In 12 patients with severe
congestive heart failure due to ischaemic
heart disease (n = 6) and due to
congestive cardiomyopathy (n = 6) the haemodynamic effects of a new beta 1-agonist,
prenalterol, were studied. Left ventricular (LV) function was studied before and 20 min after infusion of 12 mg
prenalterol. Heart rate was kept constant by atrial pacing at a rate of 100 min-1 unless intrinsic heart rate exceeded it. As a sign of positive inotropic support,
prenalterol enhanced peak rate of LV pressure development (dP/dt) from 1160 +/- 100 mm Hg/s to 1590 +/- 190 mm Hg/s (p less than 0.005). In the mean LV end-diastolic and end-systolic volume determined by cineventriculography and two-dimensional echocardiography decreased. LV
stroke work index measured with both methods increased with 4 ml/m and 5 ml/m, respectively (p less than 0.02). LV ejection fraction was improved by 6% and 8% (p less than 0.005). Increase of peak fall of left ventricular pressure (dP/dt) (1050 +/- 60 mm Hg/s to 1270 +/- 100 mm Hg/s, p less than 0.005) and shortening of time
constant (T) of pressure fall from 64.5 +/- 5.0 ms to 44.5 +/- 6.0 ms (p less than 0.005) demonstrated the improved LV relaxation. Analysis of LV volume and myocardial compliance revealed decrease of left ventricular stiffness. Thus, LV filling pressure was reduced from 22.1 +/- 4 mm Hg to 14 +/- 3.5 mm Hg (p less than 0.001). Pressure volume analysis showed a significant increase of LV power and work, as well as a slight decrease of wall stress. Our study could demonstrate, even in patients with severe
heart failure, a sustained positive inotropic effect of
prenalterol leading to an improved left ventricular contractility, relaxation and compliance. LV power and work was enhanced. The increase of
oxygen demand seemed to be counterbalanced by an improved perfusion of particularly subendocardial layers indicated by an increased transmyocardial pressure gradient.