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Abstract

The object of the investigation was to find a simple
test of cardiac function, using established methods, sufficiently
sensitive to detect deterioration of function before the advent of
clinical signs of heart failure. It was hoped, by comparing the
heart rate response to stress with changes in the systolic time
intervals, to be able thereafter to use the heart rate response
alone.
The systolic time intervals have been noted to change
with alterations in stroke volume, rate of flow and contractility.
The most appropriate method of measuring these intervals, and the
interpretation of these changes, was not altogether clear when the
investigation was begun in July, 1969. Assumptions had therefore
been made, based on the evidence available, and more recent work in
the literature has proved these assumptions to be justified. These
references, which refer to the use and significance of the pre-ejection
period, ejection period and total systole, corrected for
heart rate, have been included in the text.
A small pilot study was undertaken to determine whether
change of posture, release of venous cuffs or leg raising could be
employed as the stress but the results were inconclusive. A
difference was then found between subjects in the time of the return
of heart rate after the Valsalva manoeuvre and this was preceded by
a change in a systolic time interval. Relevant factors were therefore
reviewed and a plan of work designed. It was concluded from the reviews that, if the heart
reacted to changes in filling pressure by changes in stroke volume,
then the ability to eject the blood rapidly in the presence of the
resistance to flow induced by the manoeuvre would depend on the
cardiac response to sympathetic stimulation. This would be reflected
independently in the heart rate and systolic time intervals,
corrected for heart rate.
After the manoeuvre the heart rate and corrected ejection
period and total systole rose and then fell. But the time intervals
altered to an unexpected degree and in a manner suggesting they were
affected by the rise and fall of pressure and resistance. However,
compared with control subjects, in patients with ischaemic heart
disease corrected total systole and ejection periods increased more
and - together with the heart rate - fell more slowly to their resting
levels. In a larger series, the heart rate response alone
(number of beats from onset of fall to control heart rate) differentiated
control subjects from patients. The probable causes of
these differences and the application of the findings are discussed.

Item Type:	Thesis - Other Degree
Authors/Creators:	Cuthbert, R H
Keywords:	Heart function tests
Copyright Holders:	The Author
Copyright Information:	Copyright 1972 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).
Additional Information:	Thesis (M.D.) - University of Tasmania, 1972. Bibliography: p. 152-170
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