Controversies in the actions of digitalis substances: are all digitalis derivatives alike?

Epilepsy and sudden death: personal reflections and call for global action

To solve the mystery of sudden unexpected death in persons with epilepsy (SUDEP), a global focus is needed to identify persons at risk, develop treatment regimens, and prevent its occurrence. A world wide network of professionals must focus on basic scientific research programs and clinical and epidemiology studies. Team work among different multidisciplinary professionals in clinical settings and within and among laboratories should address the global issues of SUDEP. If the correct term 'SUDEP' is used on autopsy reports and if verbal autopsies postmortem are conducted when needed, the true incidence of SUDEP may be found to be much higher than previously thought and the market for new antiepileptics and other drugs to prevent SUDEP will be larger. Symposia should discuss new data and lessons learned from the last 20 to 30 years to be applied by scientists and clinicians worldwide to gain a better understanding of SUDEP. 'Think out of the box' when evaluating an established animal model with potential for modification(s) to study mechanism(s) of SUDEP. Multiple relevant animal models are needed to understand the pathophysiology of SUDEP, hypothesize about effective treatments, develop small pilot studies in persons with epilepsy, and conduct confirmatory large-scale clinical trials. The fields of pharmacology, clinical pharmacology, and cardiology have much to offer as we work to improve compliance, develop new antiepileptic drugs, and apply different categories of drugs to resolve the mystery of SUDEP. Ambulatory simultaneous EKG and EEG telemetry monitoring of patients at risk for sudden death will help identify cardiac vs. brain epileptogenic triggers for treatment to decrease risk of SUDEP. Respiratory function monitoring is also needed. Academic fellowships and competitions for medical students, postdoctoral fellows, residents and faculty will attract medical and graduate trainees to work on SUDEP. Grant funding is essential to move the SUDEP knowledge base forward. Leaders must solve the global mystery of SUDEP using a leadership philosophy foundation that provides innovative vision and approaches for SUDEP research and teaching programs. The interaction of teaching and research is essential: while a student is learning how to conduct research he must simultaneously learn to become a teacher. Medical and graduate leaders must provide vision and a fertile environment to teach students of today to become the self learners and leaders of tomorrow to find solutions for SUDEP.

Clinical pharmacology: drugs as a benefit and/or risk in sudden unexpected death in epilepsy?

Death may be the consequence of natural or unnatural causes, such as accidents, homicide, and suicide, which have no relationship to the disease of epilepsy. Direct causes of death include status epilepticus, and indirect causes may be head trauma or drowning subsequent to a seizure. When death occurs suddenly and without explanation, the term sudden unexpected unexplained death is used. Unexplained is a term that clinicians and research scientists are working to clarify. Numerous preclinical animal studies have been conducted as models for sudden death and have led to clinical studies in persons with epilepsy. These studies show that sympathetic nerve stimulation, ouabain, or coronary occlusion increased temporal dispersion of recovery of ventricular excitability and led to an underlying electrical instability that predisposed the ventricularmyocardium to arrhythmia. Cardiac arrhythmias in an animal model for ouabain-induced toxicity were associated with neural autonomic dysfunction. Neural discharges were characterized by increases, decreases, or no change in the discharge of postganglionic cardiac sympathetic nerves monitored simultaneously, predisposing to cardiac arrhythmia. Stimulation of the sympathetic ventrolateral cardiac nerve produced a shift in the origin of the pacemaker and tachyarrhythmias because the nerve is not uniformly distributed to the various regions of the heart but is localized to the atrioventricular junctional and ventricular regions. Such nonuniform distribution of sympathetic nerves would also contribute to initiation of arrhythmia as a nonuniform neural discharge occurred. Studies examining the physiology and pharmacology of this finding in multiple animal models found that subconvulsant, interictal discharge was associated with autonomic cardiac neural non-uniform discharge and cardiac arrhythmias. As a result of further investigations, Lathers and Schraeder edited a book in 1990 that summarized the clinical problem of sudden unexpected death and epilepsy (SUDEP). The contributors concluded that there was a paucity of clinical data addressing the mechanism of death. Regulatory response resulting from the consequent increased awareness of SUDEP occurred in 1993, when the FDA focused attention of practitioners and pharmaceutical manufacturers on the question of whether use of anticonvulsant drugs contributes to or prevents sudden unexpected death in epileptic persons. The FDA-convened panel of scientists considered the prevalence of sudden unexpected death in patients involved in studies associated with developing new anticonvulsant drugs and reviewed data on the risk of sudden unexpected death in patients taking lamotrigine. The risk of SUDEP was no different from thatfound in the young epilepsy population in general. Estimated SUDEP rates in patients receiving the new anticonvulsant drugs lamotrigine, gabapentin, topiramate, tigabine, and zonisamide were found to be similar to those in patients receiving standard anticonvulsant drugs, suggesting that SUDEP rates reflect population rates and not a specific drug effect. The FDA required warning labels on the risk of SUDEP in association with the use of each of the above-mentioned drugs. Another effect of bringing SUDEP to the attention of epilepsy researchers has been the expansion of basic science and the development of epidemiological and clinical studies directed at this phenomenon. Results from some of these studies are discussed in this article.

