"Torsade de Pointes" in Patients with Structural Heart Disease and Atrial Fibrillation Treated with Amiodarone, beta-Blockers, and Digitalis

Device therapy in heart failure with reduced ejection fraction-cardiac resynchronization therapy and more

In patients with heart failure with reduced ejection fraction (HFrEF), optimal medical treatment includes beta-blockers, ACE inhibitors/angiotensinreceptor-neprilysin inhibitors (ARNI), mineralocorticoid receptor antagonists, and ivabradine when indicated. In device therapy of HFrEF, implantable cardioverter-defibrillators and cardiac resynchronization therapy (CRT) have been established for many years. CRT is the therapy of choice (class I indication) in symptomatic patients with HFrEF and a broad QRS complex with a left bundle branch block (LBBB) morphology. However, the vast majority of heart failure patients show a narrow QRS complex or a non-LBBB morphology. These patients are not candidates for CRT and alternative electrical therapies such as baroreflex activation therapy (BAT) and cardiac contractility modulation (CCM) may be considered. BAT modulates vegetative dysregulation in heart failure. CCM improves contractility, functional capacity, and symptoms. Although a broad data set is available for BAT and CCM, mortality data are still lacking for both methods. This article provides an overview of the device-based therapeutic options for patients with HFrEF.

Clinical Use of Digitalis: A State of the Art Review

The history of digitalis is rich and interesting, with the first use usually attributed to William Withering and his study on the foxglove published in 1785. However, some knowledge of plants with digitalis-like effects used for congestive heart failure (CHF) was in evidence as early as Roman times. The active components of the foxglove (Digitalis purpurea and Digitalis lanata) are classified as cardiac glycosides or cardiotonic steroids and include the well-known digitalis leaf, digitoxin, and digoxin; ouabain is a rapid-acting glycoside usually obtained from Strophanthus gratus. These drugs are potent inhibitors of cellular membrane sodium-potassium adenosine triphosphatase (Na⁺/K⁺-ATPase). For most of the twentieth century, digitalis and its derivatives, especially digoxin, were the available standard of care for CHF. However, as the century closed, many doubts, especially regarding safety, were raised about their use as other treatments for CHF, such as decreasing the preload of the left ventricle, were developed. Careful attention is needed to maintain the serum digoxin level at ≤ 1.0 ng/ml because of the very narrow therapeutic window of the medication. Evidence for benefit exists for CHF with reduced ejection fraction (EF), also referred to as heart failure with reduced EF (HFrEF), especially when considering the combination of mortality, morbidity, and decreased hospitalizations. However, the major support for using digoxin is in atrial fibrillation (AF) with a rapid ventricular response when a rate control approach is planned. The strongest support of all for digoxin is for its use in rate control in AF in the presence of a marginal blood pressure, since all other rate control medications contribute to additional hypotension. In summary, these days, digoxin appears to be of most use in HFrEF and in AF with rapid ventricular response for rate control, especially when associated with hypotension. The valuable history of the foxglove continues; it has been modified but not relegated to the garden or the medical history book, as some would advocate.

Towards a better understanding of QT interval variability

The International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) Guideline E14 recommends 'Thorough QT Study' as a standard assessment of drug-induced QT interval prolongation. At the same time, the value of drug-induced QTc prolongation as a surrogate marker for risk of life-threatening polymorphic ventricular tachycardia known as torsades des pointes remains controversial. Beat-to-beat variability of QT interval was recently proposed as an alternative metric. The following review addresses mechanisms of beat-to-beat QT variability, methods of QT interval variability measurements, and its prognostic value in clinical studies.

Pleiotropic effects of antiarrhythmic agents: dronedarone in the treatment of atrial fibrillation

Atrial fibrillation remains the most common arrhythmia in clinical practice. Dronedarone is an antiarrhythmic drug for the maintenance of sinus rhythm in patients with atrial fibrillation. Dronedarone is an amiodarone derivative developed to reduce the number of extracardiovascular side effects. Dronedarone has undergone extensive experimental and clinical testing during the last decade. On the aggregate, these studies have highlighted a complex set of pleiotropic actions that may contribute to dronedarone's antiarrhythmic effects. In this review, we summarize the clinical studies that have evaluated dronedarone and provide an overview of dronedarone's electrophysiological and nonelectrophysiological pleiotropic actions.

