Significant regional heterogeneity of coronary flow reserve in paediatric hypertrophic cardiomyopathy

Previous studies have indicated that cardiac events in young patients with hypertrophic cardiomyopathy (HCM) are related to ischaemia rather than to a rrhythmia. We measured coronary flow reserve in paediatric HCM and compared the values with those in adult HCM. We studied 12 patients with HCM includ ing six paediatric (<20 years old; mean 13 years) and six adult patients (> 20 years old: mean 62 years), and six healthy young adults (mean 29 years) as controls. Every patient underwent magnetic resonance imaging (MRI) for a natomical assessment. Myocardial blood flow at rest and after dipyridamole infusion was measured with dynamic nitrogen-13 ammonia positron emission to mography (PET). Partial volume effect was corrected for using the anatomica l data obtained with MRI. In adult patients with HCM, coronary flow reserve in the hypertrophied septal region was not significantly different from th at in the non-hypertrophied lateral wall (1.38 +/- 0.29 vs 1.77 +/- 0.39, r espectively). In the paediatric patients, coronary Row reserve in the hyper trophied septal region was significantly lower than in the non-hypertrophie d lateral wall (0.84 +/- 0.33 vs 2.74 +/- 0.90, respectively, P < 0.01). In addition, coronary flow reserve in adult patients was lower than in contro l subjects both in the septal wall (1.38 +/- 0.29 vs 2.94 +/- 0.35, respect ively, P < 0.0001) and in the lateral wall (1.771 +/- 0.39 vs 2.85 +/- 0.69 , respectively, P < 0.05). In contrast, coronary flow reserve in paediatric patients was not significantly different from that in control subjects in the lateral wall (2.74 +/- 0.90 vs 2.85 +/- 0.69, respectively), while abso lute reduction of myocardial blood flow was noted after pharmacological vas odilatation in the hypertrophied septal region. In conclusion, significant regional differences of coronary flow reserve were present in the paediatri c patients with HCM. These results suggest that paediatric patients with HC M intrinsically have the potential to experience significant regional ischa emia even in the absence of coronary stenosis.