Clinical utility of a single 24-hour electrocardiogram in the investigation of patients with suspected cardiac dysrhythm

Despite the widespread use of ambulatory electrocardiography in cardiology practise, its clinical efficacy has not been extensively investigated. The purpose of this study was to evaluate the screening test performance of a single, continuous 24-hour electrocardiogram in 150 patients referred to a tertiary care center with clinical suspicion of cardiac dysrhythm. We found the incidence of symptoms during the test period to be significantly higher (29/50) among patients referred because of prior palpitations (group 1) relative to patients referred because of complaints of dizziness/presyncope (group 2; 10/50, p < 0.001) or patients referred because of non-specified clinical suspicion of dysrhythm, particularly ventricular dysrhythm (group 3; 17/50, p < 0.005). In contrast, abnormal cardiac rhythm was detected more frequently in group 3 (38/50) than in group 1 (24/50, p < 0.001) or group 2 (30/50, NS). The incidence of symptoms or detected dysrhythm, or both, which we defined as the maximal clinical utility of a single 24-hour test, was not different (NS) among the three referral groups, ranging from 68% in group 2 to 84% in group 3. Only in group 3, however, did patients have a high temporal concordance of symptoms and dysrhythm (12/17); in group 1 the symptom-dysrhythm concordance was 10/29 (p < 0.025) and only 2/10 (p < 0.025) in group 2. Overall, the data support the use of ambulatory electrocardiographic monitoring as a non-invasive diagnostic test for patients suspected to have abnormal cardiac rhythm. A single 24-hour recording appears most useful in the investigation of patients with palpitations because of a high incidence of palpitations during the test interval. Whatever the initial clinical stimulus for referral, a high proportion of tertiary care patients have symptoms in temporal concordance with sinus rhythm.