18 & 19: Ischaemic Heart Disease Flashcards
1
Q
How could ACh provoke coronary vasospasm?
A
- Normally ACh binds to M3 receptors on ECs leading to NO release and SM relaxation
- With EC damage ACh binds to M3 and M2 receptors on VSM causing vasoconstriction
2
Q
What causes ST elevation during angina attacks?
A
APs in ischemic regions are abnormal so abnormal flow of current is reflected in abnormal ECG
3
Q
Re entrant tachycardia requires what four things?
A
- Trigger
- Unidirectional propagation
- Relatively short wavelength
4
Q
Explain the action of nifedipine
A
- Relaxation and prevention of coronary artery spasm
- dilation of vessels in normal and ischemic regions
- Reduction of oxygen utilisation
- reduction in arterial pressure due to reduced TPR
5
Q
What is coronary reserve?
A
The ability to increase blood flow to cope with increased demand to the heart
6
Q
What can cause chest discomfort (due to ischaemia)?
A
- Chemical and mechanical stimuli (K+, H+, adenosine)
- Sympathetic afferents/spinothalamic
- Referred pain
7
Q
If angina is triggered by exertion, why does it persist in the absence of effort?
A
- EC dysfunction can cause inappropriate vascula rresponses
- Neurohumoral inputs e.g. anxiety inc HR and vascular tone
- Incomplete relaxation (inc. intracellular Ca)
8
Q
How does metoprolol help with chest discomfort?
A
- Beta adrenergic receptor blocker
- Limits inotropic state and reduces HR
- Keeps myocardial oxygen demand within coronary reserve capacity
9
Q
How does nitrate spray relieve chest discomfort?
A
- Coronary dilatation
- Systemic vasodilatation
- Peripheral pooling decreases cardiac filling and diastolic pressure, increasing coronary reserve via decreased extravascular compression
10
Q
Why might an anaemic patient have elevated pulse pressure?
A
- Peripheral vasodilation reduces TPR
- Leads to rapid runoff and lowered diastolic pressure
