Selective Site Pacing:. The Right Ventricular Approach

Prediction of midterm performance of active-fixation leads using current of injury

BACKGROUND

There are only limited prospective data on the clinical relevance of current of injury (COI) as a predictor of the midterm performance of active-fixation leads. This study sought to investigate whether it is possible to predict the midterm performance of active-fixation leads using COI recorded at the time of implantation.

METHODS AND RESULTS

One hundred fifty patients (78 men; mean age, 63 ± 19 years) who received active-fixation pacing (n = 201) and defibrillator (n = 51) leads were studied. COI was measured from the intracardiac bipolar electrogram recorded at the time of lead implantation. The study outcome was good lead performance at 6 months, defined as P wave ≥ 1.5 mV, threshold <1.5 V for atrial lead, R-wave ≥ 5 mV, and threshold <1 V for ventricular lead. A total of 102 active-fixation atrial and 150 ventricular leads were implanted. During a 6-month follow-up, invasive intervention was required for seven atrial and seven ventricular leads. In multivariate analysis, COI was the only independent predictor of good outcome for the active-fixation atrial (odds ratio [OR]: 5.67, 95% confidence interval [CI]: 2.18-14.76, P = 0.001) and ventricular leads (OR: 3.99, 95% CI: 1.08-21.26, P = 0.002). Receiver-operating characteristic analysis identified ST-segment elevation ≥2.0 mV for the atrial leads (sensitivity, 75%; specificity, 89%) and ≥10.0 mV for the ventricular leads (sensitivity, 70%; specificity, 87%) as optimal cutoffs for good midterm performance.

CONCLUSIONS

Midterm performance of active-fixation leads is predictable using COI recorded at the time of lead implantation. A ST-segment elevation ≥2.0 mV in the atrial leads and ≥10.0 mV in the ventricular leads are recommended to improve the lead performance at 6 months.

Medium-term effects of septal and apical pacing in pacemaker-dependent patients: a double-blind prospective randomized study

BACKGROUND

Pacing the right ventricle is established practice, but there remains controversy as to the optimal site to preserve hemodynamic function.

AIMS

To evaluate clinical and hemodynamic differences between apical and septal pacing in pacemaker-dependent patients.

METHODS

Patients receiving their first pacemaker for advanced atrioventricular block, with the atria in sinus rhythm, were randomized to receive apical (Group A) or septal (Group S) ventricular leads. After implant, with the device programmed VVI 70 beats/min fixed rate, patients underwent a 6-minute walk test and a transthoracic echocardiogram. Then, DDDR was programmed at nominal settings. The same tests were performed at 6 months and 12 months follow-up. If ventricular pacing was less than 98%, the patient was excluded.

RESULTS

A total of 142 patients were included in the study. During the study year, 71 (50%) were excluded for not fulfilling the condition of 98% ventricular pacing. Groups A and S had 34 and 37 patients, respectively. Age and gender were similar in the groups. At implant, QRS duration was significantly greater in Group A (158 ms) than Group S (146 ms; P = 0.018), and the QRS axis was different: -74.5° in Group A and 1° in Group S (P < 0.001). At 1 year, the 6-minute walk improved significantly in both groups: Group A 15% (P = 0.048) and Group S 24% (P = 0.001). Left ventricular ejection fraction (LVEF) increased from 0.57 to 0.61 (P = 0.008) in Group S, without significant change in Group A.

CONCLUSIONS

After 1 year, pacemaker-dependent patients with septal ventricular leads have better clinical and functional (LVEF) outcome.

Failure of the active-fixation mechanism during removal of active-fixation pacing leads

BACKGROUND

 Active-fixation pacing leads are being widely employed due to their theoretical advantages when compared with traditional passive-fixation leads: easy fixation and reposition, possible deployment in alternative pacing sites, lower rates of dislodgment, and chronic removability. However, the behavior of the active-fixation mechanism during lead removal has not been yet systematically studied and may have important clinical implications.

OBJECTIVE

 To evaluate if the active-fixation mechanism was still working properly in pacing leads that were removed due to different causes.

