Pathophysiology 1: Cardiovascular
What is the ratio of coronary capillaries to cardiac muscle cells?
1 : 1
Why does the renin-angiotensin-aldosterone system activate?
1) Renal arterial blood pressure decreases 2) Lower Na in renal tubules 3) SNS stimulation
Stage 1 hypertension
130-139/80-89
Stage 2 hypertension
>140/>90
Hypertensive Crisis
>180 and/or >120
Hypertensive Encephalopathy
A cerebral disorder of hypertension indicated by severe headache, nausea, vomiting, and altered mental status. Neurological symptoms may include blindness, muscle twitches, inability to speak, weakness, and paralysis.
Exercise ECG aka "Stress Test"
A non-invasive test recording the hearts electrical activity and monitors for ischemic events during levels of exercise (jog and monitor). Test concludes when either ischemic ECG changes, angina, or dyspnea occurs. Radionuclides may be added.
Left Heart Failure causes
AMI (acute Myocardial Infarction) Systemic HTN (Hypertension) Aortic stenosis or insufficiency Cardiomyopathy
Systole (Valve Events)
AV valves shut due to increased pressure in ventricles relative to the atria Semilunar Valves open due to increased pressure in the ventricles relative to the arteries
Holter Monitoring
An ECG device is worn during a 24-hour period to detect cardiac arrhythmias. Used to evaluate the effectiveness of antidysrhythmics and pacemakers.
S4
An abnormal heart sound detected during atrial contraction as resistance is met to blood entering either ventricle during atrial contraction; most often caused by hypertrophy of the ventricle
S3
An abnormal heart sound detected early in diastole as resistance is met to blood entering either ventricle; most often due to volume overload associated with heart failure
The renin-angiotensin-aldosterone system does what to the CV system?
Angiotensin II increases vasoconstriction leading to an increase in BP
What are the semilunar valves called?
Aortic and pulmonic
Physiologic Split
Aortic valve precedes pulmonic valve closure by 0.02-0.04 sec during expiration and to 0.04-0.06 sec during inspiration
Collateral Arteries
Are connections, or anastomoses, between the branches of the coronary circulation. Protects the heart from ischemia. Are formed by a nitric oxide and endothelial growth factor
Aorta
Artery carrying blood to the systemic circuit, which carries blood to the rest of the body
Pulmonary Artery
Artery carrying deoxygenated blood from the right ventricle to the lungs
When do the atrioventricular valves open?
At the beginning of diastole
When do the atrioventricular valves close?
At the beginning of systole (ventricular contraction)
Atrial Contraction
Atria fill and distend which opens the AV valves. Passively fills ventricles. Atria contract and provide "kick" to push remaining blood into the ventricles.
P wave means...
Atrial contraction (depolarization)
Which direction do arteries carry blood relative to the heart?
Away
Diagnosis of Hypertension
BP must be taken 3 times with a reading of >90 DIAS or >140 SYS No smoking or caffeine within 30 minutes Appropriate sized BP cuff
Hypertension in the Elderly
BP ≥ 130 SYS and <80 DIAS Arteries do not stretch
Systemic Circulation
Between the heart and the body; Left side of the heart
Pulmonary Circulation
Between the heart and the lungs; Right side of the heart
What are the two atrioventricular valves called?
Bicuspid (Mitral) and tricuspid
CO x TPR = ? Cardiac Output (CO) Total Peripheral Resistance (TPR)
Blood Pressure (BP)
Alpha 2 receptors
CNS Lowers SNS activity and lowers blood pressure
Cardiac Output (CO) Equation
CO = heart rate (HR) x stroke volume (SV)
Which vessel allows for closest contact & exchange between the blood and the interstitial space?
Capillaries
Right Ventricular Heart Failure
Caused by congestion pulmonic capillaries due to left ventricular failure. Other causes: COPD Pulmonary Embolus Rt. ventricular infarction (RCA) "Cor pulmonale" when d/t lung disease
Diastolic Dysfunction
Caused by left ventricular hypertrophy. EF is fine but the SV is decreased due to less space in the ventricle. Can cause congestion
What can a coronary Arteriography show?
