Programmed deep septal stimulation: A novel maneuver for the diagnosis of left bundle branch capture during permanent pacing.

INTRODUCTION: Permanent deep septal stimulation with capture of the left bundle branch (LBB) enables maintenance/restoration of the physiological activation of the left ventricle. However, it is almost always accompanied by the simultaneous engagement of the local septal myocardium, resulting in a fused (nonselective) QRS complex, therefore, confirmation of LBB capture remains difficult. METHODS: We hypothesized that programmed extrastimulus technique can differentiate nonselective LBB capture from myocardial-only capture as the effective refractory period (ERP) of the myocardium is different from the ERP of the LBB. Consecutive patients undergoing pacemaker implantation underwent programmed stimulation delivered from the lead implanted in a deep septal position. Responses to programmed stimulation were categorized on the basis of sudden change in the QRS morphology of the extrastimuli, observed when ERP of LBB or myocardium was encroached upon, as: "myocardial," "selective LBB," or nondiagnostic (unequivocal change of QRS morphology). RESULTS: Programmed deep septal stimulation was performed 269 times in 143 patients; in every patient with the use of a basic drive train of 600 milliseconds and in 126 patients also during intrinsic rhythm. The average septal-myocardial refractory period was shorter than the LBB refractory period: 263.0 ± 34.4 vs 318.0 ± 37.4 milliseconds. Responses diagnostic for LBB capture ("myocardial" or "selective LBB") were observed in 114 (79.7%) of patients. CONCLUSIONS: A novel maneuver for the confirmation of LBB capture during deep septal stimulation was developed and found to enable definitive diagnosis by visualization of both components of the paced QRS complex: selective paced LBB QRS and myocardial-only paced QRS.

His bundle has a shorter chronaxie than does the adjacent ventricular myocardium: Implications for pacemaker programming.

BACKGROUND: Strength-duration curves for permanent His bundle (HB) pacing are potentially important for pacemaker programming. OBJECTIVES: We aimed to calculate strength-duration curves and chronaxies of the HB and of the adjacent right ventricular (RV) working myocardium and to analyze zones of selective HB capture and battery current drain when pacing at different pulse durations (PDs). METHODS: Consecutive patients with permanent HB pacing were studied. The RV and HB capture thresholds were assessed at several PDs. Battery current drain and zones of selective HB capture at PDs of 0.1, 0.2, 0.4, and 1.0 ms were determined. RESULTS: In the whole group (N = 127), the HB chronaxie was shorter than the RV chronaxie. This difference was driven by patients with selective HB pacing (HB chronaxie 0.47 ms vs RV chronaxie 0.79 ms). The strength-duration curve for the HB had a lower rheobase and its steep portion started at shorter PDs, thus creating wider distance-zone of programmable selective HB pacing-between the HB and RV strength-duration curves at shorter PDs. The battery current drain was lower with pacing at PDs of 0.1-0.4 ms vs 1.0 ms. Chronaxie-adjusted PDs offered the lowest current drain. CONCLUSION: For the first time, the strength-duration curves for permanent selective and nonselective HB pacing were determined. Selective HB capture and battery longevity can be promoted by shorter PDs (0.2 ms). Longer PDs (1.0 ms) offer greater safety margin for RV capture and may be preferable if simultaneous RV capture during HB pacing is desired.

Programmed His Bundle Pacing: A Novel Maneuver for the Diagnosis of His Bundle Capture.

BACKGROUND: During permanent nonselective His bundle (ns-HB) pacing, it is crucial to confirm HB capture/exclude that only right ventricle (RV) myocardial septal pacing is present. Because the effective refractory period (ERP) of the working myocardium is different than the ERP of the HB, we hypothesized that it should be possible to differentiate ns-HB capture from RV myocardial capture using programmed extrastimulus technique. METHODS: In consecutive patients during HB pacemaker implantation, programmed HB pacing was delivered from the screwed-in HB pacing lead. Premature beats were introduced at 10-ms steps during intrinsic rhythm and also after a drive train of 600 ms. The longest coupling interval that resulted in an abrupt change of QRS morphology was considered equal to ERP of HB or RV myocardium. RESULTS: Programmed HB pacing was performed from 50 different sites in 32 patients. In 34 of 36 cases of ns-HB pacing, the RV myocardial ERP was shorter than HB ERP (271.8±38 versus 353.0±30 ms; P<0.0001). Programmed HB pacing using a drive train resulted in a typical abrupt change of paced QRS morphology: from ns-HB to RV myocardial QRS (34 of 36 cases) or to selective HB QRS (2 of 36 cases). Programmed HB pacing delivered during native conduction resulted in obtaining selective HB QRS in 20 of 34 and RV myocardial QRS in 14 of 34 of the ns-HB cases. In RV myocardial-only pacing cases (false ns-HB pacing, n=14), such responses were not observed-the QRS morphology remained stable. Therefore, the programmed HB pacing correctly diagnosed all ns-HB cases and all RV myocardial pacing cases. CONCLUSIONS: A novel maneuver for the diagnosis of HB capture, based on the differences in ERP between HB and myocardium, was formulated, assessed, and found as diagnostically valuable. This method is unique in enabling to visualize selective HB QRS in patients with otherwise obligatory ns-HB pacing (RV myocardial capture threshold

Cardiac resynchronization therapy-induced acute shortening of QRS duration predicts long-term mortality only in patients with left bundle branch block.

