Erika Taravelli

Vagal reflexes following an exercise stress test: A simple clinical tool for gene-specific risk stratification in the long QT syndrome

OBJECTIVES The study assessed whether heart rate (HR) reduction following an exercise stress test (ExStrT), an easily quantifiable marker of vagal reflexes, might identify high- and low-risk long QT syndrome (LQTS) type 1 (LQT1) patients. BACKGROUND Identification of LQTS patients more likely to be symptomatic remains elusive. We have previously shown that depressed baroreflex sensitivity, an established marker of reduced vagal reflexes, predicts low probability of symptoms among LQT1. METHODS We studied 169 LQTS genotype-positive patients < 50 years of age who performed an ExStrT with the same protocol, on and off β-blockers including 47 South African LQT1 patients all harboring the KCNQ1-A341V mutation and 122 Italian LQTS patients with impaired (I(Ks)-, 66 LQT1) or normal (I(Ks)+, 50 LQT2 and 6 LQT3) I(Ks) current. RESULTS Despite similar maximal HR and workload, by the first minute after cessation of exercise the symptomatic patients in both I(Ks)- groups had a greater HR reduction compared with the asymptomatic (19 ± 7 beats/min vs. 13 ± 5 beats/min and 27 ± 10 beats/min vs. 20 ± 8 beats/min, both p = 0.009). By contrast, there was no difference between the I(Ks)+ symptomatic and asymptomatic patients (23 ± 9 beats/min vs. 26 ± 9 beats/min, p = 0.47). LQT1 patients in the upper tertile for HR reduction had a higher risk of being symptomatic (odds ratio: 3.28, 95% confidence interval: 1.3 to 8.3, p = 0.012). CONCLUSIONS HR reduction following exercise identifies LQT1 patients at high or low arrhythmic risk, independently of β-blocker therapy, and contributes to risk stratification. Intense exercise training, which potentiates vagal reflexes, should probably be avoided by LQT1 patients.

A comprehensive electrocardiographic, molecular, and echocardiographic study of Brugada syndrome: Validation of the 2013 diagnostic criteria

BACKGROUND The debate on the diagnostic value of high intercostal spaces (ICSs) and of the number of diagnostic leads in Brugada syndrome (BrS) has been settled by a recent expert consensus statement. OBJECTIVE To test the validity, and the underlying anatomy, of the new electrocardiographic (ECG) diagnostic criteria using echocardiographic, molecular, and clinical evidence in 1 clinical study population with BrS. METHODS We analyzed 114 patients with BrS and with a spontaneous or drug-induced type 1 ECG pattern recorded in 1 or more right precordial leads in fourth, third, and second ICSs. The right ventricular outflow tract (RVOT) was localized by using echocardiography. All probands were screened on the SCN5A gene. RESULTS The percentage of mutation carriers (MCs) and the event rate were similar regardless of the diagnostic ICS (fourth vs high ICSs: MCs 23% vs 19%; event rate 22% vs 28%) and the number of diagnostic leads (1 vs ≥2: MCs 20% vs 22%; event rate 22% vs 27%). The concordance between RVOT anatomical location and the diagnostic ICSs was 86%. The percentage of the diagnostic ECG pattern recorded was significantly increased by the exploration of the ICSs showing RVOT by echocardiography (echocardiography-guided approach vs conventional approach 100% vs 43%; P < .001). CONCLUSION The high ICSs are not inferior to the standard fourth ICS for the ECG diagnosis of BrS, and the interindividual variability depends on the anatomical location of the RVOT as assessed by using echocardiography. This approach significantly increases diagnostic sensitivity without decreasing specificity and fully supports the recently published new diagnostic criteria.

High rate of subcutaneous implantable cardioverter-defibrillator sensing screening failure in patients with Brugada syndrome: a comparison with other inherited primary arrhythmia syndromes

Aims Subcutaneous implantable cardioverter-defibrillator (S-ICD) can avoid important complications associated with transvenous leads in patients with inherited primary arrhythmia syndromes, who do not need pacing therapy. Few data are available on the percentage of patients with inherited arrhythmia syndromes eligible for S-ICD implantation. Aim of this study was to analyse the eligibility for S-ICD in a series of patients with Brugada syndrome (BrS), and to compare it with patients with other channelopathies. Methods and results Patients presenting with BrS, long-QT syndrome (LQTS), early repolarization syndrome (ERS), and idiopathic ventricular fibrillation (IVF) were considered eligible for this study. ECG screening was performed by analysis of QRS complex and T wave morphology recorded in standing and supine position. Eligibility was defined when ≥1 sense vector was acceptable in both supine and standing position. A total of 100 patients (72 males; mean age: 46 ± 17 years) underwent S-ICD sensing screening. Sixty-one patients presented with BrS, 21 with LQTS, 14 with IVF, and 4 with ERS. Thirty-four patients with BrS (56%) presented with spontaneous type 1 ECG. In the other 27 patients (44%), type 1 ECG was unmasked by ajmaline. Overall, rate of screening failure was 13%. Patients with BrS had a higher rate of inappropriate morphology analysis as compared with other channelopathies (18% vs. 5%, P = 0.07) and had a lower number of suitable sensing vectors (49.6% vs. 84.7% vs. P < 0.001). Ajmaline challenge unmasked sensing failure in 14.8% of drug-induced BrS patients previously considered eligible. In all patients, the reason for sensing inappropriateness was due to the presence of high T wave voltages. Conclusion S-ICD screening failure occurs in up to 13% of patients with inherited primary arrhythmia syndromes. Patients with BrS present a higher rate of screening failure as compared with other cardiac channelopathies.

A randomized controlled trial of atrioventricular junction ablation and cardiac resynchronization therapy in patients with permanent atrial fibrillation and narrow QRS

Aims We tested the hypothesis that atrioventricular (AV) junction ablation in conjunction biventricular pacing [cardiac resynchronization (CRT)] pacing is superior to pharmacological rate-control therapy in reducing heart failure (HF) and hospitalization in patients with permanent atrial fibrillation (AF) and narrow QRS. Methods and results We randomly assigned 102 patients (mean age 72 ± 10 years) with severely symptomatic permanent AF (>6 months), narrow QRS (≤110 ms), and at least one hospitalization for HF in the previous year to AV junction ablation and CRT (plus defibrillator according to guidelines) or to pharmacological rate-control therapy (plus defibrillator according to guidelines). After a median follow-up of 16 months, the primary composite outcome of death due to HF, or hospitalization due to HF, or worsening HF had occurred in 10 patients (20%) in the Ablation+CRT arm and in 20 patients (38%) in the Drug arm [hazard ratio (HR) 0.38; 95% confidence interval (CI) 0.18-0.81; P = 0.013]. Significantly fewer patients in the Ablation+CRT arm died from any cause or underwent hospitalization for HF [6 (12%) vs. 17 (33%); HR 0.28; 95% CI 0.11-0.72; P = 0.008], or were hospitalized for HF [5 (10%) vs. 13 (25%); HR 0.30; 95% CI 0.11-0.78; P = 0.024]. In comparison with the Drug arm, Ablation+CRT patients showed a 36% decrease in the specific symptoms and physical limitations of AF at 1 year follow-up (P = 0.004). Conclusion Ablation+CRT was superior to pharmacological therapy in reducing HF and hospitalization and improving quality of life in elderly patients with permanent AF and narrow QRS. ClinicalTrials.gov Identifier NCT02137187 (May 2018, date last accessed).