Author + information
- Received January 2, 2014
- Revision received April 28, 2014
- Accepted May 6, 2014
- Published online October 1, 2014.
- Manish Mehta, MD∗,
- Timothy Jacobson, MD∗,
- Dawn Peters, PhD†,
- Elizabeth Le, MD‡,
- Scott Chadderdon, MD∗,
- Allison J. Allen, MD§,
- Aaron B. Caughey, MD§ and
- Sanjiv Kaul, MD∗∗ ()
- ∗Knight Cardiovascular Institute, Oregon Health & Science University, Portland, Oregon
- †Division of Biostatistics, Department of Biostatistics, Public Health and Preventive Medicine, Oregon Health & Science University, Portland, Oregon
- ‡Portland Veterans Administration Medical Center, Oregon Health & Science University, Portland, Oregon
- §Department of Obstetrics and Gynecology, Oregon Health & Science University, Portland, Oregon
- ↵∗Reprint requests and correspondence:
Dr. Sanjiv Kaul, Knight Cardiovascular Institute, Oregon Health & Science University, UHN 62, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239.
Objectives The purpose of this study was to test the hypothesis that handheld ultrasound (HHU) provides a more accurate diagnosis than physical examination in patients with suspected cardiovascular abnormalities and that its use thus reduces additional testing and overall costs.
Background Despite the limitations of physical examination and the demonstrated superiority of HHU for detecting cardiac abnormalities, it is not routinely used for the bedside diagnosis of cardiac conditions.
Methods Patients referred for a standard echocardiogram for common indications (cardiac function, murmur, stroke, arrhythmias, and miscellaneous) underwent physical examination and HHU by different cardiologists, who filled out a form that also included suggestions for additional testing, if necessary, based on their findings.
Results Of 250 patients, 142 had an abnormal finding on standard echocardiogram. Of these, HHU correctly identified 117 patients (82%), and physical examination correctly identified 67 (47%, p < 0.0001). HHU was superior to physical examination (p < 0.0001) for both normal and abnormal cardiac function. It was also superior to physical examination in correctly identifying the presence of substantial valve disease (71% vs. 31%, p = 0.0003) and in identifying miscellaneous findings (47% vs. 3%, p < 0.0001). Of 108 patients without any abnormalities on standard echocardiography, further testing was suggested for 89 (82%) undergoing physical examination versus only 60 (56%) undergoing HHU (p < 0.0001). Cost modeling showed that HHU had an average cost of $644.43 versus an average cost of $707.44 for physical examination. This yielded a savings of $63.01 per patient when HHU was used versus physical examination.
Conclusions When used by cardiologists, HHU provides a more accurate diagnosis than physical examination for the majority of common cardiovascular abnormalities. The finding of no significant abnormality on HHU is also likely to result in less downstream testing and thus potentially reduce the overall cost for patients being evaluated for a cardiovascular diagnosis.
Physical examination has been the mainstay for the point-of-care diagnosis of cardiovascular disease for centuries. Despite reports on the limitations of physical examination using the stethoscope (1,2) and the surge of imaging devices that can visualize the heart in real-time and augment the physical examination (3–6), the stethoscope has not been replaced, in whole or in part, as the principal means of the bedside diagnosis of cardiac conditions.
An adverse consequence of the inaccuracy of physical examination is missing a diagnosis such as critical aortic stenosis or significant mitral regurgitation in a patient with severe left ventricular (LV) dysfunction. Another adverse consequence is the lack of confidence regarding the clinical significance of a physical finding (e.g., a murmur), which frequently leads to ordering a test that is often unnecessary. Finally, there are cardiac abnormalities that cannot be assessed by physical examination, such as moderate LV dysfunction, LV thrombus, and vegetation. For all these reasons, a direct visual assessment of cardiac structures and function at the point of care makes eminent sense.
We hypothesized that use of a handheld ultrasound (HHU) device that could be easily deployed at the point of care would provide a more accurate diagnosis than physical examination in patients suspected of having cardiovascular abnormalities. We also reasoned that finding no abnormality on HHU would reduce the chances of ordering an unnecessary test and thus potentially reduce overall cost in patients being evaluated for a cardiovascular diagnosis.
