Torsades de pointes and self‐terminating ventricular fibrillation in a prescription methadone user

Abstract

SummaryMethadone is known to prolong the QT interval and precipitate torsades de pointes. A 54-year-old prescription methadone user with hypokalaemia was referred to Critical Care with acute confusion and respiratory distress. Alcohol withdrawal was the presumed precipitant. The real precipitant only became evident on analysis of a 24-h ECG (Holter monitor) attached to the patient at the time. The patient had suffered prolonged (10 min) ventricular arrhythmias including torsades de pointes and self-terminating ventricular fibrillation. The patient made a full recovery. Risk factors for acquired long QT syndrome and the treatment of torsades de pointes are discussed. Methadone is a synthetic opioid used in the treatment of severe pain and opioid addiction. In 2005, there were over 88 000 prescriptions for methadone dispensed in the community in England [1]. It is also a drug of abuse with approximately 11 000 16-59-year-olds in England and Wales using it in the year 2004 ⁄ 5 [2]. In 2002, a case series first established the association between methadone and acquired long QT syndrome with its potentially lifethreatening sequelae torsades de pointes [3]. This association is now well established. Case reportA 54-year-old man presented to the emergency department with epigastric pain and vomiting. No cardiovascular symptoms were described. Past medical history included chronic pancreatitis, alcoholism, hypertension and intravenous drug use until 2 years previously. He was taking methadone 60 mg orally per day. Examination demonstrated epigastric tenderness but no cardiovascular or other abnormality. Serum potassium was 2.6 mmol.l Other routine blood tests including amylase and magnesium were normal.ECG showed sinus rhythm, prolonged QT interval (QTc ¼ 0.64 s), peaked P waves and biphasic T waves (Fig. 1). No previous ECG was available for comparison. A diagnosis of pain related to chronic pancreatitis and vomiting-induced hypokalaemia was made. He was placed nil by mouth, given intramuscular morphine for analgesia, anti-emetics and intravenous fluids with potassium supplementation. Methadone was continued intravenously.An echocardiogram and 24-h ambulatory ECG (Holter monitor) were organised in view of the abnormal ECG and a computed tomography (CT) of the abdomen requested. The patient's symptoms settled within 48 h. Echocardiogram demonstrated mild left ventricular hypertrophy with normal function. CT abdomen showed only an atrophic pancreas. Sixty hours after admission (around 04.00 h), the patient became acutely confused on the medical ward. The 24-h ECG was in progress at this time. Following review by the medical team, a diagnosis of alcohol withdrawal was made and intravenous lorazepam administered. Over the following 6 h the patients remained agitated and confused, requiring further doses of lorazepam. He became increasingly tachypnoeic and hypoxic and a referral to Critical Care was made.On arrival the patient's observations were as follows: saturation 77% on 15 l face mask oxygen, respiratory rate 40 breath...

QT Interval Screening in Methadone Maintenance Treatment: Report of a SAMHSA Expert Panel

“…For example, a 2007 article by Atkinson and colleagues reported QT normalization when the methadone was discontinued or the dose reduced. 71 …”

Cardiotoxicity of Oral Methadone as an Analgesic–-Recommendations for Safe Use

“…38,[45][46][47][48][49][50][51][52][53][54][55][56][57] A minority of clinical data have involved the adult patient population undergoing methadone maintenance therapy (N = 46). 34, However, the majority of study data providing the epidemiology of methadone-associated QTc interval prolongation and applied correlational and regression analyses have been obtained in patients undergoing methadone maintenance therapy for opioid addiction (Table 4).…”

Degenerating Regenerating Torsades de Pointes

“…Ventricular fibrillation (VF) usually ends in death. Isolated case reports describe the uncommon occurrence of spontaneous termination . Torsades de pointes (TdP), a peculiar form of polymorphic ventricular tachycardia (VT) associated with a prolonged QT interval on the surface electrocardiogram, most often spontaneously terminates; less commonly it degenerates into VF.…”

“…Isolated case reports describe the uncommon occurrence of spontaneous termination. [1][2][3][4] Torsades de pointes (TdP), a peculiar form of polymorphic ventricular tachycardia (VT) associated with a prolonged QT interval on the surface electrocardiogram, most often spontaneously terminates 5 ; less commonly it degenerates into VF. We present a case of TdP degenerating into VF, regenerating back to TdP and finally spontaneously terminating.…”