Experimental model simulating right ventricular outflow tract tachycardia: a novel technique to initiate RVOT-VT.
BACKGROUND
The mechanism(s) whereby a discrete area of myocardium in the RVOT becomes arrhythmogenic remains unknown.


METHODS
In 13 dogs, a circular catheter was placed in the proximal pulmonary artery (PA) to contact the endovascular circumference of the PA. A 50-msec train of high-frequency stimulation (HFS, 200 Hz), coupled to atrial pacing, was applied at each bipolar pair of the circular catheter. The coupling interval was adjusted so that the 50-msec train occurred during the ventricular refractory period, that is, the QRS complex, in order to prevent stimulation of the myocardial sleeve within the proximal PA.


RESULTS
In all dogs, HFS induced ventricular premature depolarizations and VTs with a left bundle branch block (LBBB) morphology and inferior axis (average 6.8 +/- 1.6 V). Earliest activation was consistently recorded from the proximal PA. Esmolol, a short-acting beta-blocker (1 mg/kg), was administered intravenously in 11 dogs. The inducible ventricular ectopy was abolished in 10 dogs (>12 V, P < 0.05) and the response to HFS was blunted in one dog (10-11 V). After 30 minutes, the response to HFS returned to pre-esmolol levels.


CONCLUSIONS
Stimulation of the sympathetic input to the proximal PA induces ventricular ectopy and VTs exhibiting a left bundle branch block morphology and inferior axis, closely simulating clinical RVOT-VT. Beta-blockade either abolishes or blunts this response, corroborating the sympathetic etiology in this model and in some clinical cases of RVOT tachycardias.
Zhou
Jing
J
Cardiac Arrhythmia Research Institute, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA.
Scherlag
Benjamin J
BJ
Yamanashi
William
W
Wu
Richard
R
Huang
Yan
Y
Lazzara
Ralph
R
Jackman
Warren M
WM
Po
Sunny S
SS
D000818:Animals; D004195:Disease Models, Animal; D004285:Dogs; D017180:Tachycardia, Ventricular / Q000209:etiology / Q000503:physiopathology*