Alterations in left ventricular relaxation, early diastolic filling and passive viscoelastic properties during postpacing ischemia

Alterations in left ventricular relaxation, early diastolic filling, regional myocardial dynamics and passive viscoelastic properties during postpacing ischemia were studied in 9 patients with coronary artery disease. In all patients typical anginal pain developed during pacing tachycardia, and in the postpacing beat, left ventricular end-diastolic pressure increased from 14 +/- 4 to 26 +/- 5 mm Hg (mean +/- standard deviation, p less than 0.01), relaxation time constant increased from 44 +/- 9 to 59 +/- 7 ms (p less than 0.01) and ejection fraction diminished from 63.1 +/- 9.1 to 52.8 +/- 10.8% (p less than 0.01). However, peak rate of early left ventricular filling obtained from frame-by-frame analysis of left ventriculograms did not change significantly. The time difference from segmental peak lengthening to left ventricular peak filling increased significantly in the ischemic segment (32 +/- 30 vs 77 +/- 49 ms, p less than 0.05). Chamber stiffness constant of a viscoelastic model increased significantly from 0.0177 +/- 0.01 to 0.0354 +/- 0.015 (p less than 0.01) without change in chamber viscosity constant. In the ischemic segment, peak rate of lengthening decreased by 45% with ischemia, and peak rate of lengthening normalized for the end-diastolic segment length by 36%. However, peak rate of lengthening normalized for the extent of systolic shortening did not change. The control segment showed a tendency to increase in these 3 parameters, but the changes were not statistically significant. Thus, peak rate of segmental myocardial lengthening decreased with ischemia because of a decrease in segmental shortening.(ABSTRACT TRUNCATED AT 250 WORDS)