QT interval prolongation and the risk of malignant ventricular dysrhythmia and/or cardiac arrest: Systematic search and narrative review of risk related to the magnitude of QT interval length

Prolongation of the QTc interval is associated with an increased risk of malignant ventricular dysrhythmias, such as ventricular tachycardia (VT), and sudden cardiac death. The quantifiable risk rates of adverse dysrhythmic outcome in relation to specific QTc interval length are not known. We conducted a literature review on the topic of QT interval prolongation in adult patients and the associated risk of malignant dysrhythmic event. We specifically formulated our literature search and subsequent literature review to address the following question: Can the clinician identify specific QTc intervals at which a specific quantifiable risk of malignant dysrhythmic event (malignant ventricular dysrhythmia and/or cardiac arrest) occurs in an undifferentiated adult patient population? In the literature search, we identified 701 studies; upon review using specific, pre-determined inclusion criteria, we identified 16 articles for inclusion in the review. From this literature, we were unable to answer the question in a quantifiable manner and only noted that the risk of malignant dysrhythmic event increases with progressively longer QTc interval. The current literature on this topic is inadequate to answer this important question due to heterogenous study methodology, patient populations, endpoints, and periods of observation. Additional prospective research is required on this topic, aimed at addressing the important issue of specific, quantifiable risk and its relation to degree of prolongation of the QTc interval.

QT interval prolongation and the rate of malignant ventricular dysrhythmia and cardiac arrest in adult poisoned patients

INTRODUCTION

Prolongation of QTc interval, a common electrocardiographic (ECG) abnormality encountered in the toxicology patient, is reportedly associated with an increased risk of malignant ventricular dysrhythmias (MVD), such as ventricular tachycardia (VT, with and without a pulse), ventricular fibrillation (VF), and/or cardiac arrest. Quantifiable cardiac arrest risk in relation to specific QTc interval length is not known in this population.

METHODS

We conducted a retrospective, observational study to assess the rate of cardiac arrest and its association with degree of QTc prolongation in a cohort of patients requiring toxicology consultation.

RESULTS

550 patients were included in our analysis (average age 36 years and 49% male). Average QTc was 453 milliseconds (ms). Overall incidence of cardiac arrest in the study cohort was 1.1% with 6 reported cases; when considering patients with QTc > 500 ms, incidence was 1.7%. Two patients with cardiac arrest experienced ventricular dysrhythmia with decompensation prior to cardiac arrest; four patients developed sudden cardiac arrest.

CONCLUSIONS

The risk of malignant ventricular dysrhythmia, including cardiac arrest, is low in this poisoned patient population with an overall rate of 1.1%. Two-thirds of cardiac arrest cases occurred in patients with normal QTc intervals. When considering patients with prolonged QTc intervals, the rate of cardiac arrest remains very low at 0.8%. Considering QTc greater than 500 ms, the rate of cardiac arrest is 1.7%. Further prospective studies are required to quantify the risk of malignant ventricular dysrhythmias, including cardiac arrest, and its relation to the degree of QTc interval in poisoned patients.

Nonepileptic seizure provoked by cardiac dysrhythmia with STEMI

Acute seizures represent 1% of all visits to emergency departments in the United States. While many acute seizures are correctly attributable to underlying epilepsy, approximately one-third of acute seizures are provoked by underlying and potentially life-threatening acute conditions. Many clinical syndromes associated with seizure-like activity are well-established and readily identified in the acute setting. Cardiac dysrhythmias are known causes of acute seizure-like activity and, if transient and not captured by electrocardiogram tracings during acute episodes, may be incorrectly diagnosed as epileptic seizures. We report a case of acute ST-segment elevation myocardial infarction presenting with acute symptomatic seizure due to occult transient cardiac dysrhythmia.

Is oxygen required before atropine administration in organophosphorus or carbamate pesticide poisoning? - A cohort study

Background

Early and adequate atropine administration in organophosphorus (OP) or carbamate insecticide poisoning improves outcome. However, some authors advise that oxygen must be given before atropine due to the risk of inducing ventricular dysrhythmias in hypoxic patients. Because oxygen is frequently unavailable in district hospitals of rural Asia, where the majority of patients with insecticide poisoning present, this guidance has significant implications for patient care. The published evidence for this advice is weak. We therefore performed a patient cohort analysis to look for early cardiac deaths in patients poisoned by anticholinesterase pesticides.

Methods

We analysed a prospective Sri Lankan cohort of OP or carbamate-poisoned patients treated with early atropine without the benefit of oxygen for evidence of early deaths. The incidence of fatal primary cardiac arrests within 3 h of admission was used as a sensitive (but non-specific) marker of possible ventricular dysrhythmias.

Results

The cohort consisted of 1957 patients. The incidence of a primary cardiac death within 3 h of atropine administration was 4 (0.2%) of 1957 patients. The majority of deaths occurred at a later time point from respiratory complications of poisoning.

Conclusion

We found no evidence of a high number of early deaths in an observational study of 1957 patients routinely given atropine before oxygen that might support guidance that oxygen must be given before atropine. The published literature indicates that early and rapid administration of atropine during resuscitation is life-saving. Therefore, whether oxygen is available or not, early atropinisation of OP- and carbamate-poisoned patients should be performed.