MALEK, M. H., and E. W. FONKALSRUD. Cardiorespiratory Outcome after Corrective Surgery for Pectus Excavatum: A Case Study. Med. Sci. Sports Exerc., Vol. 36, No. 2, pp. 183–190, 2004.
Purpose: The purpose of this case study was to examine the effect of pectus excavatum before and after surgical correction on ventilatory and cardiorespiratory responses to submaximal and maximal exercise.
Methods: The patient was a 30-yr-old longshoreman who had mild pectus excavatum since infancy that became worse during his adolescent growth years. The deformity persisted into adulthood with increasing symptoms. Although he had a history of habitual aerobic exercise, the patient experienced frequent episodes of pain in the lower anterior chest, breathlessness, and reduced stamina when performing activities of daily living. He performed pulmonary function tests, submaximal and maximal incremental exercise testing, before and 6 months after corrective surgery.
Results: Six months after corrective surgery, the patient demonstrated increases in FEV1 (13.0%), maximum voluntary ventilation (MVV, 32.3%), maximum power output (max, 15.5%), V̇O2max (7.9%), metabolic threshold (V̇O2θ, 30.8%), oxygen-pulse (V̇O2/fc, 14.0%), and maximal tidal volume (VTmax, 11.7%). On submaximal testing, we found that the time constant for oxygen uptake kinetics was 46.8 s for the on-transit and 46.5 s for the off-transit before surgery and 33.6 s for the on-transit and 30.3 s for the off-transit six months after surgery.
Conclusions: The information derived from this case study supports the opinion that corrective surgery for pectus excavatum may alleviate the impaired ventilatory and cardiorespiratory performance seen preoperatively.
Pectus excavatum is a relatively common congenital deformity of the chest wall with an incidence of approximately one in every 300 births (20). This condition is more common than Down syndrome, which occurs one in every 600 to 1000 births (27). Although the pathogenesis of pectus excavatum remains unclear, investigators have hypothesized that the deformity results from unbalanced overgrowth in the costochondral regions. As a result, the chest appears concave, and a displaced heart is often palpable on the left mid-auxiliary line slightly below the armpit. Pectus excavatum occurs more often in males than females (9:1) and accounts for 90% of congenital chest wall deformities. Approximately 40% of pectus excavatum patients are aware of one or more members of their family who have pectus deformities; however, a genetic link has not been established (17). Despite numerous published reports, there is no consensus upon what degree of physiological impairment, if any, exists in this anomaly. Because of this ambiguity, many health maintenance organizations (HMOs) hold the position that corrective surgery for pectus excavatum may not improve cardiorespiratory function.
The severity of pectus excavatum can be calculated by dividing the inner width of the chest at the widest point, by the distance between the posterior surface of the sternum and anterior surface of the spine (see Fig. 1) as determined on computed tomography (CT) scans or chest radiographs (25). The mean index for normal persons is 2.5. We have observed symptomatic pectus excavatum patients with severity index ranging from 3.2 to 12.7 (20). Also, Fonkalsrud and Reemtsen (21) recently found that the downward pressure exerted on the mediastinal structures range from 14.7 kg, for those individuals with pectus severity index less than 4.5, to 18.6 kg for those individuals with pectus severity index greater than 4.6. It should be noted, that an index lower than 2.2 would be characterized as pectus carinatum (i.e., pigeon breast) which accounts for 10% of pectus deformity cases (18).
Patients with pectus excavatum, regardless of their severity index, complain of fatigue, dyspnea, chest discomfort, and palpitations occurring with mild exertion and limited exercise performance. The response to exercise is a function of numerous physiological mechanisms. In particular, the ability to sustain high-intensity exercise is contingent on four aerobic parameters: a) maximum oxygen uptake (V̇O2max), b) the metabolic threshold (V̇O2θ) above which there is a sustained increase in blood lactic acid concentration, c) work efficiency represented as the slope of δV̇O2/&U1E86; and d) the time constant for oxygen uptake τV̇O2 (34). Each of these parameters indirectly relates to the efficiency of the cardiovascular system. Patients with pectus excavatum represent a unique opportunity to differentiate central from peripheral cardiovascular abnormalities. Thus, this case study sought to examine the strength of the relationship between pectus excavatum and physiological impairment before and 6 months after corrective surgery.
Studies examining pre- and postoperative cardiorespiratory outcomes have been inconclusive concerning the physiological benefit of corrective surgery. These studies utilized various means of exercise testing and different surgical techniques to correct the chest wall deformity (15,20,24,26,28,29,35). Therefore, it is difficult to compare studies on indices of pre- and postoperative cardiorespiratory functioning. The purpose of this case study is to investigate the physiological responses to exercise performance in a pectus excavatum patient, before and after corrective surgery, using a standardized protocol that optimizes evaluation of cardiorespiratory outcomes to maximal incremental exercise.