Fortunately, many noninvasive tests exist that will determine cardiovascular (CV) pathology before clinical coronary heart disease (CHD). One of the best validated early detection tests for functional abnormalities of the endothelium is the EndoPAT, which determines endothelial function and dysfunction¹,²,³,⁴,⁵ (Figure 11.1). The EndoPAT measures postocclusion brachial artery hyperemia, which is an excellent indirect measure of nitric oxide bioavailability and endothelial dysfunction in the coronary arteries The EndoPAT predicts accurately the future risk for hypertension, CHD, unstable angina, cardiovascular disease (CVD), congestive heart failure (CHF), myocardial infarction (MI), cardiac death, hospitalization, coronary artery bypass graft, stent restenosis, the presence of plaque in the coronary arteries that are rupture prone, peripheral arterial disease (PAD), and cerebrovascular accidents (CVAs) beyond the Framingham risk scoring (FRS).¹,²,³,⁴,⁵

In a study of 528 patients with high risk for CV events over 5 years, the EndoPAT reactive hyperemia index (RHI) was measured before and after coronary angiogram.⁴ The RHI, brain natriuretic peptide (BNP), and CV score by SYNTAX were independent risk predictors for all future CV events such as MI, CV death, unstable angina, ischemic CVA, coronary artery bypass graft, CHF, and PAD. When RHI was added to FRS, BNP, and SYNTAX, the net reclassification index was significantly improved by 27.5 % with a significant increase in the
C-statistic from 0.728 to 0.766. A normal RHI is over 1.67.⁴,⁵ An index of 1.67 has sensitivity of 82% and specificity of 77% to diagnose coronary endothelial dysfunction and highly correlates to brachial artery flow mediated vasodilation (r = .0.33-0.55).