Block 2 - Cardiovascular Flashcards
What is the Cardiac Cycle?
- Electrical activity?
- Mechanical activity?
- Pressure differences?
- Volume changes?
Cardiac Cycle: Events associated with blood flow through the heart during a single complete heartbeat
- Electrical Activity: Summed activity of many cardiac cells, depolarisation and repolarisation detected by ECG
- Mechanical Activity: Contraction (systole) and relaxation (diastole) of myocardium
- Pressure Differences: Due to contraction and/or venous return
- Volume Changes: Due to blood flow down pressure gradient and unidirectional heart valves which prevent back flow
What are the 6 Phases the Cardiac Cycle?
Phases of the Cardiac Cycle:
- Ventricular filling (late diastole)
- Atrial contraction (atrial systole)
- Isovolumetric ventricular contraction (ventricular systole)
- Ventricular ejection (ventricular systole)
- Isovolumetric ventricular relaxation (early ventricular diastole)
- Ventricular filling (late diastole)
What are the mechanics of Cardiac muscle contraction?
Mechanics of Cardiac Muscle Contraction:
- Excitation: Trigger for contraction is myocardial cell AP firing which is caused by spread of depolarisation from pacemaker cell AP firing (myogenic control)
-
Excitation-Contraction Coupling: Triggering of contraction by gap junctions, AP firing, extracellular Ca2+ entry and Ca2+ binding to troponin.
- Current spreads to myocardial cell via gap junctions → AP travels along plasma membrane and down T-tubules → Voltage-gated Ca2+ channels open → Ca2+ entry → Ca2+-induced Ca2+ release from SR via ryanodine receptors → Ca2+ binds to troponin → Exposes myosin-binding sites on actin → Crossbridge cycling (contraction)
- Contraction: Crossbridge cycling (faster than smooth but slower than skeletal muscle)
- Relaxation: Removal of Ca2+ from cytosol Ca2+ dissociates from troponin → Ca2+ pumped into SR (active transport) AND Ca2+ transported out of cell by Ca2+/Na+ exchanger (antiport) driven by Na+ concentration gradient maintained by Na+/K+ ATPase pump
Repolarisation of cardiac muscle is an active process!!
Review the mechanisms responsible for the generation and distribution of action potentials in cardiac muscle.
- 5 steps in the Generation/Distribution of APs in Cardiac Muscle?
Generation/Distribution of APs in Cardiac Muscle: Pacemaker Cells → Conduction Fibres → Myocardial Cells
- SA node (sets the rhythm) fires an AP and depolarisation spreads to adjacent cells through gap junctions
- As APs spread across the atria (atrial depolarisation), they encounter the fibrous skeleton of the heart at the AV junction. This barricade prevents the transfer of electrical signals from the atria to the ventricles. The AV node is the only pathway (internodal pathways) through which APs can reach the contractile fibers of the ventricles.
- The electrical signal passes through the AV node (holds the rhythm). The AV node delays the transmission of APs slightly by slowing conduction through the nodal cells, allowing the atria to complete their contraction before ventricular contraction begins.
- APs spread through the bundle of His (AV bundle) and bundle branches to the apex of the heart
- The Purkinje fibers transmit impulses very rapidly, so that all contractile cells in the apex contract nearly simultaneously, allowing depolarisation of the ventricles
Predict the effect of altered electrolyte or permeability changes on the cardiac muscle action potential.
- What is the distribution of sodium, calcium and potassium in the cellular spaces?
Electrolytes:
- Sodium: Predominantly extracellular (disturbances affect the QRS complex)
- Calcium: Predominantly extracellular (disturbances affect the QT interval)
- Potassium: Predominantly intracellular (disturbances affect T waves)
What is the Effect on Myocardial Cells of different electrolyte imbalances?
How does an ECG look in hypokalemia and hyperkalemia?
Review the function of the cardiac conducting system and atrioventricular ring.
- What is the Cardiac Conduction System?
- 6 steps in pathway of cardiac conduction system?
- Why are electrical signals from the atria not conducted directly into the ventricles?
Cardiac Conduction System: Specialised cardiac muscle cells that initiate and send signals to the myocardium for contraction of the atria and ventricles
- SA Node: Starts the rhythm
- Internodal Pathway: Atrial depolarisation and contraction
- AV Node: Holds the rhythm
- Bundle of His: Ventricular septum depolarisation and contraction
- Bundle Branches: Ventricular septum and apex depolarisation and contraction
- Purkinje Fibres: Ventricular depolarisation and contraction
NB: If electrical signals from the atria were conducted directly into the ventricles, the ventricles would start contracting at the top. Then blood would be squeezed downward and would become trapped in the bottom of the ventricles. The apex-to-base contraction squeezes blood toward the arterial openings at the base of the heart.
