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Cardiovascular Physiology A

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1 Cardiovascular Physiology A
HSCI 211

2 Objectives To learn the basic anatomy and physiology of the heart
Muscle/ pump To understand the mechanism for the delivery of oxygen and nutrients to the organs and tissues of the body To become familiar with mechanisms to control blood pressure To understand the process of atheroma formation (Next Class) HSCI 211

3 Outline Needs for energy distribution Anatomy of the heart
The heart as a pump Circulation Introduction to EKGs Blood pressure Atheroma formation (next lecture) HSCI 211

4 The Need for Circulation
All living cells require metabolic substrates (e.g. oxygen, glucose, amino acids) and a mechanism to remove the byproducts of metabolism (e.g. carbon dioxide, lactic acid- stuff we need to remove) In human beings most cells are not in contact with the external environment The ultimate purpose of the cardiovascular system is to facilitate exchange of gases, fluid, electrolytes, large molecules and heat between cells and the outside environment The heart and vasculature ensure that adequate blood flow is delivered to organs so that this exchange can take place. Klabunde, RE Cardiovascular Physiology Concepts Lippincott, Williams and Wilkins, 2005 HSCI 211

5 Exchanges External: Internal: Lungs (oxygen, carbon dioxide)
Gastrointestinal tract- guts (glucose, amino acids, fatty acids, etc. and elimination.) Kidneys (water, electrolytes, and elimination) Skin (water, electrolytes, heat) Internal: Arteries – Arterioles - Capillaries (close to cells for nutrient exchange) – Venules - Veins HSCI 211

6 Capillary – no muscle – where exchanges take place
Test material*** Capillary – no muscle – where exchanges take place - System is very important HSCI 211

7 Circulation Veins Heart Aorta Delivered in parallel to organs HSCI 211

8 HSCI 211

9 Heart Anatomy Heart Muscles Right Atrium Right Ventricle Left Atrium
Left Ventricle Heart Valves: Between the atria and ventricles Right: Tricuspid Left: Mitral Between ventricles and outflow Right: Pulmonic Left: Aortic HSCI 211

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12 Cardiac Cycle Rhythmic contraction of the heart relies on the organized propagation of electrical impulses along its conduction pathway. The electrical impulse spreads along each cardiac cell and rapidly between neighbouring cells Electrical action potential leads to physical contraction of the cardiac muscle cells HSCI 211

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16 Heart Sounds First Heart Sound: Second Heart sound:
Closing of mitral and tricuspid valves and contraction of the Ventricles Second Heart sound: Closure of the Aortic and Pulmonary valves Systole: (Contraction) The time between the 2 heart sounds Diastole: (Relaxation) The time between the second heart sound and the first HSCI 211

17 Electrocardiogram Measures the electrical currents generated by the depolarization and repolarization of the cardiac cells Diagnosis: Rhythms Blockages An indication of heart diseases HSCI 211

18 Not in exam*** HSCI 211

19 Refer to Page 24 in your handout (Chapter 13)
19 HSCI 211 HSCI 211

20 Summary 1 Heart is a very efficient pump
Pump needs a distribution system Arteries Veins… because system is closed Why distribution? Needs a means of carrying blood Cells need O2 & nutrients for metabolisms to work Closed system… Returns deoxygenated blood & metabolites Needs an electrical system To initiate/transmit impulses, create action potentials (AP) to accomplish specific cell function (i.e., pumping action) HSCI 211

21 Summary 2 If you understand the basic elements … then you can appreciate what might go wrong
Problem with Pump – when aging pump doesn’t work well – high salt intake Congenital – perforation of the septal wall and/or malformation of heart vessels Disease – enlargement, thickening Failure of the valves – disease such as syphilis –Leakage – pressure build up behind fluid in lungs/extremities atrial enlargement Blockages Clogged arteries – insufficient fuel – cell death Heart cannot contract Ruptures Aneurysm – weakening aorta Changes over time In flexibility/elasticity of distribution system Electrical Interruptions Conduction blocks – may need pacemaker HSCI 211

22 Summary 3 … then primary care assessment
History – The story Pain on exertion or at rest Shortness of breath, etc. Look – diagnosis Edema – swelling – blood flow doesn’t get pumped back Listen The heart sounds Blood pressure – resistance in the distribution system Feel The pulses ECG Assess the electrical conductivity & efficiency of heart cycle THESE ARE THE BASIC TOOLS FOR THE GPs Obviously more sophisticated methods are needed/available for further investigation HSCI 211

23 Blood Pressure HSCI 211

24 Objectives Review of structure & function
Learn the role of various blood vessels in oxygen and nutrient supply and removal Blood Pressure and its determinants Understand how different factors might influence blood pressure levels Become familiar with mechanisms of controlling blood pressure Learn how blood pressure is measured Hypertension or High blood pressure Impact of hypertension HSCI 211

