Clinical Electrophysiology -> SCA Risk Assessment: -> Other Noninvasive Techniques D-PO04 - Poster Session IV (ID 15) Poster

D-PO04-219 - Echocardiography-guided Risk Stratification For Long QT Syndrome: A Validation And Implementation Study Of The Electromechanical Window (ID 1240)

 A.M. Sugrue: Nothing relevant to disclose.


Background: The ability to identify those at the highest phenotypic risk for long QT syndrome (LQTS)-associated life-threatening cardiac events remains suboptimal.
Objective: This study aimed to validate whether the degree of electromechanical window (EMW) negativity, as derived from echocardiography, predicts symptomatic versus asymptomatic status in patients with LQTS.
Methods: We analyzed a cohort of 651 patients with LQTS (24 ± 16 years, 59% female, 158 symptomatic, LQT1 51%, LQT2 33%, LQT3 11%, multiple mutations 5%) and 30 healthy age- and sex-match controls. The EMW was calculated as the difference between the interval from QRS-onset to the aortic-valve closure midline and the subsequent ECG QT interval, for the same beat.
Results: A negative EMW was found amongst nearly all LQTS patients compared to controls, with more profound EMW negativity in patients with symptomatic LQTS compared to asymptomatic LQTS (-51 ± 37 vs -17 ± 34 ms, p < 0.0001). Logistic regression identified EMW, QTc, female gender, and LQTS genotype as univariate predictors of symptomatic status. After multivariate analysis, EMW remained an independent predictor of symptomatic status (ORs 1.37 odds ratio for each 10-ms decrease in the EMW, 95% CI, 1.27-1.47; P <0.0001). EMW outperformed QTc in predicting symptomatic patients (AUC 0.777 vs 0.728). EMW correlation from echocardiographic sonographers showed excellent reliability (ICC 0.87, 95% CI 0.74-0.95).
Conclusion: In this validation study, patients with a history of LQTS-associated life-threatening cardiac events had a more profoundly negative EMW. The EMW outperformed the QTc as a predictor of symptomatic status. EMW is now a clinically validated risk factor. In fact, our institution’s echocardiography clinical practice committee has now approved (December 2019) the EMW for patients with LQTS making it now a routinely reported echocardiographic finding.