Cardiovascular System Pathology

Cardiovascular System Overview

• The cardiovascular (CV) system consists of the heart, blood vessels, and blood
• Its primary function is to pump blood through the blood vessels throughout the body

Heart Location and Structure

• The heart is a cone-shaped organ located slightly to the left in the thoracic cavity
• More precisely it's in the mediastinum: the space between the lungs
• It rests on the diaphragm and weighs approximately 250 to 350 grams

Chambers and Features

• The heart has four chambers: the right atrium (RA), left atrium (LA), right ventricle (RV), and left ventricle (LV)
• The atrioventricular sulcus is an external indentation between the atria and ventricles
• The interventricular sulcus is an external depression between the RV and LV

Vessels

• Veins carry blood to the heart
• Arteries carry blood away from the heart
• Great vessels are the main veins and arteries connected to the heart, including the:
  • Superior Vena Cava (SVC)
  • Inferior Vena Cava (IVC)
  • Pulmonary veins (V.) and arteries (A.)
  • Aorta

Pulmonary Circuit

• The pulmonary circuit involves the right side of the heart pumping blood to the lungs
• The pulmonary arteries deliver deoxygenated blood to the lungs
• Gas exchange occurs in the lungs between the alveoli and pulmonary capillaries
• Pulmonary veins deliver oxygenated blood from the lungs to the left side of the heart

Systemic Circuit

• The systemic circuit involves the left side of the heart receiving oxygenated blood from the pulmonary veins and pumping it to the rest of the body
• Systemic arteries pump oxygen-rich blood to all systems (except the lungs)
• Gas exchange happens at the systemic capillaries
• Systemic veins return oxygen-poor blood to the right atrium (RA)

Pressure

• The pulmonary circuit is considered a low-pressure circuit; pumps blood only to lungs
• The systemic circuit is a high-pressure circuit; pumps blood to rest of body

Heart Function

• Helps maintain blood pressure
• Rate and force of contraction influence blood pressure and blood flow to organs
• Atria produce atrial natriuretic peptide (ANP)
• ANP lowers blood pressure by decreasing sodium retention in the kidneys

Pericardium

• The pericardium is the membrane surrounding the heart
• Fibrous pericardium forms the outermost layer
• Serous pericardium produces serous fluid
  • Parietal pericardium and visceral pericardium (aka epicardium)

Pericardial Cavity

• The pericardial cavity and pericardial fluid reduces friction

Heart Wall

• The heart wall has three layers:
  • Epicardium (outermost)
  • Myocardium (middle muscle layer, made of cardiac muscle)
  • Endocardium (innermost endothelial layer)
• Fibrous skeleton: provides structure composed of dense irregular collagenous connective tissue

Cardiac Tamponade

• Cardiac tamponade occurs when the pericardial cavity fill with excess fluid placing
• The causes include: trauma, certain cancers, kidney failure, thoracic surgery, and HIV
• Excess fluid in pericardial squeezes the heart, reducing filling of ventricles
• Treatment involves removing excess fluid

Coronary Circulation

• Coronary vessels supply the heart wall
• They branch off the ascending aorta beginning with the :
  • The right coronary artery ☐
  • The left coronary artery ☐
    • It branches off the: circumflex branch and ant. interventricular a. (LAD)

Coronary Veins

• Coronary veins include:
  • Great cardiac vein
  • Small cardiac vein
  • Middle cardiac vein
  • Draining into the coronary sinus ☐ RA

Coronary Artery Disease

• Coronary artery disease (CAD) is caused by the buildup of plaques (fatty material) in the coronary arteries
• Which in turn decreases blood flow to the myocardium
• This leads to myocardial ischemia in the heart
• Symptoms include angina pectoris
• It is the leading cause of death worldwide

Myocardial Infarction

• Myocardial infarction or heart attack is the most dangerous potential consequence of CAD
• Occurs when plaques rupture in coronary arteries
• Clot forms myocardial tissue infarct
• Symptoms also may present with back, jaw, or arm pain instead in some women
• Survival depends on extent and location of damage
• Dead cells are replaced with scar tissue
• Risk factors include: smoking, increased blood pressure, poorly controlled diabetes, high levels of lipids, obesity

Angiography and Treatments

• Cardiac Angiography is the diagnostic test for CAD
• Treatments include:
  • Lifestyle modifications
  • Medications
  • Invasive treatments
    • Coronary angioplasty uses a balloon that is inflated in blocked artery to place a stent

Coronary Artery Bypass Grafting

• Coronary artery bypass grafting (CABG) uses other vessels that are grafted onto diseased coronary artery to bypass blockage

Blood Path

• The heart consists of atria and ventricles
• Atria receive blood from veins
• They then pumps through atrioventricular (AV) valves into ventricles
• Ventricles eject blood into arteries
• They carry blood through the systemic or pulmonary circuit

Blood

• Blood begins with the:
  • Superior vena cava (SVC)
  • Inferior vena cava (IVC)
  • Coronary sinus

