Comprehensive Annular and Subvalvular Repair of Chronic Ischemic Mitral Regurgitation Improves Long-Term Results With the Least Ventricular Remodeling

Abstract

Background Undersized ring annuloplasty for ischemic mitral regurgitation (MR) is associated with variable results and >30% MR recurrence. We tested whether subvalvular repair by severing second-order mitral chordae can improve annuloplasty by reducing papillary muscle tethering. Methods and Results Posterolateral myocardial infarction known to produce chronic remodeling and MR was created in 28 sheep. At 3 months, sheep were randomized to sham surgery versus isolated undersized annuloplasty versus isolated bileaflet chordal cutting versus the combined therapy (n=7 each). At baseline, chronic myocardial infarction (3 months), and euthanasia (6.6 months), we measured left ventricular (LV) volumes and ejection fraction, wall motion score index, MR regurgitation fraction and vena contracta, mitral annulus area, and posterior leaflet restriction angle (posterior leaflet to mitral annulus area) by 2-dimensional and 3-dimensional echocardiography. All groups were comparable at baseline and chronic myocardial infarction, with mild to moderate MR (MR vena contracta, 4.6±0.1 mm; MR regurgitation fraction, 24.2±2.9%) and mitral annulus dilatation (P<0.01). At euthanasia, MR progressed to moderate to severe in controls but decreased to trace with ring plus chordal cutting versus trace to mild with chordal cutting alone versus mild to moderate with ring alone (MR vena contracta, 5.9±1.1 mm in controls, 0.5±0.08 with both, 1.0±0.9 with chordal cutting alone, 2.0±0.7 with ring alone; P<0.01). In addition, LV end-systolic volume increased by 108% in controls versus 28% with ring plus chordal cutting, less than with each intervention alone (P<0.01). In multivariate analysis, LV end-systolic volume and mitral annulus area most strongly predicted MR (r2=0.82, P<0.01). Conclusions Comprehensive annular and subvalvular repair improves long-term reduction of both chronic ischemic MR and LV remodeling without decreasing global or segmental LV function at follow-up.

Chronic Ischemic Mitral Regurgitation

“…Importantly, they also demonstrated preservation of LV function in the chordal-cutting group, a concern of previous sheep model investigations from Craig Miller's group. 16,17 The possible reasons for the discrepant findings between the current article and those from Craig Miller's group are extensively discussed by Szymanski et al 11 It is interesting to note, however, that the findings of Szymanski's sheep model work closely reflect our clinical observations from a nonrandomized study. 18 We observed preserved LV function, despite a worse preoperative ejection fraction, in a group of 43 patients undergoing the chordal-cutting procedure for cIMR.…”

“…In the current issue of Circulation, Szymanski et al 11 have revisited a concept that has existed for several years: the chordal-cutting procedure for cIMR. The working group of Robert Levine originally suggested that dividing secondary chords was a simple method of increasing mitral leaflet mobility, thereby limiting the amount of apical displacement and leaflet tethering that is pathognomonic of cIMR.…”

“…11 Their model involves ligation of the second and third obtuse marginal arteries and consistently results in myocardial infarction and cIMR, but it is labor intensive and associated with a high mortality. The authors are to be commended for accurately emulating the restrictive annuloplasty operation with implantation of a complete, rigid ring that is 2 sizes smaller than the measured annular size.…”

The power of ultrasound: treating secondary MR with sound waves

“…Not as clinically established, but shown to be safe and effective is to directly target the chordal apparatus by cutting secondary chordae attaching to the leaflet bodies to relieve their tethering and to restore a greater surface for leaflet coaptation 11,12 ( Figure 1B). Such chordal cutting reduces both MR and its associated LV remodelling 13 and has been successfully applied by several surgical groups. 14 -16 The pathological changes observed in chordae post-infarction 7 and the recent reported relation between secondary MR and chordal shortening, imposing additional restriction on the tethered leaflets, lend further support to the potential benefits of chordal cutting to relieve such MR. 17 The current paper reports a proof of concept for using pulsed cavitational focused ultrasound (histotripsy) to cut chordae non-invasively guided by real-time 3D echocardiography.…”

“…(v) Acute and long-term durability of MR reduction will need to be demonstrated as this noninvasive approach of chordal cutting does not address the dilated mitral annulus, although in vivo data so far indicate that it relieves progressive LV remodelling. 13 Cutting chords by this technique may also be a beneficial partner procedure with transcatheter MV repair strategies such as the MitraClip or the Cardioband. Such a combined and complementary less-invasive MV repair approach will target leaflet tethering as well as annular dilatation and thus should effectively restore MV leaflet coaptation; the less-invasive approach can allow more patients to benefit from relief of tethering than is currently possible.…”