Focused Transthoracic Echocardiography by Sports Medicine Physicians

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1 ORIGINAL RESEARCH Focused Transthoracic Echocardiography by Sports Medicine Physicians Measurements Relevant to Hypertrophic Cardiomyopathy Eugene S. Yim, MD, MPH, Edward F. Gillis, RDCS, Krystin Ojala, CSCS, James MacDonald, MD, Frederick C. Basilico, MD, Gianmichael D. Corrado, MD Received May 9, 2012, from the Division of Sports Medicine, Children s Hospital Boston, Boston, Massachusetts USA (E.S.Y., J.M., G.D.C.); Department of Cardiology, New England Baptist Hospital, Boston, Massachusetts USA (E.F.G., F.C.B.); and Division of Sports Performance and Sports Medicine, Northeastern University, Boston, Massachusetts USA (K.O., G.D.C.). Revision requested June 15, Revised manuscript accepted for publication July 5, Address correspondence to Eugene S. Yim, MD, MPH, Division of Sports Medicine, Children s Hospital Boston, 319 Longwood Ave, Boston, MA USA. eyim@bidmc.harvard.edu Abbreviations ECG, electrocardiography; ICC, intraclass correlation coefficient; IVSd, end-diastolic interventricular septal thickness; LVIDd, end-diastolic left ventricular internal diameter; LVPWd, end-diastolic left ventricular posterior wall thickness Objectives The purpose of this study was to investigate whether sports medicine physicians can use portable echocardiography to obtain measurements pertinent to hypertrophic cardiomyopathy. Methods Thirty male collegiate athletes, aged 18 to 21 years, were prospectively enrolled. Focused portable echocardiography was performed by a board-certified sports medicine physician and a resident physician, followed by comprehensive echocardiography within 2 weeks by a registered diagnostic cardiac sonographer. A left parasternal long-axis view was acquired to measure 3 dimensions: (1) end-diastolic interventricular septal thickness (IVSd),(2) end-diastolic left ventricular internal diameter (LVIDd), and (3) end-diastolic left ventricular posterior wall thickness (LVPWd). Results Intraclass correlation coefficients between the sports medicine physician and the sonographer were strong: 0.77 for IVSd, 0.73 for LVIDd, and 0.64 for LVPWd. Intraclass correlation coefficients between measurements by the resident physician and sonographer were strong to moderate: 0.61 for IVSd, 0.62 for LVIDd, and 0.63 for LVPWd. Across all 3 readers, intraclass correlation coefficient calculations were 0.77 for IVSd, 0.81 LVIDd, and 0.75 for LVPWd, which indicated strong inter-rater reliability. Conclusions Sports medicine physicians are able to obtain measurements relevant to the diagnosis of hypertrophic cardiomyopathy with focused portable echocardiography that are consistent with comprehensive echocardiography by a registered sonographer. Key Words athletes; echocardiography; hypertrophic cardiomyopathy; sports medicine; sudden cardiac death Sudden cardiac death has captured the attention of the medical community and the general population over the years. It has been of particular interest to the sports medicine community because of its potentially devastating impact on the lives of young athletes. The underlying causes of sudden cardiac death vary by region, with arrhythmogenic right ventricular cardiomyopathy/dysplasia accounting for most cases (22%) of sudden cardiac death in certain regions, such as the Venuto region of Italy, whereas in the United States most cases (up to 48%) are associated with hypertrophic cardiomyopathy. 1,2 Conditions such as hypertrophic cardiomyopathy are therefore especially relevant to the care of athletes in countries such as the United States because they represent the leading causes of sudden cardiac death in the young population during physical exertion. 1, by the American Institute of Ultrasound in Medicine J Ultrasound Med 2013; 32:

2 Although often asymptomatic, athletes with hypertrophic cardiomyopathy can present with symptoms associated with left ventricular outflow tract obstruction: dyspnea, fatigue, exercise intolerance, dizziness, and syncope. 4 Hypertrophic cardiomyopathy also predisposes athletes to arrhythmias, including atrial fibrillation, premature ventricular depolarization, ventricular couplets, nonsustained ventricular tachycardia, and sustained ventricular tachycardia. 5 Unfortunately, sudden cardiac death can also be the first and only manifestation of hypertrophic cardiomyopathy. 6 The potential lethality of hypertrophic cardiomyopathy explains why it has been incorporated into screening programs for athletes participating in competitive sports worldwide. In countries across Europe and Asia, screening echocardiography has been incorporated as a part of screening programs that are used to determine eligibility for participation in competitive sports. These programs incorporate screening echocardiography selectively or routinely as a part of comprehensive evaluations that include medical evaluation, electrocardiography (ECG), and additional workups such as exercise stress testing, continuous rhythm monitoring, and cardiac imaging. 7,8 Hypertrophic cardiomyopathy is classically associated with asymmetric septal hypertrophy, with the following 2-dimensional echocardiographic criteria that have been used for diagnosis: unexplained maximal wall thickness greater than 15 mm in any myocardial segment, septal/ posterior wall thickness ratio greater than 1.3 in normotensive patients, and septal/posterior wall thickness ratio greater than 1.5 in hypertensive patients. 