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Diastolic Dysfunction
By Dr. Jon P. Lindemann

Diastolic dysfunction is an abnormality of the distensibility, filling or relaxation of the left ventricle. It is characterized by abnormal left ventricular filling and elevated filling pressures. It may be present alone or in combination with LV systolic dysfunction. Epidemiologic studies have shown that left ventricular systolic function is normal in 40-60% of patients with symptoms of congestive heart failure. This condition has been termed “heart failure with normal systolic function”.

The prevalence of diastolic dysfunction among patients with congestive heart failure increases with age. For example, the estimated prevalence of diastolic dysfunction among patients with heart failure was 50 percent among patients at age greater than 70 years whereas the prevalence was less than 15 percent among patients aged less than 50 years. Moreover, among these elderly patients, an additional 15 percent of patients have low-normal systolic function (ejection fraction 45-55 percent) which would not be expected to produce symptoms. Women are more likely to have heart failure with preserved systolic function than with men. A recent study of Medicare beneficiaries with a discharge diagnosis of congestive heart failure found that 35 percent had preserved LV systolic function; among these, 79 percent were women. By contrast, among the 65 percent of patients with impaired LV systolic function, only 49 percent were women. In this study, the predominance of women with normal systolic function remained after correcting for coronary artery disease, hypertension, pulmonary disease or renal failure. In a more recent analysis of a registry of more than 100,000 patients hospitalized for decompensated congestive heart failure, clinical characteristics of the 50 percent of patients with normal systolic function were as follows: more likely to be older, female and hypertensive; less likely to have had a prior myocardial infarction; and had lower in-hospital mortality, but similar ICU and hospital length of stay.

Asymptomatic diastolic dysfunction, defined by Doppler criteria, is much more common than symptomatic diastolic dysfunction. In a recent community based study of patients over 45 years old, 28 percent of asymptomatic patients had some degree of diastolic dysfunction using echo-Doppler criteria (see below). Significantly, asymptomatic diastolic dysfunction, even mild, was associated with a marked increase in all-cause mortality.

Major causes of isolated diastolic dysfunction include systemic arterial hypertension with left ventricular hypertrophy, hypertrophic cardiomyopathy, aortic stenosis with normal LV systolic function, ischemic heart disease and restrictive cardiomyopathies. The major determinants of diastolic function are active relaxation which is an active, energy-dependant process and the elasticity or distensibility of the left ventricle which is a passive process. Hypertrophy, which is a common feature among the etiologies, affects both determinants of diastolic function, altering both passive properties by increasing wall thickness and decreasing elasticity while increasing the propensity for ischemia by increasing intercapillary diffusion distances.

The clinical manifestations of diastolic heart failure are similar to those of systolic failure. Dyspnea on exertion, decreased exercise tolerance and lower extremity edema are present in both conditions, although generally less severe with diastolic dysfunction. Factors precipitating acute exacerbations are similar with systolic and diastolic dysfunction. These typically include uncontrolled hypertension, ischemia, anemia, renal insufficiency; volume expanding drugs such as nonsteroidal anti-inflammatory drugs and thiazolidenediones as well as noncompliance and sodium indiscretion. Patients with diastolic dysfunction are particularly sensitive to increases in heart rate, which decrease the time available for left ventricular filling. This case is even worse with atrial fibrillation with the loss of atrial contraction, further reducing left ventricular filling and stroke volume.

The diagnosis of diastolic dysfunction is often made in patients with symptoms of heart failure and normal LV systolic function, usually by echocardiography. The differential diagnosis includes symptoms due to obesity, lung disease and undiagnosed coronary artery disease. There is some controversy as to whether additional testing is needed to establish the diagnosis. B-type naturetic peptide (BNP) levels are elevated in patients with symptomatic and asymptomatic LV diastolic dysfunction, but cannot discriminate between patient with systolic and diastolic dysfunction. Cardiac catheterization can detect the hemodynamic features of diastolic dysfunction. However, such measures are seldom employed because of the need for specialized equipment such as micromanometer and conductance catheters and the time required to complete the studies. Moreover, catheter-based studies have been largely replaced by noninvasive echocardiographic-Doppler methods which are quantitative, and relatively rapid.

Echocardiography is useful in detecting hypertrophy and left atrial enlargement commonly present in diastolic dysfunction while quantitating LV systolic function. Moreover, echocardiography can detect other conditions leading to symptoms of heart failure including pericardial and valvular diseases as well as the presence of regional wall motion abnormalities suggestive of myocardial infarction. Doppler methods are commonly limited to an assessment of the pattern of mitral inflow during diastole. The mitral inflow pattern may be influenced by a number of parameters including preload and heart rate. Moreover, it is of limited value in the presence of atrial fibrillation. These limitations are overcome by utilization of additional Doppler indices including pulmonary venous inflow patterns, tissue Doppler and color M-mode Doppler.

Three levels of diastolic dysfunction have been described using this approach: impaired LV relaxation, pseudonormal relaxation and restrictive filling, corresponding to mild, moderate and severe diastolic dysfunction. Progressive levels of diastolic dysfunction are associated with increased plasma concentrations of BNP and are associated with worse prognosis.

Treatment of diastolic dysfunction is largely empiric due to the absence of randomized prospective clinical trials to direct therapy. Therapy is foremost directed at controlling systolic and diastolic hypertension. Preferred agents include angiotensin converting enzyme (ACE) inhibitors or receptor blockers, beta blockers and some calcium channel antagonists. (Short-acting dihydropyridine calcium channel blockers are to be avoided because of reflex tachycardia). Control of ventricular response in atrial fibrillation, both at rest and during exercise is important when this arrhythmia is present. This is generally best achieved with diltiazem or verapamil alone or in combination with beta blockers. (Digitalis has limited utility for rate control in diastolic dysfunction.) Diuretics play an important role in controlling blood pressure as well as the symptoms of pulmonary congestion and peripheral edema. Excessive diuresis should be avoided because of the possibility of decreased cardiac filling and cardiac output due to decreased preload.

In summary, diastolic dysfunction is a common cause of congestive heart failure. It is more common in women and increases in frequency with advancing age. Although mortality is less than with heart failure due to systolic dysfunction, diastolic dysfunction remains an important cause of morbidity and mortality.