Splenectomy alters blood pressure response to incremental treadmill exercise in horses

Six intact (IN) and five splenectomized (SP) mares were subjected to an incremental exercise test to examine the effects of splenectomy on blood pressure responses during exercise. During the test the horses ran up a 6 degree grade on a treadmill set at an initial speed of 4 m/s. Speed was increased 1 m/s every 1 min until heart rate (HR) reached a plateau. Hemodynamic data were collected continuously and analyzed for the last 18 s of the 4, 5, 6, and 7 m/s steps of the exercise test. There were no differences (P > 0.05) between the groups for resting means for any parameter measured in the study. HR increased (P < 0.05) in both groups of horses during exercise with significantly greater HR in the SP horses during the first two steps of the test. There were no differences (P > 0.05) in maximal HR between the groups. Right atrial pressure (RAP) did not change during exercise in the SP horses; however, it did increase 20 mmHg (493%, P < 0.05) in the IN horses. Right ventricular pressure (RVP) increased (P < 0.05) during exercise with no differences (P > 0.05) between the groups. Right ventricular maximum change in pressure over time increased (P < 0.05) in a similar fashion in both groups of animals. Mean arterial pressure (MAP) increased 29 mmHg (30%, P < 0.05) in SP horses, reaching a plateau by the 5 m/s step of the test.(ABSTRACT TRUNCATED AT 250 WORDS)