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Immune reactivity to the enzyme glutamic acid decarboxylase (GAD), a pancreatic islet autoantigen, is present at the diagnosis of insulin-dependent diabetes mellitus (IDDM). Because GAD is also highly expressed in [...]

It has been reported that use of [Beta] blockers may not be safe after cardiac transplantation because the denervated hearts may be largely dependent on circulating catecholamines to increase cardiac Output. Therefore, the effects of intravenous propranolol were studied during maximal treadmill exercise in 7 patients with heterotopic and 6 with orthotopic cardiac transplantations. An average decrease Of about 15 % in exercise duration (P In patients with heterotopic transplantation, [Beta] blockade produced similar effects on heart rate in the denervated donor hearts and the innervated recipient hearts during and after mild exercise- During peak exercise, [Beta] blockade attenuated the rate to a greater extent in the donor hearts. Although the denervated doner heart s more sensitive to [Beta] blockade than the innervated recipient heart during exercise, no adverse effects were observed. Beta-blocker therapy should be considered for cardiac transplant patients if longer-term studies confirm their safe use in these patients. (Am J Cardiol 1989;64:636-641), Although heart tissue is able to contract spontaneously, in a normal intact heart, the rate is normally regulated by the interaction of the two opposing divisions of the autonomic nervous system. At rest the intrinsic beat of the heart occurs at a faster rate than that which is measured; this inhibition occurs through a constant repression of its rate by the parasympathetic nervous system. When a threat or other need for immediate action is perceived, the sympathetic division of the autonomic nervous system is capable of immediately increasing the heart rate. Transplantation of a heart, particularly a heterotopic or out-of-place transplant, removes the ability of the autonomic nervous system to directly affect heart rate, although it may lead to a release of epinephrine from the adrenal glands which can speed-up the heart rate. However, according to some studies patients do show changes in heart rate in response to exercise following heart transplantation. It is believed that this occurs initially because exercise increases the venous return to the heart, mechanically stretching the walls of the heart and causing mechanical stimulation. As the exercise continues, there is a release of epinephrine and similar hormones from the adrenal glands which directly affect the heart, increasing the rate. The use of beta-blocking drugs prevents this action and transplanted patients have been considered vulnerable to these drugs. This experiment studies the immediate and short-term effect of a beta blocker, propranolol, during exercise. The drug was administered intravenously during treadmill exercise to 13 patients who had received a heart transplant. The drug produced a 15 percent decrease in the patients' abilities to perform exercise, lowered the average exercise-induced blood pressure elevation by about 34 percent, and kept the average heart rate 40 percent below the level that would have been reached without the medication. Beta-blocker drugs appear to be both safe and effective in patients with transplanted hearts; however, additional research is required to confirm their safety.