![]() Normal AV conduction resumed after a single ventricular paced beat (not shown). As pacing was discontinued, after a short sinus pause, a complete infranodal block occurred ( Figure 2). However, at a paced cycle length of 500 milliseconds, a 2:1 infranodal block developed. Coronary sinus pacing at a cycle length of 600 milliseconds was associated with a 1:1 AV relationship. At this step, His bundle activity recording was available and showed a normal HV value (50 milliseconds) with normal intra-Hisian conduction. A complete bidirectional CTI block was achieved after additional radiofrequency energy applications. Immediately after AV conduction resumed, the PR interval was similar to that of baseline. Following a short pause, the acceleration of sinus rhythm rules out a potential vagal mechanism. After interruption of the flutter, a complete atrioventricular block occurs. The left part of the electrocardiogram tracing shows typical flutter waves in leads II, III, and aVF conducted in a 2:1 fashion to the ventricles. As AFL stopped, a 15-second asystole due to complete AVB occurred after a short sinus pause: this situation required a brief external cardiac massage before ventricular pacing could be available ( Figure 1). The AFL terminated during radiofrequency energy delivery in the CTI at the 6-o’clock position of the tricuspid annulus, which was defined in a 45° left anterior fluoroscopic view. Sustained typical counterclockwise AFL at a cycle length of 254 milliseconds then developed and was associated with a 2:1 AV response (heart rate 118 beats per minute). Intravenous flecainide (1 mg/kg, 10 mg/min) was given to control this arrhythmia. An electrophysiological study for assessing atrioventricular (AV) conduction and CTI ablation was performed.ĭuring the study, the patient exhibited multiple bouts of atrial fibrillation at ventricular rates of about 65 beats per minute. While undergoing treatment with the latter medication, the patient experienced 2 syncopal episodes, which prompted the present hospitalization. A typical AFL occurred later and was converted to sinus rhythm with treatment with oral amiodarone, which was replaced afterward by slow-release flecainide (200 mg/d). During the prior hospitalization, the electrocardiogram (ECG) showed sinus rhythm with a normal PR interval (0.18 second), a complete right bundle branch block, and a normal QRS axis. ![]() The syncope occurred 1 month after another hospitalization that was due to transient ischemic attack. A 74-year-old man with a history of hypertension and no obvious heart disease was referred for electrophysiological evaluation of recurrent syncope. ![]()
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