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Biomedical subjects

O Parodi

Publications and source records attributed to O Parodi.

At least 73 records · Page 4Linked to original sources
PubMed1993

Non-invasive assessment of residual viability in post-myocardial infarction patients: role of nuclear techniques.

The failure of non-imaging techniques in identifying viable segments has favoured the clinical application of nuclear imaging. The main pathways that support radionuclide imaging are cell membrane integrity, persistence of intermediary metabolism and demonstration of a residual coronary reserve. Thallium-201 reinjection or rest protocols allow the identification of viable myocardium in most of patients with wall motion abnormalities and appear to be the most diffuse, low-cost and available method to detect viable myocardium. More complex approaches use positron emission tomography and matched flow/metabolic information. Flow/metabolic "mismatch" usually identifies most of hypoperfused regions that show post-operative improvement of regional wall motion. The last promising approach is represented by the demonstration of a maintained regional coronary reserve in dyssynergic areas. 99mTc-microspheres (or Teboroxime in the future) can be successfully used for this purpose. The clinical application of radionuclides appears to be one of the principal imaging tools able to identify residual viability.

Coronary Vessels↗
PubMed1993

Ischemia on effort is not a determinant of stunned myocardium in man: a radioisotopic study based on quantitative evaluation of ventricular dynamics.

To assess whether myocardial stunning occurs following brief episodes of effort ischemia, ventricular function was assessed by radionuclide angiography in 29 patients with coronary artery disease. No patient had evidence of previous myocardial infarction. Patients were divided into two groups according to presence of single (14 patients, Group 1) or multi-vessel (15 patients, Group 2) coronary artery disease. Equilibrium radionuclide angiocardiography was performed in the left anterior oblique projection by a small field-of-view gamma-camera. Acquisition were performed at baseline, at peak exercise, then again at 1 and 5 minutes of the recovery phase. For each acquisition, ejection fraction, peak filling rate and wall motion index were measured and compared. No difference in baseline and stress measurements was found between Group 1 and Group 2, except for the wall motion index that was more impaired during ischemia in patients of Group 2. Global and regional indexes of ventricular function did not show significant differences also in the two recovery periods when compared to the relative baseline values. Transient ischemia caused by an increase of oxygen demand did not reproduce the phenomenon of systolic and diastolic stunning observed in animal experiments, although in all patients the ischemia was of sufficient duration and severity to induce transient ventricular dysfunction.

Adult↗
PubMed1992

Identification of viable myocardium by dipyridamole-induced improvement in regional left ventricular function assessed by echocardiography in myocardial infarction and comparison with thallium scintigraphy at rest.

In patients with coronary artery disease and left ventricular impairment, the distinction between ventricular dysfunction due to myocardial fibrosis and postischemic, viable, although dys-synergic, myocardium has important clinical implications. Experimental studies have shown that dipyridamole can increase myocardial function in stunned segments, outlining a potential role of dipyridamole-induced functional recovery as an ultrasonic marker of myocardial viability. The aim of this study was to assess whether the increase of regional left ventricular function early during dipyridamole infusion in basally asynergic segments could identify viable myocardium recognized by rest injected, delayed (greater than 14 hours from tracer injection) thallium and (in a subset of patients) late functional recovery evaluated by a follow-up echocardiogram at rest. Twenty-two patients with angiographically documented coronary artery disease and regional dysfunction in resting conditions (average left ventricular ejection fraction 43 +/- 8%) were studied by echocardiography. All patients underwent a dipyridamole-echocardiographic test (up to 0.84 mg/kg over 10 minutes) and a delayed planar thallium study. A 13-segment model was used for both techniques. A score index ranging from 1 (normokinesia) to 4 (dyskinesia) was used for echocardiography. Thallium-201 activity was expressed in each segment as the percentage of maximal activity in the corresponding view. After dipyridamole, the wall motion score was assigned to each segment in resting conditions and at peak hyperkinesia before possible mechanical signs of ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Angiography↗
PubMed1992

Prediction of reversible perfusion defects by quantitative analysis of post-exercise electrocardiogram-gated acquisition of technetium-99m 2-methoxyisobutylisonitrile myocardial perfusion scintigraphy.

