Digoxin: its role in contemporary medicine.

Digoxin has been a key therapeutic for heart failure and atrial tachyarrhythmias for over 200 years following Withering's groundbreaking work depicting the therapeutic benefit of the common botanical foxglove in his 1785 monograph. The use of digoxin preceded any randomised evidence or even basic understanding of its mechanism of action. Over the past two decades, there has been mounting evidence further challenging the safety and efficacy of digoxin, while multiple other therapies for both heart failure and atrial tachyarrhythmias have proven to be more effective and safe. Altogether, digoxin still has an important role in contemporary pharmacotherapeutics, though its role remains controversial and should be reserved for selective patients and clinical situations, with careful attention to serum concentrations.

Orthostatic intolerance. A historical introduction to the pathophysiological mechanisms.

Several of the pathophysiological mechanisms resulting in orthostatic intolerance (ie, tachycardia) have been recognized individually over the course of the past 100 years or more. More recent definitions of the normal ranges of orthostatic blood pressure and heart rate changes have facilitated the recognition of pathogenetic disorders that are probably shared in various proportions between orthostatic intolerance and various types of orthostatic hypotension. These include autonomic dysfunction of (1) the leg veins almost invariably causing excessive gravitational blood pooling, usually associated with (2) hypovolemia of circulating erythrocytes and plasma that is probably attributable to impaired autonomic stimulation of erythropoietin production, renin release, and (less consistently) aldosterone secretion. Improved understanding of these apparent results of lower body dysautonomia should facilitate more effective therapy in the future.

Ventricular tachycardia: historical perspective.

Ventricular tachycardia is now diagnosed frequently in patients with organic heart disease. Although ventricular tachycardia was first demonstrated electrocardiographically 75 years ago, the natural history, fundamental mechanisms, and optimal management have remained elusive. Early observers commented on the rarity of occurrence and poor prognosis associated with this arrhythmia, yet with time, some patients with ventricular tachycardia were reported to survive for prolonged periods. Because of the sporadic nature of the arrhythmia and its variable prognosis, assessment of the efficacy of therapies has been difficult. A wide variety of treatments has been advocated with enthusiasm, but only a few have been consistently reported to be effective. Citation of historical data to claim benefit from new treatments should be viewed with caution.

Cardiac surgery for arrhythmias.

Cardiac arrhythmia surgery was initiated in 1968 with the first successful division of an accessory AV connection for the Wolff-Parkinson-White Syndrome. Subsequent surgical procedures included the left atrial isolation procedure and the right atrial isolation procedure for automatic atrial tachycardias, discrete cryosurgery of the AV node for AV nodal reentry tachycardia, the atrial transection procedure, corridor procedure and Maze procedure for atrial fibrillation, the right ventricular disconnection procedure for arrhythmogenic right ventricular tachycardia, the encircling endocardial ventriculotomy, subendocardial resection procedure, endocardial cryoablation, the Jatene procedure, and the Dor procedure for ischemic ventricular tachycardia. Because of monumental strides in the treatment of most refractory arrhythmias by endocardial catheter techniques during the past decade, the only remaining viable surgical procedures for cardiac arrhythmias are the Maze procedure for atrial fibrillation and the Dor procedure for ischemic ventricular tachycardia. Nevertheless, the 25-30 years of intense activity in the field of cardiac arrhythmia surgery provided the essential foundation for the development of these catheter techniques and represent one of the most exciting and productive eras in the history of medicine. In one short professional career, we have witnessed the birth of arrhythmia surgery, its adolescence as an "esoteric" specialty, its prime as an enlightening yet exhausting period, and finally its waning years as a source of knowledge and wisdom on which better methods of treatment have been founded. One could hardly ask for a more rewarding experience.

Teste de indução de taquicardia por reentrada eletrônica em pacientes portadores de marcapasso bicameral / Induced tachycardia test through electronic reentry in patients with dual-chamber pacemakers

Introdução: A taquicardia por reentrada eletrônica pode ser um efeito adverso em pacientes portadores de marcapassos bicamerais (DDD, DDDR e VDD) na presença de condução ventrículo-atrial. Pode ocorrer especialmente em pacientes cujos marcapassos apresentam falhas de comando e sensibilidade atrial ou falhas na programação. Material e Método: Foram avaliados 118 portadores de marcapasso bicameral, com implante por doença do nó sinusal (DNS) e bloqueio atrioventricular total (BAVT), por meio de monitoramento eletrocardiográfico computadorizado e programador/interrogador de marcapasso. Resultados: Taquicardias por reentrada eletrônica foram induzidas em 30 pacientes por meio de um protocolo que produziu perda de comando atrial, aumento da sensibilidade atrial, elevação da frequência de estimulação e redução...