Classes de Recomendação Classe I: Condições para as quais há evidências conclusivas e, na sua falta, consenso geral de que o procedimento é seguro e útil/eficaz. Classe II: Condições para as quais há evidências conflitantes e/ou divergência de opinião sobre a segurança e utilidade/eficácia do procedimento. Classe IIa: Peso ou evidência/opinião a favor do procedimento. A maioria aprova. Classe IIb: Segurança e utilidade/eficácia menos estabelecidas, havendo opiniões divergentes. Classe III: Condições para as quais há evidências e/ou consenso de que o procedimento não é útil/eficaz e, em alguns casos, pode ser prejudicial. Níveis de Evidência Nível A: Dados obtidos a partir de múltiplos estudos randomizados de bom porte, concordantes e/ou de metanálise robusta de estudos randomizados. Nível B: Dados obtidos a partir de metanálise menos robusta, a partir de um único estudo randomizado e/ou de estudos observacionais. Nível C: Dados obtidos de opiniões consensuais de especialistas. I falta útileficaz útil eficaz II eou utilidadeeficácia utilidade eficácia IIa evidênciaopinião evidência aprova IIb estabelecidas divergentes III casos prejudicial porte B observacionais C especialistas

Classes of Recommendation Class I: Conditions for which there is conclusive evidence and, failing that, general agreement that a given procedure is safe and useful/effective. Class II: Conditions for which there is conflicting evidence and/or a divergence of opinion about the safety and usefulness/efficacy of a procedure. Class IIa: Weight or evidence/opinion in favor of the procedure. Most approve. Class IIb: Safety and usefulness/efficacy less well established, with divergence of opinions. Class III: Conditions for which there is evidence and/or general agreement that a procedure is not useful/effective and, in some cases, may be harmful. Levels of Evidence Level A: Data derived from multiple large, concordant randomized trials and/or robust meta-analyses of randomized trials. Level B: Data derived from less robust meta-analyses, from a single randomized trial and/or from observational studies. Level C: Data derived from consensus opinion of experts. I usefuleffective useful effective II andor usefulnessefficacy usefulness efficacy IIa evidenceopinion approve IIb established opinions III cases harmful A large metaanalyses meta analyses B metaanalyses, analyses, studies C experts

OBJECTIVES: Perfusion abnormalities are frequently seen in Single Photon Emission Computed Tomography (SPECT) when a left bundle branch block is present. A few studies have shown decreased coronary flow reserve in the left anterior descending territory, regardless of the presence of coronary artery disease. OBJECTIVE: We sought to investigate rubidium-82 (82Rb) positron emission tomography imaging in the assessment of myocardial blood flow and coronary flow reserve in patients with left bundle branch block. METHODS: Thirty-eight patients with left bundle branch block (GI), median age 63.5 years, 22 (58%) female, 12 with coronary artery disease (≥70%; GI-A) and 26 with no evidence of significant coronary artery disease (GI-B), underwent rest-dipyridamole stress 82Rb-positron emission tomography with absolute quantitative flow measurements using Cedars-Sinai software (mL/min/g). The relative myocardial perfusion and left ventricular ejection fraction were assessed in 17 segments. These parameters were compared with those obtained from 30 patients with normal 82Rb-positron emission tomography studies and without left bundle branch block (GII). RESULTS: Stress myocardial blood flow and coronary flow reserve were significantly lower in GI than in GII (p<0.05). The comparison of coronary flow reserve between GI-A and GI-B showed that it was different from the global coronary flow reserve (p<0.05) and the stress flow was significantly lower in the anterior than in the septal wall for both groups. Perfusion abnormalities were more prevalent in GI-A (p=0.06) and the left ventricular ejection fraction was not different between GI-A and GI-B, whereas it was lower in GI than in GII (p<0.001). CONCLUSION: The data confirm that patients with left bundle branch block had decreased myocardial blood flow and coronary flow reserve and coronary flow reserve assessed by 82Rb-positron emission tomography imaging may be useful in identifying coronary artery disease in patients with left bundle branch block.