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Ann Thorac Surg 2010;89:240-243. doi:10.1016/j.athoracsur.2009.06.126
© 2010 The Society of Thoracic Surgeons
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Original Articles: General Thoracic

Cardiac Function Assessed by Transesophageal Echocardiography During Pectus Excavatum Repair

Thorsten Krueger, MDa,*, Pierre-Guy Chassot, MDb, Michel Christodoulou, MDa, Cai Cheng, MDa, Hans-Beat Ris, MDa, Lennart Magnusson, MDb

a Thoracic and Vascular Surgery Service, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
b Department of Anesthesiology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland

Accepted for publication June 4, 2009.

* Address correspondence to Dr Krueger, Thoracic and Vascular Surgery Service, Centre Hospitalier Universitaire Vaudois, Lausanne, 1011, Switzerland (Email: thorsten.krueger{at}chuv.ch).


   Abstract
Top
 Abstract
Introduction
 Patients and Methods
 Results
 Comment
 References
 
Background: We assessed end-diastolic right ventricular (RV) dimensions and left ventricular (LV) ejection fraction by use of intraoperative transesophageal echocardiography before and after surgical correction of pectus excavatum in adults.

Methods: A prospective study was conducted including 17 patients undergoing surgical correction of pectus excavatum according to the technique of Ravitch-Shamberger between 1999 and 2004. Intraoperative transesophageal echocardiography was performed under general anesthesia before and after surgery to assess end-diastolic RV dimensions and LV ejection fraction. The end-diastolic RV diameter and area were measured in four-chamber and RV inflow-outflow view, and the RV volume was calculated from these data. The LV was assessed by transgastric short-axis view, and its ejection fraction was calculated by use of the Teichholz formula.

Results: The end-diastolic RV diameter, area, and volume all significantly increased after surgery (mean values ± SD, respectively: 2.4 ± 0.8 cm versus 3.0 ± 0.9 cm, p < 0.001; 12.5 ± 5.2 cm2 versus 18.4 ± 7.5 cm2, p < 0.001; and 21.7 ± 11.7 mL versus 40.8 ± 23 mL, p < 0.001). The LV ejection fraction also significantly increased after surgery (58.4% ± 15% versus 66.2% ± 6%, p < 0.001).

Conclusions: Surgical correction of pectus excavatum according to Ravitch-Shamberger technique results in a significant increase in end-diastolic RV dimensions and a significantly increased LV ejection fraction.


   Introduction
Top
 Abstract
 Introduction
Patients and Methods
 Results
 Comment
 References
 
Surgical correction of pectus excavatum deformity is frequently performed for a variety of symptoms and usually results in globally satisfactory long-term results in most published reports, with improvement in self-confidence of the patients and a general clinical impression of increased stamina after surgical repair. However, whether the latter is related to psychological aspects or to a real improvement of cardiovascular or pulmonary performance after surgical repair remains controversial. The improvement of cardiac function after surgical correction of pectus excavatum is the object of a debate, recently illustrated by the publication of two different meta-analyses showing contradictory results. Analyzing eight studies including 169 patients, Malek and colleagues [1] found a statistically significant amelioration in cardiovascular functions after surgical correction, whereas Guntheroth and colleagues [2] found no increase in left ventricular (LV) size, stroke volume, and cardiac output in 4 of 5 studies grouping 118 patients. In the cited reports, assessment of cardiac function was obtained in most instances either by the use of indirect estimates on the base of pulse oxymetry or by transthoracic echocardiography, despite the limitations imposed by the abnormal anatomy of pectus excavatum. In addition, there was a lack of assessment of LV ejection fraction (LVEF) in some of the reports.

To alleviate these methodologic drawbacks, we assessed in a prospective trial the end-diastolic right ventricular (RV) dimensions and LVEF before and after surgical repair of pectus excavatum by use of intraoperative transesophageal echocardiography (TEE).


   Patients and Methods
Top
 Abstract
 Introduction
 Patients and Methods
Results
 Comment
 References
 
Patients
In this prospective study, all patients operated on between 1999 and 2004 at our institution underwent intraoperative TEE with evaluation of RV dimensions and LVEF before and after surgical correction of their pectus excavatum deformity. Seventeen adult patients were assessed, 13 male and 4 female, with a mean age of 28 years (range, 17 to 54). All patients expressed a variety of symptoms mainly related to impaired exercise tolerance and aesthetic concerns. The study was reviewed and approved by the Institutional Ethical Committee, and consent was obtained from all patients.

