Cor pulmonale

Pectus excavatum has never been reported to cause hypercapnic respiratory failure. In this report, we describe the first such case in a young woman with severe pectus excavatum who presented with chronic respiratory acidosis, pulmonary hypertension, and chronic cor pulmonale. An extensive diagnostic workup failed to uncover any other cause of respiratory acidosis, which led us to conclude that the severe chest wall deformity and the resulting severe restrictive defect were responsible for the development of chronic respiratory acidosis and cor pulmonale. (CHEST 2001; 119:1957-1961)

Key words: alveolar hypoventilation; cor pulmonale; pectus excavatum; respiratory failure

Abbreviations: TLC = total lung capacity; VC = vital capacity

Unlike deformities of the spine, pectus excavatum rarely results in a measurable impairment of lung function and is said to have never produced hypoventilation and respiratory failure.[1] A MEDLINE search failed to identify a report of a patient who had experienced respiratory failure attributed to pectus excavatum. Congestive cardiac failure also is said to be almost unheard of[2] and has not been observed in extensive hemodynamic studies.[3,4] Some patients may show a decreased diastolic filling of the right ventricle as a result of compression, but pulmonary arterial and pulmonary wedge pressures have been normal.[3,4] We describe the case of a young woman with severe pectus excavatum who presented with severe hypercapnic respiratory failure, pulmonary hypertension, and chronic cor pulmonale.

CASE REPORT

A 29-year-old Polish woman was admitted to St. Joseph's Hospital and Medical Center because of increasing dyspnea of 4 months' duration followed by the appearance of swelling of both feet of 3 days' duration.

The patient had been well until 4 months prior to hospital admission when she started noticing dyspnea on moderate exertion such as walking for one block or climbing one flight of stairs. Symptoms worsened over the following months until she started experiencing shortness of breath even at rest. There was no history of protracted cough, sputum production, chest pain, or hemoptysis. A review of her physiologic systems was unremarkable except for easy fatigability during most of her adult life, which she ascribed to a weak constitution. Her history was devoid of incidences of pneumonia, tuberculosis, bronchial asthma, or hospitalization. She had resided in the United States for 8 years and had worked for a garment factory sewing buttons on dresses.

She described her development as normal during her childhood except for being rather frail, which kept her from participating in sports. Only around age 12 years did she become aware of the abnormal funnel-shaped appearance of her chest, which she thought was strikingly different from her friends. She described her siblings and other family members as being devoid of any such deformities.

A physical examination showed a very thinly built, but lively and intelligent, young woman in mild respiratory distress at rest with the following physical characteristics: weight, 33.6 kg; height, 163 cm; pulse, 102 beats/min; BP, 108/58 mm Hg; and respiratory rate, 24 breaths/min. An examination of the chest showed severe pectus excavatum of the entire anterior chest wall with a straight back and mild scoliosis of the thoracic spine. Jugular venous distention at a 45 [degrees] angle and bilateral pitting pedal edema were noted. Breath sounds were diminished in the left lower lung field posteriorly without any adventitious sounds. Prominent left parasternal heave, enlarged cardiac dullness on percussion, loud [P.sub.2], and a loud pansystolic murmur at the pulmonic area were noted on cardiac examination. Liver edge was palpable at 2 cm below the right costal margin. Hepatojugular reflux was positive. A neurologic examination failed to show any motor or sensory deficits, with normal deep tendon reflexes.

