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Cardiac Function


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Cardiac Output formula
CO = HR x SV
What influences cardiac output?
Influenced by activity level, metabolic rate, physiologic and psychologic stress, age, body size, cardiac reserve
Cardiac Index
CI = CO/body surface area
Heart Sounds
S1 (lub)
Caused by Tricuspid and Mitral valve closure

Where can you best hear S1?
Apex of the heart

by the diaphragm
Heart Sounds
S2 (dub)
Caused by aortic and pulmonic valve closure

systole - onset of relaxation
Where can you best hear S2?
2nd ICS
Heart Sounds
S3 (lub-dub-AH)
ventricular gallop

due to myocardial failure and ventricular volume overload
What dx are usually associated with S3 sounds?
CHF; mitral or tricuspid regurgitation
Heart Sounds
S4 (TA-lub-dub)
atrial gallop

due to increased resistance to ventricular filling after atrial contraction
What dx are usually associated with S4 sounds?
HTN, CAD, aortic stenosis, cardiomyopathy
ventricles contract and eject blood into pulmonary and systemic circuits
ventricles relax and refill with blood
Pulse Deficit
Radial pulse rate falls behind apical rate
What does it mean if there is a pulse deficit?
Indicates weak, ineffective contractions of left ventricle (p 801)
Atrial fibrillation
rapid impulses bombard AV node resulting in irregular ventricular response
Manifestations of A-fib
decreased CO such as hypotension, shortness of breath, fatigue, and angina
Peripheral pulses are irregular and of variable strength
Increases risk for thromboemboli - incidence of stroke is high
Ventricular fibrillation
extremeley rapid chaotic ventricular depolarization causing ventricles to quiver and stop pumping - CARDIAC ARREST
Manifestations of V-fib
absence of pulse, losses of consciousness, stop breathing

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