CVS Flashcards
Modifiable risk factors for atherosclerosis
Smoking, diabetes, hyperlipidaemia, hypertension.
Non-modifiable risk factors for atherosclerosis
Old age, family history, gender-male
Define atherosclerosis
Thickening and hardening of arterial walls as consequence of atheroma formation
Define atheroma
Accumulation of intracellular and extracellular lipid in intima and media of large and medium sized arteries
Define arteriosclerosis
Thickening of walls of arteries and arterioles usually as a result of hypertension or diabetes mellitus
What is the most common cause of atrial fibrillation?
Re-entry loops
Why might atrial fibrillation lead to a stroke?
Uncoorodinated contraction of atrial muscle cells, resulting in the stagnation of blood in the atrium, can result in thrombus formation. This may dislodge into the systemic circulation, blocking a cerebral artery supplying the brain, causing an ischameic stroke.
Describe Virchow’s triad for thrombus formation
3 causes of thrombus formation: changes in blood vessel wall-, changes in blood flow- turbulence e.g. valve problems or stasis and changes in blood constituents- smoking, OCP.
Inferior MI: What leads would show abnormal complexes and which CA is most often responsible?
II, III and aVF, RCA
What area of heart does RCA supply?
Posterior and inferior
What area of heart does LCA suppy?
Lateral
Anteroseptal MI:What leads would show abnormal complexes and which CA is most often responsible?
V1-V2, LAD/ Anterior interventricular
Anteroapical MI: What leads would show abnormal complexes and which CA is most often responsible?
V3-V4, LAD(distal)
Anterolateral MI:What leads would show abnormal complexes and which CA is most often responsible?
V5-V6, I, aVL, Circumflex
Extensive anterior: What leads would show abnormal complexes and which CA is most often responsible?
V1-V6, I, aVL, Proximal LCA
Posterior: What leads would show abnormal complexes and which CA is most often responsible?
V1-V2 (tall R wave, not Q), RCA
V1-V6 electrode placement
V1- 4th IC space, R sternal border, V2- 4th IC space, L sternal border, V3- halfway between V2 and V4, V4- left 5th IC space, mid-clavicular line, V5- halfway between V4 and V6, anterior axillary line, V6- mid-axillary line.
Anterior interventricular/LAD supplies which heart areas?
R and LV, anterior 2/3 of IVS
SA nodal branch
SAN and pulmonary trunk if from RCA(60% of people), LA and SAN if from LCA
Circumflex
LA and LV
Left marginal
LV
Posterior interventricular
R and LV, posterior 1/3 of IVS
Right marginal
RV and apex
Formula for arterial blood pressure
CO x TPR
Pressure in RA
0-8mmHg
Pressures in RV
15-30mmHg/0-8mmHg
Pressures in pulmonary artery
15-30mmHg/4-12mmHg
Pressure in LA
1-10mmHg
Pressures in LV
100-140mmHg/1-10mmHg
Pressures in aorta
100-140mmHg/60-90mmHg
At what membrane potential does a ventricular myocyte AP begin and why?
-85mV as in diastole, membrane potential close to Ek as K+-selective channels open so membrane mostly permeable to K+ ions.
What is responsible for the long plateau phase in a ventricular myocyte AP?
The opening of L-type Ca2+ channels which have a slower activation and remain open for much longer compared to Na+ channels.
What does a long plateau phase in cardiac AP allow ventricular myocytes to do?
They have adequate time for contraction before onset of next AP and so can all contract simultaneously as cells still contracting when AP received in last cell.
Descrive calcium-induced-calcium-release during AP in a ventricular myocyte
Ca2+ influx from calcium voltage-gated channels activates release of calcium form intracellular stores e.g. SR, via ryanodine receptor- a non-classical ligand-gated ion channel, and this calcium is then responsible for cell contraction.
What would an ECG trace show within mins-hrs after a STEMI?
ST elevation, T wave upright
What would an ECG trace show within hrs-days 1/2 after a STEMI?
ST elevation, Twave decreases in height, R wave decreases in height, Q wave begins.
What would an ECG trace show within days 1/2 after a STEMI?
Q wave becomes deeper
What would an ECG trace show within days later after a STEMI?
ST normalises, T wave inverted, Q wave persists
What would an ECG trace show weeks after a STEMI?
ST and T normal, Q wave persists
Name 2 promoters of vasoconstriction
5-hydroxytryptamine and thromboxane A2
What do the letters MONA stand for in MI treatment?
Morphine, oxygen, nitrates and aspirin.
Describe the process of vascular smooth muscle cell contraction via alpha 1 adrenoceptors.
NA/adrenaline activate Gq, which is responsible for phospholipase C activation- cleaves PIP2 to IP3 and DAG. IP3 binds to ligand-gated ion channel on SR, causing Ca2+ efflux into cytoplasm, and this Ca2+ binds to calmodulin, activation MLCK. DAG activates protein kinase C which activates a protein which inhibits myosin phosphatase and so contraction promoted, causing vasoconstriction.
Describe how beta 2 adrenoceptors are responsible for vascular smooth muscle relaxation.
Gs- activate adenylyl cyclase- ATP converted to cAMP- inhibits MLCK so no phosphorylation of light chains in myosin so can’t form crossbridges with actin, so smooth muscle cell relaxation.