Special Lecture 11/08/2013. Hypertension Dr. HN Mayrovitz

Transcription

1 Special Lecture 11/08/2013 Hypertension Dr. HN Mayrovitz

2 Arterial Blood Pressure (ABP) Major Factors Summarized Sympathetic Hormones Arteriole MAP ~ Q x TPR + f (V / C) SV x HR Renal SBP

3 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 MAP < > 120 If DBP is normal but SBP is high then called Isolated Systolic Hypertension Decreased Arterial Compliance

4 Specific Known Hypertension Causes (Secondary Hypertension) ~ 10 % of Hypertension Patients Remainder Essential HTN (Primary HTN)

5 Specific Known Hypertension Causes (Secondary Hypertension Renal) Renovascular Large vessel (stenosis) Glomerular disease Kidney Diabetic Nephropathy Small vessel Polycystic kidney disease

6 Specific Known Hypertension Causes (Secondary Hypertension Other) Overproduction of: adrenal Cortisol (pituitary/adrenal tumor Cushings) adrenal E or NE (adrenal tumor Pheochromocytoma) thyroid hormones (Hyperthyroidism) parathyroid hormones (Hyperparathyroidism) aldosterone (adrenal tumor Aldosteronism) Aortic coarctation (narrowed aorta) Pregnancy induced (preeclampsia)

7 Some ABP Determinants TPR Blood Volume Vascular 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

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

11 Renin Angiotensin Aldosterone System Volume and ABP Changes via Effects of: Renin Angiotensin Antiduretic Hormone (ADH) Aldosterone

12 GFR

13 General Renal Effects Changes in renin output change circulating levels of angiotensin BP Q renin Kidney Changes in Urine Output Regulate Vascular Volume Na + controls ADH H 2 O Follows Na + urine Na + H 2 0 BP

14 1. Renin Angiotensin Main Pathways

15 Main Angiotensinogen Renin Regulation Liver (2) Baroreceptor like activity P TM + Renin Granular cells renin Granular cells a.a. Renin Angiotensin renin Half lives Main Pathways Renin Aldosterone ~ 15 min Ang II <1 min +TPR Angiotensin II (Ang II) Angiotensin Converting Enzyme (ACE) ACE lung (1) +Sympathetic +Renin a.a. Kidney 1 receptors Na + secretion Ang II Ang I Afferent arteriole Ang I ACE Intra renal Angiotensin I (Ang I) Endothelial Cells (EC) EC ACE

16 2. Include Aldosterone as a Modulator of Na + Retention and Urine Output

17 Liver Angiotensinogen Granular cells renin a.a. Adrenal Cortex Ang II Angiotensin II (Ang II) Aldosterone Promotes renal Na + retention Angiotensin Converting Enzyme (ACE) ACE lung Kidney Na + secretion Ang II Ang I Afferent arteriole Ang I ACE Intra renal Angiotensin I (Ang I) Endothelial Cells (EC) EC ACE

18 3. Include Effects of Antidiuretic Hormone ADH=Vasopressin as a Modulator of H 2 O Excretion

19 Liver Angiotensinogen Hypothalamus Adrenal Cortex Ang II Angiotensin II (Ang II) Aldosterone Promotes renal Na + Angiotensin Converting Enzyme (ACE) ACE lung Ang II Ang I Afferent arteriole retention Kidney Antidiuretic Ang I Na + Hormone secretion ACE Intra renal Posterior Pituitary (ADH) (Vasopressin) Retain H 2 O + TPR

20 Non invasive Indirect Measurement Oscillographic Auscultation

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

22 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)

23 Central Aortic Pressure

24 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? 24

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

26 Transmission and Reflection of Pulses

27 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!

28 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,

29 Earlier Reflection Arrival 110 mmhg Systolic Peaking Increased Ventricular Systolic Loading Reduced Diastolic Pressure 70

30 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 )

31 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

32 QUESTIONS?