Why is the clinical response to cardiac resynchronization better in LBBB patients?

AIMS: The improved clinical response in patients with left bundle branch block (LBBB) over LBBB-free patients treated with cardiac resynchronization therapy with a defibrillator (CRT-D) is commonly attributed to an LBBB abnormality. We aimed to find an alternative explanation. METHODS AND RESULTS: We analysed an immediate effect of selecting the LBBB group of patients in a cohort of 63 non-ischaemic cardiomyopathy (non-ICM) and 83 ischaemic cardiomyopathy (ICM) patients treated with CRT-D; 75% of non-ICM and 51% of ICM patients had an LBBB abnormality on the electrocardiogram, with a significant difference (P = 0.0032 by χ2 ). As a result of this difference, the proportion of non-ICM patients increased from 43% in the primary cohort to 53% in LBBB selection and decreased to 28% in non-LBBB group. By nonparametric survival analysis, the hazard ratio in non-ICM patients in the LBBB selection decreased from 0.48 (P = 0.0488) to 0.36 (P = 0.0251) and increased in the non-LBBB group to 0.75 (P = 0.6496). Any comparison of LBBB and non-LBBB groups must compare sets with a significantly altered proportion of patients of different aetiologies. Most publications on LBBB patients are erroneous because they compare LBBB with non-LBBB groups, not taking into account that the groups have been substantially changed by the selection process. CONCLUSIONS: The declared outcome of the LBBB groups reflects inevitably the survival outcome of their non-ICM patients and not the intended outcome of patients with LBBB. CRT-D in patients with different aetiologies of cardiomyopathy calls for separate evaluation.

The OPTI-MIND study: a prospective, observational study of pacemaker patients according to pacing modality and primary indications.

AIMS: The OPTI-MIND study aims to collect 2-year clinical outcomes of pacemaker patients in real-world clinical practice, overall and according to patient characteristics and pacemaker settings. METHODS AND RESULTS: The present analysis of the OPTI-MIND study describes the programmed device settings after discharge from the pacemaker implant. The objective was to determine whether these settings fit recent guidelines for device-programmed physiological pacing based on the preservation of atrioventricular synchrony, avoiding unnecessary pacing, ensuring rate increase during exercise or preventing neurally mediated symptoms. A total of 1740 patients were enroled at 68 centres worldwide. Baseline patient characteristics and device programming settings are available in 1674 of 1740 patients (96%). Guidelines to ensure physiological pacing were followed in 41% of patients: in patients with sinus node disease (SND), and without atrioventricular block (AVB), device programming could have led to unnecessary right ventricular pacing in 38% of patients. In SND patients with chronotropic incompetence, assisted rate increase during exercise was not programmed in 42% of patients. In 11% of patients with AVB, atrioventricular (AV) synchrony was not pursued; the main drivers being advanced age and history of atrial fibrillation. Patients with both SND and AVB were generally programmed physiologically (87%). CONCLUSION: The present analysis showed that frequent deviations occurred when comparing the device settings at discharge from the pacemaker implant in clinical practice to the available guidelines on pacing mode selection. Analysis of 2-year outcomes in the OPTI-MIND study will provide an insight into whether specific physiological settings could improve the quality of pacing with a positive effect on patient outcome.

Thoracoscopic left ventricular lead implantation.

OBJECTIVE: Cardiac resynchronization therapy is a therapeutic option in patients with chronic heart failure. Epicardial lead implantation for biventricular pacing is usually the method of second choice after failed coronary sinus cannulation. The present study describes an initial experience with minimally invasive surgical lead implantation using thoracoscopy. METHODS: Since August 2008, a total of 17 patients (mean age 69.6 + 11.1 years) with congestive heart failure, NYHA functional class 3.1 +/- 0.4, and depressed ejection function (24.8% +/- 5.7%) were referred for surgery because of failed left ventricular lead implantation through the coronary sinus. Under single-lung ventilation and video-assisted thoracoscopy, epimyocardial steroid-eluting screw-in leads were implanted on the left ventricular free wall. RESULTS: There were no in-hospital deaths or major co-morbidities. The mean skin-to-skin operating time was 115.9 +/- 32.1 min, and the post-operative average length of stay was 8.4 +/- 2.5 days. Intraoperative acute threshold capture of the left ventricular lead was 0.88 +/- 0.54 V/0.5 ms, and the value of lead impedance was 434.7 +/- 110.8 Omega. Extension to a small thoracotomy was necessary in 1 patient to stop epicardial vein bleeding. CONCLUSION: Minimally invasive left ventricular lead implantation is a safe procedure with excellent acute threshold capture.

