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209 Cards in this Set
- Front
- Back
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Blood pressure is a product of which two factors?
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Cardiac output & Total peripheral resistance
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Cardiac output is a product of which two factors?
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Heart rate & Stroke volume
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Which is an appropriate cardiac output at rest?
2L/min 5L/min 9L/min 12L/min |
5 L/min (~70 BPM*70 ml/beat)
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What effect do circulating catecholamines have on heart rate?
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Increases (eg: epinephrine, norepinephrine)
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Stroke volume is dependent on which two main factors?
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Contractility & Venous return
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What effect does the sympathetic nervous system have on venous tone?
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Increased venous tone with sympathetic stimulation
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What are four factors which affect peripheral resistance?
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Circulating regulators; Direct innervation; Local regulators; Blood viscosity
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How do the relative contributions to blood pressure of cardiac output and total peripheral resistance change with age?
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CO contribution decreases with age, TPR contribution increases with age
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What are the three main layers of an arterial wall?
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Intima, Media, Adventitia
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Which two cell layers compose the arterial intima?
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Endothelium; Internal elastic lamina
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What is the arterial media composed primarily of?
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Smooth muscle cells
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To which protein does calcium bind in vascular smooth muscle cells?
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Calmodulin
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The calmodulin/MLCK complex phosphorylates which protein to produce muscle contraction?
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Myosin (MLCK = Myosin light chain kinase)
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What are five mechanisms via which atherosclerosis can damage the body?
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Narrowing of vessel by fibrous plaque; Plaque ulceration or rupture; Intraplaque hemorrhage; Peripheral emboli; Weakening of vessel wall
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The equation dictating the factors influencing flow through a vessel is known as what?
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Poiseuille's law
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If you narrow an artery by a factor of 2, peripheral resistance increases by what factor?
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16 times! (r^4)
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Turbulent flow through an artery is caused by what? How can we detect this on a physical exam?
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Atherosclerotic plaque; Turbulent flow will be audible through a stethoscope as a bruit
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How do Endothelial-dependent vasodilators exert their effects on vascular smooth muscle?
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EDVDs exert their effects by acting as ligands for endothilial cells, which then release prostacyclin, nitric oxide and endothelium-derived hyperpolarizing factor (EDHF) which act directly on the smooth muscle cell to activate secondary messengers which cause relaxation
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Is cure rate higher for primary or secondary hypertension? What percentage of hypertensive patients have primary hypertension?
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Secondary. Primary is typically only managable with medications. Primary (Essential) makes up about 90% of patients
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What are some causes of secondary hypertension?
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Chronic renal disease (2-4% of all HT); Primary aldosteronism (<2-15%); Renovascular (1%); Pheochromocytoma; Coarctation of the aorta; Cushing syndrome
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What are the effects of Angiotensin II on Arterial smooth muscle? On the adrenal glands? On the kidney?
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VSM: Vasoconstriction; Adrenal gland: Causes release of aldosterone; Kidney: Increases renal tubular sodium reabsorption
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Angiotensiogen is released by which organ?
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Liver
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What are the four main classes of antihypertensive medications?
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Diuretics (Thiazides; K-sparing; Loop); Sympatholytics (Beta-blockers); Vasodilators (Ca-channel blockers); RAAS antagonists (ACEi; ARB)
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What is the most common side-effect of ACE inhibitors?
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Cough
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How many leaflets comprise the mitral valve?
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2
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How many lobes are there in the posterior leaflet of the mitral valve?
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3
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How is the mitral valve attached to the ventricular wall?
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Chordae tendineae coming off of the valve leaflets are attached to papillary muscles of the ventricle.
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What separates the aortic valve from the mitral valve?
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Aortic-mitral curtain
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The S1 heart sound is due to the closure of which valve?
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Mitral valve
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An opening snap is due to pathology of which valve?
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Mitral valve
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What is the most common cause of mitral stenosis?
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Rheumatic fever
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Group A Streptococcus is an important bacteria due to its association with which cardiac condition?
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Mitral stenosis (GAS [strep pyogenes] is the cause of rheumatic fever)
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What is the primary pathological disturbance in mitral stenosis?
