Effect of Classic or Delayed Ischemic Conditioning on Left Ventricular Pressure-Volume Relations in Dogs

Abstract

Objective: Non-pharmacologic interventions such as ischemic conditioning (IC) markedly reduce infarct size but it remains unclear whether this protection translates to a significant attenuation of ischemia-mediated LV contractile dysfunction. In this study we evaluated pressure-volume (P-V) data obtained by the load-insensitive conductance catheter method, to examine LV pressure-volume (LVP-V), diastolic function and ventricular-arterial coupling in anesthetized dogs exposed to ischemic conditioning (IC) or delayed IC (dIC; 48h prior to ischemia). The objective was to determine if IC, or dIC pre-treatment could influence post-ischemic recovery of LV contractile function. Methods: Three groups were studied – nIC, IC and dIC; all dogs underwent 90-min acute coronary occlusion (CO) followed by 180-min reperfusion (REP). IC consisted of 4 cycles of 5-min CO and 5-min REP of the left main coronary artery. LV P-V relations were constructed under steady-state conditions (by transient occlusion of the inferior vena cava) prior to IC treatment and at the end of the experiment; P-V loop data was also acquired at different points during the experiment to evaluate changes in end-systolic and end-diastolic parameters. Results: During CO dP/dtmax and dP/dtmin (indicator of rate of LV relaxation) decreased significantly compared to baseline in the IC group; these variables were unchanged in the dIC group. LVEF decreased during CO and REP in the nIC and IC groups but was stable in the dIC group. Tau was increased only in the IC group during CO and REP. ESV and EDV increased significantly in all groups during CO and REP; none of these negative effects was resorbed by the end of the experimental period. Conclusions: Diminished LV contractile function caused by CO did not improve with IC, or dIC pre-treatment, despite significant reduction in infarct size.