METHODS

 Thirty-one consecutive patients undergoing active-fixation lead removal (40 leads) were studied. Before lead removal, the helix was retracted using the appropriate tool, and fluoroscopy signs were evaluated. After removal, the helix status was examined, and the active-fixation mechanism was once again retested when possible.

RESULTS

 In nine of 40 leads (22.5%), the helix remained extended after lead removal in spite of having applied the number of rotations recommended by the manufacturer with the clip-on tool. There was no linear relationship between lead longevity and the presence of an extended helix after lead removal. However, failure of the active-fixation mechanism was more frequent among leads implanted <1 year before versus >1 year before (OR 6.8, 95% CI 1.1-42.7, P = 0.043). In 38% of patients with failure of the active-fixation mechanism, a previous lead reposition had been attempted before lead removal due to significant pacing threshold rise.

CONCLUSIONS

 In our series, the active-fixation mechanism failed in up to 22.5% of explanted leads. This may have important clinical implications during active-fixation lead removal and reposition.

Implantation of lumenless pacing leads at the inter-atrial septum and right ventricular outflow tract with deflectable catheter-sheath

Current permanent right ventricular and right atrial endocardial pacing leads are implanted utilizing a central lumen stylet. Right ventricular apex pacing initiates an abnormal asynchronous electrical activation pattern, which results in asynchronous ventricular contraction and relaxation. When pacing from right atrial appendage, the conduction time between two atria will be prolonged, which results in heterogeneity for both depolarization and repolarization. Six patients with Class I indication for permanent pacing were implanted with either single chamber or dual chamber pacemaker. The SelectSecure 3830 4-French (Fr) lumenless lead and the SelectSite C304 8.5-Fr steerable catheter-sheath (Medtronic Inc., USA) were used. Pre-selected pacing sites included inter-atrial septum and right ventricular outflow tract, which were defined by ECG and fluoroscopic criteria. All the implanting procedures were successful without complication. Testing results (mean atrial pacing threshold: 0.87 V; mean P wave amplitude: 2.28 mV; mean ventricular pacing threshold: 0.53V; mean R wave amplitude: 8.75 mV) were satisfactory. It is concluded that implantation of a 4-Fr lumenless pacing lead by using a streerable catheter-sheath to achieve inter-atrial septum or right ventricular outflow tract pacing is safe and feasible.

Alternate Site Atrial Pacing in the Young: Conventional Echocardiography and Tissue Doppler Analysis of the Effects on Atrial Function and Ventricular Filling

BACKGROUND

Although the right atrial appendage (RAA) is typically used for atrial pacing lead implant, recent studies have shown benefits of alternate site atrial pacing (ASAP) in the elderly. However, comparable studies in the young are lacking.

METHODS

To investigate effects of ASAP on cardiac function and atrioventricular mechanical interactions in the young, 26 subjects (ages 10 to 23 years) with normal cardiac anatomy, function, and atrioventricular node conduction underwent echocardiography during electrophysiology studies while in sinus rhythm (NSR), and with temporary pacing from high right atrium (HRA), RAA, mid septal right atrium approximating Bachmann's bundle (BB), and left atrium (LA) via the distal coronary sinus (CS). After a paced steady state of 10 minutes, left atrial total and systolic ejection fractions, color-guided mitral inflow, and annular tissue Doppler indices were obtained. Left ventricular ejection fraction and myocardial performance indexes (MPI) were calculated.

RESULTS

The total and systolic LA ejection fractions were higher during the NSR compared to all ASAP. Mitral inflow velocities changed significantly with ASAP. The passive/active ventricular filling ratio (E/A) deteriorated from NSR to HRA to BB to CS. There were significant changes in late diastolic tissue Doppler velocities during ASAP compared to NSR. The MPI during ASAP differed from those during the NSR. HRA and Bachmann bundle pacing provided better MPIs than RAA or CS pacing.

CONCLUSION

The location of atrial pacing leads has an acute impact on cardiac function and atrioventricular mechanical interaction. Pacing close to sinus node location may be beneficial in the young.

