ORIGINAL PAPER Index of biventricular interdependence calculated using cardiac MRI: a proof of concept study in patients with and without constrictive pericarditis Nandan S. Anavekar • Benjamin F. Wong • Thomas A. Foley • Kalkidan Bishu • Arunark Kolipaka • Chi Wan Koo • Masud H. Khandaker • Jae K. Oh • Phillip M. Young Received: 3 May 2012 / Accepted: 12 July 2012 / Published online: 21 July 2012 Ó Springer Science+Business Media, B.V. 2012 Abstract We sought to propose a magnetic resonance (MR) imaging-derived index of biventricular interdepen- dence as a diagnostic parameter to distinguish patients with surgically-confirmed pericardial constriction from those without. Free-breathing real time MR pulse sequences of seventeen subjects with surgically proven constrictive pericarditis and thirty-five patients referred for clinically- indicated cardiac MR examinations but without docu- mented constriction were analyzed using a novel index of biventricular interdependence. Cross-sectional biventricu- lar areas at end diastole using the epicardial surface were traced at the mid left ventricular level at end-inspiration and end-expiration and an index of biventricular interde- pendence, defined as the ratio of (biventricular end-dia- stolic area at end-inspiration)/(biventricular end-diastolic area at end-expiration) was calculated for each subject. The mean index for both groups was calculated and results were statistically compared. The index of biventricular interde- pendence approximated unity (mean index 1.03 ± 0.03 SD) in patients with surgically confirmed pericardial con- striction, indicating similar biventricular area at end- inspiration and end-expiration, and was significantly lower than in individuals without constrictive pericarditis (mean index 1.28 ± 0.10 SD; p \ 0.0001). The MR-derived index of biventricular interdependence was significantly different between subjects with surgically-confirmed peri- cardial constriction and subjects where pericardial con- straint was not suspected and may serve as a useful metric in the hemodynamic assessment of patients with a potential diagnosis of constrictive pericarditis. Keywords Index  Ventricular interdependence  Constrictive pericarditis Introduction The critical role of end diastolic volume in regulating the work of the heart has been known for over a century, largely due to the work of Ernest Henry Starling, who described this relationship in a series of papers between 1912 and 1914 [1]. It has also long been established that changes in intrapleural pressures that accompany normal respiration influence car- diac function via changes in cardiac volumes and systemic and pulmonary pressures [2–5]. Additionally, it is well known that the left and right ventricles are functionally intertwined [6] because of the in-series arrangement of the ventricular circulation, the presence of an interventricular septum that contains muscle fibers circumscribing both ventricles, and by the presence of a deformable pericardium surrounding both ventricles as well as the atria. The hemodynamic changes observed in constrictive peri- carditis are sequelae of a dissociation of intrathoracic and N. S. Anavekar (&)  B. F. Wong  K. Bishu  M. H. Khandaker  J. K. Oh Department of Medicine and Division of Cardiovascular Disease, Mayo Clinic, 200 1st street SW, Rochester, MN 55905, USA e-mail: anavekar.nandan@mayo.edu T. A. Foley  P. M. Young Department of Radiology, Mayo Clinic, Rochester, MN, USA A. Kolipaka Department of Radiology, Ohio State University Medical Center, Columbus, OH, USA C. W. Koo Department of Radiology, Mayo Clinic Health System, Mankato, MN, USA 123 Int J Cardiovasc Imaging (2013) 29:363–369 DOI 10.1007/s10554-012-0101-x