Initial experience with a novel real-time three-dimensional intracardiac ultrasound system to guide percutaneous cardiac structural interventions: a phase 1 feasibility study of volume intracardiac echocardiography in the assessment of patients with structural heart disease undergoing percutaneous transcatheter therapy.

BACKGROUND: Intracardiac echocardiographic (ICE) imaging is a modality increasingly used to guide percutaneous cardiac structural interventions. Until recently, ICE imaging has been limited by the presence of only two-dimensional imaging planes and requires considerable catheter manipulation to visualize certain targets. The aim of this study was to assess the feasibility of a new three-dimensional (3D) volumetric ICE system to provide imaging guidance in 15 patients undergoing percutaneous cardiac structural interventions. METHODS: The Siemens AcuNav 3D volumetric ICE catheter was used to guide interventions in 15 patients. Imaging was performed at 6 and 8 MHz without color Doppler flow mapping and at 4 and 6 MHz with color Doppler flow mapping. The images were independently reviewed, and the ability to visualize specific structures was assessed by two independent and expert ICE imagers. RESULTS: The majority of patients (n = 11 [73%]) were undergoing percutaneous transcatheter closure of patent foramen ovales (n = 3 [20%]) or atrial septal defects (n = 8 [53%]). Three patients (20%) underwent balloon valvuloplasty for mitral stenosis. One patient (7%) underwent a diagnostic study for congenital heart disease. There were no significant differences in image scores between 3D and two-dimensional imaging without color Doppler in clinically important targets. With color Doppler, there were decreased image scores in the 3D images. Three-dimensional images provided improved imaging of devices and catheters and of the relationship between atrial septal defect devices and the aorta. CONCLUSION: Three-dimensional volumetric ICE imaging can be successfully used to guide structural heart disease procedures. It has the potential to provide greater anatomic information during interventions. Further improvement in its imaging capabilities is required to improve color Doppler mapping and volume size capabilities.

Estimation of oxygen consumption in elderly patients with aortic stenosis.

BACKGROUND: Invasive evaluation of aortic stenosis requires measuring cardiac output. With the Fick equation, a measure of oxygen consumption (VO2) is required. Standard equations for estimating VO2 were derived in younger and healthier populations than the ones referred for possible transcatheter aortic valve replacement. The goal of this study was to determine the best method of estimating VO2 in elderly patients with aortic stenosis. METHODS: We directly measured VO2 in elderly patients undergoing invasive assessment of aortic stenosis. We compared standard equations estimating VO2 and two prespecified hypothesized equations for VO2 to determine which was most accurate. We also examined the subgroup of patients with low flow. RESULTS: Among 51 patients, aged 80-97 years, the mean VO2 was 198 mL/min. Using 125*body surface area (BSA) to estimate VO2 the average error was 35 mL/min, and 67% of values were within 25% of the true value. Using 3*Weight to estimate VO2, those numbers were 29 mL/min and 65%. The hypothesized equations did better: 100*BSA had error of -12 mL/min and 90% within 25% of measured VO2; for 2.5*Weight it was -9 mL/min and 84%. Among the 20 patients with low flow, hypothesized equations performed best. Using 2.5*Weight and 100*BSA there were 90% and 85% within 25% of measured VO2, respectively, compared to 55% and 75% when 3*Weight and 125*BSA were used. Weight and BSA were the only independent predictors of VO2. CONCLUSIONS: When estimating VO2 in an elderly population with aortic stenosis, the best equations are 2.5*Weight and 100*BSA.