Purpose: Reduced peak aerobic capacity in chronic heart failure can be partly explained by impaired peripheral factors. However, skeletal muscle deoxygenation responses during exercise and their relationship to peak aerobic capacity have not been fully established in early post-myocardial infarction (MI) patients.
Methods: Patients early post-MI (age 61 +/- 9, n=16, 21 +/- 8 days after the first MI) and age-, height-, and weight-matched control participants (age 61 +/- 9, n=18) performed ramp cycling exercise until exhaustion. Near infrared spectroscopy at the belly of the vastus lateralis muscle in the left leg was recorded continuously for measurement of skeletal muscle deoxygenation responses during exercise.
Results: Peak oxygen uptake (18.4 +/- 3.5 vs. 28.2 +/- 10.7 mL[middle dot]kg-1[middle dot]min-1, p < 0.01) was significantly lower in MI. Change in muscle oxygen saturation from rest to peak exercise ([INCREMENT]SmO2) was significantly greater in MI than controls (2.5 +/- 5.6 vs. -7.4 +/- 3.4%, p < 0.01). Relative change in deoxygenated-hemoglobin/myoglobin concentration from rest to peak exercise ([INCREMENT]deoxy-Hb/Mb) was significantly lower in MI than controls (0.1 +/- 3.6 vs. 8.7 +/- 6.4 [mu]mol[middle dot]L-1, p < 0.01). In contrast, change in total-hemoglobin/myoglobin, which is an indicator of blood volume, was not significantly different between groups. Peak oxygen uptake was negatively correlated with [INCREMENT]SmO2 (r = -0.53, p < 0.05) and positively associated with [INCREMENT]deoxy-Hb/Mb at peak exercise (r = 0.65, p < 0.01) in MI.
Conclusion: Skeletal muscle deoxygenation abnormalities were observed during dynamic cycling exercise in early post-MI patients. These abnormalities were related to impaired peak aerobic capacity in early post-MI patients.
(C) 2014 American College of Sports Medicine