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Thickening and calcification of mitral leaflets; fusion of comissure
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At which surface area does hemodynamically significant mitral stenosis occur? What is the normal mitral valve area?
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< 2 cm^2. Normal is 4-6.
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What are some symptoms of severe mitral stenosis?
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Pulmonary congestion at rest (Orthopnea/PND); Right heart failure symptoms
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How can atrial fibrillation occur as a result of mitral stenosis?
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Increased LA size causes stretching and damage to conduction fibers
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Is a loud S1 indicative of early or late mitral stenosis?
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Early
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Does the S2-Opening Snap interval increase or decrease with progression of mitral stenosis?
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The gap decreases as the disease progresses
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A 57 year-old man presents to the ER after being unable to sleep laying down. Chest XR shows left atrial enlargement with pulmonary vascular redistribution. On ausciltation, an opening snap is heard following S2. What is the most likely diagnosis?
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Mitral stenosis
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How is mild, moderate and severe mitral stenosis classified based on valve areas and mean pressure gradients?
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Mild: VA > 1.5 cm2; Grad <5 mmHg
Moderate: VA 1.0-1.5; Grad 5-10 Severe: VA <1.0; Grad >10 |
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What medical management is indicated for symptomatic mitral stenosis?
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Diuretics for vascular congestion; Heart rate-slowing medications (digoxin, beta-blockers); Anticoagulation if Afib present
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What are three contraindications to percutaneous valvuloplasty for the repair of mitral stenosis?
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Left atrial clot; Severe calcification; Mitral regurgitation (hole in valve)
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Mitral prolapse is a common cause of what condition?
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Mitral regurgitation
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With mitral regurgitation, is pulmonary edema on CXR more indicative of an acute or chronic onset?
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Acute
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Aortic valve thickening without obstruction to outflow is termed what?
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Aortic sclerosis
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How common are bicuspid aortic valves? Are they more common in males or females?
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2%; 3:1 male:female distribution
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Over the age of 65, what is the most common aetiology of aortic stenosis?
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Degenerative aortic stenosis. (Bicuspid AV is more common for those < 65)
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What are the three cardinal symptoms of aortic stenosis?
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Dyspnea on exertion; Dizziness/syncope; Angina
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How does decreased exercise tolerance occur as a result of aortic stenosis?
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Inability of the LV to increase cardiac output required with exercise due to the fixed obstruction
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Decreased volume and slow upstroke central pulses are common in which valve disease?
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Aortic stenosis (Decreased cardiac output, Longer for LV to overcome obstruction)
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A single S2 may be indicative of what valve disease? What extra heart sound can be found in this condition?
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Aortic stenosis (Aortic closure is delayed). An S4 can occasionally be heard in AS due to increased contraction of the left atrium.
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What is the murmur associated with aortic stenosis?
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Systolic ejection murmur. Intensity and time to peak correlates with severity.
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What is the most helpful diagnostic tool for aortic stenosis?
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Echocardiogram
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What is considered a normal aortic valve area?
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3-4 cm^2
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What is the primary treatment for aortic stenosis?
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Valve replacement is the only option (Either open heart or percutaneous)
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What are the two most common causes of leaflet closure failure in aortic regurgitation?
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Abnormal aortic valve structure; Dilation of proximal aorta and/or dilation of AV annulus
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What will untreated acute severe aortic regurgitation lead to?
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Rapid heart failure; Cardiogenic shock
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What are 3 causes of acute severe aortic regurgitation?
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Endocarditis; Aortic dissection; Trauma
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How does the heart compensate for chronic aortic regurgitation
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Left ventricular hypertrophy to maintain intracardiac pressure
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A high systolic blood pressure with a low diastolic blood pressure (i.e. 160/40) may result from which valvular disease?
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Chronic aortic regurgitation (Due to increased cardiac output and high systolic pressure, combined with decreased diastolic pressure)
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In aortic regurgitation, does the length or the intensity of the diastolic murmur correlate with severity?
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The length of the murmur is correlated with severity of AR, but the intensity is not.
