ESSENTIALS OF CLINICAL DIAGNOSIS
Note: Not all criteria are needed for diagnosis of hypertrophic cardiomyopathy.
Asymmetric hypertrophied nondilated ventricle with septal to posterior wall end-diastolic thickness ratio > 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 systolic anterior motion with varying degree of mitral regurgitation.
Midsystolic aortic valve closure.
Impaired diastolic function with decrease in tissue Doppler (early diastolic velocity [e’]) and longitudinal strain.
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) > 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).
Table 23–1.Differential Diagnosis of Left Ventricular Hypertrophy |Favorite Table|Download (.pdf) Table 23–1. Differential Diagnosis of Left Ventricular Hypertrophy
Supravalvular aortic stenosis
Right ventricular hypertrophy
Glycogen storage disease (PRKAG2 cardiomyopathy, Danon disease, Pompe disease)
Mucopolysaccharide storage disease
Echocardiogram parasternal long-axis view in diastole showing asymmetric septal hypertrophy (white arrow) compared to the inferolateral wall.
HCM is relatively common (1 in 500) in the general population with about 750,000 people affected in the United States. Although it is the most common cause of sudden death in the young (< 35 years old) in North America, most people afflicted with HCM 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 HCM can take many paths: sudden cardiac death, symptomatic HCM heart failure, end-stage cardiomyopathy, atrial fibrillation, and stroke. However, if intervened upon in a timely manner, HCM can potentially have no effect on normal longevity.
B. Genetics & Histopathology
The genetics of HCM involve an autosomal dominant pattern of inheritance, with 60–70% of patients having an affected family member. HCM is more common in males than females. Offspring of affected individuals have a 50% chance of inheriting mutations and risk of disease. Common genes affected include β-myosin heavy chain, myosin binding protein C, troponin I, and troponin T, but numerous others have been described. Approximately 70% of genotyped patients have mutations involving β-myosin heavy chain or myosin binding protein C. The genetic basis of ventricular hypertrophy does not always correlate with prognosis. Patients with tropomyosin mutations have only a mild ...