Diagnosing and Treating Heart Disease

Contents

• Introduction
• Diagnosing the type of pain & usual symptoms
• Diagnosing coronary heart disease with the latest technology
  • Non-invasive coronary angiography by computed tomography
  • Trialling the technology

Introduction

Coronary heart disease (CHD) remains the leading cause of death in the United Kingdom, killing more than 90,000 people each year. Coronary heart disease occurs when the bloodA fluid that transports oxygen and other substances through the body, made up of blood cells suspended in a liquid. supply to the heart becomes restricted or blocked due to the furring up of the coronary arteries with fatty deposits. This results in insufficient oxygen-rich blood reaching the heart so that the heart muscleTissue made up of cells that can contract to bring about movement. is unable to function properly, leading ultimately to a possible heart attackThe death of a section of heart muscle caused by an interruption in its blood supply. Also called a myocardial infarction. (myocardial infarctionDeath of an area of heart muscle due to poor blood supply. This is commonly known as a heart attack.). It also increases the risk of blood clots forming in the arteries. The most common symptom of coronary heart disease is chest pain. The lifetime risk of developing coronary heart disease in the UK by the age of 40 has been estimated at 50% in men and 33% in women and every year around 1 in 5 men and 1 in 6 women will die from it. There have been tremendous improvements in our knowledge of the underlying process of heart disease but unfortunately 30% of people who have a heart attack will not survive. This means that early detection of the condition is critically important.

Diagnosing the type of pain & usual symptoms

It is important to obtain an accurate and rapid diagnosisThe process of determining which condition a patient may have. of coronary heart disease at the outset as there may be serious consequences with a missed diagnosis, and to exclude chest pain that is not related to the heart. Also, it is vital to understand that the symptoms of heart disease are different in men and women. Women generally have heart attacks later in life (over the age of 55) and their symptoms are often masked and quite different from a typical attack in a man. Further, the traditional diagnostic method of electrocardiogramA tracing of the electrical activity of the heart. (ECGThe abbreviation for electrocardiogram, a tracing of the electrical activity of the heart to help in the diagnosis of heart disease.), which measures the electrical impulses made while the heart is beating, can be inconclusive in women and there is therefore a need to do more effective diagnostic tests to verify if heart disease is present. Similar problems are faced in diabetic patients, where the disease may remain “silent” for years (1).

Chest pains are often the first telltale signs of coronary heart disease; however, in many instances the exact cause of chest pain can remain elusive, leading to a large number of ‘false’ diagnoses. In the 1980’s, in response to this, ‘Rapid Access Chest Pain Clinics’(RACPCs) were developed and set up in order to systematically evaluate patients suffering from chest pains and this level of care has become standard within the NHS. The first test that is performed on patients arriving with chest pain is stressRelating to injury or concern. electrocardiographyA technique for tracing the electrical activity of the heart. Abbreviated to ECG. (ECGThe abbreviation for electrocardiogram, a method of recording the electrical activity of the heart muscle. It is useful for diagnosing heart disorders.). This entails leads being attached to the chest that measure how the heart functions whilst exercising, either on an exercise bike or treadmill, and therefore whilst under stress. The results of an ECG are important but some patients are not able to perform enough exercise to make an accurate diagnosis, whilst in other cases the test gives inaccurate results. In fact, large clinical studies that have looked at this suggest that estimated incorrect diagnoses may be as high as 25%. 

Doctors are well aware of this shortcoming and will therefore frequently request subsequent tests, such as a coronary angiography (CA), which is a specialised x-ray that can reveal detailed information about the heart, even when the results of the stress ECG are normal. This has in turn tended to lead to an increase in the number of invasive coronary angiography procedures being requested that result in a high percentage of normal tests (up to 55%). Unfortunately, coronary angiography is an invasive and expensive procedure, with a small but significant risk of major complications such as death, heart attack and strokeAny sudden neurological problem caused by a bleed or a clot in a blood vessel.. This is clearly an unsatisfactory state of affairs, from both a patient care and also cost perspective.

Alternative tests to stress ECG do exist, but they have generally not been employed as first line tests in RACPCs. Some of the larger hospitals in London have the ability to carry out special heart scans such as a scan that can check how well blood is flowing to the heart muscle (the Myocardial Perfusion Imaging test or MPI). This is an established and validated technique for the non-invasiveAny test or technique that does not involve penetration of the skin. The term 'non-invasive' may also describe tumours that do not invade surrounding tissues. diagnosis of coronary artery diseaseNarrowing of the blood vessels supplying the heart muscle, leading to symptoms such as angina and sometimes to a heart attack or myocardial infarction (2). Though the diagnostic accuracy is improved with heart scans, which involve a safe radioactive substance being injected into the body that can be viewed using special cameras, the all-important coronary artery branches themselves are not properly visible with this technique, although restricted blood flow to the heart caused by narrowed arteries can be seen. MPI is also a resource intensive test and needs considerable infrastructure and highly skilled staff and it is therefore restricted to only a few centres in the UK. Another useful test is echocardiographyThe use of ultrasound to examine the heart as it is pumping., which uses sound waves to build up a moving picture of the heart whilst both at rest and under stress when exercising. However this is also limited by the shortage of skilled personnel and there are also some technical difficulties that restrict its accuracy and usefulness.

Diagnosing coronary heart disease with the latest technology

The technology in this medical area is changing rapidly and so far The Cardiac Imaging Centre (CIRC) is only centre in London with the latest scanners that are currently acknowledged to be the state-of-the-art requirements for efficient, accurate and early diagnosis of heart disease. 

