REVIEW ARTICLE Thirty Controversies and Considerations in Hypertrophic Cardiomyopathy Ahmad Masri, MD MS, Babak Nazer, MD, Lana Al-Rashdan, MD, Meghan M. Mannello, MS, Katherine L. Fischer, MSN RN, Reyhaneh Akhavein, MD, Punag Divanji, MD, Howard K. Song, MD PhD, and Stephen B. Heitner, MD The Hypertrophic Cardiomyopathy Center at the Knight Cardiovascular Institute, Department of Medicine, Oregon Health & Science University, Portland, OR, USA ABSTRACT More than 60 years after the first description of “asymmetric septal hypertrophy of the heart,” hypertrophic cardiomyopathy (HCM) as a disease has continued to provide clinicians and researchers fertile grounds for debate and investigation. HCM, as a complex disease requiring a multidisciplinary approach, runs the gamut of all we learned in medical school and beyond – physiology, clinical medicine, genetics, imaging, diagnostics, pharmacotherapies, electrophysiology, interventional cardiology, and cardiothoracic surgical interventions. In this review, we discuss 30 contemporary controversies and considerations in HCM. Abbreviations: HCM: hypertrophic cardiomyopathy; LVH: left ventricular hypertrophy; nHCM: non-obstructive hypertrophic cardiomyo- pathy; oHCM: obstructive hypertrophic cardiomyopathy; LVOTO: left ventricular outflow tract obstruction; MVA: mitral valve apparatus; P: phenotype; G: genotype; MYH7: myosin heavy chain 7; MYPBC3: myosin binding protein C, cardiac type; ECG: electrocardiogram; SCD: sudden cardiac death; MR: mitral regurgitation; LA: left atrium; AF: atrial fibrillation; CMR: cardiac magnetic resonance imaging; LGE: late gadolinium enhancement; ICD: implantable cardioverter-defibrillator; ECV: extracellular volume; CPET: cardio-pulmonary exercise testing; SRT: septal reduction therapy; FDR: first-degree relative; NYHA: New York Heart Association; DOAC: direct oral anticoagulants; OAC: oral anticoagulants; AAD: anti-arrhythmic drugs; NSVT: non-sustained ventricular tachycardia; ACC: American College of Cardiology; AHA: American Heart Association; ESC: European Society of Cardiology; LVEF: left ventricular ejection fraction; S-ICD: subcutaneous implantable cardioverter-defibrillator; IAS: inappropriate shock; AVB: atrio-ventricular block; CHB: complete heart block; VT: ventricular tachycardia; ASA: alcohol septal ablation; ATP: anti-tachycardia pacing; TE: thromboembolism; SAM: systolic anterior motion; LBBB: left bundle branch block. ARTICLE HISTORY Received 21 May 2020; Revised 1 October 2020; Accepted 13 October 2020 KEYWORDS Hypertrophic cardiomyopathy; myectomy; alcohol septal ablation; sudden cardiac death; imaging Introduction Hypertrophic cardiomyopathy (HCM) is the most common car- diomyopathy, defined morphologically as unexplained left ventri- cular hypertrophy (LVH) in a non-dilated ventricle. It is phenotypically heterogeneous with a variety of implicated genetic mutations, morphologies, and hemodynamic profiles. HCM is divided into two broad phenotypes; either obstructive (oHCM), through the demonstration of either resting or provoked left ventricular outflow tract obstruction (LVOTO); or non- obstructive (nHCM), with the absence of LVOTO at rest or with exercise. 1–3 Irrespective of the hemodynamic phenotype, careful work in this arena has yielded growing evidence of a common underlying biomechanical abnormality: HCM-causing sarcomeric gene variants destabilize the low-energy super-relaxed state of cardiac myosin and promote excessive cross-bridging with actin. 4,5 This subsequently results in clinical evidence of hyper- contractility, disordered relaxation, and reduced ventricular distensibility. 6 Another overlapping phenotype relates to anato- mical variants of the mitral valve apparatus (MVA) which, under the right circumstances, precipitate LVOTO even in the absence of significant hypertrophy. 7,8 HCM is a complex disease that requires a multidisciplinary team approach. HCM is a mature field with more than 60 years of active research that defined the mechanisms, natural history, and outcomes of the disease; Figure 1. In a prior review, we addressed the future of HCM and what it holds. 9 In this review, we utilize a practical approach to discussing current controversies and considerations in HCM in adults, spanning clinical evaluation, genetics, imaging, diagnostics, medical therapy, and electrophy- siological, percutaneous catheter, and surgical interventions; Figure 2. These controversies and considerations include those with either evidence or lore that results in diverging clinical practices, and those whereby clinical practice has limited scien- tific evidence. We conclude by emphasizing the ultimate goal of continued research in HCM: improving the quality of life and longevity of people living with HCM. Discussion Clinical evaluation of HCM Education, widespread use of diagnostic imaging, and advancement in genetics over the last 30 years have tre- mendously improved the timeliness, accuracy, and overall rate of HCM diagnosis. Patient advocacy groups such as the Hypertrophic Cardiomyopathy Association played a pivotal role in educating physicians and patients in the multi- CONTACT Ahmad Masri [email protected] Oregon Health & Science University, Dept. of Medicine, UHN-62, 3181 SW Sam Jackson Rd, Portland, OR 97239, USA. STRUCTURAL HEART 2021, VOL. 5, NO. 1, 39–54 https://doi.org/10.1080/24748706.2020.1844926 © 2020 Cardiovascular Research Foundation
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