25 Outline Structure of blood vessels Blood circulation
Capillary exchange Physiologic methods to control blood pressure Blood pressure measurement Causes of altered blood pressure Guidelines for measuring BP Public health consequences of high BP Management of High Blood Pressure – Lifestyle Management of High Blood Pressure – Drug therapy Benefits of treating/controlling High Blood Pressure HSCI 211

26 Normal Arterial Wall

27 Blood Vessel Structure
Intima: Inner Layer – Endothelium and sub endothelial layer-loose connective tissue- Media: Smooth Muscle Adventitia: Fibrous Tissue/Connective tissue HSCI 211

28 Blood Vessel Structure **
Capillary and venules have smooth muscles - FALSE

29 Blood Flow During Rest

30 Capillary Exchange Most capillary exchange is by
diffusion (between cells) or transcytosis (through cells) Gases (O2) (CO2) diffuse freely Capillary filtration and Absorption is by bulk flow: Hydrostatic pressure (pushes) Osmotic pressure (mainly proteins- pulls fluid)

31 HSCI 211

32 Venous Blood Flow Blood vessels are similar
(in reverse) to the arterial system Small very thin-walled venules to larger veins Blood begins at very low pressure Moved by skeletal muscles, respiratory pump Valves prevent backflow HSCI 211

33 *Handling the Overflow
Outflow is greater than inflow Return is helped by the Lymphatic System Lie next to the capillaries Even thinner walls than capillaries Fluid enters (one-way) Empty into venous system or continue into larger lymph ducts Fluid is moved by smooth muscle contractions, endothelial contractions, skeletal muscle contractions Valves prevent backflow HSCI 211

34 Lymphatic System Returns fluid and proteins to circulatory system
Picks up fat absorbed by small intestine Filter to capture and destroy pathogens HSCI 211

35 Edema: Swelling “Accumulation of fluid in the interstitial space”
Edema varies with capillary exchange: A. Inadequate lymphatic drainage Obstruction (parasite, cancer, fibrous growth) B. Filtration is much greater than absorption Venous back-up (heart failure) Low plasma protein concentration (starvation) Increased interstitial plasma protein HSCI 211

36 Blood Pressure Systolic pressure: Ventricles contracting
Diastolic pressure: Ventricles relaxing (but there is still pressure in the arteries) HSCI 211

37 Determinants of Blood Pressure
Cardiac Output (CO) Peripheral Resistance (TPR) MAP = CO X TPR CO = Stroke Volume X Heart Rate HSCI 211

38 BP Regulation – Role of CV & Renal Systems

39 Factors influencing MAP
1/R = 1/R1 + 1/R2+… Volume CO=SVXHR HSCI 211

40 Factors Affecting Blood Pressure
Blood volume Raise intake of fluids Blood loss These are “regulated” by vasoconstriction of the vessels, sympathetic nervous system (make the blood pump faster) and the renal system Arterial-venous blood distribution Heart pump effectiveness Resistance in the blood vessels HSCI 211

41 Blood Pressure Controls
Local: Myogenic autoregulation of blood flow Meets the needs of the respective tissue/organ Paracrine concentrations stimulate smooth muscle contractions Adjusts metabolic product concentrations Central: Sympathetic nervous system (fight or flight) stimulates hormone release causing vasoconstriction and kidney excretion HSCI 211

42 Homeostatic Regulation: Baroreceptors
Carotid arteries (on the way to the brain) Aortic arch (on the way to the heart) Sensitive to distension of the vessel Send message to medulla Adjust sympathetic and parasympathetic activity HSCI 211

43 BP Regulation – Orthostatic Hypotension heart isn’t adjusting but the pressure is high so you get dizzy HSCI 211

44 Blood Pressure Regulation
Systems involved: Heart Blood vessels Kidneys Hormones (modulate the functions of the above) HSCI 211

45 Blood Pressure Measuring Devices
Sphygmomanometer Aneroid manometers Random Zero Sphygmomanometers Digital devices Ambulatory BP Monitors HSCI 211

46 Blood pressure Measurement
Use Sphygmomanometer 1. Stop the blood flow 2. Release pressure gradually The first sound we hear will be the highest pressure = systolic 3. When there is no sound the ventricles are relaxed. There is still pressure in the arteries = diastolic HSCI 211

47 Blood Pressure Cuff HSCI 211

48 Effect of Hypertension
On the heart itself: Heart attack, Myocardial infarction On the brains: Stroke On the kidneys: kidney failure/chronic kidney disease Eyes: retinopathy: retinal microvascular signs Periphery: Peripheral vascular disease

