Enhanced diagnosis of narrow complex tachycardias with increased electrocardiograph speed

The objective of this study was to determine if the addition of rapid speed (50 mm/s) electrocardiograms (EKGs) improves the clinician's diagnostic accuracy of narrow complex tachycardias when compared to standard speed (25 mm/s) EKGs. We conducted a prospective, comparative trial. Forty-five difficult narrow complex tachycardias (heart rate range: 150-250 beats per minute) were printed at both 25 mm/s and 50 mm/s. Eight board certified emergency physicians initially interpreted the standard speed EKG (standard group) and chose a therapy for the hypothetical patient. These eight participants later interpreted the same 45 EKGs by using both the standard and rapid speed EKGs (rapid group) and again chose a therapy. The gold standard for each EKG was based on the patient's clinical diagnosis and was independently confirmed in all cases by a board-certified cardiologist. The rhythm distribution was as follows: atrial flutter (17), atrial fibrillation (11), paroxysmal supraventricular tachycardia (15), and sinus tachycardia (2). Participants were masked to all clinical information and EKG ratios. Diagnostic accuracy was compared by using McNemar's chi(2) test. Correct diagnosis improved from 226/360 (63%), in the standard group to 257/360 (71%) in the rapid group (difference in means 8.6%, p = 0.002). The incorrect use of adenosine was decreased from 43/240 (18%) in the standard group to 32/240 (13%) in the rapid group (difference in means 4.5%, p = 0.06). In conclusion, correct diagnosis of difficult narrow complex tachycardias was improved when EKGs at both 25 mm/s and 50 mm/s were used for interpretation. It appears that the simple technique of increasing the EKG paper speed, and thus effectively spacing out the rhythm, enhances the diagnostic ability of the observer.