Sympathetic activation in dogs with congestive heart failure caused by chronic mitral valve disease and dilated cardiomyopathy

Summary Baseline plasma norepinephrine ( ne ) and epinephrine ( epi ) concentrations were measured in dogs with naturally acquired heart failure ( hf ) caused by either degenerative mitral valve disease and mitral regurgitation ( mr ) or idiopathic dilated cardiomyopathy ( dcm ). Compared with controls (clinically normal), dogs with hf had increased plasma ne concentration, which was correlated positively with clinical severity of hf . Dogs with the most severe degree of hf (New York Heart Association functional class IV) had mean ne concentration significantly ( P < 0.05) greater than that of dogs with all other functional classes of hf . Overall, mean ne concentration in dogs with dcm was greater than that in dogs with mr . Plasma epi concentration was not different between control dogs and dogs with hf or between dogs with dcm or mr . Correlations were not found between the echocardiographically derived end systolic volume index (used as an estimate of myocardial function) and plasma ne and epi concentrations or serum sodium or potassium concentration. Dogs with dcm , as a group, had a small but Significant ( P < 0.05) decrease in serum sodium concentration, compared with dogs with mr . This difference was maintained only for class-IV hf when dogs were separated according to functional hf class. In dogs with dcm , Significant inverse correlation was found between plasma ne and serum sodium concentrations. When grouped together, all dogs with hf maintained this relationship; however, dogs with mr did not have correlation between plasma ne and serum sodium concentrations. Plasma epi and serum sodium concentrations were not correlated for any group. It was concluded that in dogs, plasma ne , but not epi , concentration is high in relation to the clinical severity of naturally acquired hf . Although dogs with dcm overall had greater increase in plasma ne concentration than did dogs with primary mr , a direct relation was not evident between a noninvasive estimate of myocardial function and plasma ne concentration. The lower serum sodium values found in dogs with dcm , especially those with most severe clinical hf , along with the higher mean plasma ne concentration, may indicate a greater degree of decompensation and neurohumoral activation, compared with that in dogs with mr .