1. Then enters: Right Atrium (RA)
   • Passes the: Right atrioventricular valve (tricuspid)
2. Enters the: Right Ventricle (RV) chordae tendineae and papillary muscles
   • This passes through the Pulmonary semilunar valve ☐ pulmonary trunk
   • Which enter the ☐ LUNGS☐ pulmonary veins
3. This enters the: Left Atrium (LA)
   • Having passed the: left Atrioventricular (AV) valve> (bicuspid or mitral)
4. The blood enters: Left Ventricle (LV) which has chordae tendineae and papillary muscles
   • Then passes an: aortic semilunar valve
   • Ascends to: the Aortic Arch

Aortic Arch

• Made up of the:
  • Brachiocephalic artery
  • Left Common Carotid Artery (LCC)
  • Left Subclavian Artery

Heart Anatomy

Features of the Heart

• Pectinate muscles consists muscular ridges inside RA
• Interatrial septum is a wall between RA & LA
• Fossa ovalis is indentation in an interatrial septum:
• Trabeculae carneae consisting ridged surface in Ventricles

Ventricles

• The RV controls low pressure
• And the LV controls high pressure

Heart Valves

• The are 4 valves total which include the:
  • Tricuspid (right AV)
  • Pulmonary semilunar
  • Bicuspid (mitral, left AV)
  • Aortic semilunar

Electrophysiology

• Cardiac muscle exhibits autorhythmicity
• Cardiac muscle cells contract in response to electrical excitation in form of action potentials (APs)
• Cardiac muscle cells do not require stimulation from nervous system to generate APs
• Pacemaker cells are specialized cardiac muscle cells (~1% of cardiac muscle cells)
• Pacemaker cells coordinate cardiac electrical activity
• These rhythmically and spontaneously generate APs to other type of cardiac muscle cells
• This can be other contractile cells at roughly 99% of cardiac muscle

Histology

Key Features

• Cardiac muscle cells have a number of defining features
• They are Striated, Branching, with usually one Nucleus
• They also feature Intercalated discs

Ion Channels

• Like skeletal muscle fibers, cardiac muscle cells contain selective gated ion channels
• Opening & closing action of these ion channels are both pacemaker & contractile cardiac APs

Syncytium

• Cardiac conduction system-Pacemaker cells undergo rhythmic, spontaneous depolarizations-APs
• Functional syncytium-Permits heart to contract as a unit and produce a coordinated heartbeat

Steps of Electrophysiology

1. Rapid Depolarization: Voltage-gated Na+ channels activate and Na+ rapidly enters thereby depolarizing the membrane
2. Initial Repolarization Phase: Na+ channels are inactivated; some K+ channels open, K+ leak out and the membrane undergoes small degree of initial repolarization
3. Plateau phase: Ca2+ channels open and Ca2+ enters as K+ continues to exit, prolonging the depolarization
4. Repolarization phase: Na+ and Ca2+ channels close, and K+ continues to exit, causing repolarization

Differences from Skeletal Muscle

• Sequence of contractile cell AP resembles that of skeletal muscle fiber AP, with one exception: plateau phase
  • Plateau lengthens cardiac AP slowing down the heart rate, providing time required for heart to fill
  • Also increases strength of heart's contraction ➤ Prevents tetany keeping lengthening refractory period

Refractory Period

• The refractory in cardiac muscle cells is so long that cells cannot sustain tetany - A sustained contraction
• this allows the heart to relax and the ventricles to refill with blood before cardiac cells can become stimulated to contract again

Anatomy of Cardiac Node

• Sinoatrial node (SA node): located in upper RA- 60 to 100 bpm influenced by the:
  • Sympathetic Nervous System
  • Parasympathetic Nervous System
• Atrioventricular node (AV node
  • Located near tricuspid valve at a rate of ±40 bpm
  • And a variable AV node delay
  • Connecting to the: Purkinje fiber system

System

• It follows the steps of
  • Atrioventricular bundle (AV bundle
  • The Right and left bundle branches-Purkinje fibers
  • These are typically located in the ventricular walls

AV Nodes

• It allows atria to depolarize (and contract) before ventricles, giving ventricles time to fill with blood
• Also helps prevent current from flowing backward from AV into AV node and atria

Dysrhythmia Indicators

• P wave indicates atrial depolarization
• QRS Complex: Indicates Ventricular depolarization, while masking atrial repolarization
• T wave measures Ventricular repolarization

Key Waveforms

• P-R waves determine the length of atrial depolarization with AV node delay
• Q-T waves determines the length of ventricular action potential
• S-T Segment measures Ventricular plateau phase

Dysrhythmias

• Dysrhythmias: indicate electrical impulse distributions have become erratic

The Heart Rates

• Bradycardia: HR < 60 bpm
• Tachycardia: HR > 100 bpm
• **Sinus Tachycardia:**Regular & fast rhythm

2. Disturbances in conduction pathways

Disrupted by accessory pathways between upper & lower chambers or by heart block

• Heart block at Av Node: The P-R interval is longer than normal, due to time increase. Time for impulses to travel to ventricles from AV node The SA node isn't extra P being conducted through AV nodes

Right or Left Bundle Branch Block

Generally widens QRS complex spreading taking longer though the ventricles in the heart

Atrial fibrillation

• Generally and isn't as life threatening because atrial contradiction isn't. As necessary for ventricular fluid
• That also means ECG tracings have an irregular pattern that lacks P waves

3. Fibrillation

Electrical impulses begin haywire-Depolarizing parts of the heart without contraction . The Bag O worms Withering in a circular pattern

• In the: Ventricular: This action is immediately life threatening
• Can be remedied with Defibrillation (Electrical shock). This Electrical activity can paralyze heart tissue or reset it so the Sinoatrial pacemaker node resumes.

