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

Abstract

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.

• Authors: Anant Khositseth, Jan Nemec, Joseph Hejlik, Win K Shen, Michael J Ackerman
• Journal: Annals of noninvasive electrocardiology : the official journal of the International Society for Holter and Noninvasive Electrocardiology, Inc (Ann Noninvasive Electrocardiol) Vol. 8 Issue 3 Pg. 208-14 (Jul 2003) ISSN: 1082-720X [Print] United States
• PMID: 14510655 (Publication Type: Comparative Study, Journal Article)

Chemical References

• Adrenergic alpha-Agonists
• Phenylephrine

Topics

• Adolescent
• Adrenergic alpha-Agonists (adverse effects)
• Adult
• Blood Pressure (drug effects)
• Bradycardia (chemically induced, physiopathology)
• Electrocardiography
• Female
• Genetic Predisposition to Disease (genetics)
• Genotype
• Heart Defects, Congenital (etiology, genetics, physiopathology)
• Heart Rate (drug effects)
• Humans
• Hypertension (chemically induced, physiopathology)
• Infusions, Intravenous
• Long QT Syndrome (etiology, genetics, physiopathology)
• Male
• Phenylephrine (adverse effects)
• Treatment Outcome