Dual-single photon emission computed tomography and contrast-enhanced magnetic resonance imaging to evaluate dissimilar features of apical hypertrophic cardiomyopathy.

Apical hypertrophic cardiomyopathy (HCM) is an uncommon variant of HCM characterized by hypertrophy located in the left ventricular apex that occurs at a rate of about 30% in the Japanese population. Although the prognosis of most patients with apical HCM is relatively benign, it can be poor if apical left ventricular aneurysms develop. However, the mechanism of aneurysmal formation is unclear. We describe two patients with apical HCM and dissimilar findings in 201Thallous chloride ((201)TlCl) and (123)I-betamethyl-p-iodophenyl-pentadecanoic acid ((123)I-BMIPP) dual single-photon emission computed tomography (dual-SPECT), but no myocardial fibrosis on contrast-enhanced magnetic resonance images (MRI). One had apparently normal myocardial perfusion and metabolism, whereas the other had exercise-induced myocardial ischemia and impaired myocardial metabolism. These findings indicated that even apical HCM without myocardial fibrosis is pathophysiologically heterogeneous. Apical HCM has been evaluated by either dual-SPECT or cardiac MRI, but not by both. Thus, a combination of imaging modalities is apparently essential for elucidating the pathophysiology of apical HCM. These dissimilar findings in dual-SPECT might be important in identifying patients with apical HCM who are at high risk of forming aneurysms.