Chronic ischaemic mitral regurgitation. Current treatment results and new mechanism-based surgical approaches☆

Abstract

Chronic ischaemic mitral regurgitation (CIMR) remains one of the most complex and unresolved aspects in the management of ischaemic heart disease. This review provides an overview of the present knowledge about the different aspects of CIMR with an emphasis on mechanisms, current surgical treatment results and new mechanism-based surgical approaches. CIMR occurs in approximately 20-25% of patients followed up after myocardial infarction (MI) and in 50% of those with post-infarct congestive heart failure (CHF). The presence of CIMR adversely affects prognosis, increasing mortality and the risk of CHF in a graded fashion according to CIMR severity. The primary mechanism of CIMR is ischaemia-induced left ventricular (LV) remodelling with papillary muscle displacement and apical tenting of the mitral valve leaflets. CIMR is often clinically silent, and colour-Doppler echocardiography remains the most reliable diagnostic tool. The most commonly performed surgical procedure for CIMR (restrictive annuloplasty combined with coronary artery bypass grafting (CABG)) can provide good results in selected patients with minimal LV dilatation and minimal tenting. However, in general the persistence and recurrence rate (at least MR grade 3+) for restrictive annuloplasty remains high (up to 30% at 6 months postoperatively), and after a 10-year follow-up there does not appear to be a survival benefit of a combined procedure compared to CABG alone (10-year survival rate for both is approximately 50%). Patients at risk of annuloplasty failure based on preoperative echocardiographic and clinical parameters may benefit from mitral valve replacement with preservation of the subvalvular apparatus or from new alternative procedures targeting the subvalvular apparatus including the LV. These new procedures include second-order chordal cutting, papillary muscle repositioning by a variety of techniques and ventricular approaches using external ventricular restraint devices or the Coapsys device. In addition, percutaneous transvenous repair techniques are being developed. Although promising, at this point these new procedures still lack investigation in large patient cohorts with long-term follow-up. They will, however, be the subject of much anticipated and necessary ongoing and future research.