Relationship of Electromechanical Dyssynchrony in Patients Submitted to CRT With LV Lead Implantation Guided by Gated Myocardial Perfusion Spect / Relação entre Dissincronismo Elétrico e Mecânico em Pacientes Submetidos a TRC com Implante do Eletrodo de VE Orientado pela Cintilografia GATED SPECT

Abstract Background: Heart failure (HF) affects more than 5 million individuals in the United States, with more than 1 million hospital admissions per year. Cardiac resynchronization therapy (CRT) can benefit patients with advanced HF and prolonged QRS. A significant percentage of patients, however, does not respond to CRT. Electrical dyssynchrony isolated might not be a good predictor of response, and the last left ventricular (LV) segment to contract can influence the response. Objectives: To assess electromechanical dyssynchrony in CRT with LV lead implantation guided by GATED SPECT. Methods: This study included 15 patients with functional class II-IV HF and clinically optimized, ejection fraction of 35%, sinus rhythm, left bundle-branch block, and QRS ≥ 120 ms. The patients underwent electrocardiography, answered the Minnesota Living with Heart Failure Questionnaire (MLHFQ), and underwent gated myocardial perfusion SPECT up to 4 weeks before CRT, being reassessed 6 months later. The primary analysis aimed at determining the proportion of patients with a reduction in QRS duration and favorable response to CRT, depending on concordance of the LV lead position, using chi-square test. The pre- and post-CRT variables were analyzed by use of Student t test, adopting the significance level of 5%. Results: We implanted 15 CRT devices, and 2 patients died during follow-up. The durations of the QRS (212 ms vs 136 ms) and the PR interval (179 ms vs 126 ms) were significantly reduced (p < 0.001). In 54% of the patients, the lead position was concordant with the maximal delay site. In the responder group, the lateral position was prevalent. The MLHFQ showed a significant improvement in quality of life (p < 0.0002). Conclusion: CRT determines improvement in the quality of life and in electrical synchronism. Electromechanical synchronism relates to response to CRT. Positioning the LV lead in the maximal delay site has limitations.

Resumo Fundamento: A insuficiência cardíaca (IC) afeta mais de 5 milhões de pessoas nos Estados Unidos, com mais de 1 milhão de internações/ano. A terapia de ressincronização (TRC) pode beneficiar pacientes com IC avançada e QRS alargado; entretanto, percentual significativo de pacientes não respondem à TRC. O dissincronismo elétrico isolado pode não representar um bom preditor de resposta, e o local da última ativação do ventrículo esquerdo (VE) pode influenciar na resposta. Objetivos: Avaliar o dissincronismo eletromecânico na TRC com o implante do eletrodo do VE orientado por GATED SPECT. Métodos: Incluídos 15 pacientes com IC classe funcional II-IV, otimizados clinicamente, com fração de ejeção de 35%, ritmo sinusal, bloqueio de ramo esquerdo, QRS ≥ 120 ms. Realizaram eletrocardiograma, Questionário Minnesota Vivendo com Insuficiência Cardíaca (MLHFQ) e cintilografia GATED SPECT até 4 semanas antes do implante. Reavaliados 6 meses após. Análise primária visou determinar a proporção de pacientes com redução da duração do QRS e resposta favorável à TRC dependendo da concordância ou não na posição do eletrodo, utilizando teste Qui-Quadrado. Análise das variáveis pré e pós TRC foi feita através do teste t de Student, assumindo significância de 5%. Resultados: Realizamos 15 implantes com 2 óbitos no seguimento. As reduções das durações do QRS (212 ms vs 136 ms) e do IPR (179 ms vs 126 ms) foram significativas (p < 0,001). Em 54%, o eletrodo foi concordante com o local de maior atraso. No grupo respondedor, a posição lateral foi prevalente. O MLHFQ mostrou melhora significativa da qualidade de vida (p < 0,0002). Conclusão: A TRC determina melhora da qualidade de vida e do sincronismo elétrico. O sincronismo eletromecânico relaciona-se com a resposta à TRC. O posicionamento do eletrodo de VE no sítio de maior retardo tem limitações.

Impaired Coronary Flow Reserve Is the Most Important Marker of Viable Myocardium in the Myocardial Segment-Based Analysis of Dual-Isotope Gated Myocardial Perfusion Single-Photon Emission Computed Tomography

