Atheroma morphology and distribution in proximal left anterior descending coronary artery: in vivo observations.

OBJECTIVES: This study sought to examine, in vivo, the shape and position of atheroma in the proximal left anterior descending coronary artery. BACKGROUND: The prevalence, shape and location of atheromas involving the proximal left anterior descending artery have implications regarding the role of disturbed shear forces in the genesis of atherosclerosis. However, no data are available regarding in vivo findings or advanced disease. METHODS: Forty-two consecutive high quality intravascular ultrasound images were examined from patients with atherosclerotic disease in the proximal left anterior descending artery just distal to the left main bifurcation. Lesion percent area stenosis and maximal, minimal and flow divider intimal-medial thickness were measured at the region immediately after the circumflex takeoff. The angle formed by the midpoint of the flow divider, the human center of gravity and the maximal plaque thickness were determined. RESULTS: Eccentricity of vessel wall atheroma was observed such that the maximal wall thickness (1.42 +/- 0.50 mm [mean +/- SD]) differed significantly from minimal wall thickness (0.17 +/- 0.098 mm). Further, the region of vessel wall manifesting maximal thickness was greater than the flow divider thickness (0.26 +/- 0.16 mm). Maximal plaque thickness spared the region of the flow divider in 100% of cases and was positioned at a mean angle of 193 +/- 49 degrees from the center of the flow divider. Eccentric morphology was maintained across the 24% to 80% range of area stenosis. CONCLUSIONS: Atheromas in the very proximal left anterior descending artery are located opposite the circumflex takeoff, spare the flow divider and maintain eccentricity across a wide range of vessel stenoses. These in vivo morphologic data support the potential role of fluid dynamic mechanical factors in atherogenesis and have implications regarding the success of catheter-based interventional procedures at the site.

Witnessed embolization of a right atrial mass during transesophageal echocardiography: implications regarding the safety of esophageal intubation.

A patient with chronic lung disease and a right atrial density that was difficult to distinguish on a transthoracic echocardiogram underwent transesophageal echocardiography (TEE) that demonstrated two mobile masses attached to the anterior right atrial wall. During the TEE procedure, the patient experienced coughing and retching due to the esophageal intubation, and the embolization of one of the right atrial masses was observed. This case is the first to document this mechanism of pulmonary embolism (a mechanism that was suspected in two prior reports), and it questions the safety of procedures that induce retching and coughing in patients with mobile right atrial masses.

Indications for limited echocardiographic imaging: a mathematical model.

BACKGROUND: Few data exist on the magnitude of potential time savings obtained by using a limited echocardiographic (echo) imaging strategy on a referral population. METHODS: A mathematical model of a limited echo screening strategy was devised that used as variables the length of the limited examination and the probability of detecting the referral diagnosis or a significant incidental finding, and assumed that any abnormality would mandate a full study. Data from prior echo population studies were used in the model as examples. RESULTS: The model demonstrated a direct relation in time savings for populations with a low prevalence of disease and incidental findings. The model predicted that a limited echo imaging strategy could result in significant time savings when applied to certain specific referral populations. CONCLUSIONS: The time savings of a limited echo screening strategy can be modeled as a function of the length of the limited screen and the presence of significant findings. This model may provide the framework in which future prospective studies can confirm indications for limited echo.

Utility of contrast echocardiography in the diagnosis of aortic dissection.

Determination of ascending aortic involvement in aortic dissection has significant implications in prognosis, immediate surgical referral, and surgical approach. We report 2 cases of the use of an echo contrast agent in enhancing the diagnostic capability of transesophageal echocardiography in suspected ascending aortic dissection. Contrast echocardiography eliminated the linear artifacts often confused with true dissection flaps and allowed easy identification of the presence of true and false lumina.

Feasibility of "limited" echo imaging: characterization of incidental findings.

To evaluate the feasibility of limiting the extent of the echocardiographic examination without omitting significant incidental findings, we reviewed consecutive reports from full echo studies performed in a tertiary medical center with the following referral questions: "rule-out pericardial effusion" (n = 40) and "rule-out source of embolus" (n = 132). Specific limited echo imaging protocols were formulated without unnecessary imaging (that is, unrelated to the diagnostic question) or use of Doppler. The percentage of full echo studies with significant incidental findings was determined, categorized by patient age, and then recalculated by whether the specific limited imaging protocol could potentially detect any or all of the incidental findings. The percentage of cases with significant incidental findings was 45% and 36% in the "rule-out" pericardial effusion and source of embolus groups, respectively. This percentage was dependent on age <65 years versus > or =65 years (22% vs 42%, p < 0.005). Limited imaging protocols could identify > or =85% of cases with significant incidental findings. These data suggest that limited echo imaging may be feasible in certain patient groups and referral diagnoses.

