Jonas A. Metz

INTRAVASCULAR ULTRASOUND:: Basic Interpretation

IVUS provides a new gold standard for visualization and measurement of coronary artery disease. Morphologic and morphometric observations by IVUS are in general considerably more detailed and accurate than those obtained by angiography. IVUS has led to new insights into the pathophysiology of coronary plaque accumulation with respect to adaptive vessel responses (remodeling) and their exhaustion (de-remodeling, shrinkage). Further technologic refinements need to focus on issues such as improvement in resolution and miniaturization of IVUS catheters to enhance the applicability of this imaging technique.

The progression of thrombus in an ex-vivo shunt model evaluated by intravascular ultrasound radiofrequency analysis.

We tested the ability of ultrasound radiofrequency (RF) signal analysis to characterize thrombus accumulation in a Dacron graft incorporated into the exteriorized arteriovenous shunt in 3 baboons with constant blood flow for 60 min. Thrombus formation was quantified by sequential measurements of 111Indium-labeled platelet deposition. RF signals were acquired every 15 min at 2 sites in the graft, using a 2.9 Fr intravascular ultrasound catheter-based transducer (30 MHz) and digitized at 250 MHz in 8-bit resolution. Regions of interest were placed within a 0.5-mm perimeter adjacent to the graft wall. Integrated backscatter increased significantly (p < 0.001) with increasing platelet deposition. However, mean-to-standard deviation ratio of the RF envelope showed no significant change and the distribution pattern of the RF probability function remained constant and consistent with a Rayleigh scattering process. These results provide a basis for using RF analysis to monitor the time-course of thrombus formation.

Impact of Curve Distortion Errors on Intravascular Ultrasound Measurements and Three-Dimensional Reconstructions

Intravascular ultrasound distortion errors and longitudinal reconstructions are primarily determined by the angle of curvature. The error in commonly encountered angles is relatively small.

Enhancement of spatial orientation of intravascular ultrasound images with side holes in guiding catheters

BACKGROUND Intravascular ultrasound (IVUS) images are typically viewed and recorded in an arbitrary rotational orientation. This study was performed to validate a new method for improved orientation of sonographic vascular cross-sections. METHODS AND RESULTS We have tested a simple technique for rotational indexing of IVUS in cases in which guiding catheters with side holes are used. Although guiding catheters are opaque to ultrasonography, the side holes transmit the beam and therefore can be easily identified. The orientation of the side holes, which is characteristic for each make of guiding catheter, can be used to determine the anatomically appropriate rotational orientation of the IVUS image. In this study images of four commercially available side-hole guiding catheters were viewed in vitro to confirm the visibility of the side holes and to characterize their orientation for purposes of rotational orientation of images. Feasibility tests of rotational orientation based on side holes were then performed in canine coronary arteries (n = 3) and in six human coronary arteries. Three serial imaging runs in each clinical case yielded a mean variability in rotational orientation of 7.5 +/- 1.5 degrees. CONCLUSION Validation testing of the side-hole technique demonstrates the potential for consistent and anatomically appropriate orientation of intravascular ultrasound images.

The changing role of high speed rotational atherectomy in the present and future practice of coronary intervention

Eight hundred and fifty-two high speed rotational atherectomy (HSRA) procedures were performed in a single consecutive series of 769 patients. Stand alone HSRA was performed in 261 patients (29%). HSRA with adjunctive low pressure (≤2 ATM) balloon angioplasty (LP BA) was performed in 261 patients (34%), and HSRA with adjunctive high pressure (≥4 ATM) balloon angioplasty (HP BA) was performed in 216 patients (28%). Prognostically unfavorable Type B2 and C lesions dominated the study group (73.8%). Procedural success rate was 96%. Emergency coronary artery bypass surgery was performed in 1.3% of cases, Q-wave myocardial infarction occurred in 3.0% and death, related to procedure, was consequent in 0.4% of cases. Incidence of flow limiting dissections was 3.1%, distal spasm 5.2%, and “no reflow” phenomenon, 1.7%. The recent technique modifications included continuous advancer/guiding catheter infusion of the nitroglycerin — verapamil mixture, limitation of duration of lesion engagement by the burr, decrease of rotational speed, and strict control of rpm drop during lesion ablation. Evolution of the interventional technique involved trends towards decrease of the use of HP BA in conjunction with steady increase in the percentage of SA and LP BA procedures over time. During the last year a combination of HSRA and stents emerged. The “rotastenting” produces excellent results in longer and more frequently calcified lesions than the use of stents alone with higher degree of attainable stent expansion. These technique changes resulted in complete absence of “no reflow” in last two years, as well as a decrease in coronary vascular reactivity from all burr passes.