AIMS: QRS narrowing with initiation of biventricular pacing might be an acute electrocardiographic indicator of correction of left bundle branch block (LBBB)-induced depolarization delay and asynchrony. However, its impact on prognosis remains controversial, especially in non-LBBB patients. Our goal was to evaluate the impact of QRS narrowing on long-term mortality and morbidity in a large cohort of patients undergoing cardiac resynchronization therapy (CRT) with different pre-implantation QRS types: LBBB, non-LBBB, and permanent right ventricular pacing. METHODS AND RESULTS: This study included consecutive patients who underwent CRT device implantation. Study endpoints: death from any cause or urgent heart transplantation and death from any cause/urgent heart transplantation or hospital admission for heart failure. All pre- and post-implantation electrocardiograms were analysed using digital callipers, high-amplitude augmentation, 100 mm/s paper speed, and global QRS duration measurement method. A total of 552 CRT patients entered the survival analysis. During the 9 years observation period, 232 (42.0%) and 292 (52.9%) patients met primary and secondary endpoints, respectively. QRS narrowing predicted survival in the Kaplan-Meier analysis only in patients with LBBB. Multivariate Cox regression model showed that QRS narrowing was the major determinant of both study endpoints, with hazard ratios of 0.46 and 0.43, respectively. There was a strong relationship between mortality risk and shortening/widening of the QRS, albeit only in the LBBB group. Patients with non-LBBB morphologies had unfavourable prognosis similar to that in LBBB patients without QRS narrowing. CONCLUSION: Acute QRS narrowing in patients with LBBB might be a desirable endpoint of CRT device implantation.

Intermittent preexcitation indicates "a low-risk" accessory pathway: Time for a paradigm shift?

We report three patients with intermittent loss of the preexcitation pattern in the ECG that had undergone an electrophysiological study. Despite apparently poorly conducting accessory pathway (AP), in each case a fast anterograde conduction, either during spontaneous atrial fibrillation or during incremental atrial pacing (on isoproterenol) was documented; shortest preexcited RR intervals of 200-240 ms were observed. We review the literature and conclude that intermittent preexcitation observed on resting 12-lead ECG lacks sufficient specificity for the diagnosis of an AP with long refractory period and cannot be considered a substitute for electrophysiological study in patients with this electrocardiographical phenomenon.

[Dynamic changes of repolarization pattern associated with deep breathing and exercise in a young athlete: the sign "athletes heart" or concealed heart disease?]. / Dynamiczne zmiany okresu repolaryzacjizwiazane z oddychaniem i wysilkiemu mlodego sportowca: objaw "serca sportowca"czy utajona choroba serca?

We described ECG of a 22-year-old healthy man, professional basketball player, who has been training since he was 14. Physical examination was normal. In ECG the following abnormalities of repolarisation were observed: biphasic, positive/negative T waves in leads V3-V6. This changes normalised during deep breathing test. The echocardiogram revealed normal size of the heart's chambers, left ventricular walls hypertrophy - septum and posterior wall: 14 mm, normal mitral inflow - E/A = 1.1, normal ejection fraction (68%). The exercise test (ExT, 20 METS) was without symptoms. During ExT normalisation of repolarisation abnormalities was observed. From 6(th) minute of the recovery phase the repolarisation abnormalities were observed again. In unselected population of young athletes abnormal ECG is observed in 4.8-11.8% of athletes. Negative T waves in precordial leads are observed 2.3% of the young athletes and in 2.7% young, professional athletes. The repolarisation abnormalities described in our patient belong to electrocardiographic spectrum of the early repolarisation pattern mainly seen in black, young athletes.

Transvenous phrenic nerve stimulation for the treatment of central sleep apnoea in heart failure.

AIMS: Periodic breathing with central sleep apnoea (CSA) is common in heart failure patients and is associated with poor quality of life and increased risk of morbidity and mortality. We conducted a prospective, non-randomized, acute study to determine the feasibility of using unilateral transvenous phrenic nerve stimulation for the treatment of CSA in heart failure patients. METHODS AND RESULTS: Thirty-one patients from six centres underwent attempted transvenous lead placement. Of these, 16 qualified to undergo two successive nights of polysomnography-one night with and one night without phrenic nerve stimulation. Comparisons were made between the two nights using the following indices: apnoea-hypopnoea index (AHI), central apnoea index (CAI), obstructive apnoea index (OAI), hypopnoea index, arousal index, and 4% oxygen desaturation index (ODI4%). Patients underwent phrenic nerve stimulation from either the right brachiocephalic vein (n = 8) or the left brachiocephalic or pericardiophrenic vein (n = 8). Therapy period was (mean ± SD) 251 ± 71 min. Stimulation resulted in significant improvement in the AHI [median (inter-quartile range); 45 (39-59) vs. 23 (12-27) events/h, P = 0.002], CAI [27 (11-38) vs. 1 (0-5) events/h, P≤ 0.001], arousal index [32 (20-42) vs. 12 (9-27) events/h, P = 0.001], and ODI4% [31 (22-36) vs. 14 (7-20) events/h, P = 0.002]. No significant changes occurred in the OAI or hypopnoea index. Two adverse events occurred (lead thrombus and episode of ventricular tachycardia), though neither was directly related to phrenic nerve stimulation therapy. CONCLUSION: Unilateral transvenous phrenic nerve stimulation significantly reduces episodes of CSA and restores a more natural breathing pattern in patients with heart failure. This approach may represent a novel therapy for CSA and warrants further study.