Utility of Left Bundle Branch Block as a Diagnostic Criterion for Acute Myocardial Infarction

230 , UTILITY OF LEFT BUNDLE BRANCH BLOCK AS A DIAGNOSTIC CRITERION FOR ACUTE MYOCARDIAL INFARCTION. Jain S, Ting H, Bell M, et al. Am J Cardiol 2011;107:1111–6. This retrospective analysis sought to determine the predictive value of a new or presumably new left bundle branch block (LBBB) and the Sgarbossa criteria in diagnosing acute myocardial infarction (AMI). Data from 892 patients who presented to a Mayo Clinic-affiliated facility from July 2004 to August 2009 were used to conduct this analysis. Of the 892 patients, 36 (4%) had symptoms consistent with AMI and electrocardiogram findings with a new or presumably new LBBB. These patients tended to fall into a higher risk category and were more likely to be old, less likely to be men, had higher Thrombolysis In Myocardial Infarction score, and were more likely to have congestive heart failure. Only 39% of these patients were subsequently diagnosed with acute coronary syndrome (ACS), whereas 36% had non-ACS cardiac diagnoses and the final 25% had non-cardiac final diagnoses. Of the 14 patients who were diagnosed with ACS, 13 presented with chest pain. In contrast, the patients with a new LBBB who were determined to have a non-ACS cardiac etiology were unlikely to present with chest pain (only 2 of the 13). Finally, the Sgarbossa criteria had a very low sensitivity (14%) for diagnosing AMI. The authors concluded that a small but substantial proportion of persons who present with symptoms concerning for AMI will have a new LBBB. New LBBB leads to false activation of the cardiac catheterization laboratory nearly 2/3 of the time. Furthermore, the Sgarbossa criteria are a poor screening test for identifying ACS. [Garrett Mitchell, MD Denver Health Medical Center, Denver, CO] Comments: This study is very detailed but was limited by the retrospective design and the small number of patients in the study group. It also provides little additional information regarding diagnosing AMI or ACS in the setting of a new LBBB. It did, however, add further evidence to the notion that the Sgarbossa criteria are of limited value in this setting. , MARKERS FOR BACTERIAL INFECTION IN CHILDREN WITH FEVER WITHOUT A SOURCE. Manzano S, Bailey B, Gervaix A, et al. Arch Dis Child 2011;96:440–6. This prospective cohort study from a pediatric emergency department in Switzerland sought to compare the diagnostic properties of several common laboratory tests to each other and to clinical evaluation in detecting a serious bacterial infection (SBI) in febrile children in the post-pneumococcal vaccination era. There were 328 children aged 1–36 months who had a temperature > 38  C enrolled. Sixteen percent of the children had an SBI: 89% had urinary tract infections, 7% had pneumonia, 2% had meningitis, and 2% had occult bacteremia. Total white blood cell count (WBC), absolute neutrophil count (ANC), C-reactive protein (CRP), and procalcitonin (PCT) were measured, and clinical assessment of SBI probability was evaluated using a visual analogue scale. Using the receiver operating characteristics (ROC) and area under the ROC curve,

Abstracts the laboratory tests and the clinical assessment were compared. The authors also calculated multilevel likelihood ratios and variable-best cutoffs from the optimal cutoffs obtained from the ROC analysis. CRP (variable-best cutoff > 0.20 ng/mL), PCT (> 17.7 mg/L), WBC (> 14,100  106/L), and ANC (> 5200  106/L) all had similar diagnostic abilities to detect SBI, with sensitivities of 85.2%, 94.4%, 81.5%, and 87%, respectively. All were superior to clinical evaluation (sensitivity of 68.5%). In the setting of a normal urinalysis, these laboratory tests had high negative predictive values (PCT 99.4%, CRP 99.4%, WBC 98.9%, ANC 98.7%). [Brad Stevinson, MD Denver Health Medical Center, Denver, CO] Comment: The authors’ findings that the laboratory studies had similar abilities to detect SBI in febrile infants when compared to each other, and superior abilities when compared to clinical evaluation, are consistent with prior work. However, the 16% prevalence of SBI in this study is lower than that described in some previous work. As such, their optimal cutoff values and negative predictive values may not be generalizable. This is yet another reminder that surrogate markers need to be interpreted within the context of the individual patient and within the context of the individual practitioner’s patient population. , CUMULATIVE EFFECTIVE DOSE ASSOCIATED WITH RADIOGRAPHY AND CT OF ADOLESCENTS WITH SPINAL INJURIES. Lemburg S, Peters S, Roggenland D, et al. AJR Am J Roentgenol 2010;195:1411–7. This retrospective cohort study attempted to demonstrate that patients with multiple traumatic injuries receive significantly higher doses of radiation during imaging studies than trauma patients with isolated spinal injuries. The study was conducted at a level I trauma center from July 2003 through June 2009. All patients aged 10–20 years with spinal fractures who were admitted during the study period were included. Patients were divided into two groups based on whether they had isolated spinal injuries vs. multiple traumatic injuries. Imaging procedures during initial evaluation and hospitalization, as well as imaging procedures after discharge were retrospectively analyzed. The cumulative effective doses for all imaging studies were calculated. Seventy-two patients were included, 32 with multiple injuries and 40 with isolated spine injuries. Patients with multiple injuries had a significantly higher total cumulative effective dose (29.7 vs. 10.86 mSv) than patients with isolated spinal injuries (p < 0.001). Patients with multiple injuries had a significantly longer clinical course than did patients without multiple injuries (10.1 months vs. 3.1 months, p = 0.037). Multiple-injury patients underwent full or modified computed tomography scan of the head, neck, and trunk in significantly higher numbers (p < 0.001). Computed tomography accounted for 86% of the median cumulative effective doses. [Erik Adler, MD Denver Health Medical Center, Denver, CO] Comment: The risk of radiation associated with diagnostic imaging is well known. The Biological Effects of Ionizing Radiation VII Report estimates that solid cancer or leukemia