QT Interval Prolongation and Torsades de Pointes Unmasked by Intracoronary Acetylcholine...

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IntroductionElectrocardiograms (ECGs) of some patients

with congenital long QT syndrome (LQTS) mayshow a normal QT interval on some occasions.1

The present case showed a normal QT interval onadmission, but intracoronary administration ofacetylcholine, which was performed to excludevasospastic angina, unmasked abnormal QT inter-val prolongation and induced torsades de pointesas the authors reported earlier in LQTS patientsmanifesting a long QT interval.2

Case ReportA 75-year-old woman was referred for treat-

ment of chest pain. She had no previous episodesof syncope, and no medication had been pre-scribed. She had 12 siblings and two children, andten of them died due to noncardiac diseases. Nei-ther cardiac events nor a history of syncope havebeen observed in the remaining family members.On admission to the hospital, the ECG showednormal sinus rhythm, and QT and QTc intervalswere 380 ms and 447 ms, respectively (Fig. 1).During Holter ECG, no transient ST-T change wasdetected and the QTc interval was entirely withinthe normal range. The left ventriculogram showednormal contraction and the coronary angiogramshowed no stenotic lesions. Then, intracoronaryadministration of acetylcholine was undertaken torule out vasospastic angina. Acetylcholine wasdissolved in saline at 37°C. When acetylcholine at

PACE, Vol. 24 October 2001 1561

100 mg was administrated into the left coronaryartery, the QTc interval prolonged unexpectedlyfrom 434 to 642 ms and ventricular prematurebeats developed in a bigeminal pattern creatingshort-long cycle sequences that were promptly fol-lowed by the onset of a torsades de points3 (Fig. 1).Coronary angiograms did not show any spastic le-sions and the ST segment on the ECG was stablebefore torsades de pointes appeared. Blood pres-sure and heart rate were unchanged by the admin-istration of acetylcholine (Fig. 1). Injection ofsaline into the left coronary artery did not induceQT interval prolongation. After the catheteriza-tion, the authors serially recorded ECGs whichdisclosed QT interval prolongation, but only in-frequently. Later, an intravenous epinephrine in-jection prolonged the QT and QTc intervals from420 to 460 ms and from 412 to 532 ms, respec-tively. Programmed electrical stimulation failed toinduce any ventricular arrhythmia. These obser-vations suggested that the patient was a sporadiccase of LQTS. Genetic analysis has been under-taken, and until now no mutation has been identi-fied in the KvLQT1 gene (exon 3,5–8,12,13, and15), in the HERG gene (exon 6 and 7) or in theSCN5A gene (exon 23,24,26,28).1,4,5

DiscussionIn the present case, ECG on admission and

Holter ECG showed a normal QT interval, and theabnormal QT interval prolongation was first dis-closed by acetylcholine injection. Later studies sug-gested that she was a case of LQTS. The mechanismof acetylcholine induced QT interval prolongationin LQTS is uncertain, but bradycardia, a fall ofblood pressure, and coronary spasms is unlikely asthe cause of the QT interval prolongation.2 Sincethe acetylcholine induced QT interval prolonga-

QT Interval Prolongation and Torsades dePointes Unmasked by IntracoronaryAcetylcholine AdministrationMASAOMI CHINUSHI, IWAO NAKAGAWA, TOMOYUKI HORI, FUMIOYAMASHITA, TAKASHI WASHIZUKA, and YOSHIFUSA AIZAWAFrom the First Department of Internal Medicine, Niigata University School of Medicine, Niigata, Japan

CHINUSHI, M., ET AL.: QT Interval Prolongation and Torsades de Pointes Unmasked by IntracoronaryAcetycholine Administration. Intracoronary acetylcholine administration, which was performed to ex-clude vasospasms, unmasked an abnormal QT interval prolongation and initiated torsades de pointes ina patient with normal QT interval at rest. (PACE 2001; 24:1561–1562)

long QT syndrome, acetylcholine, torsades de pointes

Address for reprints: Masaomi Chinushi, M.D., First Dept. ofInternal Medicine, Niigata University School of Medicine, 1-754 Asahimachi Niigata 951-8510, Japan. Fax: (81)-25-227-0774; e-mail: chinushi@med.niigata-u.ac.jp

Received June 27, 2000; revised November 10, 2000; acceptedDecember 22, 2000.

Reprinted with permission fromJOURNAL OF PACING AND CLINICAL ELECTROPHYSIOLOGY , Volume 24, No. 10, October 2001

Copyright © 2001 by Futura Publishing Company, Inc., Armonk, NY 10504-0418.

tion was prevented by pretreatment with atropine.2

muscarine receptors seem to be involved in thisunique response. This is the first report that re-vealed that LQTS was unmasked by intracoronaryacetylcholine administration. Although rare, atten-

References1. Schwartz PJ, Priori SG, Napolitano C. The long QT syndrome. In

DP Zipes, J Jalife (eds.): Cardiac Electrophysiology: From Cell toBedside. 3rd ed. Philadelphia, PA, WB Saunders, 1999, pp.597–615.

2. Furushima H, Niwano S, Chinushi M, et al. Effect of atropine on QTprolongation and torsade de pointes induced by intracoronaryacetylcholine in the long QT syndrome. Am J Cardiol 1999;83:714–718.

3. El-Sherif N, Caref EB, Chinushi M, et al. Mechanism of arrhythmo-

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Figure 1. Electrocardiograms. Panel A was obtained on admission. Panel B was recorded beforeand during administration of acetylcholine. When acetylcholine was injected, the QTc intervalwas prolonged, but heart rate (HR) and blood pressure (BP) were stable (HR: 58 ® 56 beats/min,BP: 132/78 ® 128/74 mmHg). Immediately after acetylcholine administration, torsades de pointedeveloped (Panel C).

tion should be paid to the QT interval when unex-pected torsades de pointes occurs during theacetylcholine provocation test because manifesta-tion of QT interval prolongation may be associatedwith the initiation of torsades de pointes.

genicity of the short-long cardiac sequence that precedes ventricu-lar tachyarrhythmias in the long QT syndrome. J Am Coll Cardiol1999; 33:1415–1423.

4. Roden DM, Lazzara R, Rosen M, et al. Multiple mechanisms in thelong QT syndrome. Current knowledge, gaps, and future directions.Circulation 1996; 94:1996–2012.

5. Splawski I, Shen J, Timothy KW, et al. Spectrum of mutation in longQT syndrome genes. KvLQT1, HERG, SCN5A, KCNE1 and KCNE2.Circulation 2000; 102:1178–1185.