Abstract
The present study investigated the role of cardiac nerves on homeometric autoregulation in anesthetized dogs during acute volume loading. Ventricular pressure-volume loops (conductance catheter method) were constructed during acute volume loading with intact cardiac nerves (ICN) and after cardiac decentralization (DCN; bilateral ablation of thoracic vagosympathetic complexes, stellate ganglia and anterior and posterior ansae subclavia). Arterial pressure increased as expected after volume loading but no significant changes were observed for heart rate and other hemodynamic parameters. Coronary sinus venous oxygen content was also higher regardless of nerve status in response to the overall increase in cardiac work. Pressure-volume catheter data showed markedly higher end-systolic volumes after volume loading under ICN and DCN conditions; stroke volume (mL/beat) and stroke work (mL/mm Hg) were not changed but LV ejection fraction was significantly lower. End-diastolic volume and cardiac output did not change. In addition, systemic vascular resistance and tau were higher with volume loading but no differences between ICN and DCN were observed. These findings show that acute volume loading produces an immediate influence on LV function independent of cardiac nerve status.
Highlights
The intrinsic cardiac nervous system regulates beat-to-beat coordination of regional cardiac function and inte-Homeometric autoregulation allows the left ventricular (LV) to eject the same stroke volume against a wide range of resistances without increasing end-diastolic pressure and to increase contractility by reducing the duration of systole within the total cardiac cycle [5]
The present study examined whether intact cardiac nerves contribute to homeometric autoregulation in anesthetized dogs during acute volume loading
Arterial pressure increased as expected considering the experimental model; no change was observed for coronary sinus pressures
Summary
Homeometric autoregulation allows the LV to eject the same stroke volume against a wide range of resistances without increasing end-diastolic pressure and to increase contractility by reducing the duration of systole within the total cardiac cycle [5]. In hearts with intact cardiac nerves, stroke volume and work increase in relation to diastolic pressure or volume [3]. Impaired functionality of the autonomic nervous system could have negative effects on regulation of left ventricular (LV) volume and ventricular performance [6] [7]. In heart transplant patients LV volume regulation remains impaired even after normalization of cardiac hemodynamics while in heart failure patients, increased LV volume contributes to higher mortality [8]. The present study examined whether intact cardiac nerves contribute to homeometric autoregulation in anesthetized dogs during acute volume loading. Experiments were performed in the same animal before and after acute bilateral ablation of extra-cardiac sympathetic and parasympathetic nerves (cardiac decentralization)
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