The Effect of Left Ventricular Chamber Compliance on Early Diastolic Filling during Coronary Reperfusion

This study was designed to assess the changes in left ventricular (LV) diastolic filling and to evaluate the dynamic determinants of LV diastolic filling during coronary reperfusion after acute myocardial ischemia. We examined LV diastolic pressure-volume relations (D-PVRs) using the conductance catheter technique with a high-fidelity micromanometer, and the transmitral flow using transesophageal pulsed Doppler echocardiography in 9 open-chest anesthetized dogs with the pericardium opened. We measured early diastolic peak flow velocity(E), late diastolic peak flow velocity (A), the ratio of peak E to peak A (E/A), operational chamber compliance at the minimum LV pressure [(dV/VdP)nadir], and the time constant of LV relaxation (TC). Acute regional myocardial ischemia was produced by occluding the proximal portion of the left anterior descending coronary artery. Data were acquired at baseline, 10 min after acute myocardial ischemia, and after 15 and 90 min of reperfusion under left atrial pacing at 100 beats/min. During myocardial ischemia, D-PVRs shifted upward and rightward on the same curvilinear relationship compared with that at baseline (LV end-diastolic pressure (LVEDP) from 7.3 to 10.5 mmHg, LVEDV from 25 to 31 ml, both p<0.01), accompanied by a decrease in peak E and E/A (E from 41 to 25 cm/sec, E/A from 1.7 to 1.1, both p<0.01) and a prolongation of TC (from 25.4 to 30.3 msec, p<0.01). After coronary reperfusion, D-PVRs returned to baseline accompanied by an improvement in the peak E and E/A ratio. No significant changes in peak A were observed in any of the stages. There was no correlation between peak E and TC, however, a significant positive correlation was observed between peak E and (dV/VdP)nadir (r=0.76, p<0.01). In conclusion, this study demonstrated that, using pulsed Doppler echocardiography, the improvement of diastolic filling after coronary reperfusion was based mainly on changes in early diastolic filling, and that LV operational chamber compliance at early diastole, rather than a LV relaxation property, might play an important role in determining early diastolic filling during coronary reperfusion.