CARDIOVASCULAR JOURNAL OF AFRICA • Volume 25, No 2, March/April 2014
78
AFRICA
Cardiovascular Topics
Impact of prehypertension on left ventricular mass and
QT dispersion in adult black Nigerians
OK Ale, JN Ajuluchukwu, DA Oke, AC Mbakwem
Abstract
Background:
Prehypertension has been associated with
target-organ damage. This study sought to determine the
impact of prehypertension (PHT) on QT dispersion and left
ventricular hypertrophy (LVH) in adult black Nigerians.
Methods:
One hundred and one subjects with office blood
pressure (BP)
<
140/90 mmHg were categorised according to
their office BP into normotensive (BP
<
120/80 mmHg,
n
=
57) and prehypertensive (BP 120–139/80–89 mmHg,
n
=
44)
groups. Echocardiography and electrocardiography (ECG)
were performed on the subjects.
Results:
Thirty-four males aged 53.65
±
16.33 years and 67
females aged 52.42
±
12.00 years were studied. The mean
QT interval dispersion (QTd) of the normotensive (38.96
±
11.06 ms) and prehypertensive (38.41
±
11.81 ms) groups
were similar (
p
=
0.81). Prehypertensive subjects had higher
left ventricular mass (LVM) (165.75
±
33.21 vs 144.54
±
35.55 g,
p
=
0.024), left ventricular mass index 1 (LVMI-1)
(91.65
±
16.84 vs 80.45
±
18.65 g/m
2
,
p
=
0.021) and left
ventricular mass index 2 (LVMI-2) (54.96
±
10.84 vs 47.51
±
12.00 g/m
2.7
,
p
=
0.017). QTd was independent of echocardio-
graphic and electrocardiographic LVH (
p
>
0.05).
Conclusion:
Compared with normotension, prehypertension
is associated with higher LVM but similar QTd. This suggests
that structural remodelling precedes electrical remodelling in
prehypertension.
Keywords:
prehypertension, left ventricular hypertrophy, left
ventricular mass, QT dispersion, adult black Nigerian
Submitted 18/10/13, accepted 20/2/14
Cardiovasc J Afr
2014;
25
: 78–82
DOI: 10.5830/CVJA-2014-010
The heterogeneity of individuals with blood pressure (BP)
<
140/90 mmHg in terms of cardiovascular (CV) risk was reported
as early as 1939 by Robinson and Brucer.
1
BP in the range
of 120–139/80–89 mmHg (labelled then as prehypertension)
was observed to be associated with high risk of progression to
hypertension (HT) and cardiovascular disease (CVD) later in life
when compared with BP
<
120/80 mm Hg.
1
The term prehypertension was adopted in May 2003 by the
Seventh Report of the Joint National Committee on Prevention,
Detection, Evaluation and Treatment of High blood Pressure
(JNC-7) to describe BP range of 120–139/80–89 mmHg.
2
The
resuscitation of this terminology/concept in JNC-7 was a sequel
to the documentation of a higher morbidity in individuals with
prehypertension in landmark publications.
3-5
Prehypertension
(PHT) was defined in JNC-7 not only to emphasise the excess
risk associated with BP in this range, but also to focus increased
clinical and public health attention on prevention.
2,6,7
Prevalence rates of PHT among adults in the United States,
Ghana and northern Nigeria have been reported to be 31, 40
and 58.7%, respectively.
7-9
In most studies, including the ones
above, PHT was more prevalent than hypertension.
7-9
Though
PHT is associated with increased risk of major CV events
independently of other CV risk factors,
10
most individuals (90%)
with PHT have at least one cardiovascular risk factor such as
dyslipidaemia, abdominal obesity, hyperinsulinaemia, impaired
fasting glucose levels, insulin resistance, a prothrombotic state,
tobacco use, endothelial dysfunction, and impaired vascular
distensibility.
6,7,9,10
QT interval dispersion (QTd) (the difference between the
longest and the shortest QT intervals on a surface ECG), when
excessive, is associated with increased risk of cardiovascular
morbidity and mortality in population studies, and many clinical
conditions, including hypertension.
11,12
This has been related
to ventricular electrical instability, providing the necessary
substrate for lethal ventricular arrhythmias.
12,13
Greater QTd and
left ventricular mass have been demonstrated in hypertensive
individuals compared with normal individuals.
11,13,14
Considering the well-established, linear relationship between
BPandtheriskofcardiovascularevents,theCVriskassociatedwith
PHT is intermediate between normotension and hypertension.
2,3
Hence, electrocardiographic and echocardiographic indices of
target-organ damage in PHT may also be intermediate between
normotension and hypertension. The aims of this study were: (1)
to compare the QTd and indices of left ventricular hypertrophy
in adult black normal and prehypertensive subjects, and (2) to
evaluate the relationship of QTd with electrocardiographic and
echocardiographic indices in these subjects.
Department of Medicine, College of Medicine, University of
Lagos/Lagos University Teaching Hospital, Lagos, Nigeria
OK Ale, MBBS, MPH, FMCP,
JN Ajuluchukwu, MBBS, MMed, FMCP
DA Oke, MBBS, FMCP
AC Mbakwem, MBBS, FWACP