What are the 2 Functions of Atrioventricular Ring?
Function of Atrioventricular Ring:
- Allows attachment of muscular fibers of the atria and ventricles, and the attachment of the bicuspid and tricuspid valves
- Acts as insulator (dense connective tissue does not conduct electricity), forcing electrical signals from SA node to follow internodal pathway to AV node (prevents the transfer of electrical signals from the atria to the ventricles). The AV node is the only electrical conduit from the atria to the ventricles through the cardiac skeleton.
Review the electrophysiology and interpretation of the ECG.
- What do each of the waves/segments represent?
Electrophysiology of ECG:
- P Wave: Atrial depolarisation
- PR Segment: AV nodal delay
- Q Wave: Interventricular septum depolarisation
- R Wave: Bulk of ventricular depolarisation
- S Wave: Left lateral ventricular base depolarisation
- QRS Wave: Ventricular depolarisation
- ST Segment: Period of zero potential between ventricular depolarisation and repolarisation
- T Wave: Ventricular repolarisation
What are the 7 steps in ECG Interpretation?
- What are the 2 methods for determining HR?
- How do you know if they are in Sinus rhythm?
- What is the normal range for PR interval?
- What is the normal range for QRS duration?
- What is the normal range for QT interval?
- Which leads do we look at to assess axis?
- Normal range for ST segment? Where is it measured to and from?
- Normal ranges for P, Q, T Waves?
*
ECG Interpretation
- Patient Identification (Name, Date and Age)
- Calibration: 25mm/sec and 10mm/mV
-
Rate (Heart Rate):
- Method 1: Count number of R waves within a 10 second strip and multiply by 6
- Method 2: 300 divide number of large squares between 2 R waves
- Bradycardia < 60bpm & Tachycardia > 100bpm
-
Rhythm and Intervals (PR, QRS Complex and QT):
- Sinus Rhythm: P wave before every QRS complex
- Is the rhythm regular or irregular? If irregular, is it regularly or irregularly irregular?
- PR Interval: < 200ms
- QRS Duration: 80-120ms
- QT Interval: Dependent on rate
-
Axis:
- Normal: Points down and left like apex (positive deflections in leads I, II and III)
- Right: Deviation points to right hip (negative deflection in lead I, positive in II and III)
- Left: Deviation points to left arm (positive deflection in lead I and aVL, negative in II and III)
- The normal QRS axis should be between -30 and +90 degrees.
- If the QRS complex is upright (positive) in both lead I and aVF, then the axis is normal
-
Segments (ST and PR):
- ST Segment: 0.06-0.08 seconds (2 small boxes)
- Measured from J Point to start of T wave
- Normal: Isoelectric and horizontal
- Abnormal: Elevated/depressed and upsloping/ down-sloping
-
Waves (P, QRS, T, U)
- P Wave: 0.08 seconds (2 small boxes)
- Q Wave: Less than 0.04 seconds (1 small box)
- T Wave: O.16 seconds (4 small boxes)
Relate the ECG leads to the coronary arteries and areas of the heart.
- Lateral area?
- Inferior area?
- Anterior area?
- Anteroseptal area?
- Right Atrium and LV Cavity?
Relating Leads to Areas of Heart:
Lateral Area (Circumflex Artery) → I, aVL, V5 and V6
Inferior Area (RCA) → II, III and aVF
Anterior Area (LAD) → V1, V2, V3 and V4
Anteroseptal Area (LAD) → V1 and V2
Right Atrium and LV Cavity (RCA/LAD) → V1 and aVR
What are the causes of cardiac arrhythmia? (STRIDES)
Arrhythmia: Abnormality of the cardiac rhythm (non-sinus cardiac rhythm)
Causes (STRIDES):
- Structural heart change such as cardiomyopathy or congenital heart defects
- Thyroid disease, thrombus, trauma, tamponade or tension pneumothorax
- Rheumatic heart disease and other valvular diseases
- Ischaemic heart disease, inflammation of myocardium or endocardium, injury from a heart attack
- Drugs (pro-rhythmic) and diabetes
- Electrolyte disturbance
- Social drugs including nicotine, alcohol, caffeine and cocaine or SNS activity
Describe the underlying pathophysiology of cardiac arrhythmia in terms of abnormal impulse formation and a. automaticity.