49 Errors in the Measurement of BP
Patient Errors Observer Errors Equipment Errors 1994 HSCI 211

50 Hypertension or High BP
Hypertension refers to a blood pressure measurement of greater than 140/90 mm Hg (or on medication) consistently, at rest Pre Hypertension Blood pressure is between 120/80 mmHg and 139/89 mmHg. You will see in manuals 90%: Unknown cause = Essential Hypertension. This is incorrect. Most can be attributed to some factor, usually overweight, high sodium intake, alcohol, physical inactivity, etc. Pathogenic process: Vessels: Damages endothelial wall, promoting the formation of atherosclerotic plaques Heart: Increases strain on the heart, leading to hypertrophy (pump is working harder), then back-up causing pulmonary edema, and then congestive heart failure 50 HSCI 211 HSCI 211

51 Hypertension target in terms of definition
Levels for defining hypertension have shifted down, from 165/95 mmHg to DBP >=90 mmHg to currently 140/90 mm Hg or on treatment Canadian recommendations include for diagnosis at different visits specific BP levels + presence of target organ damage or BP >=140/90 at visit 5 Epidemiologic diagnosis usually based on one or the mean of a few measures (2-6) >=140/90 Creates some difficulty for comparison of studies HSCI 211

52 Prevalence of High Blood Pressure in Canada CHHS- 1986-1992
BP > 140/90 mm Hg or treated; survey n = 23,129 4.1 million hypertensive adults Total: 22%; Women 18% Men 26% Canadian Heart Health Surveys Joffres et al. AJH, 1997 HSCI 211

53 HBP Was a Challenge In Canada
21% 13% 43% 22% Hypertensive patients who are treated but BP uncontrolled and BP controlled who are unaware Patients who are aware but remain untreated and BP uncontrolled 9% Diabetic patients who are treated and BP controlled Prevalence: 22% yrs or about 4 million Canadians Joffres et al., Am J Hypertens 2001; 14: HSCI 211

54 Percentage with hypertension† who are aware, treated by medication, controlled,‡ CHMS 2007-2009
‡ measured SBP lower than 140 mm Hg and DBP lower than 90 mm Hg E interpret with caution (coeffi cient of variation 16.6% to 33.3%) Note: Because of rounding, the sum of the estimates exceeds 100%. Source: Canadian Health Measures Survey. Conclusion: Better treatment and control now, but numbers are still high 4.6 million adults yrs and prevalence is not just slightly lower at 19% vs 22% in the 80s and 90s. Prevalence: 19% (4.6 million) of Canadian adults aged 20 to 79 years Wilkins K, Campbell NR, Joffres MR, McAlister FA, Nichol M, Quach S, HL, Tremblay MS. Blood pressure in Canadian adults. Health Rep. 2010 Mar;21(1):37-46 HSCI 211

55 Global Prevalence of HBP
Nearly 1 in 5 persons live with HBP i.e. Almost 1.5 billion people have hypertension in the world HBP = Silent killer - Symptoms are not overt & hence more people are UNAWARE In Canada about 19% of the adult population is hypertensive (approx. 4.6 million) (2009) HSCI 211

56 Attributable Mortality by Selected Factors
Ezzati et al. Lancet 2002 HSCI 211

57 % Attributable DALY by Selected Factors
DALY: Disability Adjusted Life Years Ezzati et al. Lancet 2002 HSCI 211

58 Risk Factors for High Blood Pressure
Family history Overweight Physical inactivity Alcohol Diet (high sodium and low potassium, magnesium, calcium. (smoking- lose appetite – blood pressure goes down) Age- But no or little increase with age in Brazil, Papua New Guinea, South Korea, Tokelau Islands etc. Raises question of the influence of lifestyle on age related increase in BP. HSCI 211

59 Building Awareness of HBP
National and International Hypertension Societies. See World Hypertension League World Hypertension Day 2005 – Awareness of hypertension 2006 – Treat to Goal 2007 – Healthy Diet…Healthy Blood Pressure 2008 – Measure your blood pressure … at Home 2009 – Salt and Hypertension 2010 – Healthy Weights-Healthy Blood pressure 2011 – Know Your Numbers and Target Your Blood Pressure HSCI 211

60 HSCI 211

61 Hypertension Treatment
LIFESTYLE MANAGEMENT Reduce salt intake, weight, chronic alcohol intake High fruit/vegetable diet, Stop smoking Increase exercise DRUGS: Diuretics first drug of choice Beta-blocking drugs to bind beta receptors Calcium channel blockers – helps smooth muscle not to constrict so easily ACE inhibitors and angiotensin receptor blockers (ARBs) - decrease angiotensin activity Renin-Angiotensin-Aldosterone Systems (RAAS) Combination therapy for high risk patients HSCI 211

62 Guidelines – Management of HBP
Canadian High Blood Pressure Education Program (CHEP) USA -Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC) WHO/International Society of Hypertension (WHO-ISH) European Society of Hypertension (ESH) National Societies (Culturally sensitive) HSCI 211

