Ischemic Heart Disease Flashcards
what is ischemic heart disease?
heart problems caused by narrowed heart (coronary) arteries that supply blood to heart muscle
creates a mismatch between supply and demand
how can IHD manifest clinically
as MI and ischemic cardiomyopathy
how can death occur from IHD?
some suddenly due to acute coronary occlusion
some slowly over weeks to years due to progressive weakening of heart pumping process
what are the symptoms of IHD?
- angina
- heart rhythm problems
- Nausea, sweating, fatigue or shortness of breath, weakness or dizziness
- Reduced exertional capacity
- Leg swelling (when left ventricular dysfunction is present)
- Diaphoresis
what can angina from IHD be mistaken as?
indigestion or heart burn
what are the angina associated symptoms of IHD?
- Aching, burning, fullness, heaviness, numbness, pressure, squeezing
- Radiation in arms, back, jaw, neck, shoulder
- High or low BP
- Syncope
what heart rhythm problems may be caused by IHD?
- Palpitations (irregular heartbeats or skipped beats)
- Heart murmurs
- Tachycardia (Acute coronary syndrome ACS, Acute myocardial infarction AMI)
- Atrial fibrillation
- Ventricular tachycardia or ventricular fibrillation
- S4 gallop: A common early finding of diastolic dysfunction
- S3 gallop: An indication of reduced left ventricular function and a poor prognostic sign
what are the non-modifiable risk factors of IHD?
age
gender
family history of CVD
ethnicity
genetic evidence
previous history of CVD
what are the modifiable risk factors of IHD?
high BP
total cholesterol/ HDL cholesterol/ Lipoprotein a
smoking/ diet/ exercise/ alcohol
blood sugar/ diabetes/LVH
BMI
stress/ mental health
low socioeconomic state/ socail deprivation/ income
environment
centain medication
what are the most important risk factors to prevent over non-modifiable risk factors for IHD?
diet
who are the highest risk in high-income countries for IHD?
hypertension
cholesterol
tobacco use
what are the highest risk for IHD in low-income countries?
poor diet
low education
air pollution
low strenght
when does myocardial ischaemia occur?
imbalance between supply of oxygen (and other nutrient) and the myocardial demand
what might coronary blood flow be obstructed by?
- Atheroma
- Thrombosis
- Spasm
- Embolus
- Coronary ostial stenosis
- Coronary arteritis
what might cause a general decrease of oxygenated blood flow to myocardium?
anemia
carboxyhaemoglobulinaemia
hypotension causing decreased coronary perfusion pressure
what is atherosclerosis?
complex inflammatory process
plaques in the intima in large and medium-sized coronary arteries
also called atherogenesis
what triggers atherogenesis?
- Endothelial dysfunction
- Mechanical sheer stresses (HTN)
- Biochemical abnormalities (elevated and modified LDL, DM, elevated plasma homocysteine)
- Immunological factors (free radicals from smoking)
- Inflammation ( infection such as chlamydia, Helicobacter)
what are the features of athersclerotic plaques?
fibrous tissues
necrotic lipid rich core
foam cells
FC + infl cells
calcium
what occurs during the fatty steak phase?
dysfunctional endothelial cells + retention of lipoproteins (LDL,VLDL)
This causes:
increased expression of monocyte interaction(migration into intimal space)
Other immune cells that mediate the internalization of LDL to form foam cells
this is reversible!!
how does the plaque progress to form fibrous fatty lesions?
infiltration and proliferation of tunica media smooth muscle cells
various growth factors e.g TGF-B, FGF) create more inflammation
SMCs are recruited to luminal side of lesion to form a barrier between lesional prothrombotic factors
fibrous fatty lesions are less likely to regress than fatty streaks
what is the composition of a stable plaque?
