Permanent atrial standstill with irregular junctional ectopic rhythm mimicking atrial fibrillation

We present an interesting case of 'pseudo' atrial fibrillation which was further diagnosed as atrial standstill with irregular junctional ectopic rhythm during electrophysiologic study. A 56-year-old woman presented to a health facility with symptoms of palpitation, lightheadedness, and shortness of breath. Upon detection of irregular rhythm with narrow QRS complexes and no visible P waves on the electrocardiogram, newly developed atrial fibrillation was considered and a direct current cardioversion was performed, during which cardiac asystole developed necessitating cardiopulmonary resuscitation. The patient was then transferred to our institution. Echocardiographic examination showed biatrial dilatation, normal left ventricular systolic function, marked left ventricular hypertrophy, severe aortic stenosis, moderate mitral regurgitation, and severe tricuspid regurgitation. The electrocardiogram showed an irregular rhythm with narrow QRS complexes without any fibrillatory f waves and 24-hour Holter monitoring revealed three episodes of ventricular asystole lasting for more than 3.5 seconds. During the electrophysiologic study, no electrical activity was observed at the high and low levels of the right atrial lateral free wall and septal wall. The final diagnosis was established as atrial standstill and irregular junctional ectopic rhythm. The patient refused aortic valve replacement and died due to progression of the underlying disease one year following permanent pacemaker implantation..