Background
The reduction in the size of full-capability echocardiographic machines facilitates “out-of-hospital” transthoracic echocardiography (TTE). Data documenting the feasibility, yield, and logistical considerations of out-of-hospital TTE for preparticipation evaluation of athletes are sparse.
Methods
A multiyear study was conducted to examine the role of 12-lead electrocardiography for athlete screening in which TTE was used to document or exclude underlying structural heart disease. Using a commercially available portable transthoracic echocardiographic system, the rate of technically adequate imaging, diagnostic yield, and the time required for the completion of TTE (including setup, performance, and interpretation) were examined. TTE was performed in university medical offices and at “out-of-office” athletic facilities. Measurements were recorded during each year of the study to determine the impact of targeted attempts to improve efficiency.
Results
Four hundred sixty-seven of 510 participants had transthoracic echocardiographic images that were technically adequate for complete interpretation (imaging success rate, 92%). Echocardiographic evidence of physiologic, exercise-induced cardiac remodeling was observed in 110 of 510 (22%). Cardiac abnormalities with relevance to sports participation risk were detected in 11 of 508 participants (2.2%). Over 3 years, the average time for the completion of TTE (including setup, imaging, and interpretation) decreased (year 1, 17.4 ± 3 min; year 2, 14.0 ± 2.1 min; year 3, 11.0 ± 1.8 min; P < .001). This was driven by a significant decrease in the time required for TTE at out-of-office athletic facilities.
Conclusions
Community-based TTE in athletes is feasible and is associated with a high rate of technically adequate imaging. Importantly, there appears to be a significant learning curve associated with out-of-hospital TTE.
The development of full-capability, small-size echocardiographic machines represents an important technological advance and may facilitate “out-of-hospital” echocardiography. Given the accuracy of echocardiography for detecting structural and valvular heart disease, portable cardiac ultrasound has been proposed as a screening tool for specific cardiovascular conditions including left ventricular (LV) hypertrophy (LVH), LV dysfunction, and rheumatic heart disease.
Cardiovascular disease is the leading cause of sudden death among young competitive athletes. Consequently, preparticipation screening with medical history and physical examination is universally recommended. The role of additional testing, particularly the use of 12-lead electrocardiography (ECG), remains controversial because of concerns about test accuracy and cost-effectiveness. Recognition of the limited specificity of ECG coupled with the well-established high sensitivity and specificity of echocardiography has led to growing interest in the application of screening echocardiography among athletes. Echocardiography is now being applied during preparticipation screening in various populations, including professional and amateur athletes. Furthermore, there is growing interest in hospital-sponsored and private corporation–sponsored athlete screening, including echocardiography. Despite enthusiasm for such programs, data documenting their feasibility and performance remain sparse.
We recently conducted a multiyear study examining the use of ECG in preparticipation screening of university athletes in which all athletes underwent transthoracic echocardiography (TTE) to define disease prevalence. An a priori secondary objective was to examine the potential role of echocardiography in the context of athlete screening. In this report, we present data documenting the feasibility, logistical considerations, and diagnostic yield of portable echocardiography in university athletes.
Methods
Overview of Study Design
We enrolled prospective athletes in this study over 3 consecutive years (2006–2008). Athletes were eligible to participate if they were ≥18 years of age and were newly matriculated Harvard University students. The primary goal was to compare preparticipation screening with medical history and physical examination with a strategy that incorporated the addition of ECG, as previously reported. Echocardiography was performed primarily to document or exclude underlying structural cardiovascular disease with relevance to sports participation ( Table 1 ). However, an a priori secondary objective was to study the implementation of TTE during out-of-hospital sports clearance examinations, with a focus on the feasibility and diagnostic yield of portable echocardiography. To do so, we used a focused echocardiographic protocol and performed TTE in all athletes enrolled in the study during organized group screening sessions. Each participant underwent TTE once, at the time of his or her university preparticipation medical history and physical examination. The institutional review boards of Partners Human Research Committee and Harvard University approved the study protocol. Each participant provided written consent at enrollment.
