The extent to which cardiac nerves influence responses of regional ventricular function to acute myocardial ischemia was investigated in conscious dogs with intact cardiac innervation (N) and dogs with chronic cardiac denervation (D). Following coronary artery occlusion (CAO) left ventricular (LV) end-diastolic pressure increased more (P < 0.01) in D (18 ± 3.2 mmHg) than in N dogs (3.4 ± 0.7 mmHg), whereas heart rate increased more in N (32 ± 4.8 beats/min) than in D dogs (16 ± 3.0 beats/min). In nonischemic zones of D dogs there were greater increases, P < 0.05, in end-diastolic segment length, systolic segment shortening, and velocity of shortening than in N dogs. In ischemic zones, significantly greater increases in end-diastolic segment length were also observed in the D group, but similar reductions in segmental shortening occurred in both N (-116 ± 2.8%) and D (-108 ± 5.2%) dogs. The time constant of isovolumic relaxation was not different in the two groups. However, in ischemic zones of N dogs myocardial stiffness constant (κ) increased by 109 ± 24 from 33 ± 4.9 and end-diastolic stiffness (E(ed)) rose by 1527 ± 310 from 253 ± 34 mmHg, whereas κ increased significantly less (P < 0.05) in D dogs. E(ed) of ischemic zones also rose significantly less (P < 0.05) in D dogs. Thus in conscious dogs, chronic D does not attenuate depression of LV function in ischemic zones, but is associated with enhanced regional function of non-ischemic myocardium through the Frank-Starling mechanism and delayed increases in myocardial stiffness in the ischemic zone, despite larger increases in LV end-diastolic pressure.
|Original language||English (US)|
|Journal||American Journal of Physiology - Heart and Circulatory Physiology|
|Issue number||1 (21/1)|
|State||Published - 1987|
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine
- Physiology (medical)