CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 7, August 2012
AFRICA
407
demonstrated an almost 10-fold under-appreciation of affected
patients, using conventional auscultation compared to portable
echocardiography.
23
It is currently being investigated whether
CAA improves the early identification of pathological heart
sounds in patients with rheumatic heart disease.
24
Co-existing cardiovascular disease during pregnancy is a
leading cause of maternal mortality and contributes to significant
morbidity.
25
Early identification of women with cardiac disease
is essential to managing the effects of cardiac disease during
and after pregnancy. Certain conditions such as rheumatic mitral
stenosis are poorly tolerated in pregnancy. It is likely that mitral
stenosis and other structural heart diseases would be identified
during routine antenatal screening of pregnant women in primary
healthcare clinics if CAA was used as a decision support tool for
nurses and doctors in the antenatal clinic.
The use of CAA in task shifting and telemedicine
A recent World Health Organisation report outlined the crisis
in human resources in healthcare, and focused on the particular
shortage of trained specialists in sub-Saharan Africa.
26
This
shortage has resulted in the shifting of tasks normally performed
by specialists, to mid-level and community health workers.
27
The
use of technology to support community health workers has been
recommended, as many other areas of medicine have benefitted
by incorporating technology to identify disease in remote areas
of the world.
28,29
A key issue regarding the health worker shortage in
sub-Saharan Africa is insufficient training opportunities.
Two-thirds of sub-Saharan African countries have only one
medical school, and 11 sub-Saharan African countries have no
medical school at all.
30
One of the solutions is the introduction
of distance learning and open-access teaching materials.
31
The
ability of the digital stethoscope to transmit banks of recorded
data for remote teaching suggests its utility for such a programme.
The computer interface also serves as a reminder to students of
the correct auscultation method (in terms of placement and
length of auscultation).
Another use of CAA is in the field of telemedicine. Recording
heart sounds using a digital stethoscope and transmitting
the sound data for remote assessment by a cardiologist was
demonstrated to have a sensitivity and specificity of 90 and 98%,
respectively, for the detection of pathological murmurs, with low
inter-observer and intra-observer variability.
32
Challenges and further development
Despite the potential of CAA, it has yet to be adopted into
mainstream clinical practice. There are several factors which
may improve the chances of adoption of this new technology.
33
Firstly, successful CAA systems must have a clearly defined
indication: screening, diagnosis, and/or teaching. In addition,
ease of use by personnel is of particular importance. Data must
be analysed in real-time and be stored in a format which can
be integrated into clinical records. From a technical standpoint,
standardised data sets would be of great benefit and need to be
highly sensitive and specific.
Finally, single-praecordial-site CAA does not approximate
the clinical routine of auscultation in different sites, use of
diaphragm, bell and adjunct manoeuvres to comprehensively
examine the heart. A new recording device using a multiple-
praecordial-site approach, simultaneously acquiring six
auscultation sites, a single-channel ECG and a respiratory
recording, is under development.
Conclusion
Heart disease is a major cause of morbidity and mortality in all
age groups worldwide. For decades, conventional auscultation
has been the mainstay for screening and diagnosis of structural
heart disease. However, the inherent limitations of the standard
stethoscope have resulted in declining reliance on auscultation
findings and the inappropriate referral for echocardiography of
large numbers of patients with innocent murmurs.
CAA provides objectivity to a traditionally subjective clinical
skill. As an objective diagnostic support tool, it may improve
the number of appropriate cases of murmur that are referred
for echocardiography from primary care. Furthermore, CAA
can provide a new platform for teaching cardiac auscultation
to health science students and physicians. Finally, CAA may
provide a decision support tool for mid-level and community
health workers, with linkage to central expertise and training
through telemedicine.
We thank Mr Thys Cronje for the photographs. As a Fogarty International
Clinical Research Fellow, Dr Zühlke is supported by the National Institutes of
Health, Office of the Director, Fogarty International Centre, Office of AIDS
Research, National Cancer Centre, National Eye Institute, National Heart,
Blood and Lung Institute, National Institute of Dental and Craniofacial
Research, National Institute on Drug Abuse, National Institute of Mental
Health, National Institute of Allergy and Infectious Diseases Health, and
NIH Office of Women’s Health and Research through the International
Clinical Research Scholars and Fellows Programme at Vanderbilt University
(R24 TW007988) and the American Relief and Recovery Act.
References
1.
McLaren MJ, Hawkins DM, Koornhof HJ, Bloom KR, Bramwell-Jones
DM, Cohen E,
et al.
Epidemiology of rheumatic heart disease in black
shcoolchildren of Soweto, Johannesburg.
Br Med J
1975;
3
(5981):
TABLE 1. CLINICAL USES FOR CAA
Screening for structural
heart disease
Screening for structural heart disease at primary healthcare level can be improved by the additional of an objective tool to aid
referral decision making. Areas where this could potentially be of application include pre-athletic screening, antenatal screening
of pregnant women, and screening for heart failure and early rheumatic heart disease in asymptomatic people.
Clinical teaching of
cardiac auscultation
CAA may aid in more directed teaching in cardiac auscultation. This includes specific training in auscultation sequence, length
of auscultation at each site, as well in the creation of data banks of auscultation recordings. Sounds can be relayed to multiple
listeners simultaneously, replayed at different speeds and a visual display can improve retention of information. CAA can also
be incorporated into distance-learning programmes.
Task shifting and
telemedicine
The global shortage of trained medical specialists requires the training of a new cadre of mid-level and community health
workers who may benefit from the use of CAA as a decision support tool in screening for structural heart disease. Telemedicine
may be used to link these cadres of health workers, who are often in remote areas, to clinicians and secondary and tertiary
centres.
