Pharmacological Treatment of IHD Part 1 Flashcards
Treating Imbalance in supply and demand of myocardial oxygen
Demand increases: work rate and work load
Supply decreases: thrombus, atheroma, vasoconstriction
Regulation for coronary blood flow
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
Regulation of Cardiac Workload
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)
Stable Angina
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
Reflex Tachycardia
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
Ca2+ channel antagonists
Decrease frequency and force of contraction
Leads to decreasing cardiac workload
Leads to increasing dilation of arterioles
Used when Beta blockers are contraindicated
Frequency and force of contration
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
Ivabradine
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