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Three Part Question

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

Clinical Scenario

A 60 year-old Asian lady, 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 three-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 supraventricular tachycardia. Interpretation of P wave activity is difficult due to 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.

Search Strategy

Medline using the OVID interface 1966 to July Week 1 2005
EMBASE using the Dialog Datastar interface 1974 - July Week 1 2005
CINAHL using the OVID interface 1982 to June Week 4 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$).mp.] AND [exp Time Factors/ OR speed.af. OR (25mm$ OR 50mm$ OR velocity$).mp.] limit to human and English language
EMBASE:
[SUPRAVENTRICULAR-TACHYCARDIA#.DE. OR TACHYCARDIA#.W..DE. OR REENTRY-TACHYCARDIA#.DE. OR PAROXYSMAL-SUPRAVENTRICULAR-TACHYCARDIA#.DE. OR HEART-ARRHYTHMIA#.DE. OR HEART-ATRIUM-FIBRILLATION#.DE. OR SVT.mp.] AND [ELECTROCARDIOGRAPHY#.W..DE. OR ECG-ABNORMALITY#.DE. OR ECG.MP. OR EKG.MP. OR electrocardiogra$.mp.] AND [diagnos$.mp. OR differential$.mp.] AND [TIME#.W..DE. OR speed.mp. OR velocity.mp. OR 25mm$.mp. OR 50mm$.mp.] limit to human and English language
CINAHL:
[TACHYCARDIA-SUPRAVENTRICULAR#.DE. OR ARRHYTHMIA#.W..DE. OR TACHYCARDIA#.W..DE. OR ARRHYTHMIA-ATRIAL#.DE. OR TACHYCARDIA-ATRIAL#.DE. OR ATRIAL-FIBRILLATION#.DE. OR ATRIAL-FLUTTER#.DE. OR (narrow ADJ complex ADJ tachycardia).mp. OR SVT.mp.] AND [ELECTROCARDIOGRAPHY#.W..DE. OR ECG.mp. OR EKG.mp. OR electrocardiogra$.mp.] AND [diagnos$.mp. OR differential$.mp.] AND [speed.mp. OR velocity.mp. OR 25mm$.mp. OR 50mm$.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 25mm* OR 50mm*]

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.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Accardi AJ et al, 2002, USA	45 patients with difficult narrow complex tachycardia (heart rate range: 150-250 beats/min) 8 Emergency physicians reviewed the ECG's, blinded to clinical information. Definitive diagnosis depended upon agreement between the 'official diagnosis' in the case notes and a cardiologist who reviewed each case.	Prospective comparative cohort	Correct ECG diagnosis	63% 25 mm/s standard group vs 71% 50 mm/s ECG; difference in means 8.6% (95% CI 2, 15%) p=0.002	Small numbers Definitive diagnosis was potentially inaccurate. Review of 25mm/sec ECG's was followed by review of 50mm/sec ECG's two weeks later. The reviewers may have learned more about ECG diagnosis in that time, biasing the results. Intraobserver variability should have been assessed.
			Correct ECG diagnosis of atrial flutter	40% 25 mm/s standard group vs 52% 50 mm/s ECG difference in means 12.5% (95% CI 1, 24%); p=0.008
			Correct diagnosis of atrial fibrillation	85% 25 mm/s standard group vs 90% 50 mm/s ECG difference in means 4.5% (95% CI -5, 14%); p=0.046
			Correct diagnosis of PSVT	73% 25 mm/s standard group vs 78% 50 mm/s ECG difference in means 5% (95% CI -6, 16%); p=0.18
			correct diagnosis of sinus tachycardia	56% 25 mm/s standard group vs 81% 50 mm/s ECG

Comment(s)

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 if 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 50mm/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 25mm/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.

Clinical Bottom Line

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

References

1. Accardi AJ, Miller R, Holmes JF Enhanced Diagnosis of Narrow Complex Tachycardias With Increased Electrocardiographic Speed The Journal of Emergency Medicine 2002; 22(2): 123-126