The value of local normal limits in quantitative Thallium-201 CZT MPI SPECT.

Background: Considering the distinctive characteristics of CZT detectors, automatic quantification of ischemia using normal limits included with software package may deliver suboptimal results for CAD detection. The present study aims to evaluate the benefits of creating normal limits specific to a local population and laboratory protocol.

Methods And Results: Two groups were selected from patients who had undergone a CZT MPI.

Clinical validation of the planar radionuclide ventriculography in patients with right ventricular dysfunction.

Objectives: Gated radionuclide ventriculography (RNV) may be used for the evaluation of the right ventricular function. However, the accuracy of the method should be clinically validated in patients suffering from diseases with specific pathology of the right ventricle (RV) and with possible left ventricular (LV) interaction.

Methods: Three groups of 15 patients each, diagnosed with arrhythmogenic right ventricular dysplasia (ARVD), pulmonary artery hypertension (PAH) or atrial septal defect (ASD) were compared to a group of normal subjects.

Scintigraphic spectrum of a patient population with suspected arrhythmogenic right ventricular dysplasia.

Gated radionuclide ventriculography (RNV), combined with inter- and intraventricular dyssynchrony measurement by phase analysis, is able to evidence right and left ventricular mechanical cardiac disorders and may contribute to the diagnosis of arrhythmogenic right ventricular dysplasia (ARVD). Nevertheless, the patients referred for suspicion of ARVD on the basis of symptoms, electrical abnormalities or family history of sudden death, are very heterogeneous and the examination findings spread out from strictly normal to severely abnormal. In order to describe the patient population encountered in "real life" we propose to use an automatic clustering method based on RNV results in order to segment the overall population into subgroups with coherent scintigraphic data in each one.

Quantification of ventricular resynchronization reserve by radionuclide phase analysis in heart failure patients: a prospective long-term study.

Background: Phase analysis, developed to assess dyssynchrony from ECG-gated radionuclide ventriculography, has shown promising results. We hypothesized that quantifying the cardiac resynchronization reserve, that is, the extent of response to cardiac resynchronization therapy (CRT), by radionuclide imaging could potentially identify patients who are best suited for CRT.

Methods And Results: Seventy-four patients ages 64.

Long-term benefit of postconditioning.

Background: We previously demonstrated that ischemic postconditioning decreases creatine kinase release, a surrogate marker for infarct size, in patients with acute myocardial infarction. Our objective was to determine whether ischemic postconditioning could afford (1) a persistent infarct size limitation and (2) an improved recovery of myocardial contractile function several months after infarction.

Methods And Results: Patients presenting within 6 hours of the onset of chest pain, with suspicion for a first ST-segment-elevation myocardial infarction, and for whom the clinical decision was made to treat with percutaneous coronary intervention, were eligible for enrollment.

Preconditioning during coronary angioplasty: no influence of collateral perfusion or the size of the area at risk.

Aims: It is unclear whether the protection observed in human heart following repetition of brief episodes of ischaemia is due to opening of coronary collaterals or to ischaemic preconditioning. We investigated whether the improvement in ST segment change following repeated episodes of brief ischaemia during coronary angioplasty is due to preconditioning when the size of the area at risk and the collateral flow are taken into account.

Methods And Results: Thirty-six patients underwent percutaneous transluminal coronary angioplasty.

Non-invasive testing of acquired long QT syndrome: evidence for multiple arrhythmogenic substrates.

Background: Although well-defined clinically and electrocardiographically, Acquired Long QT Syndrome (LQTS) remains elusive from a pathophysiologic point of view. An increasingly accepted hypothesis is that it represents an attenuated form of Congenital Long QT Syndrome. To test this hypothesis further, we investigated patients with Acquired LQTS, using various investigations that are known to give information in patients with Congenital LQTS.

Three-dimensional automatic image warping in cardiac SPECT.

This study presents a new tool for the visualization and analysis of three-dimensional (3-D) cardiac single-photon emission computed tomography (SPECT). The first step consisted of computing the 3-D pseudo-skeleton of a binarized myocardium and, using the skeleton points, to design a bullet model (half ellipsoid prolonged by a cylinder). Afterwards, this model was used to drive the warping of the 3-D myocardium, initially egg-shaped, into a thick, flat disc using the thin-plate splines as deformation method.

In vivo measurement of myocardial oxidative metabolism and blood flow does not show changes in cancer patients undergoing doxorubicin therapy.

Purpose: The aim was to investigate in patients receiving doxorubicin whether any alteration in myocardial oxidative metabolism or blood flow as assessed by positron emission tomography (PET) could be observed either after the first dose of the drug, or during its chronic administration.

