Paced QT interval is a better predictor of mortality than the intrinsic QT interval: Long-term follow-up study

Delivery catheter system carries more physiological right ventricular septal pacing than stylet system

INTRODUCTION

The Mt. FUJI multicenter trial demonstrated that a delivery catheter system had a higher rate of successful right ventricular (RV) lead deployment on the RV septum (RVS) than a conventional stylet system. In this subanalysis of the Mt. FUJI trial, we assessed the differences in electrocardiogram (ECG) parameters during RV pacing between a delivery catheter system and a stylet system and their associations with the lead tip positions.

METHODS

Among 70 patients enrolled in the Mt FUJI trial, ECG parameters, RV lead tip positions, and lead depth inside the septum assessed by computed tomography were compared between the catheter group (n = 36) and stylet group (n = 34).

RESULTS

The paced QRS duration (QRS-d), corrected paced QT (QTc), and JT interval (JTc) were significantly shorter in the catheter group than in the stylet group (QRS-d: 130 ± 19 vs. 142 ± 15 ms, p = .004; QTc: 476 ± 25 vs. 514 ± 20 ms, p < .001; JTc: 347 ± 24 vs. 372 ± 17 ms, p < .001). This superiority of the catheter group was maintained in a subgroup analysis of patients with an RV lead tip position at the septum. The lead depth inside the septum was greater in the catheter group than in the stylet group, and there was a significant negative correlation between the paced QRS-d and the lead depth.

CONCLUSION

Using a delivery catheter system carries more physiological depolarization and repolarization during RVS pacing and deeper screw penetration in the septum in comparison to conventional stylet system. The lead depth could have a more impact on the ECG parameters rather than the type of pacing lead.

Left bundle branch potential predicts better electrical synchrony in bradycardia patients receiving left bundle branch pacing

Background

Left bundle branch pacing (LBBP) is a novel physiological pacing technology. We aim to explore the relation between LBB potential (LBB Po) and left ventricular (LV) electrical/mechanical synchrony in bradycardia patients without heart failure (HF) receiving LBBP.

Methods

A total of 62 patients undergoing LBBP were categorized by LBB Po: the LBB Po positive (+) group and the LBB Po negative (−) group. The perioperative electrocardiographic and echocardiography parameters related to cardiac synchrony were analyzed.

Results

There were 42 (67.74%) patients in the LBB Po (+) group and 20 patients in the LBB Po (−) group. Paced QRS duration (113.50 ± 17.65 ms vs. 123.40 ± 13.18 ms, P = 0.031) and stimulus left ventricular activation time (71.76 ± 3.53 ms vs. 74.45 ± 3.12 ms, P = 0.005) were shorter in the LBB Po (+) group than in the LBB Po (−) group. No significant differences in the LV mechanical synchrony (Ts-SD-12, 36.55 ± 19.76 vs. 39.95 ± 16.04, P = 0.505; PSD, 51.14 ± 17.69 vs. 45.65 ± 10.55, P = 0.205) between the two groups. There was not statistically difference in ventricular lead parameters measured intraoperative between the two groups. Compared with the LBB Po (−) group, the LBB Po (+) group showed a dramatically higher total procedure duration time (93.52 ± 9.18 min vs. 86.25 ± 10.54 min, p = 0.007) and fluoroscopy time for ventricle lead implantation (18.95 ± 3.43 min vs. 14.00 ± 3.16 min, p < 0.001).

Conclusions

The appearance of LBB Po may suggest better electrical synchrony during LBBP, but similar in LV mechanical synchrony. However, the total operation duration and fluoroscopy time of ventricular lead implantation in the LBB Po (+) group were longer. Therefore, it may be unnecessary to deliberately recognize the LBB Po when it is difficult to detect LBB Po and meet the LBBP criterion.

Changes of repolarization parameters after left bundle branch area pacing and the association with echocardiographic response in heart failure patients

Background: Left bundle branch area pacing (LBBAP) has become a safe and effective option for heart failure (HF) patients indicated for cardiac resynchronization therapy (CRT) and/or ventricular pacing, yet the response rate was only 70%. Repolarization parameters were demonstrated to be associated with cardiac mechanics and systolic function. This study aimed to investigate the effects of LBBAP on repolarization parameters and the potential association between those parameters and echocardiographic response.

Methods and results: A total of 59 HF patients undergoing successful LBBAP were consecutively included. QTc, Tpeak-Tend (TpTe), and TpTe/QTc were measured before and after the implantation. The results turned out that the dispersion of ventricular repolarization (DVR) improved after LBBAP among the total population. Although trends of repolarization parameters varied according to different QRS configurations at baseline, the post-implant parameters showed no significant difference between groups. The association between repolarization parameters and LBBAP response was then evaluated among patients with wide QRS. Multivariate analysis demonstrated that post-implant TpTe was the independent predictor of LBBAP response (p < 0.05). Receiver operating characteristic analysis indicated an area under the curve of 0.77 (95% CI, 0.60–0.93) with a cutoff value of 81.2 ms (p < 0.01). Patients with post-implant TpTe<81.2 ms had a significantly higher rate of echocardiographic response (93.3 vs. 44.4%, p < 0.01). Further subgroup analysis indicated that the predictive value of post-implant TpTe for LBBAP response was more significant in non-left bundle branch block (LBBB) patients than in LBBB patients.

