Diagnostic Implications of Atrial Vulnerability*

Abstract

Extrastimulation in the atrial vulnerable zone may result in atrial fibrillation or flutter (AFF), especially with stimulation of multiple atrial sites. However, the clinical relevance of such vulnerability to AFF is unknown. Therefore, single twice-threshold extrastimuli were applied at three disparate right atrial sites in 45 consecutive unmedicated patients without overt heart failure. Group I consisted of 12 patients with documented spontaneous paroxysms of AFF. AFF was duplicated in 9 to 12 patients using extrastimulation in the vulnerable zone (5 in sinus rhythm, 4 requiring atrial pacing at 120 beats/min). Group II consisted of 33 patients without documented AFF dispite monitoring. Vulnerability to AFF was found in 12 of 33 patients (4 in sinus rhythm, 8 requiring atrial pacing). The duration of induced AFF did not discriminate between the two groups. Among the 12 Group II patients vulnerable to AFF, 3 had rapid palpitations, 2 had undiagnosed rapid tachycardias, 1 had atrial tachycardias and 1 junctional tachycardias. In vulnerable patients, the pause after AFF correlated with the pause after atrial pacing, but only 1 of 11 Group II patients with sick sinus syndrome was vulnerable. Thus, paroxysmal AFF may be duplicated with the extrastimulus technique if sufficient arial sites are stimulated, providing a model for evaluation of these arrhythmias. But atrial vulnerability, even to extrastimulation at normal heart rates, may be seen in patients suspected of atrial tachyarrhythmia in the absence of documented AFF, and does not contribute to the diagnosis of sinoatrial dysfunction.

Dispersion of signal-averaged P wave duration on precordial body surface in patients with paroxysmal atrial fibrillation

“…These responses have been more frequently observed in patients with than without paroxysmal atrial fibrillation [1][2][3][4][5] . Right atrial mapping studies during sinus rhythm have shown that prolonged, fractionated atrial electrocardiograms were found more frequently and were more distributed within the entire right atrium in patients with than without paroxysmal atrial fibrillation [6] .…”

“…Electrophysiological studies by programmed atrial stimulation showed that the widened zones of repetitive atrial firing [1,2] , intra-atrial conduction delay [2][3][4] and fragmented atrial activity [2,4] were associated with paroxysmal atrial fibrillation. It was also reported, following right atrial endocardial mapping, that prolonged and fractionated atrial endocardial electrograms were frequently observed in patients with paroxysmal atrial fibrillation during sinus rhythm [6] .…”

Clinical Significance of the Atrial Fibrillation Threshold in Patients with Paroxysmal Atrial Fibrillation

“…As a parameter related to the induction of the arrhythmia, the "repetitive atrial firing zone" has been proposed by several investigators, 9 but others have found it a nonspecific phenomenon. 7,10,11 Furthermore, these parameters could not be applied to the evaluation of drug efficacy. For example, isoproterenol decreased the refractory period and improved conduction delay, while clinical application of isoproterenol does not necessarily terminate AF.…”

Interactions between a rapid atrial stimulator and a multiprogrammable ventricular demand pacemaker

“…1). VVI pacing lacks the ability to sense atrial activity, and in this situation, could theoretically at least, increase the frequency of atrial arrhythmias (Engel et al, 1979). Dual-chamber demand pacemakers may prove to be useful in this situation, but have been associated with pacemaker re-entry tachycardia in a number of patients (Duncan et al, 1982; Steg et al, 1982), and patients with the abnormalities seen in this case would seem to be prime candidates to develop this type of problem.…”