title: The J-wave: a new electrocardiographic sign of an occult cardiac injury.
abstract: BACKGROUND
  The aim of this study was to determine the sensitivity and specificity of a J wave on the electrocardiogram (ECG) to detect an occult cardiac injury in patients following penetrating chest trauma.
  
  
  METHODS
  A prospective study conducted on patients admitted to the Groote Schuur Hospital Trauma Centre following penetrating chest trauma during the period of 1st October 2001 and 28th February 2009, who did not have an indication for emergency surgery and that underwent an ECG and later a subxiphoid pericardial window (SPW) for a potential cardiac injury. All the patients were easily resuscitatable with less than 2l of crystalloid. A standard 12-lead ECG was performed shortly after admission. A J wave was defined as the small positive reflection on the R-ST junction.
  
  
  RESULTS
  There were 174 patients where an ECG was performed and the patient underwent SPW for a possible cardiac injury. The mean age of the patients was 28 years (range 11-65). The mechanism of injury was stab wounds in 167 patients and 7 low velocity gunshot wounds. A J-wave was present on the ECG in 65 (37%) of the 174 patients with a possible cardiac injury. The sensitivity of a J wave to detect a hemopericardium was 44%, specificity was 85%, and positive predictive value of 91% (p<0.001).
  
  
  CONCLUSIONS
  The presence of a 'J' wave on ECG signifies a significant risk of an occult cardiac injury after penetrating thoracic trauma.
authors.affiliation: Trauma Centre, Department of Surgery, Groote Schuur Hospital, University of Cape Town, Cape Town, South Africa. Electronic address: andrew.nicol@uct.ac.za.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Nicol
authors.forename: Pradeep H
authors.initials: PH
authors.lastname: Navsaria
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D003937:Diagnosis, Differential; D004562:Electrocardiography; D005188:False Negative Reactions; D005260:Female; D006335:Heart Injuries / Q000209:etiology / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010490:Pericardial Effusion / Q000209:etiology / Q000503:physiopathology*; D010491:Pericardial Window Techniques; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D013019:South Africa; D013898:Thoracic Injuries; D014193:Trauma Centers; D014950:Wounds, Penetrating / Q000150:complications*
keywords: Electrocardiogram; Hemopericardium; J wave; Occult cardiac injury; Penetrating cardiac trauma; ST segment elevation