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Biomedical subjects

O Parodi

Publications and source records attributed to O Parodi.

At least 55 records · Page 3Linked to original sources
PubMed1995

Myocardial viability: nuclear medicine versus stress echocardiography.

The failure of nonimaging techniques in the identification of myocardial viability has promoted the clinical application of radioisotopic and echocardiographic methods. Unfortunately, none of these techniques provides, per se, a 100% predictive accuracy and only few studies have been based on the postoperative improvement in regional wall motion, the absolute "gold standard" for myocardial viability. The recent thallium-201 protocols (reinjection, late redistribution, rest studies) have provided nuclear cardiology with a cell membrane integrity image able to unmask viable myocardium in more than 85% of viable segments. Sestamibi has been introduced as a nonrecirculating flow tracer able to detect transient ischemia as well as thallium-201. Its main limit, a high sensitivity to intermediate reductions in coronary blood flow, determines a high incidence of false positive studies. Positron emission tomography allows the evaluation of regional myocardial blood flow and metabolism. The marker of viable myocardium is the mismatch between reduced blood flow and normal or increased uptake of 18-F fluorodeoxyglucose. This technique allows the detection of viable tissue in most segments showing improved postoperative function. In our experience, applying a multiparametric approach, rest thallium-201 scan, rest sestamibi, dobutamine, and dipyridamole echocardiography showed a sensitivity and a specificity of 86%, 75%, 82%, 75% and 92%, 84%, 92%, and 89%, respectively, in the detection of residual viability. The main advantages of thallium-201 are reproducibility and standardization; those of stress echo are low cost and availability. In patients with severely depressed ventricular function, positron emission tomography retains a primary role when compared to thallium-201 and stress echocardiography.

Dipyridamole↗
PubMed1995

[Dilated cardiomyopathy: a new natural history? The experience of the Italian Multicenter Cardiomyopathy Study (SPIC)].

BACKGROUND: The natural history of idiopathic dilated cardiomyopathy (IDC), once a disease with a dire prognosis, is thought to be changing. Aim of this study was to describe the clinical characteristics, long term course and prognostic factors of IDC patients followed up prospectively since the late eighties. METHODS: Patients with a diagnosis of IDC confirmed by normal coronary angiography, non specific endomyocardial biopsy findings and a left ventricular ejection fraction below 50% were consecutively enrolled in a multicenter registry and followed up at 6-months intervals. RESULTS: From January 1986 till January 1994, 441 IDC patients with a mean age of 43 +/- 13 years (range 8-68) entered the registry. Thirty per cent of patients were women and 8% had familial dilated cardiomyopathy. NYHA class was I-II in 77% and 35% of patients were asymptomatic at the time of diagnosis. Treatment included digitalis in 235 patients (53%), diuretics in 239 (54%), angiotensin converting enzyme inhibitors in 269 (61%), betablockers in 108 (24%). Chronic atrial fibrillation was detected in 10% of patients and left bundle branch block in 24%. Mean cardiothoracic ratio was 0.54 +/- 0.06. Mean left ventricular end diastolic dimension was 38 +/- 6 mm/m2; 48% of patients had minimal or mild left ventricular dilatation. Mean left ventricular ejection fraction was 30 +/- 10%. At Holter monitoring 67% of cases had complex ventricular arrhythmias, 37% had ventricular tachycardia and 4% had advanced atrioventricular block. Mean exercise stress test duration was 9 +/- 4 minutes. After a mean follow up of 31 +/- 24 months, 337 patients were alive without transplantation and 5 were lost to follow up; 60 patients (14%) had died of cardiac causes, namely heart failure (6%), sudden death (7%) and pulmonary embolism (< 1%) and 30 had been transplanted (7%), while 4 had died of unclear causes. Survival and transplant-free survival were 94% and 90% at 2 years and 82 and 76% at 5 years, respectively. At multivariate analysis pulmonary capillary wedge pressure (p = 0.0001, odds ratio, for values > 15 mm Hg, 2.05) and betablocker treatment (p = 0.002, odds ratio 0.26) were independent predictors of survival. CONCLUSIONS: In this large, multicenter prospective study, prognosis of IDC in the eighties appears to be improved. Early diagnosis, together with improved medical treatment, probably bears a causal relation to these changes.