- 4 factors that contribute?
- 4 examples of arrhythmias caused by abnormal impulse formation due to automaticity?
Underlying Pathophysiology of Cardiac Arrhythmias
1. Abnormal Impulse Formation - a. Automaticity:
- Accelerated generation of an AP by either normal pacemaker tissue (enhanced normal automaticity) or by abnormal tissue within the myocardium (abnormal automaticity)
- Previously suppressed pacemakers in the atrium, AV node, or ventricle can assume pacemaker control of the cardiac rhythm if the SA node pacemaker becomes slow or unable to generate an impulse or if impulses generated by the SA node are unable to activate the surrounding atrial myocardium
- Increased SNS input or withdrawal of PNS input (exercise, beta agonist medications) results in higher sinus rates whilst decreased SNS input or increased PNS input (beta blockers, digoxin) leads to lower sinus rates
-
Factors: The discharge rate of normal or abnormal pacemakers may be accelerated by:
- Drugs
- Various forms of cardiac disease
- Reduction in extracellular K+
- Alterations of ANS tone
-
Examples:
- Sinus tachycardia
- Atrial tachycardia
- Escape rhythms
- Accelerated AV nodal (junctional) rhythms
Describe the underlying pathophysiology of cardiac arrhythmia in terms of abnormal impulse formation and b. Triggered activity.
- What are EADs and DADs?
- 6 factors that contribute?
- 7 examples of arrhythmias caused by abnormal impulse formation due to triggered activity?
Underlying Pathophysiology of Cardiac Arrhythmias
1. Abnormal Impulse Formation - b. Triggered Activity:
- Heart cells contract twice, although they only have been activated once
- Myocardial damage and electrical instability in the myocardial cell membrane can result in oscillations (after-depolarisations) of the transmembrane potential at the end of the AP, which may reach threshold potential and produce an arrhythmia
- Classified as early after-depolarisations (EADs) if repolarisation during phase 2 and/or phase 3 of the cardiac AP is interrupted, or delayed afterdepolarisations (DADs) if it occurs after full repolarisation
-
Factors:
- Catecholamines
- Electrolyte disturbances
- Hypoxia
- Acidosis
- Some medications
- Digoxin toxicity
-
Examples:
- Torsade de Pointes
- Atrial tachycardia
- Digitalis toxicity-induced tachycardia
- Accelerated ventricular rhythms in the setting of AMI
- Reperfusion-induced arrhythmias
- Right ventricular outflow tract VT
- Exercise-induced VT
Describe the underlying pathophysiology of cardiac arrhythmia in terms of abnormal impulse conduction and b. Conduction delay.
- What causes it?
- 7 Factors contributing to the pathophysiology?
- 2 Examples of arrhythmias caused by this underlying pathophysiology?
Underlying Pathophysiology of Cardiac Arrhythmias
2. Abnormal Impulse Conduction - a. Conduction Delay
- Slowed or blocked conduction through the myocardium due to damage to the conduction pathway
-
Factors:
- Cardiomyopathy
- Thrombosis
- Myocarditis
- Valvulitis
- Endocarditis
- Ischemia
- Scar tissue
-
Examples:
- AV conduction blocks
- Bundle branch blocks
Describe the underlying pathophysiology of cardiac arrhythmia in terms of abnormal impulse conduction and b. Conduction delay.
- What causes it?
- Factors contributing to the pathophysiology?
- 7 Examples of arrhythmias caused by this underlying pathophysiology?
Underlying Pathophysiology of Cardiac Arrhythmias
2. Abnormal Impulse Conduction - b. Reentry (or Circuit Movements):
- The mechanism occurs when a ring of cardiac tissue surrounds an inexcitable core (scarred myocardium)
- Tachycardia is initiated if an ectopic beat finds one limb refractory resulting in unidirectional block, and the other limb excitable.
- Provided conduction through the excitable limb is slow enough, the other limb will have recovered and will allow retrograde activation to complete the re-entry loop
- If the time to conduct around the ring is longer than the recovery times (refractory periods) of the tissue within the ring, circus movement will be maintained, producing a run of tachycardia
-
Factors:
- Injury/damage to myocardium such as ischemia, scar tissue or inflammation
-
Examples:
- Regular paroxysmal tachycardias
- Atrial fibrillation
- Atrial flutter
- AV nodal reentry
- AV reentry involving a bypass tract
- Ventricular tachycardia after MI with the presence of left ventricular scar
- Ventricular fibrillation
Describe the Classification of Arrhythmias?
