Effect of QTc interval on prediction of hypotension following subarachnoid block in patients undergoing cesarean section: A comparative study

Background: Previous studies have revealed that QTc interval is prolonged in pre-eclamptic parturients. Another study reflected the relationship between the sympathetic block and QTc interval. Subarachnoid block was safely administered in patients with severe pre-eclampsia. It has also been noticed that hypotension in response to spinal anesthesia is relatively less in pre-eclamptic patients than normal parturients. Aim: To compare the QTc values in normal and pre-eclamptic term parturients and to establish whether any correlation exists between the QTc interval and the systemic hypotension following subarachnoid block. Materials and Methods: Twenty-five pre-eclamptic patients (Group A) and 25 normotensive patients (Group B) were included in this study. QTc interval was recorded for each patient before subarachnoid block for cesarean section. Changes in arterial blood pressure and heart rate were measured in both the groups and compared. Results: Baseline QTc was significantly higher in the pre-eclamptic group (Group A: 0.47 ± 0.11) with that of control (Group B: 0.36. ± 0.02). Significant fall in blood pressure was seen only in one group with QTc between 0.38 and 0.39 in Group A. Hypotension was significantly more in normotensive mothers (Group B). However, no statistical correlation could be drawn from this study between QTc interval and hypotension, although a trend toward increasing hypotension with decreasing QTc was present. Discussion : The prolonged QTc intervals seen in pre-eclamptic patients may be due to the contributory effects of sympathetic hyperactivity, hypertension, and hypocalcemia secondary to underlying vasoconstriction. Decreased vagal control of heart in pre-eclampsia may have produced the difference in change in hemodynamic status between pre-eclamptic and normotensive parturient. Conclusion: Any consistent correlation between QTc and hypotension following subarachnoid block could not be derived from this study. To achieve a statistical significance a larger sample size may be required.