A 42-year-old man comes to the emergency department due to an episode of syncope. He was standing in his kitchen this morning when he felt palpitations for about 3 seconds; the next thing he remembers is waking up on the floor. The patient has had intermittent palpitations for the last few weeks, sometimes with associated lightheadedness. He has no significant medical history other than chronic lower back pain that began following a fall from a ladder 3 years ago. The patient fractured several lumbar vertebrae in that fall and required a surgical lumbar fusion. His back pain was uncontrolled with conservative measures, and he has been treated with escalating doses of methadone for the past year. He does not smoke or drink alcohol. The patient has a remote history of intravenous heroin abuse but has not used it for 20 years. He has no family history of early-onset heart disease, blood clots, or sudden death. Blood pressure is 120/70 mm Hg when supine and 125/75 mm Hg when standing. Physical examination is unremarkable. Which of the following ECG findings is most likely in this patient?

Question

A 42-year-old man comes to the emergency department due to an episode of syncope.  He was standing in his kitchen this morning when he felt palpitations for about 3 seconds; the next thing he remembers is waking up on the floor.  The patient has had intermittent palpitations for the last few weeks, sometimes with associated lightheadedness.  He has no significant medical history other than chronic lower back pain that began following a fall from a ladder 3 years ago.  The patient fractured several lumbar vertebrae in that fall and required a surgical lumbar fusion.  His back pain was uncontrolled with conservative measures, and he has been treated with escalating doses of methadone for the past year.  He does not smoke or drink alcohol.  The patient has a remote history of intravenous heroin abuse but has not used it for 20 years.  He has no family history of early-onset heart disease, blood clots, or sudden death.  Blood pressure is 120/70 mm Hg when supine and 125/75 mm Hg when standing.  Physical examination is unremarkable.  Which of the following ECG findings is most likely in this patient?

Quizplus · Accepted Answer

11ec160b_3b90_8174_9249_6bf9620a72e2_MD0001_00 This patient most likely has QT interval prolongation, a common adverse effect of methadone. QT interval prolongation is the ECG manifestation of delayed ventricular repolarization, which occurs due to impairment of the voltage-gated potassium channels that control the delayed rectifier potassium current. Significant slowing of ventricular repolarization can trigger torsade de pointes (TdP), a form of polymorphic ventricular tachycardia named for a repetitive "twisting of the peaks" pattern. TdP is a serious arrhythmia that can cause palpitations, lightheadedness, syncope, and sudden cardiac death (SCD). Many medications, including methadone, are known to inhibit the delayed rectifier potassium current to prolong the QT interval and predispose to TdP. Methadone undergoes slow and variable hepatic clearance, making consistent avoidance of toxic blood levels challenging; therefore, the use of high doses of methadone increases the risk of QT interval prolongation and TdP. (Choice A) Advanced atrioventricular block (ie, Mobitz type II or complete atrioventricular block) can present with syncope. Common causes include infection (eg, Lyme disease), ischemia, and medications (eg, beta blockers, nondihydropyridine calcium channel blockers). Methadone is not associated with atrioventricular block. (Choice B) Deep Q waves on ECG typically represent a previous myocardial infarction (MI). Patients with a history of MI are at risk for monomorphic ventricular tachycardia causing syncope or SCD, but a prior MI is unlikely in this relatively young patient without significant cardiovascular risk factors (eg, hypertension, smoking, family history). (Choice D) Sinus pauses occur with sick sinus syndrome, which most commonly results from age-related degeneration of the conduction system. Affected patients are usually age >65 and may experience progressive fatigue and episodes of syncope. (Choice E) Ventricular preexcitation is recognized by a slurred upslope of the QRS complex (delta wave) on ECG. Patients with this characteristic Wolff-Parkinson-White (WPW) pattern may develop paroxysmal supraventricular tachycardia (ie, WPW syndrome), which can present with syncope or SCD. However, the onset of WPW syndrome is usually age <40, and this patient's methadone use makes a prolonged QT interval more likely. Educational objective: Methadone slows the delayed rectifier potassium current responsible for ventricular repolarization, and high doses are associated with QT interval prolongation. QT interval prolongation predisposes to the development of torsade de pointes, a serious ventricular arrhythmia that can cause syncope and sudden cardiac death. __________ References: Methadone, QTc prolongation and torsades de pointes: current concepts, management, and a hidden twist in the tale? (http://www.ncbi.nlm.nih.gov/pubmed/24653586)

A 42-Year-Old Man Comes to the Emergency Department Due to an Episode