Introduction:

Ischemic mitral regurgitation (IMR) is a frequent complication of left ventricular (LV) global or regional pathological remodeling due to chronic coronary artery disease. It is not a valve disease but represents the valvular consequences of increased tethering forces and reduced closing forces. IMR is defined as mitral regurgitation caused by chronic changes of LV structure and function due to ischemic heart disease and it worsens the prognosis. It is important to distinguish between primary MR due to organic disease of one or more components of the mitral valve apparatus and secondary MR which is not a valve disease, but represents LV disease. Secondary MR is defined as functional MR, due to LV remodeling by cardiomyopathy or coronary artery disease. In the latter clinical setting, secondary functional MR is called IMR.

Pathophysiology:

Depending on echocardiography parameters such as leaflet motion, origin, and characteristics of regurgitant jets, IMR is classified into asymmetric and symmetric tethering patterns. 

Asymmetric tethering pattern: Asymmetric tethering is commonly associated with inferolateral infarcts, mild-moderate increased tenting areas, inferolateral remodeling, and a MR jet that is posterior directed due to an anterior mitral valve leaflet overrid.

Symmetric tethering pattern: Symmetric tethering is associated with large anterior or multiple infarcts, greater eccentric spherical remodeling, bi-leaflet apical tethering, ventricularization of leaflet coaptation, larger tenting areas, and a central jet direction. Annular dilatation increases the potential severity of MR associated with asymmetric or symmetric tethering.

Evaluation:

The main risk in patients with functional IMR is to misdiagnose or underestimate MR because whose clinical presentation is ischemic cardiomyopathy with a low intensity systolic murmur. In patients with organic MR, the intensity of cardiac murmur is generally well correlated with the regurgitant volume, but in severe functional IMR, the cardiac murmur is of low intensity, because of low output. Hence, a careful Echocardiography examination is the only means to assess correctly the mechanism and volume of the regurgitation.

Echocardiography is important in patients with IMR to quantify MR, to elucidate the mechanism of MR and to exclude any abnormality in the mitral valve leaflets. Perioperative transesophageal echocardiography (TEE) provides additional information, especially when TTE gives suboptimal results.

LV angiography frequently associated with coronary angiography is considered as a reference method for the assessment of the volume of MR. However, it has some limitations due to the influence of loading conditions. Quantitative Doppler echocardiography provides more objective data regarding the prognostic role of the regurgitation than ventricular angiography.

Therapeutic:

Medical treatment: Medical therapy in patients with IMR is generally aiming at preventing, delaying, or reverting LV remodeling and heart failure, as well as to prevent myocardial ischemia. There are no specific recommendations specifically targeted to patients with IMR, beyond usual medical treatment of heart failure including angiotensin-converting enzyme inhibitors (ACEIs), β-blockers, spironolactone, nitrates, and diuretics. The combination of β-blockers and ACEIs inhibits progressive LV remodeling, and is associated with a significant reduction in MR severity in patients with chronic heart failure.

Cardiac resynchronization therapy: Cardiac resynchronization therapy (CRT) has a beneficial effect on functional MR, through reverse LV remodeling, improved LV systolic function, increased closing force, and improved coordinated timing of mechanical activation of PM. The benefit of CRT is limited in patients with IMR, especially in those with important LV dilation and leaflet tethering, or in the presence of a scar at the LV pacing lead tip, which may impede resynchronization, particularly in the posterolateral LV segments.

Thrombolysis and Percutaneous coronary interventions: Thrombolysis reduces the incidence of MR following MI through a reduction in local remodeling. Percutaneous coronary interventions (PCIs) also reduce the incidence and severity of MR following MI. Isolated PCI without correcting MR is not an adequate option for the treatment of patients with IMR.

Surgical management: Surgical management of IMR has primarily comprised revascularization with or without the addition of MVR with a variety of techniques including suture, band or ring annuloplasty, or mitral valve replacement.

Other techniques for correction of Ischemic Mitral Regurgitation: The Acorn CorCap Cardiac Support Device, Coapsys device, Chordal cutting, subvalvular repair, approximation of the papillary muscles, percutaneous mitral valve repair.

Conclusion:

It is a great challenge to manage IMR. The evaluation of IMR can be accurate by perioperative TEE. Surgical revascularization alone with CABG is sufficient in patients with mild MR, but in the case of severe IMR, CABG along with valve repair can improve functional capacity, LV reverse remodeling, MR severity and BNP levels. The role of concomitant repair in case of moderate IMR is still not clear. The ischemic mitral valve is repaired during CABG with the use of an undersized complete rigid annuloplasty ring. Subvalvular techniques may be added in addition to annuloplasty for the correction of IMR. MVR with Bio-prosthetic valve and total chordal preservation is probably the treatment of choice in severe and complex IMR.

 

Source

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5661313/ Praveen Kerala Varma, Neethu Krishna, Reshmi Liza Jose,1 and Ashish Narayan Madkaiker