| Structural and valvular cardiovascular conditions associated with sudden death in athletes | |
|---|---|
| Disorders of the myocardium | Hypertrophic cardiomyopathy Arrhythmogenic right ventricular cardiomyopathy Dilated cardiomyopathy Myocarditis |
| Disorders of the heart valves | Mitral valve prolapse Pulmonic stenosis Bicuspid aortic valve associated with any of the following
|
| Disorders of the coronary circulation | Congenital anomalies of coronary arterial origin and course |
| Disorders of the aorta | Aortic root/ascending aorta dilation
|
Echocardiography Protocol
We used a commercially available, portable, laptop-sized echocardiography system (Vivid-I; GE Healthcare, Milwaukee, WI) with a 1.9-MHz to 3.8-MHz phased-array transducer. Echocardiography was performed by a sonographer credentialed in cardiac ultrasound or a cardiologist trained in echocardiography. TTE was performed in various settings, including the health services building (i.e., the “office-based” setting) or at the university athletic training facility or the rowing program boathouses (i.e., “out-of-office” settings). At the university health service building, TTE was performed in a standard examination room. At the out-of-office locations, TTE was performed on a portable stretcher bed or massage table ( Figure 1 ). Participants were imaged at rest ≥12 hours after the most recent exercise training session. Two-dimensional, pulsed-Doppler, and Doppler tissue imaging were performed from standard parasternal and apical transducer positions with 2-dimensional frame rates of 60 to 100 frames/sec and tissue Doppler frame rates >100 frames/sec.
The echocardiographic protocol (17 images; Table 2 ) was designed to evaluate for conditions associated with sudden cardiac death in athletes. Structural and functional measurements were made in accord with current guidelines. Measurements of LV cavity size, LV wall thickness, left atrial diameter, right ventricular basal diameter, transmitral velocities, and pulsed-wave tissue Doppler velocities at the mitral annulus were reviewed by an echocardiography-trained cardiologist. On-site interpretation was enhanced by having the measurement images immediately available for the overseeing physician at the conclusion of each transthoracic echocardiographic study. Additional views could be added to the protocol at the discretion of the overseeing physician when suspected abnormalities were detected. Further measurements were subsequently performed offline (EchoPAC version 7.0; GE Healthcare) if needed to further evaluate pathology that was suspected on the basis of the on-site findings.
| Transducer position/view | Images | Number of Acquisitions |
|---|---|---|
| Parasternal long axis | 2D image CF Doppler of mitral and aortic valves RV inflow CW Doppler of tricuspid regurgitation | 3 |
| Parasternal short axis | 2D image of aortic valve CF Doppler of aortic valve 2D image of pulmonic valve CW Doppler of pulmonic valve 2D image at papillary muscle level 2D image at apex | 6 |
| Apical four chamber | 2D image maximizing both left and right ventricles PW Doppler of transmitral flow PW DTI of lateral mitral annulus PW DTI of septal mitral annulus PW DTI of RV base | 5 |
| Apical five chamber | 2D image CW Doppler of aortic valve | 2 |
| Apical two chamber | 2D image | 1 |
Definitions of Echocardiographic Findings
Participants were classified into one of three categories on the basis of findings on TTE ( Table 3 ): normal, physiologically remodeled, or suggestive of pathology or overtly abnormal. As previously described, these criteria were developed by integrating data from numerous prior studies that examined echocardiographic parameters in trained athletes. Individuals were categorized as having physiologic remodeling if they met one or more of the criteria in Table 3 and had no evidence of overt pathology. Among individuals with findings suggestive or diagnostic of pathology, ultimate determination of sport participation eligibility was determined in accordance with guidelines.
