The risk of surgical treatment of tetralogy of Fallot: an appraisal.

The risk of surgical treatment of tetralogy of Fallot was analyzed with multivariate statistical techniques in a recent surgical series (1975-1983) of 159 corrected and 59 palliated patients. The overall mortality of correction was 12.6% and that of palliation was 15.3%. The significant and independent risk factors that increased the mortality of palliation were the use of a shunt other than the Blalock or its modifications (mostly Waterston) (P = 0.01), and very young age (P = 0.02). Risk factors that increased the mortality of correction were high left over right ventricular pressure ratio (P-RV/LV) (P = 0.02), persistent patency of the arterial duct (P = 0.02), other major associated lesions (P = 0.02), and the use of a transannular patch (P = 0.04). Cardioplegia significantly decreased the risk (P = 0.03). With present techniques, correction can be performed in favorable cases with a mortality approaching zero. Staged procedures neutralized the age related risk of correction, but Blalock shunts carried a mortality rate ranging from 9.5% at 1 month to 1.7% at 12 months of age. This was due to the lack of prostaglandins along with technical faults. Predicted two-stage mortality rates ranged in infants (less than 12 months) from 6.2 to 16% and compared favorably with our observed 27% mortality of primary correction. Our results show that the transannular patch becomes a fully expressed risk only in those patients with restrictive pulmonary arteries or isolated branch stenosis. This is because it decreases the force the right ventricle can generate in maintaining the cardiac output. The chances of survival, when compared with those of patients without transannular patch, are significantly less when the P-RV/LV is between 0.6 and 1.0. We therefore discuss the measures to decrease or neutralize this risk related to insertion of a transannular patch. Among the associated lesions, we discuss briefly the potential for residual right outflow tract stenosis, anomalous origin of the left anterior descending coronary artery and anomalous muscle bundle of the right ventricle.