The delayed activation wave in non-ST-elevation myocardial infarction

NSTEMI with total left circumflex occlusion: how the N-wave might help (case report)

A rise and/or fall in troponin level is an indication of type 1 or 2 myocardial infarct. A 62-year-old male physician presented to emergency room with chest discomfort followed by thought to be normal electrocardiogram (ECG) and normal echocardiography results. His serial hs-troponin test showed remarkable escalation three hours from the initial (107 ng/l into 4.978 ng/l), suggesting a high-risk non-ST-segment myocardial infarction (NSTEMI). An early invasive procedure was performed, showing acute total occlusion (TO) in the obtuse marginal 1 branch. We retrospectively reviewed our examination to diagnose better the presence of TO in NSTEMI patients presented with non-diagnostic examination. Our evaluation showed a minor change in the form of an ‘N-wave’ pattern on the ECG, which was not yet an established guideline criterion for prompt angiography. Although ECG pattern is often normal in LCx occlusion, recent study shows the presence of ‘N-wave’ ECG pattern in 10% of NSTEMI cases following TO at LCx.

Electrocardiographic identification of the culprit coronary artery in acute non-ST-elevation myocardial infarction: predictive value of N-wave and T-wave precordial instability

BACKGROUND

Recently, novel ischemic electrocardiographic changes have been described, which may be clinically significant in the identification of the culprit coronary vessel in patients with non-ST-elevation myocardial infarction (NSTEMI). We sought to determine the predictive value of N-wave, T-wave precordial instability, de-Winter ST/T-wave complex, and inferolateral myocardial infarction in the identification of the culprit artery in patients with NSTEMI referred for early invasive (<24 h) treatment.

METHODS

A total of 148 patients with NSTEMI, aged 40-91 years, were enrolled from a cohort of 510 consecutive NSTEMI subjects, hospitalized in our center in 2015-2017.

RESULTS

Of the evaluated ischemic ECG changes, the most common finding in patients with culprit left circumflex (LCx)/obtuse marginal artery or right coronary artery was T-wave precordial instability (28.3 and 13.5%, respectively), whereas in individuals with culprit left anterior descending/diagonal artery, T-wave precordial instability and N-wave in leads II, III or aVF occurred equally often (16.0%). A significant relationship was found between the occurrence of N-wave in inferolateral leads and culprit LCx/obtuse marginal. In multivariable analysis, N-wave in lead aVL [odds ratio (OR) 2.10; 95% confidence interval (CI), 1.15-3.81], and T-wave precordial instability (OR 1.56; 95% CI, 1.02-2.41) were independent predictors of culprit LCx/obtuse marginal. The accuracy of N-wave in lead aVL in predicting the culprit LCx/obtuse marginal was 73.9% and was higher than the accuracy of T-wave precordial instability, which was 69.1%.

CONCLUSIONS

In patients with NSTEMI referred for early invasive treatment, the presence of N-wave or T-wave precordial instability may be of greater clinical importance in the prediction of culprit LCx/obtuse marginal than classic ischemic changes.

Non-ST-elevated myocardial infarction with "N" wave on electrocardiogram and culprit vessel in left circumflex has a risk equivalent to ST-elevated myocardial infarction

Background

It was found that delayed activation wave often appeared in terminal QRS wave in non‐ST‐elevated myocardial infarction (NSTEMI) with culprit vessel in left circumflex artery (LCX), yet little is known about the similarities among non‐“N”‐wave non‐ST‐elevated myocardial infarction (N‐NSTEMI) and ST‐elevated myocardial infarction (STEMI).

Hypothesis

In AMI patients with the culprit vessel in LCX, “N” wave NSTEMI has a risk equivalent to STEMI.

Methods

All 874 patients admitted to Shenjing Hospital of China Medical University between January 1, 2013 and December 30, 2017 were included and whose coronary angiography (CAG) indicated the culprit vessel in LCX. Patients were divided into three groups: ST‐elevated myocardial infarction group (STEMI group, n = 322), “N” wave non‐ST‐elevated myocardial infarction group (N‐NSTEMI group, n = 232) and non‐“N”‐wave NSTEMI group (non N‐NSTEMI group, n = 320). The basic data and the incidence of MACE during hospitalization and 12 months were analyzed.

Results

In STEMI and N‐NSTEMI groups, AST, CK, CK‐MB, TnI, and stenosis severity were significantly higher than non N‐NSTEMI (P < .05). The lesions in the N‐NSTEMI and STEMI groups were more often located proximal LCX before giving rise to OM1 of LCX (P < .05), however, the non N‐NSTEMI group was often located distal LCX after giving rise to OM1 and the OM1 (P < .05). The incidence rates of all MACEs, all‐cause death, ST, TVR, and rUAP were similar in N‐NSTEMI and STEMI groups, which were greater than non N‐NSTEMI (P < .05). Both N‐NSTEMI and STEMI are independent risk factors for MACE (P < .05).

Conclusion

The basic data and the incidence of major adverse cardiac event were similar in N‐NSTEMI and STEMI patients, N‐NSTEMI has a risk equivalent to acute STEMI.

Novel ECG changes in acute coronary syndromes. Would improvement in the recognition of 'STEMI-equivalents' affect time until reperfusion?

Current guidelines recommend that patients with non-ST elevation myocardial infarction (NSTEMI) are treated with medical management alone, or in combination with coronary angiography within 24 h. Recent research suggests that NSTEMIs show angiographic evidence of complete occlusion at rates comparable to STEMIs, suggesting a subgroup of NSTEMI patients who require urgent angiography. Novel ECG changes, termed 'STEMI-equivalents', have been described as a way of identifying this subgroup. The aim of this study was to determine whether patients with STEMI-equivalent ECG changes experience similar degrees of myocardial damage, and would thus benefit from urgent PCI. Cardiac catheterisation databases at The Wollongong Hospital were searched for STEMI, and NSTEMI patients with complete occlusion of the culprit vessel, between January 2011 and December 2013. A total of 1429 patients underwent angiography during this time period. Of these, 220 were eligible for ECG analysis. We found 10-25% of NSTEMIs with 'STEMI equivalent' ECG changes correlated with complete vessel occlusion on angiography. These patients demonstrated equivalent initial troponin readings. Recognition of STEMI-equivalents represent a chance for earlier intervention with prompt coronary angiography, as these findings are often associated with complete occlusion of the culprit vessel. These findings provide further evidence supporting the potential inclusion of STEMI-equivalents in future ACS guidelines.