case_images: PMC11733771_01
case_images: A 12-lead electrocardiogram was recorded at 10 mm/mV and 25 mm/s, revealing atrial flutter with a ventricular rate of 42 beats/min, a flutter cycle length of 290 ms, and right ventricular hypertrophy.
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case_images: The 12-lead electrocardiogram (Figure 1) showed an atrial flutter rhythm, characterized by negative F-waves in V1 and positive waves in leads II, III, and aVF, with a flutter cycle length of 290 ms. Post-stimulation intervals along the isthmus matched the flutter cycle length, and concealed entrainment was observed (see Supplementary material online, Figure S1).
case_images: Cardiac computed tomography angiography and intracardiac echocardiography. (A) Cardiac computed tomography angiography reveals a morphologically right systemic single ventricle and a dilated common atrium, along with the absence of an interatrial septum and a single atrioventricular valve. The single ventricle exhibits a double-outlet configuration. (B) Intracardiac echocardiography. In the home view, the common atrium, single ventricle, and single atrioventricular valve are visualized. The moment of cavo-annular isthmus ablation guided by intracardiac echocardiography is also depicted. CA, common atrium; SV, single ventricle; P, pulmonary artery; Ao, ascending aorta; SVOT, single ventricle outflow tract; AV, aortic valve.
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case_images: Finally, the coronary arteries had independent origins, with the right coronary artery and the left coronary trunk arising from the left sinus of Valsalva (Figure 2A and Supplementary material online, Videos S1 and S2). Through the left femoral vein, an intracardiac ultrasound probe was advanced to the mid-atrium to obtain an image resembling the home view (Figure 2B and Supplementary material online, Video S3). A conduction time through the isthmus was determined, measured from the ablation catheter to the Halo catheter, being 196 ms, with a linear activation pattern from proximal to distal (see Supplementary material online, Figure S2), suggesting complete conduction block across the isthmus.
case_images: (A) Catheter positioning: duodecapolar catheter (Halo, blue arrow), decapolar catheter at the entrance of the superior vena cava (green arrow), and ablation catheter at the cavo-annular isthmus (red arrow) in the left anterior oblique fluoroscopy view. (B) Endocardial electrograms from the duodecapolar Halo catheter, decapolar catheter at the upper wall of the single atrium (coronary sinus [CS] 1-4), and surface electrocardiogram. The activation sequence of the single atrium is noted, beginning at CS 1-2 and ending at Halo 1 (counterclockwise activation).
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case_images: Through the right femoral vein, a steerable duodecapolar catheter (Steerable Duo-decapolar Mapping Catheter) was advanced and positioned on the lateral wall and cavo-annular isthmus (Figure 3A). The activation sequence of the atrial flutter was recorded, confirming a counterclockwise activation pattern (Figure 3B). After the ablation, the patient presented with sinus rhythm at 65 beats/min (see Supplementary material online, Figure S3) and intermittent second-degree Mobitz I atrioventricular block.
case_images: CARTO-Merge  (biosense webster): (A) posteroanterior view, (B) anteroposterior view, (C) right anterior oblique view, and (D) left anterior oblique view. The aneurysmal common atrium with a single atrioventricular valve is shown. The right and left superior vena cava drain into the roof of the right and left portions of the common atrium, respectively. The inferior vena cava drains into the left portion of the common atrium. All four pulmonary veins drain into the left portion of the posterior wall of the common atrium.
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case_images: The device was programmed in the dual-chamber pacemaker mode (DDD) (see Supplementary material online, Figure S4).
case_images: Voltage and activation map of the common atrium. (A) The ablation catheter is shown in the isthmus, with red spheres indicating the ablation points. (B) Real-time electrograms during ablation showing the moment when the macroreentrant circuit is interrupted, transitioning into sinus bradycardia rhythm.
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case_images: With the diagnosis of atrial flutter involving the common atrioventricular valve, an ablation line was created along the cavo-annular isthmus (red spheres in Figure 5A), successfully terminating the arrhythmia (Figure 5B and Supplementary material online, Video S5). Complete success was determined by the termination of atrial flutter and the creation of an ablation line along the cavo-annular isthmus (Figure 5 and Supplementary material online, Video S5).