Mechanism of decrease in the atrial potential after implantation of a single-lead VDD pacemaker: atrial histological changes after implantation of a VDD pacemaker lead in dogs

Pacemaker lead-related macroreentrant atrial tachycardia

Macroreentrant atrial circuits are frequently associated with scarring. Previous reports have shown the possible development of scar tissue that is adjacent to pacemaker (PM) leads. However, reports of PM lead-related reentrant tachycardia are scarce. We report the case of a 63-year-old woman who presented with macroreentrant atrial tachycardia (MAT), related to the atrial trajectory of an old single-lead ventricular PM, that was successfully treated with radiofrequency ablation after an conventional electrophysiological study ruled out isthmus-dependent atrial flutter and provided sufficient data to confirm this diagnosis.This report presents a case of MAT originating around the trajectory of a PM lead, probably because of scar tissue that developed adjacent to the lead. Experimental studies have already shown that interstitial atrial fibrosis may develop adjacent to a ventricular single-lead. This finding suggests that MAT develops in patients with this specific condition. Recognizing this condition is important for managing these arrhythmias and performing safe ablation with the preservation of PM lead integrity.

Outcomes of single‑lead VDD pacemakers in atrioventricular blocks: The OSCAR study

BACKGROUND

VDD pacemakers are regarded as a second choice in patients with atrio-ventricular blocks mainly due to the potential failure of atrial sensing, leading to a loss of atrio-ventricular synchrony. This single-centre study aimed to evaluate the prevalence of loss of atrial sensing and its potential determinants in patients with VDD pacemakers.

METHOD

142 patients with an implanted VDD device underwent long-term follow-up with clinical evaluation, electrocardiogram, device interrogation and echocardiogram.

RESULTS

Over a long follow-up period [median 110 (68-156) months], 17 patients (12%) in sinus rhythm presented loss of atrial sensing. This was most often intermittent, but three patients required a permanent switch to VVI mode. ECG showed higher prevalence of interatrial blocks (50% vs 26.6%, p = 0.057) and longer P wave duration (116 ± 19 vs 105 ± 15 ms, p = 0.019) in patients with loss of atrial sensing. Echocardiography revealed larger left atrial (LA) volumes (p < 0.05) in patients with loss of atrial sensing, and lower LA ejection fraction (0.40 vs 0.47, p = 0.0037) and expansion index (0.63 ± 0.26 vs 0.90 ± 0.31, p = 0.003). P wave duration on ECG proved to be independently associated with loss of atrial sensing on multivariable analysis (OR 1.062, 95% CI 1.015-1.110; p = 0.008). The prevalence of atrial fibrillation and subsequent switch to VVI mode was high (16%).

CONCLUSIONS

In the long-term follow-up, the loss of atrial sensing is present in 12% of patients with implanted VDD pacemakers. ECG and echocardiographic parameters may serve as screening tools for the detection of atrial myopathy which is associated with the loss of atrial sensing.

Biomarkers of Myocardial Injury and Inflammation after Permanent Pacemaker Implantation: The Lead Fixation Type Effect

Background

Permanent pacemaker implantation is accompanied by minor myocardial damage, indicated by elevated serum levels of cardiac biomarkers. Aim of this prospective study was to comparably investigate the lead fixation type effect on the extent of myocardial injury and inflammation following pacemaker implantation, and to assess the possible clinical implications.

Methods

Cardiac troponin I (cTnI) and C-reactive protein (CRP) were measured at baseline, 6 and 24h after implantation in 101 patients, categorized into the active and passive lead fixation group. Patients were followed up for clinical adverse events or abnormal pacing parameters at 24h, 7 and 30 days post-procedure.

Results

cTnI increased at 6h post-procedure (p<0.05) in 23.8% of patients, and returned to baseline after 24h. The passive group demonstrated significantly higher cTnI at 6h compared to the active group (p=0.006). CRP increased significantly at 6h, and maintained an upward trend after 24h (p<0.01) in both groups. The active group demonstrated significantly higher CRP at 6h compared to the passive group. We did not identify an association of positive biomarkers with adverse events.

Conclusion

cTnI and CRP can increase early after permanent pacemaker implantation, indicating mechanical myocardial injury and inflammation. The extent of these biomarkers elevation depends on the lead fixation type, and is not related to worse short-term prognosis.

