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Three Part Question

In [patients with suspected acute coronary syndromes in the ED] does [measuring ST segment elevation at the J point or 60 ms after the J point] enable [more accurate diagnosis of acute coronary occlusion]?

Clinical Scenario

A patient presents to the emergency department (ED) with a suspected acute coronary syndrome. The ECG shows ST elevation, which almost meets the criteria for the diagnosis of ST elevation myocardial infarction (STEMI) when measured at the J point. If measured 60 ms after the J point, the ECG meets criteria for diagnosing STEMI. You wonder if there is any evidence to determine whether ST elevation should be measured at the J point, as stipulated in international guidance (Thygesen et al, 2012), or 60 ms after the J point)

Search Strategy

We searched the following databases using the Ovid interface: EBM Reviews—Cochrane Database of Systematic Reviews 2005 to August 2014, EBM Reviews—ACP Journal Club 1991 to September 2014, EBM Reviews—Database of Abstracts of Reviews of Effects 3rd Quarter 2014, Ovid MEDLINE(R) 1946 to September Week 4 2014, Embase 1974 to 2014 Week 40
[ST segment.mp. OR STEMI.mp. OR exp ST segment elevation myocardial infarction/ OR exp ST segment/] or [Percutaneous Coronary Intervention.mp. OR PCI.mp. OR exp Percutaneous Coronary intervention/] AND [60 ms.mp. OR 60 milliseconds.mp.]

Search Outcome

We identified a total of 155 papers. After removal of duplicates, 96 papers remained. Following review, there were three papers that related to the three-part question

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Seo et al, 2011, South Korea	Patients presenting to the ED. Cohort of those identified as having inferior myocardial infarction on angiography (LCx or RCA occlusion). 88 patients who were initially diagnosed as STEMI and received immediate PCI as per protocol. 109 patients with NSTEMI picture who received PCI after cardiac enzyme rise	Retrospective cohort	Culprit lesion identified by interventional cardiologist.	STE group culprit lesion: 76 RCA, 11, LCx, 1 RCA and LCx NSTEMI group culprit lesion; 77 RCA, 26 LCx, 6 RCA and LCx	No data on whether occlusion was critical (>70%) or not. No effort made to ensure reliability of angiography findings. Retrospective. Selection bias. p Values are large. Only looks at inferior myocardial infarctions, so no review of precordial leads
			STE change at J point and 60 ms after. STE defined by two investigators blinded to angiography and clinical data Rater 1	J point - STE group n=81 (92%). 60 ms n=85 (97%) p= 0.165 Control group - J point n=8 (7%). 60 mins n=11 (10%) p=0.315
			STE change at J point and 60 ms after. STE defined by two investigators blinded to angiography and clinical data Rater 2	J point - STE group n=78 (89%). 60 ms n=83 p=0.14 Control group - J point n=6 (6%). 60 ms n=n=8 (7%) p=0.392
Smith et al, 2011, USA	ECGs of consecutive patients undergoing coronary intervention for proven acute LAD occlusion, and a control group of consecutive ED non-cardiac chest pain patients (three negative troponins) with ECGs coded as early repolarisation	Retrospective cohort study at two tertiary centres	Sensitivity and specificity for LAD occlusion using four criteria J point	2 mm in V1–V3 or 1 mm in V4–V6 Sn 61, Sp 55 1 mm in V1 and V4–V6 or 2 mm V2–V3 (male)/1.5 mm V2–V3 (female) Sn 67, Sp 47 1 mm in V1, V4–V6 or 2 mm V2–V3 (male), 2.5 mm V2–V3 (male <40 years old), 1.5 mm V2–V3 (female) Sn 67, Sp 54 1 mm V5–V6 or 2 mm V1–V4 Sn 57, Sp 66	Conference presentation so abstract only. No detail in abstract relating to inter-observer reliability
			Sensitivity and specificity for LAD occlusion using four criteria 60 min post J point	2 mm in V1–V3 or 1 mm in V4–V6 Sn 83, Sp 29 1 mm in V1 and V4–V6 or 2 mm V2–V3 (male)/1.5 mm V2–V3 (female) Sn 92, Sp 18 1 mm in V1, V4–V6 or 2 mm V2–V3 (male), 2.5 mm V2–V3 (male <40 years old), 1.5 mm V2–V3 (female) Sn 92, Sp 25 1 mm V5–V6 or 2 mm V1–V4 Sn 80, Sp 36
			Then illustrated how Smith's own decision rule performs at differentiating LAD occlusion from early repolarisation)	Sn 86, Sp 91 (decision rule is measured at 60 ms
Smith SW, 2006, USA	159 patients coded as anterior MI. 51 admitted through ED for primary PCI. 37 met inclusion criteria	Retrospective cohort study of the 37 patients	Number of patients who had STE Rater 1	1 mm STE in two consecutive leads -J point 32 (86%). 60 ms after 36 (97% p=0.10 2 mm STE in two consecutive leads - J point 22 (59%). 60 mins after 30 (81%) p=0.04 ST score >6 mm in V1-6 -J point 26 (70%). 60 mins after 33 (89%) p=0.04	Retrospective study that focused on anterior MIs only. Small cohort. Selection bias relying on correct coding; there may have been patients who were not labelled as anterior MI who this study missed
			Number of patients who had STE Rater 2	1 mm STE in two consecutive leads - J point 32 (86%). 60 mins after 36 (97%) p=0.10 2 mm STE in two consecutive leads - J point 25 (68%). 60 mins 30 (81%) p=0.14 ST score >6 mm in V1–V6 - J point 26 (70%). 60 mins after 32 (86%) p=0.08

Comment(s)

As one would expect, ST elevation measurements change depending where the measurement is taken from. There is limited evidence that measuring STE further away from the J point can improve sensitivity while specificity drops. There is no evidence, however, that such a move would reduce mortality if these patients were offered immediate revascularisation, for example. Further research in this area is warranted.

Editor Comment

ED, emergency department; MI, myocardial infarction; NSTEMI, non-ST elevation myocardial infarction; PCI, percutaneous coronary intervention; STEMI, ST elevation myocardial infarction; RCA, right coronary artery; STE, ST elevation; LCx, left circumflex artery; LAD, left anterior descending artery.

Clinical Bottom Line

With the current evidence, measurement of ST elevation at a different location to the J point cannot be advocated.

References

1. Thygesen K, Alpert JS, Jaffe AS, et al. Third universal definition of myocardial infarction. Third universal definition of myocardial infarction. J Am Coll Cardiol 2012;60:1581–98.
2. Seo D-W, Sohn CH, Ryu JM, et al. ST elevation measurements differ in patients with inferior myocardial infarction and right ventricular infarction. Am J Emerg Med 2011;29:1067–73.
3. Smith SW, Scharrer E, Khalil A, et al. 371 Performance of ST-Elevation Criteria for Anterior STEMI, and Comparison With a Decision Rule for Differentiation From Early Repolarization. Ann Emerg Med 2011;58:S303.
4. Smith SW. ST segment elevation differs depending on the method of measurement. Acad Emerg Med 2006;13:406–12.