Classification of Arrhythmias
Supraventricular:
-
Bradycardia (HR < 60bpm)
- Sinus Bradycardia or Arrest
- AV Block 1st Degree
- AV Block 2nd Degree
- AV Block 3rd Degree
-
Tachycardia (HR > 100bpm)
- Sinus Tachycardia
- Supraventricular Tachycardia
- Atrial Fibrillation
- Atrial Flutter
- Wolff-Parkinson-White Syndrome
-
Ventricular:
- Torsades de Pointes
- Ventricular Tachycardia
- Ventricular Fibrillation
Describe the basic principles of non-pharmacological management of arrhythmias.
Basic Principles:
- Remove extrinsic/underlying cause
- Stabilise patient
- Reduce risk of side effects and consequences
- Long-term monitoring and management
NB: VF and pulseless VT are shockable rhythms!!
What is the Valsalva manoeuvre? Mechanism? Use in arrhythmias?
Describe the pharmacology of anti-arrhythmic drugs.
- Difference between Rate and Rhythm control drugs?
- Rate control drugs
- 5 Advantages & 2 Disadvantages
- Rhythm control drugs
- 4 Advantages & 2 Disadvantages
Pharmacology of anti-arrhythmic drugs
- Rate Control: AV nodal slowing agents
- Rhythm Control: Anti-arrhythmic drugs
What is the Vaughan Williams Classification of Anti-Arrhythmic Agents?
- IA - Rhythm Control → Sodium Channel Blocker
- IB - Rhythm Control → Sodium Channel Blocker
- IC - Rhythm Control → Sodium Channel Blocker
- II - Rate Control → Beta Blockers (Adrenergic)
- III - Rhythm Control → Potassium channel blocker
- IV - Rate Control → Calcium channel blocker
- Not Classified
Discuss the Basic Mechanism, Comments and Examples of each of the classes of Anti-Arrhythmic Agents (Vaughan Williams Classification).
Describe the pharmacology of anti-arrhythmic drugs.
Discuss the Basic Mechanism, Comments and Examples of each of the classes of Anti-Arrhythmic Agents (Vaughan Williams Classification).
- What do Class Ia agents do to the cardiac AP?
- What do Class Ib agents do to the cardiac AP?
- What do Class Ic agents do to the cardiac AP?
- Where do Class II predominately act?
- What do Class III agents do to the cardiac AP?
- Where do Class IV predominately act?
Which class of anti-arrhythmic drug is used for the following arrhythmias?
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
- Atrial fibrillation?
Atrial Fibrillation:
- NO discrete P WAVES!!
- Chaotic rhythm
- Irregular QRS
- Narrow QRS
- Irregularly Irregular
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
- Atrial flutter?
Atrial Flutter:
- Look in V1 for regular waves
- Regularly Irregular
- Saw-tooth “F” waves
- Narrow QRS
- Pattern can be 2:1 or 4.1
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
- Ventricular fibrillation?
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
- 1st degree AV Block?
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
- 2nd degree AV block - Mobitz type I (Wenckebach)?
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
- 2nd degree AV block - Mobitz type II?
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
- 3rd degree (complete) AV block?
What is Atrial natriuretic peptide?
What is B-type (brain) natriuretic peptide?
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
- Right Bundle Branch Block? (4 characteristics)
Right Bundle Branch Block on ECG
- QRS duration > 0.12 seconds (3 x small squares)
- RSR’(“M”) in V1 and V2 with R’ > R
- Slurred S wave in lead I, aVL, V5, and V6
- Drop of Q
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
- Left Bundle Branch Block? (3 characteristics)
Left Bundle Branch Block on ECG
- QRS duration > 0.12 seconds (3 x small squares)
- Broad RSR’(“M”) in I, aVL, V5, and V6
- Broad, dominant, monomorphic S wave in V1 and V2
Treat as MI until proven otherwise!
