CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 6, July 2012
328
AFRICA
ST-depression to be the most predictive ECG characteristic of
cardiovascular disease (CVD) and CHD mortality, lending an
average two-fold risk of CVD and CHD mortality, and, as with
our study, predicting these outcomes from their mere presence
at baseline.
19
Studies reporting on the ECG in prognostication of PPCM
remain scarce, with two from Nigeria suggesting it to be a weak
predictor of recovery and long-term prognosis in PPCM.
29,30
However these studies did not use echocardiography to confirm
the diagnosis of PPCM,
30
and had a greater proportion of
patients with hypertension than those without.
29,30
Given recent
insight that patients with the PPCM phenotype who present with
hypertension appear to follow a different natural history to those
without,
2
any comparisons between data from PPCM patients
with hypertension with those without hypertension should be
interpreted with great caution.
Systematic reports of ECG abnormalities associated with
idiopathic dilated cardiomyopathy (IDCM), which bears some
resemblance to PPCM, are few. One such study of IDCM
reported that the ECG was found to be normal in up to 25% of
affected relatives of IDCM patients (who by definition suffer
from familial DCM), although these were not all newly diagnosed
IDCM cases.
31
Hence, as in our study, an overwhelming majority
had abnormal ECGs.
It remains fair to say that the shortage of studies systematically
reporting on the prevalence of ECG anomalies in PPCM may
account for most for our inability to corroborate our findings
with other available evidence, yet no reports contradict our
findings. Overall, therefore, our data can only suggest that
the 12-lead ECG in PPCM may be sensitive to underlying
LV dysfunction and/or that it can serve as a marker of more
extensive cardiac insult early in the disease process.
Lastly, we note that the 1% prevalence of first-degree heart
block, usually not considered to bear any significant risk to
adverse CVD outcome, except for its association with lamin A/C
mutation in familial DCM, may in our PPCM cohort merely
reflect the 1–2% prevalence in normal young adults.
32
However,
after recent reports implicating this so-called benign form of
heart block in the general population with increased risk of atrial
fibrillation and adverse CVD outcome 20 years down the line,
32
and suggestions that post-exercise measurements of PR intervals
may be more prognostic within five-year follow-up periods
than resting ECG PR intervals,
32
it would be useful to revise the
prognostic implications of first-degree heart block post exercise
in patients with underlying myocardial disease and congestive
cardiac failure as in PPCM.
Furthermore, evaluation of this conduction disorder may be
of particular importance in PPCM, in view of several reports
of first-degree AV block being among one of the earliest
signs of lamin A/C mutation, which in turn commonly leads
to a phenotype of apparently unexplained DCM.
33
It is worth
considering that the prognostic implications behind each of
the criteria for major and minor ECG abnormalities/variants
derived from the Minnesota code appear more applicable in the
screening of high-risk persons only,
34
as in this clinical context.
This pilot study has a number of limitations that require
comment. Firstly, the Minnesota code may not be sufficiently
validated for the detection of heart disease in pregnant women.
Moreover, the ‘normal’ 12-lead ECG in African women is yet
to be definitively described. Whether the combined presence
(81% of cases) of major abnormalities and minor variations is
sufficient to support further investigation of the 12-lead ECG as
a screening tool (particularly when there are few data to describe
the ‘normal’ 12-lead ECG in pregnant and non-pregnant African
women), is open to debate.
In determining the sensitivity of ECG changes over time,
relative to underlying LV dysfunction, we had valid data for
only 56% of the cohort. Although our PPCM patients who
did not have follow-up ECGs did not differ in clinical and
echocardiographic outcome from those with follow-up data, the
possibility that the former group may have been clinically worse
off than those with six-month data cannot be excluded, given
that greater proportions of the former manifested minor T-wave
anomalies, and that their left ventricular diameters and BMI at
baseline appeared greater than those who had six-month ECGs.
However, in light of the lower prevalence of QRS-axis deviation
and bundle branch block among the former group, interpretation
of the similarity of patients with and without follow up with
regard to ECG characteristics becomes speculative.
Further data are required to better characterise the 12-lead
ECG as a marker of LV dysfunction in this specific clinical (and
ethnic) context, before any firm recommendations can be made
in respect of obtaining a 12-lead ECG at the conclusion of each
pregnancy in sub-Saharan Africa.
Conclusions
Despite a number of limitations, this still represents a unique
study that will prove to be invaluable in determining the future
role of the 12-lead ECG as an inexpensive and simple ‘rule-out’
screening tool for PPCM, and perhaps an important tool for
increasing the intensity of subsequent treatment and management.
Overall, we found the majority (96%) of PPCMpatients presented
with ‘abnormal’ 12-lead ECGs, which improved significantly to
75% after the first six months of treatment. Over 80% of patients
displayed either major abnormalities or minor variations using
the Minnesota code. Of these, sinus tachycardia and QRS-axis
deviation were most likely to be attenuated after six months.
Even though these ECG abnormalities were mostly non-specific
and similar to those of other dilated cardiomyopathies, our study
further suggests the ECG to be useful in simple monitoring
of clinical progress during treatment and prognostication.
Specifically, the baseline presence of major T-wave and
ST-segment abnormalities in the context of PPCM patients may
place these patients at similar risk of adverse outcomes to those
with myocardial ischaemia. More definitive studies are required
to determine if this simple and relatively inexpensive tool will
prove to be of particular clinical use in the setting of PPCM. Any
progress in this regard will be welcome, given the persistently
poor health outcomes associated with PPCM in resource-poor
settings.
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