Congestive heart failure (CHF) is associated with significant ventricular systolic dysfunction. Current medical therapy is traditionally directed toward improving contractile function or minimizing ventricular work load. However, recently it has been encountered that left ventricular (LV) diastolic dysfunction also may occur in the absence of overt systolic dysfunction^1–7) and patients with CHF and systolic impairment do not benefit significantly from inotropic agents^8,9).

The objective of the present study was to identify patients with myocardial infarction and CHF who have normal global ejection fraction (EF) and to evaluate whether pulmonary congestive symptoms may in part account for impaired diastolic performance.

The clinical syndrome of congestive heart failure (CHF) is traditionally associated with inadequate myocardial contraction, volume overload and impaired ventricular filling. Accordingly, CHF therapy has been directed toward augmentation of contractile function with positive inotropic agents or alteration in preload and afterload with vasodilators and diuretics^12,13).

Recently it has been recognized that left ventricular (LV) diastolic impairment may occur without systolic dysfunction and may develop coincident with or before abnormalities of systolic function. This has been reported in patients with coronary artery disease, pressure^2–14) and volume-overload states¹⁵⁾ and cardiomyopathy^1,16,17). Several studies^5,18–21) reported normal systolic LV function in patients with CHF. Souffer et al.²²⁾ noted intact systolic LV function in 42% of patients with clinical diagnosis of CHF referred to the nuclear cardiology laboratory during a 3 month sampling period. Echeverria et al.²³⁾, who used echocardiography noted normal systolic function in 40% of 50 consecutive patients with CHF, and Dougherty et al.²⁴⁾, who used radionuclide technique also noted a normal ejection fraction (>45%) in 36% of CHF. Warnowicz et al.²⁵⁾ reported 16 of 39 patients with acute myocardial infarction (AMI) and pulmonary edema having intact LVEF. These studies suggest that the frequency of normal systolic function in patients with CHF are more closely associated with diastolic than systolic performance. Moreover, Firth et al.⁹⁾ have failed to show digitalis-induced augmentation of LVEF and Lee et al.⁸⁾ noted that only 56% among the CHF patients improved clinically with digoxin.

Myocardial contraction and relaxation are loosely coupled processes that may be separately altered by certain stimuli²⁶⁾. Thus myocardial relaxation is not directly dependent upon contractile events and several studies^17–19) have revealed the clinical relevance of diastolic impairment by its association with CHF. Pulmonary vascular congestion in the absence of abnormal systolic performance may be due to impaired ventricular filling²¹⁾.

The mechanism for abnormal ventricular diastolic filling is not well known but it may be due to defects in calcium uptake shown in myocardial microsome and depletion of myocardial catecholamine in AMI and CHF²¹⁾. Factors that may result in abnormal diastolic function in patients with CHF include volume-overload states, systemic hypertension, valvular heart disease, pericardial restriction, restrictive cardiomyopathy and increased heart rate, which reduces ventricular filling time^5,17–20). In most of our patients with AMI and CHF, the authors could not identify such causes. Two patients in the present study had hypertension, but there was no evidence of LV hypertrophy by echocardiography.

LV performance was evaluated using radionuclide measurement. LVEF, used as useful parameter for detecting impaired myocardial function in the present study has been found of value in identifying patients with systolic dysfunction in several heart diseases. Diastolic function was assessed by 6 parameters, which obtained from time-activity curve. Although Bonow et al.^1,3) and others^2,4,17,22) have shown that peak filling rate can be used to evaluate diastolic function, the authors employed average filling velocity as measures of diastolic function. Average filling velocity are less sensitive to noise and independent of temporal resolution. Our methods for measuring average filling velocities differ slightly from those reported by Smith et al.²⁷⁾ in that only the relatively constant portions of rapid and slow filling periods were used. By not taking the minimum count point of the time-activity curve as the onset of rapid filling, our method revealed more rapid normal velocities in control group than the average rates reported by Smith et al.²⁷⁾.

In addition, average slow filling velocity and rapid filling time as well as total diastolic time were significantly different in CHF patients compared with normal control group.

Bonow et al.³⁾ reported that diastolic indices in 1, 2, 3 vessel and left main diseases altered significantly in patients with CAD and normal ejection fraction compared with normal control group. But no difference between groups according to the number of vessels involved was noted. Reduto et al.⁴⁾ noted that there was little change in EF and filling fraction at rest or during exercise between anterior and inferior MI patients. Similarly, the authors found no differences in diastolic variables between groups according to the number of vessels involved and between groups according to the localization of AMI.

In conclusion, evidence of impaired LV diastolic function without abnormal systolic function was identified in selected patients who had AMI and CHF. Radionuclide assessment of diastolic performance may be relevant for evaluation of LV performance and optimal therapy in patients with CHF.