Clinical Review & Education

Challenges in Clinical Electrocardiography

Prolongation of a Prolonged QT A Case of an Undiagnosed Congenital Long QT Syndrome David Snipelisky, MD; Maegan Roberts, MS; Joseph Blackshear, MD

Case Presentation Several weeks after the birth of her first child, a woman in her 20s collapsed suddenly. She was found to be in ventricular fibrillation and was successfully cardioverted en route to her local hospital, where an amiodarone infusion was initiated. Discussion with the family revealed that she had a history of syncopal events, but each episode was self-limited, and therefore no workup was pursued. Family history was remarkable for syncope and seizures in a sibling. On examination, the patient was intubated and unresponsive to verbal or tactile stimuli. Cardiopulmonary examination revealed a regular rate and rhythm without murmurs, rubs, or gallops. The electrocardiogram (ECG) obtained on transfer to our facility is shown in the Figure, A, and indicates a mildly prolonged QTc of 466 milliseconds. Findings from a complete blood cell count, metabolic profile, and thyroid studies were within normal limits. Urine drug panel results were unremarkable. Lactic acid was elevated at 4.8 mmol/L (normal, 0.9-1.7 mmol/L). The amiodarone infusion was continued. Shortly after admission, the patient developed 2 unsustained episodes of polymorphic ventricular tachycardia and a third sustained episode, which converted to sinus rhythm after requiring emergency defibrillation. An additional amiodarone bolus of 150 mg was administered following the sustained episode. An amiodarone drip was continued at a rate of 1 mg/min, and another ECG was obtained 3 hours after admission, showing marked changes. Question: Based on the progression of the ECG findings from those in Figure, A, to those in Figure, B, what concern should be entertained with this patient?

Clinical Course The initial ECG illustrates a prolonged calculated QT interval of 466 milliseconds. Further prolongation of the QT interval to a manual measurement of 674 msec with amiodarone administration is important to recognize, since this can aggravate significantly the tendency to develop polymorphic ventricular tachycardia and also raises the question of underlying congenital long QT syndrome. Following administration of amiodarone, the patient developed T-wave alternans. This finding is associated with a high predisposition to ventricular arrhythmias, including polymorphic ventricular tachycardia degenerating into ventricular fibrillation, as in this case, and sudden cardiac death. Within the first 36 hours of admission, the patient experienced 5 additional episodes of ventricular arrhythmias, all requiring immediate defibrillation. Analysis of the ECG following defibrillation confirmed persistence of the prolonged QT interval. A total of 4400 mg of amiodarone, excluding a loading dose given jamainternalmedicine.com

at the first facility, was administered before prolonged QT was suspected as the cause. The amiodarone level 4 days after admission showed a therapeutic value of 4.1 μg/mL (normal, 1.5-5.0 μg /mL). An echocardiogram performed on hospital day 4 revealed a diminished left ventricle ejection fraction of 35% with global left ventricular hypokinesis, likely as a result of the numerous attempts at defibrillation. On evaluation and comparison of serial ECGs throughout the hospitalization, and after an additional ventricular fibrillation arrest on hospital day 4, amiodarone treatment was discontinued, and lidocaine was administered along with high-dose magnesium to maintain a level greater than 2.0 mEq/L. Treatment with β-blocker was continued, and lisinopril and spironolactone were added to the regimen. A dual-chamber implantable cardiac defibrillator was placed on hospital day 6, and atrial pacing at 80 beats per minute was initiated. The patient’s neurologic deficits resolved completely and she was discharged home after 9 days. One month later the patient reported no episodes of arrhythmia or defibrillator discharge, and her functional status was at baseline. Genetic testing results became available 2 months after hospitalization and revealed the presence of KCNE1 mutation (long QT syndrome 5), a relatively rare autosomal dominant form of long QT syndrome. Single-gene testing of first-degree family members was recommended.

Discussion Amiodarone is a proven treatment long recommended in American Heart Association guidelines for the management of cardiac arrest, and its reflex administration during ventricular arrhythmia arrest is illustrated by the present case.1 However, in rare circumstances, notably congenital long QT syndromes,2-4 amiodarone may aggravate ventricular arrhythmias. A history of syncope in a younger person with a family history of syncope and/or sudden death were clues to the presence of congenital long QT syndrome in our patient. The most feared complication of long QT syndromes is the development of torsades de pointes, a type of polymorphic ventricular tachycardia with degeneration to ventricular fibrillation and sudden cardiac death.5,6 Even in the absence of congenital long QT syndromes, prolonged QT interval and arrhythmias are associated with numerous drugs, including commonly used antibiotics such as macrolides and fluoroquinolones and also selective serotonin reuptake inhibitors.5 Associated with acquired long QT syndromes, bradycardia-dependent torsades de pointes can occur when a QRS complex falls within the T wave of a prior beat as a result of a pause. Therefore, it is important to consider initiation of temporary atrial pacing or medications such as isoproterenol until a permanent pacemaker can be implanted, although the use of isoproterenol should be used with caution in JAMA Internal Medicine November 2014 Volume 174, Number 11

