Elsevier

Heart Rhythm

Volume 2, Issue 6, June 2005, Pages 569-574
Heart Rhythm

Original-clinical
Inaccurate electrocardiographic interpretation of long QT: The majority of physicians cannot recognize a long QT when they see one

https://doi.org/10.1016/j.hrthm.2005.02.011Get rights and content

Background

Physicians in all fields of medicine may encounter patients with long QT syndrome (LQTS). It is important to define the percentage of physicians capable of distinguishing QT intervals that are long from those that are normal because LQTS can be lethal when left untreated.

Objectives

The purpose of this study was to define the percentage of physicians in the different disciplines of medicine who can recognize a long QT when they see one.

Methods

We presented the ECGs of two patients with LQTS and two healthy females to 902 physicians (25 world-renowned QT experts, 106 arrhythmia specialists, 329 cardiologists, and 442 noncardiologists) from 12 countries. They were asked to measure the QT, calculate the QTc (the QT interval corrected for the heart rate), and determine whether the QT is normal or prolonged.

Results

For patients with LQTS, >80% of arrhythmia experts but <50% of cardiologists and <40% of noncardiologists calculated the QTc correctly. Underestimation of the QTc of patients with LQTS and overestimation of the QTc of healthy patients were common. Interobserver agreement was excellent among QT experts, moderate among arrhythmia experts, and low among cardiologists and noncardiologists (kappa coefficient = 0.82, 0.44, and < 0.3, respectively). Correct classification of all QT intervals as either “long” or “normal” was achieved by 96% of QT experts and 62% of arrhythmia experts, but by only <25% of cardiologists and noncardiologists.

Conclusions

Most physicians, including many cardiologists, cannot accurately calculate a QTc and cannot correctly identify a long QT.

Section snippets

Methods

We presented four ECGs (traces of two patients with congenital LQTS and two healthy females) to 27 world-leading QT experts (arrhythmia specialists who have published clinical studies on the LQTS in peer-reviewed journals and are recognized for their clinical expertise). The range of QT and QTc values measured by the 25 QT experts who agreed to participate in this study were defined as “correct results.” We then presented the same ECGs to physicians from university hospitals in 12 countries

Measuring QT and calculating QTc

The first two traces (Figure 1A, 1B) are from patients with congenital LQTS. All QT experts (except for one who defined the QT of patient B as “borderline”) defined the QT interval of both patients as prolonged, with a QTc ranging from 460 to 530 ms (patient A) and from 454 to 520 ms (patient B). Most physicians in the other three categories measured the QT interval correctly but erred when calculating the QTc (Figure 2A, 2B): 89% of arrhythmia experts, 84% of cardiologists, and 65% of

Discussion

The LQTS can no longer be considered a medical curiosity. Advances in our understanding of the genetics and the pathophysiology of the LQTS as well as increased awareness by the medical community have led to increased recognition of the congenital form. Too often, however, there is a significant delay between the onset of symptoms and the eventual diagnosis. For example, the age at the onset of symptoms reported in the International LQTS Registry is 9 ± 6 years, whereas the age at diagnosis is

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