Iodine-123 Phenylpentadecanoic Acid Research Articles

Detection of septal ischemia with iodine 123-phenylpentadecanoic acid (p-IPPA) in patients with left bundle branch block

Detection of septal ischemia with iodine 123-phenylpentadecanoic acid (p-IPPA) in patients with left bundle branch block

Identification of viable myocardium in patients with chronic coronary artery disease and left ventricular dysfunction: Role of magnetic resonance imaging

Nineteen patients (16 men and 3 women, mean age 51 years) with previous anterior myocardial infarction and severe stenosis (≥90%) of the left anterior descending coronary artery were studied by magnetic resonance imaging (MRI) without and with contrast media to verify the capability of MRI in identifying viable myocardium in areas of severe systolic dysfunction. In corresponding left ventricular segments, a comparison was made between regional signal intensities (SI) determined on MRI images before and 4, 8, 12, and 30 minutes after administration of paramagnetic contrast media (gadolinium diethylenetriaminepentaacetic acid, 0.4 mmol/kg intravenously) and metabolic parameters determined by iodine 123 phenylpentadecanoic acid (IPPA) scintigraphy. The SI and the time of maximum postcontrast enhancement were analyzed by dividing the left ventricle into 11 segments. Each segment was classified as normal (group 1, n = 116), hibernating (group 2, n = 50), or necrotic (group 3, n = 43) on the basis of the IPPA washout rate (>30%, 10% to 30%, and <10%, respectively). Regional SI demonstrated significant differences in absolute values at 12 minutes (group 3: 1.62 ± 0.58 vs group 1: 1.32 ± 0.52, p < 0.01, and vs group 2: 1.34 ± 0.48, p < 0.05) and at 30 minutes (group 3: 1.71 ± 0.47 vs group 1: 1.21 ± 0.55, p < 0.01, and vs group 2: 1.49 ± 0.57, p < 0.05) and in temporal distribution. These results suggest that MRI has a potential role in differentiating viable from necrotic myocardium in patients with chronic severe systolic dysfunction.

Myocardial scintigraphy with iodine-123 phenylpentadecanoic acid and thallium-201 in patients with coronary artery disease: a comparative dual-isotope study

Myocardial scintigraphy with iodine-123 phenylpentadecanoic acid and thallium-201 in patients with coronary artery disease: a comparative dual-isotope study

Evaluation of myocardial viability with technetium-99m hexakis-2-methoxyisobutyl isonitrile and iodine-123 phenylpentadecanoic acid and single photon emission tomography.

The detection of viable myocardium in infarcted regions, i.e. hibernating myocardium, is a major goal in clinical cardiology today. We applied combined planar and single photon emission tomography (SPET) to the non-invasive estimation of the left ventricular ejection fraction (LVEF), myocardial blood flow and free fatty acid uptake in the heart. Of the 31 patients with coronary artery disease, 25 (81%) had had a previous myocardial infarction. All patients had at least one persistent perfusion defect on the stress-rest technetium-99m hexakis-2-methoxyisobutyl isonitrile (Sestamibi) study, and the results revealed 57/124 (46%) persistent perfusion defects. As a part of the perfusion study, the LVEF was measured at rest using the first-pass 99mTc-Sestamibi injection, and the mean LVEF was 47% +/- 9% (mean +/- 1 standard deviation). Iodine-123 phenylpentadecanoic acid (123I-pPPA) imaging at rest was performed within 2 weeks from the perfusion study. Then 6-mm transaxial, sagittal and coronal slices of the perfusion and 123I-pPPA studies were reconstructed. The bull's eye displays of the coronal slices were visually surveyed and divided into 4 quadrants: anterior, lateral, posterior and septal. The following image score was used: 0 = fixed defect, 1 = partial uptake and 2 = normal uptake. Moreover an index of metabolic reserve (MR) was calculated by dividing the bull's eye of the 123I-pPPA study by the bull's eye of resting 99mTc-Sestamibi, and its maximum value was normalized to 100%.(ABSTRACT TRUNCATED AT 250 WORDS)

Iodine-123 phenylpentadecanoic acid myocardial scintigraphy in patients with left ventricular hypertrophy: Alterations in left ventricular distribution and utilization

