COMPARATIVE EFFECTS OF PACING-INDUCED AND BALLOON CORONARY-OCCLUSION ISCHEMIA ON LEFT-VENTRICULAR DIASTOLIC FUNCTION IN MAN

Background. Effects of pacing-induced and coronary occlusion myocardial ischemia on left ventricular (LV) function have been compared only in anesthetized dogs. Diastolic properties of the same LV anterior wall segment were therefore compared in 12 patients with single-vessel proximal left anterior descending coronary artery stenosis at rest, immediately after 7 +/- 1.2 minutes of pacing, and at the end of a 1-minute balloon occlusion of coronary angioplasty (CO). Methods and Results. Shifts of the diastolic LV pressure-length relation, derived from simultaneous tip-micromanometer LV pressure recordings and digital subtraction LV angiograms, were used as an index of regional diastolic LV distensibility of the anterior wall segment. Immediately after pacing, LV end-diastolic pressure rose from 13.5 +/- 3.5 to 23.8 +/- 7.0 mm Hg (p < 0.01 versus at rest) without a significant change of the LV end-diastolic volume index (83.1 +/- 18.9 versus 88.4 +/- 16.5 ml/m2), percentage systolic shortening (%SS) of the ischemic segment fell from 40.1 +/- 10.6% to 25.2 +/- 8.6% (p < 0.01), and the diastolic LV pressure-radial length (P-RL) plot of the ischemic segment was shifted upward by 7.1 +/- 5.0 mm Hg for portions of the plot that overlapped with the diastolic LV P-RL plot at rest. At the end of CO, LV end-diastolic pressure rose to 20.8 +/- 7.8 mm Hg (p < 0.01 versus at rest) and the LV end-diastolic volume index rose to 95.6 +/- 16.3 ml/m2 (p < 0.05 versus at rest, p < 0.05 versus after pacing). Ejection fraction and %SS of the ischemic segment fell respectively from 76.6 +/- 6.8% to 46.6 +/- 11.4% (p < 0.01 versus at rest, p < 0.01 versus after pacing) and from 40.1 +/- 10.6% to 6.4 +/- 6% (p < 0.01 versus at rest, p < 0.01 versus after pacing). The diastolic LV P-RL plot of the ischemic segment was shifted upward by 3.1 +/- 2.3 mm Hg for portions of the plot that overlapped with the diastolic LV P-RL plot at rest. This upward shift at the end of CO was significantly smaller (p < 0.05) than that immediately after pacing. At the end of CO, a correlation (p < 0.03) was observed for the ischemic segment between %SS and upward shift of the diastolic LV P-RL plot. Conclusions. The upward shift of the diastolic LV P-RL plot, which was used as an index of decreased regional diastolic LV distensibility, was larger immediately after pacing than at the end of CO. Persistent systolic shortening of ischemic myocardium seems to be a prerequisite for a decrease in diastolic distensibility of the ischemic segment because of the higher %SS of the ischemic segment immediately after pacing, and because of the correlation at the end of CO between the upward shift of the diastolic LV P-RL plot and %SS of the ischemic segment.