End-systolic pressure-length relations during changes in regional contractile state.
End-systolic pressure-length relationship (ESPLR) was examined in the heterogenously contracting heart in open-chest dogs. Regional length was measured sonomicrometrically in the areas of both the left circumflex coronary artery (LCX) and left anterior descending coronary artery (LAD). ESPLR was linear during a transient reduction in arterial pressure following occlusion of the inferior caval vein (IVC). In group 1 (12 dogs), saline as a control condition (Cont) and isoproterenol (Iso, 0.05 microgram/min) to enhance the regional contractile state were infused into the LCX. Percent shortening in the LCX area increased from 13 to 16% (P less than 0.01) in Iso. The slope (Ees) of ESPLR increased from 57 to 71 mmHg/mm (P less than 0.01) in Iso. The extrapolated X-axis intercept (Lo) of ESPLR was unchanged. In the LAD area, Ees and Lo remained constant. In group 2 (13 dogs), lidocaine (1 mg/min, Lid 1; 5 mg/min, Lid 5) was infused into the LCX to induce mild and severe hypokinesis, respectively. Percent shortening in the LCX area was reduced from 14 to 8% (P less than 0.01 vs. Cont) in Lid 1 and 5% (P less than 0.01 vs. Cont, P less than 0.05 vs. Lid 1) in Lid 5. Ees tended to decrease in Lid 1 but to increase in Lid 5 (statistically not significant).(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D001794:Blood Pressure; D003864:Depression, Chemical; D004285:Dogs; D006339:Heart Rate; D007545:Isoproterenol / Q000494:pharmacology; D008012:Lidocaine / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects; D011312:Pressure; D013268:Stimulation, Chemical
D008012:Lidocaine; D007545:Isoproterenol