Clot, development of a clot, left ventricular function (End diastolic pressure and volume), ejection fraction, valve function, lack thereof
Chordae Tendineae
Connective tissue that connect the valve leaflets of the atrioventricular valves to the papillary muscles
Systole
Contraction phase of the ventricles
Which arteries & veins serve the metabolic needs of heart cells?
Coronary
Right Marginal Branch
Crosses the right ventricle transversely and ends up at the apex
Malignant Hypertension
DIAS >120mmHg; Medical EMERGENCY
Phases 3 of the cardiac cycle
Decrease in ventricular pressure causes semilunar valves to close Ventricles continue to relax
Phase 4 of the cardiac cycle
Decrease in ventricular pressure opens AV valves Permits ventricular filling from the atria
Systolic Dysfunction
Decreased contractility Low ejection fraction Big heart on chest X-ray
Circulatory System Function
Deliver oxygen, nutrients, & other substances to all body cells Remove waste products of cellular metabolism
Right Heart Failure Manifestations
Dependent pitting edema noted in sacrum of person on BR, feet & legs when sitting (10 lb weight gain before seeing edema) Pleural effusions (left sided heart failure) JVD Respiratory symptoms if caused by lung disease Early satiety Hepatomegaly, ascites, ↓ drug metabolism Hypoalbuminemia d/t liver congestion & ↓ production
Other Interactions of the Circulatory System
Digestive system - supply nutrients Respiratory System - Supply oxygen and removes CO2 Renal system - removes waste, fluid and electrolyte balance
What purpose do the valves serve in the heart?
Direct blood flow and separate the atria from the ventricles and the ventricles from the major arteries
Pericardium
Double-walled membranous sac that encloses the heart
Intrinsic Regulators of the Circulatory System
Endocrine System Nervous System
Superior and Inferior Vena Cava
Enter the heart via the right atrium
True or False: Ejection on left occurs slightly earlier than right due to pressure differences
False: The ejection occurs on the right side first, then the left. There is more pressure on the left side since it has to pump to the systemic circuit
Hypertension Risk Factors
Family history, Age, Race, Obesity, Alcohol, Stress, Oral Contraceptives, and Sodium Intake
Pericardial Cavity
Fluid containing space between the parietal and visceral pericardium
Inotropic
Force of contraction
Beta 1 Receptors
Heart Increases heart rate and contractility
Circulatory System Structure
Heart (Pump); Blood vessels (tubing)
Heart Failure (HF)
Heart as pump is impaired 🡪L ventricular problems 🡪↓ contractility Unable to pump enough blood to meet metabolic demands Results in circulatory congestion & overload
Hypertension is a risk factor for...
Heart disease and stroke
Chronotropic
Heart rate
Systolic pressure
Highest pressure achieved by the left ventricle
What does an echocardiogram measure?
How well the heart is moving. How well the valves are working. The size of the heart and its chambers
Malignant Hypertension can cause...
Hypertensive Encephalopathy Cerebral Edema and optic nerve swelling Acute Myocardial Infarction' Renal Failure
Total Organ Disease: Renal
Hypertrophy & sclerosis of arterioles and glomeruli 🡪 ↓ GFR 🡪 abnormal concentrating/diluting mechanisms 🡪 nocturia, proteinuria, microscopic hematuria, CRF
Target Organ Disease: Arterioles
Hypertrophy of tunica media Decreases lumen diameter Accelerates Atherosclerosis
Common Cardiomyopathies
Idiopathic: no known origin Congestive or dilated: usually of unknown etiology but may be associated with hyperthyroidism, alcoholism, childbirth, DM, drug toxicity (Adriamycin) Restrictive: amyloidosis, hemosiderosis (excess iron) - Myocardium becomes infiltrated with abnormal substances causing extensive fibrosis Hypertrophic: also called idiopathic hypertrophic subaortic stenosis - genetic abnormality of protein synthesis 🡪 hypertrophy of septum causing obstruction of outflow of blood Myocarditis: infection from viruses, inflammation from chemo drugs
Catecholamines do what to the heart?
Increase heart rate and force of contraction
Why is atrial natriuretic peptide (ANP) released?
Increased venous return Lead to increase in HR Leads to ANP being released
What does antidiuretic hormone do to the CV system?
