Characterization of sustained atrial tachycardia in dogs with rapid ventricular pacing-induced heart failure.
BACKGROUND
Atrial arrhythmias often complicate congestive heart failure (CHF). We characterized inducible atrial tachyarrhythmias and electrophysiologic alterations in dogs with CHF and atrial enlargement produced by rapid ventricular pacing.


RESULTS
Endocardial pacing leads were implanted in the right ventricle, right atrium, and coronary sinus in 18 dogs. The right ventricular lead was connected to an implanted pacemaker capable of rapid ventricular pacing. The atrial leads were used to perform electrophysiologic studies in conscious animals at baseline in all dogs, during CHF induced by rapid ventricular pacing at 235 beats/min in 15 dogs, and during recovery from CHF in 6 dogs. After 20 +/- 7 days of rapid ventricular pacing, inducibility of sustained atrial tachycardia (cycle length 120 +/- 12 msec) was enhanced in dogs with CHF. Atrial tachycardia required a critical decrease in atrial burst pacing cycle length (< or = 130 msec) for induction and often could be terminated by overdrive pacing. Calcium antagonists (verapamil, flunarizine, ryanodine) terminated atrial tachycardia and suppressed inducibility. Effective refractory periods at 400- and 300-msec cycle lengths in the right atrium and coronary sinus were prolonged in dogs with CHF. Atrial cells from dogs with CHF had prolonged action potential durations and reduced resting potentials and delayed afterdepolarizations (DADs). Mitochondria from atrial tissue from dogs with CHF were enlarged and had internal cristae disorganization.


CONCLUSIONS
CHF promotes inducibility of sustained atrial tachycardia. Based on the mode of tachycardia induction, responses to pacing and calcium antagonists, and presence of DADs, atrial tachycardia in this CHF model has a mechanism most consistent with DAD-induced triggered activity resulting from intracellular calcium overload.
Stambler
Bruce S
BS
Department of Medicine/Cardiology, West Roxbury Veterans Affairs Medical Center, Harvard Medical School, West Roxbury, Massachusetts, USA. bss4@po.cwru.edu
Fenelon
Guilherme
G
Shepard
Richard K
RK
Clemo
Henry F
HF
Guiraudon
Colette M
CM
D000200:Action Potentials / Q000502:physiology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D009320:Atrial Natriuretic Factor / Q000097:blood; D001794:Blood Pressure / Q000502:physiology; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects*; D004195:Disease Models, Animal; D004285:Dogs; D004452:Echocardiography; D004562:Electrocardiography; D022062:Electrophysiologic Techniques, Cardiac; D006325:Heart Atria / Q000000981:diagnostic imaging / Q000187:drug effects / Q000503:physiopathology; D006333:Heart Failure / Q000209:etiology* / Q000401:mortality / Q000503:physiopathology; D006352:Heart Ventricles / Q000000981:diagnostic imaging / Q000187:drug effects / Q000503:physiopathology; D008955:Models, Cardiovascular; D020127:Recovery of Function / Q000502:physiology; D013318:Stroke Volume / Q000502:physiology; D016019:Survival Analysis; D013612:Tachycardia, Ectopic Atrial / Q000145:classification* / Q000209:etiology* / Q000503:physiopathology; D018487:Ventricular Dysfunction, Left / Q000209:etiology / Q000503:physiopathology
D000319:Adrenergic beta-Antagonists; D000889:Anti-Arrhythmia Agents; D009320:Atrial Natriuretic Factor