Regional alterations in myocardial substrate uptake and/or utilization have been demonstrated in rats with hypertension. To determine whether alterations in left ventricular fatty acid uptake and/or utilization are present in patients with left ventricular hypertrophy (LVH), we compared the results of rest and exercise iodine-123 phenylpentadecanoic acid (IPPA) myocardial scintigraphy in 10 patients with hypertension who had concentric LVH without evidence of coronary artery disease and in 15 normal subjects. Patients with LVH had more heterogeneous left ventricular activity of IPPA compared to normal subjects after exercise but not at rest (23 +/- 8% versus 13 +/- 5% difference in maximum segmental activity at 4 minutes after exercise; p = 0.005). Although IPPA clearance was similar in both patients with LVH and normal subjects, postexercise washout in segments showing decreased initial IPPA uptake was reduced compared to washout at rest in patients with LVH (11.7 +/- 7.5% versus 21.5 +/- 8.4% at 20 minutes after injection, n = 15; p = 0.005). Exercise thallium-201 (TI-201) scintigraphy was normal in all seven patients with LVH tested. Patients with LVH showed significantly greater heterogeneity in IPPA uptake compared to TI-201 uptake immediately after exercise (25 +/- 5% versus 16 +/- 6%; p = 0.013). We conclude that (1) compared to normal subjects, patients with LVH show heterogeneous myocardial IPPA activity after exercise but not at rest; (2) postexercise washout of IPPA was decreased in segments with reduced uptake after exercise in patients with LVH; and (3) the distribution of IPPA is more heterogeneous than that of TI-201 immediately after exercise in patients with concentric LVH. The postexercise heterogeneity in IPPA uptake and delayed washout in segments with reduced initial uptake is consistent with exercise-induced myocardial ischemia in patients with LVH.

New Radionuclide Agents for Cardiac Imaging: Description and Application

The introduction of three new radiopharmaceuticals into clinical research and practice has broadened the potential applications and scope of nuclear cardiology examinations. Technetium-99m labeled isonitrile perfusion agents have excellent imaging characteristics allowing the accurate identification of coronary artery disease. Simultaneous assessments of ventricular function are possible with these agents. Iodine-123 phenylpentadecanoic acid myocardial scintigraphy permits assessments of myocardial perfusion and fatty acid metabolism, and permits investigations of myocardial metabolism with conventional imaging equipment. Iodine-123 meta-iodobenzyl-guanidine serves as an indicator of the functional integrity of the sympathetic nervous system and permits evaluations of the effects of various disease states on catecholamine handling by the heart.

Estimation of jeopardized left ventricular myocardium in symptomatic and silent ischemia as determined by iodine-123 phenylpentadecanoic acid rotational tomography

Whether patients with silent myocardial ischemia have a lesser mass of ischemic myocardium than patients with symptomatic ischemia is controversial. Forty-five patients with angiographic coronary artery disease (≥70% luminal diameter narrowing) were studied. All patients had ischemic patterns of myocardial uptake and clearance of the long-chain fatty acid perfusion/metabolic imaging agent iodine-123 phenylpentadecanoic acid after maximal exercise. Single-photon emission computed tomography was performed and 25 myocardial segments were analyzed using circumferential activity profile curves. The 21 patients with silent treadmill ischemia exercised longer than the 24 patients with painful treadmill ischemia (430 ± 137 vs 337 ± 96 seconds, p < 0.01) and to a higher heart rate (138 ± 21 vs 125 ± 18 beats/min, p < 0.05). Patients with treadmill silent ischemia had the same number of abnormally perfused myocardial segments as patients with painful treadmill ischemia (8.6 ± 4.5 vs 6.5 ±4.1 segments, difference not significant) and the same number of reversibly ischemic myocardial segments (4.0 ± 1.4 vs 4.2 ± 3.0 segments, difference not significant). The angiographic severity and extent of coronary artery disease were similar in the 2 groups. Thus, in this selected group of patients, those with silent treadmill ischemia appear to have at least as great an extent of ischemic myocardium as patients with painful exertional ischemia.

Abnormal myocardial fatty acid metabolism in dilated cardiomyopathy detected by iodine-123 phenylpentadecanoic acid and tomographic imaging

The radioiodinated synthetic fatty acid iodine-123 Phenylpentadecanoic acid (IPPA) has proven useful in the identification of regional abnormalities of cardiac metabolism in patients with myocardial ischemia. The present study was performed to test the hypothesis that the myocardial distribution and turnover of fatty acids, assessed noninvasively with IPPA, are altered in patients with cardiomyopathy. Nine normal volunteers and 19 patients with dilated cardiomyopathy of various etiologies underwent cardiac imaging with single-photon emission computed tomography (SPECT) after intravenous injection of IPPA. Apical short-axis and basal short-axis sections were reconstructed and quantitatively analyzed for relative IPPA activity distribution and washout. Patients with congestive cardiomyopathy demonstrated significantly greater heterogeneity of IPPA uptake than normal subjects (maximal percent variation of activity 27 ± 11 vs 18 ± 4, p < 0.01). They also demonstrated a more rapid percent washout rate than control subjects (24 ± 8 vs 17 ± 6 for the apical short-axis section, p < 0.05; 26 ± 7 vs 18 ± 5 for the basal short-axis section, p < 0.01). These abnormalities of fatty acid distribution and turnover were independent of the etiology of the cardiomyopathy. The degree of heterogeneity of IPPA uptake was significantly related to the patients' New York Heart Association functional class (r = 0.64, p < 0.01). Thus, compared with normal myocardium, the myocardium of patients with congestive cardiomyopathy demonstrates a more heterogeneous distribution of fatty acid uptake, which parallels the clinical severity of the disease. Furthermore, patients with congestive cardiomyopathy demonstrate a more rapid myocardial clearance of the labeled fatty acid, as assessed with SPECT imaging.

