Because chordae normally preserve LV-mitral continuity and function [15, 16], some concerns have been raised regarding any possible influence of this chordal cutting technique on LV function. In an elegant experimental publication [32], Messas ’s team evaluated global and segmental LV function in normal sheep before and immediately after cutting pre-instrumented chords in the closed beating heart, using the technique of Rodriguez et al. [33] This eliminates cardiopulmonary bypass between the pre-cutting and post-cutting stages to maintain constant hemodynamics. To avoid confounding factors, this maneuver was performed without altering myocardial perfusion (no infarction) or loading conditions. Global and segmental contractility were assessed using 3-dimensional (3D) echocardiography, Doppler tissue velocities and strain rate, and sonomicrometer pressure-volume loops and segmental strain.

Under cardiopulmonary bypass, wires were placed around the two central basal chordae and brought outside the heart, which was restarted. Hemodynamic and imaging data were collected before and after chordal cutting by radiofrequency ablation using those wires. Segmental contractility was assessed invasively using sonomicrometers and noninvasively using Doppler tissue velocity and strain rate. They found no changes from before to after chordal cutting in LV end-diastolic and end-systolic volume, ejection fraction (54.2 ± 1.8 versus 54.2 ± 2.7 %, P = 0.96), systolic ventricular elastance (7.28 ± 1.68 versus 7.66 ± 2.11 mmHg/mL, P = 0.64), preload-recruitable stroke work (46.6 ± 7.7 versus 50.2 ± 10.7 mmHg, P = 0.76), and LVdP/dt (1,480 ± 238 versus 1,392 ± 250 mmHg/s, P = 0.45). Doppler tissue velocities and longitudinal strain rates surrounding the papillary muscles were unchanged, as were sonomicrometer longitudinal and mediolateral absolute strains. No wall motion abnormalities were visible around the papillary muscles, and no MR developed. In this experimentation, we find no evidence for acutely decreased global or segmental LV contractility with chordal cutting. This absence of adverse effects is consistent with long-term clinical experience with cutting these chords in valve repair.

Several additional lines of evidence suggest the safety of this procedure. In chordal-sparing valve replacement, only the posterior leaflet and its chordae are most commonly preserved, and EF is typically maintained. For many years, these basal chordae have been disconnected in routine repair of rheumatic and myxomatous valves without adverse effects [34]. In isolated perfused hearts, severing all the basal chordae only slightly decreased shortening of a single myocardial segment [35]. In therapeutic applications, however, only two chords are cut, and although they individually bear more stress, Kunzelman and Cochran have suggested that “it may be possible surgically to remove basal chordae without seriously compromising mitral valve function.” [36] In ischemic hearts, if MR can be reduced, the dominant effect of ventricular decompression may be increased contractile function due to reduced wall stress. Relief of ischemic MR without prolapse or decreased LV global function has been confirmed in sheep with acute infero-basal infarction (unchanged LVEF, pressure, and dP/dt) [30]. LVEF was also preserved after chordal cutting 3.3 months after infarction, or by chordal cutting acutely after infarction with a mean follow-up of 33 weeks [15]. Several surgical groups have begun using chordal cutting to increase leaflet mobility and coaptation after ring annuloplasty, apparently reducing the need to overcompensate for persistent tethering by undersizing, which may further stress the valve. However questions were still arising from a series of studies on chordal cutting performed by Craig Miller team. Initially, Timek et al. showed that severing basal chordae in sheep without infarction (to explore potential use in supporting prolapsing segments) did not alter LV size or function [37]. More recently, the same group reported mild localized changes in regional fractional area shortening in three epicardial segments (2 apical). The largest changes were in regional PRSW, a derived value with wide scatter, for which the authors felt it necessary to discard some or all values in 7 of 8 sheep because of unphysiologic results [38]. Global systolic function, systolic and end-diastolic pressures, LV dP/dt, global elastance, and global PRSW were unchanged. In contrast, a further study suggested a decrease in global systolic function [33]. In that work, chordal cutting was preceded by the induction of transient ischemia in the papillary muscle territory [39]. Ingeniously, the chords were cut by radiofrequency ablation in the beating heart using wires looped around them to compare hemodynamics before and after cutting without changes in load. The authors reported a mild decrease in global end-systolic elastance (P = 0.04) and decreased PRSW (P = 0.03). However, there were no changes in load-dependent measures, and there were no changes in loading conditions to limit the applicability of these measures, which included LV volumes (and by implication EF and cardiac output), LV pressures, and dP/dt [33]. The Messas ’s study [32] using a similar Craig Miller’s radiofrequency approach but without ischemia has shown no acute changes in global function or regional strain measured noninvasively by Doppler or invasively by sonomicrometers. All of this experimental results and clinical experience with chordal cutting technique advocate for the absence of any short or long-term impact on segmental or global LV function.

As the leaflet tethering is applied on both annular and PM levels, the same team conducted an experimental chronic ischemic MR sheep model to study the potential benefit of associating undersized ring annuloplasty with chordal cutting. The association of both techniques improves results due to improved coaptation and reduced LV remodelling with an incremental improvement over isolated undersized annuloplasty [11] (Fig. 12.4).