This was a prospective study designed to compare HHU with physical examination in patients admitted to the hospital and referred for echocardiography. The reference standard was a routine 2-dimensional Doppler echocardiogram. The indications were broadly grouped under the 5 most common categories seen in an echocardiography laboratory: 1) LV function in patients with chest pain, dyspnea, and the like; 2) valve disease in patients with murmurs or known valve disease; 3) a cardiac source of embolism in patients with stroke; 4) structural heart disease in patients with arrhythmias; 5) and miscellaneous (congenital abnormalities, hypertrophic cardiomyopathy, diseases of ascending aorta, pericardial effusion, etc.). Because some patients were referred for more than 1 indication, each patient was assigned a primary and, if needed, a secondary indication.
The study was approved by the Institutional Human Investigation Committee at the Oregon Health & Science University. All patients gave written informed consent. Pregnant subjects and those <18 years of age were excluded.
A cardiology fellow (M.M. or T.J.) was assigned to the echocardiography laboratory to identify patients referred for 1 or more of the above 5 categories. The number of patients selected for each indication was roughly proportional to the frequency with which they were referred to the echocardiography laboratory. The fellow then identified a cardiology attending physician who examined the patient without access to the echocardiogram results. The patient was also examined the same day by another cardiologist using HHU, who also was blinded to the standard echocardiogram findings. Each attending physician was only told of the indication for which the standard echocardiogram had been ordered and was not allowed to obtain a patient history. They then completed a pre-designed form (Table 1). In addition, they indicated that based on their examination, the patient either needed no further testing or needed to undergo 1 of the tests listed in Table 1 to further clarify the diagnosis.
HHU was performed using a pocket-sized, battery-operated device (Vscan, GE Healthcare, Milwaukee, Wisconsin) weighing 39 g with a length of 13.5 cm, a width of 7.3 cm, and a thickness of 2.8 cm, attached to a broad-bandwidth ultrasound probe (1.7 to 3.8 MHz). It provides B-mode and color Doppler images but no spectral Doppler data. Its retail price is $7,900.
LV and right ventricular (RV) function and pulmonary artery pressure were classified by both physical examination and HHU as either normal or abnormal. Valve disease was classified as none, mild, moderate, or severe. LV hypertrophy; LV, RV, and aortic dilation; hypertrophic cardiomyopathy; ventricular or atrial septal defect; and pericardial effusion were classified as being present or absent on both physical examination and HHU. For stroke patients, although hand-agitated saline was administered as per protocol for the standard echocardiogram to rule out a patent foramen ovale, it was not performed as a part of the HHU examination. Consequently, for purposes of this study, the cardiac sources of stroke included only LV thrombus or endocarditis.
There were 17 cardiologists who performed the physical examination. They were classified according to level of clinical experience based on the number of years they had practiced as an attending physician (<5, 5 to 10, or >10 years). There were 4 cardiologists who performed HHU examinations. They all had some experience in echocardiography, varying from <2 years to >20 years.
The data were analyzed in 2 steps. The first was a comparison of HHU and physical examination for any abnormal finding that was noted on the standard echocardiogram, which was interpreted by trained cardiologists assigned to the echocardiography laboratory. Mild abnormalities were not considered different from normal. Abnormalities (especially in terms of valve findings) had to be substantially different (e.g., none versus moderate, or mild versus severe) to be considered disparate between the 2 methods. The second analysis was the comparison between HHU and physical examination for the primary and secondary indication for the standard echocardiogram. The charges assigned for downstream testing were obtained from the hospital billing department.
A McNemar test, using the binomial distribution to calculate exact p values, was used to compare the correct diagnosis between HHU and physical examination for each distinct disease category, with the standard echocardiogram serving as the reference. The inability to assess a condition by either method was considered an incorrect diagnosis for purposes of analysis.
For each condition, we also used logistic regression analysis that controlled for patient age and sex to determine whether obtaining a correct diagnosis by either physical examination or HHU was related to the level of experience of the cardiologist. Sample sizes needed for detection of differences in false positive or false negative fractions between HHU and physical examination with 90% power at significance level of 0.05 were determined on the basis of assumed discordance for each diagnosis.
A cost-analysis model was created (Figure 1) with TreeAgePro 2012 (TreeAge Software Inc., Williamstown, Massachusetts). We assumed that patients undergoing either physical examination or HHU would then be recommended to undergo no testing or 1 of the tests listed in Table 1. The Current Procedural Terminology (CPT) codes for these tests are listed in Table 2. The probability of needing additional testing was derived from the data collected in the current study (Table 1). For HHU and physical examination, we used duration of the examination to derive a cost based on average physician pay. Because this was an inpatient study, we did not incorporate time costs of the patient. In the arm that used HHU, we also added the average cost per use of the HHU unit, with total costs amortized over a 5-year expected use (1,000 studies). The costs of each test were based on the facility and professional charges at Oregon Health & Science University (Table 2), and true costs were then calculated with a cost/charge ratio of 0.434, which was derived from Medicare data.
