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This Article Full Text (PDF) Free All Versions of this Article: chest.06-2133v1 132/1/246    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to My Personal Article Archive Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Reinig, M. G Articles by Engel, T. R Search for Related Content PubMed PubMed Citation Articles by Reinig, M. G Articles by Engel, T. R

The Shortage of Short QTs

Department of Medicine, Cooper University Hospital, UMDNJ/Robert Wood Johnson Medical School ¹Cooper Plaza, Camden, NJ 08103

engel-toby{at}cooperhealth.edu

Abstract

BackgroundSyncope or sudden death has been associated with a short QT interval (QTc <300 ms), the so-called Short QT Syndrome. The current prevalence of this syndrome is unknown. The aim of this study was to evaluate the prevalence of a short QT intervals (QTc <300ms) in a general hospital population.

MethodsWe retrospectively queried 479,120 consecutive electrocardiograms(ECGs) archived by a MAC 5000^® over a 16 year period. We examined the distribution of QT intervals in our population from 150 randomly selected normal ECGs, excluding patients taking medication known to prolong the QT interval.

ResultsFrom 1988 to 2004, 479,120 ECGs from 106,432 patients were analyzed by the MAC 5000^®, which reported 215 tracings with QTc <300 ms. Each ECG was then measured manually and no QTc <300 ms was validated: 67% were found to be in error because of pacemaker artifact, 17% had supraventricular tachycardia with inaccurate detection of T wave offset, and 16% were found to have an error in cycle length calculation. Therefore, not one of the 106,432 patients was found to have a QTc <300 ms. Our average QTc =430 ± 19 SD, 95% confidence interval for QTc =392-468 ms. QTc <300 ms would then reflect >5 SD shorter than the mean QTc.

ConclusionsShort QTc reported by an ECG computer was inaccurate and required manual correction.

Short QT syndrome, defined as QTc 300 ms, is rare. We were unable to find one patient amongst a population >100,000 patients with a true QTc <300 ms.

Key Words: Arrhythmias • ECG • Electrophysiology • QT intervals • Sudden death