Cardiac resynchronisation therapy for heart failure

Heart failure (HF) is increasingly common and, despite advances in pharmacotherapeutic management, often progresses. Progression is marked by structural and electrical changes-remodelling. In approximately one-third of patients, ventricular dilatation is accompanied by intraventricular conduction delays, most commonly the left bundle branch block (LBBB). The presence of LBBB is associated with mechanical dyssynchrony of the heart. Cardiac resynchronisation therapy (CRT), the use of special pacemakers with or without implantable cardioverter defibrillators, aims to resynchronise the failing heart, improving myocardial contraction without increased energetics. Several, large, randomised clinical trials have now established the benefit of CRT in a select group of HF patients, providing functional and, recently shown, mortality benefits. However, a substantial proportion of patients are considered non-responders to CRT, and studies are now underway to identify the patients most likely to respond to CRT.

Long-Term Performance of Active-Fixation Pacing Leads: A Prospective Study

BACKGROUND

Despite the increasingly widespread use of active-fixation leads, long-term clinical follow-up of pacing lead outcomes is lacking. The aim was to analyze pacing parameters over a 2-year follow-up. We performed a prospective observational study of consecutive new pacemaker implants using the 1488T St. Jude (100) and the Medtronic 5076 (100) active-fixation leads. Detailed analysis of pacing parameters was collected at implant, day 1, and 1, 3, 6, 12, 18, and 24 months.

METHODS AND RESULTS

One hundred patients underwent implantation of 100 dual-chamber pacemakers. Initial pacing parameters in the ventricle were threshold 0.7 +/- 0.2 V, R wave 12.0 +/- 6.5 mV, and impedance 879 +/- 224 Omega. Threshold increased significantly from day 1 (0.7 +/- 0.2 V) to month 1 (0.9 +/- 0.6 V, P < 0.01) and remained stable over the long term. Four of the 100 patients had a threshold >2 V (mean 3.3 +/- 0.9 V) all between day 1 and month 3. For all patients, R wave remained stable, but impedance declined significantly from day 1 (879 +/- 184 Omega) to month 1 (677 +/- 122 Omega, P < 0.01). There were no ventricular lead complications. Initial pacing parameters in the atrium were threshold 0.9 +/- 0.3 V, P wave 3.3 +/- 2.4 mV, and impedance 606 +/- 144 Omega. Threshold remained stable over the long-term follow-up. One of 100 patients had a rise in threshold >2 V (2.2 V) between day 1 and month 1. No patients underwent lead repositioning. Sensing and impedance remained stable over the long term. Patient follow-up was completed in 94% (6 unrelated deaths). There was an 8% incidence of atrial fibrillation.

CONCLUSION

Active-fixation leads are generally associated with stable long-term pacing parameters.

Cardiac resynchronization therapy using a VDD lead

In heart failure patients with normal sinus node function, cardiac resynchronization therapy can be achieved with only two leads, one VDD type, and one left ventricular. This reduces the number of venous punctures, implanted leads, and possibly operation and fluoroscopic times and complication rates. We present two cases and discuss the advantages and limits of such a procedure.

Controversies in pacing: Indications and programming

This article reviews controversies in cardiac pacing in four areas: methods to prevent unnecessary right ventricular pacing and optimal ventricular pacing sites in the bradycardia population, pacing for prevention of atrial fibrillation (AF), a novel pacing technique for the treatment of heart failure, and pacing for the treatment of sleep apnea. Frequent right ventricular pacing has been reported to increase the incidence of AF and congestive heart failure. However, many patients with pacemakers for bradycardia have intrinsic atrioventricular conduction most of the time. Optimal programming of pacemakers and new algorithms designed to reduce unnecessary ventricular pacing are discussed. Pacing algorithms for prevention of AF have generally been shown to be ineffective. Atrial antitachycardia pacing has been shown to reduce the burden of atrial tachyarrhythmias in selected patients. Cardiac contractility modulation has recently been reported to be a promising new approach to the treatment of heart failure. Some pacing techniques may be effective in the treatment of sleep apnea but larger, long-term clinical trials are required to demonstrate a significant clinical benefit.