Cardiovascular magnetic resonance in patients with pectus excavatum compared with normal controls

Abstract

Purpose: To assess cardiothoracic structure and function in patients with pectus excavatum compared with control subjects using cardiovascular magnetic resonance imaging (CMR).

Method: Thirty patients with pectus excavatum deformity (23 men, 7 women, age range: 14-67 years) underwent CMR using 1.5-Tesla scanner (Siemens) and were compared to 25 healthy controls (18 men, 7 women, age range 18-50 years). The CMR protocol included cardiac cine images, pulmonary artery flow quantification, time resolved 3D contrast enhanced MR angiography (CEMRA) and high spatial resolution CEMRA. Chest wall indices including maximum transverse diameter, pectus index (PI), and chest-flatness were measured in all subjects. Left and right ventricular ejection fractions (LVEF, RVEF), ventricular long and short dimensions (LD, SD), mid-ventricle myocardial shortening, pulmonary-systemic circulation time, and pulmonary artery flow were quantified.

Results: In patients with pectus excavatum, the pectus index was 9.3 ± 5.0 versus 2.8 ± 0.4 in controls (P < 0.001). No significant differences between pectus excavatum patients and controls were found in LV ejection fraction, LV myocardial shortening, pulmonary-systemic circulation time or pulmonary flow indices. In pectus excavatum, resting RV ejection fraction was reduced (53.9 ± 9.6 versus 60.5 ± 9.5; P = 0.013), RVSD was reduced (P < 0.05) both at end diastole and systole, RVLD was increased at end diastole (P < 0.05) reflecting geometric distortion of the RV due to sternal compression.

Conclusion: Depression of the sternum in pectus excavatum patients distorts RV geometry. Resting RVEF was reduced by 6% of the control value, suggesting that these geometrical changes may influence myocardial performance. Resting LV function, pulmonary circulation times and pulmonary vascular anatomy and perfusion indices were no different to controls.

Figure 1

Chest wall measurements of a 16 year old male with severe pectus excavatum deformity. A Transverse TrueFISP (SSFP) images (TR/TE 630.5/1.4 msec, FA 80°): (a) minimum antero-posterior diameter of the chest (1.2 cm), (b) maximum transverse diameter of the chest (28.2 cm); (c) antero-posterior diameter of the left hemithorax (12.0 cm), (d) antero-posterior diameter of the right hemithorax (11.5 cm). The pectus index (b/a) in this case was 22.9, left chest flatness (b/c) was 2.35 and right chest flatness (b/d) was 2.44. B Transverse image showing complete (100%) leftward shift of the heart into left hemithorax. The maximum lateral distances of the left (LD_L = 15.02 cm) and right (LD_R = 0 cm) cardiac borders were measured from the midline (sterno-spinal line). Then cardiac left lateral shift (%) was measured as $(\frac{L{D}_L}{L{D}_L+L{D}_R})\times 100$. C Coronal TrueFISP image (TR/TE 630.5/1.4; msec, FA 80°) in same patient showing derivation of the indices of cardiac flatness: maximum horizontal diameter of the chest (e) which was 27.8 cm, maximum horizontal diameter of the heart (f) which was 14.8 cm and cardiac flatness (f/e) which was 0.53. D Sagittal image showing minimum AP diameter of the chest. Figure 1E-H Chest wall measurements in a 23 year old healthy subject male. E Transverse TrueFISP (SSFP) images (TR/TE 630.5/1.4; msec, FA 80°): (a) minimum antero-posterior diameter of the chest (9.07 cm), (b) maximum transverse diameter of the chest (24.7 cm); (c) antero-posterior diameter of the left hemithorax (13.3 cm), (d) antero-posterior diameter of the right hemithorax (13.0 cm). The chest index (b/a) in this case was 2.1, left chest flatness (b/c) was 1.8 and right chest flatness (b/d) was 1.9. F Transverse image showing leftward shift (67%) of the heart into left hemithorax. The maximum lateral distances of the left and right cardiac borders were measured as: LD_L = 8.71 cm and LD_R = 3.97 cm_. G and H are coronal and sagittal TrueFISP images in this healthy subject.

Figure 2

Cardiac cine images (TR/TE 29.4/1.2, FA 65°) of a 18 year old male with pectus deformity (pectus index being 17.9) and symptoms of exersional dyspnea. He has also noted discomfort in the lower anterior chest with activity and has experienced tachypnea and tachycardia. The heart is deviated considerably into the left chest by the depressed sternum. Note the restricted dilation at the end-diastolic phase.

Figure 3

Pulmonary perfusion in same patient as in figure one. Coronary time resolved images (TR/TE, FA) show a symmetric pulmonary perfusion with no perfusion deficits and normal cardio-pulmonary transit times in the most severe case among our patients with pectus severity index of 22.9.

Figure 4

Contrast enhanced high-resolution MR angiography (TR/TE 2.7/0.9, FA 70°) of a 17-year-old female with a pectus severity index of 7.9 and experience of increasing shortness of breath with exercise. 15 mm thickness maximum intensity projection images are made with an increment of 1 mm and 9 mm overlap. Images show the normal distribution of the pulmonary vessels with no abnormality. Pulmonary branches are completely assessable up to the 5^th branch order.

Figure 5

Comparison of right ventricle myocardial shortening in the direction of short and long diameters between patients with pectus excavatum and healthy control subjects.