Chapter 9

Heart Failure

It has been estimated that heart failure affects more than 4 million patients in the United States and that more than 500,000 people are diagnosed with new heart failure each year.1 In the Studies of Left Ventricular Dysfunction (SOLVD)2 coronary artery disease accounted for almost 75% of the cases of chronic heart failure in white male patients, although in the Framingham heart study, coronary heart disease accounted for only 46% of cases of heart failure in men and 27% of chronic heart failure cases in women. Coronary artery disease and hypertension (either alone or in combination) were implicated as the cause in over 90% of cases of heart failure in the Framingham study (Table 9.1).

Q: What is the pathophysiology of congestive heart failure? Congestive heart failure (CHF) is a clinical syndrome of breathlessness, effort intolerance, and edema caused by a variety of cardiac abnormalities. These abnormalities include, rhythm problems (e.g., atrial fibrillation), heart valve disease, and, most commonly, left ventricular systolic dysfunction (LVSD). With the advent of new investigative procedures, it has now become easier to diagnose heart failure early, and this enables early institution of treatment. PATHOPHYSIOLOGY

Heart failure is a condition in which the heart fails to discharge its contents adequately. It is associated with abnormalities of cardiac function, skeletal muscle, and renal function; stimulation of sympathetic nervous system; and a complex pattern of neurohormonal changes. Except in cases of valvular heart failure, the primary abnormality is the impairment of left ventricular function. Reduced cardiac output causes activation of several neurohormonal compensatory mechanisms. Stimulation of sympathetic system leads to tachycardia, increased myocardial contractility, and peripheral vasoconstriction. Activation of the renin-angiotensin-aldosterone

200

CORONARY HEART DISEASE IN CLINICAL PRACTICE

TABLE 9.1. New York Heart Association (NYHA) classification of heart failure Grade

Criteria

I

Symptoms only occur on severe exertion; an almost normal lifestyle is possible Symptoms on moderate exertion; patient has to avoid certain situations (i.e., carrying shopping bags, climbing several stairs) Symptoms occur on mild exertion Symptoms occur frequently, even at rest

II

III IV

system also leads to vasoconstriction (due to angiotensin) and an increase in blood volume, with retention of salt and water (due to aldosterone). Blood concentration of vasopressin and natriuretic peptide increases. There is also increasing cardiac dilatation. There are three natriuretic peptides. Atrial natriuretic peptide (ANP) is released from the atria in response to stretch, leading to natriuresis and vasodilatation. Brain natriuretic peptide (BNP) is also released from the heart, predominantly from the ventricles. ANP and BNP have similar action. C-type natriuretic peptide is limited to the vascular endothelium and central nervous system and has only limited effects on natriuresis and vasodilatation. Myocardial Remodeling, Hibernation, and Stunning

Following heart attack, cardiac contractility is often impaired, and neurohormonal activation causes regional eccentric and concentric hypertrophy of the noninfarcted segment with expansion of the infarcted zone. This is known as remodeling. Myocardial dysfunction may also occur in response to “stunning” (postischemic dysfunction), which describes the delayed recovery of myocardial function despite the restoration of coronary artery flow, in the absence of irreversible damage. This is in contrast to “hibernating” myocardium, which describes persistent myocardial dysfunction at rest, secondary to reduced myocardial perfusion, although cardiac myocytes remain viable and myocardial contraction may improve with revascularization. Some patients may develop heart failure as a result of diastolic dysfunction.

HEART FAILURE

201

MANAGEMENT

Q: What investigations should be done in the diagnosis of heart failure? The following investigations are usually recommended: • Echocardiography is the most important technique used in the diagnosis of heart failure even in the presymptomatic stages. Two-dimensional Doppler echocardiography allows quantification of global and regional left and right ventricular systolic function. An ejection fraction of