fibrous cap composed of layers of smooth muscle cells ensconced in a substantial extracellular matrix network
it provides an effective barrier preventing plaque rupture
stable plaques have a small necrotic core
the production of TGF-B by t-reg cells and macrophages maintains fibrous cap quality by being potent stimulator of collagen production in smooth muscle cells
what makes a plaque vulnerable
unresolved inflammation causes thinning of fibrous cap
thin areas are prone to rupture exposing prothrombotic components to platelets and pro-coagulation factors
leading to thrombus formation
what happens when atherosclerotic plaque breaks through the endothelium?
what are the possible stages of presentation of coronary/ ischemic heart disease?
asymptomatic
chronic stable angina
acute coronary syndrome (unstable angina, non ST-elevation MI, ST-elevation MI)
heart failure
sudden death
what happens to the collateral vessels during acute episode hypoxia?
dilate
double by the day and reach normal coronary flow within 1 month
what happens to the collateral vessels in hypoxia for chronic atherosclerotic patients?
slow occlusion- collateral vessels can develop at same time while the atherosclerosis becomes more severe
how can an ACS occur with collaterals?
collaterals get atherosclerosis or damage is so extensive the collaterals cannot help
this can cause weaking of the heart and heart failure
what happens to the heart after an acute occlusion?
area of muscle that has either zero flow or so little that it cannot sustain cardiac muscle function= myocardial infarction
what happens do the affected areas of muscle soon after an MI with hypoxia?
small amounts of collaterals open and blood seeps into infarcted area
local blood vessels dilate and area becomes overfilled with stagnant blood
muscle fibres use all remaining oxygen
haemoglobin becomes deoxygenated giving blueish brown hue
blood vessels appear engorged despite lack blood flow
what happens to the area of affected tissue after an MI with hypoxia in the later stages?
vessel wall permeability increases, fluid leak and local tissue oedmatous
cardiac muscle cells swell and due to no blood supply die within hours
what percentage of blood supply is required to keep the muscle alive?
15-30%- muscle will not die accept in the central portion of a large infarct with no collaterals
what are the causes of death after an MI?
decreased cardiac output- systolic stretch and cardiac shock
damming of blood in venous supply
ventricle fibrillation
rupture of infarcted area
how can ventricle fibrilation occur after an MI?
can happen in first 10 mins to 1 hour
due to low cardiac flow -> low blood flow to kidneys -> fail excrete, add to blood volume -> pulmonary oedema -> die after few hours of symptoms
how does rupture of infarcted area occur?
early little danger
after few days infarcted area begin to degenerate, heart walls become very thin stretched
finally rupture
what is the recovery after an MI with a small area of ischemia?
little or no death muscle
might become non-functional temporarily due to lack of nutrients
what is the recovery after an MI with large area ischemia?
some centre die rapidly within 1-3 hours due to loss blood supply
immediately around is non-functional
area- failure of contraction and impulse conduction
surrounding non- functional still contracting but weak dye to mild ischemia
in a recovered patient from an MI when can symptoms restart?
after exercise
increases load on the heart
not enough resolve to compensate as usually does
what is the risk assessment done for IHD?
heath check program
10 year risk assessed every 5 years using QRISK- except for people with CVD or high risk or >85yrs
what biomarkers are used to predict death from IHD?
B-type natriuretic peptide
CRP
homocysteine
renin
urinary albumin to creatinine ratio
what is seen on an ECG for stable angina?
normal ECG- need an exercise stress test
during stress might see ST depressions
what is seen on an ECG for unstable angina/NSTEMI?
ST depressions and T wave inversion
what is seen on an ECG for acute MI/ STEMI
ST-segment elevation with T wave inversion
Q waves
what can transthoracic echocardiography be used to assess in IHD?
left ventricular function
mechanical complications of AMI
when are left ventricular wall motion abnormalities seen on echocardiography?
ACS or AMI
what can stress echocardiography evaluate in IHD?
haemodynamically significant stenoses in stable patients who are thought to have CAD
when is transoesophageal echocardiography used?
assessing possible aortic dissection in setting of AMI
what is the gold standard for IHD diagnosis?
coronary angiography - detect stenoses that may be revascularized through percutaneous or surgical intervention
important in detecting presence and extend CAD
independent predictors of significant coronary stenosis and other CV events
how does coronary angiography work?
iodinated contrast agent is injected through a catheter placed at the ostium of the coronaries.
