Dynamic geometry of the left ventricle in mitral regurgitation

Abstract

High speed biplane left ventricular (LV) cineangiograms were analyzed for changes in volume, shape, and dimensions in 35 patients. Ventriculographic studies in ten normal subjects characterized by an ejection fraction EF) of 67±2% and an end diastolic volume (EDV) of 90±8 ml/m2 were compared with results from 25 patients with isolated mitral regurgitation of varying severity. Patients with mitral regurgitation (MR) were subdivided according to whether or not the ejection fraction was normal. Those with normal EF (70±2%) were termed compensated MR (CMR) and had EDV of 192±7 ml/m2. Those with decreased EF 34±3% were termed decompensated MR (DMR) and had EDV of 277±17 ml/m2. In normal subjects no significant changes in LV dimensions were noted during the isovolumic phase of contraction while in patients with compensated MR the transverse axis shortened an average of 5.2% with no change in the longitudinal axis (L). Changes in geometry prior to ejection were less evident in the group with decompensated MR. In normal subjects during ejection the extent of circumferential fiber shortening was 38±1%, and longitudinal shortening was 18±1%. In CMR slightly greater changes were observed in LV dimensions. In DMR both circumferential and longitudinal shortening was significantly reduced (17±2% and 8±1%, respectively). Assuming an ellipsoidal model of the LV chamber, eccentricity (e) was calculated to assess the degree of roundness. In normal subjects, e increased from 0.85 at end diastole to 0.92 at end systole. In compensated MR, end diastolic shape was more rounded with e increasing from 0.75 to 0.88 during systole. In decompensated MR there was only a small charge in e from 0.70 to 0.73 during systole, indicating that a globular configuration persisted in systole as well as diastole. These differences could not be satisfactorily explained in terms of etiology, age, regurgitant volume load or its duration. The differences between the two groups of patients were best expressed by the difference in ejection fraction and globularity of the LV. A relationship to absolute EDV between the two groups was less evident. These differences may be due to development of organic changes in the architecture of heart wall in those patients with decompensated MR.