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Effect of Beta-blocker Therapy on QTc Response in Exercise and Recovery in Normal Subjects

NCT00588965 · Status: COMPLETED · Phase: NA · Type: INTERVENTIONAL · Enrollment: 36

Last updated 2013-07-30

Study results available
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Summary

Background. In congenital long QT syndrome type 1 (LQT1), episodes of ventricular tachycardia are usually triggered by exercise and can be prevented in most patients by beta-blocker therapy. In addition, LQT1 associated with a normal resting QT interval can be unmasked by the abnormal QT response to exercise testing (failure of the QT interval to shorten normally). Preliminary data from our laboratory show that the exercise QT intervals of patients with LQT1 are partially normalized by beta-blocker therapy. It is still currently not known if beta-blockers modify the QT/heart rate relationship (a primary effect on repolarization) or if the "normalizing" effect is due to the inability of subjects on beta-blockers to attain sufficiently high workloads (due to reduced heart rate) for prolongation to occur. Moreover, the physiologic response of the exercise QT interval to beta-blockers in healthy control subjects is not known.

Objective. The objective of this study is to define the impact of beta-blocker therapy on the QT response to exercise and recovery in normal subjects.

Methods. Approximately 36 healthy adult subjects age-matched to previously studied LQT1 subjects will undergo 1) screening history, 2) two weeks of beta-blocker therapy ending in an exercise test, and 3) two weeks of placebo therapy ending in an exercise test. Beta blocker and placebo will be given in random order in a double-blind fashion. The QT response to exercise and recovery will be compared between drug-free and beta-blocker-treated states. These data will be compared to those previously collected for LQT1 subjects.

Implications. These results will provide new information about the effect of beta-blocker therapy on repolarization parameters in normal subjects, and will provide a context in which to interpret the previous findings that beta-blocker administration modifies the QT response to exercise in LQT1 subjects.

Conditions

  • Long QT Syndrome
  • Cardiac Repolarization

Interventions

DRUG

Placebo

Placebo will be given 1 pill daily for a week, then 2 pills daily, followed by the exercise test.

DRUG

Propranolol LA

Subjects will receive propranolol LA 80 mg one pill daily for 1 week then 2 pills daily for 1 week followed by exercise test.

Sponsors & Collaborators

  • MetroHealth Medical Center

    lead OTHER

Principal Investigators

  • Elizabeth S Kaufman, MD · MetroHealth Medical Center

Study Design

Allocation
RANDOMIZED
Purpose
BASIC_SCIENCE
Masking
DOUBLE
Model
CROSSOVER

Eligibility

Min Age
18 Years
Max Age
55 Years
Sex
ALL
Healthy Volunteers
Yes

Timeline & Regulatory

Start
2007-08-31
Primary Completion
2008-12-31
Completion
2008-12-31

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Read the full study record

This page highlights key information. For complete eligibility criteria, study locations, investigator contacts, and the full protocol, visit the original record on ClinicalTrials.gov.

View NCT00588965 on ClinicalTrials.gov