The contrast agent is then visualized through radiographic fluoroscopic examination of the heart.
what does a Doppler ultrasound look at?
common and internal carotid arteries in a non-invasive m3easure of arterial wall anatomy
what are the benefits of doppler ultrasound?
non-invasive
performed repeatedly
reliable in asymptomatic individuals
what can be predicted through a doppler ultrasound?
risk of cardiovascular disease and MI/stroke
combined thickness of intima and media of carotid artery is associated with the prevalence of cardiovascular risk factors
what is the most widely applied technique for measuring coronary flow in humans?
doppler velocity probes
what does doppler velocity probe measure?
doppler guidewire measure phasic flow velocity patterns and trachs linearly with flow rates in small, straight coronary arteries
what are the indications for doppler velocity probe?
determining severity of intermediate stenosis (40-60%(
what does a doppler velocity probe help evaluate?
whether normal blood flow has been restored after percutaneous transluminal coronary angioplasty (PTCA).
what are the medicinial treatments for IHD?
HMG-CoA reductase inhibitors
Bile acid sequestrants
CCBs
ACEi
B-Blockers
antianginal agents
platelet aggregate inhibitors
nitrates
what are HMG-CoA reductase inhibitors?
These agents lower LDL-C levels. They also lower triglyceride levels and raise serum HDL levels.
Atorvastatin (Lipitor)
what are bile acid sequestrants?
- The bile acid sequestrants block enterohepatic circulation of bile acids and increase the fecal loss of cholesterol.
- Cholestyramine (Questran, LoCholest, Prevalite)
what are CCBs?
- The calcium-channel blocker amlodipine (Norvasc) relaxes coronary smooth muscle and produces coronary vasodilation, which in turn improves myocardial oxygen delivery.
- Amlodipine (Norvasc)
what do ACEi do?
- Hypertension and atherosclerosis may be intimately linked through their effects on vascular endothelial dysfunction
- Captopril (Capoten), enalapril (Vasotec), and lisinopril (Zestril)
what do beta blockers do?
- Beta-blockers inhibit sympathetic stimulation of the heart, reducing heart rate and contractility; this can decrease myocardial oxygen demand and thus prevent or relieve angina in patients with CAD.
what do antianginal agents do?
Ranolazine is a novel antianginal agent
believed to relieve ischemia by reducing myocardial cellular sodium
reduces calcium overload via inhibition of the late sodium current of the cardiac action potential.
what do platelet aggregate inhibitors do?
May exert protection against atherosclerosis through inhibition of platelet function and through changes in the hemorrhagic profile.
Clopidogrel
Aspirin
what are nitrates effective for?
- Nitrates are effective in the treatment of acute anginal symptoms.
- In this situation, they are usually given sublingually.
- The primary anti-ischemic effect of nitrates is to decrease myocardial oxygen demand by producing systemic vasodilation
what revascularisation therapies can be used to treat IHD?
percutaneous coronary intervention
coronary artery bypass grafting
what is involved with percutaneous coronary intervention?
- Involves angiography and stent placement:
- Common to treat stable CAD
- Improves blood flow by placing a stent and compressing the plaque
what is involved in CABG?
- A vessel from another part of your body to create a graft that allows blood to flow around the blocked or narrowed coronary artery.
- This type of open-heart surgery is usually used only for people who have several narrowed coronary arteries. (cant put stents in every place)
what are the prevention recommendations for IHD?
- moderate physical activity- 30 minutes/day
- Avoid tobacco use and exposure to
- diet rich in fruits, vegetables and potassium, and avoid saturated fats and calorie-dense meals.
- Maintain a normal body weight; if you are overweight, lose weight
- Reduce stress
