Ischemia enhances use-dependent sodium channel blockade by pilsicainide, a class IC antiarrhythmic agent

Acute Cardiovascular Toxicity of Cocaine

Cocaine is one of the most commonly abused drugs and represents a major public health concern. Cocaine users frequently present to the emergency department, with chest pain being the most common presenting complaint. The incidence of acute myocardial infarction in patients with cocaine-associated chest pain is often quoted as 6%, but it is highly variable depending on the included population. Risk assessment can be challenging in these patients; serial assessment of electrocardiograms and troponins is often required. This review focuses on the assessment and management of patients presenting with cocaine-associated chest pain and cardiotoxicity. Specific treatments are discussed, including benzodiazepines, nitroglycerin, calcium channel blockers, and phentolamine, and how treatment priorities differ from patients with noncocaine presentations. The use of beta-blockers in this population remains controversial, and the literature around its use is reviewed. The most recent literature and recommendations for the use of percutaneous coronary intervention and fibrinolytics in cocaine-associated myocardial infarction is discussed as well. Cocaine-associated dysrhythmias are suggested to be the cause of sudden cardiac death in some users. The pathophysiology and evidence-based treatments for dysrhythmias are reviewed. This review provides evidence-based recommendations for the assessment and management of patients presenting with cocaine-associated cardiovascular toxicity.

Utility of Routine Exercise Testing to Detect Rate-Related QRS Widening in Patients Without Structural Heart Disease on Class Ic Antiarrhythmic Agents (Flecainide and Propafenone)

Class Ic antiarrhythmic agents are effective in the treatment of various atrial tachyarrhythmias. They are known to cause rate-related QRS widening in the presence of structural heart disease, which can lead to life-threatening arrhythmias. The role of routine exercise electrocardiography in patients without structural heart disease is unknown. All patients initiated on class Ic antiarrhythmic agents and who had exercise electrocardiography performed from June 2009 to June 2013 were included. Symptom-limited treadmill electrocardiography was performed to detect significant QRS widening at peak exercise (defined as an increase of >25% of baseline QRS). Fifty-six patients were included in the study. All patients were screened for structural heart disease before initiation of the medication. Significant QRS widening and atrial tachycardia occurred in a single patient, which terminated with cessation of exercise. This patient had a history of tachycardia-mediated cardiomyopathy with normalization of ejection fraction 3 years before being placed on flecainide. In conclusion, routine exercise testing to detect QRS widening is not warranted in patients with no structural heart disease.

The evaluation and management of drug effects on cardiac conduction (PR and QRS intervals) in clinical development

Recent advances in electrocardiographic monitoring and waveform analysis have significantly improved the ability to detect drug-induced changes in cardiac repolarization manifested as changes in the QT/corrected QT interval. These advances have also improved the ability to detect drug-induced changes in cardiac conduction. This White Paper summarizes current opinion, reached by consensus among experts at the Cardiac Safety Research Consortium, on the assessment of electrocardiogram-based safety measurements of the PR and QRS intervals, representing atrioventricular and ventricular conduction, respectively, during drug development.

Pilsicainide

Pilsicainide is a class Ic antiarrhythmic agent used for the treatment of supraventricular and ventricular tachycardia. The pharmacodynamic effects of pilsicainide are achieved via selective sodium channel blockade. In randomized, multicentre trials in patients with atrial fibrillation, restoration of sinus rhythm was achieved in significantly more patients treated with a single oral dose of pilsicainide than those who received placebo, and in a numerically higher proportion of oral pilsicainide than intravenous disopyramide recipients. In another well designed trial in patients with persistent atrial fibrillation, the proportion of patients whose arrhythmia converted to normal sinus rhythm was significantly higher among those randomized to receive 2 weeks of oral pilsicainide therapy than among patients who received placebo. Over a 1-year period, both pilsicainide and cibenzoline (another class Ic agent) were effective in preventing recurrence of atrial fibrillation in a substantial proportion of patients in a single-centre crossover trial. There were no between-group differences in the subgroup of patients with shorter-duration atrial fibrillation, but actuarial results over 1 year significantly favoured cibenzoline over pilsicainide in patients with longer-duration atrial fibrillation. Both oral and intravenous pilsicainide have demonstrated efficacy in ventricular tachyarrhythmias, including ventricular extrasystole. Clinical trial and postmarketing surveillance data indicate that pilsicainide is generally well tolerated in most patients.

Management of cocaine-induced cardiac arrhythmias due to cardiac ion channel dysfunction

Cocaine use is common in many areas of the world, particularly the United States and Western Europe. Toxicity following the use of cocaine is associated with a wide range of clinical features. In this review, we will focus on the cocaine-associated cardiac arrhythmias and, in particular, some of the controversies in their etiology and management. Cocaine can produce arrhythmias either through the production of myocardial ischemia or as a direct result of ion channel alterations. Excessive catecholamines, combined with sodium and potassium channel blockades, give rise to a wide variety of supra-ventricular and ventricular rhythms. The animal and human evidence for ion channel dysfunction is reviewed, and the effects of catecholamines are followed from the cardiac action potential to the development of arrhythmias. Finally, theoretical constructs are combined with existing evidence to develop a rational treatment strategy for patients with cocaine-induced cardiac arrhythmias. In particular, we review the evidence concerning the controversies relating to the use of lidocaine in comparison with sodium bicarbonate, in terms of QRS prolongation secondary to sodium channel blockade.