Long-term outcome in patients receiving permanent pacemaker implantation for atrioventricular block: Comparison of VDD and DDD pacing

A permanent pacemaker (PPM) with dual chamber pacing (DDD) offers atrioventricular synchronization for patients with atrioventricular block (AVB). Single lead atrial synchronous ventricular pacing mode (VDD) is an alternative, but there are concerns about its efficacy and risk of atrial undersensing. Whether VDD can be a good alternative in patients with AVB remains unknown. The aim of the present study was to compare the long-term risk of mortality of VDD with DDD pacing.A total of 207 patients undergoing PPM implantations for AVB with VDD mode were enrolled from 2000 to 2013. Another 828 age- and sex-matched patients undergoing DDD implantations during the same period of time were selected as the control group in a 1 to 4 ratio. The study endpoint was mortality.A total of 1035 patients (64.3% male) were followed up for 46.5 ± 43.2 months. The mean ages were 75.0 years for VDD, and 74.9 years for DDD. The Kaplan-Meier survival analysis showed no significant difference in long-term survival between the VDD and DDD groups (log-rank P = 0.313). After adjustment for baseline characteristics, the VDD and DDD groups had a similar long-term prognosis with an adjusted hazard ratio of 0.875 (P = 0.445). Further analyses for the risk of cardiovascular and noncardiovascular deaths also showed no significant differences between the 2 groups.The long-term prognosis of VDD mode is comparable to that of DDD mode. Single lead VDD can be considered as an alternative choice in patients with AVB without sinus nodal dysfunction.

The impact of the distance between the atrial electrode and the atrial wall on atrial undersensing in patients with VDD pacemakers: long-term follow-up

AIM

Atrial undersensing (AUS) in single-lead VDD pacemakers may be due to diminished P-wave amplitude secondary to local inflammation beneath the electrodes closer to atrial wall. The aim of this study was to assess the potential effect of distance between atrial electrode and atrial wall on immediate and long-term atrial sensing stability in VDD systems.

METHODS

A total of 275 patients with normal sinus node function who received VDD pacemakers were enrolled into the study and were followed up for a median duration of 33 months. During each control visit, a standard 12-lead electrocardiogram (ECG) was obtained and standard pacemaker function assessment was performed including testing for pacing threshold and atrioventricular synchrony. The distance between atrial electrode and atrial wall was measured from chest X-ray.

RESULTS

Of the 275 patients, AUS was detected in 59 patients. Univariate predictors of AUS were use of closely spaced bipolar ring atrial electrode (CSBR) (P = 0.01), wider atrial ring-spacing (P = 0.03), and atrial sensitivity programmed to a higher level (P = 0.001). Use of CSBR (P = 0.04) and atrial sensitivity > or =0.3 mV (P = 0.02) were observed to be the independent predictors for AUS. When the distance between atrial electrode and atrial wall was <7 mm, AUS was less with diagonally arranged bipolar ring electrodes (DABR) than it was with CSBRs (P = 0.02).

CONCLUSIONS

The distance between atrial electrode and atrial wall does not appear to affect AUS incidence in VDD pacemakers. For VDD electrodes closer to atrial wall, AUS was significantly less likely in DABR-type electrodes.

Evolution of paced QRS and QTc intervals in children with epicardial pacing leads

AIMS

Permanent ventricular pacing in children is associated with ventricular dysfunction due to asynchronous activation. It is unclear whether paced QRS intervals increase disproportionately over time, which could potentially cause ventricular dysfunction.

METHODS

A total of 52 children, with bipolar steroideluting epicardial leads implanted at a median age of 5.6 years (0.0-17.4), was analyzed and followed up to 12.2 years (median 3.7). Patients were subdivided in two groups: right (RV, n = 21) and left (LV, n = 31) ventricular pacing. To correct for age, standard deviation scores (Z-scores) for paced QRS and QTc intervals were calculated from published standard-ECG norm-values. As a measure for individual paced QRS and QTc interval changes, a regression slope coefficient (incline(i)) was calculated for each patient's course.

RESULTS

Mean Z-scores for paced QRS intervals at first and last follow-up were 4.7 +/- 1.2 and 4.9 +/- 0.9 for group RV, 4.4 +/- 1.1 and 4.8 +/- 1.1 for group LV. Incline(i) of paced QRS (group RV: 0.038 [-0.27-0.12], group LV: 0.147 [-0.05-0.30]; p = 0.07) and QTc intervals (group RV: 0.026 [-0.08-0.06], group LV: 0.023 [-0.04-0.09]; p = 0.63) did not differ between both groups and indicated limited interval changes over time.

CONCLUSION

Neither epicardial pacing of the right nor left ventricle caused disproportionate paced QRS or QTc interval increases over time. An age-related prolongation of the electrical activation unlikely causes ventricular dysfunction.

