Abstract
IntroductionWe investigated if uptake pattern on myocardial perfusion SPECT (MPS) in patients with left bundle branch block (LBBB) is related to myocardial fibrosis, myocardial wall motion, and electrocardiography (ECG) characteristics. MethodsTwenty-three patients (9 women) with LBBB, examined with MPS and cardiac magnetic resonance (CMR), were included. Tracer uptake on MPS was classified by visual interpretation as typical LBBB pattern (Defect+, n = 13) or not (Defect−, n = 10) and quantitatively. CMR images were evaluated for wall thickness and for myocardial wall motion both by visual assessment and by regional myocardial radial strain from feature tracking, and for presence and location of myocardial fibrosis. ECGs were analyzed regarding QRS duration and the presence of strict criteria for LBBB. ResultsWall thickness was slightly lower in the septum compared to the lateral wall in Defect+ patients (5.6 ± 1.1 vs 6.0 ± 1.3 mm, P = 0.03) but not in Defect− patients (5.6 ± 1.0 vs 5.6 ± 0.9 mm, P = 0.84). Defect+ patients showed a larger proportion of dyskinetic segments in the septum and hyperkinetic segments in the lateral wall compared to Defect− patients (P = 0.006 and P = 0.004, respectively). Decreased myocardial radial strain was associated with decreased tracer uptake by MPS (R = 0.37, P < 0.001). Areas of fibrosis did not match areas with uptake defect on MPS. No differences in ECG variables were seen. ConclusionThe heterogeneous regional tracer uptake in some patients with LBBB is related to underlying regional myocardial dyskinesia, wall thickening, and wall thickness rather than stress-induced ischemia, myocardial fibrosis, or specific ECG characteristics.
Highlights
We investigated if uptake pattern on myocardial perfusion SPECT (MPS) in patients with left bundle branch block (LBBB) is related to myocardial fibrosis, myocardial wall motion, and electrocardiography (ECG) characteristics
Phase histogram bandwidth, and phase standard deviation were slightly higher for the Defect? group compared to the Defect- group, but the differences were not statistically significant (P = 0.17, P = 0.26 and P = 0.20, respectively)
The findings in the present study suggest that in patients with Left bundle branch block (LBBB), the presence of typical LBBB uptake pattern on MPS is related to regional myocardial dyskinesia, wall thickening, and wall thickness rather than stress-induced ischemia, myocardial fibrosis, or characteristics on ECG
Summary
We investigated if uptake pattern on myocardial perfusion SPECT (MPS) in patients with left bundle branch block (LBBB) is related to myocardial fibrosis, myocardial wall motion, and electrocardiography (ECG) characteristics. Left bundle branch block (LBBB) is a cardiac conduction abnormality usually seen in patients with underlying heart disease. Several possible explanations for typical LBBB-related defects on MPS have been proposed, such as decreased septal wall thickness, myocardial wall motion abnormalities, and truly reduced blood flow due to diminished demand and/or diastolic filling time.[8,9,10] it is not clear if these parameters differ in patients with LBBB and presence or absence of typical uptake pattern on MPS. Patients with LBBB might have myocardial fibrosis or infarction affecting the regional uptake of the tracer in the left ventricle. Interpreting MPS in patients with LBBB can be a diagnostic challenge
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