Ronaldo de Souza Leão Lima

Prevalence and Prognostic Value of Perfusion Defects Detected by Stress Technetium-99m Sestamibi Myocardial Perfusion Single-Photon Emission Computed Tomography in Asymptomatic Patients With Diabetes Mellitus and No Known Coronary Artery Disease

Coronary artery disease (CAD) is the leading cause of morbidity and mortality in diabetics. Early diagnosis of CAD and identification of high-risk subgroups, followed by appropriate therapy, may therefore enhance survival. This study sought to determine the value of stress myocardial perfusion single-photon emission computed tomography (SPECT) with technetium-99m sestamibi to detect perfusion defects and predict cardiac events in asymptomatic diabetics. One hundred eighty asymptomatic diabetics without known CAD who underwent 2-day stress technetium-99m sestamibi SPECT were followed up for 36 +/- 18 months. End points were defined as hard (myocardial infarction or cardiac death) or total events (myocardial infarction, cardiac death, or late revascularization). Logistic regression analysis evaluated clinical variables, type of stress, exercise treadmill test (ETT), and SPECT as predictors of end points. Perfusion defects were found in 26% of patients (15% reversible, 6% mixed, and 5% fixed). Clinical or ETT variables were not associated with perfusion defect type or with hard events. However, male gender predicted total events (chi-square 3.3; p = 0.01). An abnormal SPECT significantly increased the risk of hard events (chi-square 5.4; p = 0.001) and total events (chi-square 7.4; p = 0.0001). Extensive defects determined the highest risk of total events (chi-square 18.8; p = 0.0001). Event rates increased according to SPECT: 2% of hard events per year and 5% of total events per year in patients with normal SPECT versus 9% per year and 38% per year, respectively, in those with abnormal SPECT. Importantly, a normal SPECT identified a relatively low-risk subgroup of patients. Thus, stress technetium-99m sestamibi SPECT was useful in evaluating asymptomatic diabetics for the presence of CAD, and effectively risk-stratified this population.

Incremental prognostic value of myocardial perfusion 99m-technetium-sestamibi SPECT in the elderly

Coronary artery disease (CAD) is the main cause of death in elderly patients. Single-photon emission computed tomography (SPECT) with technetium-99m ((99m)Tc)-labeled agents is extremely useful for the diagnosis and risk stratification of CAD in the general population. However, its prognostic value for the elderly has not been established. This study examined disease outcome in 328 patients aged 74 or older, with suspected CAD who were submitted to either pharmacological (dipyridamole) or exercise stress SPECT with (99m)Tc-sestamibi, seven of whom were completely lost to follow-up. Endpoints were defined as hard (myocardial infarction or cardiac death) or total events (myocardial infarction, cardiac death or myocardial revascularization). Mean follow-up was 34+/-15 months. During this period 24 cardiac deaths, 11 myocardial infarctions and 21 cases of revascularization were observed. Perfusion defects were found in 27.1% of patients (12.8% reversible, 6.2% partially reversible and 8.1% fixed). Abnormal studies were predominant in men, patients with chest pain and those with ST-T abnormalities in the baseline electrocardiogram (ECG) or in the exercise treadmill test. An abnormal scan was significantly associated with cardiac events (P<0.0001). Multivariate analysis revealed that a abnormal scan was the most important independent predictor of hard or total cardiac events. Event rates increased according to myocardial perfusion scintigraphy (MPS): <1.0% of hard events per year in patients with normal MPS versus 14.3% per year in those with abnormal MPS. (99m)Tc-sestamibi SPECT was demonstrated to be a powerful tool for the prognostic evaluation of elderly patients with suspected CAD.

PET/CT and vascular disease: current concepts.

