Cardio Flashcards
What can Atherogenesis cause?
Heart attack
Stroke
Gangrene of the extremeties
What are the risk factors for atherogenesis?
Age
Tobacco smoking
High serum cholesterol
Obesity
Diabetes
Hypertension
Family history
Where are atherosclerotic plaques commonly found?
Within peripheral and coronary arteries
What can the distribution of atherosclerotic plaques be effected by?
By haemodynamic factors -
Changes in blood flow/turbulence at bifurcations cause the artery to adjust its wall thickness ∴ develop neointima (new growth)
What can occur if an atherosclerosis plaque occludes the vessel lumen?
A restriction of blood flow (angina) OR a rupture
What are some negative outcomes of inflammation?
Artherosclerosis
Rheumatoid arthritis
Ischaemic Heart Disease
Excessive wound healing
What are some positive outcomes of inflammation?
Deals with : Pathogens, Parasites, Tumours
Wound Healing
How are leukocytes guided to the arterial wall?
Chemoattractants are released from the endothelium and send signals to leukocytes. They are released from the site of injury, and a concentration-gradient is produced -> ∴ leukocytes move toward arterial wall
How do leukocytes transmigrate into the vessel?
Selectins on the vessel wall capture the leukocyte and roll it along the vessel wall. Integrins and chemoattractants are responsible for firm adhesion of the leukocytes, and the transmigration into the vessel.
What are the 4 stages of the progression of atherosclerosis?
- Fatty streaks
- Intermediate lesions
- Fibrous plaques of advanced lesions
- Plaque rupture
Describe stage 1 of the progression of atherosclerosis
- Fatty streaks
- Appears at a v early age (<10 years)
- Consists of aggregations of lipid-laden macrophages within intimal layer of vessel wall
Describe stage 2 of the progression of atherosclerosis
- Intermediate lesions
- Composed layers of vascular smooth muscle cells, T lymphocytes, adhesion and aggregation of platelets to vessel wall, isolated pools of extracellular lipid
Describe stage 3 of the progression of atherosclerosis
- Fibrous plaques OR advanced lesions
- Impedes blood flow
- Prone to rupture
- Covered by dense fibrous cap, made by ECM proteins incl. collagen and elastin
- Laid down by SMC that overlies lipid core and necrotic debris
- May be calcified
- Contains smooth muscle cells, macrophages and foam cells and and T lymphocytes
Describe stage 4 of the progression of atherosclerosis
- Plaque rupture
- Fibrous cap has to be reabsorbed and redeposited for it to be maintained -> if balance shifts (e.g. in favour of inflammatory conditions), cap becomes weak and plaque ruptures
- Thrombus formation and vessel occlusion
What’s another cause of coronary thrombosis?
Plaque erosion
What are the differences between Plaque rupture and Plaque erosion?
Plaque erosion :
- Lesions tend to be small lesions
- Collagen triggers the thrombosis
- White thrombus
- Small lipid core
Plaque rupture :
- Big lesion (rupture)
- Tissue factor triggers the thrombosis
- Red thrombus
- Large lipid core
When there’s inflammation in the arterial wall, what occurs?
LDLs can pass in and out of the wall in XS ∴ accumulation in arterial wall and undergoes oxidation and glycation
∴ Endothelial dysfunction (response to injury hypothesis**)
What’s a method to treat coronary artery disease?
PCI - percutaneous coronary intervention
Describe PCI
Percutaneous Coronary Intervention - a family of minimally invasive procedures used to open clogged coronary arteries e.g. stent
What’s a major limitation of PCI?
Restenosis - when a previously clogged artery that was opened with a stent or angioplasty becomes narrowed again
Name some drugs used to treat coronary artery disease and describe their function
Aspirin – irreversible inhibitor of platelet cyclo-oxygenase
Clopidogrel / ticagrelor – inhibits of the P2Y12 ADP receptor on platelets
Statins – inhibit HMG CoA reductase, reducing cholesterol synthesis
PCSK9 inhibitors - monoclonal antibodies that inhibit PCSK9 protein in liver -> leads to improved clearance cholesterol from blood
What are some major cell types involved in atherogenesis?
