A micromanometer for chronic implantation

Goodman, A. H.; Angus, James A.; Einstein, Rosemarie; Cobbin, L. B.

doi:10.1007/bf02477382

Cited by 3 publications

(4 citation statements)

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“…The micromanometer has a resonant frequency of 1.5 kHz and a flat frequency response to 150 Hz with negligible phase shift or hysteresis. The details of the construction, calibration and performance of the manometer have been previously reported (Goodman et al, 1972b). A square-wave energized electromagnetic flow transducer (EMI, Australia) 18-20 mm i.d., was placed around the base of the ascending aorta to record aortic flow.…”

Section: Methodsmentioning

confidence: 99%

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The Influence of Alterations in the Cardiac Loading Conditions on Indices of Myocardial Contractility in the Anaesthetized Dog

Angus

Richmond

Cobbin

et al. 1977

Clin Exp Pharma Physio

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I . An online analogue computer was used to measure myocardial contractility as the ratio -where dP/dt is maximum rate of change of left ventricular pressure and IIT is integrated isometric tension. dP/dt IIT 2. In the open thorax anaesthetized dog, max (dP/dt) and dP/dt -were compared during alterations in preload, by partial vena caval occlusion, and changes in afterload obtained by acetylcholine injections and by partial occlusion of the descending thoracic aorta.3. A fall in preload lowered max (dP/dt) but did not alter dP'dt. -A rise and fall IIT 1 IT in afterload produced respectively an increase and decrease--& max (dP/dt) but dP/dt -__ was unaltered.IIT 4. From expanded time base recordings, the time from the start of aortic flow (EM flowmeter) to max (dP/dt) was measured to indicate the relationship between valve opening and rnax (JP/'dt). At low preload or eIevated afterload the aortic valve opened well after max (dP/dt) had been reached. When the afterload fell, max (dP/dt) occurred after the opening of the aortic valve. .Positive inotropic stimulation following intravenous isoprenaline caused a marked elevation in dP'dt. -However, the rise in max (dP/dt) was attenuated in comparison to dridt -by a marked fall in afterload and thus early opening of the aortic valve. 107 108 J. A. Angus et al. 6. It is concluded that max (dP/dt) is very sensitive to alterations in preload or afterload but the index is normalized so that changes in end diastolic fibre length do not alter this index. When the afterload falls max (dP/dt) is no longer determined in the isovolumic phase of contraction so that magnitude of rnax (dP/dt) is reduced. However, it is an empirical finding that IIT also falls so that the ratio is unaltered. -is a useful index of myocardial contractility that is insensitive to changes in preload or afterload.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

The Influence of Alterations in the Cardiac Loading Conditions on Indices of Myocardial Contractility in the Anaesthetized Dog

Angus

Richmond

Cobbin

et al. 1977

Clin Exp Pharma Physio

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“…Left ventricular pressure was measured by a catheter-tip micromanometer which was passed retrograde from the right common carotid artery (Goodman et al, 1972a). From this measurement the indices of peak dp/dt and (dp/dt)/IIT were derived.…”

Section: E T H O D Smentioning

confidence: 99%

“…From this measurement the indices of peak dp/dt and (dp/dt)/IIT were derived. The instrumentation for computing (dp/dt)/IIT ( s -~) has been reported elsewhere (Goodman et al, 1972b) and will only be briefly described here. The R wave of the ECG is used to trigger the onset of integration of the isovolumic pressure which is simultaneously differentiated and the dpldt signal passed to a peak read and hold circuit.…”

Section: E T H O D Smentioning

confidence: 99%

The effect of heart rate on indices of myocardial contractility in the dog

Richmond

Angus

Goodman

et al. 1975

Clin Exp Pharma Physio

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1. Changes in heart rate were evoked by atrial pacing in anaesthetized dogs with no pretreatment and in dogs given reserpine or guanethidine for 72 h. The effect of alterations in heart rate were related to two indices of myocardial contractility: the maximal rate of change of left ventricular pressure (dp/dt), and an index which was independent of initial fibre length (dp/dt)/IIT, where IIT is integrated isometric tension. 2. An increase in heart rate in control dogs was accompanied by a rise in both dp/dt and (dp/dt)/IIT confirming that the Bowditch staircase does exist in the intact ventricle. The regression line relating heart rate to (dp/dt)/IIT was significantly steeper than that relating heart rate to dp/dt because the reduction in left ventricular preload at high heart rate tends to attenuate the rise in dp/dt. 3. Reserpine, but not guanethidine pretreatment was accompanied by either a slight decrease or no change in (dp/dt)/IIT during pacing. 4. Acute elevation of (dp/dt)/IIT by either calcium or isoprenaline infusion in reserpine pretreated dogs did not restore the Bowditch effect. 5. Acute depression of (dp/dt)/IIT by propranolol and pentobarbitone was accompanied by a greater rise in (dp/dt)/IIT with pacing in control dogs and a rise rather than a fall in reserpine-pretreated dogs.

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Infestation in the dog by the paralysis tick, Ixodes holocyclus — 4. Cardiovascular effects

Ilkiw

1988

Aust Veterinary J

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To determine the extent and significance of changes in heart rate and rhythm noticed previously in dogs paralysed with Ixodes holocyclus, two studies were undertaken. In one the electrocardiogram was recorded at stages throughout the disease and the traces analysed for changes, while in the second a detailed study of the effect of Ixodes holocyclus on the cardiovascular system was undertaken. The electrocardiographic changes were extremely variable between stages and between dogs. Generally, if a dysrhythmia occurred in stages 1, 2 or 3 it tended to be sinus tachycardia, ventricular tachycardia or sinus arrest. In stage 4 sinus arrest, sinus bradycardia, or sinus or ventricular tachycardia were the prominent dysrhythmias, whereas in stage 5 sinus bradycardia predominated. Cardiovascular measurements indicated an increase in peripheral vascular resistance leading to a significant elevation in mean arterial pressure at all stages of the disease. Cardiac output was decreased significantly only at stage 2, although it was below the control measurements at all stages. Pulmonary arterial pressure was significantly elevated at stages 2, 3 and 4 due most probably to an increase in pulmonary vascular resistance. Myocardial contractility was not significantly changed throughout the disease. The changes observed in the electrocardiogram and the cardiovascular system in stages 1, 2 and 3 are unlikely to be due to hypoxia and could represent dysfunction of the autonomic nervous system. During stages 4 and 5 oxygen levels were below normal and the bradycardia seen terminally is almost certainly due to hypoxaemia.(ABSTRACT TRUNCATED AT 250 WORDS)

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A micromanometer for chronic implantation

Cited by 3 publications

References 3 publications

The Influence of Alterations in the Cardiac Loading Conditions on Indices of Myocardial Contractility in the Anaesthetized Dog

The Influence of Alterations in the Cardiac Loading Conditions on Indices of Myocardial Contractility in the Anaesthetized Dog

The effect of heart rate on indices of myocardial contractility in the dog

Infestation in the dog by the paralysis tick, Ixodes holocyclus — 4. Cardiovascular effects

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