Effects of precurarization on the heart measured by systolic time intervals

The effects of precurarization, with or without prior atropine medication, on heart rate, systolic time intervals (preejection period (PEP) and left ventricular ejection time (LVET)) and derivatives from these were studied in 80 healthy patients before minor surgery. Atropine (0.5-0.7 mg i.v.) exerted a vagolytic action with no changes in systolic time intervals. D-tubocurarine (0.5 mg/kg b.w.) did not affect heart rate or systolic time intervals. Both gallamine (0.3 mg/kg b.w.) and pancuronium (0.015 mg/kg b.w.) increased heart rate due to the inherent vagolytic effect. Furthermore, a short-lasting decrease in PEP and an increase in LVET were demonstrated. Consequently, a fall in PEP/LVET and a rise in 1/PEP2 were induced, indicating an increase in cardiac pump performance. These changes were blocked by prior atropine medication, a result which is not easily explainable. Possible clinical implications are discussed.