Apexcardiography proved to be a practical, non-invasive method for
measuring cardiac function in the dog. Simultaneous recordings of
the electrocardiogram, apexcardiogram and phonocardiogram were
studied in normal dogs before and after the experimental production
of ischaemic heart disease and in naturally-occurring clinical cases
of cardiac failure.
Recordings of the apexcardiogram were found to have a variable
morphology depending on the site of the transducer on the thorax.
The optimum site was over the point of maximum apical impulse,
between the 5th and 7th ribs in the majority of dogs.
The apexcardiogram in dogs after experimental production of
ischaemic heart disease and in clinical cases demonstrated few
deviations from normal. The abnormalities observed in
apexcardiograms from human cardiac patients were not consistently
recorded in this study. Qualitative information in apexcardiograms
alone does not appear to be a reliable guide to cardiac function in
Simultaneous recordings with ECGs and PCGs provided a temporal
relationship which may be used to quantify events of the cardiac
cycle. STI were derived and normal values established for both
anaesthetised and conscious dogs. The STI in dogs with cardiac
malfunction after experimentally-produced ischaemic heart disease
showed little deviation from normal.
STI were further derived from dogs with heart failure or
sub-clinical heart disease and were obtainable in the majority of
clinical cases. A significant prolongation of pre-ejection period
often accompanied by a decrease in left ventricular ejection time
was observed in those dogs considered to have cardiac failure.