Laboratory data showed a hemoglobin level of 16.9 g/dL and a WBC count of 5.1 x [10.sup.3]/[micro]L with a normal differential cell count. Serum chemistry levels were within normal range, except for a serum [HCO.sub.3] level of 40 mmol/L, and the results of a urinalysis were within normal limits. Arterial blood gas studies on room air at rest showed the following: pH, 7.38; Pa[CO.sub.2], 70 mm Hg; Pa[O.sub.2], 44 mm Hg; [HCO.sub.3], 42 mmol/L; and arterial oxygen saturation, 76% (alveolar-arterial oxygen gradient, 22 mm Hg). An ECG (Fig 1) showed sinus tachycardia with a rate of 116 beats/min, right-axis deviation, right atrial enlargement, and an rSR' pattern in [V.sub.2] without ST-T segment changes. A chest radiograph (Fig 2, 3) showed the entire heart to be displaced into the left hemithorax, clear visible lung fields, and a severe pectus excavatum with a marked reduction of the anteroposterior diameter of the chest. A CT scan of the chest (Fig 4) confirmed the severity of the pectus excavatum, reducing the space between the sternum and the vertebral bodies to about 2 cm and completely displacing the heart into the left hemithorax, which compressed the left lower lobe and the left mainstem bronchus. A high-resolution CT scan of the chest showed some interstitial changes in the lower lung fields and cystic changes in the left lower lobe with thickened pleura. Gallium scan findings were unremarkable. A quantitative perfusion lung scan showed 72% of the perfusion to the right lung and only 18% perfusion to the left lung. A ventilation/ perfusion lung scan showed a matched ventilation defect in the left lower lobe. An echocardiogram and a transesophageal echocardiogram showed severe pulmonary hypertension with no evidence of atrial or ventricular septal defect. The right atrium and right ventricle were dilated with reduced right ventricle systolic function and moderate tricuspid regurgitation. The left ventricle showed a normal ejection fraction with normal wall motion. Both the mitral and aortic valves were normal. Pulmonary function studies (Table 1) showed evidence of a severe restrictive defect (total lung capacity [TLC], 35% of predicted). Volume-adjusted diffusing capacity was mildly impaired (71% of predicted).

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Cardiac catheterization showed both the right atrium and right ventricle to be dilated with increased filling pressure of the right ventricle, decreased right ventricular systolic performance, and severe tricuspid regurgitation, severe pulmonary hypertension, increased pulmonary vascular resistance, and significant pulmonary venous desaturation. No intracardiac shunt was evident. The left atrium was normal in size with normal pulmonary venous return. Mitral valve prolapse was noted. Left ventricular systolic function was normal. No branch pulmonary artery stenosis or pulmonary venous stenosis was discovered. These findings are consistent with the diagnosis of cor pulmonale. A workup for collagen vascular disease, including antinuclear antibody, anti-DNA, complement level, and rheumatoid factor, was negative. Thyroid studies (triiodothyronine, levorotatory thyroxine, thyroid-stimulating hormone) were within normal limits. The results of a fluoroscopic examination of the diaphragm and a sniff test were normal, excluding a significant diaphragmatic dysfunction.

The patient was treated with diuretics, salt restriction, low-flow oxygen, and bilevel pressure ventilation, which resulted in improvement in dyspnea, pedal edema, and arterial blood gas levels. The patient was discharged to be observed in the pulmonary and cardiac clinics. She later underwent polysomnography and a shunt study as an outpatient. Polysomnography failed to show evidence of obstructive sleep apnea or central apnea. A shunt study was performed by sampling the patient's arterial blood after having her breathe 100% oxygen for 20 min, and the results showed a shunt fraction of 11%. Surgery was not offered as there was a concern that there was a prohibitive risk and that the procedure would not enhance her pulmonary function.

DISCUSSION

Clinical features of this case consist of a young woman with the physical findings of a severe pectus excavatum deformity of her chest wall and right-sided heart failure. Laboratory and other investigational data indicate the presence of chronic hypercapnia, hypoxemia with a significantly widened alveolar-arterial oxygen gradient (22 mm Hg), an increased hemoglobin level, severe pulmonary hypertension, and right atrial and right ventricular enlargement without evidence for an intrinsic cardiac disease or an intracardiac shunt. Lung fields were essentially clear except for some interstitial changes in the left lower lobe seen on a high-resolution CT scan. Is this a "zebra or a cobra on high heels," to paraphrase Dr. Eugene Robins' colorful description of the dilemma of separating an esoteric case from the mundane? To answer this question, a systematic approach considering all relevant diagnoses is essential.

