Outcome by Sex in Patients With Long QT Syndrome With an Implantable Cardioverter Defibrillator

Holter Electrocardiographic Approach to Predicting Outcomes of Pediatric Patients With Long QT Syndrome

BACKGROUND

This study was performed to clarify the clinical findings of pediatric patients diagnosed with long QT syndrome (LQTS) through electrocardiographic screening programs and to predict their outcome using Holter electrocardiographic approaches.Methods and Results: This retrospective study included pediatric patients with a Schwartz score of ≥3.5 who visited the National Hospital Organization Kagoshima Medical Center between April 2005 and March 2019. Resting 12-lead and Holter electrocardiograms were recorded at every visit. The maximum resting QTc and maximum Holter QTc values among all recordings were used for statistical analyses. To test the prognostic value of QTc for the appearance of cardiac events after the first hospital visit, receiver operating characteristic curves were used to calculate the area under the curve (AUC). Among 207 patients, 181 (87%) were diagnosed through screening programs. The prevalence of cardiac events after the first hospital visit was 4% (8/207). Among QTc at diagnosis, maximum resting QTc, and maximum Holter QTc, only maximum Holter QTc value was a predictor (P=0.02) of cardiac events after the hospital visit in multivariate regression analysis. The AUC of the maximum Holter QTc was significantly superior to that of maximum resting QTc.

CONCLUSIONS

The maximum Holter QTc value can be used to predict the appearance of symptoms in pediatric patients with LQTS.

Genetic variant annotation scores in congenital long QT syndrome

BACKGROUND

Congenital Long QT Syndrome (LQTS) is a hereditary arrhythmic disorder. We aimed to assess the performance of current genetic variant annotation scores among LQTS patients and their predictive impact.

METHODS

We evaluated 2025 patients with unique mutations for LQT1-LQT3. A patient-specific score was calculated for each of four established genetic variant annotation algorithms: CADD, SIFT, REVEL, and PolyPhen-2. The scores were tested for the identification of LQTS and their predictive performance for cardiac events (CE) and life-threatening events (LTE) and then compared with the predictive performance of LQTS categorization based on mutation location/function. Score performance was tested using Harrell's C-index.

RESULTS

A total of 917 subjects were classified as LQT1, 838 as LQT2, and 270 as LQT3. The identification of a pathogenic variant occurred in 99% with CADD, 92% with SIFT, 100% with REVEL, and 86% with PolyPhen-2. However, none of the genetic scores correlated with the risk of CE (Harrell's C-index: CADD = 0.50, SIFT = 0.51, REVEL = 0.50, and PolyPhen-2 = 0.52) or LTE (Harrell's C-index: CADD = 0.50, SIFT = 0.53, REVEL = 0.54, and PolyPhen-2 = 0.52). In contrast, high-risk mutation categorization based on location/function was a powerful independent predictor of CE (HR = 1.88; p < .001) and LTE (HR = 1.89, p < .001).

CONCLUSION

In congenital LQTS patients, well-established algorithms (CADD, SIFT, REVEL, and PolyPhen-2) were able to identify the majority of the causal variants as pathogenic. However, the scores did not predict clinical outcomes. These results indicate that mutation location/functional assays are essential for accurate interpretation of the risk associated with LQTS mutations.

Performance evaluation of implantable cardioverter-defibrillators with SmartShock technology in patients with inherited arrhythmogenic diseases

BACKGROUND

Patients with inherited arrhythmogenic diseases (IADs) are often prescribed preventative implantable cardioverter-defibrillators (ICDs) to manage their increased sudden cardiac arrest risk. However, it has been suggested that ICDs in IAD patients may come with additional risk. We aimed to leverage the PainFree SmartShock Technology dataset to compare inappropriate therapies, appropriate therapies, mortality, and complications in patients with and without IAD.

METHODS

This retrospective analysis included extracted, physician-adjudicated, arrhythmic episodes from ICD devices. The incidence of arrhythmic events was estimated with the Kaplan-Meier method using the log-rank test. Cox proportional hazards regression was used to estimate hazard ratios (HRs) with their 95% confidence intervals (CIs).

RESULTS

Of the 1699 ICD patients, 77 patients (4.5%) had IAD. Incidence of inappropriate shock was similar in both patients with (3.2% at 24 months) and without (3.8% at 24 months) IAD (HR: 0.80, CI: 0.19-3.30, p = 0.76). In a multivariable analysis IAD was not significantly associated with reduced mortality (HR: 0.64, CI: 0.08-4.80, p = 0.66). The rates of complications were numerically lower in patients with IAD vs without (8.8% vs 9.6% at 24 months respectively), but not statistically significant (HR: 0.83, CI: 0.20-3.38, p = 0.79).

CONCLUSIONS

IAD patients showed a very low annual rate of inappropriate therapy. This suggests that newer algorithms, such as the SST algorithm, are equally good at identifying and treating life-threatening arrhythmias in patients regardless of whether they have IAD.

Outcome by Sex in Patients With Long QT Syndrome With an Implantable Cardioverter Defibrillator

Background

Sex differences in outcome have been reported in patients with congenital long QT syndrome. We aimed to report on the incidence of time‐dependent life‐threatening events in male and female patients with long QT syndrome with an implantable cardioverter defibrillator (ICD).

Methods and Results

A total of 60 patients with long QT syndrome received an ICD for primary or secondary prevention indications. Life‐threatening events were evaluated from the date of ICD implant and included ICD shocks for ventricular tachycardia, ventricular fibrillation, or death. ICDs were implanted in 219 women (mean age 38±13 years), 46 girls (12±5 years), 55 men (43±17 years), and 40 boys (11±4 years). Mean follow‐up post‐ICD implantation was 14±6 years for females and 12±6 years for males. At 15 years of follow‐up, the cumulative probability of life‐threatening events was 27% in females and 34% in males (log‐rank P=0.26 for the overall difference). In the multivariable Cox model, sex was not associated with significant differences in risk first appropriate ICD shock (hazard ratio, 0.83 female versus male; 95% CI, 0.52–1.34; P=0.47). Results were similar when stratified by age and by genotype: long QT syndrome type 1 (LQT1), long QT syndrome type 2 (LQT2), and long QT syndrome type 3 (LQT3). Incidence of inappropriate ICD shocks was higher in males versus females (4.2 versus 2.7 episodes per 100 patient‐years; P=0.018), predominantly attributed to atrial fibrillation. The first shock did not terminate ventricular tachycardia/ventricular fibrillation in 48% of females and 62% of males (P=0.25).

Conclusions

In patients with long QT syndrome with an ICD, the risk and rate of life‐threatening events did not significantly differ between males and females regardless of ICD indications or genotype. In a substantial proportion of patients with long QT syndrome, first shock did not terminate ventricular tachycardia/ventricular fibrillation.