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Latest Cardiac Diagnostics and Treatment Methods
by Professor Avijit Lahiri MB,BS,MSc,MRCP,FACC,FESC Consultant Cardiologist & Director of the
Cardiac Imaging and Research Centre at The Wellington Hospital.
Article last updated: December 9th 2009
Introduction
Coronary artery disease (CAD) remains the leading cause of death in the United Kingdom, killing approx 90,000 people every year. Every year 1 in 5 men and 1 in 6 women will die from CAD. The lifetime risk of developing coronary heart disease (CHD) in the UK by the age of 40 has been estimated at 50% in men and 33% in women. In addition to imposing a great burden, both economically and on the already stretched resources of the NHS, it is also the most important factor contributing to the number of years of life lost before the age of 65.
Why screening for cardiovascular disease (CVD)?
There have been tremendous improvements in our knowledge of the underlying process of cardiovascular disease (CVD), but unfortunately 30% of people who have a heart attack don’t survive therefore early detection is critically important. Early detection is confounded by the fact that almost 80% of the patients have had “silent” heart disease for many years.
Diagnosing the type of pain & usual symptoms
It’s important to obtain an accurate and rapid diagnosis of coronary artery disease at the outset and exclude non-cardiac chest pain, since there may serious consequences with a missed diagnosis. Also it’s vital to understand that the symptoms of heart disease are different in men than women. Women generally have heart attacks later in life (>55yrs) and their symptoms may be masked and be very different from a typical attack in a man. Further, the traditional method of ECG can be inconclusive in women, hence the 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 (Ref 1- Anand et al).
Chest pains are often the first telltale signs of CVD, however, in many instances the differential diagnosis of chest pain is elusive, leading to a large number of ‘false’ diagnosis, which creates a very significant impact on the NHS.
In the 1980’s Rapid Access Chest Pain Clinics (RACPCs) were developed in order to systematically evaluate such patients and have now become a de facto standard of care within the NHS. The first test that is performed on patients presenting with chest pain is stress electrocardiography (ECG), where leads are attached to your chest whilst you perform exercise, either on a bike or treadmill to ascertain how the heart is functioning under stress. Whilst the results of an ECG are important some patients are not able to perform enough exercise to make an accurate diagnosis, whilst some others give false positive or false negative results. Large Clinical trials suggest that estimated incorrect diagnoses may be as high as 25%.
Doctors are well aware of this shortcoming of stress ECG’s, and therefore frequently order subsequent tests such as coronary angiography (CA) even when the stress ECG is normal. This has led to an increase in the number of invasive coronary angiography procedures with 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 (myocardial infarction - MI) and stroke. This is clearly an unsatisfactory state of affairs, from both a clinical and economic perspective.
Alternative Clinical approach: Echocardiography or Nuclear CardiologyAlternative tests to stress ECG 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 Myocardial Perfusion Imaging tests (MPI). This is an established and validated technique for the non-invasive diagnosis of CAD (Ref-2, Sabharwal et al). Though the diagnostic accuracy is improved with Nuclear Heart Scans, 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; hence its availability is restricted to only a few centres in the UK. Another useful test is a stress echocardiography, but is again limited by the shortage of skilled personnel and also there are technical difficulties which restrict its accuracy and usefulness.
The Latest in Cardiac Diagnostics
The technology in this 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 are called:
Dual-source ultra-fast CT scanner (Definition), combined with the hybrid CT+Gamma Camera (SPECT-CT) (Symbia T6), 4D- Echocardiography.
This is recognised as the latest state-of-the-art digital and remote telemetry system for exercise testing and 24 hour ECG monitoring.
This type of department has to be operated by both interventional and clinical cardiologists, radiologists, 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. CIRC works closely with the NHS, and many NHS centres use the CIRC facilities for cardiac imaging. The point 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.
Ultra-fast Dual Source CT Coronary Angiography (DS-CTA) and Calcium (CAC) Scanning:
The DS-CTA and CAC scans take less than 15 seconds, the accuracy of these scans 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 prognosis and treatment plan for the patient. With this scanner, the department has the capability to see, with great clarity, all the important branches of the coronary arteries.
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 CAD. Imaging of the heart had been a technically challenging task because of continuous motion during the cardiac cycle. Also, the ‘spatial resolution’ of traditional CT scanners were too low to assess the small and tortuous coronary arteries. However, there has been considerable improvement in this technology and this has culminated in the dual source CT (DS-CTA).
Fig1: 63 year old woman with chest pain and abnormal ECG; Dual-source
CT coronary angiogram
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Fig 1 Dual Source CT coronary angiogram showing normal coronary arteries |
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(DS-CTA) shows normal coronary
arteries. The patient was reassured and discharged to GP within 35
minutes of coming to CIRC. High cholesterol was treated with medication
alone.
The dual source CT scanners are capable of high speed imaging (ultra-fast), thereby ‘suspending’ the cardiac motion and thus allowing phenomenally clear images of the coronary arteries. 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 ‘radiation burden’ (Ref 3- Venuraja et al).
Fig 2: A 42 year old athletic man presented with fractured right side ribs following a cricket ball injury. 3 days later he complained of “wrist pain” in both hands. His stress ECG was inconclusive. His physician for a differential diagnosis referred him to Professor Lahiri at CIRC. The panel above shows the dual source CT coronary angiogram with a greater than 95% narrowing of the main right coronary artery (top left- red arrow), the in-set images (top Right) show the magnified view of the fatty ‘cholesterol’ deposit (coronary plaque) severely obstructing blood to the heart muscle. The patient was fast-tracked to the Wellington Hospital’s angiographic department for urgent treatment. The invasive coronary angiogram (bottom left panel) shows the identical blockage as seen on the DS-CTA; the blockage was dilated by coronary angioplasty and a medicated ‘stent’ was inserted by an interventional cardiologist. The coronary artery blood flow was immediately normalised reducing the risk of sudden death and heart attack. The patient was treated with medications to reduce his risk factors, and he now plays cricket for a county team.
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Fig 2. Dual source CT coronary angiogram showing severe right coronary artery narrowing
(top panel)
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Benefits of Dual Source Cardiac CT Imaging
• Imaging time is 15 seconds, total time is 35 minutes
• Early detection and improved prognosis due to earlier treatment
• Pick up "silent" disease especially important in diabetic patients
• Diagnose extent and progression of disease
• Conclusively rule-out cardiac disease or not
• Low radiation exposure, comparable to traditional CT
• Non invasive, low risk to patients
RADICAL Trial: A unique trial has been undertaken, where 1000 patients referred to 3 NHS “Chest Pain” clinics are undergoing rapid assessment of heart disease by Dual Source CT coronary angiography. The CT angiogram 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.
WHITEHALL Trial: The Whitehall trial is 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 (Ref4 – Hamer et al)
References:
1. Anand V, Lim E, Hopkins D, Corder R, Shaw L, Sharp P, Lipkin D, Lahiri A
Risk stratification in uncomplicated type 2 diabetes: Prospective evaluation of the combined use of coronary artery calcium imaging and selective myocardial perfusion scintigraphy. European Heart Journal 2006; 27, 713-721
2. Sabharwal NK and Lahiri A
Role of myocardial perfusion imaging 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 cortisol responses to mental stress are associated with coronary artery calcification in healthy men and women. European Heart J, September 2009, e-journal (advanced access publication)
Contact Professor Lahiri
If you wish to find out more about the Research programmes please contact Professor Lahiri
If you wish to find out more about the Research Programme contact BCRT
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