Drug-induced q-T prolongation

Salbutamol-Induced QT Interval Prolongation in a Two-Year-Old Patient

Salbutamol-induced QT interval prolongation is a relatively rare adverse effect of beta2-agonists. We report a case of a two-year-old female patient with no known past medical history, brought by her parents to the ED 30 minutes after ingesting a total dose of 97 mg of salbutamol solution. ECG was done for the patient when she arrived and showed sinus tachycardia with prolonged QTc (509 ms) and normal QRS complex. The patient was admitted to the Pediatric Intensive Care Unit (PICU) with persistent tachycardia and tachypnea in the initial reassessment. ECG was repeated with normal QT interval after IV Mg sulfate. The patient was observed in PICU for 12 hours with serial ECG and venous blood gas (VBG). IV potassium chloride (KCL) infusion started, and serial VBG showed normal potassium and lactate. The patient was doing well in the next six hours, with normal serial ECG, labs, and vital signs.

In conclusion, salbutamol-induced QT prolongation has infrequently been reported in the literature. Although inhaled salbutamol is commonly used in clinical practice, physicians have limited experience with the severe features of its toxicity. Salbutamol is known to cause minimal side effects, which may be under-recognized and progress to serious manifestations such as hypokalemia, QT prolongation, and sudden cardiac death.

Fluconazole-associated QT interval prolongation and Torsades de Pointes in a paediatric patient

"Torsades de pointes", a life-threatening rhythm disorder, is a polymorphic ventricular tachycardia that usually develops in association with a prolonged QT interval. Fluconazole, an anti-fungal drug, may also induce QT prolongation, in some cases subsequent torsades de pointes. Herein, we report a 16-year-old female presenting "torsades de pointes" after administration of fluconazole and rapidly improved upon cessation of the drug.

Unmasking Long QT Syndrome in the Emergency Department: A Case Report

Introduction

Long QT syndrome (LQTS) is an uncommon disorder that can lead to potentially life-threatening dysrhythmias. LQTS can be genetic, acquired, or both.

Case Report

A 44-year-old female with well-controlled hypertension and asthma presented with chest tightness. An initial electrocardiogram yielded a normal corrected QT interval of 423 milliseconds (ms) (normal <480 ms in females). Albuterol was administered and induced agitation, tremulousness, and tachycardia. Follow-up electrocardiograms demonstrated extreme prolongation of the corrected QT interval to 633 ms and morphology change of the T wave. Lab values were later notable for hypokalemia and hypomagnesemia, attributable to a recently started thiazide diuretic. The patient was ultimately diagnosed with congenital LQTS after initial unmasking by albuterol in the emergency department.

Conclusion

LQTS can be unmasked or exacerbated by electrolyte abnormalities and QT prolonging medications.

Exposure-response analysis of drug-induced QT interval prolongation in telemetered monkeys for translational prediction to human

INTRODUCTION

The preclinical in vivo assay for QT prolongation is critical for predicting torsadogenic risk, but still difficult to extrapolate to humans. This study ran preclinical tests in cynomolgus monkeys on seven QT reference drugs containing the drugs used in the IQ-CSRC clinical trial and applied exposure-response (ER) analysis to the data to investigate the potential for translational information on the QT effect.

METHODS

In each of six participating facilities in the J-ICET project, telemetered monkeys were monitored for 24 h following administration of vehicle or 3 doses of test drugs, and pharmacokinetic profiles at the same doses were evaluated separately. An individual rate-corrected QT interval (QTca) was derived and the vehicle-adjusted change in QTca from baseline (∆∆QTca) was calculated. Then the relationship of concentration to QT effect was evaluated by ER analysis.

RESULTS

For QT-positive drugs in the IQ-CSRC study (dofetilide, dolasetron, moxifloxacin, ondansetron, and quinine) and levofloxacin, the slope of the total concentration-QTca effect was significantly positive, and the QT-prolonging effect, taken as the upper bound of the confidence interval for predicted ∆∆QTca, was confirmed to exceed 10 ms. The ER slope of the negative drug levocetirizine was not significantly positive and the QTca effect was below 10 ms at observed peak exposure.

DISCUSSION

Preclinical QT assessment in cynomolgus monkeys combined with ER analysis could identify the small QT effect induced by several QT drugs consistently with the outcomes in humans. Thus, the ER method should be regarded as useful for translational prediction of QT effects in humans.

QT Prolongation and Malignant Arrhythmia: How Serious a Problem?

