Electrocardiographic Predictors of Adverse Cardiovascular Events in Suspected Poisoning

Abstract

Poisoning is the second leading cause of injury-related fatality in the USA and the leading cause of cardiac arrest in victims under 40 years of age. The study objective was to define the electrocardiographic (ECG) predictors of adverse cardiovascular events (ACVE) complicating suspected acute poisoning (SAP). This was a case-control study in adults at three tertiary-care hospitals and one regional Poison Control Center. We compared 34 cases of SAP complicated by ACVE to 101 consecutive control patients with uncomplicated SAP. The initial ECG was analyzed for rhythm, intervals, QT dispersion, ischemia, and infarction. ECGs were interpreted by a cardiologist, blinded to study hypothesis and case data. Subjects were 48% male, with mean age 42 +/- 19 years. In addition to clinical suspicion of poisoning in 100% of patients, routine toxicology screens were positive in 77%, most commonly for benzodiazepines, opioids, and/or acetaminophen. Neither the ventricular rate, the QRS duration, nor the presence of infarction predicted the risk of ACVE. However, the rhythm, QTc, QT dispersion, and presence of ischemia correlated with the risk of ACVE. Independent predictors of ACVE based on multivariable logistic regression were prolonged QTc, any non-sinus rhythm, ventricular ectopy, and ischemia. Recursive partitioning analysis identified very low risk criteria (94.1% sensitivity, 96.2% NPV) and high risk criteria (95% specificity). Among patients with SAP, the presence of QTc prolongation, QT dispersion, ventricular ectopy, any non-sinus rhythm, and evidence of ischemia on the initial ECG are strongly associated with ACVE.

Utility of Cardiac Troponin to Predict Drug Overdose Mortality

“…These findings are consistent with a prior study that demonstrated a strong association of ECG ischemia with adverse cardiovascular events in overdose patients [17]. In that prior study, components of the initial ECG were analyzed for the ability to predict cardiovascular events, and it was found that ECG evidence of ischemia was present in 40 % of patients who went on to have in-hospital cardiac arrest, versus 18 % of those who did not ( p < 0.05).…”

Clinical Risk Factors for In‐hospital Adverse Cardiovascular Events After Acute Drug Overdose

“…9 VF is probably the final common pathway of most sudden cardiac deaths, but rhythm disturbances may begin with monomorphic or polymorphic VT as well as torsade de pointes, 23 a form of polymorphic VT that is identified characteristically on the ECG. The dichotomization of QTc around 500 ms in this study, in lieu of the “QT nomogram,” 24 is justified by prior drug overdose data using this cutoff to predict ACVE, 8 as well as data from Chan and colleagues that demonstrated that the QT nomogram performed essentially the same as the 500 ms cutoff at predicting poisoning-related torsade de pointes (98.7% vs. 97.2% specificity, respectively). 24 This study demonstrates that VT/VF is much more common than torsade de pointes in this population, and that dysrhythmia occurrence may be predictable.…”

“…The final multivariable model was built around four separate conceptual clusters (defined a priori on the basis of clinical experience and prior data, 8 as demographic, clinical history, laboratory, and ECG variables) considered as separate groups to achieve a parsimonious and clinically meaningful model. Associations between clinical factors and the primary outcome were calculated first using univariate analysis.…”

“…3 A formal definition of drug-overdose related ACVE was initially informed by the International Liaison Committee on Resuscitation, 7 subsequently explored with preliminary data, 8 and then formally validated by a large prospective cohort study of acute drug overdose patients identified from the ED and followed to hospital discharge. 9 In accordance with this extensive prior work, the following is the current definition of drug-related ACVE: myocardial injury (by biomarker or electrocardiogram [ECG] evidence); shock (hypotension or hypo-perfusion requiring vasopressors); ventricular dysrhythmias (ventricular tachycardia/fibrillation, torsade de pointes); and cardiac arrest (loss of pulse requiring cardiopulmonary resuscitation [CPR]).…”

Racial susceptibility for QT prolongation in acute drug overdoses

“…QT prolongation is considered to be a reliable surrogate for the potentially fatal dysrhythmia known as torsades de pointes (TdP), because TdP is generally preceded by QT prolongation. Previously, QT prolongation has been identified as a strong predictor of adverse cardiovascular events in suspected poisoning from drug overdose (10). …”