Conclusion: LBBAP improved DVR significantly in HF patients. Post-implant TpTe was associated with the echocardiographic response after LBBAP among patients with wide QRS, especially for non-LBBB patients.

Left bundle branch area pacing is superior to right ventricular septum pacing concerning depolarization-repolarization reserve

INTRODUCTION

Left bundle branch area pacing (LBBAP) has recently been reported to be a new physiological pacing strategy with clinical feasibility and safety. The present study aims to investigate depolarization-repolarization measures including QT interval, QT dispersion (QTD), and T_peak-end interval (T_p T_e ) in this novel LBBAP strategy.

METHODS AND RESULTS

A total of 131 pacing-indicated patients were prospectively enrolled and randomized to the LBBAP group (n = 66) and right ventricular septum pacing (RVSP) group (n = 65). LBBAP was successfully achieved in 61 subjects with stable lead performance and comparable complications (ie, pocket hematoma, lead perforation, and dislodgement) compared with RVSP. Of the 61 patients with successful LBBAP, the mean LV peak activation time was 67.89 ± 6.80 ms, with the LBB potential mapped in 46 cases (75.4%). Electrocardiogram (ECG) indices were compared between these two groups before and after implantation. As a result, LBBAP yielded a narrower paced QRS duration (121.49 ± 9.87 ms vs 145.62 ± 8.89 ms; P < .001), shorter QT interval (434.16 ± 32.70 ms vs 462.66 ± 32.04 ms; P < .001), and QT_c interval (472.44 ± 33.30 ms vs 499.65 ± 31.35 ms; P < .001), lower QTD (40.10 ± 8.68 ms vs 46.11 ± 10.85 ms; P = .001), and QT_c D (43.57 ± 8.78 ms vs 49.86 ± 11.98 ms; P = .001), and shorter T_p T_e (96.59 ± 10.76 ms vs 103.77 ± 10.16 ms; P < .001) than RVSP. However, T_p T_e /QT ratio did not differ between these two groups (0.223 ± 0.026 vs 0.225 ± 0.022; P = .733). Furthermore, LBBAP displayed less increased QRS duration, QT_c interval, QTD, QT_c D, and a more shortened QT interval compared with RVSP (all P < .05).

CONCLUSION

LBBAP proves to be a feasible and safe pacing procedure with better depolarization-repolarization reserve, which may predict lower risk of ventricular arrhythmia and sudden cardiac death.

Comparison and Validation of Recommended QT Interval Correction Formulas for Predicting Cardiac Arrhythmias in Patients With Advanced Heart Failure and Cardiac Resynchronization Devices

QT interval prolongation is an important marker for the development of cardiac arrhythmias (CAs). Optimal methods to estimate QT/QTc intervals in patients with ventricular pacing (VP) and its correlation with CA have not been widely investigated. We aimed to validate the currently available formulas for QT determination during VP and to compare their abilities in predicting the occurrence of CA (atrial fibrillation [AF] and malignant ventricular arrhythmias [VAs] in patients with advanced heart failure and cardiac resynchronization therapy). Consecutive patients with advanced heart failure who underwent cardiac resynchronization therapy implantation between August 2001 and April 2015 were included in a retrospective study. Four proposed formulas for QT correction in VP rhythms were evaluated. One hundred eighty patients were enrolled. During 44 months of follow-up, 43 patients (37.7%) developed AF and 16 patients (8.9%) developed VA. There was no correlation between corrected QT increments and AF risk with any of the formulas for paced rhythms. Regarding VA, higher corrected QT values measured with Massachusetts' formula (QTcM) were found to have a higher risk of event (p = 0.036) (Beta = 1.012 [1.001 to 1.023]). Each 1 ms increase in QTc increased the probability of experiencing VA by 12‰. QTcM >444 was found to be a strong predictor of VA. In conclusion, there are significant differences in mean QTc interval measured by the currently advised formulas. QTc interval was not associated with AF in any of the formulas. Only the QTcM formula showed a significant stepwise increase in the risk of experiencing malignant VA.

Holter-monitored sudden cardiac arrest after atrioventricular junction ablation

We present a case of sudden cardiac arrest 7 hours after radiofrequency ablation of the atrioventricular junction for symptomatic permanent atrial fibrillation unresponsive to medical therapy. The Holter monitoring revealed a progressive increasing of QT interval after the procedure, highlighting the repolarization instability after acute changes in heart rates associated with modification of ventricular activation, leading to occurrence of short coupling interval ventricular extra beats and finally to a "torsade de pointes." This illustration underlines the need to program a relatively rapid ventricular rate first weeks after junction ablation, especially in case of rapid ventricular rate prior to the procedure, as well as the role of continuous ECG and QT interval monitoring during hospital stay.

QT interval variations and mortality risk: is there any relationship?

Abnormal prolongation and shortening of the electrocardiographic QT interval duration, which occur in the hereditary forms of long and short QT syndromes, are associated with an increased risk of ventricular arrhythmias and sudden cardiac death. Even within the normal range, these altered durations are associated with an increased mortality risk in the general population. While extreme prolongation or reduction of the QT interval predisposes patients to malignant ventricular arrhythmias and sudden cardiac death, the precise dose-response relationship between the QT interval and cardiovascular disease mortality is still unknown. This paper describes the need for more standardized methods for measuring and reporting the QT interval and the need for more precise assessments of the risk associated with QT interval variation.