Proarrhythmia: definition, risk factors, causes, treatment, and controversies

Supraventricular tachycardias in neonates and infants: factors associated with fatal or near-fatal outcome

Prognosis of supraventricular tachycardias in neonates and infants is thought to be excellent with rare fatal outcomes. Nevertheless, initial management can be challenging. The aim of this study was to perform a retrospective analysis in neonates/infants with non-pos-toperative supraventricular tachycardias regarding risk factors for clinical outcome and type of antiarrhythmic drug therapy. The data of 157 patients aged < 1 year who presented between 2000 and 2015 with symptomatic tachycardias were retrospectively reviewed. Pharmacological therapy was successful in 151 patients (96%); 1 patient (1%) required catheter ablation and 5 patients (3%) died (1 death linked to hemodynamical reasons after effective arrhythmia control). Serious complications following acute medical therapy occurred in 4 patients of survivors. Patients with complications or death had a lower bodyweight, more frequent intrauterine tachycardia, transplacental therapy, urgent caesarian section, higher PRISM II score, longer period to control tachycardia, more frequent proarrhythmia, and major adverse event-defined as life-threatening event without a documented new arrhythmia-compared to the group without complications. There was no significant difference between the groups regarding prematurity, structural heart disease, and type of tachycardia. Proarrhythmia occurred in 6 cases and was related to intravenous drug use with class IC antiarrhythmics in 3/6 cases, digoxin in 2/6 cases, and amiodarone in 1/6 cases. ECG signs of impending proarrhythmia without new-onset arrhythmia requiring cessation of therapy were detected in 6 patients.Conclusion: Although rare, non-post-operative supraventricular tachycardia in neonates and infants might be a serious disease. Acute intravenous pharmacological treatment to control tachycardia might pose a risk for fatal or near-fatal outcome. Detection of proarrhythmia related to class IC antiarrhythmics in neonates might be especially difficult and requires alertness. What is Known • Prognosis of supraventricular tachycardias in children are thought to be excellent with fatal outcomes being rare. • Mortality is increased in the very young and in those with structural heart disease. What is New • Complicated outcome of non-post-operative supraventricular tachycardias in neonates is associated with lower bodyweight, age, prenatal tachycardia, higher PRISM II score, longer period to control tachycardia, and proarrhythmia. • Detection of class IC proarrhythmic effect is especially difficult in neonates because of their narrow QRS and warrants alertness.

Donepezil-induced torsades de pointes without QT prolongation

We report a case of torsades de pointes (TdP) induced by donepezil without QT prolongation. An 86-year-old woman was admitted to our hospital because of a syncopal attack. She had been treated for Alzheimer's disease with donepezil. Initial 12-lead electrocardiogram showed atrial fibrillation and normal corrected QT interval. After admission, atrial fibrillation spontaneously recovered to normal sinus rhythm on electrocardiographic monitoring. On the second day, electrocardiographic monitoring documented TdP. We discontinued donepezil immediately. After washout of donepezil, TdP was not observed again. Corrected QT interval was normal throughout hospitalization. This case suggests that donepezil may cause life-threatening ventricular arrhythmias without QT prolongation. Even if corrected QT interval is normal in patients taking donepezil and experiencing symptoms associated with TdP, electrocardiographic monitoring is recommended. .

Lack of action potential-prolonging effect of terfenadine on rabbit myocardial tissue preparations

The effects of terfenadine, an antiallergic drug also known for its QT-prolonging and arrhythmogenic activities, on the action potential of isolated myocardial tissue preparations from rabbits were examined with microelectrode techniques. In the Purkinje fibers and atrium, terfenadine concentration dependently decreased the maximum rate of rise (+.V(max)) without affecting other action potential parameters. In the ventricle, terfenadine had little effect on action potential configuration. In the sinoatrial node, terfenadine 20 microM prolonged cycle length mainly through inhibition of +.V(max). Terfenadine 1 microM completely inhibited the human ether a go-go-related gene (HERG) channel current expressed in HEK293 cells in the same experimental solution as in microelectrode experiments. The lack of terfenadine effect on the action potential duration suggests that there are drugs for which the HERG channel inhibitory action underlying in vivo QT prolongation cannot be evaluated based on their action potential-prolonging activity in isolated myocardial tissue preparations.

Therapeutic drug monitoring of antiarrhythmic drugs

Most antiarrhythmic drugs fulfil the formal requirements for rational use of therapeutic drug monitoring, as they show highly variable plasma concentration profiles at a given dose and a direct concentration-effect relationship. Therapeutic ranges for antiarrhythmic drugs are, however, often very poorly defined. Effective drug concentrations are based on small studies or studies not designed to establish a therapeutic range, with varying dosage regimens and unstandardised sampling procedures. There are large numbers of nonresponders and considerable overlap between therapeutic and toxic concentrations. Furthermore, no study has ever shown that therapeutic drug monitoring makes a significant difference in clinical outcome. Therapeutic concentration ranges for antiarrhythmic drugs as they exist today can give an overall impression about the drug concentrations required in the majority of patients. They may also be helpful for dosage adjustment in patients with renal or hepatic failure or in patients with possible toxicological or compliance problems. Their use in optimising individual antiarrhythmic therapy, however, is very limited.

