IHD Flashcards
Describe normal coronary anatomy and physiology
LCA- develops from the left aortic sinus, bifurcates into LAD and LCx
LAD-supplies anterior wall of LV, intraventricular septum and part of the RV
LCx-Supplies the lateral and posterior walls of the LV
RCA-supplies the RA,RV and some LV, develops form the right aortic sinus divides into the posterior descending artery which supplies the inferior wall and marginal artery and the intraventricular septum
Circumflex-supplies lateral and posterior parts of the LV
Coronary veins- after suppling o2 to myocardium, deoxy blood is collected by the coronary veins, great cardiac vein, middle cardiac vein and coroanary sinus emptying into the RA
What is coronary perfusion?
pressure gradient that drives blood through arteries
-difference between aortic diastolic pressure and right atrial pressure (pressure in RA)
-occurs/favoured in diastole because during systole the myocardium contracts compressing the coronary arteries, reducing blood flwo
Describe oxygen demand and consumption
Coronary arteries supply oxygen form myocardial muscle function (MVO2)
What factors influence o2 demand?
-heart rate
preload
-afterload
-contractility
-wall tension( lapace law )
-blood oxygen content
What factors influence O2 supply?
-coronary perfusion pressure
-coronary vascular resistance
-external compression
-intrinsic regulators
-local metabolites
-neural innervation
-endothelial factors
Describe the different circulatory regulators affecting the blood flow
autoregulation- Vasoconstriction/vasodilation
endothelial regulation- endothelial cells lining blood vessels release substances such as Nitric oxide which is a vasodilator
metabolic regulation-increase in metabolic demand
-neuronal regulation- NS
Describe the factors that supply o2
HR- increased HR, increases cardiac output, less time spent in diastole, less filling of the heart- o2 debt
O2 content in the blood, high or low HB levels
vascular tone and endothelial functions regulate blood vessel dilation and constriction
Describe the factors that affect o2 demand
metabolic activity- needs more oxygen to supply myocardial cells, so produces more ATP
Increased HR- needs more oxygen to beat at an increased rate
-preload and afterload-if preload increases the heart has to work harder to release blood so it increases o2 demand, increasing the afterload means the heart has to work harder to overcome the pressure to eject blood, more oxygen needed for myocardial cells to respire to produce ATP
Name some factors that lead to the pathophysiology of IHD
Atherosclerosis
endothelial dysfunction-reduced ability of blood vessels to dilate appropriately in response to increased demand,reduced nitric oxide leads to vasodilation impairment
-myocardial ischemia- impaied ATP production leads to cellular dysfunction and myocardium swelling and lactic acid build up, electrical changes lead to arrhythmias
angina-myocardial oxygen demand exceeds supply and acute coronary syndrome results in plaque rupture and thrombus formation
Name some symptoms of IHD
-Angina- stable or unstable or variant
-Dyspnea
-MI
-HF
-cardiac arrest
-arrhythmias
-radiating pain
Tests used to identify IHD
-blood tests
-ECG
-ECHO
-left heart catheritisation
What are serum markers?
substances that can be measured in the blood and are used to diagnose, monitor or assess the severity of medical conditions
markers include things such as-proteins, enzymes,antibodies,hormones, metabolites, genetic markers
Describe some cardiac serum markers
Troponin ( Tnl and TnT)- protein released when the heart muscle is damaged, elevated levels are diagnostic of acute MI and myocardial injury
Creatine kinase (CK)- CK-MB is isoezyme specific to the heart and can be elevated in an acute MI
BNP-hormone released when there is increased pressure in heart chambers used to diagnose HF
Myoglobin-protein released when muscle tissue is injured such as heart tissue, a sensitive but not specific marker for myocardial injury
What are high levels of troponin?
levels rise within 3-6hrs after myocardial injury and stay elevated for 7-10 days (highly specific for Cardiac muscle)
normal range is less than 0.01-0.1 ng/mL
severe-0.1ng/mL
Extreme severe-1.0ng/mL
What are high levels of CK-MB?
rises within 4-6 hrs of myocardial injury peaks at 12-24hrs and returns to normal within 48-72 hrs
(less specific to cardiac muscle than troponin can be caused by other muscle injury)
elevated levels more that 5ng/mL
What is a STEMI?
-ST elevation myocardical infarction
-acute MI that occurs when there is a complete blockage of a coronary artery leading to heart muscle damage
How do we identify a STEMI on an ECG?
