Pathophysiology 1: Cardiovascular

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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


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