Open heart surgery was performed without perfusion under deep hypothermia in 343 patients with congenital heart defects aged from 1 year 3 months to 44 years. Cooling to a temperature of 26-250C in the oesophagus was achieved by covering the body with crushed ice. The patients were maintained under superficial ether narcosis and they were given morphine (0 5 mg/kg) and tubocurarine (0-5-1l0 mg/kg). The duration of circulatory arrest was 30 minutes in 190 and longer in 153 patients-60-77 minutes in 10 patients. It took an average of7-6 minutes for resumption of normal cardiac activity after circulatory arrest prolonged beyond 60 minutes. Of the 343 patients operated on 32 (9-3%) died. Analysis ofthe mortality pattern showed that patients with acute cardiac insufficiency contributed most to the total number of deaths (19 patients, 5 5%); those with pulmonary oedema ranked second (4 patients, 1 2%) and those with brain oedema third (3 patients, 0-9%). Neurological complications were observed in 13 patients (3-8%). Their frequency was significantly related to the duration of circulatory arrest. Circulatory inadequacy in patients with poor myocardial function who had undergone extensive repair appeared to be a contributory factor. The results obtained without perfusion under deep (26-250C) hypothermic protection suggest that 75 minutes is a safe time, in terms of brain damage, for circulatory arrest. Under these conditions complex cardiac defects can be repaired.

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A stereotypic angiospasm develops in intraorganic arteries during coarctation of the aorta, which is characterized by different functional impacts: resistance in the basin of elevated vascular pressure and pressure and bloodflow regulation in the hypotension basin. The most marked structural changes are observed in the renal and coronary arteries. Changes in the small coronary arteries are mainly due to myocardial hypertrophy, whereas in the larger ones they are caused by the increased pressure transferred from the aorta. The degree of structural changes in the larger coronary arteries is greater than in the small arteries.

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