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
- Wolff-Parkinson White Syndrome? (4 characteristics)
Wolff-Parkinson White Syndrome on ECG
- Characterised by attacks of rapid heart rate (pre-excitation syndrome)
- ECG may not always show tachycardia
- Short PR interval
- A delta wave (slurring of the upstroke of the QRS complex)
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
- Supraventricular Tachycardia? (2 characteristics)
Supraventricular Tachycardia on ECG
- Narrow complex (regular)
- No visible P waves (buried in QRS)
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
- Ventricular Tachycardia? (3 characteristics)
Ventricular Tachycardia on ECG
- Bizarre morphology
- Regular, wide, rapid complex tachycardia = Emergency!
- Monomorphic (QRS complex symmetrical) or polymorphic (QRS complex not symmetrical such as with Torsades)
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
- Atrial Ectopic / Premature Atrial Contraction? (4 characteristics)
- What are 4 frequently seen ectopic patterns?
Atrial Ectopic / Premature Atrial Contraction on ECG
- Extra (premature) heart beat
- An abnormal (non-sinus) P wave is followed by a QRS complex
- P wave typically has a different morphology and axis to the sinus P waves
- The abnormal P wave may be hidden in the preceding T wave, producing a “peaked” or “camel hump” appearance
Frequent Ectopy Patterns:
- Bigeminy (normal, ectopic, normal, ectopic)
- Trigeminy (normal, normal, ectopic)
- Couplets (two ectopics in a row)
- Triplets (three in a row)
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
- Ventricular Ectopic? (5 characteristics)
Ventricular Ectopic beats on ECG
- Extra (premature) heart beat
- Broad QRS complex (≥ 120 ms) with abnormal morphology
- Premature beat that occurs earlier than would be expected for the next sinus impulse
- Usually followed by a full compensatory pause
- Discordant ST segment and T wave changes
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
- Torsades de Pointes? (3 characteristics)
- Which patients do we see this in?
Torsades de Pointes on ECG
- Characteristic “twisting” morphology
- Like a party streamer
- Regularly irregular
- In patients with known long QT syndrome*
- Emergency!*
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
- Left Ventricular Hypertrophy? (3 characteristics)
Left Ventricular Hypertrophy on ECG
- Larger complexes (thicker muscle) Left axis deviation
- Deep S in V2, R in V5
- ST depression laterally
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
- Myocardial Ischaemia? (2 characteristics)
Myocardial Ischaemia on ECG
- ST depression (at rest ECG normalises)
- T wave inversion
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
-
Myocardial Ischaemia?
- STEMI? (3)
- NSTEMI? (2)
- Old Infarct? (2)
Myocardial Infarction on ECG
- ST elevation (starts at J point)
- ECG can be normal at start until tissue death
-
STEMI:
- Persistent elevation >1mm in 2 limb leads
- Persistent elevation > 2mm in 2 contiguous chest leads
- New LBBB
-
NSTEMI
- ST depression > 0.5mm
- T wave inversion > 2mm
-
Old Infarct (Death of Muscle)
- Q waves where there is no contraction (persist long term)
- T wave inversion
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
- Pericarditis? (2 characteristics)
Pericarditis on ECG
- Diffuse ST elevation (diffuse pericardial inflammation)
- Will change over days not minutes (unlike STEMI)
Demonstrate skills in identifying and interpreting common abnormalities in ECG.
- Pacemakers? (1 characteristic)
Pacemakers on ECG
- Spike then LBBB pattern (RV pacing)
What are the 8 clinical features of atrial fibrillation? Explain each.
Apply clinical reasoning to determine the physical and psychological causes of palpitations.
- Differentials for palpations?
Apply clinical reasoning to determine the physical and psychological causes of palpitations.
Demonstrate skills in interpretation of cardiac symptoms and signs.
Demonstrate skills in interpretation of cardiac symptoms and signs.
Demonstrate skills in interpretation of cardiac symptoms and signs.
Demonstrate skills in interpretation of cardiac symptoms and signs.
Describe the relationships between cardiac presentations and anxiety.
-
Anxiety Presentations?
- Emotional
- Cardiac
- Respiratory
- Gastrointestinal
- Temperature
- Somatic
- General
- Relationship to Cardiac presentation?
Anxiety Presentation:
- Emotional: Excessive and persistent worry, nervousness, fatigue and restless
- Cardiac: Palpitations, increased heart rate, dizziness, chest pain or discomfort
- Respiratory: Shortness of breath, difficulty breathing, choking sensation, hyperventilation
- Gastrointestinal: Abdominal churning, nausea, diarrhoea
- Temperature: Chills, hot flushes, sweating
- Somatic: Tremor, tension, shaking, numbness & tingling
- General: Sense of impending doom, hyperarousal, ANS hyperactivity, weak, having t rouble concentrating and sleeping, and having the urge to avoid things (avoidance behaviour) that trigger anxiety
Relationship to Cardiac Presentation:
- Threat is perceived by amygdala
- Threat is processed by hypothalamus which activates SNS
- SNS is activated and releases adrenaline and noradrenaline which will have systemic effects
List the steps involved in the Development of Atherosclerosis? (12 steps)
- 3 examples of causes of endothelial injury to arteries?
