EVALUATION OF CARDIAC BETA(1)-ADRENERGIC SENSITIVITY WITH DOBUTAMINE IN HEALTHY-VOLUNTEERS

1 Evaluation of cardiac beta(1)-adrenergic sensitivity in heart failur e should provide instructive therapeutic as well as prognostic informa tion. We set up a non-invasive test in healthy volunteers to evaluate beta(1)-adrenergic reactivity using dobutamine as a preferential agoni st. 2 The range of i.v. bolus doses was 3.2 to 12.2 mu g kg(-1). The t est was well tolerated. The parameters that were most sensitive and be st correlated to dobutamine doses were systolic blood pressure and the rate-corrected electromechanical systole (QS(2i)) The reproducibility of the test over 48 h and over 1 month was satisfactory for most para meters, with a mean variation coefficient ranging from 9 to 26%, and w as better for QS(2i) than for heart rate. 3 Slope of log dose-response for heart rate and QS(2i) was similar with dobutamine and with isopre naline, corresponding to stimulation of the same type of beta-adrenerg ic receptors (beta(1)-subtype). This result was obtained despite a hig her vagal stimulation with dobutamine. We conclude that the left ventr icular contractile response assessed by QS(2i) provided the best param eter for evaluation of beta(1)-adrenergic cardiac effects either with dobutamine or with isoprenaline. 4 In heart failure patients such a do butamine test should allow separation of altered contractility and bet a-adrenergic desensitization, since alteration of inotropic response t o dobutamine should depend on both altered contractile function and ad renergic desensitization but heart rate response should only depend on the latter phenomenon.