Heart Failure

• Treat "Flatline with CPR-Heart muscle ceases altogether",
• With Asystole:
• An Absence of Electrical signals on the heart
• And to attempt to restore electrical patterns through
• Electrical Activity has been exhausted
• The Heart can Not be Electrically reset

Mechanical Physiology of the Heart

• Mechanical physiology involves actual processes by which blood fills and is pumped out chambers
• Heartbeat refers to how cardiac muscle cells contract to ensure one coordinated unit in contraction
• Cardiac cycle is a sequence of events that take place from one heartbeat to the next (systole followed diastole for each chamber)

Systemic vs Diastole

• Blood flows in response to pressure that is reliant to pressure gradients as ventricles contract-Relaxing, resulting in pressure changes within chambers
• During Ventricular systole, AV valves are forced to shut by blood that is pushing against themselves.
• Meanwhile semilunar valves/outflowing blood are forced open
• Ventricular diastole is: Pressure in ventricles that falls to those in atria and in pulmonary trunk and aorta
• Causes AV Valve to : Open, allowing blood to drain from atria into relaxed ventricles

Stethoscope

Aids in assisting what is occurring in the sound and operation of the heart. S1 “lub” sound, AV valves in a position that can then close S2 “dub” sound, Semi-Lunar valves in a position that can then close

Cardiac Cycle

• A cycle of diastole plus: One Systole per chambers of the heart
• The Four Functions consist: Cycle, Is divided in The Ventricles
• 4 phases of heart function are :

1. Filling
2. Contraction
3. Ejection
4. Relaxation

Ventricular Filling Phases

• Blood drains from atria into ventricles
• LV and RV have lower pressures within the same atrium.
• Higher pressures in pulmonary trunk and aorta cause semilunar valves : Close
• This Prevents for Blood from entering into the ventricles Is Volume
• This causes Isovolumetric as Systole

Ventricular Systole Phases

• Av and Semi Valve which are a type Aortic and Pulmonary Valves can only close
• 3. Venctricular : Injection- The Phase of Continued systole as it pushes towards pulmonary and aorta systems*
• Finally to reach a : Relaxation where
• Ventricular diastole begins with , semi valves shutting

Cardiac and the Pressure

• What does a normal heart pressure look like: Both the Comparison and pressure would show to have equal exchange

Introduction to Cardiac Output and Regulation

• Heart rate(HR) is measured in cycles/bpm
• The Stroke Volume (SV) is in blood in ML per beat
• Then Cardiac output: Is the rate in terms of the blood volume pumped into systems in and around the heart that is measured in min
• C.O. = heart rate by Volume-72 beats per min times 70 Blood Vol and liters or more a minutes*
• RV pumps a volume of 5 Liters into pulmonary circuit
• LV pumps equivalent in same terms to systemic circuit
• Totaling in blood that passes through heart to be Five liters in total volume

Regulation

• Volume and starling, Ensure equals is Vol*
• *Increased rate will: forcefully contract the same in the volume or vol to equal amounts
• Contractility:* the pumping ability within heart
• The Heart is in Preload Systemically*
• After load or output load from Left: Determines the Aorta output*

As these conditions have increased there are associations with enlargement. Especially in the area of the Heart

_Muscle Cells of Ventricles It has to equal Which creates same tension so skeletal fibres and tension equal out _

What is the result

An enlargement from the Heart in all forms of skeletal structure Right- Side increase of heart can: be found with breathing disfunction or High Blood Left can do the same: Where a higher BP can :Increase Effective certain points-And Decreases Heart Lumen

• Increase by what causes these-A high level of blood pressure or heart pressure/ rate leading to the heart eventually growing at a high fast
• Decrease by Heart failure
• Increase for many such cases: Leading to higher cardiac and increased heart failure Heart rate for Rate. The Sinoatrial sets the rate of the rate, if rate is: Factors for high blood pressure:
• Positive Chronotropic-
• Sympatic nervous system
• Hormomes And increase body Temp = increase Heart Rate

Regulation of cardiac output

the increase is measured in by how much, which includes volume 104 These conditions, in the end, can lead to heart failure.

Questions about cardiovascular diseases. These questions cover coronary artery disease, myocardial ischemia, angina pectoris, myocardial infarction and cardiac tamponade. It also addresses the fibrous skeleton of the heart, and the impact of arterial blockage.