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53 Cards in this Set
- Front
- Back
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PMI: what causes a shift in it:
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Indicates a change in the anatomical position of the heart, which may occur in a pneumothorax when the mediastinum is pushed to one side
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The hearts apex lies on the diaphragm at the level of:
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Fifth intercostals space at the midclavicular line
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How much O2 % is taken up by the myocardium?
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- About 70%
Hypoxia: dilates coronary vessels, increasing blood flow, it releases a potent coronary vasodilator, adenosine |
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At what point during the cardiac cycle does coronary perfusion occur?
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During ventricular relaxation (diastole)
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What is the main adrenergic receptor in the heart?
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Β1
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What the Frank-Starling mechanism is talking about:
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The inherent ability of the heart to increase its force of contraction as increasing amounts of blood flow into it.
The greater the preload, the greater the force of contraction |
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How ventricular filling occurs: (Preload)
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Blood leaves the atria, atrial pressure falls abruptly and is only slightly higher than ventricular pressure as blood continues to drain into the ventricles. Last 0.1 sec of ventricular filling time, the atria contract (atrial kick) and forces rest of blood to ventricals.
80% ventricular filling is passive 20% caused by atrial kick |
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What is afterload?
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Tension produced by a chamber of the heart in order to contract)
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What is stroke volume?
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The volume of blood pumped from ventricle of the heart with each beat
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What is the ejection fraction?
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Filled ventricles normally eject about 60% of their volume
Less than 50% indicates poor contractility and pump failure |
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Parasympathetic stimulation on the heart and what it is going to do?
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(Vagal) primarily affects the atria, slowing the heart rate, and to a lesser extent decreasing the force of contraction.
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Calculate the mean arterial pressure (MAP):
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Systolic pressure + 2(diastolic pressure)/3
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Calculate the pulse pressure:
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It’s the difference between systolic and diastolic
Systolic – diastolic |
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Mean blood pressure is determined by:
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Stroke volume
Arterial compliance Arterial resistance |
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The test where we look at the % of blood volume pulled through the cells mainly platelets what is it:
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Hematocrit
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What signs will a person have with cor pulmonal?
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Hepatomegaly
Pedal edema Right heart failure |
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Hyperkalemia:
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Excess of potassium ions in the extracellular fluid surrounding cardiac fibers decreases the HR and SV
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Severe hyperkalemia:
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Cause heart block, or the inability of cardiac fibers to conduct action potentials through the heart
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Hypokalemia:
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May cause heart block
Increases the diffusion gradient for K+ movement out of the cell, creating a greater intracellular electronegativity than normal (decrease HR) |
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What would cause flaccid paralysis of the heart?
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Severe hypokalemia the heart muscle may fail to depolarize
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Calcium:
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Affect membrane excitability by changing the TP rather than the RMP (decreased contractility force and decreased SV)
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Hypocalcemia:
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Extremely small amount of membrane depolarization above the resting potential opens the Na+ channels (increasing HR)
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Hypercalcemia:
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Decreases membrane excitability because it raises the TP, requiring a great amount of membrane depolarization to open the Na+ gates (cause heart to develop repetitive spastic contractions)
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What light if not present in normal numbers would cause paralysis?
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K+
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What would cause an increase in excitability to the heart muscle?
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Ca
K+ |
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How catecholamines affect the heart?
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Activate beta-receptors in the cardiac cell membrane, bringing about a series of chemical events that raise intracellular levels of cyclic adenosine monophosphate (cAMP)
Increase cardiac muscle contractility |
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Cardiac tissue properties:
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Automaticity: the ability to depolarize spontaneously
Rhythmicity: the ability to depolarize spontaneously in a repetitive manner Excitability: the inclination to depolarize spontaneously Contractility: the ability to shorten muscle fibers |
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Normal sinus rhythm is:
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60 – 100 beats/min
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What causes premature beats?
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1.Local areas of tissue hypoxia (ischemia)
2.Mechanical irritation (calcified plaque) 3.Toxic irritation (nicotine, caffeine, or other drugs) |
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Normal AV rate:
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40-60bpm
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Normal Purkinje rate is:
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15 – 40 bpm
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Normal length of the P wave:
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No more than 25mm
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Normal width of the QRS complex:
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0.08 – 0.10 sec.
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What is happening with the heart:
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P wave: atrial depolarization
QRS complex: ventricular depolarization T wave: ventricular repolarization |
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What is the normal ranges of each interval:
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PR: 0.12 – 0.20 sec
QT: < 0.40 sec |
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What is detected by an ECG:
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- Voltage changes as heart depolarizes and repolarizes
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What can an ECG measure:
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The summation of all action potentials conducted through millions of myocardial fibers during the cardiac cycle
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What are the limitations of an ECG:
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Does not measure mechanical events or contraction force
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What is the normal RR interval range?
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< 0.16 sec
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What causes bradycardia?
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Excessive vagal stimulation (vomiting, suctioning, vagovagal reflex)
Sympathetic nervous system inhibition |
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Carotid sinus syndrome:
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A condition in which the pressure receptors in the fork of the common carotid artery are overly sensitive. (many vagal nerve endings)
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Syncope
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fainting
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What causes sinus tachycardia?
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Exercise, fever, anxiety, pain, and stimulants such as: coffee, tea, alcohol, and smoking
Anything that increases sympathetic stimulation Anemia, hypoxia, hypovolemia |
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What do we use to treat bradycardia?
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Parasympathetic-blocking drugs (cholinergic blockers = atropine)
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What arrhythmia would a pacemaker be indicated for?
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Severe bradycardia
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What do we use to treat PVC’s?
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O2 therapy
Coronary vasodilators Antiarrhythmic drugs (lidocaine) |
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What causes PVC’s?
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Alcohol, caffeine, tobacco
Emotional stress Hypoxia, acidosis, hypokalemia, MI, increase myocardial irritability |
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What causes PAC’s?
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Emotional stress, alcohol, caffeine, tobacco, electrolyte imbalances, sympathetic stimulation
ischemic heart disease, insufficient coronary blood flow may increase the irritability of atrial muscle. |
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Abbreviations of arrhythmias:
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VT: ventricular tachycardia
VF: ventricular fibrillation NSR: normal sinus rhythm PAC: premature atrial contraction PJC: premature junctional contraction PVC: premature ventricular contraction PSVT: paroxysmal supraventricular tachycardia |
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First-degree AV block:
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PR interval greater than 0.2 sec.
Conduction time is slower through the AV node-bundle complex |
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Second-degree AV block: (Mobitz type I /Wenckebach block)
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PR intervals gradually lengthen uttil a QRS complex fails to appear after a P wave. ( nonconducting Pwave)
Following the nonconducted P wave, PR intervals = shorter |
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Mobitz type II block:
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Constant PR intervals, but with various conduction ratios
Only 4 QRS complexes for every 5 P waves (5:4) 1 QRS for every 2 P waves (2:1) |
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Third-degree AV block (complete heart block)
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No relationship exists between P waves and QRS complexes
Atria and ventricles are electrically isolated form one another, each establishes its own rhythm |
