Main content area

Mechanisms of increased right and left ventricular oxygen uptake during inotropic stimulation

Crystal, George J., Silver, Jeffrey M., Salem, M. Ramez
Life sciences 2013 v.93 no.2-3 pp. 59-63
blood flow, dogs, drugs, equations, oxygen, vasodilation
AIMS: Few studies have investigated oxygen supply/demand relations in right ventricle (RV). The current study compared changes in myocardial oxygen uptake (MVO₂) and its determinants, myocardial blood flow (MBF) and oxygen extraction (EO₂), in RV and left ventricle (LV) during stimulation with inotropic drugs. MAIN METHODS: Twenty-one anesthetized dogs were studied. MBF was measured with radioactive microspheres. A-VO₂ difference was determined separately for RV and LV, and used to calculate MVO₂ (Fick equation) and EO₂. Responses to iv. infusions of isoproterenol (0.1μg/kg/min), dobutamine (5μg/kg/min), and amrinone (1mg/kg+10μg/kg/min) were assessed. KEY FINDINGS: Baseline MVO₂ in RV was 50–60% of that in LV. The inotropes increased MVO₂ in both RV and LV (range 32–63%; P<0.05). With isoproterenol, the increased MVO₂ in the RV was due to increases in both MBF and EO₂, whereas in LV it was due only to increases in MBF. With dobutamine and amrinone, the increased MVO₂ in RV was due to increased MBF while EO₂ was constant (dobutamine) or decreased (amrinone), and that in the LV was due to increased MBF while EO₂ decreased. SIGNIFICANCE: RV possesses EO₂ reserve that contributed to increased MVO₂ during isoproterenol infusion, whereas LV depended on increased MBF alone. Because dobutamine and amrinone caused direct coronary vasodilation, i.e., “luxuriant perfusion,” it was not necessary to recruit the EO₂ reserve. Thus, it remained available to meet further increases in MVO₂ or to maintain MVO₂ in the face of reductions in MBF.