PACING-INDUCED ATRIAL ARRHYTHMIAS IN A PORCINE MODEL OF ACUTE ALCOHOLIC INTOXICATION - DETERMINANTS OF INDUCIBILITY AND DURATION OF FLUTTERVERSUS FIBRILLATION

We have previously described that, in a closed-chest porcine model, mo derate alcoholic toxicity facilitates a variety of atrial tachyarrhyth mias. The purpose of the present study was to analyze the electrophysi ologic determinants and characteristics of each type of the observed a rrhythmias. Methods and Results: Fifteen pigs underwent 2 endocardial right atrial stimulation protocols (RASP) each after increasing doses of ethanol by means of one multipolar catheter advanced under heavy se dation from the femoral vein. Each RASP included 1,2 and 3 extrastimul i, and rapid pacing at 5 times diastolic threshold. Venous ethanol con centrations were measured (HPGC method) every 10 min and at the time o f arrhythmia induction. Atrial tachyarrhythmias were induced in 28/29 RASP tone animal died after the first dose of ethanol), and lasted for a mean of 127 sec. The longest atrial tachyarrhtyhmia induced for eac h RASP was atrial fibrillation in 16 RASP and atrial flutter in 12 RAS P. The mean venous ethanol concentration at the time of the longest ar rhythmia induced for each RASP was 198 + 84 mg/dl for RASP inducing fi brillation and 270 + 81 mg/dl for RASP inducing flutter (p<0.03). Flut ter tended to be sustained (>1 minute in duration) more often than fib rillation (9/12 flutter vs 4/16 fibrillation, p<0.007). In 5 experimen ts atrial flutter persisted for more than 10 minutes and was terminate d by overdrive atrial pacing. The mean P wave duration was 103 + 15 ms for RASP developing fibrillation vs 119 + 14 for RASP developing flut ter (p<0.01). The mean effective refractory period was 151 + 22 ms for RASP developing fibrillation vs 132 + 13 ms for RASP developing flutt er (p<0.01). Conclusions: 1) In this closed-chest porcine model, a var iety of atrial arrhythmias appear in response to programmed electrical stimulation. 2) Flutter as compared to fibrillation requires greater drug effect and electrophysiologic changes, and was more often sustain ed. 3) The association of the slower arrhythmia (flutter) with shorter refractoriness and slower conduction does not seem to follow the wave length theory.