Fig. 21.1
Pre-operative Surgical decision making in secondary mitral valve regurgitation. AML anterior mitral leaflet, MV mitral valve
Fig. 21.2
Actuarial survival and improved by at least one New York Heart Association Functional Class in survivors of mitral valve surgery for dilated cardiomyopathy (Reprinted with permission from Calafiore et al. [8])
Fig. 21.3
Actuarial survival of restrictive mitral annuloplasty for ischemic mitral regurgitation based on preoperative left ventricular end diastolic dimensions (LVEDD) (Reprinted with permission from Braun et al. [10])
In patients with moderate degrees of secondary mitral regurgitation concomitant with other cardiac procedures such as coronary artery bypass graft surgery and aortic valve surgery, there is now a tendency for surgeons to be more aggressive in treating less than severe mitral regurgitation [11–13]. Atrial fibrillation as well as prosthesis-patient mismatch has been identified as a risk factor for the persistence of moderate or more mitral regurgitation in patients undergoing aortic valve replacement with concomitant moderate mitral regurgitation [5, 14]. The low 4 % incidence of recurrent moderate or more mitral regurgitation in the RIME trial confirmed the long term stability of a restrictive mitral ring annuloplasty in patients having moderate rather than severe mitral regurgitation at preoperative baseline [13].
A mitral annuloplasty with no additional adjunctive techniques is likely to be successful in terms of a low operative risk and low incidence of recurrence of moderate or more mitral regurgitation, especially if originally done on the basis of preoperative echo guided predictive risk factors and / or for less than severe, moderate secondary mitral regurgitation [5].
Patients having had surgery for secondary mitral regurgitation due to LV dilatation can therefore be classified as those having a low or high risk of recurrent mitral regurgitation (Table 21.1). The latter group should be followed up more intensely in terms of optimizing medical treatment directed at improving LV function, or rarely re-intervention.
Table 21.1
Low risk of recurrent mitral regurgitation
Indication for mitral valve repair |
Secondary mitral regurgitation for Lone AF |
Concomitant ‘moderate’ secondary mitral regurgitation in patients undergoing cardiac surgery, for aortic valve or ischemic heart disease |
Preoperative degree of Type IIb leaflet restriction |
Coaptation depth ≤10 mm |
Tenting area <2.5 cm |
No severe anterior mitral leaflet tenting |
Anterior mitral leaflet angle (tip) <25° |
Preoperative LV function |
LVEDD <65 mm |
LVESD <51 mm |
Systolic sphericity index <0.7 |
It is now well known that a mitral annuloplasty increases posterior leaflet tethering and is dependant for success on a mobile anterior mitral leaflet, hence the importance of assessing the degree of anterior mitral leaflet tethering in determining long term stability of a repair [15]. The type of annuloplasty band or ring used, as well as surgical experience may also influence longer term stability of the mitral valve repair [16].
Antithrombotic Management
Oral anticoagulation with warfarin/Coumadin should be considered for the first 3 months after mitral valve repair surgery (recommendation Class IIa Level C) [1]. The risk of thrombo-embolism in these patients may be related to both the implantation of an annuloplasty band or ring into the left atrium, the high rate of atrial fibrillation associated with mitral valve disease, as well as possible impaired LV function (ejection fraction <35 %).
The thrombo-embolic risk of the implanted annuloplasty band or ring itself is not clearly defined and is probably low. A meta-analysis of mitral valve repair patients confirmed that the highest risk of thrombo-embolism occuring is in the early months following surgery, as well as a high 36 % post discharge incidence of atrial fibrillation in patients discharged in normal sinus rhythm [17]. Concomitant left atrial amputation may not reduce thrombo-embolic risks such that warfarin anticoagulation can be omitted in mitral valve repair patients [18]. The known frequent incidence of asymptomatic episodes of AF further highlights the importance therefore of both early anticoagulation as well as continued monitoring of heart rhythm in mitral valve repair patients. This is highlighted by the study showing that coronary artery bypass graft surgery patients with no previous history of atrial fibrillation, who then have a temporary episode of postoperative atrial fibrillation, have an eightfold increased risk of developing future atrial fibrillation and an increased cardiovascular late mortality usually from cerebral ischemic events [19].
The recommended target INR is 2.5 for patients (low risk valve prosthesis) without patient related risk factors, or 3.0 for those with risk factors such as atrial fibrillation, large left atrium greater than 50 mm or poor LV ejection fraction (<35 %) [20]. However, these ‘patient risk factors’ were identified and described for patients with prosthetic heart valves [21]. Furthermore, significant number of surgeons perceive the thrombo-embolic risk following mitral valve repair surgery (probably predominantly of a primary degenerative and not secondary aetiology) to be very low and do not prescribe warfarin anticoagulation [22, 23], whether with (36 %) or without (65 %) an annuloplasty ring [23]. The European Society of Cardiology and British Committee for Standards in Haematology only recommend a single target INR of 2.5 for patients with AF who require warfarin for the prevention of cardio-embolism and do not describe higher thrombo-embolic risk groups [24, 25]. Therefore it would seem reasonable to recommend a single target INR of 2.5 for at least the first 3 months following a mitral valve repair.
Patients with mitral valve disease have a high incidence of atrial fibrillation, and today many have had concomitant ablation surgery for preoperative AF. The current recommendation in post AF ablation patients in normal sinus rhythm is to stop anticoagulation after 3 months, but only after considering the stroke-risk profile and risk of atrial fibrillation recurrence in each individual patient [26].
