Different Patterns of Cerebral and Muscular Tissue Oxygenation 10 Years After Coarctation Repair

Abstract

The purpose of this study was to assess whether the lower exercise tolerance in children after coarctation repair is associated with alterations in peripheral tissue oxygenation during exercise. A total of 16 children after coarctation repair and 20 healthy control subjects performed an incremental ramp exercise test to exhaustion. Cerebral and locomotor muscle oxygenation were measured by means of near infrared spectroscopy. The responses of cerebral and muscle tissue oxygenation index (cTOI, mTOI), oxygenated (O₂Hb), and deoxygenated hemoglobin (HHb) as a function of work rate were compared. Correlations between residual continuous wave Doppler gradients at rest, arm-leg blood pressure difference and local oxygenation responses were evaluated. Age, length, and weight was similar in both groups. Patients with aortic coarctation had lower peak power output (Ppeak) (72.3 ± 20.2% vs. 106 ± 18.7%, P < 0.001), VO₂peak/kg (37.3 ± 9.1 vs. 44.2 ± 7.6 ml/kg, P = 0.019) and %VO₂peak/kg (85.7 ± 21.9% vs. 112.1 ± 15.5%, P < 0.001). Cerebral O₂Hb and HHb had a lower increase in patients vs. controls during exercise, with significant differences from 60 to 90% Ppeak (O₂Hb) and 70% to 100% Ppeak (HHb). Muscle TOI was significantly lower in patients from 10 to 70% Ppeak and muscle HHb was significantly higher in patients vs. controls from 20 to 80% Ppeak. Muscle O₂Hb was not different between both groups. There was a significant correlation between residual resting blood pressure gradient and Δmuscle HHb/ΔP at 10-20W and 20-30W (r = 0.40, P = 0.039 and r = 0.43, P = 0.034). Children after coarctation repair have different oxygenation responses at muscular and cerebral level. This reflects a different balance between O₂ supply to O₂ demand which might contribute to the reduced exercise tolerance in this patient population.

Keywords: children; coarctation aortae; exercise test; muscle oxygenation; near infrared spectroscopy.

FIGURE 1

Response pattern of cerebral TOI, HHb, and O₂Hb as a function of work rate, expressed in 10% Ppeak intervals. Black circles represent the healthy controls, white circles represent the coarctation aortae patients, and ^∗ indicate significant differences between patients and controls.

FIGURE 2

Response pattern of muscle TOI, HHb, and O₂Hb as a function of work rate, expressed in 10% Ppeak intervals. Black circles represent the healthy controls, white circles represent the coarctation aortae patients, and ^∗ indicate significant differences between patients and controls.

FIGURE 3

Change in muscle HHb (Δmuscle HHb) relative to the change in work rate (ΔP) for each 10 Watt interval in healthy controls (black bars) and coarctation aortae patients (gray bars). ^∗ indicate significant differences between the groups.

FIGURE 4

Correlation between the change in muscle HHb (Δmuscle HHb) and residual echocardiographic (A,B) or blood pressure gradient (C). (A) Relative to the change in work rate (ΔP) for 10–20 Watt. (B) Relative to the change in work rate (ΔP) for 20–30 Watt (B) Ppeak and the residual gradient using echocardiography in coarctation patients. (C) The correlation between the total amplitude of muscle HHb (difference between 0% Ppeak and 100% Ppeak) and blood pressure difference between arm and leg at maximal exercise.