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deMusset's sign, Mueller's sign, Becker's sign and Lighthouse sign are all associated with which valvular disease?
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Aortic regurgitation
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How many layers comprise the pericardium? What are they named?
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2: Visceral pericardium & Parietal pericardium
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What separates the layers of the pericardium?
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A thin film of fluid (50 mL)
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What is the most common cause of acute pericarditis?
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Viral infection
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What are the 3 components to the pathogenesis of pericarditis?
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Local vasodilation with transudation of fluid into the pericardial space; Increased vascular permeability; Leukocyte exudation
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A man presents to the ER with chest pain radiating towards the back. ECG shows diffuse ST elevation and PR depression. CXR is normal, but Echo shows some fluid buildup around the heart. What is the most likely diagnosis?
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Pericarditis - the pain associated with pericarditis is often sharp and radiates around the heart to the back.
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How does the ST elevation of an MI differ from that of pericarditis?
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ST elevation in MI is typically localized to one region of the heart - some reciprocal leads will actually show ST inversion. However, in pericarditis the disturbance is generalized around the heart, and thus all leads (aside from aVR) show ST elevation.
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What is the first-line treatment for viral pericarditis?
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Rest and anti-inflammatory drugs (not steroids)
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What are the three factors which determine whether a pericardial effusion remains silent?
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Volume of fluid; Rate of accumulation; Compliance of pericardium
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Are heart sounds in pericardial effusion amplified, normal, or soft?
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Soft, due to excess fluid accumulation
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The ECG phenomenon where QRS complexes appear at different heights seemingly at random, due to excess movement of the heart (as seen in pericardial effusion) is known as what?
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Electrical alternans
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How does cardiac tamponade cause signs of right-sided heart failure?
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Increased pressure in pericardium compresses the heart, leading to a rise in systemic and pulmonary venous pressures, causing elevated JVP, dyspnea and pulmonary congestion.
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What is the diagnostic criterion for pulsus paradoxus?
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Decrease of systolic blood pressure more than 10 mmHg during normal inspiration
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How does pulsus paradoxus occur?
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On inspiration, intrathoracic pressure becomes negative, pulling blood from the vena cava into the right side of the heart. The excess blood pushes the interventricular septum towards the left, reducing the size of the LV and thus the strength of contraction. As a result, systolic blood pressure is reduced on inspiration.
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What is the main pathology behind constrictive pericarditis?
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Associated with pericardial disease, the pericardium becomes thickened, stiff and calcified. The end result is that the pericardium is stuck to the heart.
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Kussmaul's sign (Rise in JVP upon inspiration) is often seen in which cardiac condition?
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Constrictive pericarditis
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The stretch on the ventricular fibers just before contraction is known as what? How is this estimated?
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Preload. Estimated by EDV or ED-Pressure
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The resistance that must be overcome for the ventricle to eject its contents is known as what? How is this estimated?
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Afterload. Estimated by systolic ventricular pressure
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How is ejection fraction calculated?
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Stroke volume/End diastolic volume
(Stroke volume = EDV - ESV) |
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Is a reduced ejection fraction associated with systolic or diastolic dysfunction?
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Systolic dysfunction (Which can result from impaired contractility or increased afterload)
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Will stiffening of the heart cause systolic or diastolic dysfunction?
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Diastolic dysfunction (Systolic dysfunction results from decreased ejection fraction)
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What three neurohormonal systems will be activated in response to decreased cardiac output?
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Sympathetic nervous system; Renin-angiotensin system; ADH release
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What substances are released in elevated levels from the atrium and ventricle in heart failure? Why does this cause problems?
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Atrial natriuretic peptide; Brain natriuretic peptide. High levels of ANP/BNP desensitize their receptors and shift the balance in favour of decreased sodium and water excretion, and thus volume overload occurs.
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What do positive ionotropes do that negative ionotropes do not?
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Increase cardiac contractility
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What three factors is stroke volume dependent upon?
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Preload; Afterload; Contractility
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What is considered a normal ejection fraction?
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55-70%
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What is the main difference in diagnosis between cardiomyopathy and heart failure?
