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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 28, No 6, November/December 2017
406
AFRICA
Letter to the Editor
NT-pro BNP and plasma-soluble ST2 as promising
biomarkers for hypertension, hypertensive heart disease
and heart failure in sub-Saharan Africa
Dear Sir
In three recent publications,
1-3
Ojji and colleagues reported on
the role of two novel biomarkers, NT-pro-BNP and plasma
soluble ST2, for differentiating sub-Saharan African people
with hypertension (HT) without left ventricular hypertrophy
(LVH) and without heart failure (HF) from hypertensive people
with LVH (HTLVH) and those with HF (HTHF). The authors
clinically and echocardiographically evaluated a group of 210
patients with hypertension residing in Abuja, the capital city
of Nigeria. All these patients had measurements done for the
cardiac neurohormone NT-pro-BNP and for soluble ST2, which
is a novel cardiac biomarker of mechanical strain.
In the first publication,
1
in which they investigated the effect
of LV remodelling on the concentration of soluble ST2, the
authors found that subjects with HTHF had higher plasma
ST2 concentrations compared to those with HTLVH and those
with HT (134.7
±
57.3 vs 23.0
±
8.3 vs 14.5
±
4.9 ng/ml, all
p
<
0.0001). Soluble ST2 also had a strong correlation with clinical
and echocardiographic parameters. The authors concluded that
‘Plasma ST2 is a useful biomarker in not only differentiating
HTHF from HT with or without LVH, but also distinguishes
hypertensive LVH from HT without LVH’.
In the second publication,
2
the authors investigated the
relationship between soluble ST2 levels and LV geometric
patterns in the same cohort of patients with HT and found that
patients with concentric LVH had higher soluble ST2 levels
compared with patients with normal LV geometry (20.4
±
8.4
vs 14.3
±
5.4 ng/ml,
p
<
0.002). This also led to the conclusion
that ‘soluble ST2 level is not only affected by hypertensive LVH,
but may be a future biomarker in differentiating concentric
hypertrophy from normal geometry in hypertension’.
In the third study,
3
the authors examined the effect of NT-pro-
BNP on LV and RV remodelling in this same hypertensive
African cohort. Participants with HTHF had significantly higher
NT-pro-BNP levels compared to those with HTLVH. Based on
these results, the authors proposed that NT-pro-BNP could be
a useful biomarker for differentiating HT with or without LVH
from HTHF in black hypertensive subjects.
The conclusions drawn by these authors are valid exclusively in
the study context for a number of reasons. First, it is important to
remember that hypertension and hypertensive heart disease, which
are potentially preventable diseases, are themain contributors of the
growing burden of heart failure in SSA.
4
Second, echocardiography
is globally the cornerstone of the routine assessment of various
types of hypertensive heart disease as it allows for the detection of
normal left ventricular concentric remodelling, concentric versus
eccentric LVH, and HF with the possible differentiation between
HF with reduced ejection fraction and HF with preserved ejection
fraction using tissue Doppler imaging, as well as the measurement
of pulmonary artery pressure, another prognostic marker in this
population.
5
However, echocardiography remains expensive, less
available in most SSA settings, and requires experts both for its
performance and interpretation. For these reasons, requesting
cardiac echocardiography in most settings in SSA is like searching
for the goose that lays the golden egg.
There is value therefore in using circulating biomarkers, which
could be useful as surrogate markers of the heart disease process
in resource-poor settings. Natriuretic peptide (BNP and NT-pro-
BNP) levels have been shown to accurately reflect left ventricular
pressure, and studies have found that peptide levels are sensitive
and specific for diagnosing heart failure and also relevant for risk
stratification.
6,7
There is no doubt that the third study by Ojji
et
al
.
3
is a confirmation of the usefulness of the diagnostic role of
NT-pro BNP in the SSA setting and it has immediate relevance
for clinicians.
Contrary to NT-pro BNP measurement, which is already an
established gold standard for HF, soluble ST2 as a biomarker has
been less investigated. Just as with other novel biomarkers, such
as mid-regional pro-atrial natriuretic peptide (MR-proANP)
and galectin-3, which are promising diagnostic and prognostic
biomarkers beyond established natriuretic peptides, the role
of soluble ST2 in the clinical care of patients is yet to be
established beyond any doubt. It is very encouraging to note
that, as suggested by Ojji and co-workers, soluble ST2 can help
differentiate HT, HTLVH and HTHF, as well as concentric LVH
from normal LV geometry.
The relevance of these three studies by Ojji and co-workers
in this particular context should however not completely
Department of Medicine, University of Cape Town, Cape
Town, South Africa; Douala General Hospital and Clinical
Research Education Networking and Consultancy, Douala,
Cameroon; Faculty of Health Sciences, University of Buea,
Buea, Cameroon
Anastase Dzudie, MD,
aitdzudie@yahoo.comDouala General Hospital, and Clinical Research Education
Networking and Consultancy, Douala, Cameroon; Faculty
of Health Sciences, University of Buea, Buea, Cameroon
Bonaventure Suiru Dzekem, MD
Department of Medicine, University of Cape Town, and
Non-Communicable Diseases Research Unit, South African
Medical Research Council, Cape Town, South Africa
Andre Pascal Kengne, MD