No abstract

No abstract

SUMMARY1. The effect of increased aortic pressure on the inotropic state of the left ventricle was studied in isolated cat hearts, perfused with bovine red cells in Tyrode solution, ejecting into a hydraulic model with the same input impedance as that of the cat aorta.2. Inotropic state was assessed at a controlled left ventricular enddiastolic pressure by interpolating single isovolumic beats by means of an occluder in the aortic cannula.3. When such isovolumic beats during periods of raised aortic pressure were compared with those during control periods, the difference in peak isovolumic pressure ranged from -03 to + 0 5 kPa indicating differences in inotropic state which were small and inconsistent in direction.4. The maximum rate of rise of left ventricular pressure (dPldtmax ) of ejecting beats was little affected by a rise of aortic pressure and the direction of changes was inconsistent.5. The effect of increased aortic pressure was studied in intact dogs after cardiac denervation; left ventricular end-diastolic pressure was uncontrolled and therefore rose to a higher steady level.6. No consistent change of dP/dtmax was found during the period of increased aortic pressure.7. All flow and pressure variables remained steady during the period of increased aortic pressure after the higher level of left ventricular enddiastolic pressure had been established.8. These results demonstrate that neither the positive inotropic effect nor the negative inotropic effect of increased load dominates in these * Drs Elzinga and Noble are supported by a European Collaborative Grant of the Wellcome Trust.

To live to a ripe old age, untroubled by health problems, physical or mental, is an almost universal aspiration. But most people are not so lucky and will likely be in care homes for their final years, with varying levels of disease, disability and dementia. Kinley et al [1] maintain that over a fifth of the population of developed countries die in care homes. Moreover, the financial cost of this end of life care, which is the focus of this paper, can be daunting and require much planning [2]. It was reported in 2017 that, in the UK, care home costs are rising up to twice as fast as inflation [3]. Consequently the question arises about the long term affordability of such care to those having to fund it, a question that ever more people both nationally and globally are having to confront.

Normal and cardiac denervated dogs, with an electromagnetic aortic flowprobe implanted at least 14 days before the experiments, ran at different speeds on a 25% graded treadmill. The experiments were carried out before and after blockade of betareceptors in the heart by PO administration of 125 mg X kg-1 practolol per day. Changes in stroke volume, heart rate, and cardiac output were measured. After beta-adrenergic blockade, only two of the seven dogs with denervated hearts were prepared to run at a limited number of speeds. Time constants of the cardiac output changes at the onset of exercise were significantly different (P less than 0.001) for the normal (11.5 +/- 0.7 s, mean +/- SEM) and the denervated dogs (29.5 +/- 1.1 s), but in normal dogs did not change with practolol (11.8 +/- 0.8 s). The steady state relationship between cardiac output (CO) and work per unit time performed on the treadmill (P) was for normal dogs: CO = 156 + 1.55P, for normal dogs after practolol treatment: CO = 156 + 0.43P (slope significantly different, P less than 0.05), and for dogs with denervated hearts: CO = 121 + 2.06P (not significantly different from normal dogs). It was concluded that changes in the venous or arterial system alone are not sufficient to increase cardiac output appreciably during exercise. The magnitude of the cardiac output increase depends more on the presence of intact beta-receptors than on the presence of intact cardiac nerves.(ABSTRACT TRUNCATED AT 250 WORDS)