Special Lecture 10/28/2012 HYPERTENSION Dr. HN Mayrovitz
Special Lecture 10/28/2012 Arterial Blood Pressure (ABP) - Definitions ABP Review Indirect Oscillographic Method Resistance (R), Compliance (C) and Volume as Determinants of ABP Hypertension Secondary and Primary Central ABP and Role of Reflection Differential Effects of R and C Changes on Systolic and Diastolic Pressures Dr. HN Mayrovitz 2011
Arterial Blood Pressure (ABP) SV P Systolic Pulse Pressure Diastolic PP Mean and Pulse Pressure Ps Pd MAP MAP = Pd + 1/3PP Dr. HN Mayrovitz 2012
Non invasive Measurement Sphygmomanometer Oscillographic
ABP via Oscillographic Method Cuff pressure Near Systolic start of oscillations Pressure oscillations in cuff MAP = 80 + 30/3 = 90 mmhg cuff
systolic Cuff Pressure mean diastolic A S /A m = 0.55 A D /A m = 0.85 A m Sensor Pressure (mmhg) Cuff Pressure (mmhg)
Some ABP Determinants Resistance Volume Compliance
Resistance as a ABP Determinant CARDIO Cardiac PUMP Pump P MAP = CO x TPR V V Aorta Vena Cava Vein Venule Pre-Capillary Sphincter/ Terminal Arteriole Capillaries Small Artery Arteriole Large Artery Capacitance Exchange Resistance Distribution
Blood Volume as an ABP Determinant 2. F S + Volume + CVP + Filling + SV + CO + MAP V CARDIO Cardiac PUMP Pump P V 1. Mechanical + Volume + Pressure Compliance Related V/C Dr. HN Mayrovitz 2012
Compliance as an ABP Determinant +Systolic + dv/dt + SV -C Low C V CARDIO Cardiac PUMP Pump P V P = V / C SV Higher C P = SV / C Mainly Systolic and Pulse Pressure Effects Dr. HN Mayrovitz 2012
Specifically Known Hypertension Causes (Secondary Hypertension) ~ 5-10 % of Hypertension Patients Remainder Essential HTN
Hypertension = High Blood Pressure So.. What s High? Hypertension BP CLASSIFICATION Normal Prehypertension Stage 1 Hypertension Stage 2 Hypertension SBP (mmhg) < 120 120-139 140-159 >= 160 DBP (mmhg) AND <80 OR 80-89 OR 90-99 OR >= 100 If DBP is normal but SBP is high then called Isolated Systolic Hypertension Decreased Arterial Compliance Dr. HN Mayrovitz 2012
Central Aortic Pressure
Most heart-related effects of elevated BP are due to increased central aortic pressure But BP is measured here! Age-Related Issues Artery stiffening Decreased Compliance Increased wave speed Earlier return of reflected pressure So, what are we missing? 14 Dr. HN Mayrovitz 2012
Why do shapes & values differ? What adequately represents central aortic pressure? Values and Shapes Differ by site
Transmission and Reflection of Pulses
Transmission and Reflection of Pulses Compliance S 0 s 0 ~ 1. Pulse wave-speed (S 0 ) is inverse to Compliance (C) Stiffer arteries ~ higher speed 1 C 2. Reflections mainly at arterial branch points Resistance 3. Pulses at any point in the artery are the algebraic sum of forward and reflected pulses Composite is what is measured! Dr. HN Mayrovitz 2012
Pulse Wave Velocity (PWV) Pulse Wave Velocity (m/s) 14 13 12 11 10 9 8 7 6 5 4 BP-Normal BP-HTN 1 BP-HTN 2/3 PWV Increases with age At any age increases with BP 20 25 30 35 40 45 50 55 60 65 70 75 80 Median Age (years) Adapted and Modified from European Heart Journal (2010) 31, 2338 2350
Earlier Reflection Arrival 110 mmhg Systolic Peaking Increased Ventricular Systolic Loading Reduced Diastolic Pressure 70 Dr. HN Mayrovitz 2012
Summary of Major Aspects 110 mmhg Systolic Peaking (stroke risk) Increased ventricular systolic afterload (LVH risk) Normal Composite (P m ) Reduced diastolic Pressure (Ischemic risk) 70 Earlier Reflection Normal Reflection (P b ) Dr. HN Mayrovitz 2012
So Standard BP by sphygmomanometry, though important and clinically useful only tells PART of the story Aortic Central Pressure may be a more accurate risk assessment Reasons have to do with pressure wave interactions that are most directly influenced by: A. Pulse wave speed (Artery compliance) B. Reflection amplitudes (Vasoconstriction state) Both tend to increase with ageing and HTN Dr. HN Mayrovitz 2012
Effects of R and C changes on Systolic and Diastolic Pressure SIMULATION RESULTS
Arterial Blood Pressure (ABP) SV TPR P C Systolic Pulse Pressure Diastolic SV C TPR Dr. HN Mayrovitz 2012
Pressure Resulting from a Single Simulated Initial Beat Pressure (mmhg) C=100% of Normal Aortic Blood Flow Systolic Pulse Pressure SV Diastolic C TPR Pressure HR = 60
Simulated Compliance Effects
Dr. HN Mayrovitz 2012 Pressure (mmhg) C=100% SV C TPR
Dr. HN Mayrovitz 2012 Pressure (mmhg) C=90% SV C TPR
Dr. HN Mayrovitz 2012 Pressure (mmhg) C=80% SV C TPR
Dr. HN Mayrovitz 2012 Pressure (mmhg) C=75% SV C TPR
Dr. HN Mayrovitz 2012 Pressure (mmhg) C=70% SV C TPR
Effect of Compliance Changes Systolic and pulse pressures increase with decreasing compliance but most times small effect on diastolic pressure 180 160 140 Systolic mmhg 120 100 80 Diastolic 60 40 20 Psys Pdia PP PP 0 60 70 80 90 100 110 % of normal artery compliance
Simulated Resistance (TPR) Effects
Dr. HN Mayrovitz 2012 Pressure (mmhg) C=100% TPR=100% SV C TPR
Dr. HN Mayrovitz 2012 Pressure (mmhg) C=100% TPR=120% SV C TPR
Dr. HN Mayrovitz 2012 Pressure (mmhg) C=100% TPR=150% SV C TPR
Dr. HN Mayrovitz 2012 Pressure (mmhg) C=100% TPR=200% SV C TPR
Effect of TPR Changes Systolic and diastolic pressures increase with increasing TPR but PP tends to decrease. Diastolic Increases more than systolic. 160 140 Systolic 120 mmhg 100 80 60 Diastolic 40 20 Psys Pdia PP PP 0 60 80 100 120 140 160 180 200 220 % of normal TPR
Summary (Kind of) Isolated Systolic HTN BV MAP C SBP & PP CO x TPR SV x HR R artle MAP ~ CO x TPR + f(bv/c) SBP & DBP DBP > SBP PP LESS Essential HTN Dr. HN Mayrovitz 2012
QUESTIONS?