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HSCI 2111 Cardiovascular Physiology A. HSCI 211 2 Objectives To learn the basic anatomy and physiology of the heart –Muscle/ pump To understand the mechanism.

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Presentation on theme: "HSCI 2111 Cardiovascular Physiology A. HSCI 211 2 Objectives To learn the basic anatomy and physiology of the heart –Muscle/ pump To understand the mechanism."— Presentation transcript:

1 HSCI 2111 Cardiovascular Physiology A

2 HSCI 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)

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

4 HSCI 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

5 HSCI Exchanges External: –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

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

7 HSCI Circulation Veins Heart Aorta Delivered in parallel to organs

8 HSCI 211 8

9 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

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12 HSCI 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

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16 HSCI Heart Sounds First 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

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

18 HSCI Not in exam***

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

20 HSCI 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 O 2 & 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)

21 HSCI 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

22 HSCI 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

23 HSCI Blood Pressure

24 HSCI 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

25 HSCI 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

26 Normal Arterial Wall

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

28 Blood Vessel Structure **

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)

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32 HSCI 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

33 HSCI *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

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

35 HSCI 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

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

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

38 HSCI BP Regulation – Role of CV & Renal Systems MAP = CO X TPR

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

40 HSCI 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

41 HSCI 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

42 HSCI 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

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

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

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

46 HSCI 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

47 HSCI Blood Pressure Cuff

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

50 HSCI HSCI 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

51 HSCI 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

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

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

54 Percentage with hypertension † who are aware, treated by medication, controlled, ‡ CHMS HSCI 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 Mar;21(1):37-46

55 HSCI 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)

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

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

58 HSCI 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.

59 HSCI 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

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61 HSCI 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

62 HSCI Guidelines – Management of HBP Canadian High Blood Pressure Education Program (CHEP) 11gl/FullCHEPRecommendations_EN_2011.pdf 11gl/FullCHEPRecommendations_EN_2011.pdf 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)

63 HSCI 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. HSCI

64 HSCI 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). HSCI

65 HSCI 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. HSCI

66 HSCI 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

67 HSCI Leading diagnoses resulting in visits to physician offices in Canada Million visits/year Hypertension Depression Diabetes Routine medical exams Acute respiratory tract infection tract infection Source: IMS HEALTH Canada

68 HSCI 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.

69 HSCI 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.

70 HSCI CAD Death Rate per 10,000 Person-years <70 < Diastolic BP (mmHg) Systolic BP (mmHg) Neaton et al. Arch Intern Med 1992; 152: Effect of SBP and DBP on Age-Adjusted CAD Mortality: MRFIT CAD Death rate per 10,000 person years


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