Case Report
Am Heart Hosp J. 2010;8(1):58–62
Case Illustrations of Long QT Syndrome Omar Abdul Razakjr, MRCP (UK),1,2
Seow Swee Chong, MRCP (UK)2
Yeo Wee Tiong, MRCP (UK),2 and Singh Devinder, MRCP (UK)2
Long QT syndrome (LQTS) is a rare potentially life-threatening condition. Physicians must remain vigilant and consider LQTS as a possible etiology in patients with a history of syncope. Prolongation of the QT interval on electrocardiogram (ECG) is an essential component for the diagnosis of LQTS, despite the limitations of this technique. Experience of analyzing the ECG and calculating corrected QTc still remain relevant and are the mainstay diagnostic tools. Often, the first sign of the problem is observed after careful evaluation of the resting ECG for the hallmark of the disorder. Unfortunately, more than 60% of physicians—even cardiologists—have been known to misinterpret the QT interval on ECG. The cases discussed in this article highlight the variable clinical presentation of prolonged QT interval and the need to be highly vigilant in clinical evaluation.
T
he term ‘torsades de pointes,’ coined in 1966 to describe the peculiar appearance of a ventricular tachycardia occurring in an elderly woman with heart block, is often translated as a ‘twisting of the points,’ referring to the beat-to-beat changes in the QRS axis.1 Congenital syndromes involving QT-interval prolongation and syncope or sudden death were first described in the late 1950s and early 1960s.1–3
However, the congenital long QT
syndrome (LQTS) is rare, while the acquired LQTS, particularly associated with use of various drugs, is common. The few electrocardiographically documented cases of syncope or sudden death in patients with a congenital LQTS have been characterized by torsades de pointes.4
Because of
the malignant clinical features of LQTS and the need for a prompt diagnosis that leads to effective treatment, every physician should be aware of its varied clinical presentation and also be able to recognize LQTS on electrocardiogram (ECG). Often, the first sign of the problem is observed on careful evaluation of the resting ECG for the hallmark of the disorder. Unfortunately, more than 60% of physicians— even cardiologists—have been known to misinterpret the QT interval on ECG.5
In this article we present three cases of
prolonged QT interval presented to National University Hospital, Singapore, with the aim of increasing awareness and knowledge about LQTS within the general medical community. These cases highlight the variable clinical
presentation of prolonged QT interval and the need to be highly vigilant in clinical evaluation.
Clinical Cases
The first case is an octogenarian woman hospitalized for frequent falls due to syncope and knee pain under the orthopaedics team. She has a past medical history of hypertension and paroxysmal atrial fibrillation. Her medications include tramadol hydrochloride, hydro- chlorthiazide, and aspirin. Clinical examination was otherwise unremarkable except for the clinical findings of osteoarthritis of the bilateral knee joints. Laboratory investigation showed hypokalemia (serum potassium 2.9mmol/l), which was attributed to hydrochlorthiazide. The electrocardiogram showed sinus rhythm and prolonged QTc of 592 milliseconds, but this abnormality went unrecognized by the attending physician (see Figure 1). The morning prior to her discharge she experienced sudden cardiovascular collapse. The cardiac rhythm showed ventricular fibrillation that was successfully defibrillated. She was subsequently managed in the intensive care unit. Cardiac monitoring showed recurrent runs of polymorphic ventricular tachycardia demonstrating pause dependence that was typical of drug-induced prolongation of QT interval (see Figure 2). She continued to have recurrent runs of polymorphic ventricular tachycardia in spite of correction
• 1. Raffles Heart Centre, Raffles Hospital, Singapore; 2. Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore
• Correspondence: Omar Abdul Razakjr, MRCP (UK), Raffles Heart Centre, 585 North bridge Road, #12-00 Raffles Hospital, Singapore 188770. E:
razak13@yahoo.com.sg
58 Long QT Syndrome Summer 2010
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