Cardiac Remodeling after Surgical Mitral Valvuloplasty for Barlow's Disease: Is it the Time to Look to the Load?

We present the case of a 48-year-old man referred for a reduced exercise tolerance in whom a bileaflet mitral prolapse (Barlow's disease), associated with flail motion of posterior mitral leaflet and ruptured chordae tendineae and complicated by eccentric severe regurgitation, was incidentally diagnosed. Albeit paucisymptomatic, at echocardiography he showed the signs of LV dysfunction and, accordingly, was underwent surgical mitral valvuloplasty with implantation of the Memo 3D ReChord Ring without complications. We analyzed the changes of echocardiographic parameters of cardiac remodeling from baseline to post operative setting, highlighting the utility of modern imaging tools (strain and myocardial work) in grade to gauge with more sensitivity LV deformation and function in different conditions of pre and afterload and to overcome the limits of ancient ejection fraction. In conclusion, especially LV myocardial work may be a promising and accurate non load dipendent tool to quantify subclinical LV dysfunction, to guide therapeutic decisions and in post-surgical follow up. Copyright:

INTRODUCTION

Severe mitral regurgitation (MR) is associated with high morbidity and mortality if surgical treatment is not timely performed. A great challenge is to identify potential left ventricular (LV) dysfunction at an early stage in order to optimize the surgery timing. However, LV ejection fraction (EF) and/or LV end-systolic diameter, parameters of LV dysfunction proposed by current guidelines as indicators for intervention, are often misleading and difficult to interpret because of their load dependency.

CASE REPORT

We report a case of a 48-year-old man referred for a reduced exercise tolerance for several months. He had no cardiovascular risk factors, except smoking, and a clinical history of an episode of amaurosis fugax 5 years before. Physical examination, blood pressure (BP), heart rate and electrocardiogram were normal. Unexpectedly, both transthoracic (transesophageal echocardiography [TTE]) and TTE showed bileaflet mitral prolapse (Barlow's disease) associated with flail motion of the central scallop of posterior mitral leaflet (P2) and first-order chordae tendineae rupture to the posterior leaflet (Type II-Carpentier classification) with eccentric severe regurgitation (4+/4+; regurgitant volume = 69 mL, effective regurgitant orifice area-EROA = 0.42 cm2) [Figure 1, Panel A]. LV EF was normal, whereas LV end diastolic volume index (EDV/body surface area = 86 mL/m2), LV ESD (42 mm), and left atrium (LA) volume index (42 mL/m2) were increased. Global longitudinal strain (GLS) average was also in normal range (−22%) whereas global myocardial work index (GWI) and efficiency (GWE) were both reduced (1465 mmHg% and 72%, respectively). The reduction of the above-mentioned myocardial work (MW) components was particularly pronounced at the level of inferoseptal, inferior and posterior LV segments [Figure 1, Panel B]. Surgical mitral valvuloplasty with implantation of the Memo three-dimensional ReChord Ring was successfully performed without complications [Figure 1, Panel C].

Figure 1

At the top (Panel A), transesophageal echocardiographic views (three chamber view at 124°, four chamber view at 0°, three dimensional “en face” view of mitral valve) showing, in late systole, bileaflet mitral prolapse associated with flail motion of the central scallop of posterior mitral leaflet by chordal rupture and medially and anteriorly directed eccentric severe regurgitation. Mitral leaflets appear large, the chordae elongated and mitral annulus dilated with loss of the coaptation point. In Panel C intraoperative transesophageal echocardiographic views (bi-dimensional view, color view and three-dimensional “en face” view) reporting mitral valve annuloplasty with implantation of the Memo three-dimensional ReChord Ring and the good surgical result suggested by early improvement of mitral regurgitation (1+/4+). In Panel B and D, comparison between preoperative (Panel B) and postoperative (Panel D) speckle-tracking echocardiographic analysis in term of Global Longitudinal Strain, Global Myocardial Work Index and Global Myocardial Work Efficiency of the left ventricular (from left to right). Note the changes of global and segmental findings in bull's eye plots, suggesting a significant left ventricular remodeling after mitral annuloplasty