Adolescent↗
PubMed1994

Assessment of anatomic and physiological severity of single-vessel coronary artery lesions by dipyridamole echocardiography. Comparison with positron emission tomography and quantitative arteriography.

BACKGROUND: The aim of this study was to compare the results of dipyridamole-echocardiography test (DET: two-dimensional echo monitoring during dipyridamole infusion up to 0.84 mg/kg over a period of 10 minutes) with both anatomic and physiological parameters of coronary artery disease severity, assessed by computer-assisted quantitative coronary arteriography, and regional coronary flow reserve, measured by [13N]ammonia (13NH3) and dynamic positron emission tomography (PET), respectively. METHODS AND RESULTS: We studied 31 patients with a history of chest pain and neither previous myocardial infarction nor resting wall motion abnormalities. Eighteen patients had single-vessel disease (> 50% stenosis of one major coronary vessel), and 13 had normal coronary arteries. The criterion for DET positivity was the appearance of a new transient regional wall motion abnormality. In patients with a positive DET, two parameters were evaluated: the dipyridamole time (ie, the time from the beginning of drug infusion to the development of obvious dyssynergy) and the wall motion score index (WMSI, a semiquantitative integrated estimation of extent and severity of the stress-induced dyssynergy). WMSI was derived by summation of individual segment scores divided by the number of segments interpreted. Quantification of regional myocardial blood flow was obtained by PET measurements of 13NH3 arterial input function and left ventricular myocardial tissue concentration both at control and after dipyridamole (0.56 mg/kg over 4 minutes). Maximal regional blood flow after dipyridamole in the region supplied by the stenotic vessel was significantly lower in the 11 patients with coronary artery disease and positive DET than in the 7 patients with coronary artery disease and negative DET (1.08 +/- 0.33 versus 1.98 +/- 0.37 mL.min-1.g-1, P < .01). In patients with a positive DET, regional coronary flow reserve correlated well with dipyridamole time (r = .87, P < .01) but not with peak WMSI (r = .25, P = NS). Patients with dipyridamole-induced akinesia or dyskinesia (n = 6) had a greater reduction in regional coronary flow reserve than did those showing hypokinesia (n = 5): 1.38 +/- 0.51 versus 2.17 +/- 0.42, P < .05. Percent area reduction was more severe in patients with DET positivity than in those with DET negativity (93.7 +/- 8.7% versus 77 +/- 10.3%, P < .01), and it correlated with regional coronary flow reserve (r = .64, P < .01) and dipyridamole time (r = -.59, P < .01). CONCLUSIONS: In patients with single-vessel disease, DET shows an excellent specificity but a limited sensitivity; in these patients, DET positivity is associated with a physiologically important coronary stenosis. Severity of the anatomic stenosis and impairment in regional flow reserve are greater when the dipyridamole-induced dyssynergy appears earlier during the test. Therefore, a stratification of the anatomo-physiological severity of coronary artery disease can be obtained with DET, based mainly on the temporal allocation of the transient dyssynergy.

Adult↗
PubMed1994

Global alteration in perfusion response to increasing oxygen consumption in patients with single-vessel coronary artery disease.

