title: Research: Association of Low-Amplitude QRSs with False-Positive Asystole Alarms.
abstract: BACKGROUND
  Although electrocardiographic monitoring is valuable for continuous surveillance of intensive care unit (ICU) patients, false alarms are common and have been cited as a cause of alarm fatigue. ANSI/AAMI EC12:2002 states that electrocardiograms (ECGs) should not detect a QRS if the waveform is less than 0.15 mV (1.5 mm) for adult patients, in order to avoid mislabeling P waves or baseline noise as QRSs during complete heart block or asystole. However, ECG software algorithms often use more conservative QRS thresholds, which may result in false-positive asystole alarms in patients with low-amplitude QRS complexes.
  
  
  OBJECTIVE
  To 1) assess the frequency of low QRS amplitude in a group of ICU patients with one or more false-positive asystole alarms and 2) determine whether low-amplitude QRSs are associated with false-positive asystole alarms during continuous ECG monitoring.
  
  
  METHODS
  Hospital-acquired standard 12-lead ECGs were examined in a group of 82 ICU patients who had one or more false-positive asystole alarms. Low QRS amplitude was defined as a unidirectional (only positive or negative) QRS of less than 5 mm in two of four leads (I, II, III, and V1).
  
  
  RESULTS
  Low-amplitude QRSs were present in 45 of 82 (55%) patients. The presence of low-amplitude QRSs did not differ according to age, sex, or race. Patients treated in the cardiac ICU had the highest proportion of low-amplitude QRSs. An equivalent proportion of patients had false-positive asystole alarms by group (no low-amplitude QRSs 95% vs. low-amplitude QRSs 87%; P = 0.229). Eight patients (10%) had both true- and false-positive asystole alarms (two [5%] with no low-amplitude QRSs and six [13%] with low-amplitude QRSs; P = 0.229).
  
  
  CONCLUSIONS
  Low-amplitude QRS, as assessed from hospital 12-lead ECGs, occurs frequently and is more common in cardiac ICU patients. However, this ECG feature did not identify patients with false-positive asystole alarms during continuous ECG monitoring.
authors.forename: Michele M
authors.initials: MM
authors.lastname: Pelter
authors.forename: Richard
authors.initials: R
authors.lastname: Fidler
authors.forename: Xiao
authors.initials: X
authors.lastname: Hu
mesh_terms: D056902:Clinical Alarms; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D004562:Electrocardiography / Q000379:methods*; D005189:False Positive Reactions; D005260:Female; D006323:Heart Arrest / Q000175:diagnosis*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity