Intracardiac echocardiography for immediate detection of intracardiac thrombus formation.

An 85-year-old man with persistent atrial flutter (AFL) with slow ventricular rate of 44/min, causing fatigue and presyncope, was referred for urgent treatment. In spite of thromboembolic risk scale value 4, he had not been treated with anticoagulants because of high risk of bleeding. The decision was made to perform urgent catheter ablation to interrupt and cure AFL. Intracardiac echocardiography probe was placed in the pulmonary artery and visualized left atrial appendage free from thrombus with its proper function. Heparin was administered and AFL stopped during energy application. Intracardiac echocardiography showed immediate thrombus formation in left atrial appendage owing to complete atrial standstill and no retrograde conduction during hemodynamically effective escape nodal rhythm. This case report shows that in patients with sinus node disease effective ablation of AFL with escape rhythm without retrograde conduction to the atria may result in complete 'electrically induced' atrial standstill and immediate thrombus formation.