Differential systolic and diastolic effects of β-adrenergic stimulation in patients with severe left ventricular dysfunction: A radionuclide ventriculographic study
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Background. An attenuated inotropic response to β-adrenergic stimulation has been documented in patients with severely depressed left ventricular (LV) function. Scant data exist regarding the effect of β-adrenergic stimulation on LV diastolic function in human beings. Our objective was to evaluate the effect of dobutamine infusion on LV systolic and diastolic function in patients with severe ventricular dysfunction.
Methods and Results. We studied 26 patients (60 ± 9 years) in stable condition with healed myocardial infarction and LV ejection fraction (EF) less than 35% by radionuclide ventriculography. LVEF, volumes, peak ejection rate (PER), peak filling rate (PFR), and peak systolic pressure-to-end-systolic volume ratio were calculated at the infusion rate of 5 and 10 γ · kg-1 · min-1 · At 5 γ · kg-1 · min-1, no changes were observed in heart rate (75 ± 16 beats/min vs 75 ± 15 beats/min at rest), LVEF (23% ± 8% vs 22% ± 7%), and PER (1.40 ± 0.48 end-diastolic volume per second [EDV/s] vs 1.30 ± 0.48 EDV/s); however, a significant increase in PFR was observed (1.11 ± 0.36 EDV/s vs 0.86 ± 0.30 EDV/s, P < .01). At 10 γ · kg-1 · min-1, an increase in LVEF (25% ± 10%, P < .01) and PER (1.60 ± 0.57 EDV/s, P < .01) was observed; PFR (1.25 ± 0.36 EDV/s, P < .05) also increased, whereas heart rate (78 ± 18 beats/min) was unchanged. No significant changes in LV volumes or in indices of LV contraction synchronicity were observed during infusion. Finally, the peak systolic pressure-to-end-systolic volume ratio was unchanged at 5 γ · kg-1 · min-1 and significantly increased at 10 γ · kg-1 · min-1.
Conclusions. In stable patients with ischemic heart disease and severe LV dysfunction, β-adrenergic stimulation may still induce a positive lusitropic response, despite attenuated inotropic and chronotropic responses; moreover, the effects on diastolic function occur earlier than those on systolic function. (J Nucl Cardiol 2003;10:46-50.)
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