Characterization and surgical resection of an organized pericardial hematoma assisted by transesophageal echocardiography.

We describe the echocardiographic features of a rare pericardial hematoma causing elevated venous pressure in a patient who had suffered blunt chest trauma in the past. Transesophageal echocardiography demonstrated a large, partially calcified mass in the right cardiophrenic angle impinging on the tricuspid annulus and facilitated intraoperative assessment of surgical resection.

Intravascular ultrasound assessment and endoluminal stenting of a stenosis in a 50-month-old coronary polytetrafluoroethylene graft.

We report the assessment and management of an 81-year-old patient with a rare stenosis in a 50-month-old polytetrafluoroethylene coronary graft. We concluded that atheromatous plaque was the cause for the stenosis based on the lesion location within the graft and its characteristics by intravascular ultrasound. Differential diagnoses are discussed under consideration of the literature. The lesion was successfully treated using endoluminal stenting.

Value and limitations of intravascular ultrasound imaging in characterizing coronary atherosclerotic plaque.

Intravascular ultrasound uses a high-frequency, miniaturized, ultrasound transducer positioned on the tip of a coronary catheter to provide detailed cross-sectional images of the coronary vessel wall. Unlike angiography, which details only luminal encroachment, this imaging technique has the unique potential to provide an image of the atherosclerotic plaque, characterize its composition, and assess stenosis severity. Lipid-filled "soft" plaque, dense fibrous "hard" plaque, calcification, and thrombosis have all been identified on intravascular ultrasound images. Individual lesion types have been associated with specific clinical ischemic syndromes and with different responses to catheter-based intervention. By means of analyzing tissue composition, intravascular ultrasound may permit identification of high-risk lesions that may eventually rupture and cause unstable coronary ischemic syndromes. This article reviews the current approaches to plaque characterization by two-dimensional intravascular ultrasound imaging and addresses clinical implications, technical limitations, and future promise of the technique.

Distortion of intravascular ultrasound images because of nonuniform angular velocity of mechanical-type transducers.

The purpose of this study was to quantify nonuniform rotation in a current mechanical intravascular ultrasound (IVUS) instrument and its effect on arc, area, and diameter measurements. The accurate reconstruction of IVUS two-dimensional images is dependent on uniform rotation of the catheter tip. Prior investigations suggested that bends in the catheter driveshaft may be responsible for poor torque transmission, nonuniform rotation, and consequent errors in IVUS measurements. Eight 30 MHz mechanically driven IVUS catheters were evaluated in a model simulating the catheter course through the aorta and coronary ostium in a clinical study. Angular velocity and posi-ion profiles of the transducer, image angle, and diameter and area measurement errors were obtained from each catheter by imaging a vascular phantom with eight equispaced echogenic markers from concentric and eccentric positions. Six catheters also were tested for comparison in a simple curvature model. Rotational error was found in all catheters tested and worsened in the aortic model. Maximal angular error, defined as the largest angle between actual and presumed transducer direction, increased when measured in the aortic model as compared with the simple curvature model (17 +/- 12 degrees to 45 +/- 25 degrees; p < 0.05). Angles of 45 degrees were misrepresented with a mean range of values of 26 to 63 degrees. With eccentric catheter placement, area and diameters had average maximal absolute errors of 26% +/- 7.8% and 23% +/- 10%, respectively. In conclusion, nonuniform rotation of mechanical IVUS transducers constitutes a significant potential source of error in IVUS measurement of arcs of calcification, and lumen shape, area, and diameter.

Transesophageal echocardiography of the aorta.

Transesophageal echocardiography (TEE) has become a widely used imaging technique for evaluating cardiac structure, function, and valvular anatomy. Transesophageal echocardiography has also provided a new perspective on the thoracic aorta, and there is growing evidence that the technique contributes valuable and sometimes unique information about aortic structure and pathology. Recently introduced multiplane transesophageal probes have improved visualization of the proximal and transverse aorta, but few comprehensive discussions of TEE's application in aortic disease exist. Therefore, we have reviewed the published literature and our institutional experience in transesophageal aortic ultrasonography. The available evidence strongly supports the use of TEE in aortic dissection and atherosclerosis and suggests potential utility in additional diseases of the aorta such as aneurysm, ulceration, trauma, and congenital or inherited malformation.

Subintimal wire position during angioplasty of a chronic total coronary occlusion: detection and subsequent procedural guidance by intravascular ultrasound.

We report a case of intravascular ultrasound (IVUS) imaging of a chronic total coronary artery occlusion angioplasty initially complicated by subintimal wire penetration. IVUS provided unique images of wire position and a "double-barrel" lumen that complemented angiographic data in initial diagnosis and in subsequent guidance of the procedure.

Screening cardiac ultrasonographic examination in patients with suspected cardiac disease in the emergency department.