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Cardiomyopathy is a diagnosis based on a test; Heart failure is a clinical diagnosis.
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What is the most useful test in diagnosing the type and severity of a cardiomyopathy?
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Echocardiography
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What are the five classifications of cardiomyopathies?
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Dilated; Hypertrophic; Restrictive; Arrhythmogenic RV dysplasia; Unclassified
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Which cardiomyopathy is associated with decreased systolic function, atrial/ventricular arrhythmias, and has an incidence of about 7/100,000?
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Dilated cardiomyopathy
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What is by far the most common etiology of dilated cardiomyopathy?
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Idiopathic!
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Approximately what percentage of patients with dilated cardiomyopathy will stabilize?
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20-50% (About 1/3)
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What are the two mainline medical treatments for reducing mortality in dilated cardiomyopathy?
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ACE inhibitors; Beta blockers (Diuretics are used to relieve symptoms)
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What is the most common genetic cardiac disorder?
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Hypertrophic cardiomyopathy
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What is the most common variant of hypertrophic cardiomyopathy?
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Asymmetric septal without obstruction
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A Bisferens pulse (spike and dome) is characteristic of what cardiomyopathy?
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Hypertrophic cardiomyopathy
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How does an alcohol septal ablation remove a left ventricular outflow obstruction in hypertrophic cardiomyopathy?
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Alcohol is injected into one of the coronary arteries to cause a mini-MI, and cause atrophy of the muscle to remove the blockage
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What are some risk factors for sudden cardiac death?
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Family history; Gene mutations; Aborted SCD; Syncope; Abnormal BP response to exercise; Non-sustained VT; LV septal thickness > 30mm
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How is restrictive cardiomyopathy characterized?
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Non-dilated ventricles with severe impairment of LV filling
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In restrictive cardiomyopathy, is diastolic or systolic function more affected?
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Diastolic function is impaired, systolic function is typically normal
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What are the two classifications of restrictive cardiomyopathy?
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Myocardial & Endomyocardial
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What is the only major cardiovascular disorder that is increasing in incidence and prevalence?
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Congestive Heart Failure
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What percentage of deaths in Canada are attributable to congestive heart failure? A) 0.1% B) 2% C) 5% D) 9%)
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D) 9%
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Approximately 1/2 of hospital readmissions for CHF are due to what?
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Non-compliance (Diet and Rx)
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What is the largest toxin contributor to heart failure?
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Alcohol
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What are four ways to classify heart failure?
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Systolic/Diastolic; High output/Low output; Left-sided/Right-sided; Acute/Chronic
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What is the difference between PND and Orthopnea?
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Orthopnea: Inability to lie flat; PND: Volume redistribution causes someone to wake up at night
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Which extra heart sound is most likely found in heart failure?
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S3
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What chemical assay can be used to differentiate heart failure from pulmonary embolism?
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BNP. Though elevated in both conditions, it can be up to 800 pg/mL in CHF, and only 200 pg/mL in pulmonary embolism
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What non-pharmalogical management should be recommended to patients with heart failure?
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Exercise & Activity (if tolerated); Salt restriction if advanced HF; Fluid restriction if congestion present
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Which type of medication is known to increase quality of life in heart failure?
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Beta blocker
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Which type of diuretic has been shown to increase survival in heart failure?
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Potassium-sparing diuretic
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What are some contraindications to ACE inhibitors?
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Intolerance (Angioedema, renal failure); Bilateral renal artery stenosis; Pregnancy; Hyperkalemia; Severe hypotension
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What are the three main beta blockers in use for heart failure?
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Carvedilol; Bisoprolol; Metoprolol
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What are some contraindications to beta-blockers?
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Bronchospastic disease (asthma); Advanced heart block; Symptomatic bradycardia
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When are nitrates and hydralazine indicated in heart failure?
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If ACEi and ARBs are not tolerated
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According to the New York Heart Association, who should be considered for an implantable cardioverter-defibrillator?
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Patients with NYHA Class II and III heart failure, with an ejection fraction < 35%
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What is the primary indication for heart transplant in CHF?