Does chlorpromazine produce cardiac arrhythmia via the central nervous system?

The influence of the central nervous system in the production of phenothiazine-induced arrhythmia and death was examined in this study. In a series of cats, spinal cords were transected at the atlanto-occipital junction prior to the 1 mg/kg/min, i.v. infusion of chlorpromazine or thioridazine. No protection against drug-induced arrhythmia or death was afforded by this procedure. In other cats, 6OH-dopamine was administered prior to intravenous injection of atropine and infusion of chlorpromazine, 1 mg/kg/min. In these in situ denervated heart preparations, there was no protection against chlorpromazine-induced arrhythmia or death. In alpha-chloralose anesthetized cats, 0.5 mg chlorpromazine administered intracerebroventricularly did not induce arrhythmia or death, although blood pressure decreased initially. Thus, chlorpromazine or thioridazine do not appear to produce arrhythmia or death via a central locus and may instead be acting directly on myocardial conduction to produce arrhythmia and death.

Chlorpromazine: cardiac arrhythmogenicity in the cat

To determine the effect of chlorpromazine on ouabain-induced arrhythmia and death, dial-urethane anesthetized cats were pretreated with chlorpromazine (5, 10, 20, 30, 40, or 60 mg/kg, i.v.) and then administered ouabain (2 microgram/kg/min, i.v.). Blood pressure, heart rate and lead II electrocardiogram (ECG) were monitored. The dosages of ouabain necessary to induce premature ventricular contractions, ventricular tachycardia and death were determined. No significant correlation between the dose of chlorpromazine given and the dose of ouabain required to produce arrhythmia or death was found. These doses of chlorpromazine could, therefore, be considered neither arrhythmogenic nor antiarrhythmic in the ouabain model. To determine whether chlorpromazine produced arrhythmia in the dial-urethane anesthetized cat model, the drug was infused at a rate of 1 mg/kg/min, i.v. Chlorpromazine produced arrhythmia at 185 +/- 4.3 minutes and death via cardiovascular collapse at 128 +/- 4.7 minutes. Bilateral adrenal vein ligation, employed to eliminate the influence of adrenal catecholamines, decreased the dosage of chlorpromazine necessary to produce arrhythmia and death to 67.8 +/- 17.7 and 84.7 +/- 15.7 mg/kg, respectively. Thus, adrenal catecholamines did not appear to contribute to chlorpromazine-induced arrhythmia, although the procedure of bilateral adrenal vein ligation appeared to be deleterious in combination with chlorpromazine. In all experiments, chlorpromazine depressed blood pressure without producing the reflex tachycardia normally seen with hypotension. This suggests that the drug may be interfering with the baroreceptor reflex arc. As chlorpromazine modifies the autonomic parameters of blood pressure, heart rate, and cardiac electrophysiology, sudden unexplained death in patients managed with this agent may be due to drug-induced arrhythmia.