Background: There is still controversy regarding the benefits of off-pump CABG and the stress that these procedures impose on the cardiac surgeon has not been previously studied. We sought to investigate whether off-pump operations are more demanding for the cardiac surgeon compared to the on-pump by evaluating the stress level by the cardiac variability indices. Methods: The heart rate variability indices, including the low frequency (LF), high frequency (HF), and low frequency/high frequency ratio (LF/HF), as well as heart rate (HR) were recorded throughout 17 on-pump and 16 offpump coronary artery bypass grafting (CABG) operations for an experienced cardiac surgeon. The operations were divided into six phases to indicate the most important surgical moments, which were subsequently compared between the two types of procedures. Results: There was a statistically significant difference (P-value<0.0001) in the surgical phases in terms of the LF, HF, LF/HF ratio, and HR. The HF, LF/HF and HR were also statistically significantly different with respect to the two types of surgeries (P-value < 0.01). The LF, however, did not show a statistically significant difference (P-value = 0. 485). The LF/HF in the off-pump CABGs showed a significant increase during posterior distal anastomosis and it thereafter declined gradually to its base level by the time of proximal anastomosis. The LF/HF in the on-pump CABGs showed an increase at the time of cannulation and cardiopulmonary bypass and it decreased afterwards to its base level by the time of posterior distal anastomosis and remained almost constant until the end of the operation. Conclusion: Our results indicated that the stress level of the surgeon is higher when performing off-pump operations compared to on-pump procedures; this was manifested by the difference in the heart rate variability indices.
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