| Parameter | Male reference value | Female reference value |
|---|---|---|
| Normal cardiac structure ∗ | ||
| LV wall thickness | ||
| LV wall thickness (mm) | <11 | <10 |
| LV cavity size | ||
| LV internal diastolic diameter (mm) | <60 | <54 |
| RV cavity size | ||
| RV internal diastolic diameter (mm) | <34 | <34 |
| LA size | ||
| Maximal anterior-posterior diameter (mm) | <41 | <39 |
| Physiologic remodeling ∗ | ||
| Mild LVH | ||
| LV wall thickness (mm) | 11–13 | 10–12 |
| Mild LV dilation | ||
| LV internal diastolic diameter (mm) | 60–63 | 54–57 |
| Mild RV dilation | ||
| RV internal diastolic diameter (mm) | 34–37 | 34–37 |
| LA enlargement | ||
| Maximal anterior-posterior diameter (mm) | >41 | >39 |
| Suggestive of or diagnostic for true pathology ∗ | ||
| Marked LVH | ||
| LV wall thickness (mm) | ≥14 | ≥13 |
| Marked LV dilation | ||
| LV internal diastolic diameter (mm) | ≥64 | ≥58 |
| Marked RV dilation | ||
| RV internal diastolic diameter (mm) | ≥38 | ≥38 |
| Impaired LV diastolic function | ||
| Septal mitral annular E′ (cm/sec) | <8 | <8 |
| Lateral mitral annular E′ (cm/sec) | <10 | <10 |
| Valvular pathology | ||
| Bicuspid aortic valve | NA | NA |
| Mitral valve prolapse | NA | NA |
| Anomalous coronary origin | NA | NA |
∗ Criteria were developed from prior studies examining echocardiographic parameters in trained athletes.
Assessment of Transthoracic Echocardiographic Performance
The percentage of participants with images technically adequate for interpretation was determined, and reasons for inadequate imaging were documented. The time required for completion of TTE (including setup, performance, and interpretation) was documented. Assessment of the time required to complete a transthoracic echocardiographic study was performed for one of every five studies, with the sonographer or physician performing the study unaware that the time measurement was being made. Time for TTE was examined as a metric of setting (office based vs out of office) and the gender of the participant. Measurements were recorded during each year of the study to determine the impact of targeted attempts to improve efficiency.
Postscreening Clinical Follow-Up
Participants were followed clinically for the duration of their collegiate athletic careers. Transthoracic echocardiographic data were stored in a central database to facilitate access if needed during subsequent evaluation of athletes with cardiovascular symptoms. The number of athletes who came to medical attention after the initial screening and who had their echocardiographic information used as part of their clinical evaluation was recorded.
Statistical Analysis
Cardiac structural and functional parameters are reported as mean ± SD. The significance of gender differences in structural and functional parameters was compared using independent-samples t tests. Comparisons of transthoracic echocardiographic performance time across study years was assessed using one-way analysis of variance. Within-year transthoracic echocardiographic performance time as a function of study location and gender was compared using independent-samples t tests after confirmation of normal distribution. P values < .05 were considered significant.
Results
Study Population
A total of 510 university athletes (311 men, 199 women) participated in the study. The mean age of the participants was 19.0 ± 0.3 years. Self-reported race or ethnicity was Caucasian in 68%, Asian in 12%, black in 10%, Hispanic or Latino in 5%, and other in 5%. The mean height and weight were 1.80 ± 0.15 m and 82 ± 16 kg in men and 1.68 ± 0.09 m and 59 ± 12 kg in women. Prior exercise training was consistent with that expected of matriculating competitive collegiate athletes, with a mean total training time of 5.1 ± 2.2 h/wk during the 8 weeks before screening. Sport-type participation was diverse and typical for a university-level competitive athletics program, with football and rowing being the most common disciplines. Other participants competed in hockey (ice and field hockey), track and field, soccer, swimming, basketball, lacrosse, and baseball or softball.
Logistics of Echocardiographic Screening
Echocardiography was performed in the university health service building ( n = 363) and at out-of-office athletic facility locations, including the athletic training room and rowing boathouses ( n = 147). The average time for TTE, including setup, imaging, and interpretation, was 13.4 ± 2.3 min. Over 3 years, the average time for the completion of TTE decreased significantly (year 1, 17.4 ± 3 min; year 2, 14.0 ± 2.1 min; year 3, 11.0 ± 1.8 min; P < .001; Figure 2 A). This was driven by a significant decrease in the time required for out-of-office TTE, as the time for office-based (i.e., in the university health service building) echocardiography was consistent across study years ( Figure 2 B). Modifications to the setup procedure were responsible for this increased efficiency in the out-of-office settings and included confirmation of the time and location with the participant the day before TTE, using a preassigned subject identification system, confirming access to power sources, and confirming the ability to adjust room lighting. Furthermore, 3-year aggregate performance times for TTE were significantly less for male participants (12.1 ± 1.6 min) than for female participants (15.3 ± 2.6 min) ( P < .001).
