It has been well documented that the arterial baroreflex is depressed in chronic
congestive heart failure. Furthermore, cardiopulmonary reflexes have also been shown to be depressed in
heart failure. Because cardiac reflexes can be mediated by both mechanical and chemical stimuli, we undertook the current study to determine whether chemically activated cardiac reflexes (Bezold-Jarisch) are abnormally depressed in dogs with chronic
heart failure at a point in time when arterial baroreflexes were clearly depressed. We studied heart rate and arterial pressure responses in 13 conscious instrumented dogs before and after chronic ventricular pacing at 250 beats/min for 4-5 wk. At the time the study was done each dog showed both hemodynamic and clinical signs of
congestive heart failure. The arterial baroreflex was evaluated by analyzing the heart rate response to acute
injections of
phenylephrine and
nitroglycerin. The Bezold-Jarisch reflex was assessed in nine dogs by determining the heart rate and blood pressure responses to intracoronary
injections of various doses of
veratridine. Arterial baroreflex responses were uniformly depressed following ventricular pacing. The
phenylephrine slope was reduced by 55.8 +/- 6.9% (P < 0.001), and the
nitroglycerin slope was reduced by 67.9 +/- 5.0% (P < 0.0001) in the
heart failure state. Significant
bradycardia and
hypotension were seen at each dose of
veratridine given (0.01, 0.1, and 0.4 microgram/kg). When compared with the prepaced control state, the magnitude of the
hypotension was no different in the
heart failure state in response to any dose of
veratridine.(ABSTRACT TRUNCATED AT 250 WORDS)