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Biomedical subjects

P Rigo

Publications and source records attributed to P Rigo.

At least 91 records · Page 5Linked to original sources
PubMed1986

Myocardial blood flow and glucose uptake after myocardial infarction.

Position emission tomography can picture the distribution of flow tracers as well as of metabolic substrates or analogs. Studies of the distribution of these tracers allow to infer information about regional myocardial clearance (flow X extraction) and substrate utilization. In a study of 32 patients after myocardial infarction, we have contrasted flow and substrate utilization to demonstrate ischemic but viable myocardium in the arterial territory of the infarct in a number of patients also specially after fibrinolytic reperfusion. Restoration of blood flow to the ischemic but viable myocardium through coronary bypass or dilatation improves flow from 56.3% to 84.2% of control and restores substrate utilization. In another group of 32 patients studied with the Strontium-82/Rubidium-82 generator, we have demonstrated perfusion changes both in the myocardial infarct area and at a distance. These changes predominate in patients with multiple vessel disease. Combined PET studies of flow and substrate utilization are new tools to study early intervention after myocardial infarction and to document the benefits of revascularization.

Aged↗
PubMed1986

The utilization of Tc-99m-TBI as a myocardial perfusion agent in exercise studies: comparison with Tl-201 thallous chloride and examination of its biodistribution in humans.

Twenty-four patients were studied with both 201Tl-thallous chloride and 99mTc-TBI scintigraphy following exercise. Comparison of the two agents in detecting segmental myocardial ischemia and scar was made in 18 patients with evidence of coronary artery disease on 201Tl-thallous chloride scintigraphy. Agreement between the two studies was observed in 77% (125 of 162) of left ventricular segments, suggesting that 99mTc-TBI can be used as a myocardial perfusion agent. Limitations were related to early high background activity from lungs and liver. The high lung activity and early myocardial redistribution within the 1st hour contributed to the failure of 99mTc-TBI to detect 16 segmental defects seen in the immediate post-exercise thallous chloride scan. Persistently high liver activity additionally affected accurate interpretation in the left ventricular segments close to the diaphragm. Improvement in the accuracy of 99mTc-TBI stress studies might be achieved with tomographic imaging to reduce the problem of background activity or by the development of 99mTc-labeled isonitrile analogues with rapid lung and liver clearance.

Adult↗
PubMed1986

Complementary role of thallium-201 scintigraphy to predischarge exercise electrocardiography for patients stratification after a first myocardial infarction.

The value of a predischarge exercise test combined with thallium-201 myocardial scintigraphy in detecting patients with severe multivessel disease (MVD) was studied in 58 consecutive patients discharged after a first acute myocardial infarction. Twelve electrocardiographic, clinical and scintigraphic variables were analysed. Angiography at one month revealed MVD (greater than 70% narrowing in vessels unrelated to infarction) in 26 patients (45%). ST segment depression of 1mm or greater, thallium defects in multiple vascular distributions (MVTL), and reversible thallium defects in a vascular distribution different from the infarct related vessel predicted patients at risk for MVD (predictive value respectively of 68%, 65% and 75%). The other variables were not significantly associated with the presence of MVD. Only ST segment depression and thallium defects in multiple vascular distributions emerged as independent predictors of MVD. Their combination yielded a 77% sensitivity and a 59% specificity for MVD. Combination of thallium imaging with the predischarge exercise ECG significantly improved the stratification provided by the exercise test alone (P less than 0.05). A positive thallium scan (MVTl defects) associated with a positive ECG (ST depression) carried a risk for MVD of 80% in the population studied. When both tests were negative, MVD was infrequent (risk 22%). Because improvement in the stratification of patients is not as clear as expected from studies performed at a later stage, it appears that exercise thallium scintigraphy at a submaximal level one or two weeks after infarction does not provide optimal information. Predischarge exercise thallium-201 scintigraphy, however, is superior to an exercise tolerance test alone in separating patients into those with high and low risk of MVD.

