Prediction of Cardiac Events in Patients Having Left Bundle-Branch Block with/without Chest Pain Using Dipyridamole Technetium-99m-Sestamibi Myocardial Perfusion Imaging
Objective: To determine the prognostic value of myocardial perfusion scintigraphy with dipyridamole stress in patients with preexisting left bundle-branch block (LBBB) with or without chest pain. Subjects and Methods: Seventy-six patients, mean age 53 ± 10 years, with preexisting LBBB underwent technetium-99m-sestamibi perfusion imaging with dipyridamole infusion protocol (0.56 mg/kg). Stress and rest single photon emission computed tomography (SPECT) images were interpreted by consensus of 2 experienced nuclear medicine physicians and classified as low-risk scans (normal myocardial perfusion scan, small reversible/small fixed defect) and high-risk scans (large, severe, fixed or reversible defect and dilated left ventricle cavity). The patients were followed up for 24 ± 8 months and occurrences of hard cardiac events (infarction or cardiac death) were noted. Results: Of the 76 patients, 52 (68%) had low-risk scans and the remaining 24 (32%) had high-risk scans. In the low-risk group, 1 (1.9%) cardiac death and 2 (3.8%) cases of nonfatal myocardial infarction occurred, while in the high-risk group, 5 (20.8%) suffered cardiac death, and 3 (12.5%) nonfatal myocardial infarction. Overall survival rate was 98.1% in the low-risk group compared with 79.2% in the high-risk group with a significant difference of p = 0.034. Negative predictive value of normal myocardial perfusion scintigraphy for the occurrence of death was 100%. No significant difference in survival rate among patients with or without chest pain (p = 0.31) was observed. Conclusions: Myocardial perfusion imaging with dipyridamole provided important prognostic information in patients with LBBB; it was useful in stratifying the patients according to cardiovascular morbidity and mortality, and would thus allow the clinician to provide early treatment especially in the high-risk category.