Discussion
Although some mild forms of MR can be present in healthy individuals,
severe forms can result in serious problems (13). MR in a moderate to
severe form is the most frequent valvular disease in the USA (1) and the
second most surgery-required valvular complication in Europe (14).
MR can occur due to various causes and mechanisms. The etiologies are
classified either as ischemic -a consequence of coronary disease- or
otherwise non-ischemic. Mechanisms are divided into two groups: organic
(primary) with an intrinsic valvular lesion which contains degenerative
mitral valve disease as the most frequent mechanism of MR (60–70%) and
functional (secondary) with a structurally normal but deformed mitral
valve as a result of left ventricular remodeling (13). The primary
mechanism is subclassified based on the leaflet movement, as a normal
movement represents class I, and excessive or restricted movement is
classified as class II and III, respectively (15).
After suspicion is raised about the MR through clinical presentations
and physical examinations like a displaced apical impulse, systolic
murmur, third heart sound, early diastolic rumble, and atrial
fibrillation, clinical and paraclinical studies to investigate the MR
should be pursued. Signs and symptoms of heart failure (HF) and severe
MR should be looked for in the clinical assessment, although they are
not specific to MR (16). TTE is usually the first paraclinical modality
to assess regurgitation. Gathering data on causes, mechanisms, severity,
and the impact of regurgitation must be followed (8, 13).
Chronic volume overload of the left ventricle can happen as a
consequence of a neglected MR. this can lead to increased left atrial
pressure, increased pulmonary venous pressure, pulmonary edema, and
subsequently, right-sided HF. Severe MR is associated with a 5-year
mortality of 50%. Facing outcomes of the MR, like HF, will be
inevitable for the survivors, as it happens for approximately 90% of
them (17). MR independently increases the burden of other cardiac
conditions, as it increases the mortality in patients with severe
systolic HF (18).
According to the management guidelines, surgery is introduced as the
only definite treatment (19). The severity of the MR increases the
necessity of the surgery, even in the presence of advanced HF or
ventricular dysfunction (20). This shows the importance of precise
quantification of the severity. Paraclinical imaging methods, along with
criteria, are developing to achieve an optimal introduction of patients
to surgery (8). Other factors, like the cause and mechanism of the MR,
affect the decision for surgical correction as well (15).
Different features should be gathered through echocardiography to
determine the regurgitation severity, which can be divided into four
groups. To begin with, the structure of the valve, leaflets, and
mechanical findings should be described. It can range from normal
leaflets to severely damaged valves with lesions like large perforations
or flail leaflets. The size of the left atrium and ventricle should also
be measured. Secondly, a qualitative Doppler assessment of color flow
jet area, flow convergence, and Continuous Wave Doppler (CWD) jet is
required.
Further, semi-quantitative data like VCW, pulmonary vein flow, and
mitral inflow must be gathered. Last but not least, quantitative
measures are reported to clarify MR severity. These factors include the
EROA, a basic measure representing the regurgitation severity, and RVol,
which can help estimate the overload burden and the RF. Values of EROA
and RVol are the strongest predictors of the outcome. While data from
these four groups should be assessed together, some features can
individually specify the lesion severity (8).
Three methods are available to calculate the quantitative measures of MR
severity: The flow convergence method (PISA method), the Quantitative
volumetric method, and the Quantitative pulsed Doppler method. All these
methods have some common components (Rvol, RF, and EROA). RVol is
determined as the blood volume which regurgitates in one beat. RF is
defined as RVol divided by the stroke volume through the regurgitant
valve, and the EROA is calculated as the RVol divided by the VTI of the
regurgitation jet. These quantitative methods have some complexities. An
expert operator is required to assess the primary measures. Because, for
example, in some methods assessing the mitral annulus diameter is
required, which is hard to obtain, or unless an exact radius value is
prepared in the PISA method, the EROA would be largely miscalculated
(8).
In cases where TTE reports suboptimal results, TEE can be helpful (8).
In TEE, the proximity of the probe to the mitral valve with a higher
spatial resolution can help to recognize the MR severity more accurately
(3). It also can give a better perspective on the exact location of the
deficit, which can facilitate further interventions and surgeries (9,
18). TEE is useful when more exact quantification of the measures is
required, for instance, jet color characteristics like VCW, VCA, and
PISA radius. TEE can also more accurately evaluate the pulmonary veins
and potential reverse flow (18). However, TEE is a semi-invasive method
that relies on geometric assumptions and is not generally available,
making TTE the suitable method for preliminary and serial studies of MR
(9). TEE demonstrates the color jets larger than TTE, and as it is done
under sedation, because of the altered hemodynamic status and
particularly decreased blood pressure, the MR severity might be
underestimated (18).
Accurate evaluation and quantification of MR severity are crucial to
assessing the valve status to decide on required interventions. This led
to the introduction of new instruments and modalities. Three-dimensional
(3D) techniques have improved the measurements, for instance, on Rvol
and the ventricle diameters (21, 22). Also, new methods like multi-slice
CT scan and CMR are introduced, which improve the assessments, and are
growingly used to substitute the previous echocardiographic suboptimal
results or as alternatives (9, 23).
In the current study, the MR severity of 93 patients was determined
using conventional semi-quantitative (VCW) and quantitative (RVOl, RF,
EROA) measures. Due to technical difficulties in obtaining these
quantitative measures, along with the non-feasibility of TEE as a
routine option for further investigations (as a result of limited
availability, aggressiveness, and dependence on sedation), we made an
effort to identify new parameters which are easier to obtain by TTE and
do not rely on operators’ expertise. This study introduces new
hemodynamic burden indices (MVVTI/LVOTVTI; MVAVTI-i; MVAVTI/LVOTDVTI; E
velocity-LA area-i) for this purpose and examines their correlation and
diagnostic value to express the severity of the MR. These indices show
an excellent diagnostic value in recognizing patients with severe MR.
While there are uncertainties about the effect of normalization of the
conventional measures on BSA on its diagnostic value (8), we used two
indices (MVAVTI-i; MVAVTI/LVOTDVTI) which BSA is contained in them.
To our notice, this is the first time that these indices have been used
in this manner. Consequently, similar data was not available for further
comparison of the results. Similar studies with larger sample sizes
should be conducted to further validate these indices and introduce them
to the diagnostic criteria.