Reduction of atrial fibrillation burden by atrial overdrive pacing: experience with an improved algorithm to reduce early recurrences of atrial fibrillation.

AIMS: Two independent studies have revealed a potential limitation of post-mode switch overdrive pacing (PMOP), which is its delayed start. METHODS AND RESULTS: We conducted a prospective, randomized, single blind, crossover design study (the post-long pause overdrive pacing study) to test the efficacy of an improved version of PMOP (PMOP(enhanced)). A total of 45 patients were enrolled, of whom 41 were analysed. The median number of atrial tachycardia/atrial fibrillation (AT/AF) episodes per day (1.38 vs. 1.19), the median number of early recurrences of atrial fibrillation (ERAF) per day (0.56 vs. 0.51), and the median AT/AF burden (time per day spent in AT/AF) (2.47 vs. 2.51 h) were not significantly different during the control and active study periods. Based on the median number of episodes per week recorded 90 days prior to enrollment, the patients were stratified by the median and then split into two groups, Group A (lower 2-Quartiles) and Group B (upper 2-Quartiles). The median AT/AF burden was significantly lower in Group B during the active study period (3.71 vs. 1.71 h, P = 0.02).The median number of AT/AF episodes per day and the median number of ERAF per day in Group B showed a trend towards reduction when the algorithm was turned on (3.79 vs. 2.44 and 2.77 vs. 1.86, respectively). In contrast, in Group A we did not demonstrate any difference in AT/AF frequency, ERAF frequency, or burden. CONCLUSION: The main finding of this study is that temporary overdrive pacing at 90 bpm for 10 min starting just prior to device-classified AT/AF termination does not show a positive effect on the overall study population. However, when enabled in patients who suffer from a high percentage of ERAF, a significant reduction in the AT/AF burden could be demonstrated. Based on these findings, further prospective studies on a more targeted patient population are needed to confirm our results.

Reduction of atrial tachyarrhythmia episodes during the overdrive pacing period using the post-mode switch overdrive pacing (PMOP) algorithm.

BACKGROUND: Early recurrences within 10 minutes after termination of an atrial tachyarrhythmia, such as atrial tachycardia (AT), atrial flutter, or atrial fibrillation (AF) episodes, account for a large part of paroxysmal AT/AF episodes. It is unclear whether these arrhythmias can be suppressed by overdrive pacing. OBJECTIVE: We set out to prove that overdrive pacing is effective in preventing early recurrences of AT/AF. METHODS: This AT500 (DDDRP device, Bakken Research Center Medtronic, Maastricht, The Netherlands) post-mode switch overdrive pacing (PMOP) study is a randomized controlled trial designed to test the efficacy of overdrive pacing on the suppression of early recurring AT/AF episodes. With the PMOP feature, overdrive pacing is activated 12 ventricular beats after device-confirmed termination of an AT/AF episode with a programmed duration and rate. If at least four episodes of 1 minute in duration occurred within the run-in period of 1 month, patients were randomized to one of the three settings (PMOP off and PMOP 10 minutes at 90 bpm or 120 bpm) for 2 months. At 2 and 4 months, patients were crossed over to another arm. At 6 months, all patients were programmed with PMOP on at 90 bpm for 30 minutes. RESULTS: We enrolled 122 and randomized 50 patients. Sixty percent of all stored AT/AF episodes occurred within 10 minutes after a previous episode; 31% occurred after device-determined termination and before the device reached the overdrive rate (17-27 ventricular beats after termination), and 29% of the episodes occurred while the device was pacing at the programmed overdrive rate. Thirty-seven percent of the average percentage of episodes during the overdrive period was prevented by the randomized settings of PMOP 90 bpm/10 min (P = .01, paired t-test, n = 39) and 120 bpm/10 min (P = .03, n = 35). In addition, for the nonrandomized setting of PMOP 90 bpm/30 min, the average number of episodes during the overdrive period was significantly smaller than the percentage of episodes occurring during the corresponding off period of 30 minutes (P = .05, n = 33). No significant differences in burden and episodes were found between the PMOP settings and the corresponding off periods. CONCLUSIONS: This is the first randomized controlled clinical trial to prove that overdrive pacing is effective in preventing early recurrences of AT/AF. However, shortcomings of the PMOP algorithm, such as late activation, need further improvement.