Unmasking Long QT Syndrome in the Emergency Department: A Case Report

Introduction

Long QT syndrome (LQTS) is an uncommon disorder that can lead to potentially life-threatening dysrhythmias. LQTS can be genetic, acquired, or both.

Case Report

A 44-year-old female with well-controlled hypertension and asthma presented with chest tightness. An initial electrocardiogram yielded a normal corrected QT interval of 423 milliseconds (ms) (normal <480 ms in females). Albuterol was administered and induced agitation, tremulousness, and tachycardia. Follow-up electrocardiograms demonstrated extreme prolongation of the corrected QT interval to 633 ms and morphology change of the T wave. Lab values were later notable for hypokalemia and hypomagnesemia, attributable to a recently started thiazide diuretic. The patient was ultimately diagnosed with congenital LQTS after initial unmasking by albuterol in the emergency department.

Conclusion

LQTS can be unmasked or exacerbated by electrolyte abnormalities and QT prolonging medications.

A case of long QT syndrome: challenges on a bumpy road

Beta‐agonist treatment during pregnancy may unmask the diagnosis of long QT syndrome. The QT prolongation can result in functional AV block. A history of seizure and/or sudden death in a family member should raise suspicion of ventricular tachycardia. More than one mutation may coexist. Refusal of beta‐blocker therapy complicates risk stratification.

Brugada syndrome: an update

More than 20 years have passed since the description of Brugada syndrome as a clinical entity. The original case series depicted patients who all had coved ST-segment elevation in the right precordial leads, associated with a high risk of sudden death and no apparent structural heart disease. As subsequent registry data were published, it became apparent that the spectrum of risk is wide, with the majority of patients classified as low risk. Two consensus documents have been published that will continue to be updated. Despite intense research efforts, many controversies still exist over its pathophysiology and the risk stratification for sudden death. Management continues to be challenging with a lack of drug therapy and high complication rates from implantable cardioverter defibrillators. In this review, we highlight the current state-of-the-art therapies and their controversies.

Cardiac syncope

Clinicians who diagnose and manage epilepsy frequently encounter diagnoses of a nonneurological nature, particularly when assessing patients with transient loss of consciousness (T-LOC). Among these, and perhaps the most important, is cardiac syncope. As a group, patients with cardiac syncope have the highest likelihood of subsequent sudden death, and yet, unlike sudden unexpected death in epilepsy (SUDEP) for example, it is the norm for these tragic occurrences to be both easily predictable and preventable. In the 12 months following initial presentation with cardiac syncope, sudden death has been found to be 6 times more common than in those with noncardiac syncope (N Engl J Med 309, 1983, 197). In short, for every patient seen with T-LOC, two fundamental aims of the consultation are to assess the likelihood of cardiac syncope as the cause, and to estimate the risk of future sudden death for the individual. This article aims to outline for the noncardiologist how to recognize cardiac syncope, how to tell it apart from more benign cardiovascular forms of syncope as well as from seizures and epilepsy, and what can be done to predict and prevent sudden death in these patients. This is achieved through the assessment triad of a clinical history and examination, risk stratification, and 12-lead electrocardiography (ECG).

Genetic testing for long QT syndrome and the category of cardiac ion channelopathies

Cardiac ion channel mutational analysis is a category of genetic testing used in clinical practice for determining the status of long QT syndrome, short QT syndrome, catecholaminergic polymorphic ventricular tachycardia, and Brugada syndrome genes in blood, saliva, or tissue from patients and family members at risk for cardiac events such as syncope and sudden death. Such testing is most informative following careful phenotypic characterization. Individuals with ion channelopathies may benefit from prevention (avoidance of triggers and predisposing drugs) and treatment (e.g., beta blocker therapy, implantable cardioverter-defibrillator (ICD) placement) modalities.

Inherited arrhythmia syndromes

Inherited arrhythmia syndromes are an important contributor to sudden death in children and adults. These cardiac ‘channelopathies’ lead to arrhythmias in a structurally normal myocardium and are often variable in penetrance and expressivity. The clinical features and management options for the four major channelopathies are outlined.

Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy is a myocardial disease characterized by myocardial hypertrophy, disorganization of cardiac myocytes, and fibrosis. Twenty-five percent of patients have a dynamic left ventricular outflow tract gradient caused by the combined effects of rapid ventricular ejection, a narrowed outflow tract, and systolic anterior motion of the mitral valve. Most cases are caused by mutations in genes that encode cardiac sarcomeric proteins. Patients present at all ages with chest pain, dyspnea, palpitations, and syncope. The most important complications of the disease are sudden cardiac death, heart failure, and thromboembolism. The principal aims of management are the alleviation of symptoms and the prevention of sudden death. In patients with substantial left ventricular outflow tract obstruction, interventions that reduce the magnitude of the outflow tract gradient (disopyramide, verapamil, β-blockade, alcohol ablation of the interventricular septum, dual-chamber pacing, and surgery) often improve symptoms. Therapeutic options in patients without left ventricular outflow tract obstruction are more limited. Clinical risk stratification is used to estimate the risk of sudden death and to target effective prophylactic treatment with an implantable cardioverter defibrillator.