Differential antagonism of cardiac actions of adenosine by theophylline.

OBJECTIVE: To determine the relative sensitivity of cardiac A1- and A2-adenosine receptor-mediated effects to antagonism by theophylline in man. METHODS: Baseline measurements of the A-H interval (A1-adenosine receptor-mediated effect) and coronary blood flow (A2-adenosine receptor-mediated effect) were made in 10 patients with angiographically normal coronary arteries. Adenosine was then administered as a continuous intravenous infusion followed by a rapid intravenous bolus, and measurements repeated. Theophylline (5 mg/kg i.v.) was then administered, and the adenosine infusion repeated. To corroborate the results found in man, the cardiac A1- and A2-adenosine receptor-mediated effects were measured in guinea pig isolated hearts exposed to increasing concentrations of adenosine, in the absence and presence of theophylline (60 microM). RESULTS: Compared to baseline, adenosine infusion and bolus caused significant prolongation of the A-H interval (109 +/- 41 vs. 116 +/- 44 vs. 168 +/- 57 ms, respectively), and increase in coronary blood flow (46 +/- 37 vs. 86 +/- 71 vs. 172 +/- 98 ml/min, respectively). Theophylline abolished the prolongation of the A-H interval during adenosine infusion and bolus (99 +/- 36 and 107 +/- 44 ms, respectively), yet had minimal effect on the increase in coronary blood flow (63 +/- 51 and 136 +/- 121 ml/min, respectively). In guinea pig isolated hearts, theophylline was shown to significantly antagonize the A2-adenosine receptor-mediated effects only when the concentrations of adenosine were < or = 1.0 microM. CONCLUSIONS: In man, theophylline completely antagonizes the A1-adenosine receptor-mediated prolongation of the A-H interval, but has minimal effect on the A2-receptor-mediated coronary vasodilation, particularly when adenosine concentrations exceed 1.0 microM.

Antegrade filling of an occluded right coronary artery via collaterals from a separate conus artery, a previously undescribed collateral pathway.

The conus artery is known to be a frequent supplier of collaterals to the LAD and distal marginal branches of the RCA. In this report we describe a patient with an ostial RCA occlusion who was found to have, during selective conus artery injection, excellent collaterals directly to the proximal RCA. This anatomy was initially mistaken for diffuse disease of the ostium and proximal portion of the RCA.

Echocardiographic assessment of wall motion in ST-segment alternans during coronary angioplasty.

ST alternans occurs in the setting of severe and extensive myocardial ischemia. In this particular case, ST alternans occurred well after the onset of ischemia-induced left ventricular dysfunction. There is no echocardiographic evidence of beat-to-beat variation in contractility to correspond to this ST-segment phenomenon. Further studies of left ventricular function during ST alternans in patients are needed to determine whether this finding applies to all patients with ischemic heart disease.

The relationship of A-B, field dependency, and emotional openness in paranoid and nonparanoid schizophrenics.

The relationship between A-B score, Field dependency (EFT), and paranoid-nonparanoid status in 24 male acute psychiatric inpatients was explored. It was hypothesized that paranoids would score as Bs and extreme field independents (conceptual orientation), while nonparanoids would score as As and field dependents (perceptual orientation). As predicted, nonparanoids were significantly more field dependent than paranoids and controls, but no difference was found between paranoids and controls. Contrary to our hypotheses, nonparanoids were significantly more B than paranoids and controls. The only difference between paranoids and controls was that paranoids were less feeling reactive. The results were interpreted in terms of the "normality= of the conceptually oriented paranoid S.

Lysis of intravascular thrombus prior to coronary stenting using the dispatch infusion catheter.

The presence of angiographic evidence of thrombus is generally thought to be a contraindication to coronary stent placement. This report describes four patients in whom angiographic thrombus was lysed using the Dispatch infusion catheter prior to coronary stenting. Urokinase was infused via the Dispatch catheter with resolution of angiographic evidence of thrombus in all cases. No complications were encountered using this technique, and all patients had excellent angiographic results after stenting. We conclude that lysis of intracoronary thrombus using the Dispatch infusion catheter is feasible and appears safe in this small study. Further trials are needed to determine if this technique reduces the acute stent thrombosis rate compared to other techniques for stent deployment in the presence of angiographic evidence of thrombus.

Selective attenuation by N-0861 (N6-endonorboran-2-yl-9-methyladenine) of cardiac A1 adenosine receptor-mediated effects in humans.

BACKGROUND: To determine the adenosine receptor subtype selectivity of the novel antagonist N-0861, the A1 and A2 receptor-mediated cardiac effects of adenosine were investigated in 13 patients during continuous intravenous infusion and boluses of adenosine before and after intravenous infusion of N-0861. METHODS AND RESULTS: Measurements of the the atria-to-His (A-H) interval, chest pain severity, and coronary blood flow velocity were made before and after low-dose (69 microg x kg(-1) x min(-1)) intravenous infusion and bolus (2.5 mg) adenosine. Two doses of N-0861 were infused intravenously, and the adenosine protocol was repeated. N-0861 0.25 mg/kg abolished the negative dromotropic effect (A-H interval prolongation) and chest discomfort experienced during infusion of adenosine and attenuated discomfort observed during the boluses of adenosine; however, the increase in coronary blood flow velocity was not significantly affected. CONCLUSIONS: These actions of N-0861 support the concept that the negative dromotropic effect and anginalike pain caused by adenosine are A1 adenosine receptor-mediated, whereas the increase in coronary blood flow velocity is due to activation of A2 adenosine receptors. N-0861 appears to be an effective and selective A1 adenosine receptor antagonist in humans.

Improved detection of healed myocardial infarction by Fourier amplitude and phase imaging in two projections: validation with MRI.

Biplane Fourier amplitude and phase images from radionuclide ventriculograms were analyzed for the presence of regional wall motion abnormalities in 25 patients who had a total of 33 healed myocardial infarctions (nonviable scar tissue) documented by contrast ventriculography and ECG. This indirect evidence was validated by MRI, which permits direct visualization of healed myocardial infarction. The use of amplitude and phase images in both projections resulted in the detection of more healed myocardial infarctions (91%) than did the use of conventional radionuclide ventriculography with left anterior oblique images alone (67%), because inferior wall infarcts are more readily visualized in the left posterior oblique projection.