Animal models of mitral regurgitation induced by mitral valve chordae tendineae rupture.

BACKGROUND AND AIM OF THE STUDY: Mitral regurgitation (MR) is a common valvular disease throughout the world. Various diagnostic techniques have been developed to assess the causes and severity of MR, and the therapeutic approaches to this disease have been widely documented. However, treatments for chronic MR remain controversial, and various animal models of chronic MR (including chordae tendineae rupture, rapid pacing and ischemia) have been developed to study the pathophysiology and therapeutic approaches to this condition. The study aim was to review the animal MR models that have been developed using a mitral valve chordae tendineae rupture technique. METHODS AND RESULTS: Among the animals used for these investigations, dogs and sheep have been most commonly used as models of MR induced by mitral valve chordae tendineae rupture, mainly due to considerations of cardiac size. Chordae tendineae cutting is performed using either closed- or open-chest techniques. In the closed-chest model, long flexible grasping forceps are positioned percutaneously in order to tear the mitral valve chordae. In the open-chest model, cardiopulmonary bypass is performed, and either selected chordae are cut under direct visualization or a non-specified number of chordae are cut, using a metal device inserted through the left ventricular apex. Whichever model is used, MR has been found to become chronic at three to six months after the induction of MR by chordae rupture. The reported mortality and complication rates of these models are high. CONCLUSION: In the long term, the experimental evolution of chronic MR is similar to the evolution occurring naturally in patients suffering from the condition. Hence, these models could be useful in understanding the disease better, and in testing new therapeutic modalities. The present review summarizes the physiological effects of each of these techniques, and compares the advantages and disadvantages of each procedure.