LUIZ SUGIMOTO

 

Professor Ot�vio Rizzi Coelho: the potential of the method is great

O Catheterization, as uncomfortable for patients as it is distressing for relatives, will continue to be effective and indispensable in the treatment of heart disease, but technology could provide, in terms of diagnosis, methods that rule out invasion of the body to assess how our hearts beat. The cardiology community has good expectations regarding the evolution of magnetic resonance imaging and multi-slice tomography, which in the medium term should provide reliable diagnoses of coronary artery problems, saving patients from invasive exams and anticipating treatments against serious events in the future.

Through catheterization (coronary angiography), the lumen of the coronary artery is observed. It's like looking through a pipe to see if something is obstructing the passage of light. But coronary disease, we now know, is not limited to blockage. First, the artery undergoes what is called “positive remodeling”, growing outward. Several inflammatory cells appear at the point of arteriosclerosis and the “pipe wall”, which was thin, thickens. As the catheter only shows the inside of the “pipe”, and not the outside, everything may appear normal. When the disease progresses, the artery begins to grow inward, obstructing the circulation of blood through the heart.

Magnetic resonance imaging is a non-invasive technique that offers an image of the external part of the coronary artery, which can help in diagnosing the disease. However, if it is relatively simple to observe a large vessel such as the aorta, the coronary artery is very small and, in addition, moves randomly according to the heartbeat and the rhythm of breathing. This requires high speed and resolution in capturing images, at a level of sophistication that current hardware and software do not yet provide. The possibility of visualizing and quantifying coronary lesions, calculating their flow and coronary reserve and also characterizing the components of the obstructive lesion (lipid center, fibrous plaque and intra-plaque hemorrhage) is invaluable and promises to revolutionize cardiology within a few years.

“CT scans easily image the brain. The problem with the heart is that it beats and the vessel follows the movement. It's as if the image we want to photograph is out of focus. The potential of the method is great, but the technique needs to improve. As in other areas, nuclear magnetic resonance tends, if not to replace, at least to complement conventional coronary angiography. We often make mistakes in such predictions, but I believe that improving the equipment will still take between five and seven years”, estimates Professor Otávio Rizzi Coelho, head of the Cardiology Area at the Faculty of Medical Sciences (FCM) at Unicamp.

Doctoral Program – Rizzi Coelho is co-supervisor of Juliano de Lara Fernandes' doctoral thesis at the Heart Institute (Incor) in São Paulo. He highlights the importance of the partnership between the two institutions – the first in the area – which made the research of Fernandes possible, a doctor graduated from Unicamp who has been monitoring volunteer patients for three years, with the aim of evaluating the applications of magnetic resonance imaging in cardiology ( see article on this page).
“Catheterization will never lose its usefulness in the diagnosis and especially in the treatment of heart conditions, as it is a less aggressive technique than surgery. In any case, it is an invasive method and subjects the patient to X-ray radiation, in addition to presenting certain limitations for diagnosis”, says Juliano Fernandes. According to him, although there are studies comparing the effectiveness of magnetic resonance imaging to that of catheterization in diagnosis, the limitation of speed in image acquisition makes the first technique still unfeasible for clinical practice.

Integrated – The other non-invasive method to try to visualize the coronary artery is multi-slice tomography, capable of obtaining images at a much higher speed. “But, like catheterization, tomography exposes the patient to radiation and uses a type of contrast that can damage the kidneys. It may be one step ahead of MRI, but it also depends on technical developments to identify coronary diseases. In any case, when it comes to diagnosis, the question is not which non-invasive technique will replace catheterization, but when”, observes Fernandes.

The Incor doctoral student adds that work with cardiac resonance is still very early, meaning it is more of a line of research than clinical application. “The studies began less than a decade ago. Currently, resonance is already routinely used clinically to observe the anatomy of the heart, ischemia and infarct sizes. In this sense, the method is already bringing relief to patients by freeing them from having to undergo a series of tests – stress tests, scintigraphy, electrocardiogram – integrating them into one.”

Partnership between Unicamp and Incor The patient who arrives at the Instituto do Coração (Incor) with a heart attack called “sem supra”, or high-risk unstable angina (high probability of coronary complications in the future), receives initial treatment and can be referred to the heart machine. MRI. In the image of the coronary artery, a cross-section is made, which allows measuring the thickness of the wall, the size of the inflamed area and the light that passes through the vessel. “These studies with volunteer patients aim to verify whether the fact that the artery is thicker – together with characteristics of the arteriosclerosis plaque that MRI is also capable of showing externally – is a bad prognosis for the person, increasing their risk for a heart attack or another cardiac event”, informs Juliano de Lara Fernandes. After six months, the patient undergoes the same MRI exam, and the results are compared. To date, 20 patients have been included in the study, seven of whom have already completed the six-month follow-up. “What we have noticed is that the thickness decreases after the acute event, the inflammatory phase improves over time. In other words, magnetic resonance imaging is capable of anticipating information about an abnormality at that point in the coronary artery, adding information to an invasive technique such as catheterization”, says Fernandes, with the exception that this method cannot yet be inserted into clinical practice, due to the lack of hardware and software that capture images in a satisfactory time, as previously described. In Campinas – Juliano Fernandes' doctoral thesis is supervised by professor Carlos Vicente Serrano Jr., from the Faculty of Medicine at USP, and in collaboration with doctors José Rodrigues Parga Filho, Luís Francisco Avila and Carlos Eduardo Rochitte, from the Magnetic Resonance Section of the Inc. At Unicamp, the doctoral student is co-supervised by professor Otávio Rizzi Coelho, from the Department of Clinical Medicine, and professor Maria Heloísa Blotta, from the Department of Clinical Pathology, both from FCM. The part of the thesis aimed at identifying information in the coronary artery was developed exclusively at Incor, whose magnetic resonance machine meets the necessary specifications. Similar equipment provided by a private clinic in the city brought the possibility of the research with volunteers being extended to Campinas. The second part of the studies refers to immunological markers, in conjunction with Unicamp. Fernandes informs that this work will be sent to the World Congress of the Society of Cardiac Resonance, scheduled for February 2004, in Barcelona.