The Influence of Insulin Resistance, Obesity, and Diabetes Mellitus on Vascular Tone and Myocardial Blood Flow

Abstract

Among individuals with cardiovascular risk factors, reductions in coronary vasodilator capacity with or without diabetes mellitus (DM) carry important diagnostic and prognostic information. Positron emission tomography (PET) myocardial perfusion imaging in concert with tracer kinetic modeling allows the assessment of absolute regional myocardial blood flow (MBF) at rest and its response to various forms of vasomotor stress. Such noninvasive evaluation of myocardial flow reserve (MFR) or the vasodilator capacity of the coronary circulation expands the possibilities of conventional scintigraphic myocardial perfusion imaging from identifying flow-limiting epicardial coronary artery lesions to understanding the underlying pathophysiology of diabetic vasculopathy, microcirculatory dysfunction, and its atherothrombotic sequelae. Invaluable mechanistic insights were recently reported with PET by unraveling important effects of insulin resistance, obesity, and DM on the function of the coronary circulation. Such noninvasive assessment of coronary circulatory dysfunction enables monitoring its response to antidiabetic medication and/or behavioral interventions related to weight, diet, and physical activity that may evolve as a promising tool for an image-guided and personalized preventive diabetic vascular care. Whether PET-guided improvement or normalization of hyperemic MBF and/or MFR will translate into improved patient outcome in DM is a laudable goal to pursue next.

Clinical Quantification of Myocardial Blood Flow Using PET: Joint Position Paper of the SNMMI Cardiovascular Council and the ASNC

“…• In general, hyperemic MBF and MFR are relatively preserved for coronary lesions with less than 70% angiographic stenosis or with preserved fractional flow reserve (FFR) (.0.8) (45,47,51,52,(85)(86)(87)(88)(89)91,141,142). However, both may be reduced even in the absence of overt obstructive stenosis, especially in higher-risk subgroups (e.g., diabetes and prediabetic states (143)(144)(145)(146)(147)(148)(149)(150)(151)(152)(153)(154), hypertension (155)(156)(157)(158), dyslipidemia (159)(160)(161)(162)(163), and chronic kidney disease (109,110,164,165)). • Hyperemic MBF and MFR are consistently reduced in lesions with greater than 70% luminal narrowing or those with abnormal FFR (45,47,51,52,(85)(86)(87)(88)…”

Relationship between Glycated Haemoglobin and Complexity of Coronary Artery Disease in Diabetic Patients

“…From the baseline diagnostic angiogram, each coronary lesion producing ≥ 50% diameter stenosis in vessels ≥ 1.5 mm had been scored separately and added together to provide the overall Syntax score, which had been calculated using the Syntax score algorithm [12] . Syntax score was used to evaluate the complexity of coronary artery lesions.…”

Relationship between HgbA1c and Myocardial Blood Flow Reserve in Patients with Type 2 Diabetes Mellitus: Noninvasive Assessment Using Real-Time Myocardial Perfusion Echocardiography

“…Cardiovascular disease is the leading cause of death in T2DM patients. Antecedent to and associated with epicardial coronary artery stenosis, T2DM patients develop abnormal microvascular function in systemic circulatory beds, including those of the myocardium [1–4]. Glycosylated hemoglobin (HgbA1c) has been established as a risk factor for T2DM patients developing microvascular atherosclerosis [5].…”