Key result
Electromechanical window negativity independently predicted symptomatic status in patients with Long QT Syndrome (OR 1.37 per 10-ms decrease; 95% CI 1.27-1.48; P<0.0001).
Why the study?
The ability to identify patients at highest phenotypic risk for LQTS-associated life-threatening cardiac events remains suboptimal.
Does echocardiography-derived electromechanical window (EMW) negativity predict symptomatic status better than QTc in patients with Long QT Syndrome?
Cohort (n=701)
Does echocardiography-derived electromechanical window (EMW) negativity predict symptomatic status better than QTc in patients with Long QT Syndrome?
Captured external expert commentary on this paper, strongest first. Original sources are linked where available.
“Importantly, it confirms the reliability of measuring this signal at routine echocardiography, with an intraclass correlation coefficient (ICC) of 0.93 (95% confidence interval: 0.89 to 0.96) among 22 sonographers who underwent a short training process. Indeed, the major source of variance between observers was the electrocardiogram rather than the Doppler measurement.”
Echocardiography-derived electromechanical window (EMW) negativity is a validated, independent risk factor that outperforms QTc in identifying LQTS patients at risk for life-threatening cardiac events.
BACKGROUND The ability to identify those patients at the highest phenotypic risk for long QT syndrome (LQTS)-associated life-threatening cardiac events remains suboptimal. OBJECTIVES This study sought to validate the association between electromechanical window (EMW) negativity, as derived from echocardiography, and symptomatic versus asymptomatic status in patients with LQTS. METHODS We analyzed a cohort of 651 patients with LQTS (age 26 ± 17 years; 60% females; 158 symptomatic; 51% LQTS type 1; 33% LQTS type 2; 11% LQTS type 3; 5% multiple mutations) and 50 healthy controls. EMW was calculated as the difference between the interval from QRS onset to aortic valve closure midline, as derived for continuous-wave Doppler, and the electrocardiogram-derived QT interval for the same beat. RESULTS A negative EMW was found among nearly all patients with LQTS compared to controls, with more profound EMW negativity in patients with symptomatic LQTS compared to those with asymptomatic LQTS (-52 ± 38 ms vs. -18 ± 29 ms; p < 0.0001). Logistic regression identified EMW, heart rate-corrected QT interval (QTc), female sex, and LQTS genotype as univariate predictors of symptomatic status. After multivariate analysis, EMW remained an independent predictor of symptomatic status (odds ratio for each 10-ms decrease in EMW: 1.37; 95% confidence interval: 1.27 to 1.48; p < 0.0001). EMW outperformed QTc in predicting symptomatic patients (area under the curve: 0.78 vs. 0.70; p = 0.01). After training and implementation, EMW correlation from echocardiographic sonographers showed excellent reliability (intraclass correlation coefficient: 0.93; 95% confidence interval: 0.89 to 0.96). CONCLUSIONS In this validation study, patients with a history of LQTS-associated life-threatening cardiac events had a more profoundly negative EMW. EMW outperformed heart rate-corrected QT interval as a predictor of symptomatic status. EMW is now a clinically validated risk factor. In December 2019, our institution's echocardiography clinical practice committee approved use of EMW for patients with LQTS, making it a routinely reported echocardiographic finding.
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Sugrue et al. (2020) conducted a cohort in Long QT Syndrome (n=701). Electromechanical window (EMW) negativity was evaluated on Symptomatic status (OR 1.37, 95% CI 1.27 to 1.48, p=<0.0001). Electromechanical window negativity independently predicted symptomatic status in patients with Long QT Syndrome (OR 1.37 per 10-ms decrease; 95% CI 1.27-1.48; P<0.0001).
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