The relationship between nitrate induced headache and whole blood viscosity: an observational prospective study.

Nitrates are one of the most prescribed medications in the treatment of angina pectoris today. Headache is the most common side effect of nitrates, and there is limited prospective data on the determinants of this effect. Our aim in this study is to open a foresight window for clinicians in clinical practice by explaining the possible relationship between nitrate induced headache (NIH) and whole blood viscosity (WBV). After coronary revascularization treatment, 869 patients with angina who were prescribed nitrate preparations were divided into groups according to the development of headache or not, and categorized according to the four-grade scale (4GS) level. Those who had no headache during nitrate use were graded as Grade 0, those who felt mild headache were Grade 1, those who felt moderate headache were Grade 2, and those who described severe headache were graded as Grade 3. The groups were compared according to WBV values. A total of 869 participants were included in the study. Most patients (82.1%) experienced any level of headache. Headache severity was correlated with both WBV at HSR (r=0.657, p<0.001) and WBV at LSR (r=0.687, p<0.001). In multivariate analysis, WBV was determined as an independent predictor of headache experience. WBV predicted NIH with 75% sensitivity and 75% specificity at HSR and 77% sensitivity and 77% specificity at LSR. WBV seems to be one of the major determinants for NIH. WBV may be a guide for initiating alternative antianginal drugs without prescribing nitrates to the patient in order to increase patient compliance.