- What does endothelial dysfunction cause? What binds here?
- Describe how this causes inflammation?
- What are foam cells?
- How is a fatty streak formed? What binds to it?
- What forms the fibrous cap around the fatty streak?
- Role of calcium?
Development of Atherosclerosis (RECAP): Fatty Streak → Atheroma → Fibrous Plaque → Occlusion/Rupture
- Endothelial injury due to irritants such as LDL, chemicals from smoking or hypertension.
- Endothelial dysfunction resulting in increased permeability, leukocyte adhesion, monocyte adhesion and emigration.
- LDL bind to receptor on endothelial cells surface and are internalised to under the tunica intima.
- Monocytes follow the LDL into the endothelium and break them down via oxidation (inflammation).
- If monocytes ingest too many LDL and cholesterol, they will die and become foam cells that remain deposited under the endothelium.
- Monocytes secrete pro-inflammatory cytokines for the recruitment of more monocytes, which ingest more LDL and become foam cells, forming a fatty streak.
- The fatty streak is thrombogenic, and platelets can bind to the damaged endothelium secreting platelet derived growth factor (PDGF).
- PDGF encourages recruitment, proliferation and growth of smooth muscle cells to the tunica intima.
- Smooth muscle cells secrete collagen, proteoglycans, elastin fibrous cells that form a fibrous cap around the fatty streak (fatty streak and fibrous cap are referred to as plaque).
- Calcium is also deposited in the fatty streak as the fibrous cap prevents its removal by HDL.
- Calcium crystalises and stiffens blood vessels walls.
- Consequently, the fibrous cap can rupture and expose underlying foam cells to blood giving rise to a thrombus (blood clot). Thrombosis can lead to aneurysm, occlusion, ischemia and infarction whilst progressive plaque growth can lead to stenosis.
Review the Gross Anatomy of the Coronary Arteries and which parts of the heart they supply.
- Pathway of blood flow from aorta?
- RCA?
- RPDA?
- RMA?
- LCA?
- LAD?
- Left Circumflex?
- Left Obtuse Marginal Artery?
Gross Anatomy of the Coronary Arteries: Aorta → Aortic Sinuses → Coronary Ostio (Openings in Aorta) → Left and Right Coronary Arteries
- Right Coronary Artery: Supplies SA node, right atrium and ventricle
- Right Posterior Descending Artery: Supplies AV node, interventricular septum and right and left ventricles
- Right Marginal Artery: Supplies the right ventricle and apex
- Left Coronary Artery: Branches into left circumflex artery and LAD
- Left Anterior Descending Artery: Supplies interventricular septum, left ventricle and some of right ventricle
- Left Circumflex Artery: Supplies left atrium and ventricle
- Left Obtuse Marginal Artery: Supplies left ventricle
- NB: Both the anterior and posterior descending arteries follow the anterior/posterior interventricular groove towards the apex of the heart where they generally anastomose
- NB: Right coronary artery and left circumflex artery travel along left/right atrioventricular grooves
What are Macroscopic features of Normal Coronary Arteries (5) vs. Atherosclerosis (7)?
MACROSCOPIC FEATURES
-
Normal Coronary Arteries
- Wide lumen
- No occluded blood flow
- Lumen not encroached by plaques
- Undisturbed arterial walls (no deposits, inflammation, clots or narrowing)
- Smooth endothelial surface
-
Atherosclerosis
- Reduced lumen size
- Fatty streaks (flat yellow spots to elongated streaks)
- Tunica intima thickening
- Fibrous plaques (white-yellow and encroach on the lumen) seen on intimal surface
- Calcium deposits (white granules)
- Superimposed thrombus (red-brown) over ulcerated plaques
- Patchy eccentric lesions (not circumferential)
What are Microscopic features of Normal Coronary Arteries (3) vs. Atherosclerosis (3)?
