The 50-Year History, Controversy, and Clinical Implications of Left Ventricular Outflow Tract Obstruction in Hypertrophic Cardiomyopathy From Idiopathic Hypertrophic Subaortic Stenosis to Hypertrophic Cardiomyopathy

Hypertrophic Cardiomyopathy Center, Minneapolis Heart Institute Foundation, Minneapolis, Minnesota 55407, USA.
Journal of the American College of Cardiology (Impact Factor: 15.34). 08/2009; 54(3):191-200. DOI: 10.1016/j.jacc.2008.11.069
Source: PubMed

ABSTRACT Dynamic obstruction to left ventricular (LV) outflow was recognized from the earliest (50 years ago) clinical descriptions of hypertrophic cardiomyopathy (HCM) and has proved to be a complex phenomenon unique in many respects, as well as arguably the most visible and well-known pathophysiologic component of this heterogeneous disease. Over the past 5 decades, the clinical significance attributable to dynamic LV outflow tract gradients in HCM has triggered a periodic and instructive debate. Nevertheless, only recently has evidence emerged from observational analyses in large patient cohorts that unequivocally supports subaortic pressure gradients (and obstruction) both as true impedance to LV outflow and independent determinants of disabling exertional symptoms and cardiovascular mortality. Furthermore, abolition of subaortic gradients by surgical myectomy (or percutaneous alcohol septal ablation) results in profound and consistent symptomatic benefit and restoration of quality of life, with myectomy providing a long-term survival similar to that observed in the general population. These findings resolve the long-festering controversy over the existence of obstruction in HCM and whether outflow gradients are clinically important elements of this complex disease. These data also underscore the important principle, particularly relevant to clinical practice, that heart failure due to LV outflow obstruction in HCM is mechanically reversible and amenable to invasive septal reduction therapy. Finally, the recent observation that the vast majority of patients with HCM have the propensity to develop outflow obstruction (either at rest or with exercise) underscores a return to the characterization of HCM in 1960 as a predominantly obstructive disease.

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    ABSTRACT: Hypertrophic cardiomyopathy (HCM) is a complex, yet relatively common genetic cardiac disease and has been the subject of intensive investigation since its first description in 1958. HCM is defined by the presence of an increased left ventricular wall thickness that is not solely explained by abnormal loading conditions. Histologically, HCM is characterised as left ventricular hypertrophy due to an abnormally hypertrophied muscular structure of predominantly the septum (‘myocardial fibre disarray’) [1]. Approximately 30 % of patients with HCM develop left ventricular outflow tract (LVOT) obstruction under resting conditions [2–4]. By convention, LVOT obstruction is defined as an instantaneous peak Doppler LVOT gradient of > 30 mmHg at rest or during physiological provocation. A gradient of > 50 mmHg is usually considered to be the threshold at which LVOT obstruction becomes haemodynamically significant.Pharmacological therapy using negative inotropic agents (non-vasodilating beta-block ...
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