Arterial Stiffness in Type 1 Diabetes: The Case for the Arterial Wall Itself as a Target Organ

Figure 1. Impact of arterial stiffness on both the macro- and microvasculature. The figure compares a compliant aorta with a stiff aorta. In the left side a compliant (elastic) aorta is represented while the right represents a stiff aorta (vascular aging). Pulse waveform with their respective components of forward wave (FW, left ventricle to peripheral) and backward or reflected wave (BW, peripheral circulation to left ventricle) in both situations are shown. When the aorta is compliant, both components of the pulse wave (forward and backward) are slow and the backward component reaches the left ventricle in diastole with no increase in the physiological aortic pulse pressure and favoring myocardial perfusion (which mainly occurs in diastole). Under these conditions, blood flow reaches the microcirculation of the organs with low resistance and high flow with low pulsability and energy (left side of the figure). When the aorta stiffens, pulse wave velocity increases in both of its components, the forward component increasing the systolic blood pressure and the afterload of the left ventricle (first step towards its hypertrophy and failure) whereas the backward component reaches the left…

Figure 2. The concept of augmentation index and augmentation pressure. The figure shows a pulse waveform with two peaks: P1 is an early systolic peak pressure (derived from the forward component of the pulse wave) whereas P2 is a late systolic peak pressure (derived from the backward component of the pulse wave). Pulse pressure (PP) is the difference between the central systolic blood pressure and the central diastolic blood pressure. PP2 is the pulse pressure of the P2, and PP1 is the pulse pressure of the P1. The augmentation pressure is the difference between the PP2 and the PP1. The augmentation index (AIx) is the augmentation pressure divided by the PP and multiplied by 100 to give as a percentage. When the aorta stiffens, reflected waves arrive earlier in the systole, the P2 value is higher as well as the augmentation pressure and the AIx. As the AIx is highly dependent on heart rate, it should be reported as its value for a heart rate of 75 bpm (AIx75). The assessment of AIx75 requires only one recording site (usually radial or carotid) for recording the pulse waveform with a device provided with a transfer function for calculating the AIx as well as other pulse waveform-derived…

Figure 3. The three layers of the elastic arterial wall are: (1) intima (endothelial cells); (2) media (concentric layers of elastin, fibrillar collagen and other proteins integrating the extracellular matrix (ECM) and vascular smooth muscle cells (VSMCs)); and (3) adventitia (fibroblasts, collagen and, in larger arteries, vasa vasorum). Atherosclerosis initiates in the intima whereas arteriosclerosis (AS) mostly affects the media.