MICROSCOPIC FEATURES/HISTOLOGY
-
Normal Coronary Arteries
- Normal tunica intima (layer of flattened endothelial cells)
- Normal tunica media (bulk middle layer of smooth muscle cells and elastin)
- Normal adventitia (thin outer layer of connective tissue)
-
Atherosclerosis
- Superficial fibrous cap composed of smooth muscle cells and dense collagen and elastin
- Beneath cap is infiltration of macrophages, T cells, and smooth muscle cells
- Deep to cap is necrotic core with cholesterol, (lipid), dead cell debris, foam cells and fibrin
Describe the mechanisms responsible for the development of myocardial ischaemia and their consequences.
- Atheroma
- Thrombosis
- Embolus
- Vasospasm
- Coronary arteritis
- Anaemia
Describe the mechanisms responsible for the development of myocardial ischaemia and their consequences.
- Atheroma
- Thrombosis
- Embolus
- Vasospasm
- Coronary arteritis
- Anaemia
What are the 2 types of disease?
Types of Disease:
- Congenital Disease
- Acquired Disease (Traumatic, Inflammatory, Degenerative and Neoplastic)
- What are the 2 types of Myocardial Diseases?
- 2 Pericardial Diseases?
- 4 Neoplasms?
Myocardial Diseases:
-
Myocarditis (Inflammatory)
- Infective Myocarditis
- Immune Myocarditis
- Idiopathic Myocarditis
-
Cardiomyopathy (Degenerative)
- Dilated Cardiomyopathy
- Hypertrophic Cardiomyopathy
- Restrictive Cardiomyopathy
- Secondary Cardiomyopathy
Pericardial Diseases:
- Pericarditis
- Cardiac Tamponade
Neoplasms
- Atrial Myxoma
- Rhabdomyoma
- Angiosarcoma
- Metastases
What is Myocarditis?
- Infective Myocarditis?
- Most common causes?
- Immune Myocarditis?
- Causes?
- 2 causes of Idiopathic myocarditis?
Myocardial Diseases:
Myocarditis (Inflammatory): Primary inflammation of the myocardium, pathologically seen as myocyte necrosis and inflammatory cell infiltration.
- Infective Myocarditis: Viruses most common causes (e.g. Coxsackie A and B, ECHO, Influenza, HIV and CMV), but can be caused by bacteria (Chlamydia, Rickettsia, Meningococcus, Diphtheria and Borrelia), fungi (candida), helminths (Trichinella) or protozoa (Chaga’s disease and Toxoplasmosis).
- Immune Myocarditis: Can occur post-viral or post-bacterial infection through cross-reactivity and development of an autoimmune condition. Also due to systemic immune disease (SLE, rheumatic fever or polymyositis), drug hypersensitivity (antibiotics, diuretics, antihypertensives) and transplant rejection.
- Idiopathic Myocarditis: Due to sarcoidosis and giant cell myocarditis
What is Cardiomyopathy?
- Dilated Cardiomyopathy? Causes?
- Hypertrophic Cardiomyopathy? Causes?
- Restrictive Cardiomyopathy? Causes?
- Causes of Secondary Cardiomyopathy?
Cardiomyopathy (Degenerative): A disorder in which the heart muscle is structurally (wall thickness and chamber size) and functionally (mechanical and electrical) abnormal. Primary myopathy can be genetic, whilst secondary myopathy is due to many causes including toxins, metabolic, drugs, infiltrates, depositions, neuromuscular.
- Dilated Cardiomyopathy: Dilation and impaired contraction of one or both ventricles (dilation can result in increased mass and eccentric hypertrophy). Common causes are viral myocarditis (Coxsackie virus) and genetics, but can also occur with drugs, alcohol and pregnancy
- Hypertrophic Cardiomyopathy: Increased ventricular wall thickness or mass not caused by pathologic loading conditions. Common causes are athletics and intense endurance training and genetics (mutations in genes coding for sarcomere proteins)
- Restrictive Cardiomyopathy: Nondilated ventricles with increased ventriuclar stiffness and impaired ventricular diastolic filling. Can occur idiopathically or due to amyloid, radiation fibrosis, sarcoidosis and metastatic tumours.
- Secondary Cardiomyopathy: Caused by cardiotoxic drugs, catecholamine excess, iron overload and thyroid disease
DILATED CARDIOMYOPATHY vs. HYPERTROPHIC CARDIOMYOPATHY?
