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Biomedical subjects

O Parodi

Publications and source records attributed to O Parodi.

At least 19 recordsLinked to original sources
PubMed1998

High-performance liquid chromatographic determination of total plasma homocysteine with or without internal standards.

Hyperhomocysteinemia is an independent risk factor for atherosclerosis and vascular occlusive disease. Assessment of total plasma concentration of homocysteine (tHcys) requires accurate and reproducible measurements. The aim of this study was to test a rapid isocratic HPLC method for tHcys analysis with an internal standard (I.S.) of alpha-mercaptopropionylglycine (MPG), 2-mercaptoethylamine (ME), or N-acetylcysteine (NAC) or without I.S., and to verify whether the use of an I.S. improves the precision. The method without I.S. showed an excellent linearity (y = 1.59x - 0.15, r = 1), recovery (100%) and a within-assay relative standard deviation (R.S.D.) of 1.2%. Instead, in our hands, the presence of I.S.s decreased the reproducibility (within-assay R.S.D. ranged from 4.5 to 6.5%) and lengthened the chromatogram by up to four to five times. In conclusion, HPLC measurement of plasma tHcys without I.S. improves accuracy with respect to determination with I.S.; moreover, this approach allows to routinely process larger amounts of plasma samples.

Chromatography, High Pressure Liquid↗
PubMed1998

Which variable of stenosis severity best describes the significance of an isolated left anterior descending coronary artery lesion? Correlation between quantitative coronary angiography, intracoronary Doppler measurements and high dose dipyridamole echocardiography.

OBJECTIVES: This study sought to investigate the angiographic or intracoronary Doppler variables of stenosis severity that best correlate with the results of dipyridamole echocardiography. BACKGROUND: Quantitative coronary angiography and intracoronary Doppler flow velocity assessments are the commonly used techniques for the objective identification of significant coronary artery stenosis. METHODS: Thirty patients with an isolated lesion of the left anterior descending coronary artery (LAD) were studied by means of on-line quantitative coronary arteriography, intracoronary Doppler flow velocity measurements and dipyridamole echocardiography 6 months after percutaneous transluminal coronary angioplasty. The quantitative arteriographic analyses were performed on-line; post-stenotic Doppler flow velocities were measured at baseline and after adenosine infusion. Angiographic and Doppler measurements were compared with the corresponding dipyridamole echocardiographic data and analyzed by discriminant analysis. RESULTS: The dipyridamole echocardiographic response was positive in 11 patients (37%). The best cutoff values for predicting an abnormal echocardiographic response were 1) stenotic flow reserve of 2.8 (p = 0.0001); 2) 59% diameter stenosis (p = 0.0001); 3) minimal lumen diameter of 1.35 mm (p = 0.001); 4) coronary flow reserve of 2.0 (p = 0.0002); and 5) maximal peak velocity of 60 cm/s during hyperemia (p = 0.04). Multivariate analysis identified stenotic flow reserve as the only independent predictor of ischemia during dipyridamole echocardiography. CONCLUSIONS: Stenotic flow reserve is the variable that best describes the functional significance of an isolated LAD lesion, and a value of 2.8 is the best predictor of a positive dipyridamole echocardiographic response. Furthermore, angiographic variables of stenosis severity relate to echocardiographic test results better than intracoronary Doppler variables.

Adult↗
PubMed1998

Super-normal 201Tl retention in hibernating myocardium: an ex-vivo study using the failing human heart.

OBJECTIVE: Although the relationship between delayed 201Tl distribution and blood flow in acutely ischemic and infarcted myocardium has been widely explored in the experimental setting, its behaviour in chronically hypoperfused dysfunctioning human myocardium has not yet been evaluated. METHODS: In tissue samples of excised failing hearts taken from ischemic (IHD) patients and idiopathic dilated cardiomyopathy (IDC) controls, we evaluated the relationship between delayed 201Tl retention (4 h redistribution), blood flow (assessed by means of 99mTc-labelled human albumin microspheres injected during transplantation) and biochemically-assessed fibrosis. 201Tl activity was expressed as the percent of the activity in the region with highest flow and the least fibrosis. RESULTS: Fibrosis and 201Tl activity were inversely related (r = -0.62, P = 0.0001). In IDC controls, low flows corresponded to uniformly preserved 201Tl retention. In IHD, 46 segments with flows < or = 0.60 ml.min-1.g-1 and 20 segments with flows > 0.60 ml.min-1.g1 showed matching delayed 201Tl retention and flow values; in the remaining 27, there was a disproportionately high tracer accumulation in comparison with flow (flow/201Tl mismatch). Despite significantly less fibrosis and lower flows, the mismatch segments showed significantly greater. 201Tl activity than the segments with concordantly high tracer retention and flow values. Conversely, at equivalent flow rates, the mismatch regions had less fibrosis than the areas with concordantly depressed 201Tl activity and perfusion. CONCLUSIONS: This super-normal 201Tl retention in hibernating myocardium may indicate a mechanism of cell adaptation to chronic hypoperfusion.

