Low-frequency intracardiac ultrasonographic imaging before and after balloon pulmonary valvuloplasty

Percutaneous Therapies in the Treatment of Valvular Pulmonary Stenosis

Transcatheter balloon pulmonary valvuloplasty (BPV) is the standard of care in managing symptomatic patients with moderate-to-severe pulmonary valvular stenosis, or asymptomatic patients with severe pulmonary valvular stenosis or with moderate pulmonary stenosis and evidence of objective exercise intolerance or right ventricular dysfunction. This article discusses the incidence, causes, and pathophysiology of valvular pulmonary stenosis in adolescents and adults; its natural history and noninvasive evaluation; the current guideline-recommended indications for BPV; the technical aspects of performing BPV; the immediate and long-term outcomes after valvuloplasty; and the complications and safety of the procedure. Also discussed is the role of this procedure in neonatal critical pulmonary stenosis and in percutaneous pulmonary valve replacement for patients with prior pulmonic valve interventions or degenerated right ventricular pulmonary artery conduits.

Quantitative assessment of stenotic aortic valve area by using intracardiac echocardiography: in vitro validation and initial in vivo illustration

Quantitative assessment of aortic stenosis (AS) is subject to the limitations of all current noninvasive and invasive methods. The ability to obtain a direct measure of aortic valve area with high resolution by intracardiac echocardiography (ICE) could be of great benefit to catheterized patients. To provide a fixed AS area as an ideal standard for comparison, we performed ICE in 12 sheep hearts with experimentally created AS and five human AS hearts from autopsies. ICE catheters were passed retrograde across the aortic valve, and the minimal orifice area on pullback was planimetered and compared with calibrated video imaging. The entire orifice circumference could be successfully recorded in 16 (94%) hearts. Orifice area from ICE correlated well with actual values (r=0.98; standard error of the estimate [SEE] = 0.06 cm2). To illustrate the applicability in vivo, two canine models and 10 patients with AS were studied. The limiting orifice could be imaged in both animals and in 8 of 10 patients, in whom values agreed well with invasive data (r= 0.95; SEE = 0.04 cm2). ICE can therefore accurately measure AS orifice area in vitro; it can be applied in vivo as well. These validation studies laid the foundation for subsequent clinical studies and applications.

Intracardiac echocardiography with a steerable low-frequency linear-array probe for left-sided heart imaging from the right side: experimental studies

Despite a need for intracardiac echocardiographic guidance during interventional procedures, an optimal catheter device is not available. The depth of field of catheters bearing 10 to 20 MHz transducers does not allow easy or complete visualization of the left side of the heart from the right side of the heart. Lower frequency transducers would be required to increase the depth of view of such rotational devices. These low-frequency transducers would require an expanded aperture and thus a larger catheter size. Other transducer modalities that could exploit the length of the imaging device rather than the circumference could potentially solve the problem of aperture size. To examine whether a linear-array transducer could provide adequate images of the left side of the heart from the venous side, we employed a prototype 7 MHz linear-array probe with a steerable tip inside eight animal hearts. Atrial and ventricular septal defects were created experimentally. The device was introduced into the right side of the heart through the inferior and superior vena cavae. Intracardiac imaging with this probe allowed visualization of the left side of the heart and major arteries from the right side with excellent image quality. By advancing the probe in various locations in the right side of the heart and using the steerability of this device, we were able to identify useful imaging planes for different cardiac structures. Atrial and ventricular septal defects were also detected easily and delineated clearly. The concept of a low-frequency (< 8 mHz) linear-array probe for intracardiac echocardiography may represent another step toward "whole-heart imaging" from the venous side.(ABSTRACT TRUNCATED AT 250 WORDS)

Intracardiac echocardiography without fluoroscopy: potential of a balloon-tipped, flow-directed ultrasound catheter

Intracardiac echocardiography is a technique that uses catheter-based ultrasound transducers placed within the heart to image cardiac structures. One disadvantage to this technique is that it requires fluoroscopy for catheter placement. This study was performed to evaluate a prototype balloon-tipped, flow-directed catheter for use during intracardiac echocardiography in seven dogs. With the balloon deflated, the catheter could not be successfully advanced without fluoroscopy. Even with fluoroscopic imaging, catheter advancement was often difficult. With the balloon inflated, it could easily be passed into the pulmonary artery without fluoroscopy in 12 of 14 attempts. Images of the cardiac chambers, valves, and pulmonary artery could be obtained. In conclusion, use of a balloon-tipped, flow-directed catheter for intracardiac echocardiography and pulmonary artery imaging can be performed without the use of fluoroscopy. With continued refinements, such as enhancement of the visual field, intracardiac echocardiography could possibly be performed at the bedside to assess cardiac function or assist with interventional procedures.