Contrast echocardiography to reduce ionizing radiation associated with cardiac catheterization during pregnancy

The transponder system: a new method of precise catheter placement in the right atrium under echocardiographic guidance

The ability to localize catheters within the heart has gained importance with the use of percutaneous catheter ablation and the transseptal approach for valvuloplasty. A prototype interactive transponder catheter system, specifically designed to mark the catheter tip for echocardiographic visualization, was used to place catheters at the tricuspid anulus and the fossa ovalis in anesthetized dogs. Catheter tip location was marked by lesions produced by radiofrequency energy delivered at the distal catheter electrode. At autopsy, the center of the radiofrequency-induced lesion was located 2.8 +/- 0.7 mm from the edge of the lateral tricuspid anulus and 3.5 +/- 3.1 mm from the center of the fossa ovalis. The transponder catheter system offers the ability to precisely position catheters in the right atrium under echocardiographic guidance.

The echo-transponder electrode catheter: a new method for mapping the left ventricle

The ability to locate catheter position in the left ventricle with respect to endocardial landmarks might enhance the accuracy of ventricular tachycardia mapping. An echo-transponder system (Telectronics, Inc.) was compared with biplane fluoroscopy for left ventricular endocardial mapping. A 6F electrode catheter was modified with the addition of a piezoelectric crystal 5 mm from the tip. This crystal was connected to a transponder that received and transmitted ultrasound, resulting in a discrete artifact on the two-dimensional echocardiographic image corresponding to the position of the catheter tip. Catheters were introduced percutaneously into the left ventricle of nine anesthetized dogs. Two-dimensional echo-transponder and biplane fluoroscopic images were recorded on videotape with the catheter at multiple endocardial sites. Catheter location was marked by delivering radiofrequency current to the distal electrode, creating a small endocardial lesion. Catheter location by echo-transponder and by fluoroscopy were compared with lesion location without knowledge of other data. Location by echo-transponder was 8.7 +/- 5.1 mm from the center of the radiofrequency lesion versus 14 + 7.8 mm by fluoroscopy (n = 15, p = 0.023). Echo-transponder localization is more precise than is biplane fluoroscopy and may enhance the accuracy of left ventricular electrophysiologic mapping.