Differentiating Left Ventricular Hypertrophy in Athletes from That in Patients With Hypertrophic Cardiomyopathy

METHODS:

Twenty-eight athletes free of cardiovascular disease were compared with 25 untrained patients with HC, matched for LV wall thickness (13 to15 mm), age, and gender. Clinical, electrocardiographic, and echocardiographic variables were compared.

RESULTS

Athletes had larger LV cavities (60 – 3 vs 45 – 5 mm, p <0.001), aortic roots (34 – 3 vs 30 – 3 mm, p <0.001), and left atria (42 – 4 vs 33 – 5 mm, p <0.001) than patients with HC. LV cavity <54 mm distinguished HC from athlete’s heart with the highest sensitivity and specificity (both 100%, p <0.001). Left atrium >40 mm excluded HC with sensitivity of 92% and specificity of 71% (p <0.001). Athletes showed higher e” velocity by tissue Doppler imaging than patients with HC (12.5 – 1.9 vs 9.3 – 2.3 cm/second, p <0.001), with values <11.5 cm/second yielding sensitivity of 81% and specificity of 61% for the diagnosis of HC (p <0.001).

The LV cavity (end-diastolic and end-systolic) was substantially larger in athletes compared with patients with HC; therefore, relative wall thickness (i.e., the ratio between LV wall thickness and cavity size) was lower in athletes. On individual analysis, none of the athletes showed an absolute LV end-diastolic diameter <55 mm, while most athletes (67%) exceeded 60 mm. None of the patients with HC exceeded an absolute LV cavity dimension of 53 mm, and most (88%) were <50 mm. (Fig 1, Fig 2).

In conclusion, in athletes with LV hypertrophy in the “gray zone” with HC, LV cavity size appears the most reliable criterion to help in diagnosis, with a cut-off value of <54 mm useful for differentiation from athlete’s heart.

Other criteria, including LV diastolic dysfunction, absence of T-wave inversion on electrocardiography and negative family history, further aid in the differential diagnosis. (Am J Cardiol 2014;114:1383-1389)

COMMENTS: Searching the clinical strength of each parameter

The aim of the study was to revise the ability of simple echo, ECG and clinical parameters for the distinction of HCM from athletic heart.

In other words, this paper is dealing with a very challenging topic, which is the distinction of the clinical parameters, that we use in differential diagnosis of athletes from HCM, according to the clinical strength of each factor. The clinical strength is based in the specificity and sensitivity of parameters that are already well known.   

In this study the conclusion is that LV cavity size appears the most reliable criterion (high specificity and sensitivity) to help in diagnosis, with a cut-off value of <54 mm useful for differentiation HCM from athlete’s heart. Diastolic function, ECG changes and family history have a significant impact.
Hypertrophic cardiomyopathy and athlete’s heart represent two distinct conditions, where pathologic processes or physiologic adaptations, respectively, result in an increase of heart wall dimensions (1), (2). A number of distinguishing features have been described in the medical literature based on the clear differences of the two conditions in the majority of cases (3), (4). Still, dilemmas may arise in cases of borderline wall hypertrophy (13-15mm) where both conditions may be responsible for the presenting phenotype (5).

So far acquired knowledge, allows physicians to highlight certain tests that bear significant “clinical strength” in the differential diagnosis process (7-15). Based in the published current medical literature, and inevitably using projections and often “gut feeling”, it is possible to nominate major and minor criteria according to the specificity and sensitivity for the differential diagnosis of HCM from athlete’s heart (16). The term major criteria is given to those tests that bear very high specificity for the diseased individuals (thus reliably identifying non-diseased individuals) and the term minor for those tests where sensitivity and specificity for the disease are more balanced (17). The criteria used for the differential diagnosis can be classified into categories: Demographics, electrocardiographic findings, structural characteristics, functional characteristics, lab tests, detraining effect and genetics.

In the case of differential diagnosis of HCM from athlete’s heart, there are a number of clues, based on the current literature, that support the notion of  tests bearing “clinical strength” that enable physicians to differentiate athlete’s heart from the hypertrophy of HCM.(7-16) These tests can represent criteria that combined would make the case for a definitive diagnosis. In fact, from a clinical point of view, a clear distinction can often be made between tests that are more or less powerful in supporting the diagnosis of HCM.

This approach, although somehow vague, can form the basis of nomination of major and minor criteria for the differential diagnosis of HCM from athlete’s heart. The term major can be used for tests that are thought to be highly specific for HCM, and the term minor for those tests that, although prevalent in HCM populations, would be still largely identifiable in healthy individuals or other diseases (TABLE 3). It is important to emphasise that, even though literature provides crucial information in nominating the criteria, there is still ample room for projections and “gut feeling” in this process.

For example, a strong case can be made for the female gender in individuals with borderline hypertrophy. Ιt is well accepted that physiologic hypertrophy in women rarely progresses beyond 11-12mm (1), (7),(8), even for elite athletes participating in vigorous training. A comparison of a large cohort of elite female athletes with male counterparts (8) also revealed a 23% less maximal left wall thickness and an 11% smaller left ventricular cavity dimension, suggesting that cardiac adaptation to intense training is clearly more pronounced in male athletes. The weight of evidence in current literature (8), (9) supports the concept that hypertrophy in elite female athletes beyond 12mm is an abnormal finding that calls for further investigation. With these clues it can be said that in the presence of borderline hypertrophy, female gender is a major criterion for the diagnosis of HCM, as an increased wall thickness is almost certainly a feature of disease in female athletes.

In much the same way, a case can be made for the family history of sudden cardiac death in the case of athletes with borderline hypertrophy. It is known that family history of sudden cardiac death is considered a major independent, albeit rather weak, predictor of sudden cardiac death in individuals diagnosed with HCM (9). In a recent study of a population of HCM patients, a family history of sudden cardiac death was positive in approximately 25% of those studied (10). As a clinical parameter associated with sudden cardiac death (SCD), a positive family history of SCD bears a positive predictive value of 28% and a negative predictive value of 88% (11). On the other hand, family history of sudden cardiac death in a healthy individual, (10), is a very rare finding. Thus, in the setting of a borderline cardiac hypertrophy, a positive family history is suggestive of cardiac disease. Still, as a diseased individual may often lack this characteristic, the sensitivity and specificity of such a criterion is low and it would be a weak stand-alone test for the diagnosis of HCM. The family history of sudden cardiac death can be termed a minor criterion for the differential diagnosis of HCM from athlete’s heart.

Conclusion:

Overall, Stefano Casseli et al from the Pelliccia group initialize a new era in the clinical differential diagnosis of HCM from athlete’s heart working not to add new parameters in the field but trying to make the distinction and compare the impact and clinical strength of each parameter. The authors are actually making a step forward towards a better algorithm (like major and minor criteria) for the differential diagnosis of HCM from athlete’s heart.