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Severe heart disease despite adequate medical therapy
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What is the term for the heart being unable to maintain adequate tissue perfusion?
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Cardiogenic shock
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How does an increase in SNS activity lead to increased preload?
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Noradrenaline works on the Beta 1 receptors in the kidney, stimulating renin release, which converts AI to AII, which then stimulates aldosterone production, leading to sodium and water retention and thus increased preload
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What are the three primary strategies for treating heart failure?
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Unload the heart; Increase the strength of contraction; Block the effects of the SNS
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What is the most powerful class of diuretics?
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Loop diuretics
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Hypokalemia is associated with which class(es) of diuretics?
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Loop diuretics; Thiazide diuretics
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Why is overly vigorous diuresis a problem with heart failure?
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Decreased cardiac output occurs due to the Frank-Starling mechanism
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What is the main cardiac problem with potassium imbalances?
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Arrhythmias
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Which class of diuretics is more commonly associated with hypomagnesemia?
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Loop diuretics
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What is the primary mechanism of action of nitroglycerin in heart failure?
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It is converted to nitric oxide inside smooth muscle cells, which promotes the conversion of GTP to cGMP, promoting dephosphorylation of myosin light chains, and therefore relaxation of the cell.
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What is the mechanism of interaction between Nitroglycerin and Viagra?
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Nitroglycerin is converted into NO which stimulates the conversion of GTP to cGMP. cGMP relaxes the cell, and is degraded by PDE5 into GMP. Viagra inhibits the degradation, and Nitro has a more profound effect, causing hypotension
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What endogenous substance does Nesiritide mimic?
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Brain naturietic peptide (Human B-type naturietic peptide)
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What are the three primary benefits of Nesiritide in heart failure?
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Vasodilation; Naturiesis; Diuresis
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Do nitro-based vasodilators exert their effects on arteries or veins?
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Veins (Decrease venous return & LV preload)
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Dobutamine, Dopamine and Milrinone all fall into which class of medications?
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Positive Inotropes
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What receptor does dobutamine exert its effects on in the heart?
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Beta-1 receptor (agonist)
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At low doses, what receptor does dopamine bind to? What does it bind to at medium and high doses?
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Low: D1 receptors (in renal vasculature); Medium: beta-1 receptor agonist; High: alpha-1 receptor agonist (vasoconstriction, undesirable effect of increasing afterload)
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What is the target site of digoxin? How does it exert its effects?
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Digoxin blocks Na/K ATPase on cardiac muscle. Increased intracellular sodium causes increased calcium influx (Na/Ca transporter), and thus contraction is increased
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What advantage does Carvedilol have over Metoprolol in heart failure?
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While both useful, carvedilol also blocks alpha-1 receptors, promoting vasodilation and reducing afterload
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Why do septal defects typically favour left to right shunting?
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The right heart is normally at a lower pressure than the left heart
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What direction of shunting keeps you pink? What direction makes you blue/cyanotic?
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Pink: Left to right; Blue: Right to left?
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What are the differences in aetiology between central and peripheral cyanosis?
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Central: Cardiac or pulmonary cause; Peripheral: Everything else (cold, etc.)
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What are the three main types of VSDs?
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Perimembranous; Muscular; Inlet
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What type of VSD involves the aortic valve? Which involves the tricuspid valve?
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Aortic: Perimembranous VSD: Tricuspid: Inlet VSD
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In utero, how does blood from the placenta bypass the lungs to enter systemic circulation? (2 right-to-left shunts)
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Ductus arteriosus & Foramen ovale
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What three cardiac changes occur quickly after birth?
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Pulmonary vascular resistance falls; Foramen ovale closes; Ductus arteriosus closes
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In VSDs, what does left-to-right shunting get worse during the first few weeks of life?
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Pulmonary vascular resistance drops immediately after birth, but still takes 7 weeks to decrease to adult levels, causing progression of symptoms
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Hepatomegaly is often seen in kids with what cardiac condtion?
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Congestive heart failure
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What symptom of CHF, while often present in adults, is only present in kids if the condition is severely decompensated with multisystem dysfunction?