The aim of this study was to assess the reliability of the quantitative analysis of regional wall thickening with electrocardiographic-gated technetium-99m 2-methoxyisobutylisonitrile (SESTAMIBI) in predicting the reversibility of stress-induced perfusion defects. The assumption was that a preserved resting wall thickening in a segment with stress-induced perfusion defect would predict normal resting perfusion. Twenty-five patients with suspected coronary artery disease underwent planar stress-rest SESTAMIBI scintigraphy. The wall thickening was quantitatively evaluated as percentage increase in counts from diastole to systole; a ratio defined as the wall thickening index (WTI) between patient and normal profile (mean - 2 SD) below 1 was considered abnormal. Improvement of the perfusion pattern at rest was observed in 76% (54/71) of segments with a stress-induced perfusion defect; 90% of these segments had a (WTI) greater than 0.8. Five segments (9%) showed fixed perfusion defects despite a WTI value greater than 0.8. In conclusion, quantitative analysis of regional wall thickening by electrocardiographic-gated SESTAMIBI identifies segments with reversible perfusion defects; this may overcome the need for studies at rest and may direct the detection of hypoperfused but viable myocardium.

Coronary Disease↗
PubMed1992

The clinical usefulness of electrocardiogram-gated Tc-99m methoxy-isobutyl-isonitrile images in the detection of basal wall motion abnormalities and reversibility of stress induced perfusion defects.

Technetium-99m methoxy-isobutyl-isonitrile (SESTAMIBI) has been recently introduced to trace regional myocardial perfusion. Beyond blood flow distribution, a quantitative index of regional myocardial wall motion from SESTAMIBI electrocardiogram (ECG)-gated images was obtained, according to the assumption that changes in the detected radioactivity reflect changes in myocardial wall thickness during the cardiac cycle. As a preliminary study, 20 patients with coronary artery disease and regional wall motion abnormalities and 15 normal subjects were studied by SESTAMIBI scintigraphy and contrast ventriculography. Regional wall motion was analyzed by a radial method applied to both techniques. Absolute systolic changes in radioactivity and its ratio to reference normal values (wall thickening index, WTI) were determined in 9 anatomical cardiac regions according to the formula (endsystolic counting profile-enddiastolic counting profile/enddiastolic counting profile) x 100. The overall agreement between radioisotopic and ventriculographic techniques was 88% (158 of 180 segments). Normal, hypokinetic and akinetic ventriculographic segments showed WTI values of 1.1 +/- 0.2, 0.8 +/- 0.2 and 0.4 +/- 0.3 respectively (P less than 0.001). A second clinical study was performed in 25 patients studied by stress/rest ECG-gated SESTAMIBI scintigraphy. The assumption of this part of the study was to investigate if a preserved wall thickening in segments with stress defects might predict those areas with normal resting perfusion. Partial or total normalization of regional perfusion was observed in 90% of segments with a WTI greater than or equal to 0.8. These studies indicate the ECG-gated SESTAMIBI may represent a suitable technique for the simultaneous analysis of flow distribution and function. Analysis of post-exercise ECG-gated SESTAMIBI can predict the reversibility of transient perfusion defects.

Adult↗
PubMed1992

Regional myocardial blood flow and coronary reserve in hypertensive patients. The effect of therapy.

Patients with essential arterial hypertension demonstrate abnormal vasodilator capacity either during increased cardiac metabolic demand or during pharmacological vasodilation. Structural and functional damage to the coronary microcirculation has been proposed as one of the major causes of impaired coronary reserve in this disease. To assess the role of microvascular impairment in regional myocardial blood flow (MBF), 27 patients with essential hypertension were evaluated by dynamic positron emission tomography (PET) at rest, during atrial pacing and after dipyridamole infusion and compared with 13 healthy subjects. All patients had normal coronary arteries, 17 had moderate to severe hypertension and 10 had mild hypertension. Baseline mean MBF of 0.97 +/- 0.25 ml/min/g was significantly increased to 1.60 +/- 0.38 during atrial pacing and 2.35 +/- 0.95 after dipyridamole infusion (p < 0.01); however, mean flow during atrial pacing and after dipyridamole infusion was significantly lower than in healthy subjects (2.15 +/- 0.73 and 3.71 +/- 0.86 ml/min/g, p < 0.05 and p < 0.01, respectively). The MBF response to atrial pacing and dipyridamole infusion was similarly depressed in patients with mild and severe hypertension. The study was repeated after 6 months of antihypertensive treatment with the calcium antagonist verapamil or the angiotensin converting enzyme (ACE) inhibitor enalapril in a subgroup of 20 patients as part of a randomised, single-blind clinical trial. This study is still in progress; the initial 16 patients treated with verapamil or enalapril showed an obvious improvement in MBF values during atrial pacing and after dipyridamole infusion after 6 months of therapy (mean MBF: 2.10 +/- 0.64 and 2.99 +/- 1.63 ml/min/g, respectively, p < 0.05 vs pretreatment values). In conclusion, obvious impairment of MBF during atrial pacing and after dipyridamole infusion was observed in hypertensive patients with normal coronary arteries and this appeared unrelated to the severity of hypertension. Therapy with verapamil or enalapril improved coronary reserve and MBF response to an increase in myocardial oxygen demand.