We recruited 250 patients (164 men and 86 women) ranging in age from 19 to 101 years (mean age 61 ± 15 years). The mean body mass index (BMI) was 29.9 ± 6.6 kg/m2. A BMI >30 kg/m2 was noted in 109 patients (44%). One hundred seven patients had at least 1 finding in Table 1 not assessable by physical examination. The mean BMI of these patients was not different from the 143 patients in whom all findings were assessable on physical examination (29.8 vs. 30.0 kg/m2, p = 0.85). Similarly, the BMI of the 29 patients in whom at least 1 finding in Table 1 was not assessable by HHU was no different from the 221 in whom all findings were assessable (31.7 vs. 29.7 kg/m2, p = 0.16). The time taken for physical examination was 5 ± 3 min, whereas that for HHU was 8 ± 3 min.
Findings based on entire examination
Of the 250 patients, 142 had an abnormal finding on standard echocardiography. Of these, HHU correctly identified 117 patients (82%), and physical examination correctly identified 67 (47%, p < 0.0001) with at least 1 abnormality seen on the standard echocardiogram. Table 3 compares the results of HHU and physical examination based on the findings of each regardless of the clinical indication. HHU was vastly superior to physical examination for both normal and abnormal LV and RV function. Both approaches were equivalent in determining the absence or presence of pulmonary hypertension, with neither approach performing particularly well in detecting the presence of pulmonary hypertension. Of note, unlike the standard echocardiogram, the HHU equipment does not have spectral Doppler, and hence, the tricuspid jet velocity used to calculate the pulmonary artery pressure cannot be measured.
Although both methods could reliably exclude substantial valve disease (moderate or severe stenosis or regurgitation), HHU was far superior in terms of correctly identifying the presence of such disease. HHU was also marginally superior to physical examination in excluding several miscellaneous findings but was far superior in terms of identifying these findings when they were present, although the accuracy of HHU was also not exemplary in this situation.
Table 4 illustrates the performance of HHU and physical examination in the assessment of substantial (moderate or severe) valve disease. Only the 3 diseases that were present in more than 10 individuals in this population are listed. For all 3 conditions (mitral as well as tricuspid regurgitation and aortic stenosis), the 2 methods were equivalent in terms of excluding disease; however, HHU was markedly superior in identifying the presence of moderate to severe mitral and tricuspid regurgitation, but not aortic stenosis.
Diagnosis based on indication
Table 5 depicts the performance of physical examination and HHU based on the clinical indication for the original echocardiogram. HHU was vastly superior to physical examination for assessment of LV function in the 172 patients referred to the echocardiography laboratory with chest pain or dyspnea as the primary or secondary indication. Both normal and abnormal LV function were far better assessed by HHU than by physical examination. In these 172 patients, the putative cause of patient symptoms was correctly assessed in 152 patients (88%) by HHU and in only 78 (45%) by physical examination (p < 0.0001).
Moderate or severe valve disease was rarely the cause of murmur in the 50 patients with this indication; however, HHU correctly identified all 38 patients who did not have significant valve disease compared with only 29 such patients identified by physical examination. In terms of finding a cardiac source of stroke, almost one-half (12) of these 26 patients had no cardiac abnormalities on standard echocardiography. Eight of 14 patients with stroke who had some abnormality on standard echocardiography were correctly identified by HHU compared with only 4 on physical examination. Similarly, of 20 patients with arrhythmias, cardiac structural abnormalities were found in only 10 on standard echocardiogram. Of these, 8 were correctly identified by HHU compared with only 3 by physical examination. Miscellaneous indications were too few for meaningful comparison.
Level of experience
Of 17 cardiologists who performed physical examination, 4 had <5 years of experience and performed 23.5% of the examinations, 3 had 5 to 10 years of experience and performed 17.6% of the examinations, and 10 had >10 years of experience and performed 58.8% of the examinations. Except for the presence of pulmonary hypertension, greater experience was not correlated with a more accurate diagnosis. Correct diagnosis by HHU was also not related to the echocardiography experience of the cardiologist for any of the conditions.