Adult↗
PubMed1998

Homogeneously reduced versus regionally impaired myocardial blood flow in hypertensive patients: two different patterns of myocardial perfusion associated with degree of hypertrophy.

OBJECTIVES: The aim of this study was to quantitatively measure regional and global myocardial blood flow and coronary reserve in hypertensive patients without coronary artery disease and to assess the correlation with left ventricular mass. BACKGROUND: The effect of left ventricular hypertrophy on regional vasodilating coronary capability in arterial hypertension is controversial, and no quantitative method has been applied to assess a possible correlation. METHODS: Positron emission tomography was performed in 50 untreated hypertensive patients and 13 normotensive subjects. Blood flow at baseline and after dipyridamole was globally and regionally measured by using nitrogen-13 ammonia; coronary reserve and resistance were calculated. Left ventricular mass was assessed by two-dimensional echocardiography. RESULTS: In hypertensive patients, flow at baseline was similar to that of normotensive subjects (p = 0.21), but values were reduced after pharmacologic vasodilation (p < 0.05). This impairment of maximal coronary flow was not correlated with left ventricular mass (p = 0.13). Among hypertensive patients, we identified a group with a homogeneous distribution of perfusion and a group with a heterogeneous flow pattern. Flow was globally reduced in the former group, but it was abnormal only at the site of perfusion defects in the latter. Patients with regional defects showed the highest likelihood of having an increased left ventricular mass. CONCLUSIONS: In arterial hypertension, left ventricular mass is not correlated with global myocardial blood flow. Nevertheless, patients with ventricular hypertrophy are likely to show a heterogeneous flow pattern with regional defects and almost normal blood flow in nonaffected regions. In hypertensive patients with a homogeneous perfusion pattern during stress, myocardial blood flow frequently shows a diffuse reduction.

Adult↗
PubMed1998

Evaluation of compartmental and spectral analysis models of [18F]FDG kinetics for heart and brain studies with PET.

Various models have been proposed to quantitate from [18F]-Fluoro-Deoxy-Glucose ([18F]FDG) positron emission tomography (PET) data glucose regional metabolic rate. We evaluate here four models, a three-rate constants (3K) model, a four-rate constants (4K) model, an heterogeneous model (TH) and a spectral analysis (SA) model. The data base consists of [18F]FDG dynamic data obtained in the myocardium and brain gray and white matter. All models were identified by nonlinear weighted least squares with weights chosen optimally. We show that: 1) 3K and 4K models are indistinguishable in terms of parsimony criteria and choice should be made on parameter precision and physiological plausibility; in the gray matter a more complex model than the 3K one is resolvable; 2) the TH model is resolvable in the gray but not in the white matter; 3) the classic SA approach has some unnecessary hypotheses built in and can be in principle misleading; we propose here a new SA model which is more theoretically sound; 4) this new SA approach supports the use of a 3K model in the heart with a 60 min experimental period; it also indicates that heterogeneity in the brain is modest in the white matter; 5) [18F]FDG fractional uptake estimates of the four models are very close in the heart, but not in the brain; 6) a higher than 60 min experimental time is preferable for brain studies.

Brain↗
PubMed1998

Perfusion-contraction mismatch during inotropic stimulation in hibernating myocardium.

