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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 32, No 3, May/June 2021
AFRICA
153
majority of subjects had an EF > 55%, only 60% (
n
= 43) showed
improvement in the postoperative EF to pre-operative values
(EF > 55%) at six months. This suggests that most subjects had
some degree of LV impairment as reflected by the median post-
operative EF of 42%, which reflects the true EF upon removal of
the low-pressure run-off into the LA following valve replacement.
Nevertheless, the majority of subjects underwent uneventful
surgery and postoperative heart failure gradually improved over
time. The five documented early deaths in the study occurred in
subjects who presented to hospital
in extremis
(
n
= 2), or suffered
postoperative complications (
n
= 3).
There were significant differences in LVEDD and LVESD
values in the respective EF groups, demonstrating an increase in
these chamber dimensions as the EF decreased (Table 2). These
findings suggest that there are lesser
changes in LV configuration
when LV function is preserved in the setting of severe MR.
Furthermore, the LA was similarly dilated in all EF groups,
reflecting both the severity and duration of MR prior to surgery.
16,17
In our study, the EF decreased significantly from a median of
63% pre-operatively to 45% postoperatively at two weeks. After
the initial decline postoperatively, the EF gradually improved
while the remaining echocardiographic parameters, LVEDD,
LVESD, LA and PASP, decreased steadily at follow-up visits.
Our findings showing an immediate decline in EF following
surgery is well described.
18,19
In Enriquez-Sarano’s study, the
EF showed a significant reduction from 58 ± 13% prior to
mitral valve surgery to 50 ± 14% following MVR.
18
Several
mechanisms explain the decline in EF following surgery in our
patients. As pointed out earlier, in many of these patients, LV
dysfunction was masked by the ventricular loading conditions
in severe MR, characterised by increased preload and reduced
afterload because of the run-off into the low-pressure LA
during systole. These loading conditions change immediately
after valve surgery when the leak has been corrected, exposing
the LV to full systemic pressure and unmasking the true state of
LV contractility.
20
In most cases, the immediate fall in EF that was observed after
surgery in our patients improved by six months.
15
Underlying
coronary artery disease with ischaemic LVdysfunctionwas unlikely
in our subjects because most of them were young black African
patients. The deleterious effect of ischaemic cardioplegic arrest
also contributes to the transient decline in early postoperative EF,
which must be expected in most subjects with MR.
Among those subjects who had a sharp fall in EF to <30%
immediately after the operation, five subjects recovered their
EF to > 50% at the six-month follow up and these five had
a median pre-operative EF of 65%. It is reassuring that in
subjects with mildly impaired LV function (EF 50–59%), the
EF improved steadily, albeit more slowly, compared to those
with preserved EF (> 60%). These data imply that although
impaired LV contractility is encountered in the immediate
postoperative period, myocardial function generally improves
over time, but reached normality earlier in subjects with
preserved pre-operative EF (Fig. 1), emphasising the need for
timeous surgical intervention in severe MR. This supports
current guidelines recommending surgery in asymptomatic
severe MR as soon as the LV begins to dilate (ESD > 40 mm) or
the EF approaches 60%.
Among the seven subjects with EF in the 40–49% range,
only three recovered their EF to > 50%. The development
of contractile dysfunction and its relation to the severity of
volume overload in MR is still not clearly understood.
12
It is well
recognised that prolonged contractile dysfunction eventually
becomes irreversible, even after the MR is corrected, and is
predictive of congestive heart failure and death.
7
Under these
circumstances, MVR is associated with higher morbidity and
mortality rates due to advanced LV impairment.
9
None of our
seven patients in the group with EF 40–49% (median EF 42%)
underwent mitral valve repair, which is recommended under
these circumstances. The choice of surgical procedure was
dependent on the available expertise at our centre to carry out
mitral valve repair, which is technically more difficult in RHD
patients compared to non-rheumatic MR.
12
The importance of adequate cardioprotection during
cardiopulmonary bypass is a critical factor that cannot be
underestimated in subjectswithalready compromisedLVfunction
from long-standing, severe MR. Myocardial ischaemia resulting
from a longer duration of cardioplegic arrest was reflected
in the prolonged CPBT in our subjects with postoperative
LV dysfunction, and no doubt contributed to persistent LV
dysfunction.
21
Lastly, Essop has emphasised the importance of
preserving the chords at surgery since any discontinuity in the
chordal–mitral apparatus could lead to further dilatation and
impairment of the LV after surgery.
12
Chordal preservation is
standard practice during MVR at our centre.
An important consideration is the presence of underlying
active carditis in young subjects undergoing MVR. Pure MVR
without stenosis causing heart failure is common in the young
who have severe active rheumatic carditis.
12,22
Early studies have
shown that heart failure is the predominant mode of death
in rheumatic carditis, explaining the high early mortality rate
among young patients with acute rheumatic carditis.
23,24
Annular
dilatation and chordal elongation have been described as the
main mechanism leading to mitral valve prolapse and severe
regurgitation during active carditis.
23,24
In total, evidence of active
carditis characterised by pericardial inflammation, chordal
elongation and/or chordal rupture was present in 55 (42%)
patients, which may well explain the impairment in LV function
in these cases. Early surgery is lifesaving in these patients and
the underlying ventricular impairment slowly improves in the
majority of cases.
12
In sub-Saharan Africa, RHD is responsible for the majority
of cases of chronic MR. Because of the compensatory
haemodynamics in chronic MR, many of these subjects present
late in the disease when symptoms are more advanced. This is
largely a result of poor socio-economic circumstances affecting
both rural and peri-urban communities. Socio-economic
challenges prevent timely access to care; these social inequalities
coupled with a resource-constrained health sector all contribute
to delayed referrals for specialist assessment and intervention. As
a result, most of our subjects with severe MR received surgical
intervention when their cardiac function had deteriorated beyond
the recommended cut-off points for surgical intervention as per
international norms. Furthermore, over-burdened, understaffed
and under-resourced state health institutions contributed to
incorrect and delayed diagnoses.
These factors led to delayed referral to the single tertiary centre
in KwaZulu/Natal (IALCH), where bed and theatre constraints
resulted in further delays before surgery was undertaken. As a
result two-thirds of patients presented with severe functional