BACKGROUND: Recent evidence suggests that, in coronary artery disease (CAD), myocardial blood flow (MBF) regulation is abnormal in regions supplied by apparently normal coronary arteries. However, the relation between this alteration and MBF response to increasing metabolic demand has not been fully elucidated. METHODS AND RESULTS: MBF was assessed at baseline, during atrial pacing tachycardia, and after dipyridamole (0.56 mg/kg IV over 4 minutes) in 9 normal subjects and in 24 patients with ischemia on effort, no myocardial infarction, and isolated left anterior descending (n = 19) or left circumflex (n = 5) coronary artery stenosis (> or = 50% diameter narrowing). Perfusion of both poststenotic (S) and normally supplied (N) areas was measured off therapy by positron emission tomography and [13N]ammonia. Normal subjects and CAD patients showed similar rate-pressure products at baseline, during pacing, and after dipyridamole. In CAD patients, MBF was lower in S than in N territories at rest (0.68 +/- 0.14 versus 0.74 +/- 0.18 mL.min-1.g-1, respectively, P < .05), during pacing (0.92 +/- 0.29 versus 1.16 +/- 0.40 mL.min-1.g-1, respectively, P < .01), and after dipyridamole (1.18 +/- 0.34 versus 1.77 +/- 0.71 mL.min-1.g-1, respectively, P < .01). However, normal subjects showed significantly higher values of MBF both at rest (0.92 +/- 0.13 mL.min-1.g-1, P < .05 versus both S and N areas), during pacing tachycardia (1.95 +/- 0.64 mL.min-1.g-1, P < .01 versus both S and N areas), and after dipyridamole (3.59 +/- 0.71 mL.min-1.g-1, P < .01 versus both S and N areas). The percent change in flow was strictly correlated with the corresponding change in rate-pressure product in normal subjects (r = .85, P < .01) but not in either S (r = .04, P = NS) or N regions (r = .08, P = NS) of CAD patients. CONCLUSIONS: Besides epicardial stenosis, further factors may affect flow response to increasing metabolic demand and coronary reserve in patients with CAD.

Adult↗
PubMed1994

Different tracers and stressors in patients with coronary artery disease: how to standardize clinical questions and nuclear cardiology answers.

The recent introduction of new tracers and stressors has increased the number of combinations of techniques that can be used for the diagnostic and prognostic stratification of patients with coronary artery disease. However, these new techniques still need to be standardized for clinical use. Thallium-201 scintigraphy is at present the most common method to assess transient ischemia and viability in patients. Dynamic exercise and dipyridamole show similar incidence of major cardiac complications and their use can be considered sufficiently safe. Further experimental and multicenter clinical studies are needed for 99mTc-Sestamibi and 99mTc-Teboroxime and for new stressors such as adenosine and dobutamine.

Adenosine↗
PubMed1994

Maldistribution of regional myocardial perfusion at rest in patients with coronary artery disease and no previous myocardial infarction, evidenced by 99mTc-Sestamibi scintigraphy.

Since myocardial 99mTc-Sestamibi uptake is closely related to coronary blood flow and the tracer does not redistribute, resting perfusion defects may be observed even in viable regions supplied by vessels with severe stenosis. The incidence and the clinical significance of 99mTc-Sestamibi uptake defects at rest were investigated in 60 men with suspected coronary artery disease and no previous myocardial infarction, in a multicenter study. Of 60 patients, 12 showed normal coronary arteries and 48 significant coronary artery disease (> 50% luminal narrowing). Based on the presence or absence of tracer uptake defects at resting planar scans, the patients were divided into Group 1 (27 patients) and Group 2 (33 patients), respectively. A greater incidence of coronary artery disease (100% versus 64%, p < 0.01) and of multivessel disease (70% versus 36%, p < 0.05) was observed in patients of Group 1. All patients underwent dipyridamole (up to 0.84 mg/kg in 10 min) 99mTc-Sestamibi scintigraphy, which more frequently induced transient 99mTc-Sestamibi uptake defects in Group 1 than in Group 2 (85% versus 42%, p < 0.001). A high incidence of resting 99mTc-Sestamibi uptake defects was observed in patients without previous myocardial infarction; this identified a subset of patients with a higher prevalence of coronary artery disease and multivessel involvement and with a greater impairment of the coronary reserve, as evidenced by a dipyridamole test.

