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52 Cards in this Set
- Front
- Back
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Systole
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aka: afterload; Contraction of the heart; Amt of resistance to open the valve; ejection fraction
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Diastole
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aka: preload; Relaxation of the heart; Amt of stretch; Ventricles are filling; Myocardium is perfusing
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What happens to the myocardium perfusion if HR increases?
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The perfusion will decrease. There is less amount of time for ventricles to fill. Will lead to decreased O2 & chest discomfort
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3 major arteries that supply the myocardium
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L anterior descending; circumflex; R coronary artery
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Ejection fraction
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% of volume ejected with each stroke; normal is 60-80%; determined via echo or cath
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At what percent is the EF indicative of heart failure?
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<40%; damage to myocardium due to pump not efective
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Importance of L main artery
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Bifurcates to L anterior descending & circumflex. If blockage here, neither LAD or circ will be perfused
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if S3 heart sound is heard...
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an incompetent ventricle
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if S4 heart sound is heard...
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from atrium
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In a cardiac cell, what two electrolytes primarily supply the electrical charges?
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Sodium (Na+) which is normally on outside of cell and potassium(K+) which is normally inside cell
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Electrical cardiac cells
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Initiate and conduct impulses
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Mechanical cardiac cells
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contract in response to stimulation
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electrical must _________ mechanical
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precede
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polarization
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the ready state; cells are balanced; no electrical activity
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depolarization
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the discharge state; causes the contraction; the 2 chemical charges trade places causing the wave of electrical flow through the heart
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repolarization
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follows depolarization; when the cell charges are returning to their original state; the recovery state
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Route of the electrical conduction pathway
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SA node --> AV node --> Bundle of His --> R & L Bundle branches --> Purkinje fibers
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SA node
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Pacemaker of the heart (in normal conduction, w/o block); inherent rate 60-100bpm; causes atrium to contract
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AV node
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will take over as pacemaker if SA blocked; Acts as a gatekeeper; briefly delays impulses (to prevent ventricles from filling up); inherent rate 40 - 60bpm
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Bundle of His
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Conducts impulses from AV node to R & L bundle branches to Perkinje fibers; causes ventricles to contract; inherent rate 20-40bpm
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Artificial means of electrical function?
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Pacemaker
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Artificial means of pump?
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Ventricle assist device
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P wave
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The first positive deflection; Firing of the SA node; Atria are depolarizing (contracting); measures .06-.12
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PR interval
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Interval of atrial depolarization and AV delay (how long it takes for impulse to travel from SA to ventricles) measured from beginning of P to beginning of Q .12-.20
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QRS wave
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Ventricular depolarization (contraction); Measured from beginning of Q to end of S .04- <.12
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QT interval
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Length of time from ventricular depolarization to repolarization; measured from beginning of Q to end of T .35-.45
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How does HR affect QT interval?
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Faster HR will shorten relaxation and QT interval will be <.35
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T wave
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Repolarization (relaxation) of ventricles; heart is getting ready for next beat; Usually upright
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Sinus Rhythm
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60-100bpm; P wave for every QRS (.04-<.12); consistent shape; upright; PRI .12-.20; QT int .35-.45
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What factors may lead to ST depression
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ischemia in myocardium
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What factors may alter QT interval
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Heart rate or medications
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Sinus bradycardia
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Sinus rhythm rate < 60bpm; everything else WNL
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Causes of sinus bradycardia
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Vagal stimulation; hypothyroidism; electrolyte imbalance; inferior MI; Meds
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What types of meds may lead to bradycardia
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Digoxin (slows conduction @ AV node); Ca Channel Blockers; beta blockers
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Significance of bradycardia
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Decreased cardiac output, hypotension, pale, cool, clammy, dizzy, light-headed
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When & how to treat bradycardia
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Only treat if symptomatic! 1. Atropine 0.5-1.0mg IVP 2. prepare for transcutaneous pacer 3. Dopamine 5-20mcg 4. Epinephrine 2-10mcg/min 5. Isoproterenol 2-10mcg
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Sinus Tachycardia
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Sinus rhythm with rate >100bpm
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Causes of tachycardia
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Stress, exercise, anterior MI, pulm embolism, meds, hyperthyroidism, CHF, fever, caffeine, pain, shock
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Significance of sinus tachycardia
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Increased HR leads to increase in myocardial oxygen demand
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Treatment for tachycardia
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1.Treat underlying cause 2.beta blockers 3.digoxin 4.Ca channel blockers
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What calcium channel blockers may be used for tx of tachycardia
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Cardizem; Adenosine, only pushed by critical care nurse w/dr @ bedside then followed by a bolus: 6mg, 12mg, 12mg
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Atrial fibrillation
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Multiple ectopic atrial foci (firing from many areas, not just SA node); Uncoordinated atrial contractions; irregular ventricular rate; "party in the atrium"
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Causes of A-fib
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HF, cardiomyopathy, alcohol, CAD, valve disease, congenital heart, HTN, hyperthyroidism, lung disease, heart surgery, PE
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A-fib on ECG strip
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No discernable P wave, no PRI, QRS is normal, may or may not have T wave, fibrillatory waves between the QRS's
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A-fib with RVR
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Pt in a-fib with a rate >100
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Significance of a-fib
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Decrease in cardiac output due to loss of "atrial kick"; risk of thrombus formation due to incomplete emptying of the atrium
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S&S of a-fib
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chest pain, SOB, dizziness
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Treatment for a-fib
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beta blockers, Ca channel blocker, cordarone, digoxin, heparin/coumadin protocol, possible cardioversion
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What needs to be done prior to cardioversion
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An echo needs to be performed to r/o clotting in the atrium, Do not want to cardiovert & dislodge clot if one is present
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What lab test is performed for a pt on heparin
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Every 6 hrs draw a PTT & adjust heparin accordingly;
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Pt education for coumadin
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Once INR is 2-3, d/c the heparin; need monthly INR; monitor for S&S of bleeding
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Atrial flutter
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Appears as saw tooth shaped waves between regular QRS complexes; atrial rate >250
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