UNLABELLED: The aims of this study were to assess the value of dobutamine echocardiography in identifying myocardial hibernation versus stunning and to elucidate the underlying pathophysiological mechanism of the contractile impairment. METHODS: Twenty-one patients with isolated stenosis of the left anterior descending artery were evaluated 1 mo after thrombolysed acute anterior infarction. Regional function and blood flow were measured using echocardiography and PET at rest and during dobutamine administration (10 microg/kg/min). RESULTS: Defined by [18F]fluorodeoxyglucose uptake, 36 of 102 dyssynergic segments were necrotic, and 66 were viable. The latter segments were subdivided according to their [13N]ammonia flow distribution: 30 hibernating regions with perfusion defects (flow of <80% of maximum) and 36 stunned areas with preserved resting perfusion (flow of > or =80% of maximum). Resting flows were similar in necrosis and hibernation (0.43 +/- 0.18 versus 0.47 +/- 0.16 ml x min(-1) x g(-1); not significant), and both resting values were lower than those seen in stunning (0.79 +/- 0.24; p < 0.05). Flow response to dobutamine was markedly reduced in necrosis (dobutamine/resting flow = 1.16 +/- 0.27), whereas it was maintained in hibernation (1.65 +/- 0.54) and stunning (1.42 +/- 0.57). Dobutamine improved function in a higher number of stunned (55%) than hibernating (16%) or necrotic (11%) segments. CONCLUSION: Dobutamine improves function mainly in stunned myocardium and does not reliably identify hibernation. The lack of functional response in hibernation is not related to an exhausted vasodilating capacity.

Cardiotonic Agents↗
PubMed1998

[Collateral circulation and the coronary reserve].

The mechanisms regulating coronary collateral circulation are largely unknown owing to both the complex and variable nature of clinical models and the difficulty to obtain quantitative and differentiated flow measurements within the various coronary tree portions. With the aim of assessing collateral flow reserve, we studied 19 patients with effort angina, without myocardial infarction and with isolated occlusion of either the left anterior descending coronary artery (n = 14) or the circumflex coronary artery (n = 5). Flow values were measured basally, during atrial pacing induced tachycardia and following ev dipyridamole infusion (0.56 mg/kg of body weight in 4 min), by means of positron emission tomography and nitrogen-13 ammonia as flow tracer, within both regions depending on collateral circulation and the remote ones. Results have been compared with those obtained in 13 normal subjects. Basal flow values in regions depending on collateral circulation and in the remote regions (0.61 +/- 0.11 vs 0.63 +/- 0.17 ml/min/g) were found to be similar, but lower than in normal subjects (1.00 +/- 0.20 ml/min/g, p < 0.01). During atrial pacing, flow increased to 0.83 +/- 0.25 and to 1.11 +/- 0.39 ml/min/g, in the regions depending on collateral circulation and in the remote regions, respectively (p < 0.05 as compared to baseline); again, values were lower than in normal subjects (1.86 +/- 0.61 ml/min/g, p < 0.01). Dipyridamole infusion further increased flow in the remote regions (1.36 +/- 0.57 ml/min/g, p < 0.01 as compared to atrial pacing) but it did not in the regions depending on collateral circulation (0.94 +/- 0.37 ml/min/g, NS as compared to atrial pacing); both values were lower than in normal subjects (3.46 +/- 0.78 ml/min/g, p < 0.01). Flow reserve in the regions depending on collateral circulation was found to have a direct linear correlation with the one in the remote regions (r = 0.83; p < 0.01). In conclusion, in spite of basal hypoperfusion, collateral circulation maintains a flow reserve which, even if reduced, is able to cope with moderate increments in oxygen consumption. An analogous flow reduction can be observed in the remote regions, suggesting that the entire coronary tree is involved, beyond the obstructive lesions of the main arterial branches.

Adult↗
PubMed1997

Comparative effects of enalapril and verapamil on myocardial blood flow in systemic hypertension.

BACKGROUND: The comparative effects of calcium channel blockers and ACE inhibitors on myocardial blood flow (MBF) in hypertensive patients after long-term treatment are still unknown. METHODS AND RESULTS: Twenty hypertensive subjects with normal coronary arteries were randomly assigned to verapamil 240 to 480 mg/d or enalapril 10 to 40 mg/d. MBF was quantified at rest, during pacing tachycardia, and after dipyridamole by positron emission tomography and 13N-ammonia before and 6 months after treatment after 1 week of pharmacological washout. In both groups, blood pressure and heart rate during flow measurements were not different before and after therapy. Before treatment, mean MBF at rest, during pacing tachycardia, and after dipyridamole infusion was similar in the two groups; however, pacing and dipyridamole flows were significantly lower than those obtained in a control group of normotensive subjects. After treatment, in the enalapril-treated patients, MBF did not change in the three study conditions. In the verapamil-treated patients, MBF did not change at rest and significantly increased during pacing and after dipyridamole. The inhomogeneity of regional MBF distribution, evaluated from the coefficient of variation, decreased at rest after both treatments and, in the enalapril group, also during pacing. No relation was found between changes in MBF and changes in left ventricular mass. CONCLUSIONS: In arterial hypertension, MBF during pacing tachycardia and after dipyridamole is impaired. Successful therapy with verapamil increases MBF response to these stimuli, independent of changes in perfusion pressure and left ventricular mass. These results suggest that verapamil directly improves coronary microcirculatory function in hypertension. Enalapril does not significantly change MBF but reduces the inhomogeneity of regional flow distribution.