Electrocardiography↗
PubMed1985

Evaluation of the effects of molsidomine by cardiac equilibrium blood pool scintigraphy.

We have used equilibrium gated blood pool scintigraphy to evaluate the hemodynamic effects and duration of action of molsidomine, a new peripheral vasodilator antianginal drug, after sublingual administration (4 mg) in five patients with heart failure. The following parameters were studied at rest and 10, 60, and 240 minutes after drug administration: left and right ventricular ejection fractions, end-diastolic and end-systolic volumes, stroke volume, heart rate, and cardiac index. Systolic and diastolic blood pressures were determined by cuff measurement. Statistically significant (p less than 0.05) changes were observed after 10 minutes for left ventricular ejection fraction (+26.2%), left and right end-diastolic volume (-12.4% and -15.2%), left ventricular end-systolic volume (-15%), and cardiac index (+7.9%); after 60 minutes for left ventricular ejection fraction (+49%), left ventricular systolic volume (+30.5%), cardiac index (+29.7%), systolic blood pressure (-7.9%), and right ventricular end-diastolic volume (-14.3%); and after 240 minutes for cardiac index (+23.9%), systolic blood pressure (-6.3%), and right ventricular ejection fraction (+23.1%). No changes in heart rate were observed. No patient experienced any side effect. We conclude that the hemodynamic improvement observed with molsidomine can be prolonged and results both from preload and afterload reduction.

Adult↗
PubMed1984

Effect of ticlopidine on saphenous vein bypass patency rates: a double-blind study.

The effects of ticlopidine, a new antiplatelet agent, on graft patency rate was investigated in a group of 150 consecutive patients undergoing aortocoronary bypass graft procedures. In a double-blind study, two groups of 75 patients each received ticlopidine (250 mg twice daily) or a placebo during a three-month period. Graft patency was evaluated by repeat angiography in 38 patients and by rest and stress myocardial scintigraphy in 93. Combined angiographic and scintigraphic analysis was performed in 36 patients. The biological effects of ticlopidine on platelet activity were assessed by bleeding time and appropriate ex vivo tests. Graft patency was evaluated in 131 patients (87%). Evaluation was performed at the end of the three-month therapy period in 77 patients (Groups T1 [ticlopidine] and P1 [placebo]) and five months later in 54 patients. The total graft attrition rate was 10.1% in Group T1 compared with 20.3% in Group P1 (p less than 0.1). Excluding patients with discordant biological data, the attrition rate was 7.1% for Group T1 compared with 21.8% for Group P1 (p less than 0.02). There was no difference between the subgroups evaluated five months after the end of therapy. Ticlopidine appears to be an effective means of protecting graft patency as long as the biological effects of the drug are present. This protective effect disappears when the drug is discontinued, which suggests that ticlopidine should be prescribed for a longer period, at least for the first year after operation.

Coronary Artery Bypass↗
PubMed1984

Effects of methylprednisolone on the Fc-receptor function of human reticuloendothelial system in vivo.

To determine whether the Fc-receptor function of reticuloendothelial system (RES) is modified by corticosteroid administration, we studied the spleen to liver uptake ratios of autologous, 99Tc-labelled heat-damaged or IgG-coated erythrocytes, injected intravenously into 10 normal volunteers, 4 h after receiving a single dose of 32 mg of methylprednisolone by mouth. In standard conditions, quantitative scans indicated that the spleen to liver uptake ratios, calculated per unit area 40 min after the injection of labelled erythrocytes, were 13.4 +/- 0.6 and 31.2 +/- 1.5 (mean values +/- -SEM), for the heat-damaged (n = 7) and IgG-coated red cells (n = 5) respectively. Four hours after corticosteroid administration, the spleen to liver uptake ratios were significantly reduced in five of ten volunteers. Abnormal ratios correlated with the Fc-receptor function of monocytes measured in vitro using IgG-coated erythrocytes. Indeed, 2-6 h after methylprednisolone was given, the Fc-receptor binding activity of monocytes isolated from the same five subjects was reduced by at least 50%, spontaneously returning to a rather normal value 4-6 h later. The C3-receptor binding activity of these monocytes remained normal, after otherwise identical experimental conditions. These results show a transient, specific impairment of the Fc-receptor function of RES after methylprednisolone administration, and may therefore explain, in part, the infectious complications occurring in some patients treated by corticosteroids.