Assessment and Follow up of the Repaired Mitral Valve
Transesophageal echocardiography (TEE) allows the evaluation of the mitral valve repair at the time of surgery. Transthoracic echocardiography (TTE) is though the key imaging method for both postoperative and follow up assessment of mitral valve repair (Table 21.2).
Table 21.2
Echocardiography parameters to be assessed in the follow up of secondary mitral valve repair
The mitral valve | Multi-parametric quantification of mitral regurgitation |
Transmitral gradients | |
Anterior leaflet tethering | |
The left ventricle | Left ventricular diameter, volume and function (M-mode, 2D, 3D echo, speckle tracking strain analysis) |
The left atrium | Left atrial volume |
The pulmonary circulation | Transtricuspid pressure gradient and systolic pulmonary artery pressure |
The tricuspid valve | Quantification of tricuspid regurgitation |
The right ventricle | Right ventricular diameter, volume and function (TAPSE, TDI, RV end systolic area) |
In principle, at the time of surgery the objective should have been to not accept more than mild residual mitral regurgitation (Grade I) on the post repair intraoperative TEE. Patients with postoperative persistent moderate or more mitral regurgitation have a poor survival [5].
The likelihood of subsequent deterioration of mitral valve repair is more frequent in patients with secondary mitral regurgitation than in those with degenerative mitral regurgitation [27]. The quality of the immediate results (residual regurgitation or stenosis) in the setting of secondary mitral regurgitation is a predictor of deterioration of valve repair, but recurrence of mitral regurgitation may occur despite a good immediate result.
The post repair TEE should not be used as the ‘baseline’ echocardiogram. Recurrence of moderate or more mitral regurgitation following initially successful surgery, especially in the higher risk groups of patients (Table 21.1), generally occurs within the first 6–12 post-operative months (Fig. 21.4) [16]. Event-free survival is decreased in patients with recurrent significant mitral regurgitation, highlighting the importance of close follow-up in this group of patients [28].
Fig. 21.4
Average temporal prevalence, with 68 % confidence limits, of progression of mitral regurgitation after mitral annuloplasty for ischemic mitral regurgitation to grades 3+ or 4+ (Reprinted with permission of McGee et al. [16])
Clinical Practice
All patients should have a baseline clinical examination, chest X-ray, ECG, and TTE assessment 6–12 weeks following surgery. Thereafter, it seems reasonable to perform further clinical and echocardiogram assessments again at 6 and 12 months following surgery, especially in patients at higher risk for recurrent mitral regurgitation (Table 21.1), although currently there is no specific recommendation regarding the follow up of patients after mitral valve surgery for secondary mitral regurgitation. Given that these frail patients primarily have heart failure with LV systolic dysfunction, echocardiography follow up should be routinely performed at each visit because echocardiography-based management improves the outcome of heart failure with reduced LV ejection fraction [29].
Mitral Gradients
Transvalvular mitral gradients should be routinely measured after restrictive annuloplasty to identify possible functional mitral stenosis, which is though rare in our experience. A significant correlation between resting peak mitral gradient and postoperative systolic pulmonary artery pressure, as well as 6-min walk test distance has been reported [30].
Residual Mitral Regurgitation
Echocardiography quantification of residual mitral regurgitation may be challenging, as the surgically altered mitral valve and sub-valvar apparatus can result in an inaccurate assessment of the proximal flow convergence zone. Therefore, the quantification of mitral regurgitation should rely on a multiparametric approach as recommended by current European guidelines, to ensure the consistency between the different echocardiography measurements [20]. Transesophageal echocardiography (2D and 3D) may be useful in some patients when there is doubt regarding the severity or the mechanism of recurrent mitral regurgitation by TTE.
Global LV remodelling may also be responsible for recurrence of secondary mitral regurgitation. However, it is not the sole mechanism responsible for recurrent mitral regurgitation. In the absence of LV dilation, recurrent mitral regurgitation may be explained by localized LV remodelling in the vicinity of papillary muscles resulting in increased anterior leaflet tethering at the bending point [31].
LV Remodelling
The aim of mitral valve repair in the context of secondary mitral regurgitation is to not only reduce the amount of mitral regurgitation but to also limit further adverse LV remodelling, to improve LV function and thereby improving patient’s symptoms. LV geometry frequently changes significantly after cardiac surgery and advantageous reverse remodelling has been well documented following successful mitral valve repair, in both low ‘simple’ annuloplasty as well as high risk patients requiring additional techniques [32, 33].
The reference technique for quantifying LV volumes is cardiac magnetic resonance imaging (MRI), as it does not rely on geometric assumptions. In the recent RIME study, LV reverse remodelling was observed in patients with ischemic heart disease and moderate secondary mitral regurgitation who underwent concomitant coronary artery bypass graft surgery (CABG) as well as mitral valve repair, illustrated by a 28 % decrease in LV end systolic volume index assessed by MRI compared to only a 6 % decrease in those who underwent CABG without associated mitral valve repair [13]. Nevertheless, in routine clinical practice, bidimensional echocardiography is widely used to detect serial changes in LV volumes and function following mitral valve repair. Three-dimensional echocardiography, in patients in sinus rhythm with adequate acoustic windows, further increases the accuracy of LV volume quantification [34], and can provide an accurate assessment of LV remodelling following mitral valve repair and LV reconstruction [35]. New algorithms and smaller 3D- transthoracic probes are now more user-friendly and can be used in clinical practice [36].
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