Results
On TTE the mean value of anterior and posterior mitral leaflet angle was 25.41 ± 4.28 and 38.37 ± 8.89°. By CMR the mean values of anterior and posterior mitral leaflet angle were 25.74 ± 3.09 and 38.94 ± 6.32 degree, respectively.
Five patients (11.9%) had posterior mitral leaflet angle exceeding 45°.
There was a strong correlation between echocardiography and CMR for assessing AML (r = 0.77; P = 0.001 and PML (r = 0.83; P = 0.001).
The IMR severity parameters were as follows: ERO 0.16 ± 0.12 cm2, RV 26.37 ± 14.59 ml, RF 0.38 ± 0.24, VCW 0.61 ± 0.80 cm.Mitral deformation indices including coaptation height (CH) and tenting area (TA) were 1.49 ± 0.41 cm and 3.95 ± 1.64 cm2.
By CMR, the RV was 20.01 ± 13.48 ml and RF 0.23 ± 0.12. There was a significant correlation between TTE and CMR for assessing RV (r = 0.688, P = 0.001) and RF (r = 0.539, P = 0.001) and also for CH (r = 0.606, P < 0.001) and TA (r = 0.676, P < 0.001).
Mean values of CMR data are presented in Table
2.
Table 2
The CMR parameters expressed as mean ± SD, minimum and maximum values
Coaptation height (cm) | 1.37 ± 0.46 | 0.74 | 2.76 |
Tenting area (cm2) | 3.39 ± 1.38 | 1.45 | 6.03 |
Mitral annular area syst. (cm2) | 10.70 ± 2.94 | 5.69 | 17.98 |
Mitral annular area diast. (cm2) | 12.28 ± 2.90 | 7.45 | 19.66 |
MADs ant-post (cm) | 3.14 ± 0.59 | 1.8 | 4.24 |
MADs sept-lat (cm) | 3.49 ± 0.54 | 2.5 | 4.58 |
MADs ant-inf (cm) | 3.85 ± 0.55 | 2.9 | 5 |
MADs mean (cm) | 3.49 ± 0.50 | 2.4 | 4.41 |
MADd ant-post (cm) | 3.53 ± 0.61 | 2.2 | 4.6 |
MADd sept-lat (cm) | 3.76 ± 0.49 | 2.75 | 4.91 |
MADd ant-inf (cm) | 4.11 ± 0.52 | 3.2 | 5.1 |
MADd mean (cm) | 3.80 ± 0.48 | 2.87 | 4.77 |
Sphericity index (SI) | 0.56 ± 0.09 | 0.38 | 0.77 |
RV (ml) | 20.01 ± 13.48 | 0.93 | 63.24 |
RF | 0.23 ± 0.12 | 0.01 | 0.6 |
LVEDDI | 3.51 ± 0.57 | 2.32 | 5.2 |
LVESDI | 4.53 ± 9.43 | 1.61 | 57.73 |
LVEDVI | 138.76 ± 50.96 | 65.68 | 304.34 |
LVESVI | 91.91 ± 48.96 | 21.46 | 243.71 |
SVI | 46.80 ± 9.19 | 33.09 | 65.82 |
SV (ml) | 85.76 ± 18.70 | 53 | 129 |
EF | 36.54 ± 13.46 | 19 | 67.3 |
LAV (ml) | 73.61 ± 34.22 | 27.86 | 192.25 |
WMSI tot | 2.11 ± 0.50 | 1.12 | 2.88 |
For all studied subjects (RV > 20 ml), there was a good correlation between anterior mitral leaflet angle and RV (
r = 0.74,
P = 0.01). This correlation was stronger (
r = 0.97,
P = 0.005) in patients with a more severe MR (RV > 30 ml). In addition, in this group of patients, there was a significant correlation between the RV and posterior mitral leaflet angle (
r = 0.90,
P = 0.037), between tenting area and posterior mitral leaflet angle (
r = 0.90,
P = 0.04), between tenting area and anterior mitral leaflet angle (
r = 0.82,
P = 0.08). There was also a weak but significant correlation between PML angle and MADs ant-post (mitral annulus diameter (antero-posterior) in systole (
r = 0.34,
P = 0.039) (Table
3). Besides, there was a correlation between PML angle and LAV (
r = 0.41,
P = 0.012).
