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

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 data1 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 number1,2 and skeletal muscle nuclear number2 in Do...