Cardiac Flashcards
Physiology of Coronary artery disease
plaques form in coronary arteries due to atherosclerotic deposits
this occludes the coronary artery supplying the heart
less blood flow to heart → myocardium necrosis due to lack of oxygenation anwd blood flow → acute MI
Difference between subendocardial and transmural infarct
subendocardial: NSTEMI - plaque ruptures to cause partial occlusion to artery, infarct to subendocardial myocardium→ myocardial ischaemia + angina
transmural: STEMI - complete occlusion of artery, → myocardial necrosis + MI
What drug classes are contraindicated in HF?
NSAIDs
CCBs
Trimethoprim
Antidepressants
Drugs causing hyperkalemia
What is angina definition?
temporary loss of blood supply to heart, causing chest pain
What causes angina pectoris (stable)?
stable plaque
chest pain brought on by exertion (exercise)
What causes unstable angina?
haemodynamically unstable plaque
What are the 3 stages of atheroma formation in atherosclerosis?
3 stages of atheroma formation:
1) fatty streak formation - lipids deposited in tunica intima layer → deposits + vascular injury → inflammation, ↑ permeability and WBC recruitment to site. Macrophages phagocytose the lipid → foam cell production
2) fibrolipid plaque formation - lipid in tunica intima layer stimulated fibrocollagenous tissue formation → thinning of muscular media
3) complicated atheroma - plaque calcifies as lipid deposits acquire Ca2+ → rupture activates thrombosis (clot formation)
partial occlusion → myocardial ischaemia + angina
complete occlusion → myocardial necrosis + MI
Primary v secondary MI?
1°: primary coronary artery event due to atherosclerosis
2°: secondary due to imbalance in myocardial O2 supply and demand w/o atherothrombosis (eg severe anaemia, coronary artery spasm)
What are causes of left-sided heart failure?
CAD
HTN, aortic valve disease, mitral valve disease - ↑ workload (afterload)
MI = ↓ myocardial mass
cardiomyopathy eg amyloid, sarcoid
What are causes of right sided heart failure?
Pulmonary HTN
tricuspid valve disease
pulmonary valve disease
Conditions which increase afterload in Right sided HF:
increased afterload:
pulmonary HTN - pulmonary vessels are constricted idiopathic
PE in the pulmonary circualtion - inc pressure in pulmonary artery (similar to pulmonary HTN)
cor pulmonale 2 ° to COPD - less ventilation due to hypoxic vasoconstriction of pulmonary vessels (eg capillaries in alveoli), pulmonary artery pressure increases, therefore RV afterload increases as RV must pump more blood to overcome the pulmonary pressure, causes right-sided hyeprtrophy
What is SV?
amount of blood ejected from LV ventricle with each contraction
Pathophysiology of HF with reduced ejection fraction (HF-rEf) - SYSTOLIC
occurs in LV myocardium where blood accumulates in the LV (blood cant get pumped out of heart)
increased preload (FS LAW)
reduced contractility (due to thin, weak myocardium)
Ef less than or equal to 40% (proportion of blood being pumped out of the ventricle)
overall reduced CO
What is preload?
increase in ventricular filling = increased in myocardium stretch = increased venous return
What 3 physiological factors affect SV?
preload (∝ to SV)
contractility (∝ to SV)
afterload (NOT ∝ to SV)
What is pulse pressure?
difference between systolic and diastolic BP
What is afterload?
pressure that ventricles must overcome to push blood into aorta
CO equation
CO = HR x SV
(amount of blood pumped in 1 min) = (no of times heart beats in 1 min) x (amount of blood ejected from LV ventricle with each contraction)
afterload is same as what pressure?
diastolic BP
Equation for CO
CO = HR x SV
Physical exam signs of Right-sided HF
oedema in feet, ankles, legs (sacrum if bed bound)
ascites (fluid in abdo cavity)
hepatomegaly (enlarged, palpable, tender)
raised JVP
Exercise intolerance
Signs and symptoms of Left-sided HF
Dyspnoea
Orthopnea (dyspnoea when lying down)
PND
Bibasal creps
Cardiomegaly (displaced apex beat)
Pulmonary congestion and oedema (crackles)
Exercise intolerance
Physiology of Diastolic HF or ‘HF with Preserved Ejection Fraction (HF-PEF)’
HF when the myocardium is near-normal
Ef greater than or equal to 50%
the issue lies in filling - decreased filling activity (preload)
increased afterload
myocardium is stiff, non-compliant (doesnt want to stretch)
Conditions which cause decreased preload in diastolic HF?
can occur 2° to ischaemic Heart disease/MI
- muscle replaced with fibrous tissue in ischaemic heart disease
- this stiffens muscle
restrictive cardiomyopathy (amyloidosis)
- muscle infiltrated with light chains called amyloid deposits accumulate in the myocardium
- myocardium loses ability to stretch/contract
cardiac sarcoidosis
- rare conditions where immune cells accumulate into granulomas and deposit
- causes muscle wall to stiffen
constrictive pericarditis
- when granulation tissue forms in the pericardium
- causes loss of pericardial elasticity
- this leads to restriction in the ventricular filling
Conditions which increase afterload in diastolic HF?
HTN: high pressure in the aorta so the ventricle increases cardiomyocyte size to compensate =more sarcomere = bigger cell = more power = more blood needing to be pumped out
aortic stenosis (aortic valve disease): aortic valve stiffens, LV requires more contractile force to pump blood past it, and myocyte increases
Diastolic HF can easily progress into systolic HF
What happens if you constantly increase preload in right sided HF?
constantly increased preload
over time myocardium constantly hypertrophies
loses contractility
myocardium weakens over time → RIGHT HF
Conditions which increase preload in right sided HF:
Pulmonary valve regurgitation: if pulmonary valve damaged, instead of going to the pulmonary vasculature, will accumulate in RV, expand muscle, RV weakens over time
Tricuspid valve regurgitation: tricuspid valve damage, more blood backs into RA and leaks into RV, expands muscle, RV weakens over time