CARDIOVASCULAR JOURNAL OF AFRICA • Vol 22, No 6, November/December 2011
AFRICA
301
Discussion
Hypertension is the commonest cardiovascular disease in Nigeria
and sub-Saharan Africa. It is the commonest risk factor for heart
failure, stroke and chronic renal impairment. In Nigeria and
most African countries, the majority of patients first present
with evidence of target-organ damage such as overt heart failure.
Most often, overt heart failure is preceded by asymptomatic left
ventricular systolic dysfunction. Information on the prevalence
and burden of both symptomatic and asymptomatic LVSD is
based on population studies as well as studies done in hyperten-
sive subjects in Europe and America.
21-23
The burden of LVSD (symptomatic or asymptomatic) in
hypertensive subjects is largely unknown in Nigeria and in
most African countries, hence the reason for the present study.
Echocardiographic methods have been shown to provide a high
yield of quantitative measurement of LV function and can be
used to assess the determinants of LV function, both in hyperten-
sive and general populations.
The main findings of the study are: the majority of our hyper-
tensive patients fell within the middle-aged group with a peak
age of 50 years, about 18% of our hypertensive subjects had
asymptomatic LVSD, the prevalence of LVSD was higher in men
than in women, LVSD increased with age, although LVSD was
independent of age, and the main predictors of LVSD were male
gender, body mass index, left ventricular mass and LV relative
wall thickness.
All over sub-Saharan Africa, the peak age of presentation
of cardiovascular diseases such as hypertension has been well
defined.
24-26
As in the present study, most patients are within the
age group of 40 to 60 years, often with a peak age of 45 to 50
years, as observed in this study. The implication is that where
complications arise, it is usually associated with high DALYs,
with a huge impact on the socio-economic growth of the family
and nation, as the population affected is in the prime of life. This
is contrary to the situation in developed countries where most
cardiovascular diseases manifest after the age of 65 years.
In a univariate analysis, age was related to LVEF. However,
when other factors such as gender, LV mass, relative wall thick-
ness and BMI were factored in, the association with age became
insignificant. The plausible reason for this is that the impact of
age on LVSF is probably mediated through other factors. Our
finding is similar to the report of other workers.
22,23,27,28
The study shows that the prevalence of impaired LVSF is
about twice as common in men as in women. In a multivariate
analysis, male gender was found to be an independent predictor
of impaired LVSF. This is similar to the findings of authors in
studies done in hypertensive subjects or in the general popula-
tion.
21-23,28
The reasons for this are not clear but it is well known
that cardiovascular diseases generally occur earlier in men than
in women. In our setting, women are also more likely to attend
follow-up clinics as well as take their medication as prescribed.
Tables 1 and 2 show that diastolic blood pressure and mean
arterial blood pressure were higher in the group with severe
LVSD compared to other groups. No significant difference was
found in the systolic blood pressure and pulse pressure among
the groups.
In univariate and multivariate analyses, blood pressure was
not found to be related to LVSF. This finding is similar to that of
Devereux
et al
.,
22
but at variance with studies done in the general
population, where the relationship of blood pressure with LVSF
persisted in the multivariate analysis.
21,29,30
This may be may be
due to the fact that most of our patients were on antihypertensive
medications.
In this study, BMI was found to decrease from subjects
with normal LVSF to those with severe LVSD (although the
lowest BMI was in those with moderate LVSD in both men and
women). The impact of BMI persisted in the multivariate analy-
sis. This relationship between LVSF and BMI was also reported
by Devereux
et al
.
22
Because our population was relatively lean,
one plausible reason for the finding may be the known relation-
ship between chronic LVSD and weight loss (cardiac cachexia).
In a univariate analysis, we did not find any relationship
between LVSD and the presence of diabetes in this study. This is
at variance with the report by some workers.
21,22
The reason for
the negative finding in our study may be that we relied on self-
reported history of diabetes. Many more subjects with diabetes
could have been detected if metabolic profiles were run in our
study subjects.
The left atrial size was found to be independently related to
LVSF. The larger the left atrium, the poorer the LVSF. Similar
findings have been reported by other investigators.
31,32
Left atrial
size is a known strong marker or surrogate of left diastolic func-
tion. The latter is known to have a positive relationship with
LVSF.
33,34
Limitations of the study
We noted the following limitations with this study. It was a
hospital-based study and may not reflect the situation in the
general population. We did not run metabolic profile functions
(blood glucose, lipid, uric acid, insulin levels, etc) in the present
study, as was done in studies in industrialised nations, due to
lack of funds
Newer measures of assessment of LVSF such as LV mid-wall
shortening, circumferential end-systolic measurements as well as
measures of arterial wall stiffening (pulse pressure/stroke index)
were not assessed in our study. Absence of ischaemic heart
disease was only assessed based on clinical history and 12-lead
ECG. This may not exclude sub-clinical ischaemic heart disease.
Conclusions
LVSD, assessed as ejection fraction
<
50%, was detected in
18.1% of our hypertensive population, who did not have symp-
toms of overt heart failure. Male gender, body mass index, LVM
and relative wall thickness were found as independent predictors
of LVSF in our study.
Significant numbers of hypertensive subjects in this study
had varying degrees of left ventricular systolic dysfunction.
Early introduction of disease-modifying drugs in these patients,
such as angiotensin converting enzyme inhibitors/angiotensin
receptor blockers may retard or prevent the progression to overt
heart failure.
It must be stated that since echocardiography is expensive,
it cannot be placed as the first line of systematic screening of
hypertensive patients, however, the predictive factors of LVSD
are accessible to primary-care physicians. For instance, the
combination of male gender and obesity should draw the atten-
tion of clinicians to the possible presence of LVSD, a pathogenic
precursor of heart failure.
