Can the echocardiographic LV mass equation reliably demonstrate stable LV mass following acute change in LV load?

Background: Limited data are available on performance of the left ventricular (LV) mass equation when there is a dynamic change to LV load. We aimed to test this equation in the immediate post-operative period following aortic valve replacement (AVR) for aortic regurgitation (AR) to see if it would reliably demonstrate stable LV mass before and after surgery. Since LV mass would be unlikely to change in the immediate postoperative period, we hypothesized that a decrease in LV diameter postoperatively would be accompanied by concomitant increases in LV wall thickness as predicted by the LV mass equation.

Methods: We reviewed echocardiograms of adult patients with AR who underwent AVR from 2007-2017 at Montefiore Medical Center (n=28). Three independent readers performed septal wall thickness (SWT), posterior wall thickness (PWT) and left ventricular internal diameter (LVID) measurements on pre-operative and post-operative echocardiograms. LV masses were calculated using the American Society of Echocardiography (ASE) equation.

Results: Post-operatively, LVID decreased from 5.7±1.2 to 4.9±1.0 cm, P<0.001. SWT was noted to increase from 1.08±0.20 to 1.18±0.27 cm, P=0.03, but PWT was unchanged, 1.11±0.21 to 1.16±0.27 cm, P=0.21. Accordingly, the LV mass equation calculated a decrease in LV mass from 266±126 to 232±99 gm, P=0.01. A control group of coronary artery bypass grafting alone (n=14) did not demonstrate any significant change in SWT, LVID, PWT and LV mass measurements. Similar findings were found for all three readers.

Conclusions: Following aortic valve replacement for regurgitation, the LV mass equation calculated a reduction in LV mass in the immediate postoperative period. Since an immediate change in LV mass after AVR is unlikely, we feel that these results highlight an important limitation of the mass equation, when used with acutely changing loading conditions.