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Clinical Review & Education Challenges in Clinical Electrocardiography

Prolongation of a Prolonged QT

Figure. Electrocardiograms (ECGs) Before and After Amiodarone Administration A ECG obtained at admission

QTc = 466 ms I

V1

V4

II

aVL

V2

V5

III

aVF

V3

V6

V1

II

V5 B

ECG obtained 3 hours after admission

I

QTc = 674 ms

V1

V4

II

aVL

V2

V5

III

aVF

V3

V6

A, The ECG obtained on admission indicates a mildly prolonged QTc of 466 milliseconds (ms). B, Three hours later, after administration of an amiodarone drip at a rate of 1 mg/min, another ECG was obtained and showed marked changes. In both panels, the red arrowheads serve to highlight the boxed areas of interest and the red interval measurements.

V1

II

V5

patients with either known or suspected coronary artery disease.6 Our patient’s dual-chamber defibrillator was used in this manner. Genetic testing, while not immediately helpful in our case, subsequently provided clarity as to the true diagnosis and allowed us to recommend lifelong avoidance of medications that prolong the QT interval (www.qtdrugs.org) and to perform single-gene testing in first-degree relatives. The importance of family history and potential adverse effects of medications in patients with cardiac arrest and prolonged QT on ECG cannot be overemphasized. Although amiodarone is a first-line medication for tachyarrhythmia, it is important to understand the potential harm due to further prolongation of the QT interval in the rare instance of first clinical presentation of congenital prolonged QT syndrome. 1832

Take-Home Points • In young patients with sudden cardiac death, a thorough history, family history, and physical examination are essential. Review of the ECG, with manual measurement of the QT interval, should be undertaken, and genetic testing of the patient and first-degree family members is recommended. • Exacerbation of tachyarrhythmic events, especially polymorphic ventricular tachycardia, associated with amiodarone administration should suggest the possibility that congenital or drug-related long QT syndrome is present and mandates the implementation of alternate anti-arrhythmic strategies. • The presence of T-wave alternans is a strong predictor of proarrhythmic states, and a thorough evaluation is essential to identify the underlying cause.

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Prolongation of a Prolonged QT

Challenges in Clinical Electrocardiography Clinical Review & Education

ARTICLE INFORMATION

REFERENCES

Author Affiliations: Department of Medicine, Mayo Clinic, Jacksonville, Florida (Snipelisky); Division of Cardiovascular Diseases, Mayo Clinic, Jacksonville, Florida (Roberts, Blackshear).

1. Morrison LJ, Deakin CD, Morley PT, et al; Advanced Life Support Chapter Collaborators. Part 8: advanced life support: 2010 international consensus on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations. Circulation. 2010;122 (16)(suppl 2):S345-S421.

Corresponding Author: David Snipelisky, MD, Mayo Clinic, Department of Medicine, 4500 San Pablo Rd, Jacksonville, FL 32224 (Snipelisky.david @mayo.edu). Section Editors: Jeffrey Tabas, MD; Gregory M. Marcus, MD; Nora Goldschlager, MD; Elsayed Z. Soliman, MD, MSc, MS. Published Online: September 1, 2014. doi:10.1001/jamainternmed.2014.4047. Conflict of Interest Disclosures: None reported.

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2. Kawaguchi T, Takasugi N, Kubota T, et al. In-hospital monitoring of T-wave alternans in a case of amiodarone-induced torsade de pointes: clinical and methodologic insights. Europace. 2012;14(9): 1372-1374.

hastens proarrhythmic response. J Cardiovasc Electrophysiol. 2002;13(6):629. 4. Lim HE, Pak HN, Ahn JC, Song WH, Kim YH. Torsade de pointes induced by short-term oral amiodarone therapy. Europace. 2006;8(12):10511053. 5. Khan IA. Long QT syndrome: diagnosis and management. Am Heart J. 2002;143(1):7-14. 6. Kay GN, Plumb VJ, Arciniegas JG, Henthorn RW, Waldo AL. Torsade de pointes: the long-short initiating sequence and other clinical features: observations in 32 patients. J Am Coll Cardiol. 1983; 2(5):806-817.

3. Tomcsányi J, Somlói M, Horváth L. Amiodarone-induced giant T wave alternans

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Prolongation of a prolonged QT: a case of an undiagnosed congenital long QT syndrome.

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