Seguridad y eficacia de los sistemas de estimulación VDD monosonda

INTRODUCTION AND OBJECTIVES

Single-lead VDD pacing provides the physiological benefits of atrioventricular synchrony with the convenience of a single-lead system. However, concern remains about the method's safety and effectiveness.

METHOD

In total, 700 patients with single-lead VDD pacemakers were evaluated retrospectively. The following parameters were recorded: age, sex, etiology, the symptoms and electrocardiographic diagnosis that justified pacemaker implantation, the venous access route used for implantation, atrial sensing at implantation, atrial undersensing at follow-up, the occurrence of supraventricular tachyarrhythmias, and final pacing mode.

RESULTS

Third-degree atrioventricular block was the main indication for pacemaker implantation (66.4%). The most commonly used venous access route was via the right cephalic vein (49.1%). At implantation, the mean atrial signal was 1.8 (4 1.15) mV. During follow-up, significant atrial undersensing occurred in 7.7% of patients; in 1.9%, it could not be corrected by device reprogramming. Uncontrollable supraventricular arrhythmias were observed in 6.4% of patients. Symptomatic sinus node disease was rare. By the end of follow-up, 91.4% of patients were still on VDD pacing, while, in 8.3%, the pacemaker had to be reprogrammed to the VVI mode. Only 0.3% required atrial lead implantation for DDD pacing. Left-side venous access during implantation was a independent predictora of atrial undersensing at follow-up. Low values of atrial detection at implant did not reach statistical signification although it showed a remarkable trend.

CONCLUSIONS

Single-lead VDD pacing seems to be safe and effective when appropriately indicated. Our findings are consistent with those of previously published studies.

Biochemical Evidence of Cardiac Damage Following Transvenous Implantation of a Permanent Antibradycardia Pacemaker Lead

OBJECTIVES

We tested the hypothesis that transvenous permanent pacemaker lead implantation causes clinically detectable myocardial damage.

BACKGROUND

Histological evidence of myocardial damage has been reported after antibradycardia pacemaker lead implantation.

METHODS

We studied 30 patients undergoing implantation of a full antibradycardia pacemaker system (pulse generator plus leads) and 10 patients in whom only a generator was implanted. Blood samples for cardiac troponin-I (CTNI), CK-MB mass, and myoglobin measurement were drawn at baseline, at the end of the procedure, and at 2, 6, 12, 24, 48, and 72 hours thereafter.

RESULTS

Abnormal CTNI levels were noted only in 24 of the 30 patients undergoing a full system implantation. CTNI levels were already abnormal at the end of the procedure in 16 and became so in all 24 during the next 6 hours. Peak levels were reached within 6 hours in 21 patients and were compatible with "minimal" necrosis (CTNI < 1.5 pg/mL) in 20. Maximum ventricular lead diameter and number of implanted leads were independent predictors of peak CTNI levels. CK-MB mass also increased after the procedure, but exceeded the normal range in only 10 patients. Myoglobin levels increased significantly both in patients undergoing a complete system implantation and in those where only a pulse generator was implanted.

CONCLUSIONS

Transvenous insertion of endocardial leads for permanent pacing is accompanied in most patients by "minimal" myocardial damage. In this setting CTNI level kinetics are fast, characterized by early elevation and peak.

Long-term efficacy and stability of atrial sensing in VDD pacing

BACKGROUND

The efficacy and stability of atrial electrode sensing function is essential in maintaining atrioventricular (AV) synchrony and activity response in VDD pacing. Studies to evaluate the relationship between atrial sensing efficacy, stability, and implantation strategy are few.

HYPOTHESIS

This study sought to determine the possible predictors, among the recipients' underlying clinical conditions and the implantation strategies used, of achieving the most stable and effective atrial sensing.

METHODS

Eighty consecutive adults implanted with VDD pacemakers were studied retrospectively. Atrial electrodes were positioned where the optimal atrial potentials (APs) were measured during implantation. Interrogation parameters, including AV-synchrony ratio, were acquired immediately post implantation, at 1 year, and at 2 years after pacemaker implantation. Appropriate atrial sensing efficacy was defined as AV-synchrony ratio > or = 90%. The stability of atrial sensing was evaluated by the variation ranges of measured APs.

RESULTS

The measured APs showed no statistical difference when age, gender, or comorbidity was considered. However, with pacing-lead bending angles < or = 90 degrees, patients may have presented with larger APs and narrower AP variation than patients with obtuse angles. There were no clinical parameters in our study that could have predicted the proper atrial sensing efficacy with an AV-synchrony ratio > or = 90%.

CONCLUSIONS

The long-term sensing efficacy and stability of VDD pacing is reliable. More sophisticated implantation strategies may further improve the atrial sensing stability and efficacy in VDD pacing.