Analysis of malformations of the heart amenable to a Blalock-Taussig operation

The Blalock-Taussig operation is of benefit to any patient who suffers from lack of adequate pulmonary blood flow, provided the structure of the heart is such that it is able to adjust to the altered circulation.Experience has shown that a patient with a tetralogy of Fallot can adjust to the altered circulation. The other types of malformation which have been improved by operation are those with a cardiac contour similar to that of a tetralogy of Fallot with left axis deviation, those with partial rotation of the heart on its axis, possibly those with “pure” pulmonary stenosis and an auricular septal defect, and a few with unusual arrhythmias. In atypical cases an effort is made to determine whether the condition is such that the patient can be helped by increasing the circulation to the lungs.The six criteria essential for successful operation are (1) the primary difficulty must be lack of adequate pulmonary blood flow; (2) there must be a pulmonary artery to which to anastomose the systemic artery; (3) a systemic artery must be available for the anastomosis; (4) the difference in pressure between the systemic and pulmonic circulations must be sufficiently great for blood to flow from the aorta to the lungs; (5) the structure of the lungs must be such that the patient can tolerate the collapse of one lung and the temporary occlusion of one pulmonary artery; and (6) the structure of the heart must be such that it can adjust to the altered circulation. The methods for the determination of each of these factors are discussed.In an analysis of the structure of the heart it is emphasized that (1) venous blood must be directed to the systemic circulation, (2) the increased volume of oxygenated blood which is returned from the lungs must be able to reach the aorta; (3) the structure of the heart must be such as to permit the continuous circulation of the blood at an accelerated rate; (4) the structure of the heart must also be such that the operation does not cause progressive cardiac enlargement. Each of these factors is analyzed.The effect of the altered circulation on the size of the heart is discussed in the light of the long-time results of the operation. Less than 5 per cent of the patients have shown progressive cardiac enlargement or died of cardiac failure. Thirty per cent have shown no increase in heart size. Thirty per cent have shown increase in heart size during the first three weeks after operation and then have adjusted to the load, and 30 per cent have shown cardiac enlargement between the time of discharge and the six-month checkup and thereafter have shown no further increase in heart size.In general, the results from the use of the subclavian artery, as estimated by the oxygen saturation of the arterial blood, the red blood cell count, and the hemoglobin level, have been as beneficial as when the innominate artery has been used for the anastomosis and, moreover, this former group of patients has shown less increase in the size of the heart.A child with a tetralogy of allot has a 90 per cent chance of being greatly improved by the operation and an equally good chance of maintaining that improvement.