Predictors of atrial flutter with 1:1 conduction in patients treated with class I antiarrhythmic drugs for atrial tachyarrhythmias

OBJECTIVES

The purpose of the study was to look for the predictor factors of atrial proarrhythmic effects of class I antiarrhythmic drugs.

BACKGROUND

Class I antiarrhythmic drugs may induce or exacerbate cardiac arrhythmias. The predictors of ventricular proarrhythmia are known. The predictors of atrial flutter with 1:1 conduction are unknown.

METHODS

Clinical history, EGG, signal-averaged EGG (SAECG) and electrophysiologic study were analysed in 24 cases of 1:1 atrial flutter with class I AA drugs and in 100 control patients without history of 1:1 atrial flutter with class I AA drugs.

RESULTS

The ages of patients varied from 46 to 78 years. Underlying heart disease was present in nine patients. The surface EGG revealed the presence of a short PR interval (PR<0.13 ms), visible in leads V5, V6 in eight (35%) patients with normal P wave duration; in other patients with prolonged P wave duration, PR seemed normaL On SAECG recording, there was a pseudofusion between P wave and QRS complex. The electrophysiologic study revealed some signs indicating a rapid AV nodal conduction (short AH interval or rate of 2nd degree AV block at atrial pacing >200 beats/mm) in 19 of the 23 studied patients. All patients, except one, had at least one sign indicating a rapid AV nodal conduction (short PR and/or P wave-QRS complex continuity on SAECG). In the control group, seven patients (7%) had a short PR interval (P<0.01) and 11 (11%) had a pseudofusion between P wave and QRS complex on SAECG (P<0.001). The P wave-QRS complex pseudofusion on SAECG had a sensitivity of 100% and a specificity of 89% for the prediction of an atrial proarrhythmic effect with class I antiarrhythmic drug.

CONCLUSION

We recommend avoiding class I AA drugs in patients with a short PR interval on surface EGG and to record SAECG in those with apparently normal PR interval to detect a continuity between P wave and QRS complex, which could indicate a rapid AV nodal conduction, predisposing to 1:1 atrial flutter with the drug.

QT-prolonging effects of sparfloxacin, a fluoroquinolone antibiotic, assessed in the in vivo canine model with monophasic action potential monitoring

Sparfloxacin, a fluoroquinolone antibacterial agent, prolongs cardiac repolarization, which may predispose to torsades de pointes. This study was designed to assess simultaneously the hemodynamic and electrophysiologic effects of sparfloxacin using the halothane-anesthetized, closed-chest in vivo canine model (n = 6). Sparfloxacin was intravenously administered in the following two doses with a pause of 20 min, a clinically relevant dose of 3.0 mg/kg/10 min and a 10 times higher dose of 30 mg/kg/10 min. After the low dose of sparfloxacin, cardiac output increased, heart rate decreased, and ventricular repolarization and refractory periods were prolonged. After the high dose, cardiac output increased, whereas heart rate and mean blood pressure decreased, and ventricular repolarization and effective refractory periods were prolonged. The increment was greater in repolarization than in refractoriness, indicating an increase of electrical vulnerability. Because sparfloxacin prolonged repolarization in a reverse use-dependent manner, its negative chronotropic effect may have potentiated the QT prolongation. Left ventricle preload, left ventricular contraction, and AV nodal as well as intraventricular conduction were minimally affected. These results suggest that caution should be used when administering sparfloxacin to patients having risk factors for QT prolongation.

Effect of magnesium sulfate on the haloperidol-induced QT prolongation assessed in the canine in vivo model under the monitoring of monophasic action potential

Haloperidol has been reported to induce polymorphic ventricular arrhythmias associated with QT prolongation. The present study examined the effects of magnesium sulfate on the cardiovascular system suffering from haloperidol overdose. Beagle dogs were anesthetized with halothane inhalation under the monitoring of monophasic action potential (n=6). After intravenous administration of an intentionally high dose of haloperidol (3 mg/kg), the heart rate (HR), left ventricular contraction and mean blood pressure (BP) decreased, and the ventricular repolarization phase and effective refractory period (ERP) were prolonged, the increment in the former being than in the latter, indicating an increase in electrical vulnerability. However, preload of the left ventricle, cardiac output (CO) and cardiac conduction were hardly affected. An additional intravenous dose of 100 mg/kg of magnesium sulfate increased the preload of the left ventricle, and decreased the HR, mean BP, left ventricular contraction and CO, suppressed atrioventricular as well as intraventricular conduction, and prolonged the ventricular repolarization phase and ERP, in which the increment of the repolarization phase was similar to that of ERP. These results suggest that magnesium sulfate hardly affects the electrical vulnerability of the heart during haloperidol overdose, but may block the calcium, potassium and sodium channels, which may explain its antiarrhythmic action.

