Abstract 10793: Notch Duration of Paced QRS Complex: a New Marker of Antitachycardia Pacing Effectiveness Among ICD Patients Without Cardiac Resynchronization Therapy.
Background: Among ICD patients with left ventricular dysfunction (LVD), improving the effectiveness of antitachycardia pacing (ATP) has become a relevant goal because shocks (SH) are associated with an increase in mortality. We speculated that the morphology of paced QRS complex from the right ventricular apex (pQRS) could be a marker of ATP efficiency because the presence of notches reflects delays in the activation of the left ventricle and may therefore be related to the times of conduction of stimulus from the pacing site to the origin of VT. Our aim in the present work was to prospectively determine the relationship between the duration of a notch >0.1 mV in the precordial leads of pQRS (DN-pQRS) and the effectiveness of ATP.
Methods: We analyzed 947 VT (CL: 333±45 ms) occurring consecutively in 104 ICD patients with LVD (LVEF: 31±8, primary prevention: 44%, pacing site: right ventricular apex; no cardiac-resynchronization therapy). ICD programming was standardized. The pQRS (pacing rate: 100 bpm) was obtained at ICD implantation (ECG: 50 mm/s).
Results: ATP was successful in 84% VT and 14% were terminated by SH. DN-pQRS correlated significantly with the probability of ineffective ATP (C=0.62; p<0.001). The cutoff point with the best sensitivity and specificity was 50 ms (60 and 70%, respectively). The adjusted mean ATP effectiveness per patient was 77% [95% CI: 70–84], generalized equation method (GEM). A total of 52 patients presented a DN-pQRS≥50 ms (DN50); they had a lower ATP efficiency -mean [95% CI]: 65% [53–75] vs. 91% [86–97]- and a higher proportion of VT terminated with SH: 34% [23–45] vs. 9% [2–16]; p<0.001 for both, GEM. The proportion of patients undergoing at least one SH due to VT was higher in those with a DN50: 59% vs. 37% p<0.001. By logistic regression -which included LVEF, basal QRS≥120 ms, indication, etiology, functional class, medical therapy and DN50- the latter (DN50) was found to be an independent predictor of the patient presenting with a VT- related SH (OR=3; p=0.02).
Conclusions: When ATP is applied to the right ventricular apex, the morphology of p-QRS is a predictor of effective ATP. Patients in whom the pQRS presents a DN50 need SH more frequently to terminate VT. In order to avoid SH, a reappraisal of alternative pacing sites may be warranted.
- © 2010 by American Heart Association, Inc.