Measuring the Nitroglycerine-Induced Vasodilation in Carotid Arteries

Abstract

Introduction: Nitroglycerin is a fast-acting drug that rapidly dilates coronary arteries and thus increases blood flow to these vessels, and increases the blood flow through the lateral vessels to low blood areas. It also reduces both end diastolic pressure and volume of the left ventricular. However, the effect of nitroglycerin on the circulation hemodynamic is not known. Carotid artery is an artery on each side of the head and neck that supplying blood to the brain, face, scalp, skull, neck and meninges. The purpose of this study was to evaluate the influence of the Nitroglycerin on the blood velocity of the carotid artery. Materials and Methods: Right carotid artery (common carotid artery 2 cm before the bifurcation, beginning of the internal and external carotid arteries) of 10 healthy subjects (age, 24±4 years) was scanned longitudinally with an ultrasound system (esaote Mylab 60) equipped with linear probe (4-13 MHz). Pulse wave Doppler images of blood velocity of the carotid arteries were recorded before and after taking a sublingual nitroglycerin pill. The blood velocity waveforms were extracted from sonograms over three cardiac cycles by using a custom analysis programs written in MATLAB. The effect of nitroglycerin on the carotid blood velocity was evaluated. Results: According to the results, the carotid blood velocities changed significantly after administration the nitroglycerin. The peak systolic blood flow velocity of the CCA and ICA decreased 15% ± 9 and 20%± 16 after taking the pill, respectively. The end diastolic velocity of the blood flow in the CCA and ICA decreased 19% ± 12 and 16%± 11, respectively. The dicrotic notch of the CCA and ECA descended 24% ± 12 and 24% ± 22, respectively. There was not shown significant difference in the heart rate of the subjects before and after nitroglycerin administration. Conclusion: According to presented results, nitroglycerin reduces both peak systolic and end diastolic blood velocity of the CCA and ICA. It seems that this hemodynamic change in the blood velocity caused by nitroglycerin might be a fast response of the carotid artery to the release of vasoactive substances such as nitric oxide (NO) from the endothelium.