Adult↗
PubMed1992

The role of sestamibi scintigraphy in the radioisotopic assessment of myocardial viability.

The relationship between sestamibi uptake as a marker of myocardial viability and postrevascularization function recovery is still to be defined. We studied 14 patients (13 males, 1 female, mean age 55 +/- 7 yr, range 35 to 64 yr) with sestamibi scintigraphy, quantitative coronary angiography and two-dimensional echocardiography. Sestamibi uptake was quantified from planar images and expressed as percent of maximal activity in each projection using a 13-segment model. All defects were subgrouped on the basis of the severity of reduction in sestamibi uptake; the limit of viability was set at 2.5 s.d. below the normal uptake (55%). Echocardiography was analyzed using a score index ranging from 1 (normokinesis) to 4 (dyskinesis) and a corresponding regional model. Before revascularization, 42 segments were grouped as normal (coronary stenosis < 50% and normal function, Group 1); of the remaining 140 segments related to > 50% coronary stenosis, 67 had normal wall motion (Group 2) and 73 showed regional dyssynergies (Group 3). Sestamibi percent activity was high in Group 1 and significantly reduced in both Group 2 and 3 segments. Pre- and postrevascularization echocardiography was compared in all patients. Sestamibi sensitivity and specificity in the detection of postrevascularization recovery of function was 83% and 71%, respectively; positive predictive accuracy was 79%. The presence of a severe defect identified most of those segments with wall motion abnormalities that did not recover following coronary revascularization; however, sestamibi overestimated rest perfusion defects in 25% of territories supplied by stenotic coronary arteries that had normal wall motion at rest. Sestamibi appears to be primarily a perfusion agent that can provide limited information regarding viability.

Adult↗
PubMed1991

Accuracy and safety of technetium-99m hexakis 2-methoxy-2-isobutyl isonitrile (Sestamibi) myocardial scintigraphy with high dose dipyridamole test in patients with effort angina pectoris: a multicenter study. Italian Group of Nuclear Cardiology.

Clinical and physiologic evidence indicates that maximal coronary vasodilation is not achieved in a large number of patients with use of the standard dose of dipyridamole (0.56 mg/kg body weight over 4 min). The feasibility, safety and accuracy of technetium-99m hexakis 2-methoxy-2-isobutyl isonitrile (Sestamibi) scintigraphy associated with intravenous high dose dipyridamole (0.56 mg/kg over 4 min followed 4 min later by an additional 0.28 mg/kg over 2 min) were evaluated in a multicenter study. Planar myocardial perfusion images were obtained at rest and after dipyridamole in 101 patients with effort chest pain and no prior myocardial infarction. High dose dipyridamole (62 patients) was used when typical chest pain or electrocardiographic (ECG) signs of ischemia, or both, did not occur during or after the standard dose (39 patients). With high dose dipyridamole, 34 patients had pain (18 patients) or ECG signs of ischemia (ST depression greater than or equal to 2 mm) (8 patients), or both (8 patients), whereas the other 28 patients had Sestamibi injection in the absence of symptoms or ECG changes. All patients underwent coronary angiography: 81 had significant coronary artery disease (greater than or equal to 50% reduction of lumen diameter) (affecting one vessel in 38, two vessels in 19 and three vessels in 24 patients) and 20 patients had normal coronary arteries. The overall sensitivity, specificity and predictive accuracy of Sestamibi scintigraphy were 81%, 90% and 83%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Coronary vasodilation is impaired in both hypertrophied and nonhypertrophied myocardium of patients with hypertrophic cardiomyopathy: a study with nitrogen-13 ammonia and positron emission tomography.

