Cardiovascular Diseases and Cardiac Surgery

Oct. 03, 2017

Pectus deformities are the most common malformation of the chest wall, occurring in approximately 1 of every 150-1,000 births with a 3-to-1 male predominance. It is more common in the Caucasian race. Pectus excavatum (PEX), where the chest caves inward, occurs approximately five to six times more often than pectus carinatum.

The exact cause of PEX is not known, but the primary theory centers around unbalanced overgrowth in the costochondral regions. One study showed that patients with asymmetric PEX had shorter ribs on the more severely depressed side of the deformity.

Up to 43 percent of patients with PEX have a family history of the disease. It is thought to be a disease of multifactorial inheritance, and the exact genes implicated are unknown. PEX can be associated with scoliosis and connective tissue disorders such as Marfan syndrome, Ehlers-Danlos syndrome, and Noonan syndrome.

"PEX is of particular concern. In addition to cosmetic considerations, it may result in cardiac compression and cardiopulmonary impairment," says Dawn E. Jaroszewski, M.D., cardiothoracic surgeon at Mayo Clinic's campus in Arizona. "Although some patients are born with pectus, most notice development and significant progression of the deformity during rapid adolescent growth. This may be accompanied by onset or worsening of symptoms."

Sternal depression usually involves the lower sternum, with depression of the 4th through 7th costal cartilages. Varying degrees of rotation and asymmetry may be seen.

Symptoms may include:

• Disproportional dyspnea on exertion
• Loss of endurance
• Exertional and nonexertional chest pain
• Progressive fatigue
• Palpitations and tachycardia
• Exercise-induced wheezing
• Frequent respiratory tract infections
• Syncope or presyncope

Chest wall restriction and decreased thoracic volume are believed to play a role. Cardiac compression may reduce stroke volume.

The psychosocial issues associated with altered body image can be significant, especially in adolescents and young adults. The importance of "cosmetic concerns" to affected individuals and their families should not be underestimated by providers.

Evaluation

Evaluation needs to be individually tailored to the patient's symptoms. Noncontrast CT of the chest should be done to three-dimensionally assess the extent of the bony and cartilaginous deformity. MRI reduces radiation exposure but bone detail is better visualized by CT scan.

The Haller index of severity should be calculated by measuring the inner width of the chest at the lowest level of the PEX defect, and dividing it by the anterior-posterior distance (between the posterior surface of the sternum and the anterior surface of the spine) again at the lowest level of the defect. The mean calculated index in nonaffected individuals is 2.52; an index greater than 3.25 is considered severe.

Arrhythmias can be documented by electrocardiographic monitoring. Transthoracic or transesophageal echocardiography may be useful in assessing the degree of right atrial and right ventricular compression, and can also document the presence of mitral valve prolapse.

Evaluation of the aorta and aortic root should be performed in individuals with suspected or confirmed Marfan syndrome or other connective tissue syndromes.

Pre- and postoperative echocardiographic imaging has shown a significant improvement in patients' right ventricular output and flow with surgical repair and correction of cardiac compression.

Static pulmonary function tests are less sensitive in demonstrating compromised pulmonary function than dynamic testing, but may show reduced forced vital capacity and maximal ventilatory volumes.

Cardiopulmonary exercise testing (CPET) is an important tool for assessing the severity and effect of PEX on a patient. CPET can be used to quantify the degree to which PEX affects a patient's ability to move and utilize oxygen.

Cardiac limitation due to the defect can be demonstrated by an abnormally low peak max anaerobic VO2 during exercise testing. In studying PEX patients during exercise, patients were unable to reach the stroke volumes of control subjects at any intensity of exercise. Because of this, cardiac output is decreased, which leads to a limitation in peak exercise capacity. Exercise ability and peak VO2 have been shown in some studies to be statistically improved after repair of PEX.

Surgical repair?

Most patients should be considered for surgical repair if they demonstrate any two of the following criteria for surgical referral:

• Severe deformity as noted by Haller index greater than 3.25
• Evidence for cardiopulmonary disability
  • Decreased peak anaerobic VO2
  • Restrictive pulmonary disease
  • Right-sided cardiac compression seen by echocardiogram or thoracic imaging
  • Shift of heart into left thorax
• Symptoms of severe defect
• Severe body image disturbance

"Ideally, patients are referred for evaluation during adolescence," says Dr. Jaroszewski. "Repair during the teens allows the patient to complete growth and reduces the chance of recurrence." Correction is readily accomplished in these individuals. Repair in younger children with severe symptoms can be considered. Adult repair, although more difficult, can be performed with good results.

The two most common approaches to repair are various modifications of the open approach (Ravitch technique) and the minimally invasive approach (Nuss procedure).

Open repair

The open repair as described by Mark M. Ravitch, M.D., in Annals of Surgery in 1949 involves resecting a minimal amount of cartilage, and then placing a metal strut to support the sternum for six to 12 months. The procedure and its variations yield excellent results with low morbidity, and it is ideal for individuals with a combination excavatum and carinatum defect, severe asymmetry, or extensive defects of the upper ribs and cartilage.

Minimally invasive approach

The minimally invasive approach was first described by Donald Nuss, M.D., and colleagues in Annals of Pediatric Surgery in 1998. This procedure involves the placement of a substernal concave bar behind the sternum, which is then flipped into a convex position to elevate the sternum. This bar is left in place for two to three years while the sternum, associated cartilage and ribs remodel.

Advantages include smaller skin incisions, and avoidance of cartilage and bone resection. Cosmetic results are good to excellent in more than 85 percent of patients. Higher rates of complications and more postoperative pain have been reported in some series. Overall, both approaches yield excellent results.

Silicone implants also have been used for cosmetic correction, but the underlying deformity is not corrected. This option is probably best reserved for adults with mild, noncompromising defects.

The progressive cardiopulmonary consequences of untreated PEX are now well-recognized. Operative correction by experienced surgeons in high-volume centers is very successful. "Early referral and evaluation is critical to obtaining optimal results," says Dr. Jaroszewski.

For more information

Ravitch MM. The operative treatment of pectus excavatum. Annals of Surgery. 1949;129:429.

Nuss D, et al. A 10-year review of a minimally invasive technique for the correction of pectus excavatum. Journal of Pediatric Surgery 1988;33:545.