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Edema
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Why do babies sweat in response to decreased cardiac output?
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Increased sympathetic activity causes both tachycardia and diaphoresis
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What is the most common reason heart failure occurs in infants with a VSD, which is different from adults?
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In kids, it is most commonly excessive pulmonary blood flow rather than decreased cardiac function that causes heart failure
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Aside from medications, what is an important management goal in babies with congestive heart failure?
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Nutritional support (Tachypnea causes major calorie loss; babies with CHF sometimes lose the ability to suck, and may require tube feeding)
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Congestive heart failure presenting in the first week of life is most likely due to what?
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Ductus arteriosus closure
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What medication is used to maintain a patent ductus arteriosus?
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Prostaglandin (E2)
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An infant presenting with weak femoral pulses but with normal brachial pulses may have what condition?
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Coarctation of the aorta
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What is the key element of an AVSD?
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Common atrioventricular valve with 5 leaflets
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What are the four components of the tetralogy of Fallot?
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Anterior-malalignment VSD; Overriding aorta; Subpulmonary stenosis; Right ventricular hypertrophy
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What is the pathophysiology behind the tetralogy of Fallot?
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Increased resistance to flow through the pulmonary circuit combined with a VSD causes right-to-left shunting and RVH
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What causes a tetralogy spell?
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Acute decrease in pulmonary blood flow (Decrease in systemic vascular resistance or an increase in pulmonary vascular resistance)
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What is the primary use of beta blockers in tetralogy spells?
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They relax subpulmonary muscles to prevents spasm and decrease pulmonary resistance
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When is the knee-to-chest position useful in a child?
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During a tetralogy spell, it can be used to increase systemic vascular resistance
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What is the primary initial treatment in a newborn for severe cyanosis due to tetralogy of Fallot?
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Prostaglandin (Beta blockers if moderate cyanosis)
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When is surgical repair of tetralogy of Fallot typically conducted?
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4-6 months
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A newborn baby presents with O2 saturation of 70%, coupled with evident cyanosis. S1 is normal but there is no splitting of S2. Pulses are normal and there is no hepatomegaly. What is the most likely cause?
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Transposition of the great arteries. S2 is not split as the pulmonary valve is too far posterior to be auscultated.
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What side effect of Prostaglandin necessitates cardio-respiratory monitoring?
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Apnea
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How does the arterial switch operation work in TGA?
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The aorta and pulmonary arteries are severed above the valve and swapped. Coronary arteries from the aorta must also be swapped.
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What is the most common atrial septal defect?
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Oval fossa defect (Secundum atrial septal defect)
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How do ASDs typically present?
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Asymptomatic murmur in a 3-5 year-old
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A 4-year old presents with a precordial bulge, a widely-split fixed S2, and a systolic ejection murmur. What is the most likely diagnosis?
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Atrial septal defect
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What are some long-term effects of unrepaired ASDs?
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Pulmonary hypertension (major); Right heart enlargement; Rhythm disturbances; Stroke
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Irreversible pulmonary hypertension secondary to a left-to-right shunt is termed what?
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Eisenmenger's syndrome
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Which chromosomal abnormality is commonly associated with AVSDs?
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Down Syndrome
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What is the most common acquired cardiac disease in children?
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Kawasaki disease
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What are the two most problematic complications with Kawasaki disease?
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Peri/myocarditis; Coronary artery aneurysm
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An 11 year-old boy presents with a 6-day history of non-exudative conjunctivitis, and an extremely red tongue. He has a perineal rash which has spread to the trunk. What is the most likely cardiac cause?
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Kawasaki disease
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Is supraventricular tachycardia typically a narrow- or wide-complex rhythm?
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Usually a narrow-complex rhythm (normal QRS)
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Problems with dual AV node physiology can lead to which arrhythmia?
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Supraventricular tachycardia. Two signals are entering the AV node
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How should an unstable patient in supraventricular tachycardia be managed?
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Synchronized DC cardioversion
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How do warning signs differ between vasovagal and arrhythmic syncope?
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Vasovagal: "gray-out", tunnel vision, sweating etcl. Arrhythmic: No warning signs
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Syncope during exercise coupled with an ECG showing t-wave inversion may be indicative of what cardiac cause?
