Temporary atrial standstill

Persistent atrial standstill following the Cox-maze III procedure: reversal with sustained atrial pacing

Atrial standstill is a rare disorder of cardiac rhythm that is characterized by total absence of electrical activity in one or both atria. We report herein the case of a patient with atrial fibrillation and symptomatic 4.0 s pauses who received a ventricular demand pacemaker. The patient later underwent mitral valve replacement with a pericardial tissue valve and the Cox-maze III procedure for symptomatic mitral stenosis and atrial fibrillation. Following surgery, he developed atrial standstill and became pacemaker dependent. The pacemaker was later revised to an atrioventricular sequential pacemaker. Twelve hours after revision, atrioventricular sequential pacing was noted and mechanical function of the atria was confirmed by Doppler echocardiography.

Prolonged transient atrial electrical silence following termination of chronic atrial tachyarrhythmias

INTRODUCTION

Atrial standstill is a rare heterogeneous arrhythmia characterized by electrical and mechanical standstill and electrical inexcitability. A long-lasting progressive form is seen with cardiac and neuromuscular diseases, and a familial or idiopathic form may have a genetic basis. A transient form was described secondary to drug intoxication, electrolyte imbalance, cardiac inflammation, and ischemia.

METHODS

We investigated three patients with long-standing atrial tachyarrhythmia (AT) (atrial flutter in two, and focal atrial tachycardia in one). All patients underwent a complete electrophysiological study with mapping of right and left atrial activity and radiofrequency ablation (RF Abl) of AT.

RESULTS

Following RF Abl of AT, all three patients manifested transient atrial electrical silence in the absence of known reversible causes. Atrial electrical silence was observed when, following AT termination, an escape atrioventricular (AV) junctional rhythm (in two patients) and an escape VVI pacemaker rhythm (in one patient) showed transient ventriculo-atrial (VA) conduction block (up to 30 seconds). A dominant sinus rhythm was observed to return 30 minutes, 90 minutes, and 12 hours, respectively, in the three patients. Two patients received a dual chamber pacemaker and a decision was made not to upgrade the patient with VVI pacemaker.

DISCUSSION AND CONCLUSIONS

The present report expands the spectrum of the syndrome of atrial standstill and raises interesting questions regarding possible electrophysiologic mechanism(s) of prolonged post overdrive atrial standstill. The report suggests that chronic overdrive of sinus and subsidiary atrial pacemakers may result in calcium overloading of cardiac cells, which is known to cause suppression of pacemaker activity as well as increased intracellular resistance. These mechanisms can possibly result in either prolonged suppression of sinus and atrial pacemaker activity and/or pacemaker exit block.

Persistent atrial standstill in a cat

A domestic shorthaired cat was presented with a 1-month history of cardiomegaly and recurrent chylothorax. The heart rate was 130 beats/min and no P waves were present on a surface electrocardiogram. Thoracic radiographs and an echocardiogram demonstrated severe biatrial dilatation, pleural effusion and restrictive pleural disease. Permanent atrial standstill was suspected. Pleurocentesis was performed and therapy was started with enalapril, frusemide and aspirin. Intracardiac electrograms revealed no atrial activity, and atrial pacing failed to elicit atrial or ventricular depolarisations. The patient was euthanased. Necropsy showed severe atrial wall thinning with marked cardiocyte loss. Persistent atrial standstill is a rare disease in the cat. Clinical signs may have been due to loss of atrial function, ventricular diastolic dysfunction, bradycardia, neurohormonal activation and reduced atrial natriuretic peptide plasma concentrations.

Total atrial paralysis after permanent dual chamber cardiac pacing

A 73 year old woman with known ischaemic heart disease and ischaemic ventricular tachycardia underwent temporary dual chamber pacing as part of the treatment to suppress tachycardia. Insertion of a permanent dual chamber system seven days later was uncomplicated. Total atrial paralysis, with inability to pace the atrium or obtain an atrial electrocardiogram from four atrial sites, developed within 24 hours of the permanent system being implanted. Atrial electrical and mechanical function recovered over several weeks.