Indications for limited echocardiographic imaging: a mathematical model

Creating a Novel Cardiac Limited Ultrasound Exam Curriculum for Internal Medical Residency: Four Unanticipated Tasks

Over the past two decades, our internal medicine residency has created a unique postgraduate education in internal medicine by incorporating a formal curriculum in point-of-care cardiac ultrasound as a mandatory component. The details regarding content and implementation were critical to the initial and subsequent success of this novel program. In this paper, we discuss the evidence-based advances, considerations, and pitfalls that we have encountered in the program's development through the discussion of four unanticipated tasks unique to a point-of-care ultrasound curriculum. The formatted discussion of these tasks will hopefully assist development of ultrasound programs at other institutions.

Ultrasound as a tool for fluid status assessment in the trauma and critically ill patient

Resuscitation to euvolemia in trauma as well as in the critically ill patient, continues to be a challenge. Focused cardiac ultrasound has been shown to be a reliable tool to evaluate fluid status and to guide therapy. The present manuscript reviews the evidence supporting the use of this tool and describes the clinical applications for image-based resuscitation using echocardiogram.

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.

Hospitalist use of hand-carried ultrasound: preparing for battle

Hand-carried ultrasound (HCU) is a burgeoning technology at a critical point in its development as a general diagnostic technique. Despite the known safety and accuracy of ultrasound in radiology and echocardiography, the use of HCU to augment physical diagnosis by all physicians has yet unrealized potential. In order to incorporate ultrasound into a diagnostic model of routine bedside application, simple imaging and training protocols must first be derived and validated. Simplified cardiac ultrasound exams have already been validated to detect evidence-based targets such as subclinical atherosclerosis, heart failure, and elevated central venous pressures. However, for general examination of the acutely ill patient, it is the internist-hospitalist who should derive a full-body ultrasound examination, balancing training requirements with the numerous clinical applications potentially available. As the hospital's leading diagnostician with ultrasound expertise available in-house, the hospitalist could develop HCU so as to triage and refer more appropriately and limit unnecessary testing and hospital stays. Active involvement by hospitalists now in the planning of outcome, validation, and training studies, will be invaluable in the formation of an "ultrasound-assisted" physical examination in the future and will promote competent, cost-effective applications of HCU within general medical practice.

A Pilot Study of the Clinical Impact of Hand-Carried Cardiac Ultrasound in the Medical Clinic

BACKGROUND

Small, hand-carried ultrasound devices have become widely available, making point-of-care echocardiograms (echos) accessible to all medical personnel as a means to augment and improve the increasingly inefficient physical examination. This study was designed to determine the clinical utility of hand-carried echo by medical residents in clinical decision making.

METHODS

Nine residents underwent brief, practical echo training to perform and interpret a limited hand-carried echo as an integral component of their office examination. The residents' hand-carried echo consisting of four basic views to define left ventricular (LV) function and wall thickness, valvular disease, and any pericardial effusions was compared to one performed by a level III echocardiographer.

RESULTS

Seventy-two consecutive medical clinic patients were enrolled with an average image acquisition time of 4.45 minutes. Residents obtained diagnostic images in 94% of the cases and interpreted them correctly 93% of the time. They correctly identified 92% of the major echo findings and 78% of the minor findings. Their diagnosis of LV dysfunction, valvular disease, and LV hypertrophy improved by 19%, 39%, and 14% with hand-carried echo compared to history and physical alone. Management decisions were reinforced in 76% and changed in 40% of patients with the use of hand-carried echo.

CONCLUSION

This study demonstrates that it is possible to train medical residents to perform an effective and reasonably accurate hand-carried echo during their physical examination, which can impact clinical management.

Feasibility and potential clinical utility of goal-directed transthoracic echocardiography performed by noncardiologist intensivists using a small hand-carried device (SonoHeart) in critically ill patients

OBJECTIVE

This study was designed to assess the clinical applicability of a small, handheld, portable transthoracic echocardiography device by noncardiologist intensivists.

DESIGN

Prospective, observational study. After 10 one-hour tutorials, intensivists performed a limited transthoracic echocardiography (TTE) (2-4 views, without Doppler or M-mode) examination with the 5.6-lb SonoHeart Echo System (SonoSite, Bethell, WA) on critically ill patients admitted to the surgical intensive care unit. After initial cardiac clinical assessment in 90 patients, a limited TTE was performed by an intensivist to assess left ventricular (LV) function and LV volume status. Each study was immediately reviewed and repeated by an echocardiographer to determine the technical quality of the TTE and the accuracy of the intensivist's interpretation. Data were analyzed and presented in proportions using descriptive statistics.

