Cardiac mechanics during development of heart failure. SOLVD Investigators.
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BACKGROUND: The changes in myocardial performance responsible for the progression from a stage of asymptomatic left ventricular dysfunction toward overt congestive heart failure are still poorly understood. Accordingly, using invasive methods, we examined the differences in baseline left ventricular function between a subgroup of patients enrolled in the treatment arm (presence of congestive heart failure) and in the prevention arm (asymptomatic patients) of the Studies of Left Ventricular Dysfunction. METHODS AND RESULTS: High-fidelity left ventricular pressures and frame-by-frame angiographic volumes were simultaneously obtained under baseline conditions in 65 patients with left ventricular ejection fraction < or = 35%. Sixteen patients had New York Heart Association congestive heart failure (class II or III), whereas the remaining 49 patients had no clinical signs of heart failure and did not receive therapy for this syndrome. A second set of data was obtained an average of 12.4 months later in 42 patients. The group with heart failure had significantly greater end-diastolic and end-systolic volumes than the asymptomatic group (both p < 0.001), but the stroke index at rest was similar in both groups. Accordingly, ejection fraction was significantly lower in the heart failure group (19.6 +/- 7.0% versus 26.3 +/- 7.2%; p < 0.02). Left ventricular end-diastolic pressure was greater and peak +dP/dt was lower in heart failure patients, but the difference did not reach statistical significance after Bonferroni correction for multiple comparisons. Moreover, the individual end-systolic stress/end-systolic volume data of the heart failure patients fell within the 95% confidence interval of the relation observed in the patients without heart failure both at baseline and after 1 year of follow-up irrespective of their changes in functional status. It was also noted that during follow-up, the changes in end-diastolic and end-systolic volumes correlated linearly, as if both dimensions always shifted in parallel, whereas alterations in contractility primarily influence end-systolic volume. CONCLUSIONS: These observations are compatible with the hypothesis that a depression in the mechanical performance of the viable myocardial areas is not the major determinant for the progression from asymptomatic to symptomatic left ventricular dysfunction. Abnormalities in left ventricular diastolic distensibility, on the other hand, might underlie the progressive ventricular dilation and create a vicious cycle through the afterload mismatch.
