Notes: Activations in Permanent Atrial Fibrillation. Introduction: Activation patterns during permanent atrial fibrillation (AF) in patients with organic heart diseases are unclear. Methods and Results: We studied six patients with permanent AF and organic heart diseases undergoing surgery. The duration of AF averaged 4.9 ± 7.6 years. Computerized epicardial mappings of the right atrial (RA) free wall and the left atrial (LA) posterior wall were simultaneously performed with 224 bipolar electrodes at 3-mm spatial resolution. In the RA, large wavefronts and conduction blocks were frequently observed. The lines of block correlated with the crista terminalis and large pectinate muscles. In contrast, the LA had rapid repetitive activities originated from corners of the electrode plaque, near the four pulmonary veins (PVs). On average, 2.8 ± 1.2 sites of rapid repetitive activities were identified per patient. They activated continuously, intermittently, or alternately during AF. The mean activation cycle length in the RA (196 ± 22 msec) was significantly longer than that in the LA (179 ± 26 msec; P = 0.004). The maximum dominant frequency in the LA was higher than that in the RA (6.41 ± 1.18 Hz vs 5.66 ± 0.55 Hz; P = 0.049). The maximum dominant frequency was consistently located in areas with rapid repetitive activations near the PVs. Conclusion: During human permanent AF associated with organic heart diseases, the activation cycle length was shorter in the LA posterior wall than in the RA free wall. Rapid repetitive activities are consistently observed in the LA posterior wall, at or near the PVs.

Notes: Background: Chronic right ventricular pacing has been reported to promote cardiac dyssynchrony. The PAVE trial prospectively compared chronic biventricular pacing to right ventricular pacing in patients undergoing ablation of the AV node for management of atrial fibrillation with rapid ventricular rates. Methods and Results: One hundred and eighty-four patients requiring AV node ablation were randomized to receive a biventricular pacing system (n = 103) or a right ventricular pacing system (n = 81). The study endpoints were change in the 6-minute hallway walk test, quality of life, and left ventricular ejection fraction. Patient characteristics were similar (64% male; age: 69 ± 10 years, ejection fraction: 0.46 ± 0.16; 83%, NYHA Class II or III). At 6 months postablation, patients treated with cardiac resynchronization had a significant improvement in 6-minute walk distance, (31%) above baseline (82.9 ± 94.7 m), compared to patients receiving right ventricular pacing, (24%) above baseline (61.2 ± 90.0 m) (P = 0.04). There were no significant differences in the quality-of-life parameters. At 6 months postablation, the ejection fraction in the biventricular group (0.46 ± 0.13) was significantly greater in comparison to patients receiving right ventricular pacing (0.41 ± 0.13, P = 0.03). Patients with an ejection fraction ≤45% or with NYHA Class II/III symptoms receiving a biventricular pacemaker appear to have a greater improvement in 6-minute walk distance compared to patients with normal systolic function or Class I symptoms. Conclusion: For patients undergoing AV node ablation for atrial fibrillation, biventricular pacing provides a significant improvement in the 6-minute hallway walk test and ejection fraction compared to right ventricular pacing. These beneficial effects of cardiac resynchronization appear to be greater in patients with impaired systolic function or with symptomatic heart failure.

Notes: Cardiac resynchronization therapy is now considered a standard therapy for patients with cardiomyopathy, heart failure, and interventricular conduction delay. Despite the demonstrated benefits in multiple large-scale trials, there is a clear nonresponder rate. This brief review will address some of the issues associated with maximizing the benefit of biventricular pacing, and whether or not advances in programming of such devices will increase the number of true responders.

Notes: DOSHI, R.N., et al.: Initial Experience with an Active-Fixation Defibrillation Electrode and the Presence of Nonphysiological Sensing. Nonphysiological sensing by a pacing and defibrillation electrode may result in inappropriate defibrillator discharges and/or inhibition of pacing. Active-fixation electrodes may be more likely to sense diaphragmatic myopotentials because of the protrusion of the screw for fixation. In addition, the movement of the fixation screw in an integrated bipolar lead system could also result in inappropriate sensing. This may be increasingly important in patients who are pacemaker dependent because the dynamic range of the autogain feature of these devices is much more narrow. Five of 15 consecutive patients who received a CPI model 0154 or 0155 active-fixation defibrillation electrode with an ICD system (CPI Ventak AV3DR model 1831 or CPI Ventak VR model 1774 defibrillator) are described. In 2 of the 15 patients, nonphysiological sensing appearing to be diaphragmatic myopotentials resulted in inappropriate defibrillator discharges. Both patients were pacemaker dependent. Changes in the sensitivity from nominal to less sensitive prevented inappropriate discharges. In one patient, discreet nonphysiological sensed events with the electrogram suggestive of ventricular activation was noted at the time of implantation. This was completely eliminated by redeployment of the active-fixation lead in the interventricular septum. In two other patients, discreet nonphysiological sensed events resulted in intermittent inhibition of ventricular pacing after implantation. These were still seen in the least sensitive autogain mode for ventricular amplitude. These were not seen on subsequent interrogation 1 month after implantation. Increased awareness of nonphysiological sensing is recommended. The CPI 0154 and 0155 leads seem to be particularly prone to this abnormality. Particular attention should be made when deploying an active-fixation screw for an integrated bipolar lead. This increased awareness is more important when a given individual is pacemaker dependent, which may warrant DFT testing in a least or less sensitive mode in these patients.