Coronary Circulation↗
PubMed1994

[Global change in the regulation of regional coronary flow in patients with single vessel coronary disease evidenced by positron emission tomography].

AIM OF THE STUDY: Aim of this study is to investigate whether, in patients with coronary artery disease (CAD), regional myocardial blood flow (rMBF) regulation is affected with further mechanisms besides the effects of epicardial coronary stenosis. MATERIAL AND METHODS: RMBF and coronary reserve are measured in 13 normal subjects and in 36 patients with effort angina and isolated (> or = 50% diameter narrowing) left anterior descending (LAD, 27 patients) or left circumflex (LCX, 9 patients) coronary artery stenosis. Measurements are obtained both at baseline and following dipyridamole (0.56 mg/kg in 4 minutes) using positron emission tomography and N13-ammonia. RESULTS: At rest, patients with CAD show similar rMBF values in the stenotic and remote areas (0.71 +/- 0.19 vs 0.77 +/- 0.22 ml/min/gr, respectively, ns); both values are significantly (p < 0.01) reduced with respect to mean rMBF observed in the normal subjects (1.07 +/- 0.21 ml/min/gr). Following dipyridamole, patients with CAD show lower rMBF values in stenotic than in control regions (1.25 +/- 0.54 vs 1.73 +/- 0.80 ml/min/gr, p < 0.01); however, both these values are significantly reduced when compared with mean rMBF in the normal subjects (3.76 +/- 0.88 ml/min/gr, p < 0.01). To evaluate whether reduction in resting myocardial perfusion indicates maximal vasodilatation, patients with CAD are divided into 2 groups: Group 1 with homogeneous baseline perfusion (0.73 +/- 0.2 vs 0.75 +/- 0.24 ml/min/gr, in stenotic and remote areas, respectively, ns), and Group 2 with baseline perfusion defect in the stenotic related territory (0.62 +/- 0.14 vs 0.84 +/- 0.17 ml/min/gr, p < 0.01). Coronary reserve (dipyridamole flow/baseline flow) is similar in the 2 Groups (1.74 +/- 0.66 vs 1.93 +/- 0.45, ns). CONCLUSIONS: These data suggest that, in patients with CAD, other factors beyond hydraulic effects of epicardial coronary stenosis, could modulate rMBF regulation; in fact: 1) myocardium perfused by angiographically normal coronary artery shows reduced values of both resting rMBF and coronary reserve; 2) myocardium supplied by stenotic vessel maintains a residual vasodilating capability despite a reduced baseline perfusion.

Aged↗
PubMed1993

Regional myocardial blood flow in stable angina pectoris associated with isolated significant narrowing of either the left anterior descending or left circumflex coronary artery.

Myocardial perfusion measurements were obtained with positron emission tomography under basal conditions and after intravenous dipyridamole infusion (0.56 mg/kg over 4 minutes) to determine if myocardial perfusion is maximized in areas of resting wall motion abnormalities in patients with stable angina. Thirty-three patients with no history of myocardial infarction, and with coronary stenosis > 50% involving the left anterior descending (n = 24) and left circumflex (n = 9) coronary arteries were evaluated. Quantitative perfusion images were recorded twice in each subject using nitrogen-13 ammonia at baseline and after intravenous administration of dipyridamole. Computer-assisted analysis of left ventriculograms showed abnormal wall motion in the stenosis-related regions in 16 patients (group 1), and normal regional function in 17 (group 2). The flow values in the anterior and posterolateral wall were considered to reflect left anterior and left circumflex coronary artery flow, respectively. Quantitative angiography showed that coronary stenosis severity was higher in group 1 than in group 2 (cross-sectional area reduction 94 +/- 7% vs 87 +/- 11%; p < 0.05). Resting blood flow in the stenosis-related areas was significantly lower than in contralateral regions in group 1 (0.66 +/- 0.19 vs 0.77 +/- 0.26 ml/min/g; p < 0.05), but not in group 2 (0.73 +/- 0.18 vs 0.78 +/- 0.21 ml/min/g; p = NS). Dipyridamole significantly (p < 0.01) increased myocardial blood flow in both stenotic and remote regions in both groups 1 (0.95 +/- 0.41 vs 1.57 +/- 0.70 ml/min/g) and 2 (1.54 +/- 0.53 vs 2.01 +/- 0.84 ml/min/g).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Alteration in regulation of myocardial blood flow in one-vessel coronary artery disease determined by positron emission tomography.

