By Michael H. Crawford, MD, Editor
SYNOPSIS: A study of a cardiac resynchronization therapy registry demonstrated right ventricular free wall strain by speckle tracking 2D echocardiography is more sensitive for detecting right ventricular dysfunction vs. other echo measures of right ventricular function.
SOURCE: Stassen J, van der Bijl P, Galloo X, et al. Prognostic implications of right ventricular free wall strain in recipients of cardiac resynchronization therapy. Am J Cardiol 2022;171:151-158.
In patients with heart failure (HF) with reduced left ventricular (LV) ejection fraction (EF) and a wide QRS on ECG, cardiac resynchronization therapy (CRT) can alleviate symptoms, but mortality remains high. Right ventricular (RV) function is a major determinant of outcomes in patients with HF with reduced EF (HFrEF). However, how to best assess RV function is challenging and controversial because of the complexity of RV morphology.
Investigators from the Netherlands tested the hypothesis that RV free wall longitudinal strain (FWS) by speckle tracking 2D echocardiography may improve the risk stratification of patients undergoing CRT vs. the usual assessment of RV fractional area change (FAC) and tricuspid annulus plane systolic excursion (TAPSE). Stassen et al examined the Leiden University Medical Centre CRT registry, which included 871 symptomatic patients with HFrEF (mean age, 65 years; 75% men).
All patients had undergone complete echo exams before CRT, and RV function measurements were made in the apical four-chamber view focused on the RV using GE Vingmed echo equipment. RV dysfunction has been defined as a FWS < 23% (they multiply by -1 to make a positive number), a FAC of < 35%, and a TAPSE < 17 mm. The primary endpoint was all-cause mortality over a mean follow-up of eight years.
Researchers found an abnormal FWS identified more patients with RV dysfunction vs. TAPSE or FAC (81% vs. 61% vs. 44%, respectively). All-cause mortality was 60% during the follow-up period. RV function measured by all three parameters was predictive of the primary outcome, but FWS was of incremental prognostic value compared to the other measures and clinical data on multivariable analysis (HR, 1.6; 95% CI, 1.3-2.1; P < 0.001).
The authors concluded FWS is more sensitive than the usual echo measures of RV function for detecting RV dysfunction and is of incremental value to the other measures and clinical data for predicting all-cause mortality.
COMMENTARY
Global longitudinal LV strain is used routinely to detect subtle changes in LV function in patients undergoing chemotherapy with potentially cardiotoxic drugs that are not detected by EF. Using RV FWS is less common for any application. The concept makes sense, though, as the RV is made up of mainly longitudinal fibers. In addition to its greater sensitivity for RV dysfunction, FWS is less angle-dependent than TAPSE and more reproducible than FAC. Also, FWS may be more load-independent.
Conceivably, RV FWS for patients undergoing CRT could be used to intensify medical therapy that would favor the RV, such as reductions in volume by diuresis or preventing tricuspid regurgitation by interventional techniques and alleviating RV pressure with pulmonary vasodilators. Also, revascularization could lower the rate of RV ischemia. More studies are needed to confirm this echo information is of clinical value.
Meanwhile, the retrospective, observational nature of this study may mean there were unmeasured confounders that affected the results. Also, HF treatment was not standardized. There was no comparative standard for the study, such as cardiac MRI or 3D echo. In addition, the authors did not present any echo data post-CRT. Finally, mortality could not be further characterized as cardiac or other etiologies.
Another issue is that normal values for FWS are vendor-specific, so the normal values used here may not apply to other echo equipment. At this time, we should start incorporating RV FWS into selected patients’ echo studies and gain more experience with this measure. However, it may be premature to make clinical decisions based on RV FWS alone.
