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Effects of DBcAMP on exercise capacity in patients with and without chronic heart failure
H Nakajima1, Y Miyagi, M Fujita
12nd Department of Internal Medicine, Toyama Medical and Pharmaceutical University, Japan.
Insights
Dibutyryl cyclic AMP (DBcAMP) caused vasodilation in heart failure patients but did not improve exercise capacity or duration. This suggests nonspecific vasodilation, not vasoconstriction, limits exercise improvement in these patients.
Area of Science:
- Cardiology
- Exercise Physiology
Background:
- Congestive heart failure (CHF) often impairs exercise capacity.
- Vasodilation is a potential therapeutic strategy to improve exercise tolerance in cardiac patients.
Purpose of the Study:
- To investigate the acute effects of vasodilation using dibutyryl cyclic AMP (DBcAMP) on exercise capacity in patients with and without congestive heart failure.
- To determine if vasodilation improves exercise duration and maximal oxygen consumption in these patient groups.
Main Methods:
- A graded exercise protocol on an upright bicycle ergometer was used.
- Patients with (group 1) and without (group 2) congestive heart failure received DBcAMP.
- Hemodynamic parameters, exercise duration, and maximal oxygen consumption were measured before and after DBcAMP administration.
Main Results:
- DBcAMP increased cardiac output and decreased pulmonary capillary wedge pressure and systemic vascular resistance at rest and during maximal exercise in both groups.
- Neither exercise duration nor maximal oxygen consumption significantly improved after DBcAMP administration in either group.
- Arteriovenous oxygen differences were lower during DBcAMP treatment, indicating reduced oxygen extraction.
Conclusions:
- Acute vasodilation with DBcAMP does not enhance exercise capacity in cardiac patients, irrespective of heart failure status.
- The lack of improvement is likely due to nonspecific vasodilation and maldistribution of cardiac output, rather than persistent vasoconstriction.
- Further research is needed to identify effective vasodilation strategies for improving exercise tolerance in heart failure.
Abstract:
The acute effects of vasodilation on exercise capacity in cardiac patients with (group 1) and without (group 2) congestive heart failure were studied using dibutyryl cyclic AMP (DBcAMP). Exercise was performed on an upright bicycle ergometer using a graded protocol. DBcAMP increased cardiac output and decreased pulmonary capillary wedge pressure and systemic vascular resistance both at rest and during maximal exercise in these two groups. However, before and after DBcAMP neither exercise duration (371 +/- 52 seconds vs. 388 +/- 44, NS, in group 1, 645 +/- 148 vs. 635 +/- 143 seconds, NS, in group 2, respectively) nor maximal oxygen consumption (12.8 +/- 2.3 ml/kg/min vs. 13.1 +/- 1.6, NS, in group 1, 20.3 +/- 1.4 vs. 20.1 +/- 1.5, NS, in group 2, respectively) was improved. In both groups the arteriovenous oxygen differences were lower at rest and during exercise performed while on DBcAMP than in the control state. In group 2 patients excess vasoconstriction mediated by abnormally increased neurohormonal activities or edema were absent. Failure of the vasodilator to increase exercise capacity is probably due to nonspecific vasodilation and maldistribution of increased cardiac output, and not to tight vasoconstriction or narrowed arteriolar lumen.