Endothelium
Macrophages
Smooth muscle cells
Platelets
Name a method to improve the duration of stents
Drug-eluting stents - anti-proliferative and inhibits healing
What is cyclo-oxygenase required for?
The synthesis of Thromboxane A2 (TxA2)
What does TxA2 stimulate?
Platelet aggregation and vasoconstriction
What drug reduces TxA2?
Aspirin
What role does P2Y(12) ADP play?
Plays a central role in platelet activation
What can ECGs identify?
Arrhythmias
Myocardial ischaemia and infarction
Pericarditis
Chamber hypertrophy
Electrolyte disturbances (hyper/hypokalaemia)
Drug toxicity
What’s the dominant pacemaker of the body and what’s its intrinsic rate?
Sinoatrial node (60-100bpm)
What are the backup pacemakers of the body and what are their intrinsic rates?
Atrioventricular node (40 - 60bpm)
Ventricular cells (20 - 45bpm)
What is the standard calibration of an ECG machine?
25mm/s
0.1mV/mm
Describe the route of impulse conduction through the heart
SAN
AVN
Bundle of His
Bundle branches
Pukinje fibres
Describe the sections of an ECG wave
P wave – atrial depolarisation
QRS – ventricular depolarisation
T wave – ventricular repolarisation
The PR interval – atrial depolarisation and delay in AV junction (delay allows time for the atria to contract before the ventricles contract)
What are the two types of leads used in ECGs?
Bipolar leads & Unipolar leads
Describe bipolar leads
Two different points of the body (pos & neg)
Describe the Unipolar leads
One point on the body and a virtual reference point with zero electrical potential, located in the centre of the heart (only require a positive electrode for monitoring)
Name the two types of cardiac myocytes
- Atrio-ventricular conduction system (slightly faster conduction)
- General cardiac myocyte
What are some common ECG abnormalities related to the P wave?
Right atrial enlargement - talkk > 2.5mm - P pulmonale
Left atrial enlargement - notched (M-shaped) - P mitrale
Long PR interval - first degree heart block
What are some common ECG abnormalities related to the QRS complex?
Depth of the S wave should NOT exceed 30mm
Pathological Q wave
= >2mm deep and >1mm wide
= >25% amplitude of the subsequent R wave
QRS axis represents the overall direction of heart’s electrical activity ∴ abnormalities of QRS axis are likely to be ventricular enlargement OR conduction blocks
Describe a regular ST segment
ST segment usually flat (isoelectric) ∴ elevation/depression by ≥1mm can be pathological
Describe a regular T wave
Should be at least 1/8 but less than 2/3 of amplitude of R
Abnormal T waves are symmetrical, tall, peaked, biphasic or inverted
T wave amplitude RARELY exceeds 10mm
Describe a regular QT interval
Regular interval = 0.35 - 0.45s
& interval decreases when heart rate increases
Should NOT be more than half of interval between adjacent R waves
Describe a regular U wave
Small, round, symmetrical and positive in lead II w/ amplitude <2mm
U wave should be same direction as T wave
How do you determine heart rate from an ECG?
Rule of 300/1500 – regular rhythms
Count the number of big/small boxes between two QRS complexes and divide this into 300/1500 for regular rhythms.
10 second rule – irregular rhythms
Count the number of beats present on the ECG and multiply by 6.
Describe the quadrant approach for the QRS axis
The quadrant approach for the QRS axis
QRS complex in leads I and aVF
Determine if they are predominantly positive or negative
The combination should place the axis into one of the 4 quadrants below
**Lead aVF** POS | Normal axis | LAD **Lead 1**| NEG | RAD | Indeterminate Axis
LAD = left axis deviation
RAD = right axis deviation
finish
What is the normal systolic ejection fraction?