QT prolongation constitutes one of the most frequently encountered electrical disorders of the myocardium. This is due not only to the presence of several associated congenital syndrome but also, and mainly, due to the QT-prolonging effects of several acquired conditions, such as ischaemia and heart failure, as well as multiple medications from widely different categories. Propensity of repolarization disturbances to arrhythmia appears to be inherent in the function of and electrophysiology of the myocardium. In the present review the issue of QT prolongation will be addressed in terms of pathophysiology, arrhythmogenesis, treatment and risk stratification approaches. Although already discussed in literature, it is hoped that the mechanistic approach of the present review will assist in improved understanding of the underlying changes in electrophysiology, as well as the rationale for current diagnostic and therapeutic approaches.

Ventricular fibrillation after elective surgery in an adolescent with long QT syndrome

Congenital long QT syndrome (LQTS) is a potentially lethal but highly treatable channelopathy. Along with multiple risk reduction measures, a recommendation for left sympathetic cardiac denervation therapy and/or implantable cardioverter defibrillator is made for higher risk patients. Despite its relatively common incidence in paediatric patients, there are no formal recommendations regarding perioperative management and discharge criteria for LQTS patients undergoing ambulatory surgery. This report describes a 17-year-old girl, diagnosed with congenital LQTS at 9 years of age, who had an episode of ventricular fibrillation the day after elective ear, nose and throat surgery. Despite several risk factors, she had a same-day dismissal, was not adequately monitored postoperatively and her cardiologists were not notified of her procedure. For the high-risk LQTS patient, we recommend monitoring of perioperative electrolytes and rhythm, postoperative ECG, adequate β-blockade therapy, avoidance of particular pharmacological agents, consideration of overnight observation and communication with the patient's cardiologist prior to procedure, and at discharge.

Medical toxicologists' practice patterns regarding drug-induced QT prolongation in overdose patients: a survey in the United States of America, Europe, and Asia Pacific region

OBJECTIVE

To describe practice patterns of medical toxicologists in the United States of America (USA), Europe, and Asia Pacific Region regarding management of drug induced QT prolongation and torsades de pointes in overdose.

METHODS

A survey was developed to assess current practice patterns and consistency with guidelines published by the American Heart Association (AHA), American College of Cardiology (ACC), and European Society of Cardiology (ESC). It was reviewed by our department research committee and the American College of Medical Toxicology (ACMT). The ACMT, European Association of Poisons Centres and Clinical Toxicologists, and Asia Pacific Association of Medical Toxicology electronically disseminated the survey to their physician members in the USA, Europe and Asia Pacific Region.

RESULTS

The overall response rate was 37% (229/617) (36% USA; 32% Europe; 52% Asia Pacific Region). Twelve toxicologists from Asia Pacific Region and Europe used the QT nomogram (Australia-5, New Zealand-1, United Kingdom-1) or QT alone (France-1, Russia-1, Romania-1, Germany-1, Philippines-1), in lieu of the corrected QT (QTc) to determine risks of developing torsades de pointes. Because only those who used QTc could proceed through the remainder of the survey, only 217 could do so. Approximately half of the respondents (52%) did not calculate QTc manually and based decisions on the electrocardiogram machines automated measurement. For those who corrected the QT interval themselves, the most common formula used was Bazett's (40%). There is great variation in the QTc value considered prolonged. Most responders considered QTc greater than 450 ms in men (28%) and 460 ms in women (25%) to be prolonged. Interestingly, approximately 15% of participants did not consider the QTc prolonged until it exceeded 500 ms in both men and women. Given an overdose scenario of a male patient with a QTc of 560 ms, heart rate of 90 beats/minute, 59% would not recommend administering intravenous magnesium sulfate. Forty-five percent and 36% believed magnesium could shorten QTc and prevent torsades de pointes, respectively. In addition, almost 90% believed administering 1-2 boluses of intravenous magnesium is safe, even when serum magnesium is not available. In regards to cardiac pacing of patients with QT prolongation and torsades de pointes, only 38% of the participating toxicologists' responses agreed with AHA/ACC/ESC recommendations. Furthermore, 21% would not pace a patient who developed torsades de pointes regardless of the scenario.

DISCUSSION AND CONCLUSIONS

The results indicate that medical toxicologists have considerable heterogeneity in terms of management practices for overdose patients with QT prolongation and torsades de pointes. Medical toxicologists may benefit from developing evidence-based consensus guidelines for the management of this relatively common finding in overdose of QT-prolonging drugs.

