Cardiac resynchronization therapy evaluated by myocardial scintigraphy with 99mTc-MIBI: changes in left ventricular uptake, dyssynchrony, and function.

PURPOSE: (99m)Tc-MIBI gated myocardial scintigraphy (GMS) evaluates myocyte integrity and perfusion, left ventricular (LV) dyssynchrony and function. Cardiac resynchronization therapy (CRT) may improve the clinical symptoms of heart failure (HF), but its benefits for LV function are less pronounced. We assessed whether changes in myocardial (99m)Tc-MIBI uptake after CRT are related to improvement in clinical symptoms, LV synchrony and performance, and whether GMS adds information for patient selection for CRT. METHODS: A group of 30 patients with severe HF were prospectively studied before and 3 months after CRT. Variables analysed were HF functional class, QRS duration, LV ejection fraction (LVEF) by echocardiography, myocardial (99m)Tc-MIBI uptake, LV end-diastolic volume (EDV) and end-systolic volume (ESV), phase analysis LV dyssynchrony indices, and regional motion by GMS. After CRT, patients were divided into two groups according to improvement in LVEF: group 1 (12 patients) with increase in LVEF of 5 or more points, and group 2 (18 patients) without a significant increase. RESULTS: After CRT, both groups showed a significant improvement in HF functional class, reduced QRS width and increased septal wall (99m)Tc-MIBI uptake. Only group 1 showed favourable changes in EDV, ESV, LV dyssynchrony indices, and regional motion. Before CRT, EDV, and ESV were lower in group 1 than in group 2. Anterior and inferior wall (99m)Tc-MIBI uptakes were higher in group 1 than in group 2 (p<0.05). EDV was the only independent predictor of an increase in LVEF (p=0.01). The optimal EDV cut-off point was 315 ml (sensitivity 89%, specificity 94%). CONCLUSION: The evaluation of EDV by GMS added information on patient selection for CRT. After CRT, LVEF increase occurred in hearts less dilated and with more normal (99m)Tc-MIBI uptake.

Strategy for identifying an efficient dosage of beta-blocker for elderly patients with myocardial ischemia and preserved left ventricular function.

OBJECTIVE: To assess the strategy of titration for prescribing an efficient dosage of propranolol to reduce myocardial ischemia in the elderly. METHODS: The study comprised 14 elderly men (73.6 +/- 5.3 years) with stable coronary heart disease documented on coronary cineangiography, ischemic response to exercise testing, and preserved left ventricular function. Titration was performed to identify the dosage of propranolol that would cause a 15% reduction in heart rate at the end of a 50 W load (corresponding to normal daily activities in the elderly) in weekly exercise tests. Synchronous scintigraphic study of the cardiac chambers was performed at rest and during exercise prior to and after propranolol use. RESULTS: The reductions in heart rate with the 50 W load and at rest were similar (21% vs 20%; P=0.5100). Propranolol improved the duration of exercise (12.2 +/- 2.0 min vs 13.1 +/- 1.8 min; P=0.0313) and abolished the changes in the ST segment induced by exercise in 8 (57%) patients. At rest, the ejection fraction was not modified by the beta-blocker. During maximum exercise, propranolol reduced the end-systolic volume index and increased ejection fraction. CONCLUSION: The strategy of using beta-blockers to reduce heart rate by 15% with a 50 W load is safe and beneficial in the elderly patient with myocardial ischemia and preserved ventricular function. The dose of beta-blocker used reduced myocardial ischemia and improved tolerance to exercise without hampering ventricular performance during maximum exercise.

Low-carbohydrate diet versus euglycemic hyperinsulinemic clamp for the assessment of myocardial viability with 18F-fluorodeoxyglucose-PET: a pilot study.

Positron emission tomography with (18)F-fluorodeoxyglucose (FDG-PET) is considered the gold standard for myocardial viability. A pilot study was undertaken to compare FDG-PET using euglycemic hyperinsulinemic clamp before (18)F-fluorodeoxyglucose ((18)F-FDG) administration (PET-CLAMP) with a new proposed technique consisting of a 24-h low-carbohydrate diet before (18)F-FDG injection (PET-DIET), for the assessment of hypoperfused but viable myocardium (hibernating myocardium). Thirty patients with previous myocardial infarction were subjected to rest (99m)Tc-sestamibi-SPECT and two (18)F-FDG studies (PET-CLAMP and PET-DIET). Myocardial tracer uptake was visually scored using a 5-point scale in a 17-segment model. Hibernating myocardium was defined as normal or mildly reduced metabolism ((18)F-FDG uptake) in areas with reduced perfusion ((99m)Tc-sestamibi uptake) since (18)F-FDG uptake was higher than the degree of hypoperfusion-perfusion/metabolism mismatch indicating a larger flow defect. PET-DIET identified 79 segments and PET-CLAMP 71 as hibernating myocardium. Both methods agreed in 61 segments (agreement = 94.5 %, κ = 0.78). PET-DIET identified 230 segments and PET-CLAMP 238 as nonviable. None of the patients had hypoglycemia after DIET, while 20 % had it during CLAMP. PET-DIET compared with PET-CLAMP had a good correlation for the assessment of hibernating myocardium. To our knowledge, these data provide the first evidence of the possibility of myocardial viability assessment with this technique.

