Relationship Between QT Interval and Outcome in Low-Flow Low-Gradient Aortic Stenosis With Low Left Ventricular Ejection Fraction

Abstract

Background: QT interval has been shown to be associated with cardiovascular events. There is no data regarding the association between QT interval and left ventricular (LV) function and prognosis in patients with low LV ejection fraction (LVEF), low-flow, low-gradient aortic stenosis (LF-LG AS). We aimed to examine the relationship between corrected QT interval (QT_c) and LV function and outcome in these patients.

Methods and results: Ninety-three patients (73±10 years; 74% men) with LF-LG AS (mean gradient <40 mm Hg and indexed aortic valve area ≤0.6 cm²/m²) and reduced LVEF (≤40%) were prospectively included in this analysis and 63 of them underwent aortic valve replacement within 3 months following inclusion. Prolonged QT_c was defined as QT_c >450 ms in men and >470 ms in women. LV global longitudinal strain was measured by speckle tracking and expressed in absolute value |%|. QT_c correlated with the following: global longitudinal strain (r=-0.40, P=0.005), LVEF (r=-0.27, P=0.02), stroke volume (r=-0.35, P=0.007), and B-type natriuretic peptide (r=0.45, P=0.0006). During a median follow-up of 2.0 years, 49 patients died. Prolonged QT_c was associated with a 2-fold increase in all-cause mortality (hazard ratio=2.05; P=0.01) and cardiovascular mortality (hazard ratio=1.89; P=0.04). In multivariable analysis adjusted for EuroSCORE, aortic valve replacement, previous myocardial infarction, LVEF, and ß-blocker medication, prolonged QT_c was independently associated with all-cause mortality (hazard ratio=2.56; P=0.008) and cardiovascular mortality (hazard ratio=2.50; P=0.02).

Conclusions: In patients with LF-LG AS and reduced LVEF, longer QT_c interval was associated with worse LV function and increased risk of death. Assessment of QT_c may provide a simple and inexpensive tool to enhance risk stratification in LF-LG AS patients.

Clinical trial registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT 01835028.

Trial registration: ClinicalTrials.gov NCT01835028.

Keywords: B‐type natriuretic peptide; Doppler‐echocardiography; QT interval; aortic stenosis; left ventricular function; low‐flow low gradient; outcome; risk stratification.