T-Wave Alternans Measured by 24-Hour Ambulatory Recordings Rather Than Exercise Stress Tests as a Risk Stratification Marker in Patients With Long QT Syndrome.

BACKGROUND: Few small-sample studies have quantified the T-wave alternans (TWA) value by 24-hour ambulatory recordings or exercise stress tests in patients with long QT syndrome (LQTS). The cutoff point of TWA ≥47 µV was based on patients with myocardial infarction. In our study, we aimed to (1) evaluate the association of TWA with life-threatening arrhythmic events (LAEs); (2) compare the predictive model of LAEs according to the TWA value measured by 24-hour ambulatory recordings and exercise stress tests; and (3) propose a cutoff point for the high risk of LAEs in patients with LQTS. METHODS AND RESULTS: The study cohort included 110 patients with LQTS referred to our hospital, and the primary outcome was LAEs. Thirty-one patients with LQTS (31/110 [28.2%]) developed LAEs during the following 24 (12-47) months. Peak TWA value quantified from 12 leads by 24-hour ambulatory recordings in patients with LQTS with LAEs (LQTS-LAEs group) was significantly higher than LQTS without LAEs (LQTS-non-LAEs group) (64.0 [42.0-86.0] µV versus 43.0 [36.0-53.0] µV; P<0.01). There was no statistical difference in TWA value measured by exercise stress tests between the 2 groups (69.0 [54.5-127.5] µV versus 68.5 [53.3-99.8] µV; P=0.871). The new cutoff point of the peak TWA value measured by 24-hour ambulatory recordings was 55.5 µV, with a sensitivity of 75.0% and a specificity of 78.6%. A univariate Cox regression analysis revealed that TWA value ≥55.5 µV was a strong predictor of LAEs (hazard ratio [HR], 4.5 [2.1-9.6]; P<0.001]. A multivariate Cox regression analysis indicated that TWA value ≥55.5 µV remained significant (HR, 2.7 [1.1-6.8]; P=0.034). CONCLUSIONS: Peak TWA measured by 24-hour ambulatory recordings was a more favorable risk stratification marker than exercise stress tests for patients with LQTS.

Natural History and Risk Stratification in Andersen-Tawil Syndrome Type 1.

BACKGROUND: Andersen-Tawil Syndrome type 1 (ATS1) is a rare arrhythmogenic disorder, caused by loss-of-function mutations in the KCNJ2 gene. We present here the largest cohort of patients with ATS1 with outcome data reported. OBJECTIVES: This study sought to define the risk of life-threatening arrhythmic events (LAE), identify predictors of such events, and define the efficacy of antiarrhythmic therapy in patients with ATS1. METHODS: Clinical and genetic data from consecutive patients with ATS1 from 23 centers were entered in a database implemented at ICS Maugeri in Pavia, Italy, and pooled for analysis. RESULTS: We enrolled 118 patients with ATS1 from 57 families (age 23 ± 17 years at enrollment). Over a median follow-up of 6.2 years (interquartile range: 2.7 to 16.5 years), 17 patients experienced a first LAE, with a cumulative probability of 7.9% at 5 years. An increased risk of LAE was associated with a history of syncope (hazard ratio [HR]: 4.54; p = 0.02), with the documentation of sustained ventricular tachycardia (HR 9.34; p = 0.001) and with the administration of amiodarone (HR: 268; p < 0.001). The rate of LAE without therapy (1.24 per 100 person-years [py]) was not reduced by beta-blockers alone (1.37 per 100 py; p = 1.00), or in combination with Class Ic antiarrhythmic drugs (1.46 per 100 py, p = 1.00). CONCLUSIONS: Our data demonstrate that the clinical course of patients with ATS1 is characterized by a high rate of LAE. A history of unexplained syncope or of documented sustained ventricular tachycardia is associated with a higher risk of LAE. Amiodarone is proarrhythmic and should be avoided in patients with ATS1.

Interplay Between Genetic Substrate, QTc Duration, and Arrhythmia Risk in Patients With Long QT Syndrome.

BACKGROUND: Long QT syndrome (LQTS) is a common inheritable arrhythmogenic disorder, often secondary to mutations in the KCNQ1, KCNH2, and SCN5A genes. The disease is characterized by a prolonged ventricular repolarization (QTc interval) that confers susceptibility to life-threatening arrhythmic events (LAEs). OBJECTIVES: This study sought to create an evidence-based risk stratification scheme to personalize the quantification of the arrhythmic risk in patients with LQTS. METHODS: Data from 1,710 patients with LQTS followed up for a median of 7.1 years (interquartile range [IQR]: 2.7 to 13.4 years) were analyzed to estimate the 5-year risk of LAEs based on QTc duration and genotype and to assess the antiarrhythmic efficacy of beta-blockers. RESULTS: The relationship between QTc duration and risk of events was investigated by comparison of linear and cubic spline models, and the linear model provided the best fit. The 5-year risk of LAEs while patients were off therapy was then calculated in a multivariable Cox model with QTc and genotype considered as independent factors. The estimated risk of LAEs increased by 15% for every 10-ms increment of QTc duration for all genotypes. Intergenotype comparison showed that the risk for patients with LQT2 and LQT3 increased by 130% and 157% at any QTc duration versus patients with LQT1. Analysis of response to beta-blockers showed that only nadolol reduced the arrhythmic risk in all genotypes significantly compared with no therapy (hazard ratio: 0.38; 95% confidence interval: 0.15 to 0.93; p = 0.03). CONCLUSIONS: The study provides an estimator of risk of LAEs in LQTS that allows a granular estimate of 5-year arrhythmic risk and demonstrate the superiority of nadolol in reducing the risk of LAEs in LQTS.