Background: Ablation of the vein of Marshall (VOM) by dehydrated ethanol (DE) is an important method for completely blocking the mitral isthmus (MI). Before DE ablation of the VOM, Marshall angiography should be performed so that the contrast medium is inevitably exposed to DE. Method:We present a case of DE ablation of the VOM. When iodixanol was exposed to DE, some floccule embolized the lumen of the over-the-wire (OTW) balloon dilatation catheter and led to the impossibility of DE ablation. Then, we performed in vitro experiments: iodixanol, not iomeprol, produced many stable white floccules when it encountered DE. Conclusion:Iodixanol is not an appropriate contrast for DE ablation of the VOM. However, if there is no other alternative contrast, the following methods might be used to address the problem: (1) diluted iodixanol (iodixanol:normal saline 1:1) could be used for VOM ablation; or (2) the lumen of the OTW could be flushed by NS after VOM angiography, and then DE injection could be performed.

Aim: To evaluate the accuracy of the diagnostic criteria for determining the origin of outflow tract ventricular arrhythmia (OTVA) and develop an electrocardiography (ECG) algorithm to predict its origin. Method: We analyzed the ECGs of 100 patients with OTVA who underwent successful ablation. The QRS complex was measured during sinus rhythm and ventricular arrhythmia (VA). After the ECG algorithm was developed, it was validated in an additional 100 patients from two different hospitals. Results: In this retrospective study, among the parameters without restrictions in the transition lead, the V2S/V3R index (AUC = 0.89) was significantly better in predicting VA originating from the right ventricular outflow tract (RVOT). Further, the larger ISA in V1 and V2 (AUC = 0.90) was significantly better in predicting VAs originating from the left ventricular outflow tract (LVOT). Among the parameters with the transition lead in V3, the V2S/V3R index (AUC = 0.82) was significantly better in predicting VAs originating from the RVOT. On the other hand, the V3 R-wave deflection interval (AUC = 0.81) was significantly better in predicting VAs originating from the LVOT. The algorithm combining the V2S/V3R index and the larger ISA in V1 and V2 could predict OTVA origin with an accuracy of 85.00%, a sensitivity of 75.68%, a specificity of 90.48%, a positive predictive value (PPV) of 82.35%, and a negative predictive value (NPV) of 86.36%. In the validation study, the algorithm exhibited excellent accuracy (95.00%) and AUC (AUC = 0.95), with a sensitivity of 94.12%, a specificity of 95.45%, a PPV of 91.43%, and an NPV of 96.92%. Conclusion: Our developed algorithm can reliably predict OTVA origin without restrictions in the transition lead.