Hormone-electrolyte interactions in congestive heart failure: lessons from a 4,000-year-old Sumerian tablet

Arrhythmias in heart failure: current concepts of mechanisms and therapy

About one half of deaths in patients with heart failure are sudden, mostly due to ventricular tachycardia (VT) degenerating to ventricular fibrillation or immediate ventricular fibrillation. In severe heart failure, sudden cardiac death also may occur due to bradyarrhythmias. Other dysrhythmias complicating heart failure include atrial and ventricular extrasystoles, atrial fibrillation (AF), and sustained and nonsustained ventricular tachyarrhythmias. The exact mechanism of the increased vulnerability to arrhythmias is not known. Depending on the etiology of heart failure, different preconditions, including ischemia or structural alterations such as fibrosis or myocardial scarring, may be prominent. Reentrant mechanisms around scar tissue, afterdepolarizations, and triggered activity due to changes in calcium metabolism significantly contribute to arrhythmogenesis. Furthermore, alterations in potassium currents leading to action potential prolongation and an increase in dispersion of repolarization play a significant role. Treatment of arrhythmias is necessary either because patients are symptomatic or to reduce the risk for sudden cardiac death. The individual history, left ventricular function, electrophysiologic testing, and the signal-averaged ECG give useful information for identifying patients at risk for sudden cardiac death. The implantable cardioverter defibrillator (ICD) has evolved as a promising therapy for life-threatening arrhythmias. A potential role may exist for antiarrhythmic drugs, mainly amiodarone. There is growing evidence that patients with sustained VT or a history of resuscitation have the best outcome with ICD therapy regardless of the degree of heart failure. Many of these patients require additional antiarrhythmic therapy because of AF or nonsustained VTs that may activate the device. Catheter ablation or map-guided endocardial resection are additional options in selected patients but seldom represent the only therapeutic strategy.

Electrolyte disturbances in chronic heart failure: metabolic and clinical aspects

The pathophysiology of congestive heart failure (CHF) includes conditions (e.g., activation of the renin-angiotensin-aldosterone system) which, when combined with CHF therapies, make patients afflicted with this syndrome quite susceptible to electrolyte disturbances. The most commonly encountered are hyponatremia, hypokalemia, and hypomagnesemia. These derangements are of vast clinical importance; their development not only represents an immediate threat to the CHF patient (e.g., dysrhythmias secondary to hypokalemia), but are also indicative of underlying pathophysiologic events, an unfavorable clinical course, and occasionally an adverse therapeutic response. The optimal care of CHF patient includes the recognition and management of these electrolyte disturbances.

Risks and benefits of the treatment of heart failure. Current status

Congestive heart failure is an increasingly common patient problem. It is a multisystem disease that involves not only the heart but also the kidneys and neurohormonal systems. Any treatment for heart failure should address depressed contractility and exercise intolerance, as well as control compensatory mechanisms. There are many different approaches to the treatment of congestive heart failure: among the drugs used are diuretics, digitalis compounds, nitrates, calcium channel blockers, beta-blockers, beta-agonists, vasodilators, angiotensin-converting enzyme (ACE) inhibitors and the new phosphodiesterase inhibitors. The therapy usually involves a multiple drug treatment plan to achieve the maximum effect for the patient with the lowest incidence of side effects. Heart failure involves a large spectrum of patients with left ventricular dysfunction, and success at achieving treatment goals with these patients will vary with the severity of that symptom. A major concern is that increasing contractility may further damage the myocardium and shorten the survival of these patients, although there is as yet no evidence of such shortening. The new phosphodiesterase inhibitor drugs are an exciting development in the treatment of heart failure, because they add a dimension to the treatment for patients who are not sufficiently improved by a regimen of digoxin, diuretics and ACE inhibitors. Any new heart failure medication should be able to improve rest and exercise haemodynamics, maintain its benefits when given orally and result in an improved exercise capacity and quality of life, and prolonged survival.