OBJECTIVE: The aim of this study was to investigate the most robust predictor of myocardial viability among stress/rest reversibility (coronary flow reserve [CFR] impairment), 201Tl perfusion status at rest, 201Tl 24 hours redistribution and systolic wall thickening of 99mTc-methoxyisobutylisonitrile using a dual isotope gated myocardial perfusion single-photon emission computed tomography (SPECT) in patients with coronary artery disease (CAD) who were re-vascularized with a coronary artery bypass graft (CABG) surgery. MATERIALS AND METHODS: A total of 39 patients with CAD was enrolled (34 men and 5 women), aged between 36 and 72 years (mean 58 +/- 8 standard in years) who underwent both pre- and 3 months post-CABG myocardial SPECT. We analyzed 17 myocardial segments per patient. Perfusion status and wall motion were semi-quantitatively evaluated using a 4-point grading system. Viable myocardium was defined as dysfunctional myocardium which showed wall motion improvement after CABG. RESULTS: The left ventricular ejection fraction (LVEF) significantly increased from 37.8 +/- 9.0% to 45.5 +/- 12.3% (p < 0.001) in 22 patients who had a pre-CABG LVEF lower than 50%. Among 590 myocardial segments in the re-vascularized area, 115 showed abnormal wall motion before CABG and 73.9% (85 of 115) had wall motion improvement after CABG. In the univariate analysis (n = 115 segments), stress/rest reversibility (p < 0.001) and 201Tl rest perfusion status (p = 0.024) were significant predictors of wall motion improvement. However, in multiple logistic regression analysis, stress/rest reversibility alone was a significant predictor for post-CABG wall motion improvement (p < 0.001). CONCLUSION: Stress/rest reversibility (impaired CFR) during dual-isotope gated myocardial perfusion SPECT was the single most important predictor of wall motion improvement after CABG.

Assessment of diastolic heart function--experience with 16-gated myocardial perfusion SPECT.

BACKGROUND: Ischaemic heart disease (IHD) is a major health problem today. However the focus has shifted primarily to angiographically detecting epicardial vessel stenoses, and ways and means of surgically correcting the blocks. Patients are often not fully evaluated for cardiac function, and diastolic dysfunction of heart, which is often an earlier manifestation than systolic dysfunction, goes undetected. METHODS: Recent gamma cameras have better imaging quality due to attenuation correction with SPECT-CT. 121 patients underwent gated myocardial perfusion imaging (MPI) for suspected coronary artery disease (CAD). We studied the diastolic function of these patients by 16-gated SPECT MPI. RESULTS: 60% patients showed absence of inducible ischaemia on MPI, and hence further invasive procedures like angiography were prevented, 40% showed inducible ischaemia and had to be further evaluated and required intervention. Of all 121 patients, 10% had LV systolic and diastolic dysfunction whereas 66% had isolated diastolic dysfunction. 40% patients had no ischaemia, normal systolic function and only diastolic dysfunction. 40% of these cases had symptoms of chest heaviness/angina equivalent. CONCLUSION: Myocardial perfusion imaging is a useful modality for evaluating patients of suspected CAD and in addition to perfusion data, also provides functional assessment of systolic and diastolic function, which provides comprehensive information regarding patients' symptomatology and can guide further management.

Respiratory Motion Detection and Correction in ECG-Gated SPECT: a New Approach

OBJECTIVE: Gated myocardial perfusion single-photon emission computed tomography (GSPECT) has been established as an accurate and reproducible diagnostic and prognostic technique for the assessment of myocardial perfusion and function. Respiratory motion is among the major factors that may affect the quality of myocardial perfusion imaging (MPI) and consequently the accuracy of the examination. In this study, we have proposed a new approach for the tracking of respiratory motion and the correction of unwanted respiratory motion by the use of respiratory-cardiac gated-SPECT (RC-GSPECT). In addition, we have evaluated the use of RC-GSPECT for quantitative and visual assessment of myocardial perfusion and function. MATERIALS AND METHODS: Twenty-six patients with known or suspected coronary artery disease (CAD)-underwent two-day stress and rest (99m)Tc-Tetrofosmin myocardial scintigraphy using both conventional GSPECT and RC-GSPECT methods. The respiratory signals were induced by use of a CT real-time position management (RPM) respiratory gating interface. A PIO-D144 card, which is transistor-transistor logic (TTL) compatible, was used as the input interface for simultaneous detection of both ECG and respiration signals. RESULTS: A total of 26 patients with known or suspected CAD were examined in this study. Stress and rest myocardial respiratory motion in the vertical direction was 8.8-16.6 mm (mean, 12.4 +/- 2.9 mm) and 7.8-11.8 mm (mean, 9.5 +/- 1.6 mm), respectively. The percentages of tracer intensity in the inferior, inferoseptal and septal walls as well as the inferior to lateral (I/L) uptake ratio was significantly higher with the use of RC-GSPECT as compared to the use of GSPECT (p < 0.01). In a left ventricular ejection fraction (LVEF) correlation analysis between the use of rest GSPECT and RC-GSPECT with echocardiography, better correlation was noted between RC-GSPECT and echocardiography as compared with the use of GSPECT (y = 0.9654x + 1.6514; r = 0.93, p < 0.001 versus y = 0.8046x + 5.1704; r = 0.89, p < 0.001). Nineteen (19/26) patients (73.1%) showed abnormal myocardial perfusion scans with reversible regional myocardial defects; of the 19 patients, 14 (14/26) patients underwent coronary angiography. CONCLUSION: Respiratory induced motion can be successfully corrected simultaneously with the use of ECG-gated SPECT in MPI studies using this proposed technique. Moreover, the use of ECG-gated SPECT improved image quality, especially in the inferior and septal regions that are mostly affected by diaphragmatic attenuation. However, the effect of respiratory correction depends mainly on the patient respiratory pattern and may be clinically relevant in certain cases.