Electrical therapies in cardiac arrest

Recognition and appropriate treatment of ventricular fibrillation or pulseless ventricular tachycardia is an essential skill for healthcare providers. Appropriate defibrillation can improve survival and benefit patient outcome. Similarly, increased public access to automatic electronic defibrillators has been shown to improve out-of-hospital survival for cardiac arrest. When combined with high-quality cardiopulmonary resuscitation, electrical therapies are an important aspect of resuscitation in the patient with cardiac arrest. This article focuses on the use of electrical therapies, including defibrillation, cardiac pacing, and automated external defibrillators, in cardiac arrest.

The significance of protein S-100B testing in cardiac arrest patients

Cardiac arrest often represents the first expression of an underlying cardiac disease. Despite advances in neurocritical care, the neurological assessment of cardiac arrest patients relies on clinical, instrumental and biochemical parameters. The clinical significance of S-100 calcium binding protein B (S-100B) has substantially increased throughout several areas of clinical neuroscience, but reliable evidences attest it can be used as a reliable and early predictor of poor physiological and cognitive neurological outcomes after cardiac arrest.

Pharmacokinetic-pharmacodynamic modelling of the effect of Moxifloxacin on QTc prolongation in telemetered cynomolgus monkeys

INTRODUCTION

Delayed ventricular repolarisation is manifested electrocardiographically in a prolongation of the QT interval. Such prolongation can lead to potentially fatal Torsades de Pointes. Moxifloxacin is a fluoroquinolone antibiotic which has been associated with QT prolongation and, as a result, is recommended by the regulatory authorities as a positive control in thorough QT studies performed to evaluate the potential of new chemical entities to induce QT prolongation in humans. The sensitivity of the cynomolgus monkey as a quantitative preclinical predictor of the PK-QTc relationship is discussed.

METHODS

Cardiovascular monitoring was performed in the telemetered cynomolgus monkey for 22 h following oral administration of Moxifloxacin (10, 30 and 90 mg/kg) or placebo. QTc was derived using an individual animal correction factor (ICAF): RR-I = QT-I--(RR-550)* (IACF). A PKPD analysis was performed to quantify the increase in placebo-adjusted QTc) elicited by administration of Moxifloxacin. In addition, the rate of onset of hERG channel blockade of Moxifloxacin was compared to Dofetilide by whole cell patch clamp technique in HEK-293 cells stably expressing the hERG channels.

RESULTS

Moxifloxacin induced a dose dependent increase in QTc). A maximum increase of 28 ms was observed following administration of 90 mg/kg Moxifloxacin. The corresponding maximum free systemic exposure was 18μM. Interrogation of the PK-QTc relationship indicated a direct relationship between the systemic exposure of Moxifloxacin and increased QTc. A linear PKPD model was found to describe this relationship whereby a 1.5 ms increase in QTc was observed for every 1 μM increase in free systemic exposure.

DISCUSSION

The exposure dependent increases in QTc observed following oral administration of Moxifloxacin to the cynomolgus monkey are in close agreement with those previously reported in human subjects. A direct effect linear relationship was found to be conserved in both species. As a result of the quantitative agreement in both species, the utility of the telemetered cynomolgus monkey as a preclinical predictor of QTc) prolongation is exemplified. Furthermore, the rate of onset of hERG channel blockade observed in patch clamp offers a mechanistic insight into the relative rates of channel blockade observed in vivo with both Moxifloxacin and Dofetilide.

Common drug interactions leading to adverse drug events in the intensive care unit: management and pharmacokinetic considerations

Critically ill patients are predisposed to drug interactions because of the complexity of the drug regimens they receive in the intensive care setting. Drugs may affect the absorption, distribution, metabolism, and/or elimination of an object drug and consequently alter the intended pharmacologic response and potentially lead to an adverse event. Certain disease states that afflict critically ill patients may also amplify an intended pharmacologic response and potentially result in an unintended effect. A team approach is important to identify, prevent, and address drug interactions in the intensive care setting and optimize patient outcomes.

Pharmacokinetics, bioavailability and effects on electrocardiographic parameters of oral fludarabine phosphate

