PMC9427300_01
(a) 12-lead surface ECG before the intervention.(b) 12-lead surface ECG after the intervention with no change in the PQ interval.
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fig1
In the current 12-lead electrocardiogram, we detected a normal sinus rhythm with a first-degree atrioventricular block (PR interval 216 ms) as shown in Figure 1. Thereafter, no tachycardia could be induced, dual AV node physiology was no longer present, and the first-degree AV block remained unchanged (Figure 1).
(a) Fluoroscopy of a dilated vena azygos (arrows) with inflow into the superior vena cava and the right atrium (p.a. projection). (b) Fluoroscopy of the coronary sinus (arrows), LAO 30 . (c) Fluoroscopy of the ablation catheter (arrow) via internal jugular vein placed in the area of the coronary sinus ostium (posteroseptal) during ablation, LAO 30 .
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fig2
Next, a venous angiography was performed (Figure 2) which revealed that the coronary sinus was accessible through the azygos vein (Figure 2). A stable position of the ablation catheter was established in the same location posteroseptally at the ostium of the coronary sinus (Figure 2).
Chest radiograph showing a prominent upper right mediastinum (arrow) as the correlation of the azygos continuation entering the vena cava superior in a cross-sectional view.
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fig3
A chest radiograph featured a suspicious configuration of the upper right mediastinum (Figure 3).
(a) Stretched reconstruction of a venous CT with azygos continuation (green arrows), aorta (white arrow), and diaphragmatic passage of the azygos (green circle). (b) Axial CT view, venous phase, showing a prominent azygos vein (green arrow). (c) 3D reconstruction showing the azygos continuation/superior vena cava (red) and the aortic arch (blue) in a right lateral and posterior view.
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fig4
Further diagnostics using contrast CT angiogram confirmed a rare anomaly: atresia of the inferior vena cava below the hepatic vein with azygos persistence (Figure 4).
His bundle electrogram (red arrows) immediately performed before the second ablation attempt (**atrioventricular (AV) interval of 128 ms; *His-ventricular (HV) interval of 48 ms).
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fig5
Recording of His bundle activity prior to ablation could be achieved 15 mm above the ostium of the coronary sinus only with the ablation catheter and resulted in an atrioventricular (AV) interval of 128 ms and His-ventricular (HV) interval of 48 ms (Figure 5).
Electrogram of the ablation (black arrow: ablation start; red arrows: junctional beats after application of radiofrequency (RF)). A small A and a large V potential were recorded immediately before the ablation.
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fig6
Tissue contact during ablation was adequate, verified by an impedance drop of >10% and occurrence of junctional beats during radiofrequency (RF) delivery in a typical right posteroseptal position at the ostium of the coronary sinus (Figure 6).