Another Marker of Severe Mitral Regurgitation
By Michael H. Crawford, MD, Editor
SYNOPSIS: A small retrospective study showed Doppler echocardiography-derived left ventricular ejection time is an independent predictor of adverse outcomes in patients with moderate or worse mitral valve regurgitation.
SOURCE: Altes A, Bernard J, Dumortier H, et al. Significance of left ventricular ejection time in primary mitral regurgitation. Am J Cardiol 2022;178:97-105.
Current markers for when to surgically correct severe mitral regurgitation (MR) may identify only those at higher risk of postoperative mortality. Identifying markers for earlier intervention was the goal of this study created by investigators from Quebec, Canada, and Lille, France.
Left ventricular ejection time (LVET) is known to correlate with LV function. Altes et al hypothesized LVET would correlate with the severity of MR as well as LV performance and predict outcomes in patients with moderate to severe MR caused by mitral valve prolapse (MVP). The study population included 302 consecutive patients with moderate or worse MR caused by MVP (median age = 61 years; 34% were women). The authors excluded patients with active endocarditis, other more than mild left heart valve disease, New York Heart Association class ≥ III, or a class I or IIa guideline recommendation for MV surgery. Although researchers collected the data prospectively from 2008 to 2019, they analyzed the information retrospectively. The authors measured LVET as the time from aortic valve opening to closing on pulsed wave Doppler of the transaortic valve flow. The primary endpoint was the composite of MV surgery or all-cause mortality. Heart teams at the two participating institutions made decisions regarding surgery.
After a median follow-up of 66 months, 178 patients achieved the primary endpoint. Patients in the lowest quartile of LVET (< 260 ms) were at the highest risk of the primary endpoint vs. those in the higher quartiles (P = 0.005). Patients with LVET less than 260 were more often men (P = 0.003), exhibited a flail leaflet, were living with more severe MR, larger LVs and left atria, and lower stroke volume indices (for all instances, P < 0.001). After adjustment for clinical predictors of outcome, such as age, atrial fibrillation, MR severity, and achieving guideline class I indicators for MV surgery in asymptomatic patients, LVET < 260 ms was associated with a higher incidence of achieving the primary outcome (HR, 1.49; 95% CI, 1.03-2.16; P = 0.033). The estimated four-year event-free survival rate was 33% for those with LVET < 260 ms vs. 50% among the rest (P < 0.001). Also, an LVET < 260 ms raised the adjusted all-cause mortality risk (HR, 2.56; 95% CI, 1.25-5.25; P = 0.01). The authors concluded a shorter LVET was associated with a higher risk of MV surgery or all-cause mortality in patients with moderate or worse MR caused by MVP.
COMMENTARY
The Holy Grail of managing asymptomatic patients with moderate or worse primary MR is a parameter that would indicate early surgery would be superior to watchful waiting. Early surgery can be contemplated in asymptomatic patients if LV ejection fraction (EF) is < 60%, if end-systolic LV diameter is ≥ 40 mm (both class I), or if the patient develops atrial fibrillation or significant (> 60 mL/m²) left atrial dilatation (both class IIa) — as long as the valve anatomy is suitable for a durable repair. However, these parameters also are predictors of postoperative long-term mortality.
More sensitive parameters of early LV dysfunction would be advantageous. LVET has been shown in heart failure with reduced LVEF populations to be predictive of adverse outcomes. Also, it is an easy-to-make and reproducible measurement on a standard pulsed Doppler recording of the aortic valve systolic velocity. Thus, incorporating LVET in the echocardiographic studies of MR patients is attractive and may contribute to decisions about surgery.
As the Altes et al study showed, LVET was related to the severity of MR indirectly because it reflected the time available for forward flow, which is important for organ perfusion. The shorter LVET is in MR patients, the greater the backward flow and the less the forward flow. Heart rate affects LVET; however, in the Altes et al study, correcting for heart rate did not alter the results.
The main outcome associated with a short LVET was meeting clinical criteria for surgery, which occurred in 142 patients over the median four-year follow-up. However, there were 45 deaths, nine among surgical patients. Whether earlier surgery would have lowered the death rate is unknown, but it is reasonable to think it might.
There are limitations to an observational, retrospective study, so causality cannot be inferred. Also, the sample size here was small. A larger prospective study would be necessary to fully assess the value of LVET for surgical decision-making among MR patients. Further, the increased use of percutaneous edge to edge repair and (perhaps soon) percutaneous MV replacement will alter the landscape of moderate or worse MR.
Even surgical repair is becoming less invasive thanks to contemporary advances in apical puncture techniques for delivering new chordae. However, putting LVET into the intervention decision mix is not unreasonable, given the ease of measuring it and the solid theoretical aspects of its importance. Nevertheless, at this time, this measurement is not the deciding factor.
A small retrospective study showed Doppler echocardiography-derived left ventricular ejection time is an independent predictor of adverse outcomes in patients with moderate or worse mitral valve regurgitation.
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