Coronary Artery Disease (CAD)
CAD, or cardiovascular disease, refers to the process of atherosclerosis developing in the arteries supplying the heart muscle.
The cardiovascular risk factors as outlined above pre-dispose patients to deposits in the lining of the arteries. The diagram below shows the progression, starting as “streaks” and potentially developing to critical narrowings, which can lead to symptoms and heart attacks.
These are termed plaques. If these are causing a significant reduction in blood flow, this can lead to symptoms – typically chest pains. Whilst these “stable” plaques may cause symptoms, they only lead to a heart attack by becoming unstable. That is, the plaque ruptures and a blood clot forms, potentially blocking the artery. This is a medical emergency and requires urgent treatment to unblock the artery. The exact cause of plaque rupture is not known.
How is CAD managed?
- Aggressive risk factor management by lifestyle +/- drugs – stopping smoking, BP & diabetic control (if relevant) with medications. Statins are invariably recommended (see below)
- Stable CAD, as defined by predictable symptoms on exertion, is managed as above, with the addition of medications called anti-anginals. There are a number of different types of these drugs which work in different ways to control symptoms
- If stable symptoms are not controlled on medications, or the coronary narrowing is thought to be placing a significant amount of heart muscle at risk, then revascularisation is offered. This can be either a PCI or Coronary Artery Bypass Graft (CABG) operation (see below)
- Unstable symptoms require urgent hospital admission & coronary angiography. The treatment is usually urgent revascularisation
Statins work in CAD in 2 different ways
- Cholesterol reduction. There is overwhelming evidence that, the lower the cholesterol, the lower the risk of having a heart attack.
- Plaque stabilisation. Statins reduce the risk of plaque rupture, and hence reduce the risk of heart attack.
There are a number of classes of anti-anginals which act on different systems:
- Drugs which reduce the workload of the heart by lowering heart rate (beta-blockers, calcium channel blockers, ivabradine)
- Drugs which open the coronary arteries (calcium channel blockers, nitrates)