Surgery
Surgery was performed under general anesthesia according to the technique of Ravitch-Shamberger. A transverse submammary skin incision was performed with dissection of both the great pectoralis and rectus abdominis muscles from the rib cage and the sternum, followed by bilateral subperiosteal resection of the rib cartilages III to VII from the sternocostal articulations to the osteocartilagenous junctions. Transverse osteotomy and wedge resection of the sternum at the level of the deformity were performed followed by cerclage osteosynthesis. A Sulamaa plate was driven across to the sternum perpendicular to its long axis and positioned on the rib cage on both sides to stabilize the sternum in the corrected position, followed by reinsertion of the anterior chest wall muscles and readaptation of the subcutaneous tissue and skin.

Fluid administration during surgery was estimated on the basis of a preoperative deficit of 2 mL · kg–1 · h–1 of fasting and intraoperative needs of 5 mL · kg–1 · h–1.

Intraoperative TEE
The transesophageal probe was inserted after tracheal intubation, and a complete cardiac examination was conducted. Three standard views were selected for measurements: (1) the four-chamber view; (2) the inflow-outflow view of the right ventricle; and (3) the transgastric short-axis view of the left ventricle. Measurements of the end-diastolic RV dimensions (Fig 1) and of LVEF were performed before, during, and after surgical correction of the deformity [3–7].


Figure 1
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  		Fig 1. (A) Schematic wire-frame diagram of the three-dimensional shape of a human right ventricular cast obtained by real-time long and short-axis measurements. (B) Computation and representation of a spheroid right ventricle model obtained by real-time long- and short-axis measurements. (PA = pulmonary artery; TV = tricuspid valve.) (Reprinted from Jiang L, Wiegers SE, Weyman AE, Right ventricle, In: Weyman AE, Editor, Principles and practice of echocardiography, Lea & Febiger, 1994 [4], with permission.)

 
The end-diastolic dimension of the RV cavity was measured by its transverse diameter (largest short-axis distance parallel to the plane of the tricuspid valve) and its area, both in four-chamber view (0 degrees on a multiplane probe; Fig 2) and in RV inflow-outflow view (60 degrees on a multiplane probe; Fig 3). The RV volume was calculated with Simpson's rule as follows: the computer of the echocardiography machine divided the area delineated by the endocardial border of the right ventricle in 20 slices assumed to be small circular discs of same diameter and known thickness (one twentieth of the ventricle long axis). It then added the calculated volume of each of them to obtain the total volume of the ventricle. This calculation was performed on two different planes (0 and 60 degrees), and the values were averaged.


Figure 2
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  		Fig 2. Transesophageal four-chamber view of the right ventricle (RV) before (A) and after (B) surgical correction. The transverse diameter (double arrow) corresponds to the largest short-axis distance parallel to the plane of the tricuspid valve. The area is calculated by delineating the endocardial border of the RV from its apex to the level of the tricuspid annular plane. In this case, the diameter and the area increased after surgery from 2.2 to 3.4 cm (+ 41%) and from 8.38 cm2 to 13.1 cm2 (+ 36%), respectively. (LV = left ventricle.)

 

Figure 3
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  		Fig 3. Transesophageal inflow-outflow view of the right ventricle (RV) before (A) and after (B) surgical correction. The transverse diameter (double arrow) corresponds to the largest short-axis distance parallel to the plane of the tricuspid valve. The area is calculated by delineating the endocardial border of the RV from the plane of the pulmonary valve to the plane of the tricuspid. In this case, the diameter and the area increased after surgery from 2.9 to 3.5 cm (+ 17%) and from 14.6 cm2 to 15.8 cm2 (+ 8%), respectively. (LV = truncated left ventricle.)

 
The LVEF was calculated according to Teichholz formula by measuring the transgastric short-axis diameter at mid-papillary level in end-systole and end-diastole by M-mode echocardiography.

The preoperative and postoperative TEE measurements were made after intubation and before the skin incision, and after the skin closure but before extubation, respectively. All measurements were made in apnea by disconnecting the patient from the anesthesia respirator.

Statistical Analysis
The t test for paired observation was used to compare the measured values in each patient before and after the surgical correction. A bidirectional hypothesis was used, and statistical significance accepted at p less than 0.05. The Pearson test was used to assess the correlation between fluid administration during surgery and end-diastolic RV diameter and LVEF, respectively.


   Results
Top
 Abstract
 Introduction
 Patients and Methods
 Results
Comment
 References
 
The mean values of the end-diastolic RV dimensions and of the LVEFs before and after surgical correction of pectus excavatum are summarized in Table 1. The end-diastolic RV diameter, area, and volume all significantly increased after surgery (p < 0.001). Intraoperative TEE revealed that all patients had a marked RV compression and deformation exerted by sternal depression before surgical correction, which was alleviated by surgical correction (Fig 2). It also revealed that the most important surgical step in this respect was sternal osteotomy followed by sternal elevation. The estimated average increase of the end-diastolic RV area and volume after surgical correction were 47% and 88%, respectively.