Methods: Six female non-heart-failure cancer patients treated with doxorubicin were included in a longitudinal study. Resting radionuclide cineangiography and PET scanning with carbon-11 acetate were performed the day before the initiation of doxorubicin treatment at a dosage of 50 mg/m2 every 3 weeks, and 3 weeks after the cumulative administration of 300 mg/m2 (chronic toxicity).

Severity and extent of perfusion defects provoked by transient coronary occlusion compared with myocardial damage observed after infarction.

A peripheral perfusion tracer injection at the time of coronary occlusion during percutaneous transluminal coronary angioplasty (PTCA) may delineate the myocardial 'area at risk' related to a given artery. To evaluate the location, size and severity of the corresponding scintigraphic defects, we conducted a prospective study of 36 patients who received a 99Tcm-sestamibi injection during single-vessel coronary angioplasty (PTCA = 18 LAD, 16 RCA and 2 LCX) followed by SPET. For comparison, a reference group of 36 successive patients examined during the early phase of myocardial infarction (MI), matched for the same vascular territories (18 anterior, 16 inferior and 2 lateral), were analysed in the same way after standard stress/reinjection 201Tl SPET.

Gated blood-pool SPECT evaluation of changes after radiofrequency catheter ablation of accessory pathways: evidence for persistent ventricular preexcitation despite successful therapy.

Objectives: This study was designed to prospectively evaluate the effects of radiofrequency ablation in Wolff-Parkinson-White (WPW) syndrome by scintigraphic analysis.

Background: The functional changes triggered by radiofrequency current ablation of atrioventricular accessory pathways are not fully known.

Methods: Forty-four patients with WPW syndrome were consecutively investigated before and 48 h after radiofrequency therapy.

Two-year assessment by exercise thallium scintigraphy of myocardial revascularization using bilateral internal mammary and gastroepiploic arteries.

Objective: To assess the blood flow supply offered to the myocardium by surgical revascularization using bilateral internal mammary (IMAs) and gastroepiploic (GEA) arteries.

Methods: Two-year assessment by exercise thallium myocardial scintigraphy without medical treatment was performed in 122 patients (mean age 61 +/- 9 years) who underwent coronary artery bypass grafting (CABG) with exclusive use of IMAs and GEA. Usually, the right IMA was used to bypass the left anterior descending coronary artery, and the left IMA to bypass the diagonal and the marginal arteries as a sequential graft if required.

Effects of lipid-lowering drugs on left ventricular function and exercise tolerance in dyslipidemic coronary patients.

Previous studies suggested that certain lipid-lowering drugs such as statins suppress ubiquinone, affect mitochondrial function, and may have deleterious effect on skeletal or cardiac muscles with potentially serious clinical consequences, especially in patients with established coronary heart disease and left ventricular dysfunction. In this double-blind study, we assessed the effects of 20 mg simvastatin (S, n = 32) or 200 mg micronized fenofibrate (F, n = 32, control group) on rest and exercise left ventricular function in hypercholesterolemic survivors of a previous Q-wave acute myocardial infarction. Left ventricular radionuclide imaging was performed at rest and during submaximal exercise and global and segmental (nine segment regional wall-motion score) ejection fractions were measured before treatment and 12 weeks later.

Does the extended use of arterial grafts compromise the myocardial recovery after coronary artery bypass grafting in left ventricular dysfunction?

Objective: To assess the prognostic factors of myocardial recovery expected after coronary bypass surgery and the impact of surgical technique used, a prospective non-randomized study including a 1-year postoperative evaluation of left ventricular function was performed in patients with left ventricular dysfunction (left ventricular ejection fraction (LVEF) < 0.40).

Methods: From 1993 to 1996, 110 patients (mean age 61+/-11 years) were included in the study.

Theoretical model for myocardial functional characterization: application to a group of patients evaluated before and after surgical revascularization.

Background: The functional improvements resulting from coronary revascularization (CABG) in patients with depressed ventricular function may be described by the use of a model combining global or local quantification of myocardial perfusion, viability, and contraction. An illustration of this model, with data provided by conventional radionuclide studies as they are performed routinely in many centers, is presented and the limitations of this approach for predicting the results of CABG are discussed.

Methods And Results: The model is based on three independent variables, which can be approximated in this preliminary study by parameters derived from standard stress and redistribution/reinjection thallium-201 single-photon emission computed tomography (SPECT) acquisitions with quantification of the tracer uptake defects and from a planar gated blood pool left ventricular ejection fraction (LVEF) measurement: Perfusion is assumed to correspond to 100-stress defect (in percentage), viability is 100-redistribution/reinjection defect, and contraction is 100(LVEF/70), assuming that a normal 70% LVEF corresponds to 100% contraction.

Assessment of left ventricular stiffness and compliance.

