Restless leg syndrome and slow coronary flow. Is it inflammation or autonomic nervous system?

To the Editor,

Erden et al. (1) recently published a very interesting paper in the Anatolian Journal of Cardiology 2014; 14: 612-6 entitled “Association between restless leg syndrome and slow coronary flow,” which suggests an association between the coronary slow flow (CSF) phenomenon and restless leg syndrome. The article showed that patients with the CSF phenomenon were more likely to suffer from restless leg syn- drome compared to subjects with normal coronary flow. Although, I appreciate the authors for their work, there are some issues that need to be clarified in order to glean more data from the article. The definition of CSF relies upon TIMI frame count (TFC), which varies depending on the image acquisition rate. The authors chose a recording speed of 25 frames/s. Still, they defined CSF according to the criteria based on the reference values of Gibson et al. (2). “a TFC greater than two standard deviations from the normal range for a particular coronary artery.”

Gibson used a frame rate of 30/s. Thus, the authors could have underestimated TFC. I believe that they need to multiply their corrected TFC with a factor of 1.2 in order to find the real corrected TFC, which may render some of their normal patients into a group of CSF (2, 3). It would be appropriate to know the mean cTFC values of patients with the CSF phenomenon and those of the normal patients in this regard. Even though the authors reported the overall prevalence of restless leg syndrome, it would be useful to know how many patients with and without the CSF phenomenon had restless leg syndrome. In our current practice, we do not come across patients having both the CSF phenomenon and restless leg syndrome, thus, they may have mild symptoms. Was there any association with symptom severity and TFC? We previously showed that patients with the CSF phenomenon had attenuated heart rate recovery, suggesting impaired vagal activation of the cardiovascular system (4). Therefore, we agree with the authors that the common link between the CSF phenomenon and restless leg syndrome is the probably autonomic nervous system.