Abnormal atrial and ventricular repolarisation resembling myocardial injury after tricyclic antidepressant drug intoxication

Physiologically based pharmacokinetic-quantitative systems toxicology and safety (PBPK-QSTS) modeling approach applied to predict the variability of amitriptyline pharmacokinetics and cardiac safety in populations and in individuals

The physiologically based pharmacokinetic (PBPK) models allow for predictive assessment of variability in population of interest. One of the future application of PBPK modeling is in the field of precision dosing and personalized medicine. The aim of the study was to develop PBPK model for amitriptyline given orally, predict the variability of cardiac concentrations of amitriptyline and its main metabolite-nortriptyline in populations as well as individuals, and simulate the influence of those xenobiotics in therapeutic and supratherapeutic concentrations on human electrophysiology. The cardiac effect with regard to QT and RR interval lengths was assessed. The Emax model to describe the relationship between amitriptyline concentration and heart rate (RR) length was proposed. The developed PBPK model was used to mimic 29 clinical trials and 19 cases of amitriptyline intoxication. Three clinical trials and 18 cases were simulated with the use of PBPK-QSTS approach, confirming lack of cardiotoxic effect of amitriptyline in therapeutic doses and the increase in heart rate along with potential for arrhythmia development in case of amitriptyline overdose. The results of our study support the validity and feasibility of the PBPK-QSTS modeling development for personalized medicine.

Cardiac Troponin T and NT-proBNP as Biomarkers of Early Myocardial Damage in Amitriptyline-Induced Cardiovascular Toxicity in Rats

The main objective of this study was to investigate whether cardiac troponin (cTn) and N-terminal, protein B-type natriuretic peptide (NT-proBNP) can be useful as indicators for amitriptyline cardiotoxicity which is a known drug having sublethal toxic cardiac effects. At the same time, this study looked at detecting potential histopathological changes specific to irreversible cardiac injuries in a rat model of amitriptyline cardiotoxicity. Male Wistar rats were randomly divided into 2 groups, control (saline) group and amitriptyline group (100 mg/kg body weight intraperitoneally, equivalent for lethal dose at 50%). Blood was collected 30 minutes after the administration. The cTn was measured using 3 different methods (2 methods designed for human use and a sandwich enzyme immunoassay specific for rat cTnT). The brain natriuretic peptide was measured by 2 different methods (1 for human and 1 specific for rats). Electrocardiography showed that the QRS complex ( P < .0001) and the QT interval ( P = .002) were significantly prolonged for amitriptyline-treated animals. Troponin T and NT-proBNP had significantly increased levels in all the rats but showed positive results only when using rat-specific quantitative measurement. In certain rats, the histopathological examination identified a few small foci of acute myocardial necrosis. In conclusion, elevation of cTnT and NT-proBNP are early indicators of cardiotoxicity, yet the significance of irreversible myocardial damage in amitriptyline cardiotoxicity needs to be further understood.

Early and prolonged ECG alterations resembling a myocardial injury after severe amitriptyline poisoning

Evidence of cardiovascular toxicity is present in the majority of tricyclic antidepressant overdoses. We report the case of a 63-year-old woman admitted to our department with a severe amitriptyline poisoning. The ECG at admission showed a pattern mimicking an acute anteroseptal subepicardial infarction. This pattern persisted for 11 days. Myocardial enzymes and echocardiographic findings never confirmed an ischemic event. At discharge, the ECG returned normal without cardiac or neurologic sequelae. Our experience suggest that after severe tricyclic antidepressant ingestion, ECG alterations resembling myocardial injury may occur early and last for a longer period than previously reported.

Acute Myocardial Infarction Associated with Amitriptyline Overdose

Tricyclic antidepressant overdose is known to cause cardiopulmonary and central nervous system complications. As with other cardiovascular complications, amitriptyline toxicity may cause acute myocardial infarction. This paper reports the case of a young female with acute myocardial infarction as a novel consequence of tricyclic antidepressant overdose.

