VENTRICULAR UNLOADING AND IMPROVEMENT IN LEFT-VENTRICULAR FUNCTION AFTER ANGIOTENSIN-CONVERTING ENZYME-INHIBITION WITH ENALAPRIL IN PATIENTS WITH CHRONIC CONGESTIVE-HEART-FAILURE

To clarify how angiotensin converting enzyme inhibition affects left v entricular function through ventricular unloading, ventricular wall st ress, ventricular volumes, and other cardiac indices and exercise tole rance were evaluated in 17 patients with mild to moderate chronic cong estive heart failure before and after 3 months of treatment with enala pril. Echocardiographic examination revealed that treatment with this angiotensin converting enzyme inhibitor resulted in significant reduct ions in end-systolic wall stress (117+/-25 to 89+/-28 g/cm(2), p<0.01) and left ventricular volume indices (end-diastolic: 163+/-56 to 143+/ -60; end-systolic 99+/-51 to 77+/-57 ml/m(2) p<0.01). Ejection fractio n (42+/-11 to 48+/-13%, p<0.01) and systolic blood pressure/end-systol ic volume (SBP/ESV; 1.06+/-0.30 to 1.33+/-0.48 mmHg/ml, p<0.01) were b oth increased. By radionuclide ventriculography, ejection fraction and peak ejection rate (2.30+/-0.74 to 2.80+/-0.76 EDV/sec, p<0.01) were increased, while time to peak ejection, time to peak filling, and peak filling rate were unchanged. Heart rate and double product at exercis e were decreased and Delta EF was significantly increased (-1.4+/-4.1 to 1.6+/-4.4%, p<0.02). The decrease in end-systolic wall stress was c onsistently related to both the increase in ejection fraction and SBP/ ESV, while the decrease in end-diastolic volume was related only to SB P/ESV and not to ejection fraction. Furthermore, there was a direct re lationship between the decrease in systolic wall stress and the decrea se in end-diastolic volume. These results suggest that the improvement of left ventricular contractility due to angiotensin converting enzym e inhibition was produced through a parallel reduction of both afterlo ad and preload. Afterload reduction had a greater effect on the improv ement of left ventricular ejection fraction than preload reduction.