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Hypertrophic cardiomyopathy
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What two components must be present to confirm syncope?
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Transient loss of consciousness coupled with loss of postural tone
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What are the two pathophysiological components typically seen together in neurocardiogenic syncope?
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Vasodepression (Drop in BP); Cardioinhibition (Reduction in HR)
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Where are the sensory receptors of the orthostatic neural reflex located?
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Aortic arch & Carotid sinuses
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When is tilt-table testing warranted in cases of vaso-vagal syncope?
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Unexplained syncope in high-risk occupations
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Is there a role in using pacemakers in patients with vasovagal syncope?
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Not typically, unless there is severe syncope with prolonged pauses documented with ongoing symptoms despite conservative measures. Even then it doesn't usually make a difference
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What is the best long-term prevention strategy for people at high risk of sudden cardiac death?
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Implantable cardioverter-defibrillator (ICD)
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How long must you wait after an MI before putting in an ICD? How long after a CABG?
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MI: 1 month; CABG: 3 months
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What are the three most important red flags when assessing syncope?
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Rule out structural heart disease; FHx of sudden death; ECG abnormalities
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What is the most well-described genetic cardiac channelopathy?
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Long QT syndrome
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What is the most common inheritance pattern for cardiac genetic disorders?
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Autosomal dominant
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Brugada syndrome is a loss of function in a channel for which ion?
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Sodium (The same channel that may have gain of function in long QT)
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Fast initial sodium influx is the main driving force behind action potentials in which three cardiac components?
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Atrial muscle; Ventricular muscle; His/Purkinje bundle
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What ion does the upstroke for the AV and SA node action potential use?
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Calcium
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Efflux of what ion is responsible for cardiac repolarization?
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Potassium
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Class I antiarrhythmics effect what ion channel? How many subtypes of class I drugs are there?
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Sodium; 3 subtypes (1A, B, C)
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Class 1A antiarrhythmic drugs causing a moderate block have what effect on action potential duration? What effect do class 1B drugs have?
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1A: Moderate block, increased APD; 1B: Mild block, decreased APD
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Metoprolol is an example of what antiarrhythmic class?
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Class II (All beta blockers are class II)
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Potassium channel blockers are what type of antiarrhythmic drug?
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Class III
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What drug class fits into class IV antiarrhythmics?
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Calcium channel blockers
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What are two pharmacological ways to reduce the frequency of cardiac action potentials?
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Decrease phase 4 slope; Increase refractory period
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What are the two pharmacological targets/techniques for preventing re-entry?
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Increase refractory period of normal heart tissue; Block sodium channels in damaged tissue to impair conduction
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Why are delayed afterdepolarizations potentially dangerous? Which ion is responsible?
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They can cause a second action potential in damaged tissue; Calcium
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Which class of antiarrhythmics can be used to prevent early afterdepolarizations?
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Class 1B (decreases action potential duration, prevents excess calcium influx)
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Lidocaine is an example of what class of antiarrhythmics?
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1B
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Why are class 1C antiarrhythmics potentially dangerous?
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They can be proarrhythmic in certain situations
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Why are class II antiarrhythmics effective in supraventricular arrhythmias?
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They slow conduction through the AV node
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Amiodarone is an example of what class of antiarrhythmics? What is its mechanism of action?
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Class III (Though it also has class I, II and IV properties); Blocks potassium channels to increase the refractory period and decrease reentry
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Class III antiarrhythmics can be proarrhythmic via what mechanism?
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By increasing the refractory period, they promote early afterdepolarizations (EADs)
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Verapamil and diltiazem are class IV antiarrhythmics. Why are certain other calcium-channel blockers, such as nifedipine, not included?
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Only non-dihydropyridine CCBs are included in this class. Dihydropyridine CCBs are only useful as vasodilators
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Where are adenosine receptors located in the heart?
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One the AV and SA nodes
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How does adenosine slow heart conduction velocity?
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Adenosine binding to the AV/SA nodes activates potassium channels to cause hyperpolarization
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