Table 3
The correlation between anterior and posterior mitral leaflet angle values and indices of LV remodeling, mitral apparatus deformation and IMR severity
AML angle/Regurgitant volume (RV > 20 ml) | 0.01 | 0.74 |
AML angle/Regurgitant volume (RV > 30 ml) | 0.005 | 0.97 |
PML angle/Regurgitant volume (RV > 30 ml) | 0.037 | 0.90 |
PML angle/Tenting area (RV > 30 ml) | 0.04 | 0.90 |
AML angle/Tenting area (RV > 30 ml) | 0.08 | 0.82 |
PML angle/MADs ant-post | 0.039 | 0.34 |
PML angle/LVEDVI | 0.031 | 0.35 |
PML angle/LVESVI | 0.021 | 0.37 |
PML angle/SV | 0.03 | 0.35 |
AML angle/WMSI tot | 0.019 | 0.41 |
PML angle/SI | 0.041 | 0.33 |
PML angle/LAV | 0.012 | 0.41 |
Among the parameters of LV remodeling, there was a significant correlation, for all the group of patients, between posterior mitral leaflet angle and LVEDV index (r = 0.35, P = 0.031), LVESV index (r = 0.37, P = 0.021), SV (r = 0.35, P = 0.03), SI (r = 0.33, P = 0.041). AML angle correlated only with WMSI (r = 0.41, P = 0.019).
Inter-observer and intra-observer variability tested by the Cohen’s method showed a concordance of 94 and 95% for echocardiographic and 95 and 96% for CMR parameters.
We have found that, in patients with chronic ischaemic mitral regurgitation (IMR), the value of anterior and posterior mitral leaflet angle determined by echocardiography correlates with the parameters of mitral apparatus deformation and LV remodeling indices by TTE and CMR. We found that echocardiographic measurement of tenting area, coaptation height and the mitral leaflet angles are highly concordant with the CMR measurements. This is important as echocardiography remains the primary diagnostic tool in patients with IMR and the therapeutic decisions (including referral for surgery and the choice between repair vs. replacement) are usually made on the basis of a thourough echocardiogram while IMR remains a diagnostic and therapeutic challenge.
In particular, it is still not clear what patients and when (i.e., at what stage of IMR and on the basis of what particular parameters) should be referred for surgery [
11]. In the past, the decision was based on parameters such as the mitral regurgitant jet extent (colour Doppler), the colour flow jet area, jet length and width, the ratio of the jet area to the left atrial area, the intensity of the continuous wave Doppler signal, the pulmonary venous flow contour or the peak early mitral inflow velocity. Those parameters, however, have been shown to be insufficient in assessing the severity of IMR in the context of the need for surgery. More recently, the quantitative IMR assessment (effective regurgitant orifice, ERO, regurgitant volume, RV, and the vena contracta width, VCW) has been indicated as the method of choice for grading the severity of IMR [
12‐
14]. Indeed, PISA and VCW show a much better correlation with angiographic grading of MR than the semi-quantitative methods [
14‐
16]. An effective regurgitant orifice >0.2 cm
2 and regurgitant volume >30 ml are associated with a poor long-term prognosis and thus those values indicate a severe IMR [
17,
18].
There is a great interest in identifying new parameters of IMR severity. Kwan and colleagues [
19] indicated the posterior leaflet angle of >47
o as the cut-off value discriminating between significant (≥moderate) and non-significant IMR (sensitivity of 96% and specificity of 84%). Magne and co-workers [
3] suggested that posterior leaflet angle ≥45° was related to a poor 3-years outcome in patients after mitral valve repair due to IMR. However, not only severe but also mild IMR is associated with an adverse prognosis due to the an additional hemodynamic load on the post-infarcted ventricle [
20].
