The sequence of right and left atrial contractions was analysed in 8 patients during spontaneous sinus rhythm and paced left atrial rhythm. During sinus rhythm, the beginning or peak of the right atrial a wave invariably preceded the beginning or peak of the left atrial a wave by a median of 32 and 34 msec, respectively. During paced left atrial rhythm, the beginning or peak of the right atrial...

The current studies were designed to investigate the mechanisms in the intact anesthetized dog that control the release of atrial natriuretic factor (ANF). In vitro, mechanical stretch of atrial tissue produces an increased release of ANF. In vivo, changes in atrial pressure correlate positively with circulating ANF levels. The present investigations used 6 open-chest anesthetized dogs to evalu...

BACKGROUND Atrial fibrillation has a high incidence in patients wearing an implantable cardioverter defibrillator for ventricular tachyarrhythmias and may lead to palpitations, heart failure, angina, stroke and inappropriate defibrillator discharge. The aim of the study was to evaluate the efficacy of a dual chamber defibrillator with atrial antitachycardia functions in treating spontaneous atr...

Background-We studied atrial activation during induced atrial flutter in the canine sterile pericarditis model to test the hypothesis that the atrial flutter reentrant circuit includes a septal component. Methods and Results-We studied 10 episodes of induced, sustained (>5 minutes) atrial flutter in 9 dogs. In all episodes, the reentrant circuit included a septal component. In 6 episodes, there...

OBJECTIVE To evaluate the incremental antifibrillatory effect of multisite atrial pacing compared with right atrial pacing in patients with drug refractory paroxysmal atrial fibrillation paced for arrhythmia prevention alone. METHODS In 20 of these patients (mean (SD) age 64 (8) years; 14 female, six male), a single blinded randomised crossover study was performed to investigate the increment...

Atrial fibrillation (AF) induces a progressive dilatation of the atria which in turn might promote the arrhythmia. The mechanism of atrial dilatation during AF is not known. To test the hypothesis that loss of atrial contractile function is a primary cause of atrial dilatation during the first days of AF, eight goats were chronically instrumented with epicardial electrodes, a pressure transduce...

BACKGROUND Atrial standstill manifests as absence of any atrial electrical activity in the surface ECG leads. Persistent atrial standstill secondary to acute myocarditis is extremely rare. CASE REPORT 10-year-old girl had atrial standstill and heart failure due to acute myocarditis. After recovery from myocarditis, heart failure resolved, but the atrial standstill persisted. OUTCOME Persist...

A patient with atrial tachycardia presented with dyspnoea on exertion. Transoesophageal echocardiography revealed idiopathic left atrial appendage stenosis. The mouth of the atrial appendage was narrowed, and there was a high velocity to and fro jet between the left atrial body and the left atrial appendage. The study, therefore, suggested isolated left atrial appendage orifice stenosis.

We present a case of a single chamber atrial pacemaker implanted for sinus node dysfunction and treatment of macroreentrant atrial tachycardias with atrial antitachycardia pacing. The patient presented with sustained atrial tachycardia above the detection rate, however, the device was unable to detect the tachycardia and did not deliver the programmed therapy. We discuss the nuances of the atri...

Background Slight variation in cycle lengths of common and rapid atrial flutter in humans is an established phenomenon, but its mechanisms have not been completely clarified. In a previous study, we demonstrated that in common atrial flutter the variations in atrial cycle length were due to atrial stretch affecting the revolution time of a reentrant circuit. In the present study, we investigate...