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A GERMAN RESEARCH TEAM FINDS HIDDEN MYOCARDIAL INFARCTION USING CARDIAC MRI

Coronary artery disease (CAD) affects millions around the world and is the leading cause of morbidity and mortality in many countries. It occurs when cholesterol deposits and inflammation restrict blood flow to the heart.

A German team has made a bounding leap in diagnosing serious heart conditions which may offer patients a second chance. The team is using a technique called late gadolinium enhancement (LGE) in patients with coronary artery disease to find myocardial infarctions (MI) that are hidden to traditional methods.

Although most infarctions (heart attacks) occur with classical symptoms like sharp pain in the heart region and/or arm, difficulty breathing and fear of dying, there are so-called silent heart attacks that can still influence prognosis.

"These patients represent almost half of the patients found to have MI. Thus, silent MI has to be regarded as a frequent finding in LGE cardiac MRI," noted Dr. Bernhard Klumpp and colleagues from the department of radiology at Eberhard Karls University Tübingen. "Although these MI are smaller than apparent MI, they are of clinical relevance as the presence of MI is linked to an unfavorable prognosis."

Its known from clinical data that many patients who suffer from coronary artery disease (CAD) have a silent progression of the disease. This means that they may have a heart attack and never know about it. This also has serious effects on the prognosis, which is why these patients must be strictly monitored and corresponding tactics should be employed.

In this study, however, Klumpp et al. decided to study silent heart attacks in patients showing symptoms of coronary disease. Two hundred and forty patients were studied, which included 182 men and 58 women. Of the 240, 181 had previous history of CAD while 76 experienced a heart attack in the past. All patients either had previous or new symptoms of CAD or known CAD with recurring or increasing symptoms.  

Patients underwent myocardial perfusion, functional and viability imaging using a 1.5 Tesla MRI system (Magneto Sonata and Avanta, Siemens). Localized contrast enhancement of a delineated shape with its base at the endocardial border on LGE images was defined as MI. The images were then classified by their size and location. The supplying coronary artery and localization were described according to the American Heart Association’s recommended 17 segment model. The degree of infarction was determined semiquantitatively by the number of affected segments and location was described by the number of each damaged segment.

Patients with confirmed MRI on LGE cardiac MRI were divided into two groups, the first were patients with previous history of MI, and the second, patients with no history of MI. Subsequently, both groups were compared and analyzed by size, location of MI, and left ventricular function.

Pic. 1. Total number of segments involved in myocardial infarction for each vessel territory compared for patients with apparent (group one) and with silent (group two) myocardial infarction. (LAD = left anterior descending artery, RCA = right coronary artery, LCX = left circumflex artery). Image courtesy of Dr. Bernhard Klumpp.

Coronary artery disease was confirmed in 210 patients, 118 of which (56%) had confirmed MI on LGE cardiac MRI, and 110 of the 118 had previous history of CAD. Only 69 of the 118 patients (58%) had history of MI. Group one’s mean left-ventricular ejection fraction was 49 ± 11%, (ranging from 18% to 74%), and the size of MI was 4.9 ± 3. Group two, on the other hand, had a mean left ventricular ejection fraction of 52 ± 11%, (ranging from 22% to 72%), and an MI size of 3.2 ± 2.1.

The results showed that patients in group two were much older and MI was considerably smaller in size than in group one. These findings coincide with previously performed studies. Myocardial infarction in group two (silent MI) occurred much more often in the left circumflex artery (LCX) than in the left anterior descending artery (LAD). Silent MI was found in 27% of patients with a history of CAD and in 23% of patients that were found to have CAD during the course of the study. In other words, 42% of patients had no knowledge of having MI and were never diagnosed with MI in the past before confirmation by LGE cardiac MRI.

These findings imply that size of MI directly affects the probability of classic symptoms onset which in the group with a history of MI was significantly larger. Also, the location in cases of silent MI was mostly concentrated in the LCX region, as opposed to group one, where the location was predominantly the anterior wall supplied by the LAD coronary artery.

"Our results confirm that chronic MI is a frequent finding in patients with CAD. Yet, 42% of all MI depicted by LGE cardiac MRI throughout the study were not known before," the authors wrote. "These patients with clinical occult MI represent 23% of all patients found to have CAD in the study and 27% of patients with previously known CAD. They have to be regarded as patients at increased risk for major adverse cardiac events."

CAD is a very serious disease that affects people of all countries and social status. Oftentimes, MI is the first symptom of CAD, which is why studying myocardial viability is extremely important and can affect prognosis and risk of MI or recurrent MI.

03.08.2015

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