Increases fluid retention in plasma Increases BP Increases vasoconstriction Increases Cardiac Output
Visceral Pericardium aka Epicardium
Inner layer of the pericardium
Endocardium
Internal lining of the heart composed of connective tissue & squamous cells Continuous with the blood vessels throughout the body
Right and left ventricles
Larger, thicker walled chambers of the heart that contract to push blood through the arteries
Atrial Blood Supply (Left and Right)
Left: 4 pulmonic veins (2 right & 2 left) Right: inferior vena cava and superior vena cava
Aortic Impedence
Loss of elasticity of aortic wall ("stiffens") Increases with aging and functioning of aortic valve. Aortic narrowing caused the L ventricle to generate higher pressure to get blood through
Beta 2 receptors
Lungs Bronchodilation
Which vessels / organ system carries plasma from the interstitium to the heart?
Lymphatic
Chemoreceptors of the blood (Measures and function)
Measures O2, CO2, and H+ Regulates Respiration
Baroreceptors: Carotid Sinus
Monitors BP to the brain
Baroreceptors: Aortic Arch
Monitors BP to the heart, makes sure there is adequate blood flow to get to the brain
Coronary Arteriography (Cardiac Catheterization)
Most precise measure of coronary artery disease. Invasive procedure in which a catheter is inserted into the coronary vessels, contrast media are injected, and images are recorded.
Why is hypertrophy in the heart a bad thing?
Muscle cells expand but the number of capillaries does not. Each capillary has to perfuse to a larger area. There is a relative decrease in available oxygen and nutrients per muscle area
Myocardium
Muscular layer of the heart
Resistance Vessels (Arteries and Arterioles)
Muscular walls High capacity to change resistance No valves Holds 25% of the blood
Electrocardiogram
Noninvasive test that evaluates the heart's function by measuring the electrical impulses of the heart
Normal Heartrate, Sinus Tachycardia, Sinus Bradycardia
Normal: 60 - 100 bpm Tachycardia: >100 bpm Bradycardia: <60 bpm
Coronary Ostia
Openings in the aorta for the coronary arteries
What does Brain Natriuretic Peptide (BNP) do?
Opposes R-A-A system (inhibition of aldosterone and renin) Vasorelaxation Increases natriuresis and reduces blood volume
Parietal Paricardium
Outer layer of the pericardium
Hypertension values
Over 140/90
Target Organ Disease: Cardiac
Overworked Left ventricle Hypertrophy and O2 demand Exceeds compensation and heart failure
Why would persantine be used in a stress test instead of exercise?
Persantine is used in place of exercise for patients who are unable to exercise. It produces dilations in the coronary arteries
Diastolic pressure
Pressure maintained in the aorta to allow for continuous flow of blood throughout the body
Pericardium Functions
Prevents undesired movement when changing positions Physical barrier to prevent infections from surrounding lungs and pleural space Contains pain and mechanoreceptors to elicit reflex changes in blood pressure and heart rate
Frank-Starling Law in Heart Failure
RAA system causes an increase in blood volume that leads to stretching of the myocardium, leading to decreased contractility
What does atrial natriuretic peptide (ANP) do?
Reduces blood volume Diuretic (Increases urinary Na loss and inhibits the release of ADH) Decreases BP
Mean Arterial Blood Pressure (MABP) (Meaning and equation)
Reflects average during contraction and relaxation DBP + 1/3 (SBP - DBP)
Total Peripheral Resistance (TPR)
Reflects the degree of vasoconstriction and the viscosity of the blood
Diastole
Relaxation phase of the ventricles
Parasympathetic stimulation of the heart
Release of neurotransmitter acetylcholine 🡪 decreases heart rate & lessens atrial & ventricular contractility & conductivity
Sympathetic stimulation of the heart
Release of neurotransmitter norepinephrine 🡪 increased heart rate, increased conduction speed through AV node, increased atrial & ventricular contractility, & peripheral vasoconstriction
Why is Brain Natriuretic Peptide (BNP) released?