Yield of TTE
Four hundred sixty-seven of the 510 participants (92%) had technically adequate images for complete evaluation of relevant pathology. Of the 43 participants with inadequate images, two were the result of generally poor acoustic windows in the settings of pectus excavatum and obesity. Failure to identify the right and left coronary ostia was the sole reason that the remaining 41 participants had inadequate images (i.e., the images were otherwise satisfactory for evaluation). Coronary artery origins were identified in the parasternal short-axis view. Use of the parasternal long-axis view did not increase the yield of identifying the right coronary artery origin. Of the 467 participants in whom coronary artery origin could be identified, it was normal in all cases.
Echocardiographic Findings
Of the 508 participants with adequate imaging, 387 (76%) had structurally normal hearts, 110 (22%) had evidence of physiologic remodeling, and 11 (2%) had evidence of suspected or overt pathology. Echocardiographic parameters of cardiac structure and function for the normal and physiologic remodeled participants are shown by gender in Table 4 . Mean values of all LV and right ventricular structural parameters were gender dependent. Individuals with echocardiographic abnormalities with potential relevance to sport participation risk ( n = 11) are detailed in Table 5 . Figure 3 highlights the role of on-site TTE to evaluate abnormal findings on ECG discovered during screening. After further noninvestigational testing, three of 11 participants had abnormalities that met recommendations for temporary or permanent sport restriction, including pulmonic valve stenosis (peak gradient of 55 mm Hg with right ventricular hypertrophy), hypertrophic cardiomyopathy (LVH with septal and posterior wall thicknesses of 18 mm and no regression during detraining; Figure 3 ), and myocarditis (LV dilation, LV dysfunction with an ejection fraction of 35%, and elevated serum troponin level after a recent viral illness). The overall prevalence of an abnormality that required sport restriction was 0.6% (three of 508), indicating that one case of relevant pathology was detected for every 170 athletes subjected to preparticipation screening.
| Parameter | Male ( n = 300) | Female ( n = 197) | ||
|---|---|---|---|---|
| Normal ( n = 209) | Physiologic remodeling ( n = 91) | Normal ( n = 178) | Physiologic remodeling ( n = 19) | |
| Structural parameters | ||||
| Interventricular septal thickness (mm) | 9.8 ± 0.9 | 11.6 ± 0.5 | 8.3 ± 0.7 ∗ | 10.6 ± 0.5 † |
| LV posterior wall thickness (mm) | 10.0 ± 1.2 | 11.8 ± 1.4 | 8.6 ± 1.1 ∗ | 10.7 ± 0.7 † |
| LV inner dimension at end-diastole (mm) | 51 ± 3 | 57 ± 5 | 42 ± 4 ∗ | 54 ± 4 † |
| LA diameter (mm) | 36 ± 4 | 40 ± 4 | 32 ± 3 ∗ | 38 ± 4 |
| RV end-diastolic diameter (mm) | 30 ± 5 | 36 ± 3 | 28 ± 4 ∗ | 33 ± 3 † |
| Functional parameters | ||||
| LV ejection fraction (%) | 65 ± 7 | 58 ± 4 | 68 ± 6 | 64 ± 6 † |
| Transmitral E wave (cm/sec) | 86 ± 16 | 96 ± 13 | 81 ± 17 | 88 ± 12 |
| Transmitral A wave (cm/sec) | 40 ± 12 | 42 ± 14 | 44 ± 10 | 44 ± 18 |
| E′ lateral PW (cm/sec) | 14.2 ± 5.3 | 18.8 ± 4.6 | 13.2 ± 4.2 | 15.6 ± 3.3 † |
| E′ septal PW (cm/sec) | 12.1 ± 3.2 | 14.1 ± 5.3 | 12.7 ± 4.1 | 13.8 ± 4.2 |
| A′ lateral PW (cm/sec) | 3.3 ± 2.1 | 3.9 ± 1.8 | 4.4 ± 1.6 ∗ | 4.8 ± 2.0 † |
| A′ septal PW (cm/sec) | 4.1 ± 2.0 | 3.9 ± 2.4 | 5.3 ± 2.2 ∗ | 4.6 ± 3.4 |
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