Special Lecture 10/28/2012

Transcription

1 Special Lecture 10/28/2012 HYPERTENSION Dr. HN Mayrovitz

2 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

3 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

4 Non invasive Measurement Sphygmomanometer Oscillographic

5 ABP via Oscillographic Method Cuff pressure Near Systolic start of oscillations Pressure oscillations in cuff MAP = /3 = 90 mmhg cuff

6 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)

7 Some ABP Determinants Resistance Volume Compliance

8 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

9 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

10 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

11 Specifically Known Hypertension Causes (Secondary Hypertension) ~ 5-10 % of Hypertension Patients Remainder Essential HTN

12 Hypertension = High Blood Pressure So.. What s High? Hypertension BP CLASSIFICATION Normal Prehypertension Stage 1 Hypertension Stage 2 Hypertension SBP (mmhg) < >= 160 DBP (mmhg) AND <80 OR OR OR >= 100 If DBP is normal but SBP is high then called Isolated Systolic Hypertension Decreased Arterial Compliance Dr. HN Mayrovitz 2012

13 Central Aortic Pressure

14 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

15 Why do shapes & values differ? What adequately represents central aortic pressure? Values and Shapes Differ by site

16 Transmission and Reflection of Pulses

17 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

18 Pulse Wave Velocity (PWV) Pulse Wave Velocity (m/s) BP-Normal BP-HTN 1 BP-HTN 2/3 PWV Increases with age At any age increases with BP Median Age (years) Adapted and Modified from European Heart Journal (2010) 31,

19 Earlier Reflection Arrival 110 mmhg Systolic Peaking Increased Ventricular Systolic Loading Reduced Diastolic Pressure 70 Dr. HN Mayrovitz 2012

20 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

21 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

22 Effects of R and C changes on Systolic and Diastolic Pressure SIMULATION RESULTS

23 Arterial Blood Pressure (ABP) SV TPR P C Systolic Pulse Pressure Diastolic SV C TPR Dr. HN Mayrovitz 2012

24 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

25 Simulated Compliance Effects

26 Dr. HN Mayrovitz 2012 Pressure (mmhg) C=100% SV C TPR

27 Dr. HN Mayrovitz 2012 Pressure (mmhg) C=90% SV C TPR

28 Dr. HN Mayrovitz 2012 Pressure (mmhg) C=80% SV C TPR

29 Dr. HN Mayrovitz 2012 Pressure (mmhg) C=75% SV C TPR

30 Dr. HN Mayrovitz 2012 Pressure (mmhg) C=70% SV C TPR

31 Effect of Compliance Changes Systolic and pulse pressures increase with decreasing compliance but most times small effect on diastolic pressure Systolic mmhg Diastolic Psys Pdia PP PP % of normal artery compliance

32 Simulated Resistance (TPR) Effects

33 Dr. HN Mayrovitz 2012 Pressure (mmhg) C=100% TPR=100% SV C TPR

34 Dr. HN Mayrovitz 2012 Pressure (mmhg) C=100% TPR=120% SV C TPR

35 Dr. HN Mayrovitz 2012 Pressure (mmhg) C=100% TPR=150% SV C TPR

36 Dr. HN Mayrovitz 2012 Pressure (mmhg) C=100% TPR=200% SV C TPR

37 Effect of TPR Changes Systolic and diastolic pressures increase with increasing TPR but PP tends to decrease. Diastolic Increases more than systolic Systolic 120 mmhg Diastolic Psys Pdia PP PP % of normal TPR

38 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

39 QUESTIONS?