The behavior of myocardial blood flow (MBF) regulation in territories supplied by angiographically normal vessels of patients with coronary artery disease (CAD) has been poorly investigated. Resting MBF and coronary reserve were evaluated in 32 patients with stable angina, no previous myocardial infarction, and isolated left anterior descending or left circumflex coronary artery stenosis (> or = 50% diameter narrowing). MBF was measured, in the absence of any medical therapy, by means of dynamic positron emission tomography and 13N-ammonia. MBF measurements at baseline and after intravenous dipyridamole (0.56 mg/kg administered over 4 minutes), were obtained both in the stenosis-related regions and in contralateral territories. As a control group, 14 normal subjects were evaluated according to the same protocol. At rest, the 32 patients with CAD had similar MBF values in the stenotic and remote regions (0.76 +/- 0.21 and 0.77 +/- 0.19 ml/min/g, respectively, p = NS); both these values were significantly (p < 0.01) reduced with respect to mean MBF in normal subjects (1.03 +/- 0.25 ml/min/g). The dipyridamole study was completed in 30 patients; these patients had lower values of maximal MBF in the stenotic than in the remote regions (1.52 +/- 0.65 vs 1.76 +/- 0.68 ml/min/g, p < 0.05); however, both these values were significantly reduced (p < 0.01) with respect to mean dipyridamole MBF in normal subjects (3.66 +/- 0.92 ml/min/g). Thus, in patients with CAD, resting and maximal MBF can be reduced not only in myocardial territories supplied by stenotic arteries, but also in territories supplied by angiographically normal arteries.

Aged↗
PubMed1993

Does the myocardium become "stunned" after episodes of angina at rest, angina on effort, and coronary angioplasty?

To assess whether myocardial stunning occurs after brief periods of ischemia, global and regional ventricular function assessed by radionuclide angiography was studied in 52 patients. Patients were divided into 3 groups according to the type of ischemic episodes. Group 1 consisted of 15 patients studied before, during and after episodes of angina at rest. Seventeen patients studied immediately before and after coronary angioplasty constituted group 2. Group 3 consisted of 20 patients with stable angina studied before, during and after exercise-induced ischemia. Medical therapy was discontinued 48 hours before the study in all patients except those undergoing coronary angioplasty who were receiving diltiazem 180 mg/day. No difference in baseline ejection fraction was found between groups, whereas peak filling rate was statistically lower in group 3 patients. Evidence of left ventricular dysfunction during ischemia was seen in patients in groups 1 and 3, whereas transient ischemia was documented by ST-segment displacement and/or typical chest pain during balloon inflation in group 2. Persistence of systolic or diastolic dysfunction was not observed in any of the 3 groups in the recovery phase after ischemia. In conclusion, transient ischemia caused either by a primary reduction in oxygen supply (angina at rest, coronary angioplasty) or by an increase in oxygen demand (angina on effort) 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 marked ventricular dysfunction. The search for stunned myocardium should be extended to other different clinical models characterized by prolonged ischemia such as unstable angina or myocardial infarction.

Aged↗
PubMed1993

Value of rest thallium-201/technetium-99m sestamibi scans and dobutamine echocardiography for detecting myocardial viability.