SETTING

Surgical intensive care unit of an academic medical center.

PARTICIPANTS

Ninety critically ill adult patients.

INTERVENTIONS

After initial cardiac clinical assessment, a limited TTE was performed by an intensivist to assess LV size and function, to rule out significant pericardial effusions, and to estimate circulatory volume.

RESULTS

Intensivists successfully performed a diagnostic limited TTE in 94% of patients and interpreted their studies correctly in 84%. Limited TTE provided new cardiac information and changed management in 37% of patients. TTE added useful information in an additional 47% of patients but did not alter immediate management. The mean "goal-directed TTE" acquisition time was 10.5 +/- 4.2 minutes.

CONCLUSION

After a brief formal training in using this handheld echocardiographic system in intensive care unit patients, surgical intensivists successfully performed and correctly interpreted a limited TTE in critically ill patients. Limited TTE provided new information and altered management in a significant number of patients. This study supports incorporating bedside goal-directed, limited TTE into intensivists' training programs.

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.

Diagnostic accuracy of new handheld echocardiography with doppler and harmonic imaging properties

BACKGROUND

The first generation of handheld echocardiography devices was evaluated with divergent results because of inherent technical limitations. New handheld devices with continuous/pulsed wave Doppler and tissue harmonic imaging were introduced recently. In this study, comparisons were drawn among standard echocardiography, invasively measured systolic pulmonary artery pressure, and these new devices.

OBJECTIVE

We sought to evaluate new handheld echocardiography and its diagnostic accuracy compared with standard echocardiography.

METHODS

Two consecutive echocardiographic examinations were performed by experienced and independent examiners using handheld and standard echocardiography. Systolic pulmonary artery pressure was measured by Swan-Ganz catheter.

RESULTS

In all, 177 (56.2%) patients had normal cardiac function; 138 (43.8%) had underlying cardiac pathology. Handheld echocardiography had an overall agreement of 94.8% and kappa of 0.89 to detect the main echocardiographic finding. Handheld echocardiography detected valve disease with an agreement of 96.7% and kappa of 0.93; global left ventricular function was assessed correctly in 85.6% of cases. Pericardial effusion was diagnosed with an agreement of 91.2%. Dyssynergy was found by handheld echocardiography with an agreement of 95.4% and kappa value of 0.88. Systolic pulmonary artery pressure measured by handheld echocardiography and Swan-Ganz catheter had a correlation of 0.97.

CONCLUSION

This study demonstrates the high diagnostic accuracy of handheld devices with continuous/pulsed wave Doppler and harmonic imaging, and that these devices broaden the diagnostic spectrum while allowing for enhanced mobility in everyday clinical applications.

Time requirements of the standard echocardiogram: implications regarding limited studies

BACKGROUND

Although no formal detailed definitions exist, a standard echocardiogram should easily be differentiated from a limited examination by its comprehensive nature and time requirement.

OBJECTIVE

We evaluated the time required to perform each specific component of a comprehensive echocardiography examination and applied these data to compare the time required to complete 3 limited imaging protocols.

METHODS

In all, 7 experienced sonographers were timed in their performance of a comprehensive echocardiographic examination on a healthy patient. A total of 3 limited imaging protocols were then constructed to evaluate for pericardial effusion, wall motion, and left ventricle size. The time necessary to complete each protocol was calculated by adding the average time required to perform all of its components and was compared with the comprehensive examination.

RESULTS

The imaging time required to complete a standard study was 26 +/- 5.4 minutes (range: 20-32). The percentage of total study time spent on 2-dimensional imaging, M-mode, color Doppler, and spectral components was 31 +/- 2.9%, 11 +/- 3.6%, 17 +/- 2.9%, and 39 +/- 5.0%, respectively. The calculated time needed to perform a limited protocol was less than 5 minutes, resulting in a greater than 80% reduction in time compared with the standard examination.

CONCLUSION

Time analysis of components of the standard echocardiography examination can be used to construct appropriate, time-efficient, limited, cardiac ultrasound imaging examinations and differentiate limited from comprehensive studies.