The pharmacokinetics, bioavailability and effects on electrocardiographic (ECG) parameters of fludarabine phosphate (2F-ara-AMP) were evaluated in adult patients with B-cell chronic lymphocytic leukemia. Patients received single doses of intravenous (IV) (25 mg/m(2), n=14) or oral (40 mg/m(2), n=42) 2F-ara-AMP. Plasma concentrations of drug and metabolites and digital 12-lead ECGs were monitored for 23 h after dosing. The dephosphorylated product fludarabine (2F-ara-A) was the principal metabolite present in the systemic circulation. Mean (+/-SD) elimination half-life did not differ significantly between IV and oral dosage groups (11.3+/-4.0 vs 9.7+/-2.0 h, p=0.053). Renal excretion was a major clearance pathway, along with transformation to a hypoxanthine metabolite 2F-ara-Hx. Estimated mean oral bioavailability of 2F-ara-A was 58%. Compared to the time-matched drug-free baseline Fridericia correction of the QT interval (QTcF), the mean QTcF change following 2F-ara-AMP did not differ from zero, and a treatment effect of >+10 and >+15 ms could be excluded following oral and IV 2F-ara-AMP, respectively. Similarly, heart rate, PR interval and QRS duration did not change following 2F-ara-AMP treatment. Thus the 25 mg/m(2) IV and 40 mg/m(2) oral doses of 2F-ara-AMP produce similar systemic exposure, and do not prolong QTcF, indicating low risk of drug induced Torsades de Pointes.

Termination of drug-induced torsades de pointes with overdrive pacing

Drug-induced prolongation of the QT interval is frequently encountered after medication overdose. Such toxicity can result in degeneration to torsades de pointes (TdP) and require overdrive pacing. We present 3 cases in which intentional medication overdose resulted in QTc prolongation with subsequent degeneration to TdP. Despite appropriate care, including magnesium therapy, each case required overdrive pacing for resolution of TdP. Although rarely encountered, patients with drug-induced TdP can be successfully managed with overdrive pacing.

Antibiotic adverse reactions and drug interactions

When contemplating antibiotic use, intensivists must consider possible beneficial and harmful drug interactions. After antibiotics are instituted, adverse reactions must be anticipated. Acute illness, comorbidities, and concurrent medications affect the presentation and management of antibiotic-related adverse events. Intensivists should use the fewest possible antibiotics, carefully choosing agents that maximize antimicrobial activity and minimize potential drug interactions and adverse reactions.

Atypical antipsychotics and newer antidepressants

Atypical antipsychotics and newer antidepressants are commonly prescribed medications responsible for tens of thousands of adverse drug exposures each year. The emergency medicine physician should have a basic understanding of the pharmacology and toxicity of these agents. This knowledge is crucial to providing proper care and timely management of patients presenting with adverse drug effects from exposure to atypical antipsychotics and newer antidepressants.

Toxicologic issues during cardiopulmonary resuscitation

PURPOSE OF REVIEW

The following review intends to outline the unique aspects of providing cardiopulmonary resuscitation for the poisoned patient and highlights both current practice and new therapies that apply to toxicologic cases.

RECENT FINDINGS

Although there are few prospective randomized studies to further evidence-based care of the poisoned patient, there have been several reports of novel uses of both established medications and new medications in toxicologic patients. These case reports highlight treatment possibilities and potential avenues for further research.

SUMMARY

It is important for providers to recognize the limitations of standard advanced cardiac life support algorithms when caring for poisoned patients. Toxicologic causes of cardiopulmonary compromise should be considered along with administration of appropriate antidotes and adjunctive therapies.

Dental treatment of patients with long QT syndrome

BACKGROUND

Long QT syndrome (LQTS) is associated with life-threatening cardiac arrhythmias causing syncope and sudden cardiac death, frequently precipitated by physical or psychological stress.

TYPES OF STUDIES REVIEWED

The authors did a literature review of data published in peer-reviewed medical and dental journals. They also extracted epidemiologic information, correlations between genetic mutations and disease onset and progression, and data regarding outcomes of therapy from published peer-reviewed studies and the cohort population belonging to the International Long QT Syndrome Registry.

RESULTS

LQTS is diagnosed after an unexpected cardiac event or through QT interval prolongation on an electrocardiogram. Gene mutation identification in LQTS provides insight into respective proarrhythmogenic factors and indicated therapeutic regimens. beta-blockers are the initial treatment for two of the three major forms of LQTS. Patients refractory to beta-antiadrenergic therapy may benefit from one or more of the following: cardiac pacemakers, implanted cardioverter defibrillators and left cardiac sympathetic denervation.

CONCLUSIONS

Clinical studies are needed to investigate the safety of treating patients in an ambulatory setting.

CLINICAL IMPLICATIONS

Preventive measures are recommended, including evaluation by a cardiac specialist before any dental intervention, use of anxiolytic protocols, avoidance of drugs that prolong the QT interval, and provision of treatment in a setting in which medical emergencies can be managed expeditiously. Dental treatment in a hospital and use of a general anesthetic administered by anesthesiologists are recommended for procedures in which anxiety and adrenergic stimulation would not be suppressed sufficiently in an ambulatory environment.