-ST elevation is > 1mm in limb leads and >2mm in precordial leads
-Inferior wall infarction - leads II,III AVF show ST elevation ( suggest RCA obstruction)
-Anterior wall infarction- leads V1-V4 show ST elevation (suggests LAD obstruction)
-Lateral wall infarction- Leads I, aVL, V5, V6 show ST elevation (suggests LCA obstruction)
-posterior wall infarction - ST depression in anterior leads ( V1-3) and tall R waves
(inverted T waves, Pathological Q waves)
Define NSTEMI
-non ST elevation myocardial infarction
-does not cause ST segment elevation on ECG. Associated with partial blockage of coronary artery leading to myocardial ischemia and damage to heart muscle
How do we identify a NSTEMI on an ECG?
-ST depression in contiguous leads, >1mm and may be horizontal or downsloping
-T wave inversion
NSTEMI changes based on location?
-inferior wall(RCA or LCA)
-ST depression/ T wave inversions in leads II, III, aVF
-Anterior wall ( left anterior descending artery)
ST depression/T wave inversion in leads V1-4
-Lateral wall (LCA)
ST depree/ T wave inversion in leads I, aVL,V5, V6
What is a T wave inversion?
-downward deflection of T wave
-occurs in the leads that correspond to the region of the heart affected by ischemia or injury
Define pathological Q waves
-abnormal deep and wide Q waves on and ECG indicating MI or permanent heart muscle damage
-Q waves suggest the heart muscle has been necrosed due to prolonged ischemia
What is the criteria for pathological Q waves?
duration- greater than 0.04s
depth-more than 25% of the height of the following R wave in the same lead
Shape- deep negative deflection
decribe ECG changes pre and post infarction
pre-infarction
within minutes – tall / hyperacute T waves
within minutes / hours – ST elevation
within hours – loss of R wave height; appearance of Q waves; T wave inversion
within a week or more –ST returns to normal
months afterwards – T wave returns to normal
how do we diagnose an MI?
-history
-ECG
-raised cardiac enzymes
-structural wall abnormalities
name some complications of an MI
Arrhythmias
Cardiogenic shock
LVF/ RVF
Cardiac rupture (VSD, Papillary/free wall rupture)
Mitral regurgitation
Aneurysm
Pericarditis (Dressler’s syndrome)
Thromboembolism
Depression
Define LVEF
-measurement used to assess the pumping efficency of the LV - expressed as a proportion of blood pumped out of the LV with each heartbeat relative to the total amount of blood in the ventricle before contraction
-normal range 50-70%
What is left heart catheterization?
-medical procedure to assess the function of the left side of the heart particularly the LV, LA nad coronary artreies to diagnose CAD.
-procedure unvolves inserting a catheter through blood vessels and injecting contrast dye to visualise heart chambers and arteries
What treatments are used for a STEMI?
-reperfusion therapy
-percutaneous coronary intervention- angioplasty
-Fibrinolysis-thrombolytic therapy
-CABG
-medication such as antiplatelet, anticoagulants, thrombolytics, beta blockers,statins
What is an angioplasty?
catheter with a baloon is inserted in the blocked artery and the baloon is inflated to open up the blockage- a stent is placed to keep the artery open and prevent reocclusion
What is fibrinolysis/ thrombolytic therapy?
medications such as tPA, streptokinase or reteplase used to dissolve the blood clot causing the blockage
What is a CABG?
surgically rerouting blood around blocked coronary artery using a graft from another body part
What treatments are used for a NSTEMI?
-antiplatelet, anticoagulant,beta blockers,ACE inhinitors, statins
-reperfusion therapy
Name 2 different stents used in PCI
Bare metal stents
drug eluting stents
What are drug eluting stents?
coated with a polymer that slowly releases medication ( immunosuppresant or antiproliferant) this drug helps prevent overgrowth of tissue within the stent reducing the risk of restenosis
-pros-Reduced restenosis, better for patients with complex lesions
-cons-risk of late stent thrombosis, longer duration of dual antiplatelet therapy
What are bare metal stents?
-metal mesh tubes inserted into the artery to keep open after balloon angioplasty.
-Pros-lower cost, shorter duration of antiplatlet therapy
-cons-high risk of restenosis, more likely to require repeat procedures
Prognosis of MI
Timing of revascularization
Size of MI
Extent of LV dysfunction
Extent of CAD
Recurrent ischaemia
