Myocardial blood flow assessment with 82rubidium-PET imaging in patients with left bundle branch block

Abstract

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.

Myocardial perfusion artifacts in left bundle branch block: A diagnostic challenge

“…13,16,17 The role of absolute myocardial blood flow (MBF) quantification using positron emission tomography (PET) MPI has been suggested to avoid misinterpretation of septal perfusion defects in patients with LBBB in two small studies. 12,18 In general, PET MPI has clear advantages over SPECT including higher photon energy, improved resolution, attenuation correction, lesser radiation exposure, shorter test time, and the ability to quantify absolute MBF. 19 Whether these technical advantages translate into improved diagnostic performance in patients with LBBB has not been systematically evaluated.…”

“…Two small studies suggest that determination of absolute MBF (using Rb-82 and O15-[H 2 O]) may improve the diagnostic performance of PET MPI in those with LBBB. 12,18 In this issue of the journal, Meredith et al, 20 using regadenoson, report that relative Rb-82 PET MPI without the use of absolute MBF measures can be reliably used to identify obstructive CAD in patients with LBBB. Given the small size and conflicting results with a previous O-15 study 12 we raise the following important questions that merit further research in a larger cohort:…”

Left Ventricular Dyssynchrony in a Patient with Normal Perfusion and Stress-Induced Left Bundle Branch Block

“…7 Myocardial perfusion PET-CT is a technique that can contribute to increase the accuracy of CAD evaluation in patients with LBBB. Recently, Falcão et al, 8 demonstrated that 82Rb-PET relative myocardial perfusion could discriminate between LBBB patients with and without CAD, even when considering the LAD territory alone.…”

Atualização da Diretriz Brasileira de Cardiologia Nuclear – 2020

“…Nesses pacientes, frequentemente, se observa hipocaptação do radiofármaco relacionada de modo mais frequente à região septal, que pode se exacerbar com o teste de esforço, pois o aumento da FC aumenta o movimento paradoxal do septo e, consequentemente, reduz a perfusão nessa parede. 67,68 Fármacos que induzem vasodilatação primária: Dipiridamol, adenosina e regadenoson (não disponível em nosso meio para a prática clínica rotineira) provocam aumento importante do fluxo coronário nas artérias normais e pequeno ou inexistente nas com estenose funcionalmente significante, resultando, então, na heterogeneidade relativa de fluxo entre as paredes do VE. Durante a vasodilatação máxima, quando injetado o radioisótopo, também será observada a diferença na captação relativa do radiofármaco pelas paredes do VE, possibilitando o diagnóstico de doença coronária:…”

“…Dada esta situação, a quantificação do fluxo coronário absoluto e da RFC emergiu como alternativa importante para a avaliação diagnóstica e prognóstica desses pacientes. Falcão et al, 306 demonstraram que a avaliação de reserva de fluxo pelo PET auxilia na detecção de DAC em pacientes portadores de bloqueio de ramo esquerdo. Pacientes com perfusão aparente normal e RFC anormal apresentaram maior taxa anual de morte cardíaca, infarto do miocárdio não fatal, revascularização tardia e hospitalização por causas cardíacas do que os pacientes com perfusão normal e RFC normal (6,3% versus 1,4%; p < 0,05).…”