60 - 65%
Define cardiac failure
Failure to transport blood out of the heart
What is cardiogenic shock?
Severe failure to transport blood out of the heart
What is required for relaxation of the heart to occur?
Removal of calcium (energy dependent)
Myocardial hypertrophy can be ________
adaptive / physiological
e.g. athletes and pregnancy
What happens if you stretch capability of sarcomeres?
Cardiac contraction force diminishes
What triggers the hypertrophic response?
Angiotensin-2
ET-1 and insulin-like growth factor 1
TGF - beta
What does Left-sided cardiac failure cause?
Pulmonary Congestion
LV cannot pump efficiently ∴ blood backs up in veins that take blood to lungs
Pressure in these vessels ↑↑
∴ Fluid pushed into alveoli
∴ Overload of RHS of heart
What does Right Sided Cardiac Failure cause?
Venous Hypertension
High pressure in veins of legs - caused by venous insufficiency where blood leaks downwards due to effect of gravity through leaky valves
∴ Congestion
What does Diastolic Cardiac Failure cause?
Stiffer heart (LV)
This means LV cannot fill with blood fully during diastole ∴ ↓blood pumped to the body
Describe the heart structure up until the 5th week of gestation
Single chamber, divided by intra-ventricular and intra-atrial septa from endocardial cushions
How do the further chambers form in the heart after the 5th week of gestation?
Muscular intra-ventricular septum grows upwards from apex of the heart - also allows valve development to occur
Define congenital heart disease
A general term for a range of birth defects that affect the normal way the heart works
Name the 4 most common congenital heart disease and
Ventricular Septal Defect (VSD)
Name the 4 most common congenital heart disease and its % occurence
Ventricular Septal Defect (VSD) 25 - 30%
Atrial Septal Defect (ASD) 10 - 15%
Persistent/Patent Ductus Arteriosus (PDA) 10 - 20%
Fallots 4 - 10%
Define multifactorial inheritance
One child with the defect increases the probability of second child with another defect
Give some examples of single genes associated with multifactorial inheritance
Trisomy 21, Turner Syndrome (XO)
What is Turner Syndrome?
When woman only have 1 X chromosome
Results in short stature and underdeveloped ovaries
Give some examples of Homeobox genes associated with multifactorial inheritance
Infections e.g. rubella - causes congenital heart disease in baby if pregnant mother develops rubella
Define a cardiac shunt
A pattern of blood flow in the heart that deviates from the normal circuit of the circulatory system
What are some causes of a Left-Right cardiac shunt
Ventricular septal defect
Atrial septal defect
Persistent ductus arteriosus
Truncus arteriosus (a single blood vessel comes out of the right and left ventricles)
What happens during anomalous pulmonary venous drainage?
Blood flow from some pulmonary veins flows into RA instead of LA ∴ some pulmonary venous flow enters into systemic venous circulation
What happens during hypoplastic left heart syndrome?
Left side of heart is not formed correctly
∴ underdeveloped LV
What causes a Right-Left cardiac shunt?
Tetralogy of Fallot
Tricuspid atresia - absence of tricuspid valve
What are some defects that result in NO shunt. Describe them.
Complete transposition of great vessels - an abnormal spatial arrangement of any of the great vessels
Coarctation - congenital narrowing of a short section of the aorta
Pulmonary stenosis - narrowing at a point from the right ventricle to the pulmonary artery causing obstruction of blood flow
Aortic stenosis - narrowing of the aortic valve opening restricting blood flow from the left ventricle to the aorta
Coronary artery origin from pulmonary artery
Ebstein malformation/anomaly - faulty tricuspid valve
Endocardial fibroelastosis - thickening within the muscular lining of the heart chambers due to an increase in the amount of supporting connective tissue, leading to cardiac hypertrophy