Background Heart rate decrease after exercise, that is associated with reactivation of parasympathetic system, is important, as it is also associated with mortality. Previous studies have shown that this is an independent mortality predictor in patients having no coronary artery disease and having normal left ventricular function. In our study, we aimed to study heart rate recovery (HRR) after exercise in patients having impaired left ventricular function. Methods One hundred and two consecutive patients (68 males, 34 females) requested to perform an exercise stress test were included in our study. Patients were divided into two groups as those having a normal heart rate reserve (Group1, n = 72) and those having an abnormal heart rate reserve (Group2, n = 30). Results In Group1 and Group2, resting heart rate averages were found to be 83.61 +/- 18.01/min and 85.10 +/- 13.40/min, respectively (P > 0.05), and maximum heart rates during exercise were 141.42 +/- 19.70/min and 121.17 +/- 19.01/min while those in Group1 had statistically significantly higher heart rates (P < 0.001). A statistically significant positive association was found in the correlation test carried out between the maximum heart rate during the treadmill exercise test and ejection fraction (EF) value (r = 0.201; P < 0.05). Metabolic equivalents of task values obtained during the treadmill exercise test in Group1 and Group2 were 9.48 +/- 2.28 and 8.36 +/- 2.50, respectively, and the difference between the said values was statistically significant (P < 0.05). Conclusions We believe that the association between low EF and abnormal HRR is worth studying and randomized large-scale studies are needed to determine mortality risk.