Adult↗
PubMed1983

Radiocardiographic evaluation of left ventricular function after inhalation of C15O2.

Inhalation of C15O2 delivers a bolus of labelled water into the pulmonary veins and the left atrium; analysis of the left ventricular curve provides an easy method for the evaluation of left ventricular function. the patient was seated before six collimated probes positioned toward the lungs. An additional probe was directed toward the heart in a modified 15 to 20 degrees left anterior oblique projection. One to two mCi C15O2 was administered per study. The left ventricular curve was analysed and the ejection fraction was calculated using a new method. The background was first calculated for the cycle with the largest diastolic counts using characteristic points of the curve before and after transit of the indicator through the left ventricle. For the other cycles, the background was considered to be a constant fraction of the end-diastolic counts. The left ventricular ejection fraction was obtained for each cycle after corresponding background subtraction as the ratio of diastolic activity minus systolic activity over diastolic activity. The ejection fraction thus determined in 20 patients was highly reproducible from beat to beat and from study to study in the same patient (r = 0.97 and 0.96). It corresponded closely to the ejection fraction determined using a camera-computer system (r = 0.92). We conclude that C15O2 inhalation is an easy, rapid, reproducible and attractive method to assess left ventricular function.

Adult↗
PubMed1983

Radioisotopic studies during exercise testing: how valuable?

Myocardial imaging and exercise radionuclide angiography have proven useful in the detection of exercise-induced regional dysfunction. EF monitoring is, however, inadequate to detect deterioration of cardiac performances with complex changes in the ventricular loading conditions. Measurement of absolute volumes and especially of end-systolic volume by a count-derived technique will further enhance the value of this method when attenuation correction can be consistently performed. Non-invasive estimates of end-systolic indices could then be obtained. Concomitant evaluation of right ventricular ejection and function provides data on ventricular interdependence and allows quantification of regurgitant lesions and of their changes with exercise. Combined evaluation of these parameters will allow a better definition of the changes occurring in valvular heart disease. Radioisotopic studies also permit evaluation of stress-induced changes in pulmonary blood volume and in the pulmonary distribution of thallium. These parameters, although incompletely studied, could provide further evidence of transient LV dysfunction and deserve further study.

Aortic Valve Insufficiency↗
PubMed1983

Right ventricular myocardial infarction diagnosed by 99 m technetium pyrophosphate scintigraphy: clinical course and follow-up.

Out of 178 consecutive patients with acute inferior wall myocardial infarction submitted to technetium-99 m pyrophosphate scintigraphy, 49 (27.5%) were found to have concomitant right ventricular infarction. Gated blood pool scans showed right ventricular abnormalities in 21 out of 26 patients who were submitted to this investigation (right ventricular asynergy: 16 cases; right ventricular dilatation: eight cases; decreased right ventricular ejection fraction: 16 cases). Complications were common in the acute stage. Shock was noted in 19 cases (eight related to bradycardia, three related to relative hypovolaemia and eight instances of true cardiogenic shock). Atrial fibrillation (seven patients), ventricular fibrillation (eight patients) and severe atrioventricular conduction disorders (13 patients) were also frequent. In spite of this, the in-hospital mortality was low: three deaths occurred (6.1%), one from heart failure, two others from posterior septal rupture. All patients were followed up for one year or more. Six additional deaths were noted (three from left cardiac failure, two from recurrent anterior wall infarction and one from massive pulmonary embolism). Clinical assessment, haemodynamic measurements and gated blood pool scans showed significant improvement of right ventricular function with return to normal in those cases with small right ventricular infarcts as judged from technetium-99 m pyrophosphate scintigraphy. In spite of the complications seen in the initial period, patients with a right ventricular infarction have a good overall prognosis and the long-term outcome, primarily determined by the left-sided lesions, is often favourable.

