COMMENT: The future of ultrasound in cardiology
Since its humble beginnings in the early 1950s, echocardiographs, or ECHOs as they are more commonly known, have become an invaluable tool for cardiologists. But the use of ultrasound in the medical speciality of cardiovascular medicine is not limited to echocardiographs. Ultrasound has a much broader range of applications in the field of cardiovascular medicine. From intra-operative guidance for surgeons to screening for cardiovascular diseases, ultrasound opens doors and allows us to ‘see the unseen’. RACHID REDOUANE of ultrasound manufacturer, ALOKA Europe, explains
WITH pathological knowledge and the cost of healthcare increasing, preventative medicine is becoming central to healthcare policy. Since we now understand many of the risk factors and stages of disease progression, identifying these early warning signs in patients allows treatment to start earlier and stops disease progression sooner.
Cardiovascular disease is a modern disease, which is becoming startlingly common among the exercise-shy, salt-eating, cigarette-smoking, fast food addicts of Western countries. Being a risk factor in itself for a number of deadly conditions, such as strokes, heart attacks and kidney failure, early detection of any arterial disease is of paramount importance. The vascular degeneration associated with diabetes (atherosclerosis and peripheral vascular disease) is very significant considering 200 million people world wide suffer from diabetes. One particular subset of patients at risk of arterial disease is those who are HIV-positive and have been on anti-retroviral therapy for a long period of time. The metabolic and cardiovascular side-effects of these drugs can cause atherosclerotic plaques to develop.
Since we now understand many of the risk factors and stages of disease progression, identifying these early warning signs in patients allows treatment to start earlier and stop disease progression sooner
Before ultrasound provided a diagnostic solution, diagnosis of vascular disease was made by an angiogram; the intra-venous injection of contrast medium followed by an X-ray to see how open the blood vessels are; or by using MRI scans. However, a number of new techniques have been developed to detect vascular degeneration using ultrasound.
Reduced arterial compliance is the first detectable sign, followed by increases in IMT (intima media thickness; the thickness of arterial walls)1. High-resolution ultrasound systems are required to distinguish this level of detail. Because these ultrasound imaging techniques are non-invasive and accurate for detecting even sub-clinical levels of vascular disease, they could be easily applied to screening programmes.
Diagnosis and detection
For many cardiovascular diseases, rapid diagnosis is very important to allow treatment to be quickly administered to minimise damage to the heart or other organs; potentially saving lives. For example, deep vein thrombosis (DVT) needs rapid diagnosis and treatment, since up to 50% of patients will progress to having fatal pulmonary embolisms (a blockage in a main blood vessel in the lungs, preventing normal gas exchange)2. The standard treatment of anticoagulants is effective, but only if administered quickly. Diagnosis is usually made with compression ultrasound (ultrasound imaging with compression of the veins in question) and a new two-point compression technique focuses on high probability areas, which reduces the study time down to less than five minutes, from a two- hour wait with previous radiation or contrast-medium exposure dependant techniques without compromising on sensitivity or specificity.
Measuring the rate of blood flow from the heart during operations can reduce complications and speed up a patient’s recovery. Recent NICE approval of this will lead to millions of pounds of savings and numerous benefits for patients
The detection and diagnosis of foetal cardiac abnormalities is very challenging because of the small size of foetal structures and the difficulties of imaging through the womb. But significant ultrasound advancements have been made. In particular, STIC (spatiotemporal image correlation – real time imaging) has been developed since 20033. A lot of the fine imaging processing, such as 3D volume rendering and tomographic ultrasound imaging (creating ‘slices’ to view internal organ structure), can be done off-line, minimising scanning time. Four main improvements come with these advancements; increased accuracy for diagnosis since all planes and depth can be viewed; offline data allows expert review later; unique functional parameters can be evaluated; and patients experience better counselling and interdisciplinary consultations with these more-comprehensible images. Additionally, the generated images have an added use as valuable teaching material, too.
Cardiovascular disease affects both the mechanics and fluid dynamics of the cardiovascular system.To improve clinical models and diagnostic processes for many cardiovascular diseases, ultrasound has been used to provide new parameters such as wall motion and blood flow to study the mechanics and fluid dynamics of the cardiovascular system. With the ALOKA Alpha 10 system, for example, wall motion can be reliably detected at different positions and compared simultaneously using the Free Angular M-Mode (FAM).
