Concentric hypertrophic cardiomyopathy

Concentric or symmetric hypertrophic cardiomyopathy is a morphological variant or phenotype of hypertrophic cardiomyopathy (HCM) characterized by fairly symmetrical or diffuse thickening of the myocardium and a reduction of the left ventricular cavity.

Terminology

The term ‘concentric left ventricular hypertrophy’ might be more appropriate in the context of a known or possible secondary cause as hypertensive heart disease, aortic stenosis athletes heart syndrome or infiltrative disease etc.

Epidemiology

Statements on the frequency of concentric hypertrophic cardiomyopathy are quite variable among studies and range from about 5-10% ^1-4 to 42% ^5-7. This variability might be a result of including secondary causes of left ventricular hypertrophy as cardiac amyloidosis, Fabry disease or sarcoidosis etc.

Associations

Concentric hypertrophic cardiomyopathy might be also associated with left ventricular outflow obstruction ⁵.

Pathology

In concentric hypertrophic cardiomyopathy, myocardial wall thickness is increased in a fairly symmetrical and circumferential fashion and the left ventricular cavity is decreased.

A wall thickness of ≥15 mm in adults or a z-score of ≥2 in children is considered diagnostic ¹.

Microscopic appearance

Microscopically hypertrophic cardiomyopathy is characterized by the following features ^4-6:

• cardiomyocyte hypertrophy: transverse diameter exceeding 40µm
• cardiomyocyte fiber disarray: disordered myocyte bundles/contractile elements within sarcomeres
• interstitial fibrosis or replacement fibrosis
• bizarre enlarged nuclei with nuclear hyperchromasia and pleomorphism

Radiographic features

Concentric hypertrophic cardiomyopathy is characterized by a circumferential fairly symmetrically increased myocardial wall thickness (≥15 mm) without significant differences between the walls or segments ⁵.

Echocardiography

Echocardiography can visualize symmetric hypertrophy and can provide additional information on cardiac function including cardiac strain. Besides echocardiography allows assessment of diastolic dysfunction and detect abnormal filling patterns ⁵.

MRI

Cardiac MRI can demonstrate symmetric left ventricular hypertrophy and can assess cardiac function including cardiac volumes and cardiac strain. It can provide additional prognostic information by demonstrating myocardial fibrosis and detect potential secondary causes of left ventricular hypertrophy ^1,5-7.

• cine imaging
  • concentric left ventricular wall thickening during diastole
  • decreased left ventricular cavity
  • increased mass and increased left ventricular ejection fraction
• cardiac strain imaging: decreased global longitudinal strain 
• cardiac tissue characterization
  • T1 mapping: increased native T1 values
  • ECV: increased
• IRGE/PSIR:
  • focal intramyocardial non-ischemic, fan-shaped or patchy late gadolinium enhancement
  • often visible at the right ventricular insertion sites (hinge points)
  • indicating replacement fibrosis or myocardial scarring

Radiology report

The radiological report should include a description of the following ⁵:

• location and extent of hypertrophic wall segments
• cardiac volumes and measurements including left ventricular mass
• cardiac wall motion abnormalities
• mitral annular plane systolic excursion (MAPSE) 
• signs of diastolic dysfunction
• presence of myocardial crypts
• signs of myocardial fibrosis, myocardial scarring or myocardial fiber disarray
• left ventricular outflow obstruction
• systolic anterior movement (SAM) of the mitral valve
• findings indicating secondary causes of left ventricular hypertrophy

Differential diagnosis

Clinical conditions that also might present with concentric left ventricular hypertrophy include the following ^1-7:

• cardiac amyloidosis
  • altered blood pool kinetics
  • atrial wall hypertrophy and/or papillary muscle thickening
  • much higher native T1 and ECV 
• cardiac sarcoidosis
  • patchy T2 hyperintensity
  • subepicardial late gadolinium enhancement 
• Anderson-Fabry disease
  • decreased native T1 
  • mid-wall inferolateral basal late gadolinium enhancement 
• Danon disease
• hypertensive heart disease
  • difficult to differentiate
  • normal or reduced ejection fraction 
• athlete heart syndrome: no reduction of the left ventricular cavity
• aortic stenosis: systolic jet in the aortic root

In addition concentric, it should be distinguished from other hypertrophic phenotypes including:

• asymmetric hypertrophic cardiomyopathy
• midventricular hypertrophic cardiomyopathy
• apical hypertrophic cardiomyopathy (Yamaguchi syndrome)
• mass-like hypertrophic cardiomyopathy