To what extent are perfusion defects seen by myocardial perfusion SPECT in patients with left bundle branch block related to myocardial infarction, ECG characteristics, and myocardial wall motion?

Figure 1. The top row A shows an example of a patient considered to have a typical left bundle branch block (LBBB) uptake pattern on myocardial perfusion SPECT (MPS) images (Defect+ group). One MPS short-axis slice at rest is shown. On quantitative assessment of tracer uptake on MPS, summed stress score was 19 and summed rest score was 16. The electrocardiogram (ECG) meet strict criteria for LBBB16 with a QRS duration of 144 ms. Cine short-axis cardiac magnetic resonance (CMR) images are shown in end-diastole (ED) and end-systole (ES). No signs of myocardial fibrosis can be found in late gadolinium enhancement (LGE)-CMR images. The bottom row B shows an example of a patient considered not to have a typical LBBB uptake pattern on MPS (Defect− group). The ECG meet strict criteria for LBBB with a QRS duration of 148 ms. This patient is one out of six where signs of myocardial fibrosis were found in LGE-CMR images, in this case in the endocardial parts of the basal lateral wall (arrow) constituting 3.6% of the left ventricle. One MPS short-axis slice at rest is shown. On quantitative assessment of tracer uptake on MPS, summed stress score was 3 and summed rest score was 3

Figure 2. MPS rest perfusion (mean±SD), expressed as a percentage of raw counts to the maximum raw count in the image, for the septal and lateral wall in the Defect+ and Defect− group, respectively. Septal and lateral wall are the two basal and two mid-ventricular segments, segments 2, 3, 8, and 9 for the septal wall, and segments 5, 6, 11, and 12 for the lateral wall in the AHA 17-segment model. ns, not significant, *P < 0.05, **< 0.01 and ***P < 0.001

Figure 3. Visual assessment of regional left ventricular wall motion on CMR according to the AHA 17-segment model, where wall motion in each segment was graded to one of the following: hyperkinesia, normokinesia, hypokinesia, akinesia, or dyskinesia. Patients with a typical left bundle branch block (LBBB) uptake pattern on myocardial perfusion SPECT (MPS) (white bars), Defect+ group, and patients with no typical LBBB uptake pattern on MPS (black bars), Defect− group

Figure 4. Radial strain (mean±SD) at end-systole in cardiac magnetic resonance short-axis images, for the septal and lateral wall in the Defect+ and Defect− group, respectively. Septal and lateral wall are the two basal and two mid-ventricular segments, segments 2, 3, 8, and 9 for the septal wall, and segments 5, 6, 11, and 12 for the lateral wall in the AHA 17-segment model. ns, not significant, *P < 0.05, **P < 0.01, and ***P < 0.001

Figure 5. Radial strain on cardiac magnetic resonance (CMR) images in each segment according to the AHA 17-segment model in all patients, correlated to visual assessment of uptake score on myocardial perfusion SPECT (MPS) images at rest in each segment in all patients. Boxes extend from 25th to 75th percentiles and whiskers extend from 10th to 90th percentiles. In total, 352 segments could be analyzed. One patient did not complete rest MPS examination since the stress MPS examination was considered normal. For this patient, the MPS tracer uptake scores at stress are used. n = number of segments in each MPS tracer uptake score group

Figure 6. Relationship between MPS tracer uptake, expressed as a percentage of raw counts to the maximum raw count in the image, and left ventricular radial strain by CMR in all patients on a myocardial segmental level. In total, 352 segments were analyzed. One patient did not complete rest MPS examination since the stress MPS examination was considered normal. For this patient, the MPS tracer uptake scores at stress are used