Since its introduction in 2001, positron emission tomography associated to computed tomography (PET/CT) has been established as a standard tool in cancer evaluation. Being a multimodality imaging method, it combines in a single session the sensitivity granted by PET for detection of molecular targets within the picomolar range, with an underlying submilimetric resolution inherent to CT, that can precisely localize the PET findings. In this last decade, there have been new insights regarding the pathophysiology of atherosclerosis, particularly about plaque rupture and vascular remodeling. This has increased the interest for research on PET/CT in vascular diseases as a potential new diagnostic tool, since some PET molecular targets could identify diseases before the manifestation of gross anatomic features. In this review, we will describe the current applications of PET/CT in vascular diseases, emphasizing its usefulness in the settings of vasculitis, aneurysms, vascular graft infection, aortic dissection, and atherosclerosis/plaque vulnerability. Although not being properly peripheral vascular conditions, ischemic cardiovascular disease and cerebrovascular disease will be briefly addressed as well, due to their widespread prevalence and importance.

Biodistribution of bone marrow mononuclear cells in chronic chagasic cardiomyopathy after intracoronary injection

BACKGROUND Animal and human clinical studies have indicated that bone marrow (BM) mononuclear cell (MNC) therapy for Chagasic Cardiomyopathy (ChC) is feasible, safe and potentially efficacious. Nevertheless, little is known about the retention of these cells after intracoronary (IC) infusion. METHODS Our study investigated the homing of technetium-99m ((99m)Tc) labeled BM MNCs and compared it to thallium-201 ((201)Tl) myocardial perfusion images using the standard 17-segment model. Six patients with congestive heart failure of chagasic etiology were included. RESULTS Scintigraphic images revealed an uptake of 5.4%±1.7, 4.3%±1.5 and 2.3%±0.6 of the total infused radioactivity in the heart after 1, 3 and 24h, respectively. The remaining activity was distributed mainly to the liver and spleen. Of 102 segments analyzed, homing took place in 36%. Segments with perfusion had greater homing (58.6%) than those with decreased or no perfusion (6.8%), p<0.0001. There was no correlation between the number of injected cells and the number of segments with homing for each patient (r=-0.172, p=0.774). CONCLUSIONS These results indicate that (99m)Tc-BM MNCs delivered by IC injection homed to the chagasic myocardium. However, cell biodistribution was heterogeneous and limited, being strongly associated with the myocardial perfusion pattern at rest. These initial data suggest that the IC route may present limitations in chagasic patients and that alternative routes of cell administration may be necessary.

Influence of chronic renal failure on the heart rate response to dipyridamole in patients undergoing myocardial perfusion SPECT

BackgroundDipyridamole promotes a reduction in blood pressure and an increase in heart rate (HR), considered the normal hemodynamic response to the drug. Data suggest that patients with chronic renal failure (CRF) have an attenuation of this hemodynamic response. This study sought to evaluate the HR response to dipyridamole and its determinants in patients with or without CRF undergoing gated myocardial perfusion single photon emission computed tomography.Methods and ResultsConsecutive patients (n=355, 9,6% with CRF) undergoing rest/dipyridamole myocardial perfusion single photon emission computed tomography were evaluated. The HR response to dipyridamole was considered to be reduced if the HR ratio (maximal HR/rest HR) was 1.20 or less. A logistic regression analysis determined independent predictors of a blunted HR response. A reduced HR response was found in 84.4% of patients with CRF and 40.6% of those without CRF (P<.0001). In patients without CRF the independent predictors of abnormal HR response were hypertension, rest and differential perfusion scores, and left ventricular ejection fraction. In contrast, in CRF patients there was no significant association of any of the studied variables with abnormal HR response.ConclusionsAn abnormal HR response to dipyridamole is frequently found in patients with CRF. Different mechanisms may account for abnormal HR response in patients with or without CRF.

Comparison between short-acquisition myocardial perfusion SPECT reconstructed with a new algorithm and conventional acquisition with filtered backprojection processing.

