Effect of fatty acids on the ventricular arrhythmia threshold in the isolated heart of the rabbit.

1 The ventricular arrhythmia threshold (VAT) was measured in the isolated Ringer-perfused rabbit heart (Langendorff preparation) by applying a single 10 ms square-wave pulse of current to the left ventricle during the vulnerable period of the late systole under normoxic and hypoxic conditions. 2 The sodium salt of the fatty acid was bound to albumen and incorporated in the Krebs-Henseleit solution which was maintained at 37 degrees C and gassed with 95% O2 and 5% CO2 (normoxia) or 5% CO2 in air (hypoxia). 3 Saturated fatty acids failed to alter the VAT under normoxia. 4 Naturally occurring long-chained saturated and mono-unsaturated fatty acids with chain lengths varying from 14 to 20 carbons, but not the 12 carbon lauric acid, potentiated the effect of the hypoxia in lowering the VAT. 5 Short-chained 8 and 10 carbon saturated and long-chained polyunsaturated fatty acids antagonized the effect of hypoxia on the VAT. 6 In addition the polyunsaturated acids antagonized the potentiating effect of the long-chained saturated and mono-unsaturated acids on the hypoxia in lowering the VAT. 7 The fatty acids did not alter the duration or type of the induced arrhythmia.