Assessing muscle vasodilation using near-infrared spectroscopy in cardiac patients.
BACKGROUND
In patients with chronic heart failure, an inadequate increase in muscle blood flow resulting from impaired vasodilation plays a key role in their exercise intolerance. However, no non-invasive methods to assess muscle vasodilation during dynamic exercise were available. We investigated whether the changes in tissue hemoglobin and myoglobin content (total-Hb + Mb) determined by non-invasive measurement using near-infrared spectroscopy (NIRS) reflect vessel conductance of working muscle during exercise.


RESULTS
Sixteen patients (10 patients with normal cardiac systolic function, 6 with cardiac dysfunction) performed incremental bicycle exercise testing. Total-Hb + Mb from the right vastus lateralis muscle was monitored using NIRS. Leg blood flow (LBF) in the right femoral vein was measured using a thermodilution technique every 30-60 s. Leg vessel conductance was calculated as LBF/mean arterial pressure at each time of the measurement. In all cases except 1, the levels of total-Hb + Mb showed significant correlation with the leg vessel conductance (r=0.792 to 0.980). Intra-subject reproducibility of the NIRS measurement was also confirmed in 6 patients.


CONCLUSIONS
Total-Hb + Mb from NIRS reflected muscle vasodilation during sub-maximal dynamic exercise in patients with and without cardiac dysfunction, indicating that NIRS provides a valuable method to assess the working muscle vasodilation.
Watanabe
Shigeyuki
S
Cardiovascular Division, Department of Internal Medicine, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Japan. s-watana@md.tsukuba.ac.jp
Ishii
Chikako
C
Takeyasu
Noriyuki
N
Ajisaka
Ryuichi
R
Nishina
Hidetaka
H
Morimoto
Takafumi
T
Sakamoto
Kazuhiko
K
Eda
Kazuhiko
K
Ishiyama
Miki
M
Saito
Takumi
T
Aihara
Hideaki
H
Arai
Emi
E
Toyama
Masahiro
M
Shintomi
Yoshitaka
Y
Yamaguchi
Iwao
I
D000328:Adult; D000368:Aged; D000787:Angina Pectoris / Q000503:physiopathology*; D001281:Atrial Fibrillation; D001794:Blood Pressure; D016022:Case-Control Studies; D005080:Exercise Test; D005268:Femoral Vein / Q000503:physiopathology; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D007866:Leg / Q000098:blood supply*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply*; D009211:Myoglobin / Q000032:analysis; D019265:Spectroscopy, Near-Infrared / Q000295:instrumentation / Q000379:methods; D014664:Vasodilation
D006454:Hemoglobins; D009211:Myoglobin