title: Laser photoablation of ventricular tachycardia: correlation of diastolic activation times and photoablation effects on cycle length and termination--observations supporting a macroreentrant mechanism.
abstract: Neodymium:yttrium-aluminum-garnet (YAG) photocoagulation during ventricular tachycardia allows the electrophysiologic effects of the temporal and spatial sequence of energy delivery to be correlated with local activation times. A retrospective analysis was performed of the termination of 19 episodes of ventricular tachycardia for which the local diastolic activation time was known for all successful ablation sites and for 95% of all ablation sites. The mode of termination was compared with that of 26 episodes of spontaneously terminating ventricular tachycardias. Spontaneous terminations occurred without a change in cycle length (54%) or with a 7 +/- 15% change in cycle length over one to three terminal beats (46%). In contrast, laser ablation-induced terminations resulted in a 39 +/- 55% increase in cycle length over nine or more cycles. The effect of attempted laser ablation was compared with the local presystolic activation time and the local activation time expressed as a percent of the diastolic interval (end of QRS complex = 0%, onset of next QRS complex = 100%). With one exception, no tachycardia terminated at ablation sites activating less than -50 ms before the QRS complex. All 8 successful first ablation attempts and 13 of all 19 successful ablations occurred in the 35% to 50% interval of diastolic activation. All successful ablations at sites activating at greater than 50% of the diastolic interval required multiple ablation attempts. Successful ablation was performed from the epicardium in 6 and from the endocardium in 13 episodes of ventricular tachycardia. These results are most consistent with a macroreentrant mechanism with a region of high vulnerability represented by the 35% to 50% interval of diastolic activation.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Laser and Applied Technologies Program, Carolinas Heart Institute, Charlotte, North Carolina 28232.
authors.forename: R H
authors.initials: RH
authors.lastname: Svenson
authors.forename: L
authors.initials: L
authors.lastname: Littmann
authors.forename: P G
authors.initials: PG
authors.lastname: Colavita
authors.forename: S H
authors.initials: SH
authors.lastname: Zimmern
authors.forename: J J
authors.initials: JJ
authors.lastname: Gallagher
authors.forename: J M
authors.initials: JM
authors.lastname: Fedor
authors.forename: J G
authors.initials: JG
authors.lastname: Selle
mesh_terms: D003971:Diastole / Q000502:physiology*; D004562:Electrocardiography; D006801:Humans; D008028:Light Coagulation / Q000379:methods; D016343:Monitoring, Intraoperative; D010507:Periodicity; D012189:Retrospective Studies; D013610:Tachycardia / Q000503:physiopathology / Q000601:surgery*; D013997:Time Factors