A Comparison of VVIR and DDDR Pacing Following Cardiac Transplantation

We compared the clinical course of patients paced in VVIR versus DDDR mode to determine the most appropriate method of pacing following cardiac transplantation. Pacemaker implantation was required in 9 of 90 orthotopic cardiac transplants (10%). Indications included sinus bradycardia or sinus arrest (8 patients) and AV node dysfunction (1 patient). VVIR pacemakers were implanted in four patients and DDDR in five patients. DDDR patients : The mean P wave was 1.7 mV and the mean atrial stimulation threshold was 0.8 V (at 0.5 msec). During follow-up of 20 months, two atrial lead complications developed (29% of leads in 33% of patients). No lead complications were directly related to endomyocardial biopsy. VVIR patients : All four patients developed VA conduction with mean VA time 180 msec (160–240 msec). Two patients developed pacemaker syndrome. Conclusions : VA conduction and pacemaker syndrome may develop in cardiac transplant recipients paced in the VVIR mode. Dual chamber pacing is technically feasible and preferable following cardiac transplantation.     

Effect of Therapeutic INR on Activated Clotting Times,Heparin Dosage,and Bleeding Risk During Ablation of Atrial Fibrillation

Effect of INR on Anticoagulation During Ablation of Atrial Fibrillation . Background: Ablation of atrial fibrillation (AF) with international normalized ratio (INR) ≥ 2.0 is safe and may reduce thromboembolic complications. Heparin is administered during the procedure, but the effect of elevated INR on heparin requirements and target activation clotting times (ACT) ≥ 350 seconds during ablation is unknown. Objectives: To study the effect of INR on intraprocedural anticoagulation during ablation of AF. Methods: We retrospectively studied 427 consecutive patients over an 18‐month period when we were transitioning to continuation of warfarin for AF ablation. Baseline INR, procedural ACT measurements, heparin doses and major complications were analyzed according to Group 1 with INR < 2.0 (n = 246) and Group 2 with INR ≥ 2.0 (n = 181). Results: In Group 1, the mean INR was lower (1.3 ± 0.3 s vs 2.4 ± 0.3; P < 0.001), and the mean heparin dose was greater (106.82 ± 40.01 vs 77.03 ± 18.5 U/kg; P < 0.001). A single heparin bolus achieved ACT ≥ 350 seconds throughout the procedure in 51 patients (20.7%) in Group 1 compared to 108 patients (59.7%) in Group 2 (P < 0.01). Mean ACT values were higher in Group 2. Symptomatic pericardial effusions were similar (2.4% in Group 1 and 2.2% in Group 2). There were 3 thromboembolic cerebrovascular events in Group 1 and none in Group 2. Femoral hematomas occurred more frequently in Group 1 (8.1%) than in Group 2 (3.3%) (P = 0.007). Conclusions: AF ablation with INR ≥ 2.0 provides a consistent anticoagulant milieu during the procedure, with lower heparin requirements that are important to anticipate. (J Cardiovasc Electrophysiol, Vol. 22, pp. 248‐254, March 2011)     

The relationship of sweat gland count to electrodermal activity

This study assessed whether greater skin conductance activity at the distal versus medial site (Scerbo, Freedman, Raine, Dawson, & Venables, 1992) is attributable to a greater number of active (open) sweat glands at the distal site. The number of sweat glands was measured using the Palmar Sweat Index (PSI). Twenty-four subjects were exposed to 10 auditory stimuli. Electrodes were placed on the fore and middle fingers of each hand, using distal sites on one hand and medial sites on the other. The PSI was measured at the medial and distal phalanges adjacent to the electrode placement sites. The distal site contained more open and total sweat glands. Open gland count had the strongest correlations with skin conductance. Multivariate analyses of covariance revealed that site effects for nonspecific and orienting response frequency and trials to habituation were associated with site differences in open glands. Skin conductance measures and the PSI reveal greater electrodermal activity at the distal site. In addition, the number of open glands may be a useful measure related to electrodermal response frequency when polygraph measurement is unavailable.     

