Adobe Systems Physiology department 1 Arterial stiffness. Adobe Systems Physiology department 2 Oral exam questions ̶Arterial elasticity – significance ̶Arterial pulse, pulse wave Adobe Systems Define footer – presentation title / department 3 ̶Mr. Folkow - 19th century – added physical characteristics to individual sections of the vascular system (aorta – compliance; ̶ arterioles – resistance; veins – capacity) ̶ ̶Basic relationship: blood pressure is a function of SV and PO ̶Compliance: ∆V / ∆P ̶ Adobe Systems Physiology department 4 Factors of arterial stiffness changes ̶Elastin degradation ̶Collagen deposition ̶Endothelial dysfunction ! Adobe Systems Physiology department 5 Complications of the higher arterial stiffness Adobe Systems Physiology department 6 Pulse wave Reflected wave Forward systolic wave t [s] P[mmHg] Adobe Systems Define footer – presentation title / department 7 ̶Reflected wave increases = augments blood pressure in the aorta ̶Physiologically: in young people, the reflected wave mainly affects the diastolic pressure, which increases – and thus contributes to better filling of the coronary circulation and better nutrition of the endocardium ̶ ̶ ̶ Adobe Systems Physiology department 8 Pulse wave Reflected wave Forward systolic wave t [s] P[mmHg] t [s] P[mmHg] SBP/P1 P2 DBP PP=SBP – DBP mBP=DBP+1/3PP AP=P2 – P1 SBP – systolic blood pressure, DBP – diastolic blood pressure, P1 – pressure at peak of systolic flow, P2 – pressure of the reflected wave, PP – pulse pressure, mBP – mean blood pressure, AP – augmented pressure Adobe Systems Physiology department 9 Pulse wave at different vascular segments •If the aorta was an long open-ended tube providing a simple resistance to flow (i.e., there was no wave reflection), then: •The pressure wave in the aortic root would show a single peak for each contraction. If we connect the network of arteries with all its bifurcations and vascular beds, then … as this primary wave travels along the arteries it will generate reflected waves from each bifurcation and from the peripheral vascular beds. … all these small reflected waves return to the heart, summing to create a reflected wave as shown, starting even before the end of systole •Pressure in the aortic root is the sum of the outgoing and reflected wave (the green wave) •Note: importantly how the reflected wave boosts the coronary artery perfusion pressure - the aortic root pressure - during diastole when over 95% of perfusion of the sub-endocardium takes place Adobe Systems Define footer – presentation title / department 11 ̶In older people, the arteries are stiffer and peripheral resistance is higher, the reflected wave reaches the aorta earlier, still at the time of systole and is absent in diastole – therefore they have high systolic pressure and low diastolic pressure – isolated systolic hypertension ̶ ̶ ̶ •If the patient arteries get stiffer…. • then pulse wave velocity increases, and reflected wave arrives back at the heart sooner. •Now there is a very different aortic root pressure waveform (green wave). • As a result of this, there are three important clinical implications. •First, the central systolic pressure and central pulse pressure is increased. • An increase in the central pulse pressure that stresses cerebral blood vessels increases stroke risk • NOTE: this change in central systolic pressure can occur without any changes occurring in peripheral systolic pressure. •Second, there is an increase in left ventricular load (LV load). • Increase in LV load accelerates increase in LV mass and increases LV hypertrophy • The area under the pressure-time curve during systole is by definition LV load. • This increase in LV Load (late systolic “afterload”) is shown by the black arrowed region • •Third, the pressure that is perfusing the coronary arteries during the critical diastole period is reduced, increasing the risk of myocardial ischemias. •CONCLUSION: Increasing arterial stiffness independ-ently increases the risk of all three major cardiovascular outcomes. Adobe Systems Physiology department 13 Sex differences in mechanisms of arterial stiffness ECM - extracellular matrix; VSMC - vascular smooth muscle cell; eNOS - endothelial NOS; NADPH - NAD phosphate oxidase; BH(4) - tetrahydrobiopterin; SMC‐MR - smooth muscle cell mineralocorticoid receptor; AT1R - angiotensin II type 1 receptor; EC‐MR - endothelial cell mineralocorticoid receptor; ENaC - epithelial sodium channel. Adobe Systems Physiology department 14 PWV measurement – Sphygmography in practicals A highly compliant aorta has a relatively low PWV (< 6 m/s) Adobe Systems Define footer – presentation title / department 15 Use in clinical practice ̶Non-invasive investigation of arterial stiffness is gradually moving from the position of experiments to clinical practice ̶Started thanks to new recommendations of the European Hypertensive Society in Milan in 2007 – pulse wave velocity testing was included among the main diagnostic methods and in the process of determining the risk of cardiovascular disease + evaluation of the effect of treatment of essential hypertension ̶ ̶ ̶ ̶ Adobe Systems Define footer – presentation title / department 16 ̶Arterial stiffness expresses damage to their walls by risk factors over a long period of time (years), while blood pressure values fluctuate physiologically and may not reflect the degree of damage to the vascular wall ̶ ̶Using techniques for measuring the pulse wave velocity, it is possible to calculate the central aortic pressure, which is a stronger prognostic parameter than the pressure measured on the brachial artery and more accurately expresses the load on the heart ̶ ̶ Adobe Systems Define footer – presentation title / department 17 ̶Changes in arterial stiffness are clinically imperceptible ̶ ̶Methods are a modern trend for determining the risk of cardiovascular disease – ̶risk of developing hypertension ̶risk of sudden cardiac death ̶ ̶ Adobe Systems Define footer – presentation title / department 18 ̶Device Sphygmocor – company: AtCor Medical, Australia Adobe Systems Physiology department 19 Adobe Systems Define footer – presentation title / department 20 ̶Device VaSera, company: Fukuda Denshi, Japan Adobe Systems Physiology department 21 Cardio-ankle vascular index – CAVI - measurement Adobe Systems Physiology department 22 CAVI measurement Adobe Systems Physiology department 23 Thank you for your attention Find a mistakes))))) Adobe Systems Physiology department 24 Adobe Systems Physiology department 25 Ultrasound measurement age IMTR (mm) IMTL (mm) Adobe Systems Physiology department 26 Ultrasound measurement (β – index).