Drug therapy of sustained ventricular tachyarrhythmias. Is there still a role?

This article provides a review of the risks faced by patients with sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) in the absence of a reversible or transient cause so that the goals of therapy can be clearly defined. The therapeutic approaches that have been proposed to achieve these goals are outlined and evidence comparing these various approaches to therapy is then summarized in order to propose an algorithm for the optimal use of antiarrhythmic drug therapies as primary therapy for selected VT/VF patients. Options for the ancillary uses of antiarrhythmic drug therapies in ICD patients are considered.

Late outcome of survivors of idiopathic ventricular fibrillation

This report describes clinical, hemodynamic, and electrophysiologic characteristics of 18 consecutive survivors of sudden cardiac arrest due to idiopathic ventricular fibrillation (VF) between 1986 and 1996. Long-term data in relation to the prescribed therapy are presented. The mean age of the 18 patients was 48 +/- 14 years (median 49). Electrophysiologic studies showed a low inducibility of sustained ventricular tachyarrhythmias in 4 patients (22%). Treatment consisted of class III agents, beta blockers, or implantable cardioverter-defibrillators. Two patients were discharged without any therapy. Therapy control was undertaken either by serial drug testing or by the empirical approach. Serious complications of therapy occurred in 2 patients: 1 patient experienced a proarrhythmic effect of antiarrhythmic drug therapy, and the other patient received multiple inadequate defibrillator discharges due to a defect in the transvenous lead. All but 1 patient (94%) remained free of recurrences of sudden cardiac arrest during a follow-up time of 45 +/- 29 months (median 41). One patient died 2 weeks after surviving cardiac arrest due to intractable VF while receiving sotalol treatment. Therapy guided by electrophysiologic studies did not have any impact on survival. Adverse effects or noncompliance led to discontinuation of drug therapy in 7 patients after a mean period of 31 +/- 30 months. Without any treatment 9 patients remained without recurrences over 45 +/- 33 months. Because of the absence of risk factors for arrhythmia recurrence and criteria to select therapy, randomized prospective studies are warranted to assess the optimal therapies in these young, ostensibly healthy patients.

Antiarrhythmic drug therapy in the management of atrial fibrillation

Antiarrhythmic drugs have been used for the acute conversion of atrial fibrillation to sinus rhythm, as well as for the long-term maintenance of sinus rhythm. In recent years, concerns regarding antiarrhythmic drug efficacy as well as safety have prompted a re-examination of the indications for antiarrhythmic therapy in patients with atrial fibrillation. This review will focus on the safety and efficacy of antiarrhythmic therapy in the acute and chronic management of patients with atrial fibrillation.

Torsades de pointes in two chronic renal failure patients treated with cisapride and clarithromycin

Patients with chronic renal failure are often on multiple medications and are at risk for the development of adverse effects from drug interactions. Two cases of torsades de pointes that followed the initiation of clarithromycin therapy in patients receiving long-term cisapride therapy are being reported. Elevated cisapride levels while on this combination with return to therapeutic range while on cisapride only was documented in one of the patients. The role of the inhibition of cytochrome P-4503A4 in the occurrence of the arrhythmia is discussed.

Electrophysiological mechanisms for ventricular arrhythmias in patients with myocardial ischemia: anesthesiologic considerations, Pt II

This is the second half of a two-part review article that discusses ventricular tachyarrhythmias, either induced by acute ischemia or consequent to chronic myocardial ischemia, and their anesthestic implications. The first half of the article was published in the June 1997 Issue of The Journal.

Signal-averaged ECG in patients with antidepressant therapy

The signal-averaged electrocardiography (SAECG) identifies patients at risk of ventricular arrhythmias and sudden cardiac death. Since the similarity has been known of the pharmacology of class I antiarrhythmics and tricyclic antidepressants, the potential proarrhythmic effects of antidepressants has become a particular problem. The influence of sodium channel blocking antidepressant drugs on the SAECG time-domain parameters was evaluated, using high-pass filters of 25 Hz and 40 Hz. SAECG was performed in 11 depressed patients with normal cardiac status before and for 4 weeks after antidepressant initiation. At the filter setting of 25 Hz, a significant worsening of all studied SAECG parameters (filtered QRS duration, low-amplitude signal duration, root mean square voltage in the first and in the last 40 ms of the filtered QRS) was found in our patient group. Using a 40 Hz high-pass filter, the results were similar. Antidepressant therapy significantly prolonged filtered QRS duration, significantly reduced root mean square voltages in the first and in the last 40 ms of the filtered QRS and non-significantly prolonged low amplitude signal duration. Amitriptyline and maprotiline induced late potentials (LP) in 2 patients at 40 Hz high pass filter setting. No patient had LP at 25-250 Hz. Our pilot study indicates that sodium channel blocking antidepressant drugs may affect SAECG variables similarly to class I antiarrhythmics. SAECG might be useful in categorizing of antidepressant agents and risk stratification of psychiatric patients.