Aims In this study we investigated the relationship between cardiovascular instability and the size of the developed ischaemic lesions during carotid stent implantation by diffusion-weighted (DWI) magnetic resonance (MR) examination. Material and methods We retrospectively analyzed anaesthesia reports and follow-up MR examinations after stent implantation of 192 patients in a 3-year period. Nineteen aspects of cardiovascular status were analyzed. We registered the duration of the intervention, low and high blood pressure (BP) values during anaesthesia and heart rates. The fluctuations of BP and heart rate and the time of their compensations after the stent expansion were also recorded. Values were compared with the number and the size of ischaemic lesions on DWI scans. We used Spearman and Kendall rank correlations and Welch’s tests for statistical analysis. Values of p ≤ 0.05 were considered as statistically significant. Results Decreased heart rate significantly correlated with the number ( p = 0.0123) and size ( p = 0.00323) of ischaemic lesions during stent expansion. Other cardiovascular parameters did not show any significant correlations. Conclusions Our results indicate that only heart rate attenuation affects the size of ischaemic lesions; thus the prevention of bradycardia is highly important.