The indications for mitral valve surgery in chronic IMR are not well defined. In most cases, in patients with severe IMR coronary bypass grafting alone is not sufficient to cure or even to reduce its degree [
21]. It is generally agreed that patients who have indications for coronary artery bypass grafting (CABG) with moderate-to-severe IMR (3 or 4 grade) should also undergo concomitant MV surgery [
22‐
24]. However, it is controversial whether concomitant MV surgery should be performed in CABG patients with mild-to-moderate IMR (1 or 2 grade) [
22]. Malidi and co-workers [
25] compared, in patients treated by isolated CABG, the outcome between those with mild-to-moderate IMR versus those without IMR. They found a higher prevalence of heart failure symptoms and decreased cardiac event–free survival in IMR patients. In addition, 30% of patients progressed to 3 or 4 grade MR during a mean follow-up of 16 months. Those findings would suggest that MV surgery should be considered at the time of CABG even in patients with mild-to-moderate IMR, but the parameters on which the decision should be made remain to be defined—particularly since in moderate IMR the clinical utility of mitral valve repair remains unproven [
11,
26,
27]. In particular, the risk of long-term MR and heart failure progression must be balanced against the increased perioperative risk of the additional MV procedure [
25]. Borg and coworkers [
22] recommend that patients with mild-to-moderate IMR and multiple comorbidities, or a life expectancy of less than 5 years, should undergo CABG only.
The most common surgical procedure currently performed for chronic IMR is restrictive mitral annuloplasty [
28,
29]. However, mitral valve replacement remains a reasonable surgical option in subgroups of patients with IMR, predominantly because of its reliability and reproducibility. Mitral valve replacement should be considered for patients with chronic IMR and multiple comorbidities, complex regurgitant jets (non-central jet or several jets), or severe tethering of both MV leaflets [
29,
30]. Calafiore and coworkers [
29] recommend MV replacement when the distance between the coaptation point of the leaflets and the plane of the mitral annulus (coaptation height) exceeds 1.0 cm.
Recurrent IMR despite surgical annuloplasty is related to leaflet tethering by progressive left ventricular remodeling [
30‐
33]. Among the pre-operative echocardiographic parameters, obtained by transthoracic approach, the most important in predicting persistent or recurrent MR after annuloplasty are tenting area 2.5 cm
2, coaptation height 1.0 cm, central jet of MR, complex regurgitant jets, restrictive diastolic filling profile, severe enlargement of the left ventricle and posterior mitral leaflet angle value ≥45° [
21,
34]. In a study of 51 patients subjected to mitral valve repair, those with posterior mitral leaflet angle value ≥45° had significantly lower 3-year event-free survival (22 ± 17% vs. 76 ± 12%,
P < 0.001) [
3].
We showed that the posterior mitral leaflet angle value highly correlated with regurgitant volume and tenting area (
r = 0.90,
r = 0.90, respectively). However, our findings also suggest that it may be important to evaluate the anterior mitral leaflet angle, especially in the group of patients with a more severe MR (RV > 30 ml). In those patients, we found a strong correlation between the anterior mitral leaflet angle and regurgitant volume or tenting area (
r = 0.97,
r = 0.82 respectively). Thus our current findings and those of Magne and colleagues [
3] indicate that the consideration of the anterior leaflet angle in combination with the other indices of mitral valve morphology may be useful to guide the operative strategy. In our study group, the five patients (11.9%) with the posterior mitral leaflet angle value >45° were referred to mitral valve replacement with chordal sparing.
Limitations
The present study was based on 2D echocardiography while 3D echo can provide more precise geometric information on the mitral apparatus deformation and left ventricular remodeling. However, in a majority of cardiovascular centers today, the 2D echo remains the most common imaging modality in patients with IMR. Importantly, our measurements of mitral leaflet angles by 2D echo were correlated not only with the echocardiographic but also CMR parameters of mitral apparatus deformation and LV remodeling.
In our study, the assessment of IMR was done at rest. Recent work by Lancellotti and colleagues [
35] shows that chronic IMR is dynamic during exercise, and that an increase in ERO ≥ 13 mm
2 on exercise can identify the subgroup of patients at a higher risk of cardiac events. Thus it is likely that evaluation of IMR on exercise will need to be considered in the decision-making algorithms in patients with chronic IMR.