Edward K. Chung

A Reappraisal of Atrial Dissociation

Abstract Although the existence of atrial dissociation has been doubted by some investigators, various clinical observations have provided further evidence for the true occurrence of this interesting arrhythmia. Atrial dissociation is characterized by a unilateral ectopic atrial rhythm independent of the basic rhythm. The basic rhythm and the unilateral atrial rhythm never interfere with each other, and the latter is always confined to a small or large portion of one atrium. The most important diagnostic feature of this arrhythmia is the independent atrial rhythm, which is never conducted to the ventricles. The unilateral atrial rhythm is commonly a slow rhythm; less commonly, unilateral atrial fibrillation or flutter and, rarely, unilateral atrial tachycardia may be observed. Atrial dissociation must be differentiated from atrial parasystole and various artifacts that may resemble unilateral atrial rhythm. The electrocardiogram after cardiac transplantation produces findings very similar or even identical to those of atrial dissociation. When atrial dissociation is observed, it is nearly always in critically ill patients with intractable congestive heart failure and generally occurs a few hours before death.

Unusual form of digitalis-induced triple A-V nodal rhythm

Abstract An instance of digitalis-induced triple A-V nodal rhythm has been described. To my knowledge, it is the first arrhythmia reported. The necessity of early recognition of digitalis intoxication in elderly patients who develop A-V nodal arrhythmias, particularly those multifocal in origin, during digitalization has been emphasized.

Recognizing digitalis toxicity in patients with artificial pacemakers.

In a patient with ventricular rhythm induced by an artificial cardiac pacemaker, the clue to diagnosis of digitalis intoxication lies in electrocardiographic recognition of altered atrial mechanism, particularly the appearance of retrograde P waves. Recognition of ventricular premature contractions is also very important. Illustrative cases of all the arrhythmias detected in 20 pacemaker patients with digitalis toxicity are presented.

Drug Therapy for Cardiac Arrhythmias

Antiarrhythmic agents are indispensable in restoring normal cardiac rhythm in an emergency and in maintaining it once the emergency has passed. An understanding of the mechanism of the arrhythmia and of the physiologic and pharmacologic actions of the drug is a prerequisite for successful therapy.

Serum digoxin determination by radioimmunoassay. Clinical implications.

Used in conjunction with a thorough clinical and electrocardiographic evaluation, determination of serum digoxin concentration is an effective tool for assessing digitalis intoxication or underdigitalization due to various causes. The radioimmunoassay technic is recommended for its speed, sensitivity, and precise results.

Guide to the use of Artificial Pacemakers

In comparison with the fixed-rate pacemaker, the demand type of artificial pacemaker has the advantage of avoiding competition between natural and pacemaker rhythms. Demand pacemaker function can be tested with a special external device that temporarily speeds the rate. Atrial-synchronized pacemakers have recently gained favor because they can meet varying physiologic requirements and thus are well suited to young, active persons.

Guide to Managing Digitalis Intoxication

The first thing to do for a patient with digitalis intoxication is to discontinue the digitalis. If toxicity is severe, the patient belongs in the intensive care or coronary care unit. Potassium is an effective antiarrhythmic agent when used according to strict rules. Among the many other agents given for digitalis-induced arrhythmias, diphenylhydantoin is probably the safest and most effective.

Guide to Digitalis Therapy

The “usual” dosage of digitalis is only a guide. Different patients need different amounts of the drug, and numerous factors can and do intervene to change the requirements. Dosage must be carefully adjusted according to age and also in the presence of hypokalemia, preexisting hypercalcemia, advanced heart disease, endocardial fibrosis, or the Wolff-Parkinson-White syndrome.

Ventricular bigeminy masquerading as total electrical alternans: In a case of probable tuberculous pericarditis∗

Abstract An unusual electrocardiographic finding simulating total electrical alternans in a 45 year old woman with a recent history of pericardial effusion is reported. Findings obtained on subsequent tracings made clear that the original tracing had disclosed an unusual form of ventricular bigeminy produced by ventricular fusion beats appearing consecutively. This correct interpretation eliminated an unnecessary delay of surgery for active cavitary pulmonary tuberculosis.

Use and Abuse of Carotid Sinus Stimulation

The effect of carotid sinus stimulation on a tachyarrhythmia, or sometimes the absence of an effect, can be helpful in differential diagnosis. The procedure is also used in therapy of some arrhythmias. Abuse relates to the danger of inducing ventricular fibrillation in patients with digitalis intoxication and to the possibility of precipitating long ventricular standstill in elderly persons.