Cardiac chronotropic responsiveness to beta-adrenoceptor stimulation is not reduced in the elderly.
نویسندگان
چکیده
OBJECTIVES This study evaluated cardiac beta-adrenoceptor responsiveness in the elderly. BACKGROUND The hypothesis of reduced cardiac beta-adrenoceptor responsiveness in the elderly is based on a smaller increase in heart rate after administration of isoproterenol, a nonselective beta 1- and beta 2-adrenoceptor agonist. By means of dobutamine-stress-echocardiography we were able to retest the hypothesis more accurately because dobutamine is a relatively selective beta 1-adrenoceptor agonist with weak beta 2- and alpha-adrenoceptor stimulant activity that prevents baroreflex-mediated changes in heart rate. METHODS After administration of stepwise incremental infusions of dobutamine, we measured heart rate and blood pressure responses in 360 patients who had no beta-adrenergic blocking agent therapy and no side effects during the stress test. For each patient we calculated the dose of dobutamine required to increase heart rate by 50% of the maximal heart rate during the highest dose of dobutamine. RESULTS No relation was found between age and sensitivity to dobutamine (n = 293). Power analysis revealed that this negative finding was not the result of inadequate sample size. In contrast to the prevailing hypothesis, an increased heart rate response to dobutamine was found even in a subgroup of "healthy" elderly subjects (i.e., those without concomitant disease or acute myocardial ischemia, n = 67) that was not related to changes in blood pressure during stress. However, in subjects with acute ischemia (n = 109), smokers (n = 151) or patients with a history of a previous myocardial infarction (n = 148), dobutamine sensitivity was reduced in the elderly despite a diminished change in systolic blood pressure with advanced age during dobutamine infusion. This phenomenon could be explained by a decrease in efferent cardiac baroreflex sensitivity, as has been observed during acute myocardial ischemia. There were no age-related differences in plasma concentrations of dobutamine. CONCLUSIONS No evidence for reduced beta-adrenoceptor responsiveness to dobutamine was found in "healthy" elderly subjects.
منابع مشابه
Protective Effect of Digoxin on Impaired Chronotropic Responsiveness to Adrenergic Stimulation in Cholestatic Rats
Decreased cardiac responsiveness to adrenergic stimulation has been observed in cholestatic liver disease, but the cause remains unclear. Previous reports have suggested that nitric oxide overproduction might have a role in cholestasis-induced bradycardia via inhibition of L-type calcium channels. In the present study, the digoxin has been used to increase cardiac Ca2+ transient in male Sprague...
متن کاملتأثیر بیماریها بر پاسخدهی گیرنده های بتا - آدرنرژیک
The development of radioligand - binding studies has greatly advanced our knowledge of the molecular pharmacology of beta - adrenoceptors. Using this technique it became possible for the first time to directly determine the tissue concentration of beta - adrenoceptors, and by this, the responsiveness of tissues to beta - adrenergic stimulation. One major insight into the molecular pharmacology ...
متن کاملPropofol-induced alterations in myocardial beta-adrenoceptor binding and responsiveness.
UNLABELLED Propofol (iv) depresses cardiovascular function in both humans and animals. However, the mechanism underlying this action has not been well described. The present study was designed to test the hypothesis that this effect of propofol results in part from an antagonism of adrenergic control of the heart. Experiments examined effects of propofol on: 1) [3H]CGP12177 (a beta-adrenoceptor...
متن کاملBeta-adrenoceptor-mediated responsiveness of human internal mammary artery
The internal mammary artery (IMA) is currently the preferred conduit for myocardial revascularization. However, pre-operative vasospasm and a hypoperfusion state during maximal exercise may limit its use as a bypass graft. The mechanism of spasm has not been clearly defined. Since β-adrenoceptor activation plays a major role in vasorelaxation, the present study was carried out to investigate th...
متن کاملHemodynamic and beta-adrenergic receptor adaptations during long-term beta-adrenoceptor blockade. Studies with acebutolol, atenolol, pindolol, and propranolol in hypertensive patients.
In an attempt to further clarify the mechanism of the maintenance of the antihypertensive effect of beta-adrenoceptor antagonists, the effects of four antagonists with different ancillary properties (acebutolol, atenolol, pindolol, and propranolol) on systemic and renal hemodynamics, body fluid volumes, hormones, and lymphocyte beta-adrenoceptor density were studied in four groups of 10 hyperte...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- Journal of the American College of Cardiology
دوره 25 5 شماره
صفحات -
تاریخ انتشار 1995