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LV volume may work as well as linear measures in pinpointing aortic regurgitation mortality risk

JAMA Cardiology
Reuters Health - 10/11/2020 - In asymptomatic patients with chronic aortic regurgitation (AR), left ventricular end-systolic volume index (LVESVi) and volume-derived LV ejection fraction (Vol-LVEF) work as well as LV end-systolic dimension index (LVESDi) and linear LVEF in pinpointing those at greatest risk of death, researchers suggest.

Further, a LVESVi threshold of 45 mL/m(2) or higher was significantly associated with an increased mortality risk.

"Given that transthoracic echocardiography remains the first-line modality for the comprehensive imaging assessment of AR, our findings expand the armamentarium of LV parameters available for risk stratification of asymptomatic patients," Dr. Hector Michelena of the Mayo Clinic in Rochester, Minnesota told Reuters Health by email.

"In addition, our findings suggest the possibility that as a risk-marker, a LVESVi cutoff of 45 ml/m2 could be superior to its linear counterpart (LVESDI cutoff of 20 mm/m2), a notion that needs verification in future studies," he said. "Finally, retention of the independent prognostic value of LV volumes when performed during routine clinical practice and by multiple observers (scalability) has not yet been demonstrated."

Dr. Michelena and colleagues analyzed clinical and echocardiographic data on 492 consecutive asymptomatic patients with chronic moderately severe to severe AR (mean age, 60; 86% men) from January 2004 through April 2019.

As reported in JAMA Cardiology, ischemic heart disease prevalence was low (9%), and 92% of patients had preserved linear LVEF (50% or greater) with a mean LVESVi of 41 mL/m2.

At a median of 5.4 years, 13.4% of patients had died under medical surveillance, and overall survival was not different from the age- and sex-matched general population.

Various multivariate models, adjusted for age, sex, Charlson Comorbidity Index, and AR severity, showed that in addition to linear LVEF and LVESDi, LVESVi and Vol-LVEF were independently associated with mortality under surveillance, with similar C statistics.

Spline curves showed that continuous risks of death began to rise for both linear LVEF and Vol-LVEF less than 60%; LVESVi more than 40 mL/m2 to 45 mL/m2; and LVESDi above 21 mm/m2 to 22 mm/m2.

As dichotomized variables, patients with LVESVi more than 45 mL/m2 demonstrated increased relative death risk (hazard ratio, 1.93), whereas LVESDi more than 20 mm/m2 did not.

Further, LVESVi more than 45 mL/m2 showed a decreased survival trend compared with the expected population survival.

JAMA Cardiology Editor Dr. Robert Bonow of the Northwestern University Feinberg School of Medicine in Chicago told Reuters Health by email, "Linear measurements of LV dimensions are inherently imprecise in estimating true LV volumes, as the shape of the ventricle is highly variable; it remodels in response to the volume overload," he explained. "It is also unclear whether one should measure the LV dimension using the standard recommendation at the tips of the mitral leaflets or deeper in the cavity of a spherical ventricle where the diameter is greatest."

"As most echocardiography laboratories have evolved to reporting LV volumes rather than (or in addition to) linear dimensions, as recommended by the American Society of Echocardiography and European Society of Cardiovascular Imaging, it would be helpful to have natural history data identifying values of LV end systolic volume that are associated with outcomes in patients with AR, and thus the current study represents a step forward," he said.

Importantly, he noted, the threshold for identifying patients at highest risk (LVESV index of 45 mL/m2) "is precisely the threshold value defined by the ASE/ESCVI to represent severe LV dilation, hence providing some validity to applying the ASE/ESCVI volumetric criteria to patients with chronic AR going forward."

That said, he added, "it is also important to note that the standard linear measurements of LV systolic dimension appear to have worked equally well in this study. This is one step forward, but we do need further studies to confirm these results to know how to assimilate them into clinical practice."

By Marilynn Larkin

SOURCE: https://bit.ly/2ItqN7F and https://bit.ly/2GMqEMb JAMA Cardiology, online November 4, 2020.

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