A case of sinus pause due to the proarrhythmia of pilsicainide

A 74-year-old man received oral administration of pilsicainide, a pure sodium channel blocker with slow recovery kinetics, to convert paroxysmal atrial fibrillation to sinus rhythm and developed loss of consciousness two days later. The ECG monitoring revealed sinus pause with markedly prolonged PQ interval and QRS width. Two days after the drug was discontinued, the duration of the QRS complex was normalized. This drug is rapidly absorbed from the gastrointestinal tract, most of which is excreted from the kidney. The plasma concentration of pilsicainide, although not measured, must have been very high, since his renal function was impaired. When pilsicainide is prescribed in patients with coronary artery disease or renal dysfunction, close attention must be paid to avoid life-threatening arrhythmias due to high plasma concentrations of the drug. This is an interesting case because the proarrhthmia of the drug was not tachyarrhythmia, such as ventricular tachycardia or torsades de pointes, but sinus pause.

Class IC antiarrhythmic drugs, flecainide and pilsicainide, produce ST segment elevation simulating inferior myocardial ischemia

Flecainide and pilsicainide, Class IC antiarrhythmic drugs with slow kinetics, were administered to a 64-year-old man experiencing ventricular tachycardia. Both drugs suppressed the arrhythmia, but caused ST segment elevation in leads II, III, and aVF. No evidence of ischemic heart disease was detected. Withdrawal of the drugs eliminated the ST change. Because these drugs frequently are used to treat tachyarrhythmias in patients who may present with chest pain, this rare ECG manifestation of Class IC drugs should be recognized to avoid misdiagnosis of acute inferior myocardial infarction.

Anti-ischemic intervention as prognosis improvement in patients with coronary artery disease, with special focus on verapamil

Angina pectoris is a significant risk predictor in patients with atherosclerotic heart disease. The major complications are myocardial infarction, heart failure, and arrhythmias. Plaque rupture turns stable angina pectoris into acute coronary syndrome by provoking platelet aggregation and thereby thrombus formation. Verapamil significantly inhibits platelet aggregation and thrombus formation, which may be one of several reasons for the protective effect of verapamil on reinfarction in patients recovering from myocardial infarction. Ischemia may lead to left ventricular dilation and diastolic dysfunction, and thereby heart failure. In postinfarction patients intervention with verapamil significantly reduced the use of diuretics compared with placebo, indicating that anti-ischemic intervention may prevent heart failure. Ventricular arrhythmias are significantly associated with arrhythmic as well as non-arrhythmic death. The lack of preferential association of ventricular arrhythmias with arrhythmic death rather than nonarrhythmic death may imply that arrhythmias are provoked by ischemia. Antiarrhythmic intervention in postinfarction patients significantly increases death and arrhythmic events compared with placebo, especially in patients with residual ischemia. This may be due to a significant slowing of conduction during ischemia in patients treated with antiarrhythmic agents. In animal studies anti-ischemic agents prevent or suppress ventricular arrhythmias during ischemia, whereas traditional antiarrhythmic drugs have no effect or even worsen the arrhythmias, especially during episodes with elevated sympathetic activity. Verapamil significantly reduces plasma norepinephrine levels and the norepinephrine release during ischemia, whereby ventricular arrhythmias may be prevented. Also, supraventricular arrhythmias are significantly associated with myocardial ischemia and are prevented by verapamil. In patients with atherosclerotic heart diseases, angina pectoris is a significant risk predictor, but anti-ischemic intervention should be considered even in patients in whom the major problem is heart failure or arrhythmias.

Mechanisms of negative inotropic effects of class Ic antiarrhythmic agents: comparative study of the effects of flecainide and pilsicainide on intracellular calcium handling in dog ventricular myocardium

We studied the subcellular mechanisms responsible for the negative inotropic effects of the two Ic drugs flecainide and pilsicainide. Aequorin luminescence (Ca2+i) and isometric tension were recorded simultaneously in isolated trabeculae from the dog ventricle. In isolated myocytes from the same ventricle, the slow inward current (ICa) was recorded. Both flecainide and pilsicainide decreased peak Ca2+i, peak tension, and peak ICa concentration dependently. Each effect with flecainide was more marked than that with pilsicainide; however, Ca2+i and ICa paralleled each other in changes in tension, and the tension-Ca2+i-ICa relationship showed the same curve for each drug. We conclude that the difference in negative inotropic effects of these class Ic drugs are primarily related to their effects on L-type Ca2+ channels and the subsequent decreases in the amount of Ca2+ released from the sarcoplasmic reticulum (SR) during each cardiac cycle. Therefore, their negative inotropic effects may not be directly correlated with the essential mechanisms responsible for their antiarrhythmic action.