Figure 12.30 Causes and consequences of dilated and hypertrophic cardiomyopathy. Some dilated cardiomyopathies and virtually all hypertrophic cardiomyopathies are genetic in origin. The genetic causes of dilated cardiomyopathy involve mutations in any of a wide range of genes. They encode proteins predominantly of the cytoskeleton, but also the sarcomere, mitochondria, and nuclear envelope. In contrast, all of the mutated genes that cause hypertrophic cardiomyopathy encode proteins of the sarcomere. Although these two forms of cardiomyopathy differ greatly in subcellular basis and morphologic phenotypes, they share a common set of clinical complications. LV, left ventricle.
Pericardial Diseases
- What is Pericarditis? Classifications? Causes?
- What is Cardiac tamponade? Causes?
Pericardial Diseases:
Pericarditis: Inflammation of the pericardium classified according to the composition of the fluid that accumulates around the heart (serous, fibrinous, purulent or haemorrhagic). Caused commonly by viral infection, but can also be due to bacterial infection, autoimmune conditions, post-MI, chest trauma, cancer or idiopathic.
Cardiac Tamponade: Compression of the heart caused by fluid collecting in the sac surrounding the heart (pericardial cavity). Caused by pericarditis, chest trauma, complications of cardiac surgery, cancer, kidney failure, connective tissues diseases, hypothyroidism and aortic ruptures.
Neoplasms of the Heart
- What is Atrial Myxoma?
- What is Rhabdomyoma?
- What is Angiosarcoma?
- Metastases?
Neoplasms of the Heart:
Atrial Myxoma: Rare heart disorder in which a rare tumour grows in the left heart chamber
Rhabdomyoma: Benign tumour of striated muscle
Angiosarcoma: Rare type of cancer that forms in the lining of the blood vessels and lymph vessels
Metastases: More common than primary cardiac tumours. Pericardial are most common, followed by epicardial and myocardial metastases. Can manifest as a lung mass or mediastinal mass with direct invasion of the adjacent heart, as a central mass extending into the left atrium via the pulmonary veins, as pericardial effusion and nodularity, or as myocardial nodules.
Describe and classify the clinical presentations of Ischaemic Heart Disease (IHD).
- What is the definition of IHD? 2 types of causes?
Definition of IHD: Disturbance in myocardial O2 supply and demand
Decreased Supply: Due to mechanical obstruction (atheroma, thrombosis, spasm, stenosis), or decreased flow of oxygenated blood to myocardium such as with anaemia, hypoxia, hypotension, tachycardia (shortened diastole) and carboxyhaemoglobulinaemia (carbon monoxide poisoning)
Increased Demand: Due to increased cardiac output such as with hyperthyroidism or thyrotoxicosis, or myocardial hypertrophy such as from aortic stenosis or hypertension.
Classification of IHD?
Describe the progressive manifestations of ischaemic heart disease.
Compare the blood vessel lumen in:
- a. Stable angina pectoris
- b. Unstable angina pectoris
- c. STEMI
What are 6 Clinical Features of IHD? Give explanations for each of them.
Clinical Features of IHD
- Chest Pain (Central) → Pain/Tightness/Pressure/Discomfort, Radiation to Jaw/Shoulder/Neck, On exertion (SA) or at rest (USA)
- Dyspnoea/Shortness of Breath
- Reduced Exercise Tolerance
- Sense of Impending Doom
- Palpitations
- Sweating
List the fixed and potentially changeable risk factors for coronary disease?
Outline the complications of Ischaemic Heart Disease (IHD).
- Day 1-3 Post MI? (4)
- Day 3-5 Post-MI? (5)
- Day 5-10 Post-MI? (3)
- Day 10 + Post-MI? (2)
Complications of IHD:
- Stable Angina
- Unstable Angina
- Acute Myocardial Infarction (STEMI/NSTEMI)
- Mortality
-
Day 1-3 Post MI:
- Cardiac Dysrhythmia
- Pericarditis (Early) or Dressler’s Syndrome (Delayed)
- AV Block
- Cardiogenic Shock
-
Day 3-5 Post-MI:
- Ventricular Free Wall Rupture
- Ventricular Septal Rupture
- Papillary Muscle Rupture
- Acute Mitral/Tricuspid Regurgitation
- Ventricular Pseudoaneurysm
-
Day 5-10 Post-MI:
- Ventricular Mural Thrombus
- Atrial Thrombus
- DVT and Pulmonary Embolism
-
Day 10 + Post-MI:
- Congestive Heart Failure
- Ventricular Aneurysm (VF or VT)