SCD in the young is usually due to concealed cardiovascular diseases, in the absence of alarming symptoms. The only way to detect and diagnose them in vivo is to submit the apparently healthy young people to a thorough clinical examination, which can unmask the hidden disease [1, 2].

This implies screening of the cardiovascular performance in the young on a large scale. In the past, cardiovascular examination was carried out in male conscripts in Italy, when the military service was obligatory. Since the military service became voluntary and restricted to few people, this opportunity has been lost in our Country. No in-depth visit is carried out at school. The only opportunity, for both males and females, is given by the obligatory pre-participation screening for sport activity eligibility. This is an important occasion not only to identify sick and to ensure healthy people but also to make proper interventions to prevent SCD.

Of course, sport activity is salutary and should be practiced since young age. However, the exercise is a double-edged sword, since it can offer protection in the long term from coronary atherosclerosis in those who are regularly engaged, but can entail in the short term the risk of SCD due to an underlying masked heart disease [3]. SCD can occur during sport activity with 2.5-fold rate than in people not practicing sport and is clearly related to the existence of hidden cardiovascular abnormalities, either structural or functional, of which the subject was unaware [4]. They may involve the aorta, the coronary arteries, the myocardium, the valves, the conduction system, or ion channels. The paradox is that the heart with these concealed morbid entities is compatible with an even excellent performance in terms of cardiac output, but it is vulnerable to sudden electrical instability like ventricular fibrillation or, more rarely, to structural breakdown like aortic rupture.

In the majority of cases, these abnormalities are easily suspected or even diagnosed at basal 12-lead ECG or stress test (see, for instance, cardiomyopathies, ion channel diseases, AV block, preexcitation syndromes). The physical examination alone, as carried out in the US, may skip cardiac diseases at high risk [5], such as hypertrophic cardiomyopathy. Among 33.735 screened athletes, we were able to detect 22 cases of people affected by hypertrophic cardiomyopathy [6]. Of these 22, 18 (82 %) were suspected thanks to abnormal ECG, whereas only 5 (23 %) had a positive family history or cardiac murmur. Thus, the sensitivity of our system was fourfold that the US one, with obvious implications in terms of SCD prevention [7, 8].

Also arrhythmogenic cardiomyopathy shows ECG abnormalities (large QRS complexes, epsilon waves, inverted T waves in the right precordial leads), which raise the suspicion that there is something wrong. The existence channelopathies is evident at the basal ECG (long and short QT interval, ST segment elevation). The same CPVT syndrome, in which the basal ECG is normal, shows onset of polymorphic ventricular arrhythmias at stress test ECG. Preexcitation syndromes show short PR, with or without delta wave. In all these conditions, the ECG is the only way to identify subjects at risk [8, 9].

Different from the US protocol, which includes only personal and family history with physical examination (not necessarily carried out by physicians) [5], the Italian protocol makes compulsory the employment of the ECG, and if some suspicion arises at the ECG, two-dimensional echo becomes mandatory as well [7, 9]. The last tool is the gold standard for the diagnosis of hypertrophic cardiomyopathy, by detecting left ventricular hypertrophy, either symmetric or asymmetric (≥13 mm).

Figure 13.1 is a flowchart of the protocol of pre-participation screening accomplished in Italy. First level includes family history, physical examination, and 12-lead ECG. If the findings are negative, eligibility for competitive sport is granted. If the findings are positive, a second-level investigation is accomplished, consisting of noninvasive tools (echo, stress test, signal-averaged ECG, Holter monitoring, cardiac magnetic resonance, and angio-computed tomography). If the diagnosis is not yet reached and the doubt persists, a third level of investigation is carried out with the use of invasive tools (coronary angiography, electrophysiologic study, electroanatomic mapping, and even endomyocardial biopsy). In the absence of any cardiovascular disease, green light for eligibility switches on.

Disqualification from sport activity is lifesaving “per se.” Since the initiation in Italy in 1982 of the nationally wide pre-participation screening (program including ECG), the annual incidence of SCD declined progressively up to 89 % in screened athletes in 2004 (see also Chap. 12) [8].

In contrast, the incidence of SCD did not demonstrate significant changes over the time in unscreened nonathlete young people that had not the opportunity to undergo cardiovascular screening.

Critics argue that false-positive ECG findings may lead to exclusion of many athletes that are not at risk of SD [10, 14, 15]. This is particularly true in certain ethnic groups, like black athletes, with a higher prevalence of ECG abnormalities that are a variant of normal. In our experience, 9 % of 42.386 athletes were found positive at first-level examination, but after further investigation, only 0.2 % were ultimately disqualified [6]. In England, false-positive rates were reported in 3.7 % [14, 15]. Employment of the recently updated guidelines for ECG interpretation has proven to significantly decrease the rate of false-positive among athletes [9]. Certainly, reducing the frequency of unnecessary disqualification and adapting, instead of prohibiting, sport activity (from high static-dynamic to low static-dynamic sports) remains one of the screening objectives.

Coronary artery diseases, either congenital or acquired, may escape detection at ECG. Accelerated coronary atherosclerosis in the young is typically represented by a single plaque in the proximal segment of the left anterior descending artery. It may be totally silent, both in terms of angina and ECG abnormalities at basal 12-lead and stress test recording. A coronary vasospasm, superimposed to the subostructive plaque, has been proven to be a precipitating factor of transient fatal ischemia, something that cannot be reproduced at the pre-participation screening [16]. The relative risk of sport-related SCD in premature coronary atherosclerosis is 2.6, again stressing the role of effort in precipitating cardiac arrest in affected subjects [4].

The relative risk in congenital coronary artery anomalies is even much more (RR = 79.0) as to say that if you are affected by these abnormalities, the risk to die suddenly is only if you make effort [4]. This emphasizes the concept on how much important would be the identification of affected people, because just disqualification from sport activity would be lifesaving. Unfortunately, again, basal 12-lead ECG and stress test ECG appeared normal in cases of coronary artery anomalous origin who died suddenly and thus got eligibility for sport activity [17].