Evaluation of Cardiac Beta 1-adrenergic Sensitivity with Dobutamine in Healthy Volunteers

1. Evaluation of cardiac beta 1-adrenergic sensitivity in heart failure should provide instructive therapeutic as well as prognostic information. We set up a non-invasive test in healthy volunteers to evaluate beta 1-adrenergic reactivity using dobutamine as a preferential agonist. 2. The range of i.v. bolus doses was 3.2 to 12.2 micrograms kg-1. The test was well tolerated. The parameters that were most sensitive and best correlated to dobutamine doses were systolic blood pressure and the rate-corrected electromechanical systole (QS2i). The reproducibility of the test over 48 h and over 1 month was satisfactory for most parameters, with a mean variation coefficient ranging from 9 to 26%, and was better for QS2i than for heart rate. 3. Slope of log dose-response for heart rate and QS2i was similar with dobutamine and with isoprenaline, corresponding to stimulation of the same type of beta-adrenergic receptors (beta 1-subtype). This result was obtained despite a higher vagal stimulation with dobutamine. We conclude that the left ventricular contractile response assessed by QS2i provided the best parameter for evaluation of beta 1-adrenergic cardiac effects either with dobutamine or with isoprenaline. 4. In heart failure patients such a dobutamine test should allow separation of altered contractility and beta-adrenergic desensitization, since alteration of inotropic response to dobutamine should depend on both altered contractile function and adrenergic desensitization but heart rate response should only depend on the latter phenomenon.