[Modification of myocardial function parameters by L- and D-penbutolol--an echocardiography, placebo-controlled...

In order to study left ventricular contraction parameters of L-penbutolol and D-penbutolol (isopenbutolol) we evaluated TM-echocardiograms of 12 healthy volunteers at 30 and 60 minute intervals for 8 hours after oral administration of 40 mg L- and D-penbutolol and placebo. Three different observers determined end-systolic and end-diastolic dimensions, left ventricular shortening fraction (SF) as well as mean-, peak- and rate corrected circumferential fiber shortening (VCF) and calculated at each measuring point the difference from the control value (Delta). L-penbutolol demonstrated a typical beta-blocking effect with a significant (p less than 0.001) decrease of systolic (11.1 +/- 8.6 mm Hg) and diastolic blood pressure (6.7 +/- 4.6 mm Hg) and heart rate (10.0 +/- 7.4 bpm) as well as a significant (p less than 0.001) negative inotropic effect expressed by a decrease of SF (6.5 +/- 4.2%) and VCF-mean (0.40 +/- 0.15 circ/s), VCF-peak (1.04 +/- 0.61 circ/s) and rate corrected VCF (0.28 +/- 0.08 circ/s). However, we saw a similar but less distinct negative inotropic and chronotropic effect of D-penbutolol as compared to placebo. HR decreased by 5.3 +/- 6.2 bpm (p less than 0.001), SF decreased maximally by 5.0 +/- 3.2% (p less than 0.05), VCF-mean by 0.27 +/- 0.08 circ/s (p less than 0.001), VCF-peak by 0.71 +/- 0.31 circ/s (p less than 0.001) and rate corrected VCF by 0.22 +/- 0.04 circ/s (p less than 0.001). By means of TM echocardiography it was therefore possible to document a strong beta-blocking effect of L-penbutolol as well as a negative inotropic and negative chronotropic effect by the D-isomer of penbutolol.