Results
Study Population and Clinical Findings
Between January 2008 and March 2009, 2261 consecutive male Caucasian athletes were enrolled. Mean age was 12.4±2.6 years. The demographic and clinical characteristics of the population, divided in two subgroups, depending on the presence of TWI, are summarised in Table 1.
No athlete had known cardiac disease and 26 athletes (1.1%) were found to have abnormal personal medical history. In all, 42 athletes (1.9%) reported positive family medical history, mostly for ischaemic heart disease, but also for dilated cardiomyopathy (one athlete), inter-ventricular septal defect (one case) and aortic disease (one case). No athletes reported a family history of sudden cardiac death. A total of 18 athletes (0.8%) had significant abnormal findings on physical examination (Table 1). In general, athletes with TWI were younger, with smaller BSA, BMI and less total training hours. No significant differences were found in the family history or physical examination.
Electrocardiographic Findings
Electrocardiographic findings are presented in Table 2, in which ECG abnormalities are categorised by their likely origin: common/training-related or uncommon/training-unrelated, and the study population is divided in two subgroups, depending on the presence of TWI.
The two subgroups were homogeneous for the electrocardiographic parameters, except for heart rate, which was slightly higher in athletes with TWI, and QRS duration, which conversely, was lower (Table 2).
TWI in at least two consecutive leads was found in 136 athletes (6.0%), distributed in anterior, extended anterior, inferior and infero-lateral leads in 126/136 (92.6%), 2/136 (1.5%), 3/136 (2.2%) and 5/136 (3.7%) athletes, respectively (Table 3).
TWI was more common among individuals aged 8–10 (75/599, 12.5%) and 11–13 years (45/857, 5.2%) than in those aged 14–16 (14/689, 2%) or 16–18 years (2/116, 1.8%) (Table 3). A significant association (p<0.001) was found between age groups and the distribution of T waves in ECG leads. Other training-unrelated ECG abnormalities are listed in Table 2.
Echocardiographic Findings
Echocardiographic findings in athletes with or without TWI are presented in Table 4. Distribution of various parameters is depicted in figures 1 and 2.
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Figure 1.
Age, heart rate and LV mass distribution in athletes with or without T wave inversion (TWI). Age and HR distribution are depicted at the top, on the left and on the right, respectively; LV mass and LV mass indexed for height distribution are depicted down, on the left and on the right, respectively. Whiskers plot highlights differences between groups.
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Figure 2.
End-diastolic and end-systolic diameter, inter-ventricular septum and posterior wall thickness distribution in athletes with or without T wave inversion (TWI). End-diastolic and end-systolic diameters are depicted at the top, on the left and on the right, respectively; inter-ventricular septum and posterior wall thickness distribution are depicted down, on the left and on the right, respectively. Whiskers plot highlights differences between groups.
Athletes with TWI had small ventricular dimensions, walls thickness and atrial diameter, according to their younger age (Table 4). No differences were found in TTE measurements indexed by BSA and/or height (Table 4). Abnormal TTE was observed in 9/136 (6.6%) athletes with TWI and in 93/2125 (4.5%) athletes without TWI. The distribution of TTE findings in athletes, as well as their relationship with TWI localisation in ECG leads, is depicted in figure 3. There were no cases of ARVC. Only 6 out 126 (4.8%) athletes with TWI in the anterior leads had minor TTE abnormalities, including patent foramen ovale (three cases: one age 8, two age 10), mitral valve prolapse (two cases: one age 10, one age 12) and bicuspid aortic valve (one age 12). No athletes with TWI in the extended anterior or inferior leads had any echocardiographic findings. Among the five subjects with infero-lateral TWI, 3 (60.0%) had significant TTE abnormalities, including one HCM (a 13-year-old) and two LVH (one age 16, one age 17); the remaining two had normal TTEs.
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Figure 3.
Relationship between ECG and transthoracic echocardiogram (TTE) findings in athletes with or without T wave inversion (TWI) at ECG. Arrows indicate subgroups. PFO, MVP and BAV indicate patent foramen ovale, mitral valve prolapse and bicuspid aortic valve, respectively.
The vast majority of athletes without TWI (2032/2125, 95.6%) had normal TTE findings. However, cardiac abnormalities, in some cases serious, were found in 93 children (4.4%), including: HCM (one), mild LVH (six), mild LV dilation (LVD) (six), inter-atrial septal defect (13), bicuspid aortic valve (16), patent foramen ovale (24), inter-atrial septal aneurysm (14), mitral valve prolapse (eight), patent ductus arteriosus (two), and pulmonary artery dilation or subvalvular pulmonic membrane (two and one, respectively). In the athlete with HCM and normal T waves, ECG revealed deep Q waves in infero-lateral leads, suggestive of cardiomyopathy.
Sensitivity, Specificity, Positive and Negative Predictive Values of TWI for Preparticipation Screening
The sensitivity and specificity of TWI in identifying cardiac TTE abnormalities mandating sport restriction (ESC guidelines for preparticipation screening) were 0.7% (95% CI 0.004% to 0.0012%) and 100% (95% CI 0.997% to 1.000%), respectively. The positive and negative predictive values were 50% (95% CI 0.479% to 0.521%) and 94.0% (95% CI 0.929% to 0.949%), respectively. The sensitivity, specificity and predictive values of TWI according to their localisation on the surface ECG, in detecting TTE abnormalities needing clinical follow-up and in identifying cardiac electro-structural abnormalities mandating sport restriction or needing clinical follow-up are presented in the online supplementary appendix http://heart.bmj.com/content/101/3/193/suppl/DC1 (table S1A, B respectively).