To Örebro University

Background

Peripheral muscle factors are presumed to be important contributors to the reduced exercise capacity in congenital heart disease (CHD), but the mechanisms are poorly understood.

Purpose

To investigate if muscle oxygenation in the calf muscle is impaired in adults with complex CHD in comparison to controls.

Method

Seventy-four adults with complex CHD (35.6±14.3 years, females n=22) were recruited from centers specialized in adult CHD. Seventy-four age and gender matched subjects were recruited as controls. Muscle oxygenation was successfully determined using near-infrared spectroscopy on the medial portion of m. gastrocnemiusin 63 patients and 67 controls. Measurements were made at rest, during venous occlusion to estimate blood flow (BF – indicated by the slope increase of total haemoglobin, HbT), at the start of isotonic unilateral heel-lifts to exhaustion, and immediately after exercise.

Results

In comparison to controls, patients had a lower muscle saturation (StO2) at rest, albeit not statistically significant, (66±17% vs. 60±19%, p=0.07), and a lower BF (0.38±0.21 vs. 0.31±0.21 HbTx3.5sec^–1, p=0.07). For exercise, compared to the controls, patients had a slower desaturation rate at exercise onset (−11.7±5.8% vs. −7.7±4.3%. StO2x3.5sec^–1, p<0.001), and both a slower resaturation rate (6.1±3.8% vs. 3.9±3.7% StO2x3.5sec^–1, p=0.002) and a slower half recovery time (16.8±11.1 vs. 28.6±21.2 sec, p<0.001) post exercise.

Conclusion

The lower muscle oxygenation and blood flow at rest, and the slower oxygenation kinetics during exercise may give insight to the mechanism for the reduced exercise capacity commonly found in adults with complex CHD. This finding may also provide implications for design of rehabilitation programs for these patients.