Antihypertensive Agents↗
PubMed1997

Coronary vasoconstriction during myocardial ischemia induced by rises in metabolic demand in patients with coronary artery disease.

BACKGROUND: In patients with coronary artery disease, a maximal vasodilation of the coronary microcirculation is generally assumed to occur during myocardial ischemia induced by rises in metabolic demand. However, vasoconstriction has been documented during severe prolonged ischemia in animals. The aim of this study was to investigate coronary vasomotor tone during pacing-induced ischemia in humans. METHODS AND RESULTS: The study included 11 patients with exercise-induced ischemia and single-vessel disease of the left anterior descending artery and 7 control subjects with normal coronary arteries. Blood flow velocity was monitored with a Doppler catheter in the left anterior descending artery. Coronary resistance index was calculated as the ratio between mean arterial pressure and flow velocity. Measurements were obtained at baseline, after intracoronary adenosine (2 mg), and during maximal atrial pacing in the absence and presence of adenosine. After adenosine administration at rest, coronary resistance decreased more in control subjects than in patients (25 +/- 7% of baseline versus 61 +/- 19%; P < .01). Coronary resistance decreased in all control subjects (P < .01) both at maximal pacing (60 +/- 17% of baseline) and after administration of adenosine during tachycardia (31 +/- 13% of baseline). By contrast, all 10 ischemic patients displayed increased coronary resistance at maximal heart rate (221 +/- 131% of baseline; P < .01 versus baseline, P < .01 versus control subjects). At this stage, adenosine decreased coronary resistance to 44 +/- 20% of values observed before injection. Additionally, it reduced ST-segment depression in 5 of 8 patients. CONCLUSIONS: In patients with coronary artery disease, transient myocardial ischemia induced by increased metabolic demand is not associated with maximal vasodilation. Rather, an inappropriate severe microvascular vasoconstriction is present that can be abolished by intracoronary adenosine.

Adenosine↗
PubMed1997

Flow-function relation in patients with chronic coronary artery disease and reduced regional function. A positron emission tomographic and two-dimensional echocardiographic study with coronary vasodilator stress.

OBJECTIVES: We sought to elucidate the flow-function relation in chronic postischemic dysfunction during vasodilator stress. BACKGROUND: In patients with ischemia and regional dysfunction, stress echocardiography can elicit three responses in the dysfunctioning segments: no change, improvement or worsening. The physiology underlying these responses is unclear. METHODS: Seventeen patients with ischemia and left ventricular dysfunction underwent evaluation of regional function by two-dimensional echocardiography and myocardial blood flow by positron emission tomography and 13N-ammonia. Flow (ml/min per g) and function (regional wall motion score [RWMS] from 1 = normal to 4 = dyskinetic) were evaluated both at rest and after dipyridamole (0.56 mg/kg body weight over 4 min). RESULTS: In 45 normal segments, rest to dipyridamole flow increased from 0.83 +/- 0.22 (mean +/- 1 SD) to 1.87 +/- 0.90 (p < 0.01) with a hyperkinetic contraction pattern. Among dysfunctioning segments, responders (n = 11) showed an upsloping flow-function curve during stress (i.e., increased function [RWMS rest 2.5 +/- 0.5 vs. dipyridamole 1.2 +/- 0.4] and increased flow [rest 0.69 +/- 0.30 vs. dipyridamole 1.89 +/- 1.43, p < 0.01]); nonresponders (n = 20) had a flat flow-function curve during dipyridamole (i.e., fixed function [RWMS rest and dipyridamole 2.6 +/- 0.5] and no flow increase [rest 0.64 +/- 0.24 vs. dipyridamole 0.87 +/- 0.51, p = NS): Ischemic segments (n = 9) exhibited a downsloping flow-function curve during dipyridamole (i.e., worsened function [RWMS rest 2 +/- 0.5, dipyridamole 3.1 +/- 0.6] and no significant flow change [rest 0.67 +/- 0.29 vs. dipyridamole 0.79 +/- 0.23, p = NS]). CONCLUSIONS: Myocardial segments with rest dysfunction and a contractile reserve elicitable by a vasodilator stress more often exhibit residual flow reserve, whereas segments with a fixed or worsening mechanical response during stress show a flat flow response.