9 Although comprehensive echocardiography by a sonographer is traditionally used to diagnose hypertrophic cardiomyopathy with these criteria, a focused protocol for point-of-care echocardiography could be developed for use by sports medicine physicians to help screen for hypertrophic cardiomyopathy. Such a protocol may be feasible given the development of portable and handheld ultrasound devices that have proven equally reliable and accurate in measuring cardiac parameters relevant to hypertrophic cardiomyopathy. 10 Similar precedence has also been set in other fields, in which focused sonographic protocols have become a part of standard practice. 11,12 As sonography becomes more avidly incorporated into the field of sports medicine, the potential use of portable sonography in this manner should be considered. This study began to explore that possibility by evaluating the reliability of portable sonography in the hands of a sports medicine physician and a resident physician. Materials and Methods Study Population Thirty male athletes participating in National Collegiate Athletic Association Division I collegiate sports, aged 18 to 21 years, were prospectively enrolled. Athletes participated in one of the following sports: track and field (10), crew (7), soccer (6), baseball (6), and ice hockey (1). All participants were healthy and had no known history of cardiovascular disease. Participants were recruited by convenience sampling at the athletic training facility of the university. The study was approved by the Institutional Review Board at Northeastern University as well as New England Baptist Hospital. Written informed consent was obtained from all participating athletes. Echocardiography Protocol Portable echocardiography was performed initially at university facilities by a sports medicine physician and a resident physician. Within 2 weeks, the participants followed up at a local hospital to receive comprehensive echocardiography by a registered diagnostic cardiac sonographer. The sports medicine physician was board certified in sports medicine and had greater than 5 years of clinical experience in the use of sonography, although most of the experience was in musculoskeletal sonography. The physician received training in sonography through residency training and also completed a weekend course in advanced echocardiography before the onset of the study. The resident physician was a postgraduate year 2 resident in emergency medicine planning for specialization in sports medicine. The resident physician had 2 years of clinical experience in the use of sonography, through requisite teaching in sonographic techniques provided by residency training in emergency medicine. Both individuals received targeted training by a sonographer before the study. Training sessions comprised 4 hour-long sessions focused on obtaining the measurements relevant to the study. Echocardiographic examinations were performed with the participants at rest in the left lateral decubitus position. The readers obtained their measurements independently and were blinded to the results of other readers. Portable echocardiography was performed with a commercially available battery-powered portable platform (MicroMaxx; SonoSite Inc, Bothell, WA) equipped with a 2.5-MHz phased array transducer and a 10.4-in/26.4-cm diagonal liquid crystal display screen. Comprehensive echocardiography was performed with a Vivid 7 ultrasound system (GE Healthcare, Wauwatosa, WI) equipped with an M4S phased array transducer using second-harmonic 334 J Ultrasound Med 2013; 32:

3 (1.7/3.4-MHz) imaging. Images were viewed on a 21-in liquid crystal display. Measurements were acquired from a frozen-frame image captured during end diastole. An ECG signal was used to identify end diastole on comprehensive echocardiography. However, this signal was not available for portable echocardiography. With portable echocardiography, end diastole was identified by selecting the frame with the largest left ventricular areas, with associated closure of aortic and mitral valves. A left parasternal long-axis view was acquired to measure 3 dimensions (Figure 1): (1) end-diastolic interventricular septal wall thickness (IVSd), (2) end-diastolic left ventricular internal diameter (LVIDd), and (3) end-diastolic left ventricular posterior wall thickness (LVPWd). The IVSd was measured from the leading edge of the right septal echo to the leading edge of the left septal echo, approximately 1 cm from the aortic outflow tract. The LVIDd was measured from the leading edge of the left septal echo to the leading edge of the endocardial echo. The LVPWd was measured from the leading edge of the endocardial echo to the leading edge of the epicardial echo. These measurements were chosen in consultation with the sports cardiologist involved as an author of the study because of their reliability and relevance to the diagnosis of hypertrophic cardiomyopathy in athletes. As mentioned previously, measurements of IVSd and LVPWd are not only helpful as absolute measures of wall thickness but also useful in calculating the septal/posterior wall ratios used as diagnostic criteria for hypertrophic cardiomyopathy. The LVIDd was also chosen because it has also been used in diagnosing hypertrophic cardiomyopathy, which is classically associated with decreased internal diameters of the left ventricle as a result of hypertrophy. Figure 1. A parasternal, long-axis view of the heart was obtained from each athlete. Three measurements were taken for each athlete: (1) IVSd, (2) LVIDd, and (3) LVPWd. Statistical Analysis Continuous data are presented as mean ± standard deviation. The measurements obtained by the sports medicine physician and resident physician were compared to the values obtained by the sonographer through pair-wise evaluations of concordance using intraclass correlation coefficients (ICCs) for each of the 3 parameters measured. To evaluate agreement/concordance among all 3 readers, ICC calculations were computed across all 3 readers for each parameter. P <.05 was considered statistically significant. All analyses were performed with an online opensource statistical program. 