Reply to “Moving Beyond Linear Formulas for Left Ventricular Mass in Aortic Valve Replacement”

Abstract

We thank Moneghetti and colleagues for acknowledging positively our investigative result related to a potential pitfall of the linear echocardiography method for calculating left ventricular (LV) mass. The Devereux LV mass formula is the most widely used echocardiographic method to estimate LV mass and it has been a reliable predictor of cardiovascular outcomes in various populations. The formula was originally derived from the cube function of the LV end-diastolic dimension, posterior wall thickness, and interventricular septal thickness. The LV mass estimated from this formula was validated against the anatomically measured LV mass in 34 patients. The main point of our paper was to provide an explanation for the paradoxical finding of a greater and faster LV mass reduction in patients with severe aortic stenosis after surgical aortic valve replacement (SAVR) compared to after transcatheter AVR (TAVR) despite better hemodynamics with transcatheter aortic prostheses. In evaluating the echocardiographic parameters used to calculate LV mass in the CoreValve high-risk trial, we found that LV end-diastolic dimension became significantly smaller soon after SAVR, but not after TAVR, while both posterior and ventricular septal wall thickness decreased in both groups over time and to a similar extent. The smaller LV end-diastolic dimension after SAVR was responsible for the paradoxical faster and greater regression of the calculated LV mass. The reduced LV dimension after SAVR appeared to be related to reduced stroke volume after SAVR which did not occur after TAVR. There are several other echocardiographic methods to calculate LV mass. The Area-length method has also been well-validated against LV mass calculated by cardiac magnetic resonance imaging (MRI). The Area-length method uses LV cavity long-axis dimension and short-axis area. However, the Area-length method would also be falsely reduced if stroke volume decreases immediately after SAVR. There are several alternative means to compare LV mass regression after SAVR and TAVR. As suggested by Moneghetti and colleagues, 3D echocardiography or other imaging techniques such as cardiac computed tomography (CT) or cardiac MRI should provide more accurate LV mass calculations without being affected by acute changes in LV dimensions. We are currently conducting a prospective study to compare LV mass after SAVR and TAVR using cardiac CT, and hope to share our data soon. Ana Kadkhodayan has nothing to disclose. Dr. Jae K. Oh has received research support for the echocardiographic core laboratory from Medtronic.