Analysis of site-specific late potentials using a novel Holter signal-averaged electrocardiography in patients with Brugada syndrome.

BACKGROUND: The utility of late potentials on signal-averaged electrocardiography (SAECG) for risk stratification in patients with Brugada syndrome (BrS) remains controversial. Late potentials on conventional SAECG with Frank leads may be insufficiently sensitive to detect site-specific late potentials in right precordial leads. OBJECTIVE: The purpose of this study was to evaluate the utility of site-specific late potentials using a novel unipolar Holter-SAECG system for risk stratification in patients with BrS. METHODS: Consecutive symptomatic (n = 20) and asymptomatic (n = 21) patients with BrS who underwent investigation using conventional SAECG and a novel unipolar Holter-SAECG system were enrolled. We evaluated clinical characteristics and outcomes and compared late potentials on the 2 SAECGs between both groups and patients with and without cardiac events (CEs) (sudden cardiac death or sustained ventricular tachyarrhythmias) during the follow-up period. RESULTS: During mean follow-up of 76 months, 10 patients (24%) had CEs. There were no significant differences in late potentials on conventional SAECG between symptomatic and asymptomatic patients. On the Holter-SAECG system, RMS40 in lead V2 in the third intercostal space (3L-V2) at the nighttime was significantly lower in the symptomatic group than in the asymptomatic group (5.5 ± 0.8 µV and 8.2 ± 0.8 µV, respectively; P = .027). Univariate analysis of predictive values for CE showed that hazard ratios of daytime and nighttime RMS40 in lead 3L-V2 of <7.7 µV and <6.1 µV were 7.58 and 6.14, respectively. CONCLUSION: Site-specific late potentials in lead 3L-V2 measured using the novel Holter-SAECG system may be a useful marker for high-risk patients with BrS.

The unstable pacing thresholds of the leadless transcatheter pacemaker affected by body positions in subacute phase after implant.

BACKGROUND: If the threshold at implant of leadless transcatheter pacemakers (LTPs) is less than 2.0 V, pacing thresholds reportedly decrease significantly by 1 month and maintain an optimal value of less than 1.0 V by 6 months. CASE SUMMARY: We report a case series of two patients with unstable pacing thresholds of the LTPs in the subacute phase after implant. The first patient (77-year-old man) was implanted an LTP for sick sinus syndrome. At that time of implant, the pacing threshold was 0.9 V at 0.24 ms. At 1 week and 1 month later, the threshold had increased to more than 2.0 V at 0.24 ms. We investigated the trend data for the week and found variations in the threshold. The second patient (81-year-old man) was implanted an LTP for bradycardia and atrial fibrillation. The pacing threshold at implantation was 0.63 V at 0.24 ms. One week later, the threshold had increased in supine position and decreased in sitting position. The trend data for the week were fluctuating greatly. DISCUSSION: The pacing threshold may increase to more than 2.0 V with significant fluctuation on assessment at 1 week and 1 month after implantation in association with changes in body position, even though we confirmed a stable threshold at implant. If an increased threshold is observed, it is necessary to check the trend data and threshold in each body position.