The relation between radioisotopic and echocardiographic markers of myocardial viability and postrevascularization recovery of function is still to be defined. To this purpose, 14 patients (11 men, 3 women, aged 35 to 64 years, mean 54 +/- 7) with ventricular dysfunction were studied by a multiparametric approach. Each patient underwent, on separate days, rest thallium-201 and technetium-99m sestamibi scintigraphy, dobutamine echocardiography and coronary angiography. Coronary angiography was analyzed by a quantitative approach. Thallium uptake at rest was quantified from planar early (10-minute) and delayed (16-hour) thallium-201 images and expressed as a percentage of maximal activity in each projection using a 13-segment model. Sestamibi uptake was expressed in the same way. Dobutamine (up to 10 micrograms/kg/min) echocardiography was analyzed using a score index ranging from 1 (normokinesia) to 4 (dyskinesia) and a similar segmental model. Before revascularization 50 segments were grouped as normal (coronary stenosis < 50% and normal function, group 1); of the remaining 132 segments with > 50% coronary stenosis, 57 had normal wall motion (group 2) and 75 showed regional dyssynergies (group 3). Early and delayed thallium-201 regional percent activities did not differ in group 1 and in group 2 but were significantly less in group 3 segments. Sestamibi percent activity was more in group 1 and significantly reduced both in group 2 and 3 segments. Segments with improved wall motion after dobutamine had more early, delayed thallium-201 and sestamibi percent activities than unresponsive segments. Postrevascularization echocardiography was performed in all patients. Delayed thallium-201 scans and dobutamine echocardiography showed good sensitivity and specificity in detecting viable myocardium. (ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Angiography↗
PubMed1993

Evaluation of regional myocardial systolic and diastolic function using ECG-gated Sestamibi scintigraphy. Preliminary results in patients with and without coronary artery disease.

Sestamibi allows ECG-gated acquisition and similarly to radionuclide angiography a time-activity curve from a defined myocardial region can be derived and analysed. Diastolic (peak relaxation velocity) and systolic (per cent thickening) functional parameters from Sestamibi ECG-gated acquisition were obtained; this data were compared in 10 patients with radionuclide angiographic data (peak filling rate and ejection fraction, respectively). A high correlation was found between peak relaxation velocity and peak filling rate (r = 0.792), while no significant correlation was found between thickening and ejection fraction (r = 0.577). Sestamibi parameters were calculated in 15 patients with known or suspected coronary artery disease and compared with those obtained in 10 normal subjects. In regions supplied by stenotic vessels the average values of peak relaxation velocity and thickening were significantly lower than those obtained in control subjects in the corresponding vascular territory. The average regional values of the diastolic parameter were significantly lower than the corresponding normal range also in regions with preserved systolic function, i.e. with thickening values within 1SD from the mean value of normals. In conclusion, from the ECG-gated acquisition of Sestamibi regional diastolic and systolic functional parameter may be derived; this completes the spectrum of information that can be obtained by a single injection of tracer.

Coronary Disease↗
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. Technetium-99m-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.

Blood Flow Velocity↗
PubMed1993

Metabolic and hemodynamic effects of insulin on human hearts.