Released by the ventricles in response to stimulus from ventricular stretch receptors
Some causes of hypertension besides essential hypertension
Renal: Polycystic kidney disease (Enlarged cysts in kidneys block function) Pyelonephritis (inflammation of the renal pelvis) Glomerulonephritis (inflammation of the glomeruli) Vascular: Renal artery stenosis (Blockage of kidney artery) Coarctation of the aorta (Narrow aorta (congenital)) Endocrine: Hyperaldosteronism (Too much aldosterone) Hyperthyroidism (Thyroid is working too hard) Cushing's syndrome (Too much cortisol) Pheochromocytoma (Tumor on adrenal gland) Chemical: Oral contraceptives NSAIDs Decongestants Antidepressants Sympathomimetics Corticosteroids
Alpha 1 receptors
Resistance Vessels (Arteries and Arterioles) Vasoconstriction
Papillary Muscles
Responsible for pulling the atrioventricular valves closed by means of the chordae tendineae to prevent the backflow of blood
Cardiac Conduction Order
SA node -> AV node -> Bundle of HIS -> Bundle Branches -> Purkinje Fibers
Diastole (Valve Events)
Semilunar valves close due to higher pressure in the arteries than in the ventricles. AV valves open due to higher pressure in the atria than in the ventricles
Phase 2 of the cardiac cycle
Semilunar valves open due to increase in ventricular pressure Ventricular volume and pressure starts to decrease
Interventricular septum
Separates the left and right ventricles
Pacemaker Rates per Node
Sinoatrial Node: ~70 - 75 bpm Atrioventricular Node: ~50 bpm Purkinje Fibers: ~15 - 30 bpm
Right and left atria
Smaller, thinner walled chambers of the heart that collect blood to send to the ventricles
Valsalva Maneuver
Stimulating the vagus nerve to decrease heart rate
*Know the Circulatory Path through the Heart*
Superior and inferior vena cava and coronary sinus -> right atrium -> tricuspid valve -> right ventricle -> pulmonic semilunar valve -> pulmonary arteries -> lungs -> pulmonary veins -> left atrium -> bicuspid (mitral) valve -> left ventricle -> aortic semilunar valves -> aorta
Left Anterior Descending Artery
Supplies blood to portions of the left and right ventricles and much of the interventricular septum
Conus
Supplies blood to the upper right ventricle
Posterior Descending
Supplies small branches to both ventricles
Circumflex Artery
Supplies the left atrium and the lateral wall of the left ventricle
Pulse Pressure
Systolic pressure (SBP) minus diastolic pressure (DBP)
Exercise Testing
Test in which subject walks on treadmill to test activity tolerance. If the subject walks less than 1 minute, could indicate serious cardiac problem. It is used to measure coronary artery disease
Myocardial Contractility
The ability of the heart muscle to contract. Influenced by Preload, Afterload, and SNS stimulation
Afterload
The amount of resistance to left ventricular ejection Higher TPR = Higher afterload
S1
The first heart sound, heard when the atrioventricular (mitral and tricuspid) valves close. Beginning of systole
Ejection Fraction (EF)
The fraction or percentage of the volume of blood in the ventricle that is ejected during systole Normal range is 55% to 75% total ventricular volume
Tunica Intima
The innermost layer of a blood vessel, composed of a single layer of squamous epithelial cells over a sheet of connective tissue; its smooth, frictionless surface allows blood to flow smoothly through the vessel (laminar blood flow)
Tunica Media
The middle and thickest layer of tissue of a blood vessel wall, composed of elastic tissue and smooth muscle cells that allow the vessel to expand or contract in response to changes in blood pressure and tissue demand.
Starling's Law
The more the heart is filled (increasing the length of the muscle fibers) during diastole the more forcefully it contracts. If the heart is overfilled, this stretches out the cardiac muscles and they cannot contract as well. Think of an overstretched slinky
Tunica Adventitia
The outer layer of tissue of a blood vessel wall, composed of elastic and fibrous connective tissue.
Relative refractory period
The period of time following an action potential, when it is possible, but difficult, to fire a second action potential, due to being further from threshold potential (hyperpolarized)
S2
The second heart sound, heard when the semilunar (aortic and pulmonic) valves close. End of systole
Cardiomyopathy
The term used to describe all diseases of the heart muscle that impact the contractility of the heart
Stroke Volume (SV)
The volume of blood ejected from each ventricle during systole
Cardiac Output
The volume of blood ejected from the left side of the heart in one minute.
