Background: The proximity of cardiac structures to the wall of the esophagus might allow a variety of trans-esophageal interventional procedures to be performed under EUS control. There will be concerns about safety and catastrophic bleeding of this moving target. The relative safety of mediastinal lymph node puncture at EUS suggests that some needle based trans-esophageal cardiac procedures might also be safe. Aim: To investigate the feasibility and safety of a variety of interventional trans-esophageal cardiac procedures in experimental studies in pigs and to report the use of EUS needle puncture in a few patients. Methods and Procedures: A variety of EUS-guided devices were tested in trans-esophageal survival experiments in pigs. These included 22 and 19 G needles, guide-wires, RF catheters, electrodes, pacing wires and injection of contrast agent into coronary arteries. Experimental procedures studied included: needle biopsy, contrast injection into the atrium, ventricle and coronary arteries, passage of a guide-wire into atrium and ventricle, direct intracardiac recording of ECG, cardiac conductive tissue ablation, direct cardiac pacing, wire guided RF valvotomy and ring contraction for valve incompetence using RF current. Results: Excellent views were obtained of posterior cardiac structures. It was easy to puncture the heart with EUS needles. Using 22 gauge needle electrodes ECG traces were obtained directly from the surface of the heart and also from intra-cardiac sites including those adjacent to the sinu-atrial and atrio-ventricular node. Using a Grass stimulator and EUS placed electrode, the heart was paced through the EUS scope. Coag diathermy was applied to the aortic and pulmonary rings and cutting diathermy to a needle through a leaflet of the aortic valve. A 22G needle was placed into the coronary arteries adjacent to the aortic valve root and to inject contrast into the artery. No bleeding or electrical instability was observed in these survival experiments. In 3 patients pericardial fluid was aspirated using a 22G needle. In 1 patient with an apparent intra-cardiac tumour thought to be a myxoma a 19G EUS biopsy showed that this structure was an organized thrombus. There were no complications. Conclusions: These studies suggest that some trans-esophageal intra-cardiac EUS procedures are feasible and that cautious extension of these preliminary experiments and experiences may be warranted. A small number of clinical cases are presented. Background: The proximity of cardiac structures to the wall of the esophagus might allow a variety of trans-esophageal interventional procedures to be performed under EUS control. There will be concerns about safety and catastrophic bleeding of this moving target. The relative safety of mediastinal lymph node puncture at EUS suggests that some needle based trans-esophageal cardiac procedures might also be safe. Aim: To investigate the feasibility and safety of a variety of interventional trans-esophageal cardiac procedures in experimental studies in pigs and to report the use of EUS needle puncture in a few patients. Methods and Procedures: A variety of EUS-guided devices were tested in trans-esophageal survival experiments in pigs. These included 22 and 19 G needles, guide-wires, RF catheters, electrodes, pacing wires and injection of contrast agent into coronary arteries. Experimental procedures studied included: needle biopsy, contrast injection into the atrium, ventricle and coronary arteries, passage of a guide-wire into atrium and ventricle, direct intracardiac recording of ECG, cardiac conductive tissue ablation, direct cardiac pacing, wire guided RF valvotomy and ring contraction for valve incompetence using RF current. Results: Excellent views were obtained of posterior cardiac structures. It was easy to puncture the heart with EUS needles. Using 22 gauge needle electrodes ECG traces were obtained directly from the surface of the heart and also from intra-cardiac sites including those adjacent to the sinu-atrial and atrio-ventricular node. Using a Grass stimulator and EUS placed electrode, the heart was paced through the EUS scope. Coag diathermy was applied to the aortic and pulmonary rings and cutting diathermy to a needle through a leaflet of the aortic valve. A 22G needle was placed into the coronary arteries adjacent to the aortic valve root and to inject contrast into the artery. No bleeding or electrical instability was observed in these survival experiments. In 3 patients pericardial fluid was aspirated using a 22G needle. In 1 patient with an apparent intra-cardiac tumour thought to be a myxoma a 19G EUS biopsy showed that this structure was an organized thrombus. There were no complications. Conclusions: These studies suggest that some trans-esophageal intra-cardiac EUS procedures are feasible and that cautious extension of these preliminary experiments and experiences may be warranted. A small number of clinical cases are presented.