Fate of trileaflet equine pericardial extracardiac conduit used for the correction of anomalies having pulmonic ventricle-pulmonary arterial discontinuity.

BACKGROUND

External conduits used for the repair of congenital heart diseases having discontinuity between the pulmonic ventricle and the pulmonary artery still carries a high risk of reoperation. Between June 1983 and June 1992, handmade equine pericardial conduit with fabricated trileaflet valve had been the conduit of choice in our institute. The aim of this study is to clarify the temporal sequence of conduit obstruction in this material and to formulate the optimal surgical strategies for this disease entity.

METHODS

One hundred forty-three patients have undergone extracardiac conduit repair using this conduit. Postoperative catheterization performed within 2 months showed pulmonary to systemic ventricular systolic pressure ratio of 0.57 +/- 0.17 with the pressure gradient between pulmonic ventricle and pulmonary artery of 21.1 +/- 17.2 mm Hg. In 63 patients among the survivors, a series of Doppler two-dimensional echocardiographic images could be clearly obtained.

RESULTS

Moderate-to-severe degree of pulmonary insufficiency represented only 3.2% of all cases within 3 months, which rapidly increased to 14.3% at 1 to 3 years and 32.8% at 3 to 5 years. However, the rate of increase of pulmonary insufficiency diminished beyond 5 years with 34.9% at 5 to 7 years and 40.0% at 7 to 9 years. Estimated pressure gradient calculated by Bernoulli's equation applied in the same patient subset was 4.1 +/- 7.9 mm Hg within 3 months, which progressively increased to 7.1 +/- 11.8 mm Hg at 1 to 3 years, 21.0 +/- 24.0 mm Hg at 3 to 5 years, 40.2 +/- 25.9 mm Hg at 5 to 7 years, and 71.3 +/- 34.0 mm Hg at 7 to 9 years. Among patients with a pressure gradient across the conduit of more than 40 mm Hg at follow-up catheterization, the primary cause of the obstruction was attributed to degeneration of the valve in 7 patients, whereas sternal compression was strongly suspected as the primary cause in the other 8 patients. Intimal peel was not obvious in the excised specimens.

CONCLUSIONS

Degeneration of the valve in the equine pericardial conduit became prominent at 3 to 5 years after the operation, whereas the pressure gradient across the conduit continued to progress thereafter. A thick and hardened valve from degeneration and varying degrees of external compression by the sternum were delineated at the site of stenosis.