Bruce J. Kimura

Focused Cardiac Ultrasound: Recommendations from the American Society of Echocardiography

1. Why is a guideline needed? 567 2. Definitions 568 a. What is FCU? 568 b. Terminology 568 3. Differentiation of FCU and ‘‘Limited TTE’’ 568 a. Examination Expectations 569 b. Equipment 570 c. Image Acquisition 570 d. Image Interpretation 570 e. Billing 571 4. Considerations for Successful Use of FCU as an Adjunct to Physical Examination 571 a. Personnel 571 b. Equipment 571 c. Potential Limitations of FCU 572 5. FCU Scope of Practice 573 a. FCU When Echocardiography is Not Promptly Available 573 b. FCU When Echocardiography is Not Practical 574

International Evidence-Based Recommendations for Focused Cardiac Ultrasound

BACKGROUND Focused cardiac ultrasound (FoCUS) is a simplified, clinician-performed application of echocardiography that is rapidly expanding in use, especially in emergency and critical care medicine. Performed by appropriately trained clinicians, typically not cardiologists, FoCUS ascertains the essential information needed in critical scenarios for time-sensitive clinical decision making. A need exists for quality evidence-based review and clinical recommendations on its use. METHODS The World Interactive Network Focused on Critical UltraSound conducted an international, multispecialty, evidence-based, methodologically rigorous consensus process on FoCUS. Thirty-three experts from 16 countries were involved. A systematic multiple-database, double-track literature search (January 1980 to September 2013) was performed. The Grading of Recommendation, Assessment, Development and Evaluation method was used to determine the quality of available evidence and subsequent development of the recommendations. Evidence-based panel judgment and consensus was collected and analyzed by means of the RAND appropriateness method. RESULTS During four conferences (in New Delhi, Milan, Boston, and Barcelona), 108 statements were elaborated and discussed. Face-to-face debates were held in two rounds using the modified Delphi technique. Disagreement occurred for 10 statements. Weak or conditional recommendations were made for two statements and strong or very strong recommendations for 96. These recommendations delineate the nature, applications, technique, potential benefits, clinical integration, education, and certification principles for FoCUS, both for adults and pediatric patients. CONCLUSIONS This document presents the results of the first International Conference on FoCUS. For the first time, evidence-based clinical recommendations comprehensively address this branch of point-of-care ultrasound, providing a framework for FoCUS to standardize its application in different clinical settings around the world.

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.

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.

Observations during development of an internal medicine residency training program in cardiovascular limited ultrasound examination.

BACKGROUND Despite the future potential of using ultrasound stethoscopes to augment the bedside cardiac physical, few data exist on a general cardiovascular imaging protocol that can be taught to physicians on a perpetual basis as a curriculum in graduate medical education. METHODS During the past decade, we developed and integrated a cardiovascular limited ultrasound training program within the confines of an internal medicine residency. The evidence-based rationale for the exam, the teaching methods, and curriculum are delineated, and subsequent observations regarding program requirements, proficiency, and academic outcomes are explored. Analysis of variance and linear regression assessed for relationships between academic scores, chief resident selection, and gender to proficiency in ultrasound. RESULTS A brief, 5-minute cardiovascular limited ultrasound exam (CLUE) was taught using both didactic and bedside methods, and practiced primarily within the cardiology consult, outpatient clinic, and intensive care rotations. Program costs were minimized by employing readily available institutional resources. After a 2-year lead-in training phase, the subsequent 4 years of senior resident performance (n = 41 residents) showed an 81% pass rate in CLUE competency. Resident ultrasound performance did not relate to academic scores (r = 0.05, P = 0.75), chief resident selection, nor gender. Observations regarding resident pitfalls in CLUE practice and increased participation in extracurricular research are described. CONCLUSIONS We report our initial experience in developing and implementing a training program for bedside cardiovascular ultrasound examination that employed evidence-based techniques, set proficiency goals, and assessed resident performance. It may be feasible to teach future internist-hospitalists the technique of bedside ultrasound during residency.

Diagnostic performance of a pocket-sized ultrasound device for quick-look cardiac imaging

BACKGROUND Although pocket-sized, simplified ultrasound devices have emerged to enable subjective point-of-care assessment, few data on their cardiac application exist. We sought to examine the image quality and the accuracy of subjective diagnosis of video loops obtained from a pocket-sized ultrasound device for 2 significant cardiac abnormalities, left ventricular systolic dysfunction and left atrial enlargement, obtained from a single, quick-look view. METHODS Parasternal left ventricular long-axis images acquired with a miniaturized commercially available device (Acuson P10) were reviewed using subjective criteria for left ventricular systolic dysfunction and left atrial enlargement and were compared with M-mode measurements of left atrial systolic diameter and E-point septal separation from a fully featured echocardiograph in 78 inpatients referred for standard echocardiography. Interpretive confidence and image quality were evaluated with each interpretation. RESULTS Of 78 inpatient studies, 19% of pocket ultrasound and 13% of standard studies were technically limited (P = NS). Of 61 technically adequate studies, subjective interpretation of pocket ultrasound images had a sensitivity, specificity, and accuracy of 79%, 52%, and 64% for left atrial diameter more than 4 cm; 47%, 98%, and 82% for E-point septal separation more than 1 cm of; 83%, 62%, and 74% for either abnormality; and 92%, 82%, and 87% for either abnormality when interpretive confidence was present (n = 23). The pocket ultrasound image quality scores were significantly lower than the standard echocardiograph (P < .001). CONCLUSION The pocket-sized device provided adequate imaging for screening of 2 significant cardiac entities. Subjective interpretation of a single parasternal view may help identify patients with cardiac disease.

Technology insight: hand-carried ultrasound cardiac assessment--evolution, not revolution.

Hand-carried ultrasound devices can enhance the art of bedside physical examination by increasing diagnostic accuracy, detecting disease at an earlier stage, and improving triage and referral of patients. Although limitations of device cost and portability can be overcome with technologic advances, the shortage of standardized imaging and training opportunities now needs to be addressed to move the technique forward. Cardiologists are the best-qualified subspecialists to design and teach a simplified training program for bedside use of hand-carried ultrasound devices to assess the cardiovascular system.

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.

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.

Detection of early carotid arterial atherosclerosis by briefly trained physicians using a hand-held ultrasound device.

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