Myocardial muscle is considered to be a target tissue for insulin action, but direct measurements of insulin's effects on cardiac hemodynamics and intermediary metabolism in humans are scarce. We combined great cardiac vein (GCV)/arterial catheterization with the euglycemic insulin clamp technique and thermodilution in six healthy middle-aged (53 +/- 2 yr) volunteers. In the fasting state, the myocardium extracted free fatty acid (FFA), lactate, pyruvate, glycerol, and beta-hydroxybutyrate (6.4 +/- 0.8, 6.2 +/- 1.0, 0.58 +/- 0.12, 0.44 +/- 0.15, and 11 +/- 2 mumol/min, respectively) and consumed 0.26 +/- 0.02 mmol/min oxygen. As fasting plasma insulin (73 +/- 6 pmol/l) was raised and clamped at 503 +/- 16 pmol/l for 100 min while maintaining euglycemia (approximately 5 mmol/l), arterial levels of lactate and pyruvate rose (by 121 and 159%, respectively), whereas FFA, glycerol, and beta-hydroxybutyrate fell (by 69, 48, and 85%, respectively, all P < 0.001). Correspondingly, net myocardial uptake of glucose, lactate, and pyruvate increased to 18.9 +/- 3.5, 32.0 +/- 2.3, and 2.7 +/- 0.5 mumol/min, respectively, whereas net extraction of circulating FFA, glycerol, and beta-hydroxybutyrate was abolished (all P < 0.001). The stimulation of lactate and pyruvate uptake was the result of both increased arterial supply and enhanced myocardial extraction ratio (from 19 +/- 3 to 51 +/- 6% for lactate, from 26 +/- 5 to 44 +/- 5% for pyruvate, P < 0.001 for both). This shift from fat to carbohydrate fuel usage occurred in the absence of changes in oxygen consumption, heart rate, GCV blood flow, aortic pressures, coronary vascular resistance, and left ventricular end-diastolic pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxybutyric Acid↗
PubMed1993

Residual coronary reserve despite decreased resting blood flow in patients with critical coronary lesions. A study by technetium-99m human albumin microsphere myocardial scintigraphy.

BACKGROUND: Experimental data demonstrate the persistence of a transmural vasodilator reserve in the face of depressed resting myocardial perfusion. The present study was designed to determine whether resting myocardial hypoperfusion indicates exhausted coronary reserve (CR). METHODS AND RESULTS: Fifteen patients with stable angina, isolated left anterior descending coronary artery (LAD) stenosis, and no previous myocardial infarction were evaluated by means of 99mTc human albumin microsphere scintigraphy. Regional myocardial perfusion and CR were assessed at baseline and after LAD papaverine (10-12 mg) by means of two microsphere injections in the left ventricle and compared with five normal subjects. Two 300-second scans were obtained with a mobile gamma camera positioned in the 70 degrees left anterior oblique projection; actual microsphere distribution after papaverine was obtained by image subtraction. The two arterial input functions (basal and papaverine) were measured from the first-pass time-activity curves and validated with the reference arterial sample technique. From the comparison of circumferential profile analysis between patients and normal subjects, nine patients (group 1A) showed perfusion defects at rest (reduction of percent radioactivity below 2 SD of normal subjects) in the LAD territory, and the other six (group 1B) showed homogeneous perfusion. CR (papaverine/resting perfusion) was 3.8 +/- 0.2 and 1.51 +/- 0.27 in normal subjects and in ischemic patients, respectively (p < 0.01). Despite resting hypoperfusion, group 1A showed a papaverine-recruitable CR similar to that of group 1B (1.57 +/- 0.33 and 1.43 +/- 0.16, respectively, p = NS). CONCLUSIONS: In patients with stable angina pectoris, isolated LAD stenosis, and no previous myocardial infarction, microsphere scintigraphy disclosed a high incidence of resting perfusion defects; in those patients, a residual CR was observed despite decreased resting blood flow.

Adult↗
PubMed1993

Myocardial blood flow distribution in patients with ischemic heart disease or dilated cardiomyopathy undergoing heart transplantation.

