Hyperventilation facilitates induction of supraventricular tachycardia: A novel method and the possible mechanism

Introduction: Hyperventilation has been demonstrated to alter autonomic function. Sympathomimetic drugs (isoproterenol) and parasympatholytic drugs (atropine) may be needed to facilitate induction of supraventricular tachycardia (SVT). The aim of this study was to test the clinical utility and mechanisms of hyperventilation to facilitate SVT initiation. Methods and Results: Fourteen patients with clinically documented SVT (9 AV nodal reentrant tachycardia and 5 AV reciprocating tachycardia) but noninducible during baseline electrophysiologic study were included. Immediately after hyperventilation test (at least 30 respirations/min) for 2 minutes, systolic blood pressure, sinus cycle length, anterograde and retrograde 1:1 conduction, and induced SVT were measured. Arterial blood gas, pH, and heart rate variability before and after hyperventilation were measured. Seven of nine patients with AV nodal reentrant tachycardia and 3 of 5 patients with AV reciprocating tachycardia could be induced immediately after the hyperventilation test. After hyperventilation, anterograde AV and retrograde VA 1:1 conduction were improved, sinus cycle length was decreased, and heart rate variability were decreased in both groups. Conclusion: Hyperventilation can facilitate induction of SVT. Improvement of conduction properties and changes of autonomic function are the possible mechanisms.