Okada et al. have studied patients with global LV dysfunction and severe ischemic MR; after chordal cutting and annuloplasty, MR decreased, without decreased EF. [40] Fayad et al. reported the result of five patients with LV ejection fraction averaged 39 ± 3 % with ischemic MR, due to anterior leaflet tenting, which worsened during exercise echocardiography. All patients underwent cutting of the two basal chordae attached to the anterior mitral leaflet associated with myocardial revascularization. Three patients had additional mitral valve annuloplasty. Postoperative MR was evaluated using exercise echocardiography. Chordal cutting was performed through aortotomy allowing comfortable access to the anterior mitral valve. Mitral effective regurgitant orifice at rest and at peak exercise was reduced by surgery (10 ± 3 to 0.6 ± 0.5 mm² at rest and from 20 ± 3 to 6 ± 2 mm² at peak exercise; p = 0.03). Mitral tenting area at rest and at peak exercise was concomitantly reduced by surgery (1.83 ± 0.21 cm² to 0.50 ± 0.4 cm² at rest and from 3.11 ± 0.58 to 1.7 ± 0.5 cm² at peak exercise; p = 0.03). Left ventricular size and function remained unchanged after surgery confirming the myocardial safety of the study [41]. Yamamoto et al. have reported one patient with ischemic MR treated by chordal cutting, annuloplasty, and cardiac volume reduction; after 6 months, EF was maintained [42]. Sai-Sudhakar CB et al. describe a case of 66-year-old man with cardiomyopathy and ischemic mitral regurgitation presented with the features of congestive heart failure with severe mitral regurgitation associated with the tethering of the lateral (P1) and medial (P3) scallops of the posterior leaflet of the mitral valve due to secondary chordal attachments. The ejection fraction was only 15 % with severe global systolic and diastolic dysfunction. Mitral regurgitation was successfully corrected with mitral annuloplasty and resection of the secondary chordae tethering the medial and lateral scallops of the posterior leaflet of the mitral valve [43]. Borger et al. have shown that chordal cutting improves mitral leaflet mobility and decrease MR recurrence in patients without any adverse effects on LV function [44]. They compared echocardiographic and clinical data in patients who underwent chordal-cutting mitral valve repair (n = 43) and those undergoing conventional mitral valve repair (control, n = 49) for ischemic mitral regurgitation. Patients who underwent chordal cutting had a higher prevalence of recent myocardial infarction, left main disease, diabetes, and peripheral vascular disease (all p < .05). Left ventricular ejection fraction was lower in the chordal-cutting group (33 ± 2 % vs 44 ± 2 %) and preoperative tent height was greater (11.7 ± 0.5 vs 9.7 ± 0.6 mm; both p < .01). In-hospital mortality was 10 % in control patients and 9 % in the chordal-cutting group (P = .9). Other complication rates were similar for the two groups. The reduction in tent height before-to-after repair was similar in the two groups of patients, but those undergoing chordal cutting had a greater reductions in tent area (53 ± 3 % vs 41 ± 3 %; p < .01). The chordal-cutting group also had greater mobility of the anterior leaflet, as measured by a reduction in the distance between the free edge of the anterior mitral valve

leaflet and the posterior left ventricular wall (24 ± 3 % vs 11 ± 4 %; p < .01). Control patients had more recurrent mitral regurgitation during 2 years of follow-up by univariate (37 % vs 15 %; p = .03) and multivariate analysis (p = .03). Chordal cutting did not adversely affect postoperative left ventricular ejection fraction (10 % ± 5 % relative increase in left ventricular ejection fraction vs 11 % # 6 % in the control group; p = .9). In this study, chordal cutting improves mitral valve leaflet mobility and reduces mitral regurgitation recurrence in patients with ischemic mitral regurgitation, without any obvious deleterious effects on left ventricular function.

More recently Calafiore et al. in 2013 [45] confirm this result in case (chordal cutting; n = 26) – control (classic annuloplasty; n = 26) trial using a propensity matched approach. From 2007 to 2011, 31 patients underwent CC for ischemic MR. The indication was the presence of increased tethering of the anterior leaflet, with a bending angle (BA) <145°. Patients with same echocardiographic characteristics were identified and propensity matched for age, ejection fraction (EF), MR grade, diameters, and BA. Only patients with preoperative and follow-up echocardiograms were included and divided into two groups of 26 patients each, CC and no-CC. Preoperatively, in the CC and no-CC groups, the age was 61 ± 9 and 62 ± 10 years, EF was 31 % ± 5 % and 29 % ± 8 %, MR grade (0–4) was 3.6 ± 0.6 and 3.3 ± 0.8, and diastolic and systolic dimension was 56 ± 7 and 43 ± 8 mm and 57 ± 11 and 44 ± 11 mm, respectively. The New York Heart Association class and BA was 2.7 ± 0.6 and 2.6 ± 0.7 and 137° ± 4° and 137° ± 6°, respectively. All patients underwent overreductive annuloplastie (physioring for no CC and SMB40 for CC group). In the CC group, second-order chords were cut using aortotomy. After a mean of 33 ± 15 months, the MR grade was 0.6 ± 0.6 and 1.1 ± 0.8 (P = .014) and the EF was 40 % ± 5 % and 35 % ± 7 % (P = .005) in the CC and no-CC groups, respectively. The corresponding diastolic and systolic diameters were 52 ± 5 and 38 ± 8 mm and 53 ± 11 and 41 ± 12 mm (P = NS). The modifications were significant only in the CC group (P = .022 and P = .029 for the diastolic and systolic dimensions, respectively). The corresponding New York Heart Association class decreased to 1.1 ± 0.3 and 1.5 ± 0.6 (P = .004). The BA increased to 182° ± 4° in the CC (P < .001) and remained unchanged (137° ± 6°) in the no-CC group. The authors concluded that in selected patients with a BA <145° and coaptation depth ≤10 mm, CC is related to less MR return or persistence, improved EF, and lower New York Heart Association class. Therefore, in selected patient with a BA < 145° and coaptation depth ≤ 10 mm, chordal cutting is related to less MR return or persistence, improved EF and lower NYHA Class.