Relationship between shortening load, contractility, and myocardial energetics in intact dog.
A canine model was developed to estimate left ventricular wall stress, volumes, contractility, and high-energy phosphate metabolites without the need for major surgery. A percutaneously inserted catheter-tip manometer was used to record high-fidelity left ventricular pressure while gradient echo cinemagnetic resonance (cine-MR) imaging alternated with in vivo 31P-nuclear magnetic resonance (NMR) spectroscopy during pharmacological maneuvers to increase cardiac work. Left ventricular circumferential wall stress, volumes, maximum rate of pressure development (dP/dtmax), and the ratio of phosphocreatine (PCr) to gamma-ATP (PCr/gamma-ATP) were recorded sequentially during control 1, dobutamine infusion, control 2, angiotensin infusion, and control 3 in five anesthetized, closed-chest dogs. PCr/gamma-ATP did not change significantly during controls 1-3, angiotensin, and dobutamine infusion. Left ventricular peak positive dP/dt (+dP/dtmax) increased significantly during dobutamine (3,338 +/- 831 mmHg/s, P < 0.001) but was unchanged during angiotensin (1,818 +/- 317 mmHg/s) and controls 1-3 (1,915 +/- 434 vs. 1,808 +/- 478 vs. 1,859 +/- 414 mmHg/s). However, dobutamine decreased the total systolic stress integral (area under the wall stress-time relationship) and end-diastolic and end-systolic volumes, whereas angiotensin increased these parameters compared with control conditions. The unchanged PCr/gamma-ATP is in accord with the results from other open-chest surface coil 31P-NMR experiments in the normal heart. Our assessment of left ventricular functional parameters provides new information that complements these more invasive studies in which heart rate-pressure product was measured during increases in cardiac work.(ABSTRACT TRUNCATED AT 250 WORDS)
Dell'Italia
L J
LJ
Department of Medicine, University of Alabama, Birmingham 35294.
Evanochko
W T
WT
Blackwell
G G
GG
Pearce
D J
DJ
Pohost
G M
GM
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D001810:Blood Volume; D004280:Dobutamine / Q000494:pharmacology; D004285:Dogs; D004734:Energy Metabolism; D006321:Heart / Q000502:physiology*; D006439:Hemodynamics / Q000187:drug effects; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D009040:Motion Pictures; D009200:Myocardial Contraction; D009206:Myocardium / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism; D010758:Phosphorus; D013314:Stress, Mechanical
D010710:Phosphates; D000804:Angiotensin II; D010758:Phosphorus; D004280:Dobutamine