Background-The vein of Marshall (VOM) is an attractive target during ablation of atrial fibrillation because of its autonomic innervation, its location anterior to the left pulmonary veins, and its drainage in the coronary sinus. Methods and Results-We studied 17 dogs. A coronary sinus venogram showed a VOM in 13, which was successfully cannulated with an angioplasty wire and balloon. In 5 dogs, electroanatomical maps of the left atrium were performed at baseline and after ethanol infusion in the VOM, which demonstrated a new crescent-shaped scar, extending from the annular left atrium toward the posterior wall and left pulmonary veins. In 4 other dogs, effective refractory periods (ERP) were measured at 3 sites in the left atrium, before and after high-frequency bilateral vagal stimulation.

Multiple imaging modalities are employed independent of one another while managing complex cardiac arrhythmias. To combine electrical, anatomical, and functional imaging in a single catheter system, we developed a balloon catheter that carried 64 electrodes on its surface and an intracardiac echocardiography (ICE) catheter through a central lumen. The catheter system was inserted, and the balloon was inflated inside the left ventricle (LV) of eight dogs with 6-wk-old infarction, created by occlusion in the left anterior descending coronary artery. Anatomy was constructed by ICE imaging (9 MHz) through the balloon. Single-beat noncontact mapping (NCM) was performed via the multielectrode array to reconstruct unipolar endocardial electrograms during sinus rhythm. Standard contact mapping (CM) of the endocardium was also carried out for reference. Myocardial infarction in anterior LV extending from the middle to apical regions was localized both by ICE and NCM and validated by CM and pathology. The overall difference in the activation times between NCM and CM was 3 +/- 1 ms. Unipolar voltage in infarcted middle anterior LV was smaller than the voltage in normal middle inferior LV both by NCM (11 +/- 4 vs. 16 +/- 3 mV; P = 0.002) and CM (11 +/- 3 vs. 20 +/- 4 mV; P < 0.001). Unipolar voltage was also inversely related to infarct transmurality, both by NCM (r = -0.87; P = 0.005) and CM (r = -0.94; P < 0.001). The infarct area by ICE (7.7 +/- 2.9 cm(2)) was in agreement with CM (bipolar voltage, <1 mV; and area, 7.6 +/- 3.3 cm(2); r = 0.80; P = 0.016). Meanwhile, the voltage threshold that depicted the infarct area by NCM was directly related to the smallest unipolar voltage reconstructed within the infarct (r = 0.96; P < 0.001). In conclusion, combining NCM and ICE imaging in a single catheter system is feasible. The preclinical development of such an integrated system and its evaluation in experimental myocardial infarction demonstrate capabilities for single-beat mapping at multiple sites as well as the online assessment of anatomy and myocardial function.

The vein of Marshall (VOM) is an attractive target during ablation of atrial fibrillation due to its autonomic innervation and its location anterior to the left pulmonary veins and drainage in the coronary sinus. We studied 14 dogs. A coronary sinus venogram showed a VOM in 10, which was successfully cannulated with an angioplasty wire and a 2 mm balloon. In 5 dogs, electroanatomical (Carto) maps of the left atrium were performed at baseline and after ethanol (100%, 4 – 8 cc) was infused in the VOM, which demonstrated the creation of a new crescent-shaped scar in the left atrium, extending from the annular left atrium towards the posterior wall and left pulmonary veins. In 4 dogs, both cervical vagal trunks were isolated in the carotid sheath and cuff stimulation electrodes were attached to them. Effective refractory periods (ERP) were measured in 3 sites of the left atrium, before and after high-frequency bilateral vagal stimulation. The baseline ERP was 113.6±35.0 ms, and decreased to 82.2±25.4 ms (p<0.05) after vagal stimulation. After alcohol infusion in VOM, vagally-mediated ERP decrease was eliminated (from 108±27.2 ms to 95.6 ±16.7ms, p=NS). This elimination of vagal effects was not uniform and was limited in sites in proximity with the VOM (baseline ERP 105±18.7ms vs post vagal 98.±37.6ms, p=NS, as opposed to 106.7±27.1ms vs post vagal 73.3±19.7ms, p<0.05, in sites remote to VOM). We also tested feasibility of VOM alcohol infusion in humans: 2 patients undergoing pulmonary vein antral isolation had successful VOM cannulation: left atrial voltage maps demonstrated new scar involving the infero-posterior left atrial wall extending towards the left pulmonary veins. Retrograde alcohol infusion in the VOM achieves significant left atrial tissue ablation, abolishes local vagal responses and is feasible in humans.

Electrical impedance tomography (EIT) detects tissue composition inside a medium by determining its resistive properties, and uses various electrode configurations to pass a small electric current and measure corresponding potential. We investigated the feasibility of reconstructing scarred tissue inside the heart wall by employing EIT on the basis of a catheter carrying a plurality of electrodes and placed inside the blood-filled heart cavity. We built a computer model of the biological medium, and reconstructed the resistivity distribution using the finite element method and Tikhonov regularization. The results established the successful implementation of the numeric methods and the possibility of localizing and quantifying scarred myocardium. Novel application of EIT from inside the heart cavity could be useful during catheterization and may complement other diagnostic modalities. Further research is necessary to assess the impact of several factors on the accuracy of the reconstruction and include number of electrodes, catheter location, and scar size.