Table 6 illustrates further testing suggested after physical examination and HHU in the 250 patients. Of the 142 patients with at least 1 abnormality on the standard echocardiogram, further testing was suggested in 128 patients (90%) after physical examination and in 129 patients (91%) after HHU (p = 1.0). There was a marginal increase in charges of $5,874 after HHU examination, mostly related to an additional angiogram suggested after HHU. In comparison, of 108 patients without any abnormalities on standard echocardiography, further testing was suggested in 89 (82%) undergoing physical examination versus only 60 (56%) undergoing HHU (p < 0.0001). There were appreciable savings because of the reduction in the number of downstream tests suggested after HHU. Most of the cost savings were achieved by a more accurate assessment of LV function by HHU.
Our modeling showed that HHU had an average cost of $644.43 versus an average cost of $707.44 for physical examination. This yielded a savings of $63.01 per patient for HHU versus physical examination. We then performed a sensitivity analysis that examined the additional length of hospital stay required when additional tests are ordered. With the assumption that additional tests would add another half-day hospital stay, the average cost of HHU was $1,262.43 versus $1,415.44 for physical examination.
Our study demonstrates that HHU provides timely and more accurate diagnosis than physical examination for the majority of common cardiovascular abnormalities, as well as for the common indications for which echocardiograms are ordered. Furthermore, finding no significant abnormality on HHU is also likely to result in less downstream testing and thus potentially could reduce the overall cost for patients being evaluated for suspected cardiovascular disease.
Some form of HHU has been available in the clinical setting now for a decade or more. Initial studies using relatively larger devices reported that they compared favorably with the standard echocardiogram in terms of making cardiac measurements (7–12) and the diagnosis of specific cardiac conditions (13–20). These devices have also begun to be used to assist with vascular access (21) and removal of fluid from the thorax and pericardium (22). They are being placed in critical care units or emergency departments to assist in the evaluation of hemodynamically compromised patients, to rule out severe LV dysfunction, pericardial effusion, and pulmonary embolism, for example (23–27). Guidelines have been developed by professional societies for the use of focused ultrasound examinations in these settings (21,28–30).
HHU has also been used as a screening and diagnostic tool in locations without access to the standard echocardiogram (31–34). Images have been interpreted either on site or remotely through some form of telemedicine or Internet-based access to uploaded images (33,35). In 1 instance, more than 1,000 patients were scanned by 9 sonographers, and images were interpreted through an Internet site by 75 cardiologists from remote continents (33). One-third of these screened patients with suspected cardiac conditions were found to have cardiovascular abnormalities.
There have also been reports on the ease of training medical students and residents on the use of HHU, thus enhancing their ability to make a correct diagnosis (4,7,18,36). Several medical schools have incorporated HHU in their core curriculum. However, attempts at introducing HHU to practicing physicians (including cardiologists, all of whom are now being trained in echocardiography and many of whom interpret standard echocardiograms in their hospitals or practices) have failed for several reasons. First is the reluctance on the part of most physicians to obtain additional, albeit minimal, training in the use of HHU. Second is the perception that HHU examination takes considerably more time than physical examination, thus making it unfeasible in a busy practice. Third, there is no financial or other incentive for it; it takes more time without providing additional compensation. Fourth, at least among some cardiologists, there may be a concern that it will reduce the need for a standard echocardiogram, which may adversely affect their income in the current fee-for-service setting. Fifth is the opposite concern that based on HHU, spurious echocardiograms will be ordered, increasing overall cost. Sixth is the argument that HHU is not as accurate as the standard echocardiogram (29,30,37,38).
Because HHU is so superior to physical examination in terms of making a diagnosis and potentially reducing the need for unnecessary tests, these arguments have very little import. In terms of additional training, physicians routinely receive continuing medical education, and a 2-day course on the use of HHU complemented by readily available supplemental online training could easily be implemented. HHU takes marginally more time than physical examination (mean of 8 min for HHU vs. 5 min for physical examination in our study, with similar results in another study ). For the additional time taken, and given that HHU use can potentially reduce cost to the system, its use makes sense and should be incentivized.
The use of HHU could reduce referrals for the standard echocardiogram, at least among cardiologists and even among other physicians as they become accustomed to its use. In a fee-for-service environment, this may be a disincentive, but in a capitated one, this may contribute to lowering healthcare costs. A previous study also showed that when HHU was performed by appropriately trained personnel, referrals for standard echocardiogram did not increase and normal findings on HHU decreased downstream testing (39). Although HHU is not as robust as a standard echocardiogram for confirming or excluding cardiac findings, that is not its primary purpose.
