Cardiac Function
Terms
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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
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Heart Sounds
S1 (lub) -
Caused by Tricuspid and Mitral valve closure
diastole - 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
- Systole
- ventricles contract and eject blood into pulmonary and systemic circuits
- Diastole
- 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