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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 28, No 1, January/February 2017
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AFRICA
with acute HF. Because the echocardiographic evaluations
performed in the current study were not done close to the time
of admission in many patients, the worst measures may have
been missed. It is also possible that some specific characteristics
of the patient population may have contributed to this lack of
association.
Increased resting heart rate is a known predictor
for cardiovascular mortality and morbidity in a variety of
cardiovascular diseases, including HF.
26
In patients with reduced
LVEF, with or without signs or symptoms of HF, high heart rate
has predicted adverse outcomes, irrespective of other known
risk factors.
27
Several pathophysiological mechanisms, including
blunting of the force–frequency relationship, the induction of
myocardial ischaemia, precipitation of rhythm disturbances, and
acceleration of atherosclerosis have been proposed to explain
the association between higher heart rate and worse outcomes in
patients with HF.
26
Higher heart rate might also be a marker of greater
neurohormonal activation. The SHIFT study showed that heart
rate is important in the pathophysiology of HF with reduced
LVEF, and that heart rate reduction
per se
is a mechanism
responsible for improvement in clinical outcomes.
28
The CHARM investigators also found that the value of
resting heart rate in predicting worse outcomes was independent
of baseline left ventricular systolic function in heart failure.
29
A
higher heart rate was associated with a greater risk of hospital
stay for HF, both in patients with reduced and preserved LVEF
in a
post hoc
analysis of the DIG (Digitalis Investigation Group)
trial. In predicting mortality, however, higher heart rate was only
significant in patients with a reduced LVEF.
30
Similar to our findings, left atrial size or its surrogates have
been shown to predict hospitalisation for HF and death in other
studies.
31
Left atrial size predicts death among high-risk groups,
such as patients with dilated cardiomyopathy, LV dysfunction,
atrial arrhythmias, acute myocardial infarction, as well as in in
the general population.
32
Left atrial size, aortic stenosis, heart rate and measures
of hypertrophy had some value in predicting outcome in our
cohort. This may suggest that early diagnosis and treatment of
hypertension and valvular heart disease in sub-Saharan Africa
should be emphasised to improve outcome.
Limitations
Our data should be interpreted in the context of their limitations.
Unobserved variables may have confounded the results. Not
all echocardiographic parameters were available in all patients,
limiting the number of parameters for analysis. The variable
timing of the echocardiogram and inter-observer variability
may have affected the specific results obtained. Furthermore,
the number of events was small. Therefore both the variable
selection and the parameter estimates for the selected variables
are subject to instability.
We also looked at echo predictors of acute HF from various
causes. Even though there was no statistically significant
interaction between the echo variables, different conditions and
outcomes, there could still be a dilutional effect of grouping
heterogeneous conditions together.
Finally, our results are drawn from a population of young
acute HF patients predominantly with systolic dysfunction.
Consequently, these findings may not apply to older patients or
to those with preserved LVEF.
Conclusions
In accordance with previous studies, echocardiographic
variables, especially those of left ventricular size and function,
were found to have little or no additional predictive value in
patients admitted for acute HF. Left atrial size was associated
with death or re-admission within 60 days while left ventricular
posterior wall thickness and the presence of aortic stenosis were
associated with the risk of death within 180 days. There is a need
for further studies of echocardiographic evaluation, especially
when performed closer to the acute event, to further elucidate
the pathophysiology and risk stratification of patients with acute
HF.
The THESUS-HF study was funded by Momentum Research Inc, Durham,
North Carolina, United States of America
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