Cardiovascular Journal of Africa: Vol 22 No 2 (March/April 2011) - page 20

CARDIOVASCULAR JOURNAL OF AFRICA • Vol 22, No 2, March/April 2011
74
AFRICA
with 100% occurrence in the other parity groups: parity 0 and
parity one to three (
p
<
0.005) (Table 4).
T-wave inversion in lead III
±
any other lead was commoner
in the pregnant group than the controls (23.2 vs 10%, RR
=
2.319, CI
=
1.018–5.284,
p
=
0.0364). By contrast, tall and
broad T waves in V
2
–V
6
occurred more commonly in the control
group than the pregnant group (18.6 vs 5.8%, RR
=
0.312, CI
=
0.107–0.910,
p
=
0.0215).
The QTc was prolonged in a minor proportion of both the
pregnant and control groups (4.3 vs 8.6%). The prolongation was
however in the range of 0.46–0.47 s.
Discussion
This study showed that pregnancy in Nigerian women might be
associated with cardiac and electrocardiographic changes, includ-
ing low DBP, systolic ejection murmur, higher heart rate, normal
frontal-plane QRS axis, rarity of Negroid-pattern ST elevation
and significant LVH based on Araoye’s criterion among blacks.
The low DBP was expected, because pregnancy reduces
systemic vascular resistance and afterload, as a result of periph-
eral vasodilatation and the low resistance, high flow circulation
of the uterus and placenta.
3
In this study, significantly lower DBP
was nearly three times more common in the pregnant patients
than in the controls, and this was supported by other studies.
2,3
Furthermore, by eight weeks’ gestation, the systemic vascular
resistance fell by 70% of its preconception value.
12
The common clinical findings in this study were tricuspid
systolic murmur ranging from grade 1–3 and loud P
2
. The signif-
icant cardiac findings were still observed in the pregnant group,
even after controlling for the possible effect of the estimated
gestational age. These clinical findings were observed because
the majority of the pregnancy-induced changes, such as reduced
systemic vascular resistance, increased cardiac output, increased
stroke volume and reduced arterial pressure occur during the first
eight weeks of gestation.
12
The ECG heart rate reached statistical significance between
the two groups. Pregnancy has been well known to cause an
increase in heart rate but not to the level of tachycardia. Only
8.7% of the pregnant patients had sinus tachycardia, against
2.9% of the control group. This was supported by previous stud-
ies, which reported that pregnancy only marginally increased
heart rate by about 10–20 beats/min.
1-3
The frontal-plane QRS axis was normal in all pregnant
subjects, as previously reported.
13
Axis deviation was not found
in any of the study participants. Other studies have reported left
and right axis deviation associated with normal pregnancy.
3,5,13
We suggest that population-specific differences may account for
this variation.
The incidence of atrial and ventricular premature complexes
during pregnancy is unknown.
13
The low incidence in this study
compared with what was obtained in normal non-pregnant
subjects, as it is not unusual to find these occasional ectopics in
normal non-pregnant subjects.
9
The rarity of the ‘normal Negroid-pattern’ ST elevation in
the study subjects might mean that the expected pregnancy-
associated ST segment sagging, as previously reported in some
studies,
5
depressed the ST segment to the isoelectric line. T-wave
inversion in lead III
±
any other lead was about twice as common
in the pregnant group as in the controls. This has been reported in
previous studies and is attributable to outward and upward shift
of the cardiac apex by the enlarging uterus.
5
In this study, no case of atrial fibrillation or flutter, other
supraventricular tachyarrhythmias (SVT) or ventricular tachy-
cardia was found. These conditions are rare in normal pregnan-
cies and their presence should raise the suspicion of underlying
severe cardiac disease during pregnancy.
13
Non-specific intraventricular conduction defect (in avF)
was found more frequently in the pregnant group (3.551, CI
=
1.230–10.252,
p
=
0.0105). Similarly, tall and broad T waves
in V
2
–V
6
were found less commonly in the pregnant group than
in the control group (0.312, 0.107–0.910,
p
=
0.0215). These
had not been previously reported. We suggest the possibility of
population-specific, pregnancy-related ECG changes. Further
studies are needed to clarify this.
LVH determined fromAraoye’s criterion was higher in preva-
lence among the pregnant subjects, based on identification with
increased voltage in the R wave of lead 1
>
12 mm (0.087, CI
=
0.019–0.155,
p
<
0.05). This was in support of previous stud-
ies, which had demonstrated that the heart is enlarged by both
chamber dilatation and hypertrophy as a result of the haemo-
dynamic changes that occur in pregnancy.
5
Acute physiological
LVH can occur rapidly during a normal human pregnancy, as an
adaptive response to increased preload and cardiac work.
14
This
can be demonstrated during the second trimester and is most
marked at the end of pregnancy.
15
Even in a first pregnancy,
the cardiovascular adaptation (LVH inclusive) begins early, can
persist postpartum and appears to be enhanced by a subsequent
pregnancy.
16
The follow up of the patients eight weeks postpartum with
a repeat ECG revealed normal voltage in the ECG in one out
of two subjects who reported back for follow up. Reversal of
chamber and hypertrophic changes of normal pregnancy has
been shown to occur from a variable period of eight weeks to
more than one year post delivery, due to the reversal of the
haemodynamic changes associated with pregnancy.
14-18
However,
the proportion of subjects who reported back was too small to
draw a meaningful conclusion on this and further studies are
therefore suggested.
In Table 4, multiparity (
>
three) showed statistical signifi-
cance in only the ST-segment isoelectric line parameter (
p
<
0.005), where three out of five in the more-than-three pari-
ty group were affected. The volume-overloaded state (with
increased preload) of pregnancy causes physiological LVH;
17
after the first pregnancy, subsequent pregnancies have been
shown to enhance this.
16
Similarly, as mentioned, the expect-
ed pregnancy-associated ST-segment sagging depressed the
‘Negroid pattern’ ST-segment elevation to the isoelectric line.
LVH is responsible for the ST segment sagging, hence the
parity-related enhancement of the physiological LVH would
account for more multiparous women having their ST segment
on the isoelectric line.
However, findings from our study were not in conformity
with above arguments, as fewer patients in grand multiparous
groups had demonstrable ST isoelectric lines. Echocardiographic
indices could elucidate more correctly these haemodynamic
changes and clarify this grey area.
The major limitation in this study was the small sample size
and this is evident in the wide range demonstrated in the various
confidence intervals.
1...,10,11,12,13,14,15,16,17,18,19 21,22,23,24,25,26,27,28,29,30,...60
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