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The interaction between systolic and diastolic effects of inotropic drugs is an important subject which has not yet been fully clarified in the cardiological literature. The effects of the inotropic drugs k-strophanthidin and dobutamine on left ventricular (LV) relaxation and early filling phase were compared in patients with coronary artery disease (CAD) and preserved systolic function. Twenty-two patients were randomly divided into two groups; group I was infused with 0.0035 mg.kg-1 of k-strophanthidin for 10 min and group II with dobutamine at a rate of 10 micrograms.kg-1.min-1 for 10 min. Both groups underwent simultaneous haemodynamic and echo 2D-Doppler evaluations at controlled heart rate. K-strophanthidin improved contractility indexes (peak of LV systolic pressure P < 0.001, max dP/dt + P < 0.05 and dP/dt P < 0.01) and worsened T constant and LV lowest diastolic pressure, (LVLDP) (P < 0.001 and P < 0.05 respectively) without changing early transmitral filling parameters. Dobutamine induced a significant increase in contractility in group II but at the same time significantly improved LV relaxation variables (max dP/dt - P < 0.01 and T constant P < 0.001). In addition, dobutamine reduced LVLDP (P < 0.05) and significantly increased LV early filling parameters. These results show that an acute administration of either k-strophanthidin or dobutamine enhances contractility, whereas these drugs have the opposite effect on the early diastolic phase.

The beneficial effects of dobutamine on left ventricular systolic and diastolic phases have been described in patients with congestive heart failure. Its influence on left ventricular diastolic phase in patients with preserved systolic function, absence of dys- or akinetic areas, and left ventricular dilatation has not yet been adequately investigated. Thus a simultaneous echo-Doppler and hemodynamic study was performed in 15 patients with ischemic heart disease and preserved systolic function in order to assess the effect of dobutamine on left ventricular relaxation and filling phase. The infusion of dobutamine at a rate of 10 micrograms/kg/min induced a marked inotropic action, as shown by the significant increase in positive dP/dt (from 1392 +/- 224 to 2192 +/- 295 mmHg/sec, p < 0.001), dP/dt/P (from 32 +/- 8.1 to 50 +/- 17 sec-1; p < 0.0001), and in peak of systolic pressure (from 143 +/- 25 to 168 +/- 36 mmHg; p < 0.005). In addition, dobutamine reduced the end-systolic volume index (from 30 +/- 16 to 26 +/- 19 ml/m2; p < 0.05), the end-systolic stress (from 222.2 +/- 65.3 to 198.4 +/- 84 g/cm2; p < 0.006), and had favorable effects on relaxation and the early filling phase.(ABSTRACT TRUNCATED AT 250 WORDS)