Aged↗
PubMed1997

Myocardial and forearm blood flow reserve in mild-moderate essential hypertensive patients.

BACKGROUND: Structural readaptation of systemic resistance-sized arterioles in response to an elevated blood pressure reduces the forearm vasodilator reserve in patients with essential hypertension. The development of a similar process at the coronary microvascular level has frequently been hypothesized, but little information about coronary remodeling during the uncomplicated stage of hypertension has been obtained, and the relationship with concomitant changes in forearm blood flow reserve is not known. OBJECTIVE: To assess the minimal myocardial resistance and its relationship with the minimal forearm resistance in a group of male patients with mild-to-moderate uncomplicated hypertension and carefully matched controls. MATERIAL AND METHODS: The minimal myocardial resistance (Rmin(myocardia), the mean arterial pressure: hyperemic myocardial flow ratio after administration of 0.84 mg/kg dipyridamole, measured by using positron emission tomography and [3N]-ammonia), minimal forearm vascular resistance (Rmin(forearm), a hemodynamic index of arteriolar structure derived from the mean blood pressure and maximal postischemic forearm blood flow by venous plethysmography), echocardiographic cardiac mass and wall thickness were measured in 25 male patients with mild-to-moderate uncomplicated essential hypertension, most of whom had previously been treated, and in seven sex- and age-matched normotensive controls. RESULTS: Rmin(myocardial) (and hyperemia: baseline myocardial flow ratios) did not differ significantly between the two groups, whereas Rmin(forearm) was significantly higher in hypertensives. There was no significant intra-individual correlation between the two parameters. The left ventricular mass index was greater in patients and was related previously to Rmin(forearm) but not to Rmin(myocardial) for the overall sample. In a subgroup analysis, Rmin(forearm) values were 2SD above control values in nine patients and within the normal range in the remaining 16. The myocardial reserve was very similar in the two subgroups. CONCLUSIONS: The myocardial vasodilator reserve appeared to be preserved in these mild-to-moderate uncomplicated hypertensive patients, whereas the forearm vasodilator capacity was reduced, suggesting that the hypertensive readaptation process was not distributed homogeneously over the two vascular beds.

Adaptation, Physiological↗
PubMed1997

Lipomatous metaplasia in left ventricular scar.

BACKGROUND AND OBJECTIVE: Substitution of interstitial tissue by fat may be observed in the right ventricle of hearts but is less common in the left ventricle. Fat was noted in myocardial scars of patients undergoing heart transplantation, prompting this retrospective study to determine the frequency of left ventricular myocardial scar being replaced by fat and its significance METHODS AND RESULTS: The left and right ventricles and coronary arteries were sampled systematically and lesions quantified histologically in 97 normal subjects dying accidentally; 116 consecutive failing hearts excised at transplantation from patients with ischemic heart disease, idiopathic dilated cardiomyopathy or chronic valvulopathy; and 34 autopsy hearts of apparently normal subjects with "silent' Chagas' heart disease who died suddenly and unexpectedly. Twenty-two left ventricular aneurysmectomy specimens from ischemic patients with heart failure were also studied. Among excised hearts lipomatous metaplasia of myocardial scar was observed in 68% of ischemic heart disease, in 37% of chronic valvulopathy and in 26% of idiopathic dilated cardiomyopathy patients; it was seen in 15% of Chagasic patients and in 55% of aneurysm walls. CONCLUSIONS: Lipomatous metaplasia of scar is often associated with severe heart failure and is more frequent and extensive in ischemic heart disease. Transformation of a compact scar into compressible and "sliding' adipose tissue may worsen ventricular wall function, thus facilitating and/or aggravating aneurysm formation. This phenomenon must be considered in the evaluation of myocardial repair, cardiac imaging of viable myocardium, quantitative morphology of autopsy specimens, and qualitative and quantitative biochemical analysis of myocardial tissue.

Adipose Tissue↗
PubMed1996

Temporal coding in vision: coding by the spike arrival times leads to oscillations in the case of moving targets.

