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Background: Early guidance recommended a bolus of intravenous heparin at the beginning of leadless pacemaker (LP) implantation procedures. However, due to concern about bleeding complications, more recent practice has tended toward omitting the bolus and only running a continuous heparin infusion through the introducer sheath. The impact of omitting the heparin bolus on procedural outcomes is not clear., Methods: We reviewed all Medtronic Micra LP implants at our institution from 9/2014 to 9/2022. The decision to bolus with heparin was at operator discretion., Results: Among 621 LP implants, 326 received an intravenous heparin bolus, 243 did not, and 52 patients were excluded because heparin bolus status could not be confirmed. There was a trend toward more frequent omission of the heparin bolus with more recent implants. Median follow-up after LP implant was 14.3 (interquartile range [IQR]: 8.4-27.9) months. There was no difference between heparin bolus and no bolus groups in the number of device deployments/recaptures (1.42 ± 0.81 vs. 1.31 ± 0.66, p = .15). Implant-related adverse events were also similar between heparin bolus and no bolus groups: access-site hematoma requiring intervention (7 vs. 5, p = .99), pseudoaneurysm (1 vs. 1, p = .99), cardiac perforation (1 vs. 1, p = .99), intraprocedural device thrombus formation (2 vs. 4, p = .41), 30-day rehospitalization (21 vs. 15, p = .98), and 30-day all-cause mortality (16 vs. 14, p = .70). There was one additional nonfatal cardiac perforation in a patient who was excluded due to unknown heparin bolus status. Regarding device electrical parameters between heparin bolus and no bolus groups, there were no significant differences at the time of implant: pacing capture threshold 0.5 ± 0.4 vs. 0.5 ± 0.3, p = .10; pacing impedance 739.9 ± 226.4 vs. 719.1 ± 215.4, p = .52; R wave sensing 11.7 ± 5.7 vs. 12.0 ± 5.4, p = .34). Long-term device performance was also similar between groups., Conclusion: Omission of the systemic heparin bolus at the time of LP implantation appears safe in appropriately selected patients. Heparin bolus may still be considered in long cases requiring multiple device deployments or in patients at high risk for thrombotic complications., (© 2024 Wiley Periodicals LLC.)

Pacing of the RV and LV is a promising technique for treating patients with dilated cardiomyopathy and bundle branch block. The salutary effects of biventricular pacing may be due to resynchronization of LV activation. Currently, available biventricular pacemakers and implanted defibrillators produce simultaneous ventricular output pulses. The purpose of the current study was to assess the effects of variation in the timing of RV and LV activation, using the paced QRS duration as a marker of resynchronization. Twenty-six patients undergoing transvenous biventricular pacemaker implantation were studied. After stable lead positions were achieved, activation of the LV and RV was varied over a range of +/- 50 ms and the QRS duration measured on a 12-lead ECG. Only 6 (23%) of the 26 patients had maximal shortening of the paced QRS with simultaneous activation of the LV and RV. The shortest paced QRS duration was most often produced by an LV to RV interval of -30 ms (LV activation preceding RV activation). Optimization of LV to RV interval resulted in an additional 13% shortening of the paced QRS compared to simultaneous activation (P < 0.0001). Patients with leads located on the lateral or anterolateral walls of the LV were more likely to benefit from preexcitation of the LV than did patients with leads in the posterior position. Results of this study suggest that the ability to program the LV to RV interval may be useful to optimize the benefit of biventricular pacing.

Pacemaker dependent patients exhibit interventricular conduction delay due to right ventricular lead placement. The addition of a transvenous coronary sinus lead for biventricular pacing has been shown to be effective. Venous stenosis and thrombosis postpacemaker implantation can occur in up to 35% of patients. This report describes a patient with a preexisting left-sided dual chamber pacemaker and chronic left subclavian vein occlusion that was upgraded to a biventricular system byplacing a coronary sinus lead and single chamber ventricular triggered pacemaker on the opposite side.

This study compares LV performance during high right ventricular septal (RVS) and apical (RVA) pacing in patients with LV dysfunction who underwent His-bundle ablation for chronic AF. We inserted a passive fixation pacing electrode into the RVA and an active fixation electrode in the RVS. A dual chamber, rate responsive pulse generator stimulated the RVA through the ventricular port and the RVS via the atrial port. Patients were randomized to initial RVA (VVIR) or RVS (AAIR) pacing for 2 months. The pacing site was reversed during the next 2 months. At the 2 and 4 month follow-up visit, each patient underwent a transthoracic echocardiographical study and a rest/exercise first pass radionuclide ventriculogram. We studied nine men and three women (mean age of 68 +/- 7 years) with congestive heart failure functional Class (NYHA Classification): I (3 patients), II (7 patients), and III (2 patients). The QRS duration was shorter during RVS stimulation (158 +/- 10 vs 170 +/- 11 ms, P < 0.001). Chronic capture threshold and lead impedance did not significantly differ. LV fractional shortening improved during RVS pacing (0.31 +/- 0.05 vs 0.26 +/- 0.07, P < 0.01). RVS activation increased the resting first pass LV ejection fraction (0.51 +/- 0.14 vs 0.43 +/- 0.10, P < 0.01). No significant difference was observed during RVS and RVA pacing in the exercise time (5.6 +/- 3.2 vs 5.4 +/- 3.1, P = 0.6) or the exercise first pass LV ejection fraction (0.58 +/- 0.15 vs 0.55 +/- 0.16, P = 0.2). The relative changes in QRS duration and LV ejection fraction at both pacing sites showed a significant correlation (P < 0.01). We conclude that RVS pacing produces shorter QRS duration and better chronic LV function than RVA pacing in patients with mild to moderate LV dysfunction and chronic AF after His-bundle ablation.