Are Aging and Heart Failure Similar Syndromes of Sympathetic Dysregulation?

Abstract

Both heart failure (HF) and aging alter the basal regulation of sympathetic nerve discharge (SND) and the majority of HF patients are aged, however, the effect of combined aging and HF on SND regulation to acute stress is not well established. We tested the hypothesis that aging and HF are not similar syndromes of sympathetic nervous system dysregulation, as evidenced by differences in SND (renal and splenic) responses to heat stress in young HF compared with aged HF rats and in aged HF compared with aged non‐HF rats. Anesthetized young (3–6 months) and aged (24–25 months) F344 rats received either a surgically‐induced myocardial infarction or a sham operation. Heating experiments (internal body temperature, Tc, increased to 41.5°C) were completed in chloralose‐urethane anesthetized rats 4–6 weeks after the myocardial (or sham) infarction procedure. Left ventricular (LV) function was determined by measuring left ventricular end diastolic pressure (LVEDP) and comparing dimensions of the left atrium (LA) and the aorta (Ao) (LA/Ao ratio) using echocardiographic techniques. Preliminary results indicate that LVEDP and LA/Ao ratio and SND responses to acute thermal stress may differ in young HF compared with aged HF rats and in aged HF compared with aged non‐HF rats. These findings suggest that both age and HF should be considered when determining mechanisms regulating SND responses to acute environmental stress. Funding provided by NIH HL091342.