Effect of phenylephrine provocation on dispersion of repolarization in congenital long QT syndrome

Anant Khositseth, Jan Nemec, Joseph Hejlik, Win K. Shen, Michael J. Ackerman

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


Introduction: Syncope and sudden death are associated with sympathetic stimulation in LQT1 while LQT2 patients are more susceptible to arrhythmias during nonexertional states. Abnormal spatial (QTd)- and transmural (TDR)-dispersion of repolarization may indicate increased arrhythmogenicity. This study compares the effect of phenylephrine on QTd and TDR in genotyped LQTS to control (C). Methods and Results: Seventeen LQT1, 12 LQT2, and 18 age- and sex-matched normal controls received 2 mcg/kg of phenylephrine intravenously. At baseline and peak phenylephrine effect, BP, QT, RR, Bazett's QTc, precordial QTd (QTmax-QTmin), and T-peak to T-end (Tp-e) intervals were determined blinded to the patient's clinical and genotype status. Baseline QT intervals and QTc were significantly longer in LQT1 and LQT2 compared to C. Baseline QTd and Tp-e were greater in LQT2 than either LQT1 or C: QTd = 79 ± 29 ms (LQT2), 53 ± 26 (LQT1), and 45 ± 15 (C) and Tp-e = 120 ± 30 ms (LQT2), 99 ± 20 (LQT1), and 90 ± 11 (C). Overall, phenylephrine exerted no significant effect on either QTd or Tp-e except with subgroup analysis of symptomatic LQTS where LQT1 and LQT2 patients had a divergent response with TDR. Conclusions: Phenylephrine-induced bradycardia decreased TDR in symptomatic LQT1 but increased TDR in symptomatic LQT2. The observed effects of phenylephrine are consistent with the protective effect of beta-blocker in LQT1 and the increased arrhythmogenicity noted during nonexertional states in LQT2.

Original languageEnglish (US)
Pages (from-to)208-214
Number of pages7
JournalAnnals of Noninvasive Electrocardiology
Issue number3
StatePublished - Jul 2003


  • Dispersion of repolarization
  • Electrocardiography
  • Long QT syndrome
  • Phenylephrine

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)


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