Atrial activation time and pattern of linear triple-site vs. single-site atrial pacing after cardioversion in patients with atrial fibrillation.

AIMS: Multisite atrial pacing has been suggested to be effective in suppressing atrial fibrillation (AF), however, the effect of linear triple-site atrial pacing (LTSP) in humans has not been evaluated. We compared the effects of LTSP to single-site atrial pacing (SSP) on the atrial activation and wavefront propagation pattern in patients with persistent AF. METHODS AND RESULTS: In 10 patients with persistent AF, the effects of LTSP and SSP were evaluated by left atrial (LA) endocardial non-contact multielectrode array mapping and multipolar catheters. LTSP and SSP were delivered from the high right atrium (HRA), the distal coronary sinus (CS), and within the LA at the site showing maximal overlay of low-voltage zones during sinus rhythm and pacing at HRA and CS. Atrial activation time and pattern, P wave duration, and the prevention of AF induced by burst pacing were assessed with these pacing interventions. Compared with SSP, LTSP at the HRA, CS, and LA shortened atrial activation times (183 +/- 24 vs. 174 +/- 24 ms, 186 +/- 29 vs. 166 +/- 28 ms, and 171 +/- 40 vs. 163 +/- 39 ms; P < 0.05, respectively). P wave duration was shorter with LTSP than SSP at all three sites (141.7 +/- 35.1 vs. 146.9 +/- 38.5 ms, 138.1 +/- 34.6 vs. 145.7 +/- 33.7 ms, and 142.7 +/- 33.4 vs. 151.3 +/- 35.1 ms; P < 0.05, respectively). LTSP initially depolarized a larger area than SSP, and produced more uniform and planar wavefront propagation. LTSP prevented the burst-induction of AF during LA pacing in 3 of 10 patients, while SSP was never successful. CONCLUSION: In patients with persistent AF, LTSP provided more rapid and uniform activation of the atria compared with SSP, which was associated with prevention of burst-induction of AF in some patients. Further study is required to determine whether LTSP can modify the substrate of chronic AF, leading to frank AF suppression.

Defibillator electrogram T wave alternans as a predictor of spontaneous ventricular tachyarrhythmias in defibrillator recipients.

BACKGROUND: Although T wave alternans (TWA) and the T wave peak-to-end (Tpte) interval are associated with vulnerability to ventricular tachyarrhythmia (VT), no previous reports have demonstrated that TWA immediately precedes spontaneous VT in the human ambulatory setting. METHODS AND RESULTS: Stored electrograms from the implantable cardioverter defibrillators (ICD) of 74 patients (59 males, 55.3+/-12.2 years) were analyzed. TWA (DeltaT amplitude), Tpte interval, QT interval, and RR intervals were measured from magnified digital images immediately before spontaneous VT (VT(Clinical); n=73), or immediately after ICD shocks during artificially-induced VT (VT(Induced); n=74) or inappropriate shocks (Shock(Inapp); n=6). (1) TWA was significantly greater in VT(Clinical) than VT(Induced) (P<0.01) or Shock(Inapp) (P<0.001), but Tpte was not (P=NS). (2) In the VT(Clinical) group, TWA was significantly greater in patients with ischemic VT than in those with non-ischemic cardiomyopathy or idiopathic VF (P<0.05). (3) In the same patient, the TWA for VT(Clinical) was significantly greater than that for VT(Induced) (P<0.01). CONCLUSION: TWA measured from ICD electrograms is significantly greater immediately before spontaneous VT than immediately after inappropriate shocks or shocks during induced VT. These findings indicate that repolarization alternans plays an important role in the induction of VT in humans.