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  		Table 1 End-Diastolic Right Ventricular Dimensions and Left Ventricular Ejection Fraction Assessed by Intraoperative Transesophageal Echocardiography Before and After Surgical Correction of Pectus Excavatum Deformity (n = 17)
 
The LVEF also significantly increased after surgical correction (p < 0.001), with an estimated average increase of 14%.

The calculated need of intraoperative fluid administration was 2,318 ± 334 mL, and the total fluid administered was 2,103 ± 439 mL (mean ± SD). No significant correlation between end-diastolic RV diameter or LVEF with fluid administered (mL/kg bodyweight or mL/kg bodyweight per hour of operating time) was found.


   Comment
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
References
 
Surgical correction of pectus excavatum usually results in improved self-confidence and increased stamina in young adults in most reports, but it remains controversial and a matter of debate whether this is accompanied by a gain in cardiopulmonary reserves. A recently published meta-analysis indicates that surgical repair of pectus excavatum does not significantly improve pulmonary function [8]. In contrast, a meta-analysis from the same authors including eight studies published between 1960 and 2005 (169 patients) suggests a statistically significant amelioration in cardiovascular functions after surgical correction [1]. This finding was contested by another recent review concentrating on direct cardiac performance measurements rather than derivatives of exercise performance such as O2 pulse measurements [2]. This review was based on five publications (118 patients) that analyzed cardiac function before and after surgery using radionuclides, transthoracic two-dimensional echocardiography, radiographic planimetry, and cardiac output by the Fick method. Cardiac function was studied most frequently by transthoracic echocardiography despite its methodologic limitations due to the abnormal anatomy of the deformed anterior chest wall. No improvements were found in LV size, stroke volume, and cardiac output after surgery in four of five studies, but one report revealed a 22% increase in LV stroke volume after surgery by squaring the LV diameter from transthoracic M-mode echocardiography [9]. An additional study based on transthoracic echocardiography (which was not included in this review) also demonstrated a 15% improvement of LV function after surgical repair of pectus excavatum in 34 patients [10].

To overcome the methodologic drawbacks of transthoracic echocardiography for the evaluation of RV dimensions and LV function, we prospectively performed intraoperative TEE in 17 patients with pectus excavatum before and after surgical repair. Our results show that RV dimensions and LVEF both significantly increased by surgical correction of pectus excavatum.

The RV transverse diameter situated in the sagital plane of the chest was selected for measuring the effect of surgery because the RV compression by the anterior chest wall was mainly anteroposterior (Figs 2 and 3). The difference in the preoperative and postoperative dimensions of the RV cavity was more pronounced in its transverse axis (largest short-axis distance parallel to the plane of the tricuspid valve) than in its long-axis (distance between the plane of the tricuspid valve and the apex). The recorded end-diastolic RV diameters were within the normal range, both before correction (2.4 ± 0.8 cm) and after correction (3.0 ± 0.9 cm), as the normal diameter in adults is 2.4 to 3.1 cm [3, 4, 6, 7]. However, the values for the end-diastolic RV area, normally situated between 14 and 16 cm2 in the four-chamber view [5], were smaller than normal before correction (12.5 ± 5.2 cm2) and larger than normal after correction (18.4 ± 7.5 cm2).

Simpson's rule, which assumes the cavity to have a circular symmetry along its axis on the selected echocardiographic plane, is well suited for calculating the volume of the left ventricle, which is rather circular in cross section. That is not the case for the right ventricle, which is shaped like a crescent wrapped around the anterior face of the cylindrical left ventricle, with a large inflow tract (tricuspid valve) and a tubular outflow tract (Fig 1). In all echocardiographic planes, the area of the RV appears smaller than the area of the LV; on average, the RV area is 0.6 times the LV area. The RV volumes calculated with the Simpson's rule are therefore biased toward exceedingly small values. That is particularly the case in the four-chamber view (0-degree plane). It also biases the percentage increase in volume after correction toward exceedingly high values (± 88%) because it deduces the volume of the whole ventricle from the sole anteroposterior plane, where the increase after correction is maximal.

