Aim: Chronotropic incompetence and a delayed HR recovery reflect autonomic dysfunction and predict adverse cardiac prognosis. Since cardiac involvement is known in colorectal cancer survivors, we aimed to investigate these responses during exercise.

Methods: Nineteen patients who survived from CRC (13 men, 6 women, 53.78±11.23 years) and fifteen healthy adults (11 men, 4 women, 50.06±10.66 years) were included in the study. Cardiopulmonary exercise test (CPET) performed with Modified Bruce protocol was performed. HRR was calculated as the difference between the HR at peak exercise and at first minute into the cooling period. A cut-off point of ?12 beats was taken as an abnormal HRR. Chronotropic response index (CRI) and was calculated as: CRI=((peak?HR?resting?HR)×100)/((220?age)?(resting?HR)). A cut-off point of  <80 was taken as an incompetence.

Results: While five (26.31%) of the patients had abnormal HRR, two (13.33%) of the healthy participant had abnormal HRR. Seven (36.80%) of the patients had a low CRI, while three (20%) of the healthy participant had a low CRI. While three (15.78%) of the patients had both abnormal HRR and low CRI, one (6.67%) of the healthy participant had both abnormal HRR and low CRI. Although the number of affected CRC survivors was higher, there was no statistically significant difference (p>0.05).

Conclusion: Although the mechanisms underlying impaired cardiac autonomic control during exercise are not yet fully known, slower heart rate recovery after exercise is indicative of worse autonomic function. There is a need for more studies showing the effects of exercise, which are effective on autonomic function and cardiac response on these patients.