Background: We sought to determine the reliability of electrocardiography (ECG) and chest radiography (CXR) in predicting left ventricular (LV) dysfunction in patients with suspected neuromuscular disorders (NMDs) undergoing preanesthetic evaluation for muscle biopsy. Methods: In this retrospective study, 255 patients with a preliminary diagnosis of NMDs based on history, physical examination, and laboratory testing underwent preanesthetic screening before muscle biopsy. The screening included various combinations of ECG, CXR, and transthoracic echocardiography (Echo) to assess perioperative risk associated with potentially undiagnosed LV dysfunction. Multivariate logistic regression analysis was applied to ascertain whether CXR and ECG were independently predictive of LV dysfunction. In addition, receiver-operating characteristic curve analysis was used to assess the diagnostic accuracy of each test and the combination of CXR and ECG in differentiating LV dysfunction from normal function based on Echo "gold standard" data. Results: The study consisted of 255 patients who had a transthoracic Echo, and among these patients, 235 had CXR and 237 had ECG. Forty-four patients were diagnosed by transthoracic Echo to have LV dysfunction (17.3%). Of the 255 patients in the study population, 24 were found to have mild LV dysfunction (9.4%) and 20 had moderate to severe LV dysfunction (7.8%) on Echo. With Echo providing the definitive standard for the diagnosis of LV dysfunction, we found that a CXR alone was predictive in 37% of cases of LV dysfunction, an ECG alone was predictive in 14% of cases, and the combination of both was predictive in 81% of cases. The combination of ECG and CXR test offered the highest diagnostic accuracy (area under the curve of 0.95, P < 0.0001) for differentiating moderate to severe LV dysfunction from normal LV function. Conclusions: In patients with suspected neuromuscular disease, CXR and ECG provided low independent diagnostic prediction for the presence or absence of LV dysfunction. The combination of both tests can identify cardiomyopathy with relatively high accuracy in children with suspected NMDs independent of age and gender, particularly in patients with moderate to severe LV dysfunction. Although our findings suggest that combination ECG and CXR screening is a reliable means of detecting LV dysfunction, this approach fails to differentiate the severity or type of cardiomyopathy that may exist. Therefore, the decision to obtain a perioperative Echo before muscle biopsy should involve careful consideration of the disease suspected, ECG and CXR results, laboratory studies, patient age, physical examination, and family history.