BACKGROUND: The present investigation was designed to obtain an absolute measurement of myocardial blood flow and of its transmural distribution in ischemic heart disease and idiopathic dilated cardiomyopathy and to provide a reference standard for cardiac imaging in nuclear cardiology. METHODS AND RESULTS: Regional myocardial blood flow and its transmural distribution were estimated by the reference microsphere method in eight patients with idiopathic dilated cardiomyopathy (n = 4) or ischemic heart disease (n = 4) during heart transplant procedure. Before aortic clamping, 99mTc-labeled human albumin microspheres were injected into the left atrium while arterial blood was sampled from the aorta at a constant rate. No complications were observed during or after the procedure. From the excised heart, myocardial slices for gamma camera imaging and well counting analysis were obtained. Myocardial blood flow was assessed by a well counter, correlated with the extent of fibrosis expressed as collagen per total tissue proteins obtained from 4-hydroxyproline and glycine as determined by high-performance liquid chromatography. Microsphere distribution, as seen by gamma camera images in a different slice, was correlated with the extent of fibrosis assessed by histological analysis of the same myocardial specimen. Mean transmural myocardial blood flow was 0.49 +/- 0.17 and 0.38 +/- 0.15 mL.min-1 x g-1 in idiopathic dilated cardiomyopathy and ischemic heart disease, respectively (P < .01). Endocardial-to-epicardial flow ratio was lower in ischemic heart disease than in idiopathic dilated cardiomyopathy patients (0.99 +/- 0.33 versus 1.16 +/- 0.30, P < .05). Mean myocardial fibrosis was 9 +/- 6% in idiopathic dilated cardiomyopathy and 25 +/- 28% in ischemic heart disease. In both groups, no correlation was found between myocardial blood flow values and the extent of fibrosis. In ischemic heart disease, regional myocardial blood flow was not significantly affected by the severity of coronary stenosis (< or = 70% or > 70%) either in the endocardium (0.44 +/- 0.24 versus 0.36 +/- 0.16 mL.min-1 x g-1, P = NS) or in the epicardium (0.50 +/- 0.33 versus 0.38 +/- 0.33 mL.min-1 x g-1, P = NS). By gamma camera imaging, transmural microsphere distribution appeared more homogeneous in idiopathic dilated cardiomyopathy than in ischemic heart disease (mean coefficient variation, 18% and 27%, respectively; P < .02); the severity of perfusion impairment did not correlate with the extent of fibrosis evaluated by histological criteria. CONCLUSIONS: Heart transplant surgery offers a valuable model to assess absolute myocardial perfusion in human heart failure. Myocardial blood flow is markedly depressed in failing hearts of both ischemic heart disease and idiopathic dilated cardiomyopathy patients; a different transmural myocardial blood flow distribution is observed in ischemic heart disease than in idiopathic dilated cardiomyopathy, with prevalent endocardial perfusion in the latter but not the former condition. In patients with end-stage heart failure, myocardial blood flow appears to be similarly impaired in fibrotic and viable regions. Mechanisms other than myocardial fibrosis and coronary lesions appear to operate in determining myocardial blood flow impairment in heart failure.

Adult↗
PubMed1993

Imaging of myocardial viability: a head-to-head comparison among nuclear, echocardiographic, and angiographic techniques.

The relationship between radioisotopic, echocardiographic, and angiographic markers of myocardial viability is still to be defined. To this purpose, 14 patients with previous myocardial infarction were studied using a multiparametric approach. Each patient underwent, on separate days, rest thallium 201 and technetium 99m Sestamibi planar scintigraphy, dobutamine/dipyridamole stress echocardiography, and coronary angiography; 11 of these patients underwent also dipyridamole echocardiographic testing. Thallium 201 and Sestamibi uptakes at rest were expressed as percentage of maximal activity in each projection using a 13 segment model. Dobutamine and dipyridamole stress echocardiography were analyzed using a score index ranging from 1 (normokinesis) to 4 (dyskinesis) and a similar segmentation. Coronary angiography was analyzed by quantitative approach. In all patients, follow-up echocardiography was performed following coronary revascularization. Before revascularization, 75 segments showed regional dyssynergies. Thallium 201 showed the highest sensitivity and specificity in the preoperative identification of viability, whereas Sestamibi was affected by a significant number of false-negative studies. Among echocardiographic techniques, dobutamine was slightly superior to dipyridamole in the detection of viable segments. The degree of coronary stenosis failed to predict the recovery of function following by-pass graft or angioplasty in almost all segments; however, in case of occlusion, most viable segments were perfused by adequately collateralized coronary arteries.

Adult↗