Morphologic and functional characteristics of the heart in Friedreich's ataxia

Abstract

The purpose of this study was to characterize the heart in patients with Friedreich's ataxia by two-dimensional echocardiography, systolic time intervals, and heart biopsy. Ten patients with Friedreich's ataxia (seven females and three males, age 15 +/- 7 years) were compared with 10 age-matched normal subjects (five males and five females, age 16 +/- 7 years). The mean systolic blood pressure in the patients with Friedreich's ataxia was lower (114 +/- 9 mm Hg) than that in the control subjects (122 +/- 8 mm Hg; p less than 0.05); diastolic blood pressures were the same. The heart rate in the patients with Friedreich's ataxia (102 +/- 17 beats/minute) was greater than that in the control subjects (76 +/- 12 beats/minute; p less than 0.001). The interventricular septal wall thickness was much greater in Friedreich's ataxia (13 +/- 2 versus 8 +/- 1 mm, p less than 0.001) as was the posterior wall thickness (13 +/- 3 versus 8 +/- 1 mm, p less than 0.001). The left ventricular end-diastolic diameter was smaller in Friedreich's ataxia (35 +/- 6 mm versus 47 +/- 6 mm; p less than 0.01), and the fractional change of the left ventricular minor axis with systole was greater in Friedreich's ataxia (40 +/- 9 percent versus 33 +/- 5 percent; p less than 0.05). An 11th patient with Friedreich's ataxia (age 33) had clinical heart failure, but his course was complicated by alcohol abuse. Heart biopsy in three patients with Friedreich's ataxia demonstrated myocyte hypertrophy (21.5 +/- 2.0 microns diameter; normal, 14 to 17 microns) and increased fibrosis (16 +/- 9 percent; normal, less than 5 percent). Thus, heart disease in Friedreich's ataxia is characterized by myocyte hypertrophy, interstitial fibrosis, increased left ventricular wall thickness, decreased left ventricular cavity size, sinus tachycardia, and normal systolic function. Further biochemical analysis of tissues may lead to the link of the neurologic and cardiac diseases and eventually to more effective therapy of this condition.