Improved Atrial Mechanical Efficiency During Alternate- and Multiple-Site Atrial Pacing Compared With Conventional Right Atrial Appendage Pacing: Implications for Selective Site Pacing to Prevent Atrial Fibrillation

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.

Avoidance of Right Ventricular Pacing in Cardiac Resynchronization Therapy Improves Right Ventricular Hemodynamics in Heart Failure Patients

BACKGROUND

Cardiac resynchronization therapy (CRT) applied by pacing the left and right ventricles (BiV) has been shown to provide synchronous left ventricular (LV) contraction in heart failure patients. CRT may also be accomplished through synchronization of a properly timed LV pacing impulse with intrinsically conducted activation wave fronts. Elimination of right ventricular (RV) pacing may provide a more physiological RV contraction pattern and reduce device current drain. We evaluated the effects of LV and BiV pacing over a range of atrioventricular intervals on the performance of both ventricles.

METHODS

Acute LV and RV hemodynamic data from 17 patients with heart failure (EF = 30 +/- 1%) and a wide QRS (138 +/- 25 msec) or mechanical dyssynchrony were acquired during intrinsic rhythm, BiV, and LV pacing.

RESULTS

The highest LV dP/dt(max) was achieved during LV pre- (LV paced prior to an RV sense) and BiV pacing, followed by that obtained during LV post-pacing (LV paced after an RV sense) and the lowest LV dP/dt(max) was recorded during intrinsic rhythm. Compared with BiV pacing, LV pre-pacing significantly improved RV dP/dt(max) (378 +/- 136 mmHg/second vs 397 +/- 136 mmHg/second, P < 0.05) and preserved RV cycle efficiency (61.6 +/- 14.6% vs 68.6 +/- 11.4%, P < 0.05) and stroke volume (6.6 +/- 4.4 mL vs 9.0 +/- 6.3 mL, P < 0.05). Based on LV dP/dt(max), the optimal atrioventricular interval could be estimated by subtracting 30 msec from the intrinsic atrial to sensed RV interval.

CONCLUSIONS

Synchronized LV pacing produces acute LV and systemic hemodynamic benefits similar to BiV pacing. LV pacing at an appropriate atrioventricular interval prior to the RV sensed impulse provides superior RV hemodynamics compared with BiV pacing.