Vijay S. Chauhan

Introduction: Patients on hemodialysis have an increased risk of sudden cardiac death and an increased cardiac arrhythmia burden due to large fluid and electrolyte shifts, especially during the long inter‐dialytic period. Arrhythmia burden may be decreased on home nocturnal hemodialysis due to prolonged fluid removal and clearance. This study examined the safety and feasibility of prolonged cardiac monitoring in patients who were converting from conventional hemodialysis (12 h) to home nocturnal hemodialysis (30+ h). Methods: Patients from a single center in Toronto, Ontario, Canada with a low cardiac risk profile, who were eligible to perform hemodialysis at home, were enrolled. Participants underwent the insertion of an implantable loop recorder and cardiac arrhythmia were monitored during conventional hemodialysis, and for 1 year after conversion to home nocturnal hemodialysis. Findings: Ten participants completed the study. The average ultrafiltration rate per session during conventional hemodialysis was 6.87 mL/h/kg, and the average cardiac ejection fraction was 52.6%. There were no adverse effects associated with implantable loop recorder implantation, usage, or removal. One participant recorded three sinus bradycardia and two sinus pause events during conventional hemodialysis that resolved after conversion to home nocturnal hemodialysis. All other participants did not experience any arrhythmic events before or after conversion to home nocturnal hemodialysis. Discussion: Our pilot study demonstrated a safe and feasible protocol for prolonged monitoring of cardiac arrhythmia in a stable population undergoing conversion from conventional to home nocturnal hemodialysis. Due to the small sample size, future work is required to delineate the full effect of home nocturnal hemodialysis on cardiac arrhythmia burden in patients with increased cardiac comorbidities.

BACKGROUND: The safety, yield, and prognosis of a type 1 procainamide-induced Brugada pattern are incompletely understood and may differ from those of other sodium channel blockers with greater potencies. METHODS: The safety of procainamide infusion and yield of a type 1 Brugada pattern were assessed according to indication in consecutive patients from the Canadian Hearts in Rhythm Organization registry. Outcomes were evaluated in patients with a standard or high-lead procainamide-induced Brugada pattern (without previous cardiac arrest) and compared with those with a spontaneous type 1 pattern. RESULTS: In 947 consecutive patients undergoing procainamide infusion for the diagnosis or exclusion of Brugada syndrome, 2 patients (0.2%) experienced asymptomatic ventricular arrhythmias related to procainamide, which resolved upon discontinuation of the infusion. The yield of a type 1 pattern was 7.2% in 390 patients with unexplained cardiac arrest, 22.2% in 135 patients with a family history of Brugada syndrome, and 6.9% in 116 patients with a family history of unexplained cardiac arrest or sudden death. Test yield was 46.6% in 189 patients with a non-specific type 2 or 3 Brugada pattern and 92% in those with an intermittent spontaneous type 1 pattern (ie, implied sensitivity of 92%). Estimated specificity was very high. In 137 patients with a procainamide-induced type 1 Brugada pattern (with no previous cardiac arrest) followed for a mean of 5.9±4.5 years, no patients met the primary composite arrhythmic end point (0%). In 105 spontaneous type 1 patients, one patient (1%) met the primary end point after receiving appropriate shocks for ventricular fibrillation. Thirteen percent had a primary prevention implantable cardioverter defibrillator implanted at baseline (one appropriate shock), with an additional 7% undergoing implantable cardioverter defibrillator implantation during follow-up, predominantly for syncope with a suspected arrhythmic mechanism. No patient who underwent implantable cardioverter defibrillator implantation during follow-up subsequently received appropriate therapy. CONCLUSIONS: Procainamide infusion is extremely safe for the diagnosis and exclusion of Brugada syndrome, with yield dependent on pretest probability and indication for testing. Estimated sensitivity and specificity appear to be high. Patients with an asymptomatic procainamide-induced type 1 Brugada pattern are at very low risk of malignant ventricular arrhythmias.

BACKGROUND: Activation recovery interval (ARI), extracted from unipolar electrograms, serves as a practical surrogate for repolarization during experimental studies in vivo. Far-field signal contamination and low spatial resolution obscure regional repolarization gradients and duration alternans detection using unipolar ARI. We hypothesized that the attenuation of far-field contamination with the principal component-referenced unipole will allow for a more accurate assessment of true local repolarization gradients and spatially assess action potential duration alternans. METHODS: Unipolar ARI and the novel method, Repol ^Loc , were validated for the detection of spatial and temporal repolarization changes using simultaneous optical and electrical mapping in a rabbit Langendorff model. Repolarization changes were created using global infusion of ibutilide or pinacidil, or topical application of lidocaine. Epicardial mapping was conducted in a porcine Langendorff model following the topical application of lidocaine to investigate the spatial resolution of each method. Generalized linear models of the two methods were used to compare with optical action potential duration (APD80). RESULTS: Following the infusion of antiarrhythmic drugs, the Repol ^Loc method (slope=0.90) had a slightly higher correlation to optical APD80 than the ARI method (slope=0.79). Following regional application of lidocaine, Repol ^Loc was better able to localize the site of drug administration with an average 26.12% reduction as compared with 18.66% reduction in unipolar ARI ( P =0.0046). Additionally, temporal repolarization alternans and restitution changes assessed by Repol ^Loc method tracked optical APD80 quantified time domain changes. CONCLUSIONS: Repol ^Loc has higher sensitivity to local spatiotemporal repolarization heterogeneities and alternans than traditional ARI. Although ARI only correlates with uniformly distributed changes in repolarization in the entire myocardium, Repol ^Loc also provided accurate regional gradient assessment and duration alternans of repolarization. These findings suggest ARI has significant far-field contamination and Repol ^Loc may provide a better clinical mapping tool for spatiotemporal repolarization gradient mapping.