For those people interested in the technology, the scanners used are the dual-source, ultra-fast CTThe abbreviation for computed tomography, a scan that generates a series of cross-sectional x-ray images (computerised tomography, which combines special x-ray equipment with computers in order to produce images of the inside of the body) scanner (the Definition), combined with the hybrid CT and Gamma Camera (the SPECTAn abbreviation for single photon emission computerised tomography, an imaging technique that uses a radioactive tracer and a gamma camera.-CT) and 4D-echocardiography.

This is recognised as the latest state-of-the-art digital system for exercise testing and 24 hour ECG monitoring. 

This type of department has to be operated by interventional and clinical cardiologists, radiologists, and specialist technical and nursing staff. CIRC is unique in that it is also supported by the British Cardiac Research Trust and is acknowledged for the outstanding quality of clinical research and training that it undertakes. CIRC works closely with the NHS, and many NHS centres use the CIRC facilities for cardiac imaging. The point however is that you can only plan patient care and management accurately if you have immediate access to the most appropriate scanning procedures for the heart patient.

The scans taken by these latest pieces of equipment are completed in less than 15 seconds and their accuracy means that heart disease can be unequivocally ruled out, or where disease is present, it can be reliably diagnosed with information on the extent and severity of the disease. This provides a more accurate prognosisAn assessment of the likely progress of a condition. and treatment plan for the patient.

Non-invasive coronary angiography by computed tomography (CTA)

Non-invasive coronary angiography by computed tomography (CTA) is a recently developed technique to detect the presence of coronary artery disease. Imaging of the heart is a technically challenging task because of its continuous motion during the cardiac cycle. Also, the ‘spatial resolution’ of traditional CT scanners is too low to allow assessment of the small and tortuous coronary arteries. However, there has been considerable improvement in this technology in recent times and this has culminated in the dual source CTA. 

The dual source CT scanners are capable of very high speed imaging that visually ‘suspends’ the heart motion and allows phenomenally clear images of the coronary arteries to be seen. The whole procedure takes around 20-35 minutes and is done on an out-patient basis. The accuracy of detecting coronary artery disease is significantly higher with the dual source scanners compared to conventional CT, and new protocols have very significantly reduced the all-important ‘radiationEnergy in the form of waves or particles, including radio waves, X-rays and gamma rays. burden’ that is associated with these procedures (3).

• Benefits of Dual Source Cardiac CT Imaging
• Imaging time is 15 seconds, total time is 35 minutes 
• Allows early detection of heart disease and improved prognosis due to earlier treatment
• Is able to pick up "silent" disease, which is especially important in diabetic patients
• Can diagnose the extent and progression of disease 
• Can conclusively rule-out cardiac disease in those cases where it is not the cause of chest pain 
• Provides a low radiation exposure, comparable to traditional CT
• Is non invasive and a low risk to patients

Trialling the technology

A unique trial is currently underway at CIRC where 1000 patients referred to 3 NHS “Chest Pain” clinics will undergo rapid assessment for heart disease by Dual Source (DS) CT coronary angiography. The CT angiogramAn X-ray image of the blood vessels following the injection of a dye to improve visibility. is compared with the “standard” NHS care to evaluate the accuracy, speed of diagnosis and economic impact of Dual Source CT angiography. So far, 190 patients have already entered the trial and the results are very encouraging.

• When asked, most patients preferred CT angiogram with the CIRC CT scanner as it was non invasive compared to cardiac angiogram
• 2/3 of patients who had a DS-CT angiogram in CIRC did not require further tests
• Initial results from CT angiogram proved useful in deciding on the method of treatment.
• The study will be completed by Dec 2010 and we are hopeful that the results will have a significant impact on the way patients will be managed when presenting with chest pain.

A further study is the ‘Whitehall’ trial, a long-term study of UK civil servants where cardiac risk has been assessed longitudinally. CIRC participated in the recent trial where Coronary Artery Calcium Imaging was used to detect coronary artery disease. Intriguing data published in November 2009 suggests that “stress” is an important factor in the development of silent heart disease (4).

In conclusion then, it is of immense importance when treating suspected heart disease to have rapid and conclusive diagnosis and we now have the technology to facilitate this.

References

1. Anand V, Lim E, Hopkins D, Corder R, Shaw L, Sharp P, Lipkin D, Lahiri A
   Risk stratification in uncomplicated type 2 diabetesA disorder caused by insufficient or absent production of the hormone insulin by the pancreas, or because the tissues are resistant to the effects.:  Prospective evaluation of the combined use of coronary artery calciumAn element that forms the structure of bones and teeth and is essential to many of the body's functions. imaging and selective myocardial perfusion scintigraphy. European Heart Journal 2006; 27, 713-721

2. Sabharwal NK and Lahiri A
   Role of myocardial perfusion imagingImaging of the heart after intravenous injection of a radioactive tracer, to assess the blood supply to the heart itself. for risk stratification in suspected or known coronary artery disease Heart, 2003; 89: 1291-1297

3. Shreenidhi Venuraju, Ajay Yerramasu, Avijit Lahiri.
   Advances in cardiac computed tomography: An update for primary physicians. 
   Prim Care Cardiovasc J 2009; 2: 131-7

4. Mark Hamer, Katie O’Donnell, Avijit Lahiri, and Andrew Steptoe.
   Salivary cortisolA steroid hormone important for helping to regulate carbohydrate metabolism and the stress response. responses to mental stress are associated with coronary artery calcificationCalcium deposited in tissues and organs. in healthy men and women. European Heart J, September 2009, e-journal (advanced access publication)