The absence of a left ventricular disorder, valvular heart disease, or an intracardiac shunt as a cause of severe pulmonary hypertension and the presence of hypercapnia in this case would point to lung disease, chest wall disorder, diaphragmatic dysfunction, neuromuscular disease, obstructive apnea, or obesity-hypoventilation as possible causes of cor pulmonale with secondary pulmonary hypertension. An intrinsic (ie, diffuse infiltrative/interstitial) lung disease causing chronic hypoxemia resulting in cor pulmonale can be excluded on the basis of its absence on a chest radiograph and a CT scan of the chest. A low TLC and a normal [FEV.sub.1]/FVC ratio exclude an obstructive lung disease. Clinical features, polysomnography, and the studies of diaphragmatic function exclude obesity-hypoventilation, obstructive apnea, central apnea, neuromuscular disease, or diaphragmatic dysfunction as possible causes of alveolar hypoventilation. By process of elimination, chest wall deformity seems the only logical cause of hypercapnic respiratory failure and cor pulmonale in this case. Severe impairment of vital capacity (VC) [0.72 L; 19% of predicted] and TLC (1.76 L; 35% of predicted) are clearly the consequences of the severe restraint imposed by pectus excavatum deformity.

Profound gas exchange abnormalities, in this case, are the combined results of venous admixture, ventilation/ perfusion mismatch, and alveolar hypoventilation. Evidence of a widened alveolar-arterial oxygen gradient of 22 mm Hg and a shunt fraction of 11% suggest significant contributions to hypoxemia from both ventilation-perfusion mismatch and venous admixture. Hypercapnia, the result of alveolar hypoventilation, is an additional contributing factor. Similar mechanisms for gas exchange abnormalities are operative in patients with other disorders of the chest wall, including kyphoscoliosis, neuromuscular disease, or obesity-hypoventilation, as a consequence of the compression of otherwise normal lung parenchyma. Compression of the left lower lobe by the displaced heart alone could account for the widened alveolar-arterial oxygen gradient in our patient.

The most significant abnormality in this case is a severe pectus excavatum (funnel chest) deformity, with only 2 em of space between the vertebral bodies and the sternum, displacing the entire heart into the left hemithorax. Severe impairment of VC and TLC with a normal [FEV.sub.1]/FVC ratio and a near-normal, volume-adjusted diffusing capacity of the lung (Table 1) appear to be the consequences of the displacement and compression of lung parenchyma by an extreme degree of pectus excavatum, resulting in severe chronic hypercapnia, hypoxemia, and cor pulmonale.

Pectus excavatum was first described by Bauhinus in 1596[1] and later exhaustively studied by Ebstein.[5] Anatomic changes of pectus excavatum and the approaches for its correction were first described comprehensively by Brown.[6] Pectus excavatum is the result of a developmental abnormality of the anterior portion of the diaphragm. Often familial in nature, the deformity affects about 2.2% of the population. Clinical manifestations are mainly cosmetic and orthopedic in nature, with frequent psychological effects on children and their parents. Cardiac manifestations are said to be limited mostly to auscultation findings in one half of the patients and consist of a loud parasternal systolic murmur with a thrill and a split second sound. ECG changes (Fig 1) occur because of the displacement of the heart toward the left. Subjective symptoms of easy fatigability, exercise intolerance, dyspnea, precordial pain, and palpitations have been attributed to cardiac displacement, rotation, and angulation of great vessels. Congestive cardiac failure is almost unheard of and has not been observed in a number of extensive hemodynamic studies.[2-4] In a few cases, right ventricular pressure patterns showed a postsystolic dip with elevated end-diastolic pressure much like that seen in patients with mild constrictive pericarditis, which suggested disturbed right ventricular diastolic filling as a result of compression, which has been demonstrated by angiography in some cases.[7]

Similarly, the lung volume profile generally has been found to be within the normal range except for an occasional slight increase in the residual volume or mild reductions in TLC and VC.[6,8,9] Pectus excavatum, unlike deformities of the spine, rarely causes measurable functional impairment and has never resulted in hypoventilation and respiratory failure.[1]

A comparison with other reported surgical series[10-15] indicates that our patient has the most severe degree of pectus excavatum deformity based on the criteria in Table 2. An exhaustive review by Gaensler[1] and our review of the literature have failed to find a similar reported case. Therefore, we believe that this is the first report of a case of severe pectus excavatum causing chronic hypercapnic respiratory failure, pulmonary hypertension, and chronic cor pulmonale.