ObjectiveTo compare a novel reconstruction package (Evolution for Cardiac), used to improve image quality in myocardial perfusion single photon emission computed tomography (MPS) and enable shorter scan acquisitions, to filtered backprojection used for conventional time acquisitions. MethodsForty-four patients who underwent 2-day Tc-99m sestamibi MPS had both standard [SD: 14-min scan and filtered backprojection processing] and short (SH: 6-min scan and iterative reconstruction with Evolution for Cardiac) studies. In a 17-segment model of the left ventricle, each segment was automatically scored 0–4 (normal to absent radiotracer activity); summed stress, rest and difference scores (SSS, SRS, SDS) were obtained. Spearmans test assessed the correlation between scores from SD and SH studies, and Bland–Altman plots evaluated absolute and mean differences of scores between these studies. ResultsThe SSS, SRS, and SDS were not statistically different between SD and SH studies (SSS: 5.9±6.6 vs. 5.8±6.5; SRS: 2.6±3.5 vs. 2.6±2.9; SDS: 3.3±5.8 vs. 3.2±5.7). Significant correlations were observed between SD and SH studies regarding SSS (R2=0.93), SRS (R2=0.85), and SDS (R2=0.9) (all P<0.001). Bland–Altman plots showed that differences in SSS, SRS, and SDS fell within 2 standard deviations of the average differences between SD and SH studies. Overall agreement between clinical readings of SD and SH scans was good (up to 100% in abnormal scans). ConclusionA new reconstruction package (Evolution for Cardiac) enabled short MPS acquisition without changes in quantitative perfusion results when compared with conventional acquisition and processing.

Comparison of the prognostic value of myocardial perfusion imaging using a CZT-SPECT camera with a conventional anger camera

BackgroundRecent studies have shown that myocardial perfusion imaging (MPI) in cadmium-zinc-telluride (CZT) cameras allow faster exams with less radiation dose but there are little data comparing its prognosis information with that of dedicated cardiac Na-I SPECT camerasObjectiveThe objective of this study is to compare the prognostic value of MPI using an ultrafast protocol with low radiation dose in a CZT-SPECT and a traditional one.MethodsGroup 1 was submitted to a two-day MIBI protocol in a conventional camera, and group 2 was submitted to a 1-day MIBI protocol in CZT camera. MPI were classified as normal or abnormal, and perfusion scores were calculated. Propensity score matching methods were performedResults3554 patients were followed during 33±8 months. Groups 1 and 2 had similar distribution of age, gender, body mass index, risk factors, previous revascularization, and use of pharmacological stress. Group 1 had more abnormal scans, higher scores than group 2. Annualized hard events rate was higher in group 1 with normal scans but frequency of revascularization was similar to normal group 2. Patients with abnormal scans had similar event rates in both groupsConclusionNew protocol of MPI in CZT-SPECT showed similar prognostic results to those obtained in dedicated cardiac Na-I SPECT camera, with lower prevalence of hard events in patients with normal scan.

Reduced heart rate response to dipyridamole as a marker of left ventricular dysfunction in diabetic patients undergoing myocardial perfusion scintigraphy.

Purpose of the Report: This study sought to find among clinical, hemodynamic and left ventricular perfusion and function data obtained from myocardial perfusion scintigraphy (MPS), those associated with a reduced heart rate (HR) response to dipyridamole in diabetic patients. This phenomenon, although previously described as a marker of autonomic dysfunction in patients with diabetes, has not been fully elucidated. Materials and Methods: One hundred two consecutive diabetic patients undergoing dual-isotope (rest Tl-201/dipyridamole stress Tc-99m tetrofosmin) MPS were prospectively enrolled. A reduced HR response to dipyridamole was considered present if the ratio between maximal HR after dipyridamole infusion and rest HR was ≤1.20. MPS images were interpreted semiquantitatively, and perfusion scores were calculated. Left ventricular ejection fraction (LVEF) was automatically obtained. A logistic regression analysis was used to find variables independently associated with a reduced HR response to dipyridamole. Results: A reduced HR response to dipyridamole was found in 46.1% of the patients and was associated with the presence of chronic renal failure (&khgr;2 = 6.4), with high baseline HR (&khgr;2 = 4.7) and low poststress LVEF (&khgr;2 = 10.6). Conclusions: Attenuation of the HR response to dipyridamole was frequent and was strongly associated with reduced LVEF. Autonomic dysfunction may be reflected in the higher baseline HR but should not be considered the sole mechanism accounting for the reduction in HR response to dipyridamole in patients with diabetes.