Invasive and non-invasive methods exist to assess left ventricular compliance (LVC). This work has two parts, one experimental and one clinical. We estimated left chamber stiffness in dogs by using volume data from radionuclide ventriculography (RNV) and left ventricular pressure data, synchronized with a gating system to the intraventricular dp/dt max to obtain volume and pressure data from a mean cardiac cycle.

[Role of isotope methods in the evaluation of cardiac function in intensive care].

Radioisotopic cardiac investigation techniques still have a limited role in intensive care units, mainly due to cumbersome traditional equipment, even if in some cases favourable local circumstances exist, such as the proximity of a nuclear medicine unit or the availability of a mobile gamma camera. Nevertheless, nuclear techniques show a number of interesting features, mainly related to the fact that measurements of cardiac chamber volumes and of their variations can be directly derived from activity counts, without any geometrical hypothesis as it is necessary for other methods such as contrast angiography or echocardiography. The whole cardiac cycle (its systolic part as well as its diastolic part) can therefore be evaluated.

Clinical experience with technetium-99m teboroxime scintigraphy in patients referred for myocardial perfusion evaluation.

A series of 30 patients (25 males, 5 females, age = 28-73 years) with a clinical indication of thallium-201 stress/4 hours redistribution scintigraphy has been studied using stress/rest (n = 7) or rest/stress (n = 23) protocols with technetium-99m teboroxime (CARDIOTEC, Squibb Diagnostics) in order to assess the clinical usefulness of this new molecule and to compare it to thallium. In all cases coronary artery disease was known or highly suspected, with a history of myocardial infarction in 18 cases (subacute n = 6, remote n = 12) and/or previous by-pass surgery or PTCA in 5 cases. Medical treatment was not discontinued at the time of stress testing.

Technetium-99m teboroxime scintigraphy. Clinical experience in patients referred for myocardial perfusion evaluation.

In order to evaluate the clinical value of a new myocardial perfusion tracer, a series of 30 patients (25 male, 5 female, mean age 56 years) referred for thallium 201 stress/redistribution scintigraphy has been studied using stress/rest (n = 7) or rest/stress (n = 23) protocols with technetium 99m teboroxime (Cardiotec SQUIBB). In all cases coronary artery disease was known or highly probable, with a history of myocardial infarction in 18 cases. Medical treatment was not discontinued at the time of stress testing, and coronary angiography was available in 27 patients.

Assessment of chest pain by nuclear cardiology techniques.

This article reviews the nuclear cardiology techniques which can be used to assess chest pain. Nuclear techniques can potentially give valuable information on the location and extent of myocardial perfusion abnormalities, the assessment of myocardial viability, and/or presence of myocardial necrosis and the effects, both regional and global, of myocardial ischemia on myocardial function. The article reviews specific tests available and their indications and indicates the usefulness of these techniques for the clinician managing myocardial ischemia.

A new experimental model for studies of drug actions on myocardial metabolism. Application to a study of the influence of POCA.

In order to study myocardial metabolism by external detection, quantitative information on the metabolism of a gamma-emitting iodinated fatty acid (IHA) was obtained from time-activity curves of radioactivity in different compartments. A 4-compartment mathematical model was then developed; compartments 0, 1, 2, and 3 correspond respectively to vascular IHA, intracellular IHA, esterified forms, and iodide resulting from mitochondrial oxidation of IHA. We applied this model to a study of the influence of an inhibitor of fatty acid oxidation, POCA (2-[5(4 chlorophenyl) pentyl]-oxirane-2-carboxylate).

Mathematical model of the metabolism of 123I-16-iodo-9-hexadecenoic acid in an isolated rat heart. Validation by comparison with experimental measurements.

The aim of the present study was to demonstrate that it is possible to estimate the intracellular metabolism of a fatty acid labelled with iodine using external radioactivity measurements. 123I-16-iodo-9-hexadecenoic acid (IHA) was injected close to the coronary arteries of isolated rat hearts perfused according to the Langendorff technique. The time course of the cardiac radioactivity was measured using an INa crystal coupled to an analyser.

Kinetics of (16 123I) iodohexadecenoic acid metabolism in the rat myocardium, influence of glucose concentration in the perfusate and comparison with (1 14C) palmitate.

External counting, intracellular and subcellular distribution of (16 123I) iodohexadecenoic acid are studied on isolated rat hearts perfused with or without glucose. The presence of an exogenous substrate reduces the fatty acid oxidation and induces an increase of total cardiac and organic fraction activities. In this fraction, activity is very low for free fatty acids, but high for triglycerides and especially for polar lipids.

Influence on the myocardial and blood activity course of the characteristics of the labelled fatty acid injected i.v. into mice.

In order to choose a labelled fatty acid (FA) for the external study of myocardial metabolism, FAs that are different in chain length, saturation, nature and position of the radioactive label, are injected i.v. into mice.