*3.1.5. Fingertip digital thermal monitoring (DTM)*

Fingertip digital thermal monitoring (DMT) of vascular reactivity represents a noninvasive, reproducible, operator-independent technique based on changes in fingertip temperature during cuff-occlusive reactive hyperemia [119]. This method relies on a premise that changes in fingertip temperature during and after vascular occlusion that reflects changes in blood flow and thus microvascular and endothelial function [120]. So far, studies have reported that vascular function measured by DTM correlate with Framingham Risk Score and coronary artery calcium score (a measurement of the amount of calcium in the walls of the coronary arteries using a special computed tomography (CT) scan of heart) independently of age, sex, and traditional cardiac risk factors [121]. Although clinical implications of DTM are promising, more studies on the mechanisms mediating this vascular response and large prospective trials are needed to establish the real research and clinical value of this method.

response to nitroglycerine is used [127, 129, 130]. Nitroglycerine-induced vasodilation was significantly reduced in patients with cardiovascular disease [129]. Additionally, nitroglycerine-induced vasodilation was impaired in patients with atherosclerosis [131]. FMD should be interpreted as an index of vascular function reflecting both endothelium-dependent and -independent vasodilation in individuals with impaired nitroglycerine-induced vasodilation [129]. Furthermore, coronary artery dilation in response to nitroglycerine is impaired in patients with coronary heart disease which predicts long-term atherosclerotic disease progression and cardiovascular event rate [132]. These findings suggest that nitroglycerine-induced vasodilation *per se* may be a marker of the grade of atherosclerosis and predictor of cardiovascular events. However, the relationship between nitroglycerine-induced vasodilation and the risk for future cardiovascular events should still be

The Markers of Endothelial Activation http://dx.doi.org/10.5772/intechopen.74671 403

Since FMD requires an expensive ultrasound system and high levels of technical skills, a novel method for measurement of endothelial function, namely, measurement of enclosedzone flow-mediated dilatation (ezFMD) was developed [133]. ezFMD is a noninvasive method which assesses the level of vasodilatation from the oscillation signals transmitted to a sphygmomanometer cuff attached to the upper arm. In patients with cardiovascular diseases, ezFMD was significantly lower than in age- and gender-matched healthy individuals. In addition, cardiovascular risk factors were independent predictors of ezFMD. ezFMD was significantly correlated with conventional FMD [134]. Conventional measurement of FMD by ultrasound is measured by the change in vascular diameter, whereas ezFMD is based on the change in vascular volume. Both methods are equally valuable for assessing endothelial function, however, measurement of ezFMD is easier and less biased than measurement of

Quantitative coronary angiography (QCA) or intravascular ultrasound are methods for imaging vasomotor responses of epicardial coronary arteries, which enable tracing of changes in vessel diameters in response to endothelium-dependent interventions, e.g., intracoronary infusion of drugs or substances, such as acetylcholine [2]. Vessels with an intact endothelium vasodilate in response to ACh infusion, whereas segments with dysfunctional endothelial cells display abnormal vascular response [2]. Estimation of coronary endothelial function with intracoronary ACh provides diagnostic and prognostic data in patients with suspected

Some of advantages of this method is direct assessment of the coronary vascular bed and represents gold standard for assessment of epicardial macrovasculature, while its disadvantage is invasiveness and limitation to those patients undergoing coronary angiography [68].

Physiologically, endothelium-dependent vasodilation occurs in response to exercise or tachycardia as a replacement for exercise, but also pacing induced tachycardia, and leads to increased flow-mediated endothelium-dependent vasomotion of the epicardial vessels that is impaired in atherosclerosis [68]. In healthy isolated intramyocardial porcine coronary

*3.2.2. New method for assessment of endothelial function—measurement of ezFMD*

established.

FMD.

*3.2.3. Coronary epicardial vasoreactivity*

coronary microvascular dysfunction.