Pesquisa de viabilidade miocárdica

A pesquisa de viabilidade miocardica em pacientes portadores de disfuncao ventricular esquerda tem grande impacto para a tomada de decisao terapeutica nesse tipo de paciente, pois permite identificar aqueles que mais se beneficiarao de procedimentos de revascularizacao, tanto cirurgicos quanto por angioplastia percutânea. Alem disso, apresenta impacto economico, pois seleciona pacientes nos quais a revascularizacao nao melhora o prognostico, conforme demonstrado pela metanalise de Allman et al.. A identificacao do musculo viavel pode ser feita por diferentes tecnologias, sendo as mais importantes a cintilografia miocardica, a ecocardiografia de estresse, a tomografia por emissao de positrons e a ressonância magnetica. O uso do talio-201 na cintilografia miocardica, por ser um analogo do potassio, depende da existencia da integridade da membrana celular para sua captacao pelo miocito. Por essa razao, esse radiotracador permite a identificacao de viabilidade miocardica mesmo com quantidades reduzidas de musculo vivo. Esse fato provavelmente justifica a sensibilidade alta apresentada por essa tecnica para identificar a recuperacao da contratilidade apos revascularizacao. No entanto, a sua especificidade e inferior a apresentada pela ecocardiografia de estresse com dobutamina, principalmente quando se encontra a resposta bifasica, ou seja, ha uma melhora inicial da contratilidade em segmentos hipoe acineticos com dose baixa de dobutamina, mas que voltam a piorar com doses mais elevadas desse farmaco. Com a introducao do gated SPECT, a cintilografia miocardica, principalmente com sais ligados ao Tc, pode avaliar simultaneamente a perfusao, a contratilidade global e segmentar e os volumes sistolicos e diastolicos

Real-time cardiac magnetic resonance cine imaging with sparse sampling and iterative reconstruction for left-ventricular measures: Comparison with gold-standard segmented steady-state free precession.

BACKGROUND Segmented cine imaging with a steady-state free-precession sequence (Cine-SSFP) is currently the gold standard technique for measuring ventricular volumes and mass, but due to multi breath-hold (BH) requirements, it is prone to misalignment of consecutive slices, time consuming and dependent on respiratory capacity. Real-time cine avoids those limitations, but poor spatial and temporal resolution of conventional sequences has prevented its routine application. We sought to examine the accuracy and feasibility of a newly developed real-time sequence with aggressive under-sampling of k-space using sparse sampling and iterative reconstruction (Cine-RT). METHODS Stacks of short-axis cines were acquired covering both ventricles in a 1.5T system using gold standard Cine-SSFP and Cine-RT. Acquisition parameters for Cine-SSFP were: acquisition matrix of 224×196, temporal resolution of 39ms, retrospective gating, with an average of 8 heartbeats per slice and 1-2 slices/BH. For Cine-RT: acquisition matrix of 224×196, sparse sampling net acceleration factor of 11.3, temporal resolution of 41ms, prospective gating, real-time acquisition of 1 heart-beat/slice and all slices in one BH. LV contours were drawn at end diastole and systole to derive LV volumes and mass. RESULTS Forty-one consecutive patients (15 male; 41±17years) in sinus rhythm were successfully included. All images from Cine-SSFP and Cine-RT were considered to have excellent quality. Cine-RT-derived LV volumes and mass were slightly underestimated but strongly correlated with gold standard Cine-SSFP. Inter- and intra-observer analysis presented similar results between both sequences. CONCLUSIONS Cine-RT featuring sparse sampling and iterative reconstruction can achieve spatial and temporal resolution equivalent to Cine-SSFP, providing excellent image quality, with similar precision measurements and highly correlated and only slightly underestimated volume and mass values.