Perfusion and functional abnormalities outside the septal region in patients with left bundle branch block assessed with gated SPECT

Background. The presence of a left bundle branch block (LBBB) pattern on th e electrocardiogram may frequently lead to perfusion defects in the septum not necessarily due to ischemic heart disease, but probably due to abnormal septal wall motion. The introduction of gated single photon emission compu ted tomography (SPECT) allows the evaluation of myocardial perfusion and fu nction in one study. Accordingly, we analysed perfusion and function and th e relation between perfusion and regional function in the septal region in patients with a LBBB without evidence of a previously sustained myocardial infarction. Methods. We selected 37 patients with a LBBB without a history of a previou s myocardial infarction, which was confirmed by echocardiography and/or cor onary angiography. Ah patients underwent technetium-99m tetrofosmin gated S PECT myocardial imaging. Twelve control patients with a low likelihood of c oronary artery disease and a normal technetium-99m tetrofosmin gated SPECT myocardial perfusion scintigram were selected as a reference population. Th e left ventricle (LV) was divided into 18 segments, which were scored for p erfusion and function (wall motion and wall thickening) on a 4-point scale. Results. The average LV end-diastolic volume was higher and the average LV ejection fraction was lower in patients with LBBB as compared to controls ( 142 +/- 90 vs. 81 +/- 18 ml, and 48 +/- 13 vs 62 +/-7%, p=0.03 and p=0.02, respectively). Not only in the septum, but also in the other segments, redu ced myocardial perfusion and abnormal wall motion/wall thickening was obser ved in the patients with LBBB (p <0.0001 vs controls). Patients with LBBB s howed no correlation between perfusion and function in the septum, and betw een perfusion in septum and global LV function (r=0.21, p=0.2; r=0.10, p=0. 6, respectively). Conversely, a good correlation was found between perfusio n and function, either regional or global, in the remote segments (both r=0 .79, p <0.0001). Conclusions. We conclude that patients with LBBB without a previous myocard ial infarction show cardiomyopathic changes with perfusion and wall motion abnormalities, involving the entire left ventricle. The severity of diminis hed septal perfusion is not directly associated with the severity of septal wall motion abnormalities or global LV function. However, in the myocardia l segments remote from the septum, reduced perfusion is closely associated with functional abnormalities.