Surgical repair of the deformity provides cosmetic benefits, but the pathophysiologic benefits remain controversial. Although subjective improvement in exercise tolerance and dyspnea often are noted after surgery,[12,13] pulmonary function improvement is infrequent and modest.[14] Conversely, others have shown a reduction in pulmonary function after surgical repair.[10,15] Moreover, it should be noted that all reported surgical series consist of patients with either normal or mildly impaired pulmonary function. Consequently, the appropriateness of surgical repair is debatable when a substantial improvement in lung function is the primary objective, as it is in our patient.

ACKNOWLEDGMENT: The authors thank Jenifer s. Khan for her assistance in editing the article.

REFERENCES

[1] Gaensler EA. Lung displacement. In: Fenn WO, Rahn H, eds. Handbook of physiology: respiration. Washington, DC: American Physiological Society, 1965; 1649-1650

[2] Ravitch MM. Pectus excavatum and heart failure. Surgery 1951; 30:178-194

[3] Lyons HA, Zuhdi MN, Kelly JJ Jr. Pectus excavatum, cause of impaired ventricular distensibility as exhibited by right ventricular pressure pattern. Am Heart J 1955; 50:921-922

[4] Reusch CS. Hemodynamic studies in pectus excavatum. Circulation 1961; 24:1143-1150

[5] Ebstein W. Uber die trichterbrust. Arch Klin Med 1882; 30:411-423

[6] Brown AL. Pectus excavatum. J Thorac Surg 1939; 9:164-184

[7] Fabricius J, Davidson HG, Hansen AT. Cardiac function in funnel chest. Dan Med Bull 1957; 4:251-257

[8] Polgar G, Koop CE. Pulmonary function in pectus excavatum. Pediatrics 1963; 32:209-215

[9] Weg JG, Krumholz RA, Harkleroad LE. Pulmonary dysfunction in pectus excavatum. Am Rev Respir Dis 1967; 96:936-945

[10] Kaguraoka H, Ohnuki T, Itaoka T, et al. Degree of severity of pectus excavatum and pulmonary function in pre-operative and post-operative periods. Thorac Cardiovasc Surg 1992; 104:1483-1488

[11] Nakahara K, Ohno K, Miyoshi S, et al. An evaluation of operative outcome in patients with funnel chest diagnosed by means of the computed tomogram. Thorac Cardiovasc Surg 1987; 93:577-582

[12] Haller JA, Scherer LR, Turner CS, et al. Evolving management of pectus excavatum based on a single institutional experience of 664 patients. Ann Surg 1989; 209:578-582

[13] Morshuis W, Folgering H, Barentsz J, et al. Pulmonary function before surgery for pectus excavatum and at long-term follow-up. Chest 1994; 105:1646-1652

[14] Cahill JJ, Lees GM, Robertson HT. A summary of preoperative and post-operative cardiorespiratory performance in patients undergoing pectus excavatum and carnivatum repair. J Pediatr Surg 1984; 19:430-433

[15] Wynn S, Driscol D, Ostrom N, et al. Exercise cardiorespiratory function in adolescents with pectus excavatum. Thorac Cardiovasc Surg 1990; 99:41-47

(*) From the Pulmonary Division, St. Joseph's Hospital and Medical Center (Drs. Theerthakarai, El-Halees, and Javadpoor), Paterson, NJ; and Seton Hall University (Dr. Khan), School of Graduate Medical Education, South Orange, NJ.

Manuscript received March 14, 2000; revision accepted November 9, 2000.

Correspondence to: M. Anees Khan, MD, FCCP, Chief Pulmonary Division, St. Joseph's Hospital and Medical Center, 703 Main St, Paterson, NJ 07503

COPYRIGHT 2001 American College of Chest Physicians
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