Skeletal muscle proton T 2 in chronic heart failure

To evaluate the interest of proton T 2 measurement of skeletal muscle at rest and with exercise in patients with chronic heart failure, we performed associated measurements of proton T 2 using magnetic resonance imaging, of external work using ergometry, and of intra-cellular pH (pH) using magnetic resonance 31 P-spectroscopy, in skeletal muscle of the leg anterior compartment, in 37 patients with chronic heart failure. Sixteen patients were in New York Heart Association class II (NYHA II, moderate cardiac failure) and 21 in NYHA classes III-IV (severe cardiac failure). Rest T 2 was significantly increased in NYHA III-IV patients (30.9 ± 2.2 versus 32.8 ± 209 ms, p < 0.01). For these very different work levels, T 2 variations in both groups were of 23 ± 8 versus 21 ± 9, p =3D NS and pHi variations were of -8 ± 4 versus -9 ± 5%, p =3D NS. The ratio of relative T 2 variations to W was significantly increased in NYPH III-IV patients (0.24 ± 0.12 versus 0.60 ± 0.41%/J, p < 0.02). Variations of T 2 and of pHi with exercise were coupled with external work, only in group NYHA II. T 2 variations negatively correlated with those of pHi in both groups (r=3D -0.78, p<0.01 in NYHA II patients and r=3D -0.60, p<0.01 in NYHA III-IV patients). In conclusion, rest T 2 of skeletal muscle, as well as exercise-related proton T 2 variation as a function of work level, allow to evaluate the degree of severity of heart failure. A coupling is obtained between T 2 and pHi variations with exercise which seems to depend on the exercise intensity level. (authors). 22 refs., 3 figs., 2 tabs