Radiologists: Mark Wilson
Coronary Heart Disease (CHD) is the leading cause of mortality and morbidity in the UK and the single most common cause of premature death. The UK death rate is among the highest in the world at around 120,000 per year. CHD, together with cancer and stroke, accounts for 35 per cent of life years lost before the age of 75. The World Health Organization (WHO) has predicted that by 2020, CHD will be the greatest cause of death and disability throughout the world.
CHD can develop at any age. Initially, an area of plaque forms in the coronary artery. It is not until the plaque obstructs more than 50 per cent of the coronary artery that the flow of blood to the heart muscle is reduced. This usually means that when resting, or undertaking minimal activity, the blood supply to the heart is adequate. However, when the heart requires a greater supply of oxygen, as occurs during exercise or emotional episodes, the blood supply cannot increase sufficiently and the person will experience chest discomfort. This is referred to as angina pectoris. Once plaque has formed, the wall of the coronary artery is damaged and irregular in shape and platelets cluster around the obstruction. This reduces the size of the lumen still further and consequently the blood supply is also reduced. Sometimes platelet aggregation can be sudden causing an abrupt and total occlusion of the coronary artery. At this time the person will experience a myocardial infarction (MI).
A number of factors are thought to increase the likelihood of developing CHD. The three major risk factors are smoking, hypertension and abnormal cholesterol levels. However, additional risk factors include a family history of CHD, diabetes, abdominal obesity, lack of fruit and vegetables in the diet and lack of exercise. These risk factors are common, regardless of sex, ethnic group or age and are frequently not found in isolation, thereby increasing the risk. Some risk factors are modifiable, for example, cholesterol, diabetes, hypertension, obesity, physical inactivity and smoking, and efforts should be made to increase awareness of how to reduce the likelihood of developing CHD.
In Cardiac catheterisation a long, narrow tube is inserted into a blood vessel in the arm or leg and guided to the heart with the aid of X-ray monitoring. Contrast dye is injected through the catheter to produce images of the coronary arteries that supply oxygenated blood to the heart muscle. The Cardiologist uses these images to evaluate or confirm the presence of heart disease (such as coronary artery disease, heart valve disease, or disease of the aorta) and to determine the need for further treatment (such as an interventional procedure or bypass surgery or medical therapy)
A coronary angiogram is generally safe. However, as with any invasive procedure, there are risks these are rare but can include:
- Bleeding around the point of puncture
- Abnormal heart rhythms
- Blood clots
- Allergic reaction to the dye
- Heart attack
- Perforation of a blood vessel
- Air embolism (introduction of air into a blood vessel, which can be life-threatening)
Intra Vascular Ultrasound (IVUS)
Intravascular Ultrasound (or IVUS) allows us to see a coronary artery from the inside-out. This unique point-of-view picture, generated in real time, yields information that goes beyond what is possible with routine imaging methods, such as coronary angiography, performed in the cath lab.
This cross-section view can aid in stent sizing, and in confirmation that the stent has been placed optimally, is fully expanded and hugging the vessel wall.
Intracoronary Optical Coherence Tomography (OCT)
Cardiovascular optical coherence tomography (OCT) is a catheter-based invasive imaging system. Using light rather than ultrasound, OCT produces high-resolution in vivo images of coronary arteries and deployed stents. The main applications of the OCT system are:
- Atherosclerotic plaque assessment
- Stent struts coverage and apposition management, and in-stent restenosis evaluation
- PCI guide and optimisation
Pressure wire studies
Fractional Flow Reserve (FFR) measurement involves determining the ratio between the maximum achievable blood flow in the presence of stenosis compared to the theoretical maximum flow in a normal coronary artery with a hypothetical absence of the stenosis.
|Pd = Distal pressure|
|Pa = Aortic pressure|
|Pd/Pa + hyperemia = FFR|
This ratio represents the potential decrease in coronary flow distal to the coronary stenosis.
Procedures to open blocked arteries may be carried out after the diagnostic part of the coronary angiogram is complete. Interventional procedures include balloon angioplasty and stent placement. Coronary angioplasty is one of the most common heart treatment operations, with around 75,000 procedures performed in England every year.