To assess regional coronary reserve in hypertrophic cardiomyopathy, regional myocardial blood flow was measured in 23 patients with hypertrophic cardiomyopathy and 12 control subjects by means of nitrogen-13 ammonia and dynamic positron emission tomography. In patients with hypertrophic cardiomyopathy at baseline study, regional myocardial blood flow was 1.14 +/- 0.43 ml/min per g in the hypertrophied (20 +/- 3 mm) interventricular septum and 0.90 +/- 0.35 ml/min per g (p less than 0.05 versus septal flow) in the nonhypertrophied (10 +/- 2 mm) left ventricular free wall. These were not statistically different from the corresponding values in control subjects (1.04 +/- 0.25 and 0.91 +/- 0.21 ml/min per g, respectively, p = NS). After pharmacologically induced coronary vasodilation (dipyridamole, 0.56 mg/kg intravenously over 4 min), regional myocardial blood flow in patients with hypertrophic cardiomyopathy increased significantly less than in control subjects both in the septum (1.63 +/- 0.58 versus 2.99 +/- 1.06 ml/min per g, p less than 0.001) and in the free wall (1.47 +/- 0.58 versus 2.44 +/- 0.82 ml/min per g, p less than 0.001). In addition, patients with hypertrophic cardiomyopathy who had a history of chest pain had more pronounced impairment of coronary vasodilator reserve than did those without a history of chest pain. After dipyridamole, coronary resistance in the septum decreased by 38% in patients without a history of chest pain, but decreased by only 14% in those with such a history (p less than 0.05). Coronary resistance in the free wall decreased by 45% in patients without and by 27% in those with a history of chest pain (p = 0.06).(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonia↗
PubMed1991

Right coronary artery disease. Pathophysiology, clinical relevance, and methods for recognition.

Among the clinical manifestations of ischemic heart disease, right coronary artery (RCA) disease offers a wide variety of right and left ventricular ischemic involvement, including prevalent right ventricular dysfunction and severe cardiac failure. Whether the right ventricular impairment is dependent primarily on ischemia of the right ventricle or requires a concomitant left ventricular dysfunction remains debatable. To assess the pathophysiology and clinical relevance of RCA-related ischemia, a systematic study of patients with single RCA disease (either vasospastic angina at rest or typical stable angina) was undertaken by radionuclide ventriculography. A high incidence of ischemia-induced right ventricular dysfunction was observed (93% and 95% in angina at rest and on effort, respectively), either alone or associated with left ventricular impairment. These results were compared with those obtained in a control population with isolated left anterior descending artery disease and either primary or secondary angina pectoris. We infer that the impairment of the right ventricle was related primarily to right ventricular ischemia and that left ventricular dysfunction alone did not cause an important depression of right ventricular systolic function. In conclusion, the clinical manifestations of RCA disease can be protean; the right ventricle can be the target of ischemia, and recognition of its impairment poses diagnostic problems. Radionuclide ventriculography and two-dimensional echocardiography, together with stressors of coronary flow reserve, are reliable techniques for assessing RCA-related ischemia.

Angina Pectoris↗
PubMed1990

Novel organ-specific circulating cardiac autoantibodies in dilated cardiomyopathy.

To determine whether organ-specific cardiac autoantibodies are present in dilated cardiomyopathy, indirect immunofluorescence on human heart and skeletal muscle was used to test sera from 200 normal subjects and from 65 patients with dilated cardiomyopathy, 41 with chronic heart failure due to myocardial infarction and 208 with other cardiac disease. Three immunofluorescence patterns were observed: diffuse cytoplasmic on cardiac tissue only (organ-specific), fine striational on cardiac and, to a lesser extent, skeletal muscle (cross-reactive 1) and broad striational on both cardiac and skeletal muscle (cross-reactive 2). Cardiac specificity of the cytoplasmic pattern was confirmed by absorption studies with homogenates of human atrium, skeletal muscle and rat liver. Organ-specific cardiac antibodies (IgG; titer range 1/10 to 1/80) were more frequent in patients with dilated cardiomyopathy (17 [26%] of 65) than in those with other cardiac disease (2 [1%] of 208, p less than 0.0001) or heart failure (0 [0%] of 41, p less than 0.001) or in normal subjects (7 [3.5%] of 200, p less than 0.0001). Organ-specific cardiac antibodies were more common in patients with dilated cardiomyopathy and in those with fewer symptoms (8 of 15 in New York Heart Association functional class I versus 9 of 50 in classes II to IV, p less than 0.01) and more recent (less than 2 years) onset of disease (9 of 19 versus 8 of 46, p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Behavior of right and left ventricles during episodes of variant angina in relation to the site of coronary vasospasm.