Adult↗
PubMed1983

Evaluation of right-ventricular function by gated blood-pool scintigraphy.

The purpose of this paper is to review several modalities that can be helpful in evaluating right-ventricular (RV) function. We have investigated the role of functional imaging in analysis of regional RV function and in selection of RV region of interest (ROI). From this we have derived a method to determine the RV ejection fraction using a single RV ROI. The analysis is performed in a modified LAO projection; Fourier phase and amplitude functional images are used to help trace the ROI and study wall-motion abnormalities. This method is compared with the double-ROI technique of Maddahi. Values of RV ejection fraction obtained with one ROI correlate well with those obtained using two ROIs (r = 0.95). The regression equation is used to correct for the single-ROI underestimation. The inter- and intra-observer variability is better for the single- than for the double-ROI technique. RV function studies are performed in normal volunteers and in patients with a variety of cardiac disorders. Changes in RV ejection fraction caused either by direct alteration of RV function or by altered loading conditions are documented. Analysis of regional RV function demonstrates RV free wall as well as septal perturbations, further characterizing the extent of dysfunction and providing some etiologic information. We conclude that: 1. RV ejection fraction can be measured by the use of an adequate single diastolic ROI; and 2. A simple equilibrium gated technique can provide detailed information about global and regional RV function that should be systematically added to the analysis of the parameters for left-ventricular function.

Adolescent↗
PubMed1982

Measurement of left-to-right shunts by gated radionuclide angiography: concise communication.

Gated cardiac blood-pool scans allow comparison of left- and right-ventricular stroke volume. We have applied these measurements to the quantification of left-to-right shunts (QP/QS) in nine patients with atrial septal defects, one patients with partial anomalous pulmonary venous return, four patients with ventricular septal defects, and two patients with patent ductus arteriosus. None of these patients had combined lesions. QP/QS was measured as the right-ventricular (RV) stroke counts divided by the left-ventricular (LV) stroke counts and as the LV stroke counts divided by the RV stroke counts in patients with RV and LV diastolic volume overload respectively. All patients had also QP/QS measurements by oximetry and first-pass radionuclide angiography. The stroke-count measurements indicated the overloaded ventricle in all patients. QP/QS determined by equilibrium gated studies correlated well with those obtained by oximetry (r = 0.79). Reproducibility of the equilibrium measurements was good. We conclude that gated cardiac blood-pool scans can measure left-to-right shunts and can distinguish between shunts with RV and LV volume overload.

Adolescent↗
PubMed1981

Stress thallium-201 myocardial scintigraphy for the detection of individual coronary arterial lesions in patients with and without previous myocardial infarction.

The value of stress thallium-201 scintigraphy for detecting individual coronary arterial stenoses was analyzed in 141 patients with angiographically proved coronary artery disease, 101 with and 40 without a previous myocardial infarction. In patients without infarction, the sensitivity for detecting greater than 50 percent narrowing in the left anterior descending, the right and the left circumflex coronary artery was 66, 53 and 24 percent, respectively. In those with a previous infarction, the sensitivity for demonstrating disease in the artery corresponding to the site of infarction was 100 percent for the left anterior descending, 79 percent for the right and 63 percent for the left circumflex coronary artery. In patients with a prior anterior infarction, concomitant right or left circumflex coronary arterial lesions were detected in only 1 of 12 cases, whereas in those with previous inferior or inferolateral infarction, the sensitivity for left anterior descending coronary artery disease was 69 percent. Because of the reasonably high sensitivity for detecting left anterior descending arterial disease, irrespective of the presence and location of previous infarction, myocardial scintigraphy was useful in identifying multivessel disease in patients with a previous inferior infarction. However, because of its relative insensitivity for right or left circumflex coronary artery disease, scintigraphy proved to be a poor predictor of multivessel disease in patients with a prior anterior infarction and in patients without previous myocardial infarction.

Adult↗