ecause exogenous adenosine is known to induce hyperemia, it is used clinically for Tl imaging 1 and coronary flow or pressure measurement. 2,3 In Japan, ATP is used for this purpose instead of adenosine 4 because when administered intravenously, ATP is degraded to adenosine; therefore, the effects of adenosine and ATP are considered essentially the same. However, the direct effect of exogenous ATP might be manifiested through adenine nucleotide receptors (P2X, P2Y) in addition to its effect as adenosine through the adenosine receptors (A1, A2, A3).Adenosine A2 receptor stimulation relaxes smooth muscle via the stimulation of adenylyl cyclase activity. KATP channel opening via the A1 receptor stimulation may also relax vascular muscle. In cardiac muscle, A1 receptor stimulation has a negative inotropic effect: 5 it decreases adenylyl cyclase activity, decreases L-type Ca current (ICa), shortens the action potential duration 6 and inhibits contraction. 5 During continuous ATP injection, the direct effect of ATP should be considered in addition to the effect of its metabolite, adenosine. ATP induces vasodilation through the P2Y receptor, which is endothelium-dependent, and vasoconstriction through the P2X receptor. P2Y receptor stimulation inhibits cardiac muscle contraction through the inhibition of ICa. 7 Thus, there are many effects on cardiac and vascular smooth muscle from continuous ATP injection. Although the effect of adenosine on human hemodynamics is available from the literature, 2,8 the effect of continuous ATP injection is unknown and needs to be clarified.
MethodsThis study was performed in patients undergoing cardiac catheterization for re-evaluation after percutaneous coronary intervention (PCI) or coronary aorta bypass graft surgery (CABG) in Saitama Cardiovascular and Respiratory Center. Patients with acute coronary syndrome, severe heart valve disease, systemic hypotension, bronchial asthma, and any degree of atrioventricular (AV) block were excluded. Patients whose electrocardiogram (ECG) was not showing normal sinus rhythm or whose left ventricular (LV) ejection fraction was less than 40% were also excluded. Informed consent was obtained from each patient before the study.First, diagnostic coronary angiography was performed using the Jadkins' technique. If significant stenosis existed in a major coronary artery that was not protected by a bypass graft, the patient was withdrawn from the study. The total number of patients was 14 (13 male; 1 female; post PCI, 7; post CABG, 7; mean age, 65.2±2.5 years).Right atrial pressure (RAP), right ventricular pressure (RVP) and pulmonary capillary wedge pressure (PCWP) were measured and the cardiac index (CI) and stroke volume index (SVI) were calculated using a thermodilution technique. The catheter was then mounted in the pulmonary artery (PA) and aorta (Ao) for simultaneous monitoring of PA pressure (PAP) and Ao pressure (AoP) while ATP was injected from a peripheral vein at 0.16 mg · kg -1 · min -1 . After 4 or 5 min of equilibration, PAP and AoP became...