The effects of single-vessel coronary occlusion on simultaneously evaluated right (RV) and left ventricular (LV) performance were assessed and compared with LV perfusion patterns in 25 patients with variant angina. Coronary spasm involved the right coronary artery in 15 patients (group 1) and the left anterior descending coronary artery in 10 patients (group 2). Biventricular function was assessed by radionuclide angiography under basal conditions, during spontaneous or ergonovine-induced ischemia, and after resolution of the ischemic attack. Myocardial perfusion was assessed by thallium 201 scintigraphy in 21 patients of this series during superimposable ischemic episodes. In group 1, ischemia caused RV (14 of 15 patients) and LV (13 of 15 patients) regional dysfunction with significant reduction in RV and LV ejection fractions. The interventricular spetum was involved in six of 15 patients, causing a more pronounced LV impairment. In group 2, all patients showed septal dyssynergies associated with a reduction of LV ejection fraction; absent or trivial RV involvement was observed. In both groups, LV perfusion defects were present in all patients with LV wall motion abnormalities during ischemia, matching the site of regional dyssynergies. Thus, in a group of patients with variant angina and single-vessel disease, transient occlusion of the right coronary artery directly caused RV and LV impairment; in these patients, the extent of LV but not RV dysfunction appeared related to the presence of septal ischemia. Vasospasm of the left anterior descending coronary artery consistently caused LV dysfunction not associated with secondary effects on RV systolic function.

Angina Pectoris, Variant↗
PubMed1990

A new method for noninvasive quantitation of segmental myocardial wall thickening using technetium-99m 2-methoxy-isobutyl-isonitrile scintigraphy--results in normal subjects.

A quantitative index of regional myocardial wall motion obtained from electrocardiogram-gated perfusion images has been assessed. The assumption for the proposed algorithm is that, according to the partial volume effect, the recovery counts by the instrumentation is a function of the object size. Systo-diastolic changes in the detected radioactivity would therefore reflect changes in myocardial wall thickness. Ten normal volunteers were studied in control condition by 99mTc 2-methoxy-isobutyl-isonitrile scintigraphy. Electrocardiogram (ECG)-gated images were acquired in multiple projections. End-diastolic and end-systolic activity was measured along radii from the center to the edge of the left ventricle. Data are displayed as circumferential profiles and the percent systolic thickening determined according to the formula (end-systolic profile--end-diastolic profile) (end-diastolic profile + background) x 100.) The intra- and interobserver variabilities were +/- 5.4% and +/- 4.1%, respectively. Analysis of regional systolic thickening showed a heterogeneous pattern, with a maximal and minimum value of 35% and 27% located to the infero-apical and to the proximal anterior wall, respectively. Our values correlate well with those reported for normals using cine computed tomography or nuclear magnetic resonance.

Adult↗
PubMed1990

Simultaneous in vitro and in vivo validation of nitrogen-13-ammonia for the assessment of regional myocardial blood flow.

Measurement of myocardial blood flow by 13NH3 relies heavily on the assessment of both the input function and the variable tissue extraction fraction. In six open-chest dogs, myocardial and arterial 13NH3 activity was measured both by in vitro sampling and by in vivo positron emission tomography (PET). Regional myocardial blood flow was forced to vary in the range 0.2-5 ml/min/g and actual values were assessed by in vitro counting of 153Gd microspheres. The ammonia input function was processed by: (a) total curve integration; (b) curve integration for 2 min; (c) integral of a fitted curve (gamma variate in vivo and exponential of the downslope in vitro). Method C brought to regional flow values which best approximated microspheres data. The in vitro correlation allows for correcting in vivo values for the flow-dependent extraction fraction. The method can be easily applied for regional myocardial blood flow measurements with PET in human studies.

Algorithms↗
PubMed1989

Multiparametric approach to diagnosis of non-Q-wave acute myocardial infarction.

The present study investigated whether the lack of enzyme increase is reason enough to exclude necrosis in patients with ischemic heart disease who develop electrocardiographic sustained ST-T changes in the absence of Q waves. In 15 consecutive patients with angina who developed sustained ST-T changes during hospitalization, the presence of myocardial necrosis was investigated by a prospective multiparametric approach. Serum enzymes and myoglobin, pyrophosphate uptake, 2-dimensional echocardiography, perfusion scintigraphy, left ventriculography and coronary angiography were evaluated. According to creatine kinase and creatine kinase-MB peak at twice the upper normal value, the diagnosis of acute myocardial infarction applied only to 40% of patients. However, myoglobin was positive in 80% and a perfusion defect could be documented by an electrocardiographic gated microsphere technique in 100% of patients. The positivity of myoglobin increased to 100% and of creatine kinase and creatine kinase-MB to 87 and 60%, respectively, when a peak value twice the individual lowest value was considered for positivity. The 100% presence of perfusion defects associated with the high prevalence of both positive pyrophosphate uptake (87%) and regional dyssynergies (87 and 73%, respectively, by left ventriculography and echocardiography) strongly suggest that sustained (greater than or equal to 7 days) ST-T changes in this population were indicative of myocardial necrosis. Thus, by conventional enzymatic approach, diagnosis of non-Q-wave infarction can be missed in a sizable number of patients and present important clinical implications.

Adult↗