The Centro Nacional de Investigaciones Cardiovasculares (CNIC) has coordinated the first international consensus document providing guidelines on the conduct of MRI studies after a heart attack in clinical trials or experimental models. The document, published this week in the Journal of the American College of Cardiology, concludes that the main outcome parameter in studies assessing new treatments should be absolute infarct size: the percentage of the left ventricle that is irreversibly damaged. The recommended timing for MRI is between three and seven days after the heart attack.
The document addresses the need within the cardiovascular community for guidance on the best protocols, the best techniques, and the most appropriate situations for conducting a MRI study after a heart attack.
MRI is one of the best methods for studying the heart after an infarction, said Valentín Fuster, MD, director of the cardiovascular institute and medical director at Mount Sinai Hospital in New York. He said MRI allows the study of the heart anatomy, function, and tissue composition in a very precise way without exposing the patient to radiation, and MRI is the ideal method for assessing the effects of new treatments.
"However, until now the community has lacked consistent recommendations on the specific procedures to follow after an acute myocardial infarction in order the assess the effect of these treatments," said Fuster, one of the lead scientists on the document.
Consistency in the use of MRI after a heart attack is important for the clinical community because it is difficult to compare clinical studies that use MRI to assess a principal outcome because the studies use widely different protocols, said Borja Ibañez, MD, first author on the document and the clinical research director at the CNIC.
"Myocardial infarction affects millions of people in the world every year, and this is, therefore, a highly active field of research," Ibañez said. "Because of this, the implications of the new consensus document are enormous.”
In addition to establishing absolute infarct size as the main outcome measure to assess in studies evaluating new treatments, the document recommends that MRIs should be carried out between days three and seven after the infarction. Study co-author Dr Rodrigo Fernández-Jiménez commented that “the scientific evidence indicates that the period between three and seven days after an infarction because that is when MR parameters are more stable and less affected by rapid changes occurring in the heart as it attempts to repair itself. This time window is also practical, the authors note because most patients stay in the hospital for at least three days after having a heart attack.
Another author on the document is Javier Sánchez-González, a physicist from Philips based at the CNIC, where he coordinates the joint development program in cardiovascular imaging. Sánchez-González said new techniques for mapping the heart are helping doctors to understand processes in the infarcted heart that previously could only be observed by pathological anatomy after death.
"The ability to observe these processes in living patients using a noninvasive technology is without a doubt a major medical advance," Sánchez-González said.
The document’s contents were defined during an international meeting held at the CNIC with support from Philips. The meeting brought together a multidisciplinary group of 16 experts in the field from the United States, Canada, the UK, France, Germany, Sweden, the Netherlands, Greece, Switzerland, Singapore, and Spain.