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INTRODUCTION

ESSENTIALS OF DIAGNOSIS

Note: Not all criteria are needed for the diagnosis of hypertrophic cardiomyopathy.

  • Asymmetric hypertrophied nondilated ventricle with septal to posterior wall end-diastolic thickness ratio more than 1.3 not explained by other etiologies.

  • Ejection murmur that increases with Valsalva with or without concomitant mitral regurgitation murmur and preserved aortic second sound.

  • Increased gradients causing obstruction across left ventricular outflow tract and/or mid ventricle with characteristic late peaking “dagger”-shaped Doppler velocity profile.

  • Mitral valve apparatus structural abnormalities and systolic anterior motion with varying degree of mitral regurgitation.

  • Midsystolic aortic valve closure.

  • Impaired diastolic function with decrease in tissue Doppler peak early diastolic velocity (e′) and global longitudinal strain.

GENERAL CONSIDERATIONS

A. Definition & Prevalence

Hypertrophic cardiomyopathy (HCM) is a disorder of the myocardium caused by mutations of the sarcomere or sarcomere-associated proteins. It was first brought to attention by the British forensic pathologist Donald Teare in 1958 as a disease manifesting with symmetric or asymmetric left ventricular hypertrophy (LVH) more than 1.5 cm (Figure 23–1) in a nondilated ventricle. Additional observations made by him were myocardial clefts and myocyte disarray seen along with hypertrophy in hearts of young and healthy adults who experienced sudden death. Subsequently, pioneering work by Eugene Braunwald has defined the hemodynamics of the disease process as we know it now. The distribution of hypertrophy is variable, can involve the right ventricle, and is not explained by other causes of LVH (see Table 23–1 for differential diagnosis of LVH).

Figure 23–1.

Echocardiogram parasternal long-axis view in diastole showing asymmetric septal hypertrophy (white arrow) compared to the inferolateral wall.

Table 23–1.Differential Diagnosis of Left Ventricular Hypertrophy

HCM is relatively common (1:200–1:500) in the general population with about 750,000 people affected in the United States and 15–20 million worldwide. However, only 15–20% of HCM is identified clinically which clearly highlights a troubling reality given that it is the most common cause of sudden cardiac death in individuals less than 35 years of age in North America. On a positive note, most people afflicted with HCM do live a normal life. HCM patients may live well into their sixth to eighth decades, with patients older than age 90 with HCM being reported. Moreover, the first clinical recognition of HCM may occur when patients are in their sixth to eighth decade of life; usually, these patients have milder forms of the disease with the most serious complications being uncommon after age 60. The natural history of ...

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