Long-Term Performance of the Attain Model 4193 Left Ventricular Lead

Background: Cardiac resynchronization therapy (CRT) has proven to be a valuable therapy addition for patients with drug-refractory heart failure and a ventricular conduction delay. Delivery of CRT is dependent upon the successful implantation and chronic performance of a left ventricular (LV) pacing lead. This study assessed the long-term electrical performance and safety of a steroid-eluting, transvenous, over-the-wire, cardiac vein pacing lead.
Methods: The Attain Model 4193 LV lead (Medtronic, Inc, Minneapolis MN, USA) was successfully implanted in 1,070 patients with 286 patients completing 3 years of follow-up. Clinical data were collected at pre-implant, implant, and at 6-month intervals for 3 years.
Results: Over 3 years, the mean chronic pacing threshold ranged from 1.9 V to 2.1 V, the mean R-wave sensing amplitudes ranged between 13.6 mV and 15.0 mV, and the mean pacing impedance ranged between 562 ohms and 590 ohms. Additionally, the observed freedom from first post-implant LV-lead-related complications was 90.4%. Of 1,070 total patients, 82 experienced 89 LV-lead-related adverse events requiring invasive interventions or resulting in the termination of the CRT therapy. The LV lead was repositioned in 31 patients, replaced in 21 patients, and explanted/capped in four patients. There were no deaths related to the LV lead during implantation or during the follow-up period.
Conclusions: The data suggest that the 4193 LV lead is safe and effective over time. The LV lead electrical measurements remained stable through follow-up, demonstrating reliable long-term performance within the recommended value range at 36 months and had an acceptable complication rate.     

A Comparative Study of Activity and Dual Sensor: Activity and Minute Ventilation Pacing Responses to Ascending and Descending Stairs

Previous studies with activity-based rate; adaptive pacemakers have shown a somewhat paradoxical response when comparing ascending stairs to descending stairs. The objective of this investigation was to measure dual-sensor rate response provided by activity and minute ventilation (MV) compared with activity alone, and with a control group, during ascending and descending stairs. For dual sensor mode, measured mean peak pacing rate with 72 (92) steps per minute was 111 ± 13 beats/min (124 ± 14 beats/min) ascending stairs and 81 ± 7 beats/mm (97 ± 13 beats/min) for descending. For activity mode alone, mean peak pacing rate was 90 ± 12 beats/min (108 ± 19 beats/min) ascending stairs and 97 ± 12 beats/min (123 ±17 beats/min) descending. The mean peak control group heart rate ascending stairs for a step rate of 72 (92J steps/min were 116 ± 11 beats/min (127 ±14 beats/min) ascending stairs and for descending 89 ± 12 beats/min (95 ± 11 beats/min). While for dual sensor controlled pacing there was a significant difference for ascending and descending stairs at both step rates, there was no difference between going upstairs and downstairs for activity mode alone. Rates with dual sensor did not significantly differ from respective rates of the control group. The mean correlation coefficient between MV and paced rate was 0.85. Pacing heart rates delivered by the dual sensor mode were appropriate for ascending and descending stairs. In contrast to activity mode alone, the peak heart rates for dual sensor mode are higher during ascending than during descending stairs.     

Inappropriate Sensing of Atrial Stimuli in Patients with Third-Generation Defibrillators and DDD Pacemakers

Although the problem of ICD sensing of paced ventricular stimuli has been resolved by incorporation of VVI pacing into current ICDs, many patients require separate DDD pacemakers. We report a problematic PM-ICD interaction: the inability to prevent sensing of paced atrial stimuli (atrial sensing) leading to double-counting in DDD-PM-requiring patients with transvenous (TV) ICDs with aggressive autogain sensing (CPI Ventak® PRxII or III). Four of eight patients receiving both transvenous DDD PMs and ICDs (CPI Endotak® lead, at the RV apex), had atrial sensing, leading to double counting, despite intraoperative testing of multiple atrial locations with an active fixation lead. Five patients had a PRxlI/III ICD, four with atrial sensing (80%), and three a PRx without atrial sensing. Patients with atrial sensing were not distinguished by any clinical or device related variable. In patients with atrial sensing (all with heart block), the PM was programmed to VDD mode. No patient has received inappropriate therapy or failed to sense VP in follow-up. In many patients with TV ICDs who require DDD pacing, no atrial position can be found without ICD sensing of atrial stimuli. While in patients with heart block this problem can be circumvented by programming to the VDD mode, in patients with sinus incompetence it may only be resolved by the combination ICD-DDD PM, currently in development.