Leng Jiang

　　Hypertrophic Cardiomyopathy (HCM) was only reported as scattered cases by autopsy，open heart surgery and ventriculogram 50 years ago; the decisive contribution of echocardiography has opened a new era after the HCM’s “B.C. period”. There have been evolving opinions and debates generated by the disease over the past 50 years. It is now well demonstrated that HCM has remarkable diversity in the pattern and extent of left ventricular hypertrophy (LVH)， the presence， location and degree of obstruction， the disease course， the risk for sudden cardiac death (SCD)， as well as the age of onset of the disease.
　　HCM is now recognized as the most common inherited heart disease. Across multiple geographies and ethnicities， the prevalence of HCM is approximately one in 500. Yet， many cardiologists might see only one or two new cases of HCM a year. In 2011， the American Society of Echocardiography published Clinical “Recommendations for Multimodality Cardiovascular Imaging of Patients with HCM”， which was endorsed by the American Society of Nuclear Cardiology， Society for Cardiovascular Magnetic Resonance， and Society of Cardiovascular Computed Tomography; and the ACC and the AHA unveiled the first guidelines for the diagnosis and treatment of HCM. Although the lack of high levels of evidence regarding HCM provided by clinical trials， a guideline document based on expert consensus that outlines the most important diagnostic and management strategies is helpful.
　　The natural history of HCM is benign in the majority of patients， with a near normal life span. However， adverse outcomes， including sudden cardiac death， lifestyle-limiting symptoms secondary to dynamic LVOT obstruction and/or diastolic filling abnormalities， atrial fibrillation， and LV systolic dysfunction， do occur in some patients. Indeed， HCM is a leading cause of nonviolent sudden death in competitive athletes and young individuals in the United States. Therefore， diagnosis of the disease and further risk-stratification are very important.
　　A large proportion of HCM patients are asymptomatic， the clinical diagnosis is typically made with cardiac imaging， most commonly with 2-D echocardiography (Echo) based on the presence of a hypertrophied and nondilated left ventricle. There are various imaging modalities available now， which can be used to assess cardiac morphology of HCM and to guide treatment， screening and preclinical diagnosis and to detect phenocopies. By incorporating the available data and utilizing “cost-awareness” and “risk-benefit analysis”， the guidelines recommend transthoracic Echo be used in the initial evaluation of all patients suspected of HCM， and also for family members in some cases (class I， level B).
　　The diagnosis of HCM is based on the demonstration of LVH (wall thickness ≥ 15 mm) in the absence of other disease process that can reasonably account for the magnitude of hypertrophy present. Thus， many clinical conditions need to be differentiated， such as hypertensive heart disease， discrete hypertrophy in some elderly， athlete’s Heart， Fabry disease， Freiderich’s ataxia， and amyroidosis. The pattern of LVH can be helpful， since HCM produces asymmetric hypertrophy in most cases， while the other conditions produce concentric hypertrophy. But concentric LVH pattern does occur in HCM patients. Dynamic LV outflow tract (LVOT) obstruction is an important feature for HCM， which can impact on the prognosis and interventional strategy; but non-obstructive pattern is not uncommon in HCM. Doppler Echocardiography is the imaging modality of choice to assess the hemodynamics of dynamic obstruction. In symptomatic patients with LVOT gradients < 30 mm Hg at rest， it is recommended to perform gradient- provoked tests by Valsalva maneuver， amyl nitrite， and if possible with exercise (preferably treadmill exercise). LV systolic and diastolic dysfunction， even subclinical， can now be assessed by tissue Doppler and 2D speckle imaging for risk stratification.  The guidelines also recommend periodic echo screening for children of HCM patients， starting by age 12 or earlier and especially if they are engaging in competitive sports (class I， level C). Periodic echo exams of HCM patients can be useful every one to two years (class IIa， level C) and exercise treadmill can be used to determine functional capacity (class IIa， level C).
　　CMR may be considered in more challenging clinical scenarios， as in patients with suboptimal echo images. It can also provide additional information to characterize LV morphology (especially atypical apical or other localized hypertrophy)， therefore， facilitate the diagnosis. CMR imaging has received class I recommendation when transthoracic echo is inconclusive (level B) and to glean additional information that might influence patient management， such as late gadolinium enhancement which is thought to represent myocardial scar (level B). CT imaging may be useful in some patients with chest pain to determine the presence or extent of coronary artery disease， as well as SPECT or PET imaging (class I and II， all level of evidence C).
　　The detailed discussion of state of the art cardiac imaging for HCM will be presented at 0:45-11:00 May 25， during the cardiovascular imaging forum at 3H-J Hall(3F)， and the contemporary management for HCM will be discussed at 16:00-16:20 May 25 during structural heart disease at Yangtze Hall (F5)， with case illustration.