13 Results Study Population Thirty athletes were recruited for the study, and all athletes were able to follow up within 2 weeks of the initial echocardiographic examinations for comprehensive echocardiography. Portable Versus Comprehensive Echocardiography The means ± standard deviations for each of the measured parameters by all 3 readers are displayed in Table 1. The ICCs between measurements by the sports medicine physician and the sonographer were 0.77 for IVSd, 0.73 for LVIDd, and 0.64 for LVPWd.The ICCs between measurements by the resident physician and sonographer were 0.61 for IVSd, 0.62 for LVIDd, and 0.63 for LVPWd. Comparing concordance across all 3 readers, ICC calculations were 0.77 for IVSd, 0.81 LVIDd, and 0.75 for LVPWd. Discussion Echocardiographic measurements by a sports medicine physician and a resident physician were found to have strong or strong to moderate agreement when compared to values obtained by a sonographer in a dedicated echocardiography laboratory. Pair-wise comparison between the sports medicine physician and the sonographer showed strong agreement for IVSd and LVIDd and strong to Table 1. Measurements by 3 Readers Sports Medicine Resident Registered Parameter Physician Physician Sonographer IVSd, mm 10.0 ± ± ± 1.0 LVIDd, mm 53 ± ± ± 3.0 LVPWd, mm 9.1 ± ± ± 0.9 Values are mean ± SD. J Ultrasound Med 2013; 32:

4 moderate agreement for LVPWd. Pair-wise comparison between the resident physician and the sonographer showed strong to moderate agreement across the board. Measurements for IVSd, LVIDd, and LVPWd by the 3 readers had similar means, with slight overestimation of values obtained by portable echocardiography compared to comprehensive echocardiography. Despite this trend, none of the measurements by the sports medicine physician or the resident physician fell into the range of abnormal. This finding was expected given that all athletes in the study were otherwise healthy, with no history of cardiovascular disease. Although the sports medicine physician measured IVSd and LVIDd accurately, LVPWd was measured with less precision. The correlation coefficients for IVSd and LVIDd were comparable to those shown in previous studies comparing portable and comprehensive echocardiography in the hands of sonographers. 10 Of note, these previous studies also showed that LVPWd was more difficult to measure reliably than the other parameters, although sonographers were still able to maintain a strong correlation between portable and comprehensive echocardiography. Our data support the idea that IVSd and LVIDd are more accurately measured by portable echocardiography than LVPWd. Technical differences between portable ultrasound systems and standard echocardiography machines may be responsible, although further study would be required to investigate these factors. Although the measurements by the resident physician did not have as strong a correlation to comprehensive echocardiography as those obtained by the sports medicine physician, the level of agreement across all 3 readers was strong. Inter-rater agreement across all readers involved in the study showed strong agreement, with ICC calculations ranging from 0.77 to This level of agreement is comparable to that shown in previous studies comparing linear measurements by portable versus comprehensive echocardiography in the hands of certified sonographers. 10 Therefore, agreement may have been even stronger had the images been taken by the same type of machine by all readers in the study. If a similar level of accuracy can be attained broadly by other sports medicine physicians, this technique holds the potential to affect clinical practice in the future. In the United States, where hypertrophic cardiomyopathy is the most common cause of sudden cardiac death in young athletes, current screening practices have been proven to be haphazard and inconsistent. Although the American Heart Association has published recommendations for cardiovascular screening in athletes, most physicians and athletic directors are either unaware of these recommendations or have not implemented them into practice. 14 Furthermore, incorporating particular diagnostic tests, such as ECG, has faced controversy and disagreement, with some advocates pointing to its successful use in other countries, whereas opponents claim that the diagnostic test lacks specificity and leads to unnecessary referrals to specialists Since comprehensive echocardiography is considered an accurate diagnostic test for evaluating the presence of cardiovascular abnormalities such as hypertrophic cardiomyopathy, the development of a focused protocol for echocardiography could serve as a critical addition to a broader, more effective screening strategy for hypertrophic cardiomyopathy. The most prevalent argument against this idea, however, is that it would not be cost-effective because of the low prevalence of abnormalities in the athletic population and the resultantly large number of athletes that would have to be screened to detect one athlete with abnormalities. 