Previous chapters discussed how fixed obstructions to blood flowing through the heart can lead to significant morbidity and mortality. Aortic and mitral stenosis are two examples of lesions, which prevent the heart from effectively pumping blood. Hypertrophic obstructive cardiomyopathy (HOCM) represents a specific form of hypertrophic cardiomyopathy (HCM), which also manifests, at rest or with provocation (e.g., elevated heart rate, hypovolemia), with dynamic obstruction of left ventricular outflow tract (LVOT) (Figure 10–1). Dynamic outflow obstruction results in syncope, dyspnea, and, at times, sudden death. Although there is an increased incidence of sudden cardiac death (SCD) in the HCM patient with myocardial wall thickness greater than 30 mm or more, the majority of sudden deaths occur in HCM patients with myocardial wall thicknesses less than 30 mm.1 Consequently, all HCM patients should undergo SCD risk stratification at initial evaluation. The American College of Cardiology Foundation and the American Heart Association (ACCF/AHA) developed extensive guidelines for the evaluation and management of the HCM.
Although rare, cardiac tumors and other masses at times interfere with valve function, produce emboli, and dynamically obstruct blood flow through the heart. This chapter will examine these different conditions, which are nonetheless linked by their dynamic ability to prevent the heart from properly functioning.
The midesophageal long-axis view is presented here in outline form. As a consequence of the hypertrophied interventricular septum, flow patterns within the heart are altered such that the anterior leaflet of the mitral valve is drawn during ventricular systole into the LVOT producing obstruction. This is known as systolic anterior motion (SAM) of the mitral valve.
SIGNS, SYMPTOMS, AND DIAGNOSIS OF HCM
HCM is an autosomal dominant trait; roughly one-half of the patients have a blood relative afflicted with HCM.2,3 The disease can affect both males and females. It is estimated that HCM presents in 1:500 of the general adult population and that these patients are at increased risk for SCD.4 Certainly, many patients with HCM are not detected and can present with SCD as the first manifestation of their cardiac disease.
Symptoms of HCM include dyspnea, exercise intolerance, palpitations, syncope, chest pain, and SCD. HCM can manifest in both the left and the right heart; however, it is overwhelmingly a disease of the left ventricle. HCM can occur with and without LVOT obstruction.5 In nonobstructive HCM disease, patients develop a hypertrophied myocardium and diastolic dysfunction without generating high dynamic pressure gradients in the LVOT. As previously discussed in Chapter 2, diastolic dysfunction occurs when the heart is unable to normally accommodate diastolic filling at low pressures. Subsequently, impaired relaxation and ventricular compliance leads to an increased left ventricular end-diastolic pressure (LVEDP), elevated pulmonary arterial pressures (PAPs), increased pulmonary congestion, and decreased coronary perfusion pressure (CPP). Such patients can develop angina, ...