Avaliação da reserva funcional miocárdica em portadores de aneurisma de ventrículo esquerdo por ventriculografia radioisotópica. Resposta ao exercício isotônico / Radionuclide Ventriculography Assessment of Myocardial Functional Reserve in Patients With Left Ventricular Aneurysm. Response to Isotonic Exercise

PURPOSE: To evaluate global and regional left ventricular (LV) ejection fractions (EF) by radionuclide ventriculography in patients with LV aneurysm at rest and during isotonic exercise. METHODS: Twenty patients were studied by radionuclide ventriculography at rest and during exercise. All patients had been submitted to cineangiography and showed LV aneurysm post myocardial infarction. RESULTS: Patients were divided according to LV EF in two groups: one with EF > or = 40 and the other with < 40 EF. Both groups showed normal response of global EF to exercise: mean rest EF was 40 +/- 14 and mean exercise EF was 45 +/- 14 (p < 0.01). When groups were considered separately, EF values showed the same behavior. Half of the patients showed normal response to exercise and the other half showed abnormal response. These changes were not associated with resting EF values, but were due to regional EF of lateral wall, that changed from 44 +/- 7 to 48 +/- 7 in the group of patients with normal LV EF response to stress and from 50 +/- 5 to 46 +/- 5 in those with abnormal response (p < 0.01). CONCLUSION: The evaluation of regional ventricular EF by radionuclide ventriculography during exercise better discriminates functional reserve in patients with LV aneurysm than resting global EF. These findings could help the decision making of the therapeutic approach in this specific group of patients.

Objetivo - Avaliar a fração de ejeção (FE) global e segmentar do ventrículo esquerdo (VE), em portadores de aneurisma ventricular pelo uso da ventriculografia radioisotópica no repouso e ao exercício isotônico. Métodos - Foram estudados 20 pacientes através da ventriculografia radioisotópica em repouso e na vigência de exercício isotônico. Os pacientes tinham dingnóstico de aneurisma de VE pós-infarto do miocárdio à cineangiografia contrastada. Resultados - Os pacientes foram divididos em 2 grupos segundo a FE global de VE no repouso: grupo com FE >40% e outro com FE <40%. Quando analisados os dois grupos em conjunto, a resposta da FE global ao esforço foi normal: média de FE no repouso 4014% e no esforço 4514% (p<0,01). Observou-se o mesmo comportamento das FE no esforço quando os 2 grupos foram analisados separadamente. Metade dos pacientes apresentou resposta normal da FE global de VE e na outra metade a resposta foi anormal. Este comportamento nao estava associado ao valor de repouso da FE global e deveu-se à resposta da FE regional da parede lateral ao exercício que passou de 447para 487% (p<0,01) no grupo com resposta normul e de 505 para 465% naqueles com resposta anormal (p<0,01). Conclusão - A avaliação da fração regional ventricular no esforço pela ventriculografia radioisotópica discrimina melhor a reserva funcional de portadores de aneurisma de VE do que a FE global de repouso e pode auxiliar na decisão terapêutica deste grupo de pacientes

Estratégia para individualizar uma dose eficiente de betabloqueador em pacientes idosos com isquemia miocárdica e função ventricular esquerda preservada / Strategy for identifying an efficient dosage of beta-blocker for elderly patients with myocardial ischemia and preserved left ventricular function

OBJETIVO: Avaliar estratégia de titulação para prescrever uma dose de propranolol que seria eficiente em reduzir isquemia do miocárdio em idosos. MÉTODOS: Foram estudados 14 homens idosos (73,6 ± 5,3 anos), portadores de doença coronariana estável, documentada pela cinecoronariografia, com resposta isquêmica ao teste ergométrico e função ventricular esquerda preservada. O propranolol foi titulado a fim de atingir redução de 15 por cento na freqüência cardíaca, ao final da carga de 50 W (correspondente às atividades diárias normais de idosos), em testes ergométricos semanais e feito estudo cintilográfico sincronizado das câmaras cardíacas, em repouso e durante exercício, antes e após seu uso. RESULTADOS: As reduções da freqüência cardíaca na carga de 50 W e em repouso foram semelhantes (21 por cento vs 20 por cento; p=0,5100). O propranolol melhorou a duração do exercício (12,2 ± 2,0 min vs 13,1 ± 1,8 min; p=0,0313) e aboliu as alterações do segmento ST induzidas pelo exercício em 8 (57 por cento) pacientes. Em repouso, a fração de ejeção não foi modificada pelo betabloqueador. Durante o exercício máximo, o propranolol reduziu o índice de volume sistólico final e aumentou a fração de ejeção. CONCLUSAO: A estratégia de empregar betabloqueadores para reduzir a freqüência cardíaca em 15 por cento na carga de 50 W é segura e benéfica nos idosos com isquemia miocárdica e função ventricular preservada. A dose utilizada reduziu a isquemia miocárdica e melhorou a tolerância ao exercício, sem prejudicar o desempenho ventricular durante exercício máximo.

Avaliaçäo do pré-processamento das projeçöes em ESPECT com phantom físico / Evaluation of projections pre-processing in SPECT with physical phantom

Neste trabalho, apresenta-se uma solução alternativa para a reconstrução de imagens tomográficas em Medicina Nuclear que usa o modelo de ruído de Poisson. O algoritmo proposto foi aplicado a um phantom físico e comparada com a metodologia usual de reconstrução em rotina clínica. A análise dos resultados mostrou que a aplicação do método melhora a qualidade das imagens reconstruídas.

We present an altemative solution for the reconstruction of SPECT images using a Poisson Noise Model. The proposed algorithm was applied on a real phantom and compared to the standard clinica! procedure. Results have shown that the proposed method improves the quality ofthe SPECT images.