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Tagged MRI is challenging conventional views regarding atherosclerosis and latent heart problems in patients that otherwise appear healthy and present no symptoms. By tagging different tissue prior to a scan, researchers can obtain a detailed view of the movement and function of those tissues. Now, by studying subjects in the Multi-Ethnic Study of Atherosclerosis (MESA) project, Joao Lima of the Department of Radiology, at Johns Hopkins University, in Baltimore, Maryland, and colleagues there and in five other centres, have investigated whether an increase in the thickness of the carotid artery (so-called intima-media thickness, or IMT) can be related to reduced heart function. The MESA study is a prospective observational study including four ethnic groups and the participants have no clinical cardiovascular disease. Cardiologists are usually taught that atherosclerosis causes heart problems leading to heart attack or chest pain or other symptoms. However, this research shows that stresses and strains on the heart caused by congestion in the main arteries can affect the function of the heart's left ventricle and so heart function before symptoms become apparent. Thickness of the carotid artery, however, has been well-established as a marker for disease in patients before symptoms appear. The present research takes this concept a step further by using tagged MRI to correlate IMT with heart function. The researchers have found that higher carotid IMT induces strain on the heart muscle leading to poorer systolic and diastolic myocardial function. This, Lima explains, indicates a direct relationship between subclinical atherosclerosis and incipient myocardial dysfunction. "This study challenges the notion that atherosclerosis, the most common aetiology of heart failure in the industrialized world, impairs cardiac function by causing discrete clinical episodes of myocardial infarction or ischaemia," explains Lima. Instead, the team has shown that increased carotid IMT is in fact associated poorer function in specific regions of the heart muscle. Tagged MRI can, in other words, reveal a latent cardiovascular problem in people without apparent symptoms and so provide an early warning that may be acted on by helping them alter nutrition and exercise patterns, reduce other risk factors such as smoking and alcohol consumption, or provide cardioprotective drugs. Related links:
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Lima tagging at the heart strings |
