Pharmacological Treatment of IHD Part 1

Question 1

Treating Imbalance in supply and demand of myocardial oxygen

Answer 1

Demand increases: work rate and work load

Supply decreases: thrombus, atheroma, vasoconstriction

Question 2

Regulation for coronary blood flow

Answer 2

Endothelium - derived relaxing factor - NO
Sheer stress causes influx of calcium, which turns CTP->cGMP, which causes relaxation of smooth muscle
Dephosphorylating myosin LC-PO4 also relaxes smooth muscle

Question 3

Regulation of Cardiac Workload

Answer 3

End diastolic volume (preload) regulated b sympathetic system and RAAS (contractility of venules) and just RAAS (H2O and Na+ retention)
Heart Rate (symp NS/Ca2+)
Contractility (symp NS/Ca2+)
Lateral peripheral resistance (symp NS, RAAS)

Question 4

Stable Angina

Answer 4

Predictable pattern of pain, during exercise, relieved by rest
Treatment: decrease work load and/or increase blood supply and treat risk factors
Nitrates do both e.g. GTN, but
Side effects: postural hypotension, headache, dizziness

Question 5

Reflex Tachycardia

Answer 5

Due to activation of SNS - if treatment causes it, use a beta blocker to block effects of SNS
Beta blockers decrease frequency and force of contraction, decreasing cardiac output
Also inhibit renin release from kidney, so inhibit RAAS
Side Effects: bronchoconstriction, fatigue, contraindicated in patients with peripheral vascular disease
E.g. bisoprolol

Question 6

Ca2+ channel antagonists

Answer 6

Decrease frequency and force of contraction
Leads to decreasing cardiac workload
Leads to increasing dilation of arterioles
Used when Beta blockers are contraindicated

Question 7

Frequency and force of contration

Answer 7

CCBs can reduce heart beat by blocking L type channels in SA and AV nodes
This slows rate of depolarisation and reduces rate of AP generation
Also decreases force of contraction by reducing Ca2+ entry through L type channels

Question 8

Ivabradine

Answer 8

Blocks the pacemaker current (Ih/f - funny current) in the nodal tissue of the heart
It decreases Na+ entry through If channels - slows rate of depolarisation of the SA nodal cells and reduce firing frequency and heart rate - doesn’t directly alter force of contraction
Side effects: luminous phenomena (Ih) in retina, blurred vision, dizziness
Alternatives: long-acting nitrate (isosorbide mononitrate), nicorandil, ranolazine