Left ventricular performance in the conscious dog with chronically denervated heart

Conscious dogs have been studied after chronic cardiac denervation and implantation of aortic flow and left ventricular pressure transducers. After cardiac denervation, sinus arrhythmia was abolished but cardiac output, stroke volume (SV), maximum acceleration of blood from the left ventricle (MA), and maximum rate of rise of left ventricular pressure (LV dp/dt max) were all within the range of values previously found in dogs with innervated hearts. An increase in end-diastolic volume produced an increase in SV but little change in MA or LV dp/dt max. The following responses were found to be similar to those found in dogs with innervated hearts: (1) postectopic potentiation, which produced no increase in SV from the same left ventricular end-diastolic pressure (LVED) while MA and LV dp/dt max were markedly increased; (2) inhalation of carbon dioxide, which produced a fall in SV, MA, and LV dp/dt max and a rise in LVED; (3) the haemodynamic effects of changing heart rate by atrial pacing and the interval strength relationships. Intracellular enzyme function, lipid, RNA/DNA, and water content were also found to be normal in chronically denervated hearts as judged by quantitative histochemical studies and interference microscopy.