63 The “Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure” (JNC VII) Provides a guideline for hypertension prevention and management. The following are the report’s key messages: In persons older than 50 years, systolic blood pressure greater than 140 mmHg is a much more important cardiovascular disease (CVD) risk factor than diastolic blood pressure. The risk of CVD beginning at 115/75 mmHg doubles with each increment of 20/10 mmHg; individuals who are normotensive at age 55 have a 90 percent lifetime risk for developing hypertension. 63 HSCI 211 HSCI 211

64 JNC VII (Cont’d) Individuals with a systolic blood pressure of 120–139 mmHg or a diastolic blood pressure of 80–89 mmHg should be considered as prehypertensive and require health-promoting lifestyle modifications to prevent CVD. (High normal BP) Thiazide-type diuretics should be used in drug treatment for most patients with uncomplicated hypertension, either alone or combined with drugs from other classes. Certain high-risk conditions are compelling indications for the initial use of other antihypertensive drug classes (angiotensin converting enzyme inhibitors, angiotensin receptor blockers, beta-blockers, calcium channel blockers). 64 HSCI 211 HSCI 211

65 JNC VII (Cont’d) Most patients with hypertension will require two or more antihypertensive medications to achieve goal blood pressure (<140/90 mmHg, or <130/80 mmHg for patients with diabetes or chronic kidney disease). If blood pressure is >20/10 mmHg above goal blood pressure, consideration should be given to initiating therapy with two agents, one of which usually should be a thiazide-type diuretic. The most effective therapy prescribed by the most careful clinician will control hypertension only if patients are motivated. Motivation improves when patients have positive experiences with, and trust in, the clinician. Empathy builds trust and is a potent motivator. 65 HSCI 211 HSCI 211

66 How to measure BP at home
Do not talk Keep back supported Place cuff mid-arm at heart level Be seated Ensure arm is supported Keep legs uncrossed Keep feet flat on the floor CHEP 2008 HSCI 211

67 Leading diagnoses resulting in visits to physician offices in Canada
25 20 Routine medical exams Depression Acute respiratory tract infection 15 Diabetes Million visits/year Hypertension 10 URTI: Upper Respiratory Tract Infections. Patient visits to office-based physicians for essential hypertension numbered 18.9 million in 2002, a 10% increase from the previous year. Most visits were to GP/FMs (90%). 55% of visits were made by female patients and 45% were made by males. The age distribution was as follows: More than 81% of visits involved a drug recommendation. • Community retail pharmacies dispensed an estimated 52.7 million prescriptions for anti-hypertensive  agents in 2002, compared with 34 million in Source IMS Canada with permission. 5 Source: IMS HEALTH Canada HSCI 211

68 Benefits of Lowering Blood Pressure
In clinical trials, antihypertensive therapy has been associated with reductions in (1) stroke incidence, averaging 35–40 percent; (2) myocardial infarction (MI), averaging 20–25 percent; and (3) Heart Failure, averaging >50 percent. HSCI 211

69 It is estimated that in patients with stage 1 hypertension (SBP 140–159 mmHg and/or DBP 90–99 mmHg) and additional cardiovascular risk factors, achieving a sustained 12 mmHg reduction in SBP over 10 years will prevent 1 death for every 11 patients treated. In the added presence of CVD or target organ damage, only nine patients would require such BP reduction to prevent one death Ref: adapted from SHEP, SYST-EUR, STONE studies. HSCI 211

70 Effect of SBP and DBP on Age-Adjusted CAD Mortality: MRFIT
CAD Death Rate per 10,000 Person-years 100+ 90-99 80-89 75-79 70-74 <70 <120 160+ Diastolic BP (mmHg) Systolic BP (mmHg) 20.6 10.3 11.8 8.8 8.5 9.2 12.6 12.8 13.9 24.6 25.3 25.2 24.9 16.9 23.8 31.0 25.8 34.7 43.8 38.1 80.6 37.4 48.3 Neaton et al. Arch Intern Med 1992; 152:56-64. CAD Death rate per 10,000 person years Multiple Risk Factor Intervention Trial (MRFIT) Systolic blood pressure (SBP) and diastolic blood pressure (DBP) have been shown to be strongly associated with coronary artery disease (CAD) mortality. The combined effect of SBP and DBP on age-adjusted CAD mortality is shown on this slide. These data, from a cohort of men screened for the Multiple Risk Factor Intervention Trial (MRFIT) and followed for an average of 12 years, show that SBP is actually a stronger predictor of death from CAD than DBP. HSCI 211 Source: Neaton JD and Wentworth D for the Multiple Risk Factor Intervention Trial (MRFIT) Research Group. Serum cholesterol, blood pressure, cigarette smoking, and death from coronary heart disease. Arch Intern Med 1992; 152:56-64.

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