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Comparison of heart rate variability and classic autonomic testing for detection of cardiac autonomic dysfunction in patients with fibromyalgia

Dear Editor, We read with great interest the article entitled ‘Comparison of heart rate variability and classic autonomic testing for detection of cardiac autonomic dysfunction in patients with fibromyalgia’, published in the International Journal of Rheumatic Diseases in 2016 by Lee et al. The study was designed excellently. We congratulate Lee et al. We would like to highlight some points regarding this article. In their study, they mentioned that ‘inclusion criteria were lack of co-morbid conditions or medications that could affect ANS [autonomic nervous system] function including any type of sleeping pills, tranquilizers or antidepressants, for at least 1 month prior to the study; (iii) no evidence of major depression, congenital cardiac disease, coronary artery disease or cardiomyopathies’. It has been shown that hypertension, diabetes mellitus, atrial fibrillation, taking antihypertensive drugs like beta-blockers, angiotensin converting enzyme inhibitor and smoking can alter heart rate variability results. Lee et al. have mentioned only co-morbid conditions or medications that could affect ANS. We could not understand whether hypertension, diabetes mellitus, atrial fibrillation and smoking are co-morbid conditions or not. Because Lee et al. accepted congenital cardiac disease, coronary artery disease or cardiomyopathies as exclusion crteria, additionally, we think diabetes mellitus, hypertension and atrial fibrillation can be accepted as exclusion criteria. The other point is about smoking. Although the authors described patients’ social conditions, such as marital status in baseline characteristics, they did not give any information about smoking, that also can alter the heart rate variability. It is also a social habit. For that reason the issues mentioned previously should be included in the text. A very small point is that, most of the patients with fibromyalgia are women. But it can occur in men also. In our study and Lee et al.’s study, all patients with fibromyalgia are women. It has been shown that sex also can affect heart rate variability. We entitled our study ‘Heart rate turbulence analysis in female patients with fibromyalgia’. In any study in female patients with fibromyalgia, if it is entitled ‘. . .in female patients with fibromyalgia’ it will be an improvement.