Left ventricular failure

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  1. Heart failure can be categorized into three types: mechanical abnormalities (pressure or volume load), myocardial abnormalities (cardiomyopathy or ischemia) and conduction of rhythm disturbances
  2. Heart failure is generally associated with a decrease in stroke volume and an increase in end-diastolic volume resulting in a decreased ejection fraction and a high diastolic pressure in the ventricle
    1. hypoxia, ischemia, or other myocardial depressants move the Starling curve downward; NOTE: heart normally extracts about 90% of O2 supplied to it so a drop in oxygenation may hurt heart muscle significantly
    2. increases in ventricular diastolic pressure is reflected in increases in pulmonary venous and capillary pressures
  3. cardiac failure results in fewer beta-1 receptors making beta-2 receptors proportionally greater in volume, cardiac hypertrophy, and increased demand for oxygen by the myocardium
  4. once heart failure occurs with a decrease in cardiac output, peripheral resistance will increase, renin angiotensin system will be activated, atrial natriuretic factor is released, aldosterone levels increase and there is an increase in sympathetic nerve tone
  5. Symptoms: exertion dyspnea, orthopnea, nocturnal dyspnea, dry cough, fatigue, decreased tolerance to effort
  6. Treatment:
    1. acute left heart failure: inotropic agents such as dopamine, dobutamine or amrinone; anti-arrhytmic treatment
    2. chronic: ACE-inhibitors, beta-blockers, digoxin, diuretics, nitrates, aspirin
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