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Atropine-triggered idiopathic ventricular tachycardia in an asymptomatic pediatric patient

Hsin-Chu Hsien, Taiwan

To the Editor:

Although idiopathic ventricular tachycardia (VT) in pediatric patients is not uncommon,¹ it might accidentally be elicited in an undiagnosed and asymptomatic patient during induction of anesthesia. We present a nine-year-old girl who was scheduled to undergo bilateral myringotomy with tube insertion. Due to her young age and unremarkable past history, a routine 12-lead electrocardiogram (ECG) was not required. Preoperative physical examination revealed no cardiac murmur or cyanosis. Baseline blood pressure and heart rate were 102/49 mmHg and 80 beats·min^–1, respectively. Unexpectedly, episodes of ventricular premature contractions (VPC) with bigeminy or trigeminy couplets were noted on the ECG before induction. The patient did not feel uncomfortable but was clearly anxious. Normal sinus rhythm resumed spontaneously 15 min later. After discussing with her family and surgeon, we decided to continue the induction of anesthesia with atropine (0.2 mg, iv), thiopental (140 mg, iv) and atracurium (15 mg, iv), followed by tracheal intubation. Shortly after atropine was given, a wide-QRS pattern VT (180 to 195 beats·min^–1) was seen on the ECG. As femoral artery pulsation was still present, a first dose of 30 mg lidocaine was administered intravenously. VT was not abolished but converted to sinus rhythm after a second dose of lidocaine was administered three minutes later.² A 12-lead ECG was obtained after stable hemodynamics (90 beats·min^–1 and 90/50 mmHg) were achieved and displayed normal sinus rhythm, left bundle branch block, and juvenile T-wave patterns. The surgical procedure was cancelled and the patient recovered from anesthesia (maintained with sevoflurane and O₂) without reversal of atracurium. No further episodes of VT were observed during emergence. Subsequent 12-lead and 24-hr Holter ECG captured sporadic VPC (Figure A). A transthoracic echocardiogram showed normal heart structures and a treadmill-exercise test failed to induce any VPC or VT. Because the patient and her parents refused further cardiac electrophysiological examination, a final diagnosis of VT originating from the right ventricular outflow tract (RVOT) could not be confirmed.³ Study of heart rate variability showed high sympathetic activity in the supine resting state (Figure B). Strenuous exercise induced vagal withdrawal and more sympathetic activation (Figure C), but not sufficient to provoke VPC or VT. Since sympathovagal balance changes prior to the onset of cardiac arrhythmias,^4,5 the vagolytic action of atropine might have facilitated the initiation of RVOT-VT in this case. Sporadic or occasional VPC in an asymptomatic pediatric patient should not be overlooked before induction of anesthesia.

View larger version (30K): [in this window] [in a new window]   FIGURE Electrocardiogram (ECG) tracings and power spectra of heart rate variability (HRV) taken one year after the ventricular tachycardia (VT) attack. A) ECG (slow and fast sweeps) displayed occasional single-focus ventricular premature beats (VPC). B) Supine resting condition: mean heart rate (HR): 82 beats·min–1; sympathetic dominance (LF/HF = 3.9). C) Strenuous exercise condition: mean HR: 99 beats·min–1; more prominent sympathetic activation with vagal withdrawal (LF/HF = 9.0 and reduced HF). LF(nu) = normalized lower frequency power; HF(nu) = normalized high frequency power. Upper panel = ten-second ECG tracing; lower panel = five-minute HRV analysis.

References

1 Pfammatter JP, Bauersfeld U. Idiopathic ventricular tachycardias in infants and children. Card Electrophysiol Rev 2002; 6: 88–92.[Medline]

2 Tsuchiya T, Okumura K, Honda T, Iwasa A, Ashikaga K. Effects of verapamil and lidocaine on two components of the re-entry circuit of verapamil-senstitive idiopathic left ventricular tachycardia. J Am Coll Cardiol 2001; 37: 1415–21.[Abstract/Free Full Text]

3 Dixit S, Gerstenfeld EP, Callans DJ, Marchlinski FE. Electrocardiographic patterns of superior right ventricular outflow tract tachycardias: distinguishing septal and free-wall sites of origin. J Cardiovasc Electrophysiol 2003; 14: 1–7.[Medline]

4 Fei L, Statters DJ, Hnatkova K, Poloniecki J, Malik M, Camm AJ. Change of autonomic influence on the heart immediately before the onset of spontaneous idiopathic ventricular tachycardia. J Am Coll Cardiol 1994; 24: 1515–22.[Abstract]

5 Hayashi H, Fujiki A, Tani M, Mizumaki K, Shimono M, Inoue H. Role of sympathovagal balance in the initiation of idiopathic ventricular tachycardia originating from right ventricular outflow tract. Pacing Clin Electrophysiol 1997; 20: 2371–7.[Medline]

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