Iodine-123 phenylpentadecanoic acid and single photon emission computed tomography in identifying left ventricular regional metabolic abnormalities in patients with coronary heart disease: Comparison with thallium-201 myocardial tomography

Iodine-123 phenylpentadecanoic acid (IPPA) is a synthetic long chain fatty acid with myocardial kinetics similar to palmitate. Two hypotheses were tested in this study. The first hypothesis was that IPPA imaging with single photon emission computed tomography (SPECT) is useful in the identification of patients with coronary artery disease. Fourteen normal volunteers (aged 27 ± 2 years) and 33 patients (aged 54 ± 11 years) with stable symptomatic coronary artery disease and at least one major coronary artery with luminal diameter narrowing ≥70% were studied with symptom-limited maximal exercise testing. The IPPA (6 to 8 mCi) was injected 1 min before the termination of exercise, and tomographic imaging was performed beginning at 9 min and repeated at 40 min after the injection of IPPA. Nine of the normal volunteers and 13 of the patients had a second examination performed at rest on another day.Using the limits of normal as 2 SD from the normal mean values, 27 of the 33 patients with coronary artery disease demonstrated abnormalities in either the initial distribution or the clearance of IPPA, or both. Nineteen of the 33 patients had a maximal variation of activity distribution of ≥ 25% on the 9 min IPPA images. Twenty-two of the 33 patients had a maximal variation in IPPA washout >17% and 17 had a washout rate ≤2%. There was good agreement between the location of significant coronary artery stenoses and abnormalities in the initial distribution and clearance of IPPA.The second hypothesis tested was that IPPA imaging is as or more sensitive and, therefore, complementary to thallium-201 imaging in the identification of exercise-induced ischemia in patients. Twenty-five of the 33 patients underwent both thallium-201 and IPPA tomographic imaging after symptom-limited maximal exercise testing. The amount of exercise performed by each patient during both studies was shnilar. Twenty-one of the 25 patients had abnormal IPPA tomographic studies, whereas 18 had abnormal thallium-201 tomographic studies (p = NS).The results of this study suggest the following conclusions: 1) iodine-123 phenylpentadecanoic acid imaging using single photon emission computed tomography and exercise provides a sensitive and relatively noninvasive method for identifying abnormalities in myocardial metabolism associated with significant coronary artery stenoses, and 2) iodine-123 phenylpentadecanoic acid is at least as sensitive as thallium-201 for this purpose using tomographic imaging and exercise testing.

Iodine-123 phenylpentadecanoic acid: Detection of acute myocardial infarction and injury in dogs using an iodinated fatty acid and single-photon emission tomography

The ability of an iodinated fatty acid, iodine-123 Phenylpentadecanoic acid (1–123 PPA), and single-photon emission computed tomography (SPECT) to detect myocardium injured by temporary or permanent coronary arterial occlusion was evaluated. In 5 control dogs, 11 dogs that underwent 90 to 120 minutes of fixed left anterior descending coronary artery (LAD) occlusion, and 8 dogs that underwent 90 minutes of temporary LAD occlusion and up to 90 minutes of reflow, 2 to 6 mCi of 1–123 PPA were injected and the dogs were imaged with SPECT. Control dogs showed relatively uniform uptake and clearance of 1–123 PPA in similar left ventricular (LV) regions. Dogs with permanent LAD occlusion were identified by computer algorithm as having regions of decreased 1–123 PPA uptake in the infarct-related area and a reduced rate of 1–123 PPA clearance (−9.4% in infarct sectors [washin], +3.7% in sectors adjacent to the area of infarction, and +15.4% in control LV sectors [p <0.01]). Dogs with temporary LAD occlusion and reperfusion had decreased clearance of 1–123 PPA from the regions with infarction; 1–123 PPA clearance was −5.2 ± 16.4% in infarct sectors, 12.7 ± 7.4% in periinfarct zones, and 30.4 ± 12% in control LV regions. These data demonstrate that tomographic analysis of 1–123 PPA uptake and clearance permits the relatively noninvasive detection of LV myocardium injured by permanent or temporary LAD occlusion and reperfusion.