What question did this study set out to answer?

This study aims to compare the influences of sympathetic stimulation on QTc intervals across different genotypes of congenital long QT syndrome.

April 24, 2026

Gene-specific response of dynamic ventricular repolarization to sympathetic stimulation in LQT1, LQT2 and LQT3 forms of congenital long QT syndrome

Key Result

Sympathetic stimulation elicits distinct dynamic ventricular repolarization responses in LQT1, LQT2, and LQT3 syndromes, potentially explaining why cardiac event triggers differ by genotype.

Key Points

This study aims to compare the influences of sympathetic stimulation on QTc intervals across different genotypes of congenital long QT syndrome.
12-lead electrocardiograms recorded in patients before and after epinephrine administration.
Epinephrine was given as a bolus injection followed by continuous infusion.
QT intervals were measured semi-automatically, and QTc was calculated using Bazett's method.
In LQT1 patients, QTc increased from 477 ms to 631 ms (P<0.0005) with +32% prolongation.
In LQT2 patients, QTc rose from 502 ms to 620 ms (P<0.0005) but returned to baseline of 531 ms.
LQT3 and control groups showed less QTc prolongation, with LQT3 increasing from 478 ms to 532 ms (P<0.05) and returning to baseline.

Structured PICO

Does the dynamic response of ventricular repolarization to sympathetic stimulation differ between LQT1, LQT2, and LQT3 forms of congenital long QT syndrome?

Population

Patients with LQT1, LQT2, and LQT3 forms of congenital long QT syndrome

Intervention

Sympathetic stimulation

Comparator

Comparison between LQT1, LQT2, and LQT3 genotypes

Outcome

Dynamic response of ventricular repolarizationsurrogate

Differences in dynamic ventricular repolarization response to sympathetic stimulation may explain why cardiac event triggers vary among LQT1, LQT2, and LQT3 genotypes.

Main Result

Absolute Event Rate: 0% vs 0%

Abstract

AIMS: Differences in the sensitivity of the genotype of the congenital long QT syndrome to sympathetic stimulation have been suggested. This study compared the influence of sympathetic stimulation on continuous corrected QT (QTc) intervals between LQT1, LQT2 and LQT3 forms of the congenital long QT syndrome. METHODS AND RESULTS: We recorded a 12-lead electrocardiogram continuously before and after bolus injection (0.1 microg x kg(-1)) of epinephrine followed by continuous infusion (0.1 microg x kg(-1) min(-1)) in 12 LQT1, 10 LQT2, 6 LQT3, and 13 control patients. The QT intervals and previous RR intervals of all beats were measured semi-automatically, and the QTc intervals of all beats were calculated by Bazett's method. The dynamic response of the RR interval to epinephrine was no different between the four groups. The QTc was prolonged remarkably (477+/-42 to 631+/- 59 ms; P<0.0005, % delta prolongation =+32%) as the RR was maximally decreased (at peak of epinephrine), and remained prolonged at steady state conditions of epinephrine (556+/-56 ms; P<0.0005 vs baseline, +17%) in LQT1 patients. Epinephrine also prolonged the QTc dramatically (502+/-23 to 620+/-39 ms; P<0.0005, +24%) at peak of epinephrine in LQT2 patients, but this shortened to baseline levels at steady state (531+/-25 ms; P=ns vs baseline, +6%). The QTc was much less prolonged at peak of epinephrine in LQT3 (478+/-44 to 532+/-41 ms; P<0.05, +11%) and controls (394+/-21 to 456+/-18 ms; P<0.0005, +16%) than in LQT1 and LQT2 patients, and shortened to the baseline levels (LQT3; 466+/-49 ms, -3%, controls; 397+/-16 ms, +1%; P=ns vs baseline) at steady state. CONCLUSION: Our data suggest that the dynamic response of ventricular repolarization to sympathetic stimulation differs between LQT1, LQT2 and LQT3 syndromes, and may explain why the trigger of cardiac events differs between the genotypes.