Our study was intentionally designed to test our hypotheses in the best-case scenario; both the physical examination and HHU were performed by board-certified cardiologists in patients suspected of having cardiovascular abnormalities. Both methods, therefore, had the best chance to succeed. In this setting, HHU identified 82% of patients with cardiac abnormalities on standard echocardiography, whereas physical examination identified only 47%. The putative cause of patient symptoms (based on indication for the standard echocardiogram) was correctly assessed in 88% of patients by HHU and in only 45% by physical examination. HHU was superior to physical examination in almost all categories of cardiovascular diseases. Interestingly, the level of experience did not influence the accuracy of either physical examination or HHU.
Importantly, when no abnormalities were found, the physician using HHU felt more confident not ordering an additional test than the one performing physical examination. Further testing was suggested in 82% of patients with no abnormalities undergoing physical examination versus only 56% undergoing HHU. As a consequence, the total estimated cost decreased. The actual additional tests performed in these patients were close to those suggested by users of HHU. Most of the patients in whom no additional testing was suggested after HHU examination were those in whom LV and RV function assessment or murmur formed the basis of the standard echocardiogram indication. These indications define the majority of patients referred for echocardiography. With increasing familiarity with HHU and positive feedback regarding patient outcomes, it is likely that fewer standard echocardiograms will be ordered in patients undergoing HHU examination.
The number of patients was modest, although for most disease conditions, the power calculation suggested that 250 patients were adequate. The misdiagnosis of valvular disease by physical examination was influenced by the severity of disease in our study rather than just its presence or absence. Our cost estimates were based on assumptions of additional tests. With a few exceptions, the actual tests ordered, however, were very close to those suggested by the physicians. Future studies could randomize patients to either approach and examine downstream costs as well as outcomes. Finally, the value of HHU needs to be tested in the day-to-day practice of a primary care physician or midlevel provider to assess its impact on the practice of medicine.
Our findings indicate that the use of HHU should be encouraged among cardiologists either in addition to or in lieu of the stethoscope. Most contemporary trained cardiologists can perform and interpret a basic echocardiographic examination. As their experience with HHU increases, they are likely to decrease the use of the stethoscope. Future developments in HHU devices should allow auscultation of the lungs with the same probe that images the heart (using sound). Although ultrasound can detect comets and Kerley B lines in the lungs, these usually represent advanced stages of heart failure. Auscultation of the lungs is still necessary to assess the presence or absence of early stages of heart failure. The ability to auscultate with the same device will provide a truly comprehensive cardiovascular examination. These devices could have applications (“apps”) that would allow physicians to access Internet-based information. They could even act as a pager or cell phone. The size needs to be even smaller, to fit easily into a coat pocket, and the probe needs to communicate wirelessly with the device. In this manner, a physician could have an all-purpose tool in his or her pocket that would be more in keeping with the 21st century than the stethoscope, a 200-year-old technology whose time should be over.
This research was supported in part by a research grant from GE Medical, Milwaukee, Wisconsin and was presented in part at the 2013 annual scientific sessions of the American College of Cardiology in San Francisco, California, the American Society of Echocardiography in Minneapolis, Minnesota, and the American Heart Association in Dallas, Texas. Dr. Caughey serves as a medical advisor to CellScape, Ariosa Diagnostics, and MindChild Medical. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- Abbreviations and Acronyms
- body mass index
- handheld ultrasound
- left ventricular
- right ventricular
- Received January 2, 2014.
- Revision received April 28, 2014.
- Accepted May 6, 2014.
- American College of Cardiology Foundation
- Panoulas V.F.,
- Daigeler A.L.,
- Malaweera A.S.,
- et al.
- Spencer K.T.,
- Anderson A.S.,
- Bhargava A.,
- et al.
- Troianos C.A.,
- Hartman G.S.,
- Glas K.E.,
- et al.,
- Councils on Intraoperative Echocardiography and Vascular Ultrasound of the American Society of Echocardiography
- Testuz A.,
- Müller H.,
- Keller P.F.,
- et al.
- Seward J.B.,
- Douglas P.S.,
- Erbel R.,
- et al.
- Spencer J.K.,
- Adler R.S.
- Goodkin G.M.,
- Spevack D.M.,
- Tunick P.A.,
- Kronzon I.
- Bruce C.J.,
- Montgomery S.C.,
- Bailey K.R.,
- Tajik J.,
- Seward J.B.