Tricyclic antidepressant poisoning : cardiovascular toxicity

Tricyclic antidepressants remain a common cause of fatal drug poisoning as a result of their cardiovascular toxicity manifested by ECG abnormalities, arrhythmias and hypotension. Dosulepin and amitriptyline appear to be particularly toxic in overdose. The principal mechanism of toxicity is cardiac sodium channel blockade, which increases the duration of the cardiac action potential and refractory period and delays atrioventricular conduction. Electrocardiographic changes include prolongation of the PR, QRS and QT intervals, nonspecific ST segment and T wave changes, atrioventricular block, right axis deviation of the terminal 40 ms vector of the QRS complex in the frontal plane (T 40 ms axis) and the Brugada pattern (downsloping ST segment elevation in leads V1-V3 in association with right bundle branch block). Maximal changes in the QRS duration and the T 40 ms axis are usually present within 12 hours of ingestion but may take up to a week to resolve. Sinus tachycardia is the most common arrhythmia due to anticholinergic activity and inhibition of norepinephrine uptake by tricyclic antidepressants but bradyarrhythmias (due to atrioventricular block) and tachyarrhythmias (supraventricular and ventricular) may occur. Torsade de pointes occurs uncommonly. Hypotension results from a combination of reduced myocardial contractility and reduced systemic vascular resistance due to alpha-adrenergic blockade. Life-threatening arrhythmias and death due to tricyclic antidepressant poisoning usually occurs within 24 hours of ingestion. Rapid deterioration is common. Level of consciousness at presentation is the most sensitive clinical predictor of serious complications. Although a QRS duration >100 ms and a rightward T 40 ms axis appear to be better predictors of cardiovascular toxicity than the plasma tricyclic drug concentration, they have at best moderate sensitivity and specificity for predicting complications.

Deadly pediatric poisons: nine common agents that kill at low doses

More than 97% of pediatric exposures reported to the AAPCC in 2001 had either no effect or mild clinical effects. Despite the large number of exposures, only 26 of the 1074 reported fatalities occurred in children younger than age 6. These findings reflect the fact that, in contrast to adolescent or adult ingestions, pediatric ingestions are unintentional events secondary to development of exploration behaviors and the tendency to place objects in the mouth. Ingested substances typically are nontoxic or ingested in such small quantities that toxicity would not be expected. As a result, it commonly is believed that ingestion of one or two tablets by a toddler is a benign act and not expected to produce any consequential toxicity. Select agents have the potential to produce profound toxicity and death, however, despite the ingestion of only one or two tablets or sips. Although proven antidotes are a valuable resource, their value is diminished if risk after ingestion is not adequately appreciated and assessed. Future research into low-dose, high-risk exposures should be directed toward further clarification of risk, improvements in overall management strategies,and, perhaps most importantly, prevention of toxic exposure through parental education and appropriate safety legislation.

Brugada syndrome and "Brugada sign": clinical spectrum with a guide for the clinician

BACKGROUND

Patients with the manifest Brugada syndrome have an inordinate risk of sudden death and are candidates for implantation of a defibrillator. The Brugada type electrocardiogram (ECG) abnormality (the "Brugada sign"), however, is known to be associated with a wide range of conditions, many of which may not pose such a threat. Clinicians need guidance in choosing a rational approach for the evaluation and treatment of patients with a finding of the Brugada sign.

METHODS

A systematic literature search was performed to identify publications on the Brugada syndrome and the Brugada-type ECG abnormality, with special emphasis on analyzing outcomes data. In addition, the ECG database of our institution was reviewed for tracings consistent with the Brugada sign, and, when possible, clinical correlations were made.

RESULTS

Patients with the Brugada sign and a family history of sudden death or a personal history of syncope are at a high risk of sudden death and therefore should be strongly considered for implantation of a defibrillator. In patients who are hospitalized and critically ill, the Brugada sign is frequently the result of severe hyperkalemia, drug toxicity, or right ventricular injury. In most individuals with no symptoms and without a family history of sudden death, the Brugada sign is likely a normal variant.

CONCLUSIONS

Most patients with the Brugada sign can be risk-stratified with simple clinical tools. Specific testing for the Brugada syndrome should be reserved for questionable cases and for the research setting. A provisional diagnostic-therapeutic algorithm is offered as a means of assisting the clinician in the evaluation and treatment of patients with the Brugada sign.