End Diastolic Volume (EDV)
The volume of blood in the left ventricle at the end of filling just prior to contraction
Absolute refractory period
Time during which another action potential is impossible; limits maximal firing rate
Why is ADH released?
To fix high osmolarity (high solute presence in blood) or to fix low blood pressure
Pericardial Fluid Function
To lubricate membranes and minimize friction as the heart beats
Which direction do veins carry blood relative to the heart?
Towards
True or False: The heart has specialized cells that enables it to generate its own action potentials WITHOUT stimulation from the nervous system
True: These specialized cells are concentrated in areas called nodes. The autonomic nervous system can affect the heart rate but the nodes generate the action potentials that lead to contraction.
Echocardiogram
Using ultrasound to record or visualize cardiac structures
Manifestations of Hypertension
Usually no symptoms other than elevated blood pressure Symptoms seen related to organ damage are seen late and are serious Headache Swelling of optic disk = emergency Nocturia = Renal damage
Capacitance Vessels (Veins and Venules)
Valves Elastic and distensible High capacity to hold blood Holds 75% of the blood
Atrioventricular Valves
Valves that separate the atria and ventricles
Semilunar Valves
Valves that separate the ventricles and the major arteries
Pulmonary Vein
Vein carrying oxygenated blood back from the lungs to the left atrium
Why is tachycardia bad?
Ventricles not able to fill completely, so cardiac output is low. Coronary arteries receive less blood, so supply to heart is decreased. Increase in heart rate leads to an increases in oxygen consumption/need.
QRS complex means...
Ventricular contraction (depolarization) and atrial relaxation (repolarization)
T wave means...
Ventricular relaxation (repolarization)
Phase 1 of the cardiac cycle
Ventricular volume is constant. Increased ventricular pressure increases causing the AV valves to close
Preload
Volume of blood in ventricles at end of diastole
Interatrial septum
Wall that separates the left and right atria
Treatment: Lifestyle Modifications
Weight reduction - ↓ workload of heart Regular physical activity - ↓ resting HR, ↓ TPR ↓ alcohol intake Smoking cessation ↓ sodium & fat intake and ↑ Ca, K, Mg in diet 4 gm Na - watch food labels esp. canned foods Relaxation techniques - ↓ resting HR, ↓ TPR
JEOPARDY!: An electrical impulse at this node causes the ventricles to contract
What are the Purkinje Fibers?
JEOPARDY!: An electrical impulse at this node causes the atria to contract
What is the AV node?
Left Heart Failure Backwards Effects
When EF ↓, blood backs up in L atrium, pulmonary veins, pulmonary capillary bed 🡪 volume of blood in lungs ↑ 🡪 fluid enters interstitial spaces & alveoli 🡪 pulmonary edema
When do the semilunar valves close?
When the pressure in the great arteries is greater than the pressure in the ventricles
When do the semilunar valves open?
When the pressure in the ventricles exceeds the pressure in the great arteries
Total Organ Disease: Other
aortic aneurysm, retinopathy, cerebrovascular disease
Right Heart Failure Effects
↑ pressure & volume transmitted to distensible liver ↑ pressure in peritoneal vessels leads to transudation into peritoneal cavity 🡪 ascites ↑ pressure in capillaries causes peripheral edema
Myocardial oxygen needs in heart failure
↑ with HTN, ↑ HR or ventricular enlargement BUT myocardium cannot ↑ consumption
Sympathetic Response to Heart Failure
↓ CO 🡪 ↓ BP 🡪 SNS 🡪 ↑ HR & force of contraction; vasoconstriction of arterioles Trying to counteract decrease in BP
Renin-angiotensin-aldosterone system response to heart failure
↓ CO 🡪 ↓ renal perfusion 🡪 RAA 🡪 ↑ blood volume & ↑ TPR (↑ preload & afterload)
Left Heart Failure Forward Effects
↓ SV to aorta 🡪 ↓ BP 🡪 ↑ RAA & SNS 🡪 ↑ HR, vasoconstriction, ↑ blood volume