Intracardiac QT variability in patients with structural heart disease on class III antiarrhythmic drugs

We previously showed that increased intracardiac repolarization lability predicts life-threatening ventricular arrhythmias in patients with structural heart disease. Patients with structural heart disease frequently take antiarrhythmic drugs (AADs), which directly affect repolarization. The effect of AADs on the predictive value of repolarization lability is unknown. We hypothesized that increased intracardiac beat-to-beat QT variability predicts sustained ventricular tachyarrhythmias in structural heart disease patients on class III AADs. Intracardiac electrograms and surface electrocardiogram were simultaneously recorded at rest for 5 minutes in 500 patients (mean +/- SD age, 61 +/- 14 years; 368 male [74%]) with implanted implantable cardioverter-defibrillator for primary (295 patients, or 79%) or secondary prevention of sudden cardiac death. Mean (SD) follow-up currently reached 24.8 (11.7) months. Intracardiac QT variability index was an independent predictor of ventricular tachycardia/ventricular fibrillation events and fast ventricular arrhythmias with cycle length of 240 ms or less in the multivariate Cox model. Intracardiac QT variability was higher in patients on class III AADs than in those not taking these drugs. Increased intracardiac QT variability after adjustment for class III AADs use carried independent risk of life-threatening ventricular tachyarrhythmias.

"Torsade de pointes" during amiodarone infusion in a cirrhotic woman with a prolonged QT interval

We describe an interesting case of a woman with decompensated cirrhosis, ischaemic heart disease and prolonged QT interval, who developed a new-onset atrial fibrillation. During amiodarone infusion a torsade de pointes occurred, which was immediately converted to sinus rhythm by synchronized cardioversion. A new episode of atrial fibrillation was treated with infusion of a beta-blocker (metoprolol) that restored sinus rhythm and normalized the QT interval. Delayed repolarization, frequently observed in ischaemic heart disease, cirrhosis and pro-arrhythmic drugs administration, represents the background for the development of torsade de pointes. Our report underlines that the potential harmfulness of a prolonged QT interval in cirrhotic patients is currently not perceived in its entirety, so that various categories of drugs affecting ventricular repolarization are rather thoughtlessly used in clinical practice without monitoring the QT interval. Thus, amiodarone should be avoided, if possible, or used with extreme care in arrhythmic patients with advanced liver disease. Moreover, beta-blockers may be considered the first-line treatment for rate-control during supraventricular tachyarrhythmias in cirrhotic patients with delayed repolarization.

Augmentation of late sodium current unmasks the proarrhythmic effects of amiodarone

AIM

Clinical use of amiodarone is associated with occasional development of torsade de pointes (TdP). However, preclinical models have failed to demonstrate the proarrhythmic potential of amiodarone. The objective of this study was to reveal and explain the pro- and anti-arrhythmic effects of acute exposure to amiodarone in an animal model.

METHODS AND RESULTS

Endo- and epicardial monophasic action potentials (MAPs) and 12-lead electrocardiogram were recorded in female rabbit isolated hearts. Ion channel currents were measured in human embryonic kidney cells expressing SCN5A Na+ and HERG K+ channels. Acute amiodarone alone caused an insignificant increase in duration of MAP (MAPD90) without causing TdP. In the presence of 3 nM sea anemone toxin (ATX-II), amiodarone (1-30 nM) prolonged MAPD90 from 217 +/- 5 to 250 +/- 8 ms (n = 16, P < 0.01), increased transmural dispersion of repolarization (TDR) from 59 +/- 9 to 70 +/- 10 ms and beat-to-beat variability (BVR) of MAPD(90) from 0.75 +/- 0.03 to 1.06 +/- 0.13 ms (P < 0.05). At 30-300 nM, amiodarone induced TdP in 16 out of 17 hearts. A further increase of amiodarone concentration to 1-10 microM abbreviated MAPD(90) to 211 +/- 9 ms, decreased BVR to 0.5 +/- 0.01 ms, decreased TDR (n = 7, P < 0.05), and suppressed TdP. Amiodarone inhibited HERG K+ and late Na+ currents with IC50s of 0.8 +/- 0.1 and 3.0 +/- 0.9 microM, respectively.

CONCLUSION

In hearts in which late INa is augmented to mimic congenital or acquired pathological conditions, amiodarone has a concentration-dependent biphasic effect to induce and then suppress arrhythmic activity, secondary to inhibition of HERG K+ and late Na+ currents. This is the first preclinical model demonstrating the potential for amiodarone to induce TdP.

A practical guide for clinicians who treat patients with amiodarone: 2007

Amiodarone is commonly used to treat supraventricular and ventricular arrhythmias in various inpatient and outpatient settings. Over- and under-use of amiodarone is common, and data regarding patterns of use are sparse and largely anecdotal. Because of adverse drug reactions, proper use is essential to deriving optimal benefits from the drug with the least risk. This guide updates an earlier version published in 2000, reviews indications for use of amiodarone and recommends strategies to minimize adverse effects. The recommendations included herein are based on the best available data and the collective experience of the member of the writing committee.