Effects of inotropic and chronotropic stimuli on acute myocardial ischemic injury. I. Studies with dobutamine in the anesthetized dog.

Abstract

SUMMARY The effect of i.v. dobutamine on acute myocardial ischemic injury was assessed in 22 anesthetized dogs subjected to serial 10-minute occlusions of the left anterior descending coronary artery. The severity of ischemic injury was determined by mass spectrometric measurement of the increase in intramural carbon dioxide tension (zAPmco2) in the ischemic zone. In the nine protocol 1 dogs, dobutamine, 20 ,ug/kg/min, infused between the control and final occlusion, significantly increased both heart rate (HR) and left ventricular (LV) dP/dt; APmco2 was significantly higher during the dobutamine infusion than during control occlusion (76 ± 21 vs 56 + 13 mm Hg,p < 0.01). The nine protocol 2 dogs were atrially paced at a HR of 20-30 beats/min above baseline values during the control occlusion and received dobutamine (12.6 ± 7.8 ugg/kg/min) at doses necessary to attain an equal HR (mean 149-154 beats/min) during the last occlusion.Although LV dP/dt was higher after dobutamine, APmco2 was similar during the two occlusions. Protocol 3 dogs (n = 4) received lower doses of dobutamine (5.6 ± 3.2 Ag/kg/min) to produce an increase in LV dP/dt, but not in HR compared with baseline values; APmco2 was similar during control and dobutamine occlusions. There were no major changes in arterial or left atrial pressures. Rate-pressure product, an indirect measurement of myocardial oxygen consumption, was increased only by the higher doses of dobutamine in protocol 1.Thus, inotropic stimulation with dobutamine during coronary occlusion does not cause important augmentation of acute myocardial ischemic injury in the nonfailing heart unless HR is increased simultaneously.THE SEVERITY of evolving acute myocardial ischemic injury can be influenced by interventions performed before or shortly after experimental coronary artery occlusion.' Pharmacologic agents and hemodynamic alterations can affect ischemic injury. Although most reports deal with interventions that lessen myocardial ischemic injury, certain interventions can intensify ischemia or increase infarct size.2 B Even though the role of specific therapy to protect ischemic myocardium in the patient with evolving acute myocardial infarction is not clear, it is widely held that interventions that augment ischemic injury in experimental animals should be avoided in patients with myocardial ischemic syndromes.0" 11 Most deleterious influences on evolving ischemic damage are thought to be mediated by further alterations in the relationship between myocardial oxygen supply and demand in ischemic tissue. An creasing heart rate, contractile state, or left ventricular (LV) wall tension.'1 Because many studies that showed augmentation of ischemic injury used interventions that simultaneously alter several determinants of myocardial oxygen demand or supply or both, we investigated whether deleterious effects on ischemic damage also result from more selective alterations in these hemodynamic variables.Methods Twenty-two mongrel dogs that weighed 17-44 kg were anesthetized with i.v. pen...

Dobutamine Cardiovascular Magnetic Resonance for the Detection of Myocardial Ischemia With the Use of Myocardial Tagging

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Dobutamine Stress Echocardiography for Detecting Coronary Artery Disease

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