Pharmacology - CHD Flashcards
Explain Coronary Blood Flow (CBF)
Venous blood returns to the right atrium, via the coronary sinus and anterior cardiac vein
Can also return to the heart chambers directly via thebesian veins
The right coronary artery then supplies blood to the SAN/AVN and the right hand
The left coronary artery supplies the left and right heart (85% of CBF)
What is the benefit of collateral vessels?
They are like B roads, so if there is ischemic damage (blockage in the main artery) then the blood can still flow around it
How is Coronary Blood Flow (CBF) regulated in the normal heart?
Autonomic NS has very little effect!!
Done by metobolic autoregulation, using potassium, adenosine and hypoxia
How does adenosine cause an increase in coronary blood flow (CBF)?
As heart rate/cardiac workload increases, more ATP is used up
The increase in AMP (from breakdown in ATP) stimulates an increase in adenosine
This stimulates A1 receptors (which decreases HR) and A2 receptors which increases cAMP levels…which causes vasodilation….and so increases CBF
How does Hypoxia and Potassium cause an increase in coronary blood flow (CBF)?
Hypoxia –> An increased workload causes less oxygen to be avaliable, and so less ATP in the coronary smooth muscle
This opens ATP-sensitive K+ channels, causing hypolarisation in the SM –> leading to vasodilation (increasing CBF)
Potassium –> An increased workload will increase the number of action potentials, which increases extracellular K+
This activates Na+K+-ATPase in the coronary SM, causing an increase in electronegativity –> causing hyperpolarisation…..and so more vasodilation and CBF
What are the 4 different types of Angina?
Myocardial Infarction (ACS) –> At rest
Unstable Angina (ACS) –> At rest, due to plaque rupture
Stable Angina –> On excertion/stress
Variant Angina –> At rest, caused by coronary vasospasms
How do you treat Stable Angina?
Reduce oxygen demand
Increase oxygen supply
Use lipid lowering drugs to prevent the progression of the atheromatous disease
First Line = BB (B1 selective) / CCB (dihydropyridines)
Second line = Organic nitrates/Ivabradine/Nicorandil/Ranolazine
How do Organic Nitrates work?
They are metabolised to release NO –> increasing levels of cGMP…which causes relaxation
Cause the systemic vasodilation of veins (decreases preload) and arteries (decrease afterload), which causes a decrease in cadiac oxygen demand
Also causes an increase in the dilation of collateral vessels, which increase oxygen supply
How do Nicorandil, Ivabradine and Ranolazine work?
Nicorandil –> Activates vascular ATP-sensitive K+ channels, and is also an NO donor
Ivabradine –> Inhibits the if pacemaker current in the SAN, which decreases HR
Ranolazine –> Inhibits late Na+ channels that are activated by ischaemia in cardiac myocytes
How do you treat Variant Stable?
Nitrate Vasodilator + CCB
BB are NOT effective
As main aim is to dilate coronary arteries
What are the 2 types of Unstable Angina?
NSTEMI –> Partial artery blockage
STEMI –> Complete artery blockage
What’s the difference between Pulmonary and Peripheral Oedema?
Pulmonary –> Left ventricular hypertrophy
Peripheral –> Congestive heart faliure (CHF)
