gms | German Medical Science

Question : To compare arrhythmogenic responses to right and left mediastinal nerve stimulation.

Methods: After midline thoracotomy, right and left juxta-cardiac nerves were stimulated by trains of 5 pulses (1ms; 1 mA, 200 Hz) during the atrial refractory period. Activation maps were recorded from 191 epicardial and 63 endocardial unipolar electrograms

Results: Right nerve stimulation caused sinus bradycardia followed by right atrial tachycardia and atrial fibrillation (60%). Other responses were sinus bradycardia (14%), sinus tachycardia (2%) and atrial fibrillation without preceding sinus rhythm change (24%). The response to left nerve stimulation was atrial fibrillation without preceding sinus rhythm change (66%) whereas sinus bradycardia alone or followed by atrial fibrillation was elicited from the remaining left-nerve stimulations. After atropine sinus bradycardia as well as atrial fibrillation from either right- or left-nerve stimulation were abolished. With right nerve stimulation ectopic sites of origin were localized on the anterior right atrial epicardium, the Bachmann bundle region and adjacent right atrial appendage. With left nerve stimulation ectopic beats originated equally between the Bachman bundle region and the posterior left atrial wall near the pulmonary veins. Sites of early activation at arrhythmia onset corresponded to areas of repolarization changes determined by the difference in integral surface maps subtended by unipolar recordings at base line and during nerve stimulation.

Conclusions: Juxta-cardiac nerve stimulation induced atrial tachyarrhythmias and fibrillation from multiple discrete sites on both right and left atria. These sites corresponded to areas of repolarization change reflecting localized vagal effects as confirmed with atropine. Atrial tachyarrhythmias were not always preceded by an initial sinus bradycardia, especially in response to left nerve stimulation.