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HEART FAILURE

Heart Failure is the inability of the heart to perform its task of moving blood from veins to arteries. As a consequence, arterial blood pressure decreases which causes blood to back up in veins increasing venous pressure. Finally, an insufficient difference in pressure between the arteries and veins exists, and together they cannot produce sufficient cardiac output. In congestive heart failure, the lack of sufficient renal blood flow activates the renin-angiotensin-aldosterone-antidiuretic hormone system, causing the retention of salt and water. The increased plasma volume, while initially improving cardiac function via the "Frank-Starling Mechanism", leads to at least one enlarged ventricle, a volume overload on the affected ventricle and, eventually, to decompensation and an even weaker heart. Increased sympathetic input also initially improves cardiac function, but uses an awful lot of valuable heart "energy" and also leads to decompensation. CAUSES OF HEART FAILURE Causes of right and left heart failure have basic similarities, but different disease states tend to produce one or the other. THE CAUSES OF LEFT HEART FAILURE   Ischemic Heart Disease Too great of a pressure load because of either hypertension, or aortic stenosis Too great of a volume load, because of insufficiency of either the mitral or aortic valve, thyrotoxicosis, anemia, or fistula, or disease of the heart muscle itself, such as myocarditis, cardiomyopathy, or amyloidosis THE CAUSES OF RIGHT HEART FAILURE   Left Heart Failure causes too great of a pressure load and leads to Right Heart Failure Chronic Pulmonary Disease (vasoconstriction of the pulmonary vessels with hypoxia) Right heart failure caused by pulmonary disease is called cor pulmonale Pulmonary Artery Stenosis Primary Pulmonary Hypertension Pulmonary Embolism Too great of a volume load in fluid overload Congenital Heart Disease (ventricular septal defect, patent ductus arteriosus) CONSEQUENCES OF HEART FAILURE As a result of the inability of the heart to pump blood from veins to arteries adequately, arterial pressure falls and venous pressure rises. The lack of a difference in pressure causes cardiac output to fall. The diminished forward movement of blood into arteries is called "forward failure." The backup of blood into the veins is called "backward failure." Low Output Failure is the lack of sufficient cardiac output secondary to a pressure load (e.g. stenotic aortic valve) or ineffective myocardial contraction caused by ischemia or primary disease of the heart muscle. In contrast, High Output Failure results from the inability of the heart to keep up with a greater than normal demand on the heart to move volumes of blood (incompetent heart valves). ACUTE LEFT SIDED FAILURE Also known as cardiac arrest, this condition is caused by severe arrhythmias such as ventricular fibrillation and requires CPR or electrocardioversion. CARDIOGENIC SHOCK This acute severe decrease in left ventricular cardiac output is caused by an abrupt decrease in forward flow, resulting in reflex increase in sympathetic output with tachycardia and severe vasoconstriction. Vasoconstriction produces tissue death and the release of toxic compounds, which sets up a positive feedback cycle. Even with correction of the cause, mortality remains high. Causes include: aortic or mitral valve failure perforation of the heart massive MI Prognosis for Cardiogenic shock is very poor. Even after recovery the victim may succumb to renal failure or ARDS (adult or acute respiratory distress syndrome). ACUTE BACKWARD FAILURE ~ LEFT HEART Insufficient forward flow allows blood to back up in the pulmonary veins, increasing pulmonary venous pressure and causing fluid to leak from pulmonary capillaries into alveolar spaces. Pulmonary edema then causes dyspnea, coughing, pink frothy sputum and life-threatening hypoxia. CHRONIC BACKWARD FAILURE OF THE HEART Forward failure causes the kidneys to retain salt and water. Combined with the already increased venous volume, chronic backward failure causes pulmonary venous congestion with leakage of fluid into lungs resulting in pulmonary edema, dyspnea, orthopnea, pulmonary hypertension, which then causes right heart failure. ACUTE SEVERE DECREASE IN RIGHT VENTRICULAR CARDIAC OUTPUT Caused by pulmonary embolism or cardiac tamponade. A large thrombus from an iliac vein becomes impacted in the pulmonary circulation resulting in a lack of right sided output and therefore also left sided output and death. Smaller emboli cause lung infarction and pulmonary hypertension. CHRONIC BACKWARD FAILURE OF RIGHT VENTRICLE Accumulation of fluid occurs in the systemic circulation resulting in congestion and damage to the liver and spleen in particular and edema of the lower extremities (dependent areas of body). SYMPTOMS JUGULAR VENOUS DISTENSION The height at which the greatest pulsation of the jugular veins occurs serves as a simple index of the filling pressure of the right ventricle. Increased venous pressure indicates a failure of the right ventricle to produce a normal cardiac output at a normal filling pressure. PERIPHERAL EDEMA As a result of backward failure of the right ventricle, fluid leaks from systemic capillaries, especially in dependent areas. PULMONARY EDEMA As a result of backward failure of the left ventricle fluid leaks from the pulmonary capillaries causing dyspnea, coughing, and even gurgling sounds. STRENGHT OF PULSE SCALE 4 = bounding 3 = full, increased 2 = expected 1 = diminished, barely palpable 0 = absent CAPILLARY REFILL Capillary Refill is the amount of time required for the capillary bed to refill after it is occluded by pressure. Blanch the patient's nail bed with a sustained pressure of several seconds using your thumb and forefinger. Either a toenail or fingernail can be used. Release the pressure and observe the time required for nail to regain its full color. Normal time is almost instantly to less than 2 seconds. A refill time of greater than 2 seconds indicates pathology such as arterial occlusion, hypovolemic shock or hypothermia. QUANTIFYING EDEMA SCALE Press your index finger over thge patient's bony prominence, such as the tibia or medial malleolus, for several seconds. Any depression that does not resume its original contour almost immediately is a sign of orthostatic or pitting edema. +1: slight pitting, no visible distortion, disappears rapidly (about 2 mm depression) +2: greater depth (~4 mm), no visible distortion of extremity, disappears in 10-15 seconds +3: visible change in limb contour, definite pit (~6 mm) and persists greater than one minute +4: grossly distorted limb, very deep pit (~8 mm) lasting 2-5 minutes. BACK             HOME              NEXT