Arterial pressure and heart period in the conscious rabbit: diurnal rhythm and influence of activity.

Mean-arterial pressure (MAP), heart period (HP) and the level of physical activity were measured in conscious rabbits and averaged over one-hour periods during 14 consecutive days. Serial autocorrelation coefficients and serial crosscorrelation coefficients were computed, to analyse periodicity. Measurements were started immediately after implantation of the cannula (group A, n = 11) or 10-46 days after implantation of the cannula (group B, n = 6).

Continuous 24-hour intra-arterial blood pressure recording in the conscious unrestrained rabbit.

A measuring system is described for the long-term continuous beat-to-beat measurement of mean aortic pressure and heart period (interval between beats) in the conscious unrestrained rabbit. Pressures and heart periods were collected in hourly histograms. The histograms were summed into day (0800-2000 h), night (2000-0800 h) and 24-hour histograms.

Cardiac function, fiber shortening, and dynamic geometry.

Many models for the study of the pump function of the heart emphasize the importance of cardiac geometry and detailed dimensional data. Because of the lack of accurate measuring techniques, approximate geometries such as shells of revolution have been applied. In this study, methods are presented that measure the dynamic geometry of the working, isolated canine heart by means of ultrasound-velocity tomography techniques.

Cardioplegia in the presence or absence of calcium.

The effect of the Bretschneider procedure of myocardial protection on the recovery of dog hearts in the postischemic phase after 90 min of aortic occlusion was studied. In one series of experiments, Bretschneider's calcium-free cardioplegic solution HTP was used; in a second series, 5 X 10(-5) M CaCl2 was added to this solution. The coronary system was perfused with cardioplegic solution (6 degrees C) for 6 min at the onset and for 1 min after 30 and 60 min of ischemic arrest.