Increased Cardiac Muscle Fiber Size and Reduced Cell Number in Down Syndrome: Heart Muscle Cell Number in Down Syndrome

Abstract

The size of cardiac muscle fibers was determined for 15 patients with Down syndrome who did not have congenital heart disease and for 15 age- and sex-matched control patients by counting the number of cardiac muscle cells in specified areas of microscopic sections (method of Black-Schaffer and Turner). Mean ratio of muscle cells per unit area for the Down patients versus controls was 84.9%, with mean cross-sectional area of Down fibers 117.8% of control value and calculated mean volume of Down cells 127.7% of control value. Mean weights of Down hearts related to normal for age, versus control hearts, was 79.8% of control values. Calculated ratio of total cardiac muscle cell number in Down hearts was 62.5% of the value for controls. This value corresponds closely to the 62.4%, which can be calculated from Naeye's data on cardiac muscle fiber size in Down syndrome based on a point-count method, and is also close to published values for liver cell size and number and skeletal muscle nuclear number in Down syndrome. This study demonstrates that the Black-Schaffer and Turner method gives results equivalent to those of the point-count method for studies of cardiac muscle fiber size, and further supports the suggestion that chromosome 21 controls the size and number of at least certain cell types.

‘The sedentary heart’: Physical inactivity is associated with cardiac atrophy in adults with an intellectual disability

“…Abnormal gene regulation and reduced cardiac cell number are found in DS [25]. However, diastolic dysfunction was also demonstrated in subjects without DS, disproving a syndromic feature.…”

Evaluation of Left Ventricle Systolic and Diastolic Functions by Tissue Doppler Echocardiography in Children with Down Syndrome

“…Both these ratios were lower than those of normal subjects in other reports that found a similar difference (21,22). This weakened rightsided diastolic performance may be due to defective cardiac autonomic performance, cardiac hypertrophy by inhibited calcineurin signaling, or cardiac muscle fiber dysfunction (13,(26)(27)(28)(29)(30). Pulmonary hypertension is considered one of the most common complications in children with Down syndrome even without the presence of any structural heart defects 4…”

How Normal Is a ‘Normal' Heart in Fetuses and Infants with Down Syndrome?

“…Tricuspid valve regurgitation has been suggested as a useful feature for detection of fetuses with DS [7,][8]. The increased prevalence of tricuspid valve regurgitation is considered to be related to the structural changes associated with DS: decreased number of myocytes, abnormal orientation of myocytes and myofibrils and abnormal connective tissue [31]. The observed dysplastic, plump AV valves in fetal hearts with DS confirm an abnormal development of the AV valves in patients with DS.…”