Several clinical and echocardiographic studies describe morphological and functional findings in patients with hypertrophic cardiomyopathy. Less is known regarding morphological and functional characteristics of the left ventricular hypertrophy found in the setting of the Noonan and LEOPARD syndromes.

To compare non-invasively the morphological and functional findings potentially affecting symptoms and clinical outcome in children with hypertrophic cardiomyopathy as opposed to Noonan and LEOPARD syndromes.

We studied by echo-Doppler 62 children with left ventricular hypertrophy, dividing them into two subgroups matched for age and body surface area. The first group, of 45 patients with a mean age of 7.5 ± 5.2 years and body surface area of 0.9 ± 0.44 mq, had idiopathic hypertrophic cardiomyopathy. The second group, of 17 patients, all had left ventricular hypertrophy in the setting of Noonan or LEOPARD syndromes. Their mean age was 6.6 ± 5 years, and body surface area was 0.8 ± 0.36 mq. In all patients, we assessed the left ventricular maximal mural thickness, expressed as a Z-score, along with any obstructions in the left and right ventricular outflow tracts. In addition, to define left ventricular diastolic function, we used mitral flow and pulsed Tissue Doppler to record the Ea, Aa, Ea/Aa, E/Ea indexes in the apical 4-chamber view at the lateral corner of the mitral annulus. We also measured the diameters of the coronary arteries in the diastolic frame.

Compared to those with hypertrophic cardiomyopathy, those with syndromic left ventricular hypertrophy showed a significantly increased Z-score for mural thickness, and a higher prevalence of obstruction in the left ventricular outflow tract. In addition, the patients with Noonan or LEOPARD syndromes showed a significantly decrease of Ea and increase of Aa, with a decreased Ea/Aa ratio, all suggestive of left ventricular abnormal relaxation. Moreover, the E/Ea ratio was significantly increased in these patients. The presence of right ventricular hypertrophy, mainly associated with dynamic obstruction in the outflow tract, was detected in only 5 of the 17 patients with Noonan or LEOPARD syndromes, as was dilation of the coronary arteries.

Compared to children with hypertrophic cardiomyopathy, those with left ventricular hypertrophy in the setting of Noonan or LEOPARD syndromes show more ventricular hypertrophy and diastolic dysfunction, due to both abnormal relaxation and reduced compliance. They also exhibit an increased prevalence of obstruction of the left ventricular outflow tract, along with dynamic obstruction of the right ventricular outflow tract and dilated coronary arteries. These morphological and functional findings could explain the different symptoms and clinical events, and potentially define the more appropriate therapeutic options in children with left ventricular hypertrophy of different aetiology.