BACKGROUND/OBJECTIVE: Our purpose was to evaluate the utility of a brief screening cardiac ultrasonographic (SCU) examination. We prospectively compared the SCU with conventional clinical evaluation in 124 emergency department (ED) patients with suspected cardiac disease. Furthermore, we assessed the impact and quality of SCU examinations as obtained by briefly trained ED personnel (EP). METHODS: Patients underwent clinical evaluation by an ED physician and SCU examination by a sonographer or cardiologist. Patient disposition, hospital stay length, and the number of full echo examinations were compared with the presence of significant findings on SCU. In patients who received a full echocardiogram during hospitalization, results of the initial clinical examination were compared with results of the SCU examination in the diagnosis of significant findings. A similar analysis, but with quality assessment, was performed on only those SCU examinations acquired by 4 EP. RESULTS: Of the 124 patients enrolled in the main study, 40 of 124 (32%) had significant findings on SCU. Of patients with abnormal SCUs versus normal SCUs, 16 of 40 (40%) versus 18 of 84 (21%) had hospital stay lengths >2 days (P < or =.05). Using the 36 inpatient full echo studies obtained for standard indications during hospitalization as a gold standard, initial clinical examination identified only 7 of 30 (23%) significant findings and had 16 false-positive diagnoses, whereas SCU identified 22 of 30 (73%) with 8 false positives. Although similar study results occurred with interpretation of 68 SCUs obtained by EP, quality was achieved in only 55% ED personnel versus 97% of sonographer-obtained SCUs (P <.05). CONCLUSIONS: An SCU examination detects significant findings misdiagnosed on initial clinical evaluation in the ED and provides prognostic data regarding length of hospital stay.

Axial movement of the intravascular ultrasound probe during the cardiac cycle: implications for three-dimensional reconstruction and measurements of coronary dimensions.

BACKGROUND: Motion of the intravascular ultrasound (IVUS) probe within the coronary artery from cardiac contraction may result in artifacts during 3-dimensional ultrasound image reconstruction and inaccurate measurements of coronary compliance. The purpose of this study was to establish whether longitudinal movement of the IVUS transducer in the coronary artery occurs and to quantify such motion. METHODS: In 31 patients we positioned IVUS transducers at 59 coronary branch points: 41 in the left anterior descending coronary artery, 11 in the left circumflex coronary artery, and 7 in the right coronary artery. In each image sequence the branching vessel oscillated in and out of the imaging plane during the cardiac cycle, confirming longitudinal transducer movement. The extent of movement was estimated by IVUS from the dimension of the branch vessel traversed. In addition, angiographic visualization and measurement of IVUS probe motion was performed at 17 branch points in 12 patients. RESULTS: Average longitudinal transducer movement as measured by IVUS was 1.50 +/- 0.80 mm (n = 46, range 0.5 to 5.5 mm). Because IVUS could not account for probe motion that exceeded the vessel branch diameter, the values obtained represent minimum movement. Average probe motion as assessed by cineangiography in a subset of 12 patients was 2.43 +/- 1.42 mm (range 0.57 to 6.56 mm). CONCLUSIONS: This study establishes that longitudinal movement of IVUS transducers within coronary vessels occurs during the cardiac cycle. Because documented extent of motion may be sufficient to influence analysis, IVUS images are best obtained with electrocardiographic gating.

Advantage of stents in the most proximal left anterior descending coronary artery.

OBJECTIVES: Balloon angioplasty of the proximal left anterior descending artery is associated with a high rate of restenosis. We hypothesized that the significant reduction in restenosis rates demonstrated by stent implantation in the coronary arteries in general would be especially prominent in the most proximal left anterior descending coronary artery. METHODS: We reviewed 65 consecutive patients in whom stents were placed in the most proximal left anterior descending artery between March 1990 and July 1995 and compared them with 56 consecutive patients with angioplasty. Minimum luminal diameter was measured angiographically before, after, and 6 months after the intervention. We compared the change in minimum luminal diameter and restenosis rate between the patients with stents and the patients with angioplasty to clarify the response of this important artery to these different procedures. RESULTS: There was 6-month angiographic follow-up of the treated lesion in 99% of the patients. The postprocedure minimum luminal diameter, acute gain, and minimum luminal diameter at follow-up were greater in arteries treated with stents than in those treated with balloons. Of importance, late loss was not significantly different between the two groups after treatment at this site. Thus the restenosis rate after angioplasty was 52% compared with 20% after stent implantation (p < 0.001). CONCLUSIONS: Stent implantation in the most proximal left anterior descending artery is associated with an even greater reduction in restenosis rate than implantations elsewhere in the coronary arteries. This enhanced reduction in restenosis appears to be due to an unusually large amount of late loss after angioplasty at this site.