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Differential diagnosis of narrow complex tachycardias by increasing electrocardiograph speed
  1. Joao Luis Gaspar, Medical student,
  2. Richard Body, Clinical Research Fellow
  1. Department of Emergency Medicine, Manchester Royal Infirmary, Oxford Road, Manchester M13 9WL, UK;


    A shortcut review was carried out to establish whether increasing the paper speed during ECG recording could improve the accuracy of diagnosis of narrow complex tacycardias. Altogether 256 papers were found using the reported search, of which one presented the best evidence to answer the clinical question. The author, date, and country of publication, patient group studied, study type, relevant outcomes, results, and study weaknesses of these best papers are tabulated in table 2. It is concluded that increasing paper speed does indeed improve diagnostic accuracy.

    • ECG
    • electrocardiogram speed
    • arrow complex tachycardia

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    Clinical scenario

    A 60 year old Asian female, who speaks little English, is brought to the emergency department with what seems to be a three day history of worsening exertional dyspnoea and a 3 hour history of resting dyspnoea with light-headedness. On examination she is apyrexial with a pulse of 150 beats/min, a respiratory rate of 20/min, blood pressure 100/60, and oxygen saturation 93% in air. A 12-lead ECG is recorded, which reveals a rapid narrow complex tachycardia. Interpretation of P wave activity is difficult because of the rapid heart rate and you cannot be entirely sure whether this is atrial flutter, junctional tachycardia, or sinus tachycardia. You wonder if increasing the ECG speed will help you to make a more accurate diagnosis.

    Three part question

    In [adults with narrow complex tachycardia] does [increased electrocardiograph speed] improve [sucess in identifying the type of narrow complex tachycardia]?

    Search strategy

    Medline OVID interface 1966 to week 1 July 2005. EMBASE using the Dialog Datastar interface 1974 to week 1 July 2005. CINAHL using the OVID interface 1982 to week 4 June 2005.

    OVID: [exp Tachycardia, Supraventricular/OR exp Tachycardia, Paroxysmal/OR exp Atrial Flutter/OR exp Tachycardia, Atrioventricular Nodal Reentry/OR exp Tachycardia/OR exp Atrial Fibrillation/OR exp Tachycardia, Sinus/OR (narrow complex tachycardia OR SVT).mp.] AND [exp Electrocardiography/OR (ECG OR EKG OR electrocard$).mp.] AND [exp Diagnosis, Differential/OR (diagnos$ OR differential$).mp.] AND [exp Time Factors/OR OR (25 mm$ OR 50 mm$ OR velocity$).mp.]. LIMIT to human and English language.

    EMBASE: [ OR OR OR OR OR OR] AND [ OR OR OR OR electrocardiogra$.mp.] AND [diagnos$.mp. OR differential$.mp.] AND [ OR OR OR 25 mm$.mp. OR 50 mm$.mp.]. LIMIT to human and English language.

    CINAHL: [ OR OR OR OR OR OR OR (narrow ADJ complex ADJ tachycardia).mp. OR] AND [ OR OR OR electrocardiogra$.mp.] AND [diagnos$.mp. OR differential$.mp.] AND [ OR OR 25 mm$.mp. OR 50 mm$.mp.]. LIMIT to human and English language.

    Cochrane: [(exp MeSH headings: Tachycardia, Supraventricular OR Atrial Fibrillation OR Atrial Flutter OR Tachycardia, Ectopic Juntional) OR SVT OR narrow complex tachycardia] AND [(exp MeSH heading Electrocardiography) OR ECG OR EKG] AND [exp MeSH headings Diagnosis, Differential OR Diagnosis] AND [speed OR velocity OR 25 mm* OR 50 mm*].

    Search outcome

    Using the reported searches, 116 papers were identified using OVID Medline, 216 using EMBASE, 8 using CINAHL, and 6 using Cochrane. Only one paper, which had been identified using both OVID Medline and EMBASE, was relevant to the three part question.


    There is a subgroup of patients with narrow complex tachycardia who are difficult to diagnose using the initial 12-lead ECG. A trial of adenosine is often used to aid diagnosis but this often causes significant side effects to the patient and some quite literally heart stopping moments for patient and physician alike. The idea of a simple, quick, non-invasive test such as the 50 mm/s ECG to aid diagnosis is therefore attractive.

    The only study to investigate the clinical utility of this strategy suggests that the addition of a 50 mm/s ECG to a standard 25 mm/s ECG improves diagnostic accuracy in narrow complex tachycardia. The study suggests that inappropriate use of adenosine may be reduced by implementing this strategy, as interpreters are more likely to correctly diagnose difficult tracings.


    A 50 mm/s ECG should be considered when differential diagnosis of narrow complex tachycardia is difficult.

    Table 2



    • Report by Joao Luis Gaspar, Medical studentSearch checked by Richard Body, Clinical Research Fellow