P2D317: Cardiopulmonary Impact of the Minimally Invasive Repair of Pectus Excavatum in Pediatric Patients – a Prospective Study

Background: Pectus excavatum (PE) is associated with compromised cardiopulmonary response during exercise due to compression of the heart and lungs. Minimally invasive repair of PE (MIRPE) elevates the sternum and relieves anatomical compression; however, the physiologic benefits of this on cardiopulmonary function are poorly understood. We sought to examine the effects of MIRPE on exercise response during cardiopulmonary exercise testing (CPET).

Methods: A prospective study beginning in February 2021 enrolled patients who underwent MIRPE at ≤ 18 years of age and were presenting for pectus bar removal. All patients had CPET prior to MIRPE, and CPET was repeated 3-9 months after bar removal. Oxygen (O2) pulse at maximal exertion was used as an index of cardiovascular efficiency, and maximal oxygen consumption (Peak VO2) was used to measure exercise capacity. Patient demographics, Haller index (HI), correction index (CI), and preoperative and postoperative CPET results were analyzed. CPET Variables were expressed as absolute values and percent predicted. Patients self-reported changes in activity at the time of enrollment. Descriptive statistics were utilized for patient characteristics. Paired sample T-tests were used to compare patient’s pre- and post-MIRPE CPET results.

Results: Twenty-five patients were enrolled, 72% (18/25 ) of whom were male. The median age at MIRPE and at bar were removal 15.0 [IQR:14-16.5] years and 18.6 [IQR:17.5-19.8] years, respectively. A median of 4.5 [IQR:4.0-7.6] months elapsed from bar removal to CPET. The median HI and CI were 4.5 [IQR:3.8-5.7] and 29.4% [IQR:23.0-40.3], respectively. Patients had a mean weight and height increased between preoperative and postoperative CPET of 8.6±7.2 kg (p < 0.001) and 4.3±5.3 cm (p < 0.001). 7 (28%) patient reported decreased activity post-operatively.
Following MIRPE, statistically significant increases were found in percent predicted maximal heart rate (HR) (91.3% vs 94.4%, p=0.015), O2 pulse, (10.3 vs 12.1 ml/beat, p=0.004), and percent predicted O2 pulse (79.5% vs 84.4%, p=0.046). The peak VO2 /kg and percent predicted peak VO2/kg did not change significantly following MIRPE; however, the peak VO2 (not weight indexed) did increase significantly (p < 0.001) (Table 1).
Patients were stratified by exercise changes preoperatively versus postoperatively (no change, increased, or decreased). The O2pulse, percent predicted O2 pulse, and the peak VO2 increased in patient with stable activity levels. Peak VO2/kg and precent predicted peak VO2/kg decreased in patients with decreased activity levels, Table 2.

Conclusion: Following MIRPE, there was an increase in O2 pulse which is a surrogate for stroke volume response. The increase in O2 pulse may reflect relief of cardiac compression that was present preoperatively. Exercise capacity (VO2/kg) is multifactorial and despite improvement in stroke volume response, other factors such as changes in weight and physical activity levels limited post-operative change. O2 pulse may be a more reproducible measure of the effects of cardiac decompression following MIRPE.