• 
• 

Three Part Question

In [a patient presenting with features suggestive of pulmonary embolus] what is [the diagnostic utility of ECG] in [stratifying risk of pulmonary embolus]?

Clinical Scenario

A thirty year old man presents to the emergency department with a spontaneous onset of atraumatic pleuritic chest pain. He is in a low risk group clinically. The medical registrar suggests that the fact that the ECG is normal makes the diagnosis of pulmonary embolus much less likely. You wonder whether his assertion that a normal ECG will help to exclude a pulmonary embolus is safe.

Search Strategy

Medline OVID 1966-week 4 June 2005
The Cochrane Library Issue 1 2005
[exp Pulmonary Embolism OR exp THROMBOEMBOLISM OR PE.mp OR pulmonary infarct$.mp OR Pulmonary Embol$.mp] AND [exp Electrocardiography OR Electrocardio$.mp OR ECG.mp OR EKG.mp] LIMIT to human AND English.
[{Pulmonary embolism MeSH OR thromboembolism MeSH}] AND [{electrocardiography MeSH}]

Search Outcome

952 papers were found of which 947 were not directly relevant to the question, were of insufficient quality or did not report enough data to assess the diagnostic utility of ECG or a scoring system in which it was included. The remaining papers are summarised in the table below.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Stollberger C et al, 2000, Austria	168 (derivation) and 139 (validation) inpatients suspected of pulmonary embolus	Prospective Derivation/Validation study	Risk factors, objective clinical signs, LDH, ECG ('signs of Right heart strain'), Arterial blood gases, Venography/Plethysmography results and Chest X-Ray recorded Multivariate logistic regression established those associated with the diagnosis of PE	Individual signs 16-48% sensitive for PE, 83-94% specific	Small sample size Inpatient population only
			'PE Score' (including ECG signs of Right heart strain) developed and validated in second group	PE score's performance is reported for 17 different scores in paper. Examples are given below: PE score >0.3 Sn100%, Sp 79% PE Score >0.5 Sn 70%, Sp 99%
Rodger M et al, 2000, Canada	212 consecutive patients referred for V/Q or Pulmonary angiogram for suspected PE	Prospective validation of previously derived scoring system	Prevalence of 28 ECG abnormalities in those subsequently diagnosed as PE positive (49) or negative (163)	Only 2 abnormalities (tachycardia and incomplete RBBB) significantly more prevalent in PE positive than PE negative patients	Small numbers (possibility of false negative results)
			Diagnostic utility of ECG scoring system (previously derived in patients diagnosed as PE positive) assessed for validation	Positive and negative predictive values of scoring system 57.1 and 81.7 respectively
Miniati M et al, 2003, Italy	1100 consecutive patients referred for investigation for PE	Derivation/Cross Validation study	Objective signs, risk factors, ECG and CXR recorded. Multivariate logistic regression established those associated with the diagnosis of PE	Scoring system (included ECG signs of right heart strain) developed which divides patients into low, intermediate, moderately high and high groups Pre-test probability by group Low- 4% Intermediate- 22% Moderately high- 74% High- 98%	Subjective inclusion criteria No prospective validation study (cross validation only)
Richman PB et al, 2004, USA	Patients assessed for pulmonary embolus over 1 year. 49 with PE compared to 49 without	Observational	ECG changes classically associated with PE	Sinus tachycardia (18.8%vs 11.8%), Incomplete RBBB (4.2% vs 0%), S1Q3T3 (2.1% vs 0%) S1Q3 (0 vs 0)	Incomplete cohort used in that 252 patients investigated for PE were not used in analysis
Sinha N et al, 2005, USA	Patients undergoing CT pulmonary angiography at a tertiary hospital over 30 months	Retrospective cohort	ECG changes significantly associated with PE	Sinus tachycardia (39% vs 24%) Atrial tachyarhythmias (15% vs 4%) Q3 (40% vs 26%) Q3T3 (8% vs 1%)

Comment(s)

While it is clear that there are some ECG changes that occur more frequently in patients with PE, these occur infrequently. There is no evidence that an ECG alone has adequate sensitivity or specificity to rule out or in a pulmonary embolus. It may have utility as part of risk stratification strategies.

Clinical Bottom Line

An ECG alone is of little value in the diagnosis of pulmonary embolus. Its main value is in ruling out other causes of the presenting symptoms, or as part of a risk stratification strategy to inform a further investigative protocol.

References

1. Stollberger C, Finsterer J, Lutz W, et al. Multivariate Analysis-Based Prediction Rule for Pulmonary Embolism. Thrombosis Research 2000:97;267-273.
2. Rodger M, Makropolous D, Turek M, et al. Diagnostic value of the Electrocardiogram in Suspected Pulmonary Embolism. American Journal of Cardiology 2000:86;807-809.
3. Miniati M, Monti S, Bottai M. A structured clinical model for predicting the probability of pulmonary embolism. Am J Med 2003;114:173-9.
4. Richman PB, Louti H, Lester SJ et al. Electrocardiographic findings in Emergency Department patients with pulmonary embolism. J Emerg Med 2004;27:121-6.
5. Sinha N, Yalamanchili K, Sukhija R et al. Role of the 12-lead electrocardiogram in diagnosing pulmonary embolism. Cardiol in review 2005;13:46-9.