Intracardiac ultrasound imaging during transseptal catheterization.

STUDY OBJECTIVE: The purpose of this study was to assess the feasibility of using small 12.5- or 20-MHz intracardiac ultrasound catheters to image the fossa ovalis and guide transseptal catheterization. DESIGN: The study was performed in three phases. First, in vitro imaging of human autopsy hearts was performed to define the intracardiac ultrasound appearance of the fossa ovalis and transseptal apparatus. Subsequently, the optimum approach for imaging the fossa ovalis in vivo was established in 30 patients. Finally, intracardiac ultrasound imaging was performed during transseptal catheterization of 10 patients undergoing percutaneous mitral commissurotomy. INTERVENTIONS: Intracardiac ultrasound imaging was performed with a 12.5- or 20-MHz single-element mechanical device in which a central imaging core is rotated within a 6F polyethylene sheath. MEASUREMENTS AND RESULTS: In both in vitro and in vivo studies, the fossa ovalis was easily identifiable as a thin membranous region surrounded by the thicker muscular portion of the interatrial septum. Initial in vivo studies established venous access by the femoral route to be superior to the internal jugular approach for catheter introduction. Studies performed during transseptal catheterization established the utility of using the fluoroscopic image of the catheter adjacent to the fossa ovalis to generate a guiding shot for positioning the transseptal apparatus. In addition, distention of the fossa prior to needle perforation could be demonstrated. However, since it was often difficult to track the tip of the needle, actual puncture of the fossa was rarely demonstrated. CONCLUSIONS: Intravascular ultrasound imaging can precisely locate the fossa ovalis in virtually all subjects. It therefore may assist transseptal catheterization.

Low pressure radiofrequency balloon angioplasty: evaluation in porcine peripheral arteries.

OBJECTIVES: The purpose of this study was to evaluate the efficacy of radiofrequency-powered thermal balloon angioplasty in an in vivo porcine model. BACKGROUND: Various modes of thermal energy used adjunctively during balloon angioplasty have demonstrated the potential to enhance the results of acute lumen dilation. METHODS: In normal pigs, 75 peripheral arteries were dilated with a newly designed, radiofrequency-powered, thermal angioplasty balloon. All inflations were performed at 2-atm pressure for 85 s. Dilations were performed either with (hot) or without (cold) the application of heat. Lumen dimensions and vessel morphology were assessed with intravascular ultrasonography. At the end of each study, dilated arterial segments were harvested for histologic examination. RESULTS: Single cold balloon inflations resulted in a 12.7% increase in arterial cross-sectional area whereas single hot inflations resulted in a 22.9% increase (p < 0.03). Similarly, when multiple cold inflations were compared with multiple hot inflations, two, three and four sequential hot inflations resulted in a significantly greater increase in cross-sectional area than an equivalent number of cold inflations (p < 0.03). Histologic examination demonstrated a temperature-dependent effect on the depth of medial necrosis and extent of arterial wall thinning (p < 0.001) as well as evidence for uniform alteration of elastic tissue fibers at temperatures of > or = 60 degrees C (p < 0.03). CONCLUSIONS: Low pressure radiofrequency thermal balloon angioplasty results in a greater increase in cross-sectional area in porcine peripheral arteries than does nonheated conventional balloon angioplasty. The pathologic basis for this enhanced dilation may be a temperature-dependent effect on medial necrosis, thinning of the arterial wall or alteration of vascular elastic fibers, alone or in combination.

Intracardiac echocardiography in humans using a small-sized (6F), low frequency (12.5 MHz) ultrasound catheter. Methods, imaging planes and clinical experience.

OBJECTIVES: This study was designed to determine the clinical utility and feasibility of using 12.5-MHz ultrasound catheters for intracardiac echocardiography. BACKGROUND: Intracardiac echocardiography is a potentially useful technique of cardiac imaging and monitoring in certain settings. The feasibility of intracardiac echocardiography using 20-MHz ultrasound catheters in patients has been demonstrated. High resolution images of normal cardiac structures as well as cardiac abnormalities have been obtained. However, imaging has been limited by the shallow depth of field inherent in high frequency ultrasound imaging. METHODS: Intracardiac echocardiography with 12.5-MHz catheters was performed in eight mongrel dogs and 92 patients. Catheters were introduced percutaneously in 80 patients studied in the catheterization laboratory and directly into the heart in 12 patients in the operating room. Right heart imaging was performed in 68 patients and arterial and left heart imaging in 35 patients. RESULTS: When these catheters were introduced into the venous system, the right atrium, tricuspid valve, right ventricle, pulmonary valve and pulmonary artery were visualized. Pericardial effusion, intracardiac masses and atrial septal defects were correctly identified. The left ventricle, left atrium, mitral valve, aortic valve, aorta and coronary arteries could be imaged from the arterial circulation. Diseases identified included valvular aortic stenosis, subvalvular aortic stenosis and Kawasaki disease. Average imaging time was 10 min. No complications occurred as a result of intracardiac echocardiography. CONCLUSIONS: Intracardiac echocardiography with 12.5-MHz ultrasound catheters is safe and feasible; it also provides anatomic and physiologic information. This feasibility study provides a foundation for wider clinical use of intracardic echocardiography.