The 'oscillations' which have been observed in the visual cortex of cats and monkeys in the case of moving targets are discussed in relation to a temporal coding based on the arrival times of spikes or bursts. A decoding process for this temporal coding is proposed in which neurons work in a correlator mode. In the case of motion analysis, periodic resetting is needed to avoid information jamming. This resetting is proposed to be responsible for the 'oscillations'. Good initial synchronization is required for the decoding process to be performed efficiently. A diffusive process based on interdendritic ionic currents is proposed and shown to operate efficiently, without any loss of spatial and temporal resolving powers.

Animals↗
PubMed1996

Morphological bases for thallium-201 uptake in cardiac imaging and correlates with myocardial blood flow distribution.

To determine the morphological bases of thallium-201 myocardial distribution in chronic cardiac dysfunction and their relation to myocardial blood flow, myocardial slices from ten excised hearts of five chronic ischaemic heart disease patients and five idiopathic dilated cardiomyopathy patients, were imaged on a gamma camera to quantitate the uptake of thallium-201, injected 4 h before surgery, and myocardial blood flow from distribution of technetium-99m-labelled human albumin microspheres injected during surgery. Tracer distribution was correlated with histologically assessed myocardial fibrosis and myocytolysis. Thallium-201 uptake was inversely related to fibrosis (r = -0.73, in ischaemic heart disease, r = -0.65 in idiopathic dilated cardiomyopathy). In ischaemic heart disease, myocardial blood flow was related neither to thallium-201 uptake (r = 0.41) nor to the extent of fibrosis (r = -0.48). In this group, segments with normal or mildly reduced thallium-201 uptake showed significantly lower fibrosis than those with moderate or severe uptake defects (5 +/- 7% and 7 +/- 11% vs 33 +/- 14% and 42 +/- 12%, respectively, P < 0.0001. In a clinical model of chronic ischaemic dysfunction, despite severely depressed myocardial blood flow, extensive areas of myocardium devoid of significant structural impairment are present. Thallium-201 uptake effectively discriminates regions with preserved viability from those with relevant myocardial damage.

Adult↗
PubMed1996

The role of coronary microvascular dysfunction in the genesis of cardiovascular diseases.

Positron emission tomography (PET) offers the unique capability of measuring specific flow (flow per unit of mass) in man by means of a regional, tridimensional, noninvasive approach. Using PET, myocardial perfusion abnormalities secondary to microvascular disorders have been investigated in arterial hypertension (AH), dilated and hypertrophic cardiomyopathy (CM), as well as in ischemic heart disease (CAD). In AH, regional perfusion at rest is within the normal range, while the coronary reserve and flow response to increase in metabolic demand are blunted. These flow abnormalities are independent of the degree of cardiac hypertrophy and the severity of AH; appropriate anti-ipertensive therapy is able to improve the perfusion abnormalities after long term treatment, independently of the effect on myocardial hypertrophy. Both dilated and hypertrophic CM demonstrate abnormal vasodilating capability, which has been shown to be present in the subclinical form of dilated DM; the reduction of coronary reserve is not related to the presence and extent of the hemodynamic impairment in dilated CM, and involves also nonhypertropied myocardium in asymmetric hypertrophic CM. These findings indicate a primary involvement of coronary microcirculation in non advanced forms of dilated and hypertrophic CM. Finally, in patients with CAD, myocardial territories supplied by angiographically normal coronary arteries show abnormal coronary reserve and flow during pacing tachycardia, indicating that, even in absence of epicardial coronary artery obstruction, microcirculation is impaired in subjects with coronary atherosclerosis. This abnormality can smooth perfusion differences between control and jeopardized regions. Accordingly, the absence of a perfusion defect during stress might indicate the presence of either a non significant stenosis or a diffuse impairment in microcirculatory function. Nuclear perfusion imaging with conventional perfusion tracers does not allow measurements of absolute blood flow, rather it provides an estimation of perfusion inhomogeneities. Although the agreement with the angiographic documentation of coronary artery disease has been frequently considered to characterize the diagnostic reliability of these techniques, the evaluation of myocardial perfusion provides an independent tool for the functional assessment of patient with heart disease. The possibility to obtain measurements of regional myocardial blood flow, provided by positron emission tomography, helps to identify the mechanisms affecting flow regulation in the myocardium. This tool thus provides a new rationale for the application of perfusion imaging, to obtain a more precise characterization of these patients, beyond the agreement with the morphological angiographic picture.

Arteriosclerosis↗