LAUSR

Circulation. 2019;140:344–346. DOI: 10.1161/CIRCULATIONAHA.119.040129 344 A lthough certain histopathologic findings (myocyte hypertrophy, disarray, interstitial fibrosis, and coronary artery dysplasia) are characteristic of hypertrophic cardiomyopathy (HCM)1, clinical recognition of phenocopies that masquerade clinically as HCM, despite multimodality cardiac imaging, can often be challenging. Also, dynamic left ventricular outflow tract obstruction (LVOTO), the clinical hallmark of obstructive HCM, can occasionally be seen in other disorders like hypertensive heart disease (HHD), storage diseases (Fabry disease), and, occasionally, infiltrative disorders like amyloidosis.2–4 Regardless of the underlying etiology, surgical myectomy (SM) is a very effective therapy for relief of dynamic LVOTO.5 In the current study of patients with clinically diagnosed HCM and severe dynamic LVOTO who underwent SM, we sought to study the frequency of various histopathologic diagnoses, besides HCM, on the postsurgical myocardial specimen. This was an observational study of 2472 consecutive adult patients aged ≥18 years (56±14 years, 54% men, excluding 63 patients with subaortic membrane) with advanced symptoms related to severe dynamic LVOTO who underwent SM at our tertiary center between January 2002 and March 2018. Baseline clinical and imaging data (including resting and provokable LVOT gradients on transthoracic echocardiography) were recorded. After a thorough clinical and imaging evaluation, all patients were clinically diagnosed with HCM by experienced cardiologists. Before surgery, there was no suspicion of an alternate diagnosis besides HCM. All SM specimens were subsequently evaluated by dedicated cardiac pathologists, and a diagnosis of HCM was made based on a combination of factors including myocyte disarray, myocyte hypertrophy, small coronary arteriole dysplasia, interstitial fibrosis, and endocardial fibroelastosis. SM specimens were sampled by submitting 1 cassette composed of multiple fragments of tissue to make 1 paraffin block per 5 g of tissue. The current study was approved by the institutional review board with a waiver of individual informed consent. The breakdown of findings on surgical pathology were as follows: (1) histopathologically confirmed HCM (n=2108, 82%); (2) HHD (in the absence of HCM features, n=280, 11%); (3) storage diseases, including Fabry disease (presence of dense concentric lamellar bodies on electron microscopy, n=33, 1.3%); (4) concomitant myocarditis (based on Dallas criteria) with histopathologically confirmed HCM (n=123, 5%); and (5) cardiac amyloidosis (using standard criteria including Congo red staining, n=18, 1%). The Table shows baseline clinical and imaging data. Genotype data were not uniformly available. Patients with true HCM had a higher frequency of family history, whereas the HHD and amyloid groups were significantly older, with a higher proportion of hypertension and coronary artery disease. There were no significant differences in basal septal thickness and LVOT gradients between different groups. There were 7 (0.3%) Alaa Alashi, MD Ria M. Desai Tamanna Khullar, MD Kevin Hodges, MD E. Rene Rodriguez, MD Carmela Tan, MD Zoran B. Popovic, MD, PhD Maran Thamilarasan, MD Per Wierup, MD, PhD Harry M. Lever, MD Nicholas G. Smedira, MD Milind Y. Desai, MD