Surgical settings
Echocardiograms have been central to cardiology for a number of years now, but the use of ultrasound is not limited to just external imaging of the heart
Ultrasound has become an invaluable tool for guiding surgeons and clinicians through a number of invasive procedures, from catheter and stent implantation to foetal cardiac surgery. These operations and procedures are tricky and can be dangerous, but with ultrasound guidance the surgeon can operate with increased accuracy, passing on benefits to the patients. For example, stents are a good and frequent solution to vessel occlusion. Ultrasound-guided installation of these stents increases the effectiveness of this procedure, eliminating the need for post-operative systemic anti-coagulation therapy.
Accurate diagnosis of important risk factors using ultrasound can avoid deaths during cardiac surgery. Around 80% of cardiac surgical patients have some degree of atherosclerosis in the descending aorta and are therefore at risk of peri-operative strokes or systemic emboli4. If accurately diagnosed, an alternative surgical technique can be used. There are two possible methods to detect the degree of atherosclerosis once the chest is opened; transesophageal (TEE – using a probe inserted down the oesophagus) or epiaortic ultrasound (using a probe placed over the exposed aorta). Epiaortic imaging can generate images of the proximal descending aorta and in both transverse and longitudinal planes, and was found to be the most suitable technique to diagnose aortic atherosclerosis above TEE and palpation. Before this new technique, strokes would have been far more common in cardiac surgery and lives lost as a result.
Surgical patients can also benefit from ultrasound-based intra-operative blood flow monitoring. Measuring the rate of blood flow from the heart during operations can reduce complications and speed up a patient’s recovery. Recent NICE approval of this will lead to millions of pounds of savings and numerous benefits for patients5. Further developments stretch as far as pre-natal cardiac medicine. Human foetal cardiac intervention is a very challenging area of cardiac surgery. Further uses of intra-operative ultrasound have been found in foetal surgery and recent research in preclinical models has shown that ultrasound-guided techniques are a viable option for foetal cardiac catheterisation.
Ultrasound has a place in the operating theatre as well as clinics and wards, guiding a range of procedures and giving patients the best possible chance of a speedy return to full health
Echocardiograms have been central to cardiology for a number of years now, but the use of ultrasound is not limited to just external imaging of the heart. Without the continuous innovation from the ultrasound community, these new developments would never have been brought to market. As a result, the quality of cardiovascular imaging has greatly improved, affording clinicians an invaluable insight into any structural abnormalities from foetus to adult.
Ultrasound has a place in the operating theatre as well as clinics and wards, guiding a range of procedures and giving patients the best possible chance of a speedy return to full health. Increased uptake of the technology by more clinicians will drive further innovative applications of ultrasound. At ALOKA we are working with leading professors to bring innovation in ultrasound to the market quicker. For example, we are working with Dr Lemasale, a venous disease specialist; Professor van Bibra, who is developing myocardial contrast echocardiography; and Professor Filice, who is researching interventional ultrasound, covering a broad range of ultrasound areas within cardiovascular medicine.
References
1 van Vonderen, M. G. A., Smulders, Y. M., Stehouwer, C. D. A., Danner, S. A., Gundy, C. M., Vos, F., Reiss, P., Agtmael, M. A. 2009. Carotid Intima-Media thickness and Arterial Stiffness in HIV-Infected Patients: The Role of HIV, Antiretroviral Therapy and Lipodystrophy. Journal of Acquired Immune Deficiency Syndromes, 50(2):153-161
2 Grimm, L. 2011. Bedside Ultrasonography in Deep Vein Thrombosis. Medscape Reference, 29 March 2011
3 Shen, O., Yagel, S. 2010. The added value of 3D/4D ultrasound imaging in fetal cardiology: has the promise been fulfilled? Ultrasound Obstet Gynecol 35: 260–262
4 Davila-Roman, V. G., Barzilai, B., Wareing, T. H., Murphy, S.F., Schechtman, K. B., Kouchoukos, N. T. 1994. Atherosclerosis of the ascending aorta. Prevalence and role as an independent predictor of cerebrovascular events in cardiac patients. Stroke, 25:2010-2016
5 Walsh, F. 2011. Blood flow monitor 'could save NHS £400m a year'. BBC, 30 March