19 Training sports medicine physicians in portable echocardiography may address this point by potentially improving accessibility of the diagnostic test. In addition, such testing could be administered selectively to athletes at higher risk or in individuals who screen positive by conventional methods (history, physical examination, and ECG), in an attempt to reduce false-positive rates and unnecessary referral to specialists. Once a specific strategy incorporating this focused technique is implemented, cost-effectiveness analyses will be invaluable in justifying utility in this setting. Limitations Although our study showed a strong correlation between values obtained by a sports medicine physician and a sonographer, a stronger correlation has been documented in previous studies comparing sonographers. 20 Part of this discrepancy should be attributed to the difference in devices used by the physician and the echocardiographer in our study. Although differences in the imaging characteristics of the echocardiography machines themselves may explain part of this variability, the method for identifying end diastole may also have contributed to this discrepancy. An electrocardiographic tracing was not available to identify end diastole on portable echocardiography, adding a degree of complexity to obtaining correct imaging for the sports medicine physician and resident physician. Regardless, as discussed previously, studies comparing the correlation between echocardiographers using portable and comprehensive echocardiography machines have shown a similar level of correlation as that seen in our study. The discrepancy between measurements obtained by the sports medicine physician and resident physician will 336 J Ultrasound Med 2013; 32:

5 also require further investigation. Although the sports medicine physician had a moderate to strong correlation compared to the sonographer, the resident physician had a weaker correlation in measurements. This finding can presumably be attributed to the level of training and experience with sonography that differed between the two readers, but it remains to be proven. The quality and substance of training likely affect accuracy in these techniques, but the exact quantity and content of required training remain an open question. If such techniques are to be incorporated more widely into practice, appropriate training programs will have to be developed to ensure adequate proficiency. This process may require general training in sonography, focused training in taking particular measurements relevant to hypertrophic cardiomyopathy, as well as a certain amount of clinical experience. Another major limitation of our study was its sample size. The study was designed as a pilot to assess feasibility for further investigation and was not meant to produce definitive results. However, the small sample size of 30 restricts heterogeneity of the sample and also limits generalizability of the data to larger populations. Further investigation with larger numbers and even recruitment of multiple study sites will help improve validity and generalizability of data. Another limitation to the implications of our study is that only healthy athletes without a history of cardiovascular disease were recruited for the study. As expected, measurements obtained by all readers were within normal cardiac physiologic limits. Although this study provides preliminary evidence that trained physicians can obtain accurate measurements using portable echocardiography, it does not prove that this technique can be applied toward the diagnosis of hypertrophic cardiomyopathy. Before this technique can be applied specifically in this manner, additional studies including high-risk athletes as well as athletes with abnormal cardiac dimensions will be required to validate this method in its application for evaluating athletes for hypertrophic cardiomyopathy. Last, the parameters chosen for the focused protocol in our study may not be adequate to detect all cases of hypertrophic cardiomyopathy. A full evaluation for hypertrophic cardiomyopathy by comprehensive echocardiography includes not only the static measurements obtained in our study but also a number of more specialized dynamic techniques: spectral Doppler imaging to assess provoked gradients and dynamic outflow tract obstruction, color Doppler imaging to assess regurgitation and valve incompetence, and M-mode assessment to evaluate systolic anterior motion of the mitral valve. Our focused protocol was admittedly less comprehensive than such a formal evaluation, but the static measurements in our study were chosen because they could feasibly be applied to a broader screening protocol used by less experienced operators. The sensitivity and specificity of this limited evaluation must be evaluated before this technique can be justifiably incorporated into screening strategies for hypertrophic cardiomyopathy. Conclusions Sports medicine physicians may be able to obtain measurements with portable echocardiography that are relevant to the diagnosis of hypertrophic cardiomyopathy and consistent with those measured by sonographers in dedicated echocardiography laboratories. As more sports medicine physicians become proficient in the use of portable echocardiography, a focused protocol could provide the basis for a screening strategy for detecting hypertrophic cardiomyopathy in athletes. 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