QT Interval Variability and Adaptation to Heart Rate Changes in Patients with Long QT Syndrome

JAN NĚMEC; MARIE BUNCOVÁ; VLADIMIR SHUSTERMAN; BRUCE WINTER; WIN-KUANG SHEN; MICHAEL J ACKERMAN

doi:10.1111/j.1540-8159.2009.02179.x

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QT Interval Variability and Adaptation to Heart Rate Changes in Patients with Long QT Syndrome

Journal article

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QT Interval Variability and Adaptation to Heart Rate Changes in Patients with Long QT Syndrome

JAN NĚMEC, MARIE BUNCOVÁ, VLADIMIR SHUSTERMAN, BRUCE WINTER, WIN-KUANG SHEN and MICHAEL J ACKERMAN

Pacing and clinical electrophysiology, Vol.32(1), pp.72-81

Received July 4, 2008; revised September 1, 2008; accepted October 4, 2008.

01/2009

DOI: 10.1111/j.1540-8159.2009.02179.x

PMID: 19140916

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Abstract

Background: Increased QT variability (QTV) has been reported in conditions associated with ventricular arrhythmias. Data on QTV in patients with congenital long QT syndrome (LQTS) are limited. Methods: Ambulatory electrocardiogram recordings were analyzed in 23 genotyped LQTS patients and in 16 healthy subjects (C). Short-term QTV was compared between C and LQTS. The dependence of QT duration on heart rate was evaluated with three different linear models, based either on the RR interval preceding the QT interval (RR(0)), the RR interval preceding RR(0) (RR(-1)), or the average RR interval in the 60-second period before QT interval (mRR). Results: Short-term QTV was significantly higher in LQTS than in C subjects (14.94 +/- 9.33 vs 7.31 +/- 1.29 ms; P < 0.001). It was also higher in the non-LQT1 than in LQT1 patients (23.00 +/- 9.05 vs 8.74 +/- 1.56 ms; P < 0.001) and correlated positively with QTc in LQTS (r = 0.623, P < 0.002). In the C subjects, the linear model based on mRR predicted QT duration significantly better than models based on RR(0) and RR(-1). It also provided better fit than any nonlinear model based on RR(0). This was also true for LQT1 patients. For non-LQT1 patients, all models provided poor prediction of QT interval. Conclusions: QTV is elevated in LQTS patients and is correlated with QTc in LQTS. Significant differences with respect to QTV exist among different genotypes. QT interval duration is strongly affected by noninstantaneous heart rate in both C and LQT1 subjects. These findings could improve formulas for QT interval correction and provide insight on cellular mechanisms of QT adaptation.

long QT syndrome

QT correction

QT variability

Details

Title: Subtitle: QT Interval Variability and Adaptation to Heart Rate Changes in Patients with Long QT Syndrome
Creators: JAN NĚMEC - Cardiovascular Institute, University of Pittsburgh, Pittsburgh, Pennsylvania
MARIE BUNCOVÁ - Division of Cardiology, Institute for Clinical and Experimental Medicine, Prague, Czech Republic
VLADIMIR SHUSTERMAN - Cardiovascular Institute, University of Pittsburgh, Pittsburgh, Pennsylvania
BRUCE WINTER - Division of Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota
WIN-KUANG SHEN - Department of Internal Medicine/Division of Cardiovascular Diseases
MICHAEL J ACKERMAN - Cardiovascular Genetics Laboratory/Division of Cardiovascular Diseases
Resource Type: Journal article
Publication Details: Pacing and clinical electrophysiology, Vol.32(1), pp.72-81
Edition: Received July 4, 2008; revised September 1, 2008; accepted October 4, 2008.
DOI: 10.1111/j.1540-8159.2009.02179.x
PMID: 19140916
NLM abbreviation: Pacing Clin Electrophysiol
ISSN: 0147-8389
eISSN: 1540-8159
Publisher: Blackwell Publishing Inc
Number of pages: 10
Language: English
Date published: 01/2009
Academic Unit: Cardiovascular Medicine; Internal Medicine
Record Identifier: 9984094372502771

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