Valvular flow abnormalities are often identified by a resting focused Doppler examination performed at the time of stress echocardiography

BACKGROUND

Patients are usually referred for stress echocardiography to assess whether there is inducible myocardial ischemia. At some centers, a focused Doppler examination is also performed. We sought to determine the clinical value of this additional study by examining how often valvular flow abnormalities were identified that might affect clinical care.

METHODS

We reviewed 1272 consecutive stress echocardiogram reports from a 1-year period, including 1223 tests that contained focused Doppler data. Important Doppler findings were defined as at least moderate mitral regurgitation, at least mild aortic regurgitation, any aortic or mitral valve stenosis, or any resting left ventricular outflow tract gradient.

RESULTS

Overall, focused Doppler identified an important Doppler abnormality in 214 patients (17%). At least moderate mitral regurgitation was identified in 67 patients (5%) and at least mild aortic regurgitation was identified in 163 patients (13%). In addition, aortic stenosis (n = 14; 1%), mitral stenosis (n = 5; 0.4%), and resting outflow tract gradient (n = 2; 0.2%) were noted. A prior echocardiogram had been performed at our institution in 317 patients (26%). For this subset, a new important Doppler finding, a two-step change in regurgitant grade, or a one-step change in stenosis severity was noted in 28 patients (9%). Among patients who had a previous study, the prevalence of new findings was the same (9%) in those who had been studied within the previous year as in those whose previous study had been performed more than 2 years before.

CONCLUSION

Focused Doppler documents valvular flow abnormalities in 17% of patients referred for stress echocardiography, thereby enhancing the potential overall value of the test. The frequency of new findings was independent of the time interval from the previous Doppler study. These data should be considered when clinicians choose a stress imaging modality.

Limited cardiac ultrasound examination for cost-effective echocardiographic referral

BACKGROUND

Although a standard echocardiogram is frequently requested and requires significant resources, few data exist on methods to improve referral for this examination. Therefore, we sought to determine the diagnostic value of a limited echocardiographic examination and to predict the cost-effectiveness of a limited imaging strategy on echocardiographic referral.

METHODS

A limited echocardiographic examination was reviewed for abnormalities and compared with standard echocardiographic findings. Assuming an imaging strategy in which a normal limited echocardiographic examination would negate the need for standard echocardiography, we calculated the diagnostic yields, the number of full echocardiographic studies eliminated, and the number of abnormal cases missed. We also stratified data by patient age (< or > or = 65 years), inpatient versus outpatient status, gender, referral diagnosis, and referring physician subspecialty.

RESULTS

In 151 outpatients, overall diagnostic yield was 47% (95% CI [39%, 55%]), and was lower in those younger than 65 years, in women, and in noncardiologist referral. In 155 inpatients, yields were 75% (95% CI [67%, 83%]) and were also related to age, but not to gender, diagnosis, and physician subspecialty. Sensitivity, specificity, negative and positive predictive values, and accuracy for the limited echocardiographic examination was 77%, 72%, 67%, 81%, and 75%, respectively. The limited imaging strategy negated 70% of studies in the outpatient group younger than 65 years, with a less than 5% chance of missing a clinically significant finding.

CONCLUSION

A limited echocardiographic imaging strategy is most cost-effective when used in young outpatients, where it can result in a substantial reduction in referral for standard echocardiography while rarely missing findings.

Experience with an ultrasound stethoscope

BACKGROUND

To test the diagnostic potential of the SonoHeart, a battery-powered hand-held ultrasound imaging device, in an outpatient clinic setting.

METHODS

A total of 114 patients with a variety of cardiac diseases were examined by 2 independent cardiologists with the hand-held device using the standard echocardiographic system (SE) as a reference. Global right ventricular (RV) and left ventricular (LV) function (scored as normal, mildly to moderately, or severely reduced) and internal cavity dimensions were assessed. Regional wall motion of 6 segments using a 2-point score (1 = normal wall motion, 2 = abnormal wall motion) was evaluated in 34 patients on-line.

RESULTS

There was a good agreement between the 2 imaging devices for evaluation of global LV (93%) and RV function (99%), regional wall motion (90%), dimensions of the LV (99%) and the RV (99%), and the left (96%) and right atria (99%). Furthermore, SonoHeart identified hypertrophic cardiomyopathy, pericardial effusion, and abnormalities of valves.

CONCLUSION

The SonoHeart device allows rapid and accurate diagnosis, whenever needed in the outpatient clinic.