At 6 months' follow-up, the patient was completely asymptomatic and no heart failure sign was detected on clinical examination. At TTE, MR resulted mild (1+/4+), LV EF was 50%, LV volumes and LA volume index were reduced but a residual paradoxical septal motion and right ventricular (RV) dysfunction (tricuspid annular plane systolic excursion = 14 mm and peak systolic velocity = 8 cm/s) were reported. GLS was also reduced (−13.4%) with a regional impairment involving especially septal basal segments, GWI (1318 mmHg%) was lower in comparison with presurgery values, despite its improvement in medium-basal inferoposterior LV segments, whereas GWE was significantly greater (90%) [Figure 1, Panel D].

DISCUSSION

This case demonstrates that surgical repair in Barlow's disease and severe MR improves the symptoms, promotes cardiac remodeling and has an effect on myocardial deformation and LV MW.

It is known that MR affects LV with a volume load leading initially to LV compensatory adaptations. Only when these adaptations fail, overt LV dysfunction occurs. The progression of chronic MR may be silent and only incidentally diagnosed, as in our case, by the development of symptoms in the advanced disease stages.

Mathematical models support the statement that LV afterload ranges from normal to increase in chronic MR[1] and progressively, contributes to EF decline and clinically overt LV dysfunction.

Accordingly, it is crucial a quantitative estimation of MR degree and of indices of LV dysfunction with advanced echocardiographic techniques during different MR stages, also in consideration of preload and afterload changes, in order to guide management decisions.

The current guidelines[2] recommend surgery in symptomatic patients with severe MR or in asymptomatic patients who show signs of LV dysfunction,[3] usually classified by EF and/or left ventricular end-systolic diameter (LVESD).

Unfortunately, these ancient echocardiographic parameters are influenced by altered loading of MR[4] and despite are simple and easily calculated, neglect the progress of modern imaging tools in grade to gauge with more sensitivity LV function and deformation in different conditions of pre and afterload.

With increasing role of advanced imaging modalities, other parameters of LV function such as GLS, GWI, and GWE may provide incremental diagnostic and prognostic information and be more clinically valid and reliable than traditional parameters.

Recent reports support the use of GLS for its better reproducibility than EF. Kim et al.[5] demonstrated that preoperative GLS appeared to be the most powerful predictor of cardiac events and all-cause death, in comparison to conventional parameters, in patients with severe primary MR who underwent surgical correction. In our case, although baseline LV GLS average was normal, GWI and GWE were impaired at BP values of 110/70 mmHg.

However, the main pitfall of GLS is the load dependence [6] that makes its reliability in the volume overloaded state of severe MR problematic.[7] Thus, LV MW, overcoming the limit of the ventricular load, may be a promising and suitable tool to detect and quantify faithfully subtle myocardial dysfunction in patients with severe MR undergoing surgery.

Furthermore, our case highlights many aspects of cardiac remodeling induced by mitral valve (MV) repair, such as the improvement of valvular geometry and filling pressures associated with a significant reduction of LA and LV volumes as result of loading condition changes. In addition, in our patient a reduction in LV EF after surgery was found. However, this EF reduction has been already described in many studies that evaluated patients underwent MV surgery, suggesting that afterload-dependent LV end systolic volume decreased relatively less than preload-dependent LV EDV.[8] Moreover, paradoxical septal motion and RV postsurgical dysfunction were found at follow up, albeit these findings are commonly recognized after cardiac surgery.[910] Even if underlying mechanisms are still not clear.

This is the first case in which the findings of strain imaging and MW after valvuloplasty for Barlow's disease were compared to baseline values. Especially MW components were able to provide valuable information for the detection of segmental hidden myocardial damage and for the pre and postoperative evaluation of severe MR.

In conclusion, surgical mitral valvuloplasty for severe MR associated with Barlow's disease improves the symptoms and promotes cardiac remodeling. In severe primary MR, LV MW may be a promising and accurate non load dependent tool to quantify subclinical LV dysfunction, to stratify the risk, to guide therapeutic decisions and in postsurgical follow-up.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.