In a comparison of two-dimensional transthoracic echocardiography between patients with pectus excavatum and normal controls, Mocchegiani and colleagues [11] found that the RV outflow tract was narrower in pectus excavatum patients, but the RV cavity slightly larger than in normal chest patients (area 18.0 ± 2.3 cm2 versus 15.5 ± 1.7 cm2 in four-chamber apical view). The magnitude of these abnormalities was related to the degree of chest wall deformity evaluated on chest roentgenogram. The RV emptying fraction was reduced in pectus excavatum patients compared with controls, but no relationship could be found between this reduction and the degree of chest wall deformity [11]. Our results disagree partially with these data, because the RV area increased significantly after surgical correction of pectus excavatum in our study.

From a methodologic point of view, caution in the interpretation of TEE assessments of RV areas might be indicated, since they are dependent on the plane of measurement. Given the variable nature of the relationship between the esophagus and the heart, a specific TEE plane does not guarantee that a "standard" TEE plane such as 0 degrees or 60 degrees will provide equivalent data in individual patients. In contrast, TEE measurements of LV function are standardized and reliable, and demonstrated an increase in LVEF from 58% to 66% (± 14%) in our patients. That indicates a significant improvement in cardiovascular function secondary to surgical repair of pectus excavatum, in accordance with the results of Hu and colleagues [9] who showed a 22% increase in LV stroke volume and an 11% increase in ejection fraction by M-mode echocardiography. It fits also with the results of Bawazir and colleagues [12] who showed 11% increase in stroke volume and 15% increase in cardiac output measured by 2D echocardiography, and with Kowalewski and colleagues [10] who demonstrated an increase in RV and LV end-diastolic volumes after surgery (49% and 11%, respectively).

The absence of correlation between intraoperative fluid administration and increased RV dimension and LVEF indicates that the improved hemodynamic variables measured at the end of the pectus excavatum repair are not explained by an increased cardiac preload due to fluid administration during surgery.

In conclusion, intraoperative TEE measurements suggest a significant increase in end-diastolic RV ventricular dimensions and a significantly increased LVEF after surgical correction of pectus excavatum according to the Ravitch-Shamberger techniqe. However, this study does not correlate the magnitude of improvement in cardiac function with the importance of preoperative chest wall deformities and its clinical impact during later follow-up.


   References
Top
 Abstract
 Introduction
 Patients and Methods
 Results
 Comment
 References
 

  1. Malek MH, Berger DE, Housh TJ, Marelich WD, Coburn JW, Beck TW. Cardiovascular function following surgical repair of pectus excavatum Chest 2006;130:506-516.[Medline]
  2. Guntheroth WG, Spiers PS. Cardiac function before and after surgery for pectus excavatum Am J Cardiol 2007;99:1762-1764.[Medline]
  3. Drexler M, Erbel R, Muller U, Wittlich N, Mohr-Kahly S, Meyer J. Measurement of intracardiac dimensions and structures in normal young adult subjects by transesophageal echocardiography Am J Cardiol 1990;65:1491-1496.[Medline]
  4. Jiang L, Wiegers SE, Weyman AE. Right ventricleIn: Weyman AE, editor. Principles and practice of echocardiography. Philadelphia: Lea & Febiger; 1994. pp. 913.
  5. Michaux I, Filipovic M, Skarvan K. Right ventricleIn: Poelaert J, Skarvan K, editors. Transesophageal echocardiography in anaesthesia and intensive care medicine. 2nd ed.. London: BMJ Books; 2004. pp. 150.
  6. Weyman AE. Principles and practice of echocardiographyPhiladelphia: Lea & Febiger; 1994. pp. 1293.
  7. Feigenbaum H. EchocardiographyPhiladelphia: Lea & Febiger; 1994. pp. 658.
  8. Malek MH, Berger DE, Marelich WD, Coburn JW, Beck TW, Housh TJ. Pulmonary function following surgical repair of pectus excavatum: a meta-analysis Eur J Cardiothorac Surg 2006;30:637-643.[Abstract/Free Full Text]
  9. Hu T, Feng J, Liu W, et al. Modified sternal elevation for children with pectus excavatum Chin Med J 2000;113:451-454.[Medline]
  10. Kowalewski J, Barcikowski S, Brocki T. Cardiorespiratory function before and after operation for pectus excavatum: medium-term results Eur J Cardiothorac Surg 1998;13:275-279.[Abstract/Free Full Text]
  11. Mocchegiani R, Badano L, Lestuzzi C, Nicolosi GL, Zanuttini D. Relation of right ventricular morphology and function in pectus excavatum to the severity of the chest wall deformity Am J Cardiol 1995;76:941-946.[Medline]
  12. Bawazir OA, Montgomery M, Harder J, Sigalet DL. Midterm evaluation of cardiopulmonary effects of closed repair for pectus excavatum J Ped Surg 2005;40:863-867.[Medline]

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