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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 32, No 3, May/June 2021
154
AFRICA
disability, often in advanced heart failure, which impacted on
postoperative outcomes and contributed to significant morbidity
and/or mortality. Wisenbaugh
et al
. have documented that
patients in developing countries may present for the first time
when EF is < 60% or ESD > 45 mm.
25
These patients tend to
suffer poorer outcomes following MVR and would likely benefit
from mitral valve repair, even though repair undertaken in RHD
is technically more difficult than with degenerative MR.
4
A more worrying explanation for delayed surgery is that
clinicians may not be applying established guidelines in referring
patients more timeously for surgery. Patients with moderate-
to-severe MR are assessed by more junior staff who may
not request an echocardiographic assessment because of the
demands of a busy clinic, and because such patients are
relatively asymptomatic, they may be given repeated follow-up
appointments in the assumption that all is well in stable patients.
Symptoms often occur late in the course of MR since the
compliance properties of the LA allow it to accommodate
large volumes of blood before a significant rise in pressure
is transferred to the pulmonary circulation. With increasing
severity of regurgitation, contractile dysfunction may supervene,
often preceding the onset of dyspnoeic symptoms.
An EF < 60% has been shown to be associated with poorer
survival rates after corrective surgery and is likely to indicate
underlying contractile dysfunction inMR patients.
3,8,26
The majority
of our patients had markedly enlarged LA sizes (
n
= 84, 66% with
LA
> 55 mm) and elevated PASP (
n
= 66, 50% with PASP > 60
mmHg), indicating that these subjects had severe chronic MR
of sufficiently long duration for such advanced changes to have
developed. Chronic MR therefore requires careful monitoring by
experienced clinicians and repeated echocardiographic assessments,
which would reveal the onset of ventricular decompensation and
the need for early surgery in such cases.
The timing of surgery in patients with severe MR is a critical
factor in the preservation of myocardial function.
27-29
Wisenbaugh
et al
. have shown that pre-operative ESD is the only independent
predictor of postoperative death.
25
Whereas a good outcome was
predicted at a pre-operative ESD of 40 mm, they showed that
the risk of severe heart failure and/or death sharply increased
when it reached 51 mm. Taking these observations into account,
the recommended optimal time for surgery can be derived at an
LVESD between 40 and 50 mm, MV repair being the preferred
surgical intervention when LVESD reaches 50 mm.
8,12,15
Pulmonary hypertension is another independent predictor
of postoperative mortality, with the risk of death or occurrence
of heart failure being twice as high as in patients without
pulmonary hypertension.
30,31,33
The presence of pulmonary
hypertension depends on the severity of MR, the functional class
of the patient and the presence of LV dysfunction.
32,33
Significant
pulmonary hypertension (PAS > 50 mmHg) has been reported in
20 to 30% of patients with severe MR
30
and 64% of patients who
are in NYHA functional class III–IV.
31
The pre-operative PASP
was elevated beyond 50 mmHg in all EF groups in our study.
The majority of our patients was symptomatic and was
receiving heart-failure treatment, including ACE inhibitors.
Controlling symptoms in these patients with medical therapy
in the belief that LV function and cavity size are stable in such
patients is a misinterpretation of the evidence-based guidelines
for intervention, which recommend surgery in symptomatic
severe MR regardless of chamber dimensions.
5,27
The current
paradigm for managing severe MR is to offer early surgery in
these patients because of the difficulty in diagnosing underlying
LV dysfunction and because the long-term outcome may be
poor, even in subjects with good LV function as assessed by EF.
It is well established that pre-operative EF does not predict
long-term outcome following MVR.
27,34
Furthermore, surgery
may now be accomplished with low morbidity rates since
surgical outcomes have improved considerably with better
cardioprotection, and also with using the technique of MV
repair in subjects with significantly impaired LV function.
Limitations
This study has several limitations, among them being the
retrospective design, which resulted in incomplete datasets for
analysis, and the use of raw echocardiographic data, which were
not indexed to body surface area. Routine HIV testing prior to
surgery was not a prerequisite to surgery in the early years when
many subjects were not tested. In our study, HIV infection did
not explain the impaired LV function in the group with EF
40–49%. Furthermore, the low cardiac-related mortality rate
in our study (4%) may not be a true reflection of mortality, as
nearly one-quarter of patients failed to return for follow up. The
poor follow up after the six-week visit also resulted in reduced
numbers of matched pairs for comparison, thereby reducing
the total number of patients whose data could be interrogated
for statistical purposes. Also, in our study we did not routinely
use quantitative measurements such as calculation of the
effective orifice area and regurgitant fraction, which are now
recommended in both sets of guidelines.
4,5
Lastly, our cohort
of MR did not include patients with pre-operative EF < 40%
submitted for MVR as per the policy of our surgical unit, and
we could not make firm inferences from this small sample with
significantly impaired LV function.
Conclusion
In this study, a significant number of subjects with severe MR
presented with advanced symptoms and/or decompensated
HF with echocardiographic parameters that were well beyond
the guidelines recommended for surgical intervention. While
it is reassuring that surgical intervention improved cardiac
dynamics and LV function in the ensuing three to six months in
subjects with mildly impaired LV function, a cohort of patients
remained with impaired LV function, in part due to delayed
surgery. Several factors accounted for surgery being performed
in the very late stages of the natural history of MR in our
patients, among them the primary reason being socio-economic
challenges associated with lack of access to healthcare as a
result of a failing public healthcare system. Pre-operative ESD
was the only predictor of postoperative LV dysfunction. Chronic
organic MR therefore requires careful clinical surveillance and
prompt referral for regular echocardiographic assessment to
enable early detection of LV dilatation and timeous surgery in
order to preserve ventricular function.
References
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Incidence and characteristics of newly diagnosed rheumatic heart disease