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aVR ST‐segment changes and prognosis of ST‐segment elevation myocardial infarction

Abstract Background Clinical importance of aVR lead‐related changes in predicting the prognosis of acute myocardial infarction remains uncertain. The present study aimed to assess the value of ST‐segment changes in aVR lead and the outcome and sequels of the first episode of acute ST‐segment elevation myocardial infarction. Methods This prospective cohort study was conducted on patients suffering first episode of ST‐segment elevation myocardial infarction and underwent percutaneous coronary intervention. Information was collected through hospital‐recorded files reading. The electrocardiogram (ECG) was taken from the patients upon entering the hospital and followed‐up for 30 days to assess cardiovascular complications. Results In patients with anterior STEMI, with the use of multivariate analysis, admission aVR ST elevation ≥1 mm was found to be a strong and independent predictor of major cardiovascular adverse events (MACE) within 30 days of discharging (P value for trend .002). In patients with inferior (± RV) ST‐segment elevation myocardial infarction (STEMI), with the use of multivariate analysis, admission aVR ST depression ≥1 mm was found to be a strong and independent predictor of MACE within 30 days of discharging (P value for trend .01). Conclusion In patients with anterior STEMI, admission aVR STE ≥1 mm was found to be a strong and independent predictor of MACE within 30 days of discharging. On the other hand, in patients with inferior STEMI, aVR ST depression ≥1 mm was found to be a strong and independent predictor of MACE within 30 days of discharging.


| INTRODUCTION
Lead aVR on electrocardiogram as a unipolar and augmented limb lead can present valuable and specific information from the right upper portion of the heart. It is well established that ST-segment changes in the aVR lead are associated with three coronary vessels involvement or left main disease in patients suffering acute coronary syndrome (ACS). 1,2 These changes have been accepted as a main source for additional information to determine culprit lesions and thus for predicting poor prognosis especially in patients with ST-segment elevation myocardial infarction (STEMI). 3,4 The pathological change in ST segment in lead aVR is closely linked to anterior STEMI; however, these segmental changes among those with inferior STEMI remain inconsistent. 5 Additionally, some studies could only determine the value of ST-segment (g) Selvester Score (which estimates the size and location of myocardial scar in the left ventricle and calculated based on based on Q-or R-wave duration, R-or S-wave amplitude and R/Q or R/S amplitude ratios as previously described [11]), and (h) Aldrich score (which was calculated using the following formula (anterior STEMI: 3 Â   Table 2, the serum level of triglyceride was only different in anterior MI patients due to ST changes in the aVR lead so that in patients with ST ranged À1 mm and + 1 mm was significantly lower than other groups with different ST patterns. However, ST-segment changes had no effect on patients' LVEF. In inferior MI subgroup, mean SUM STE was significantly high in the patients with ST <À1 mm as compared to those with ST ranged À1 mm and + 1 mm (P = .003). In anterior MI subgroup, MAX STE was significantly higher in patients with ST < À1 mm (P < .001), while ST-segment resolution was significantly the lowest in those with ST ranged À1 mm and + 1 mm (P = .04). Also, in the subgroups with inferior/right ventricle MI, SUM STE was significantly higher in the patients with ST < À1 mm as compared to those with ST ranged À1 mm and + 1 mm (P = .04). Mean Aldrich score was also lower, and also ST-segment resolution was higher in those with ST < À1 mm (P = .05) as compared to other ST subgroups ( Table 3). As indicated in Table 4, none of the angiographic findings was significantly associated with ST-segment changes in the aVR lead. There was no significant association between the site of infarct in each type of vessel involvement and ST-segment changes in the aVR lead (Table 5).
With regard to the patients' prognosis, in anterior MI subgroup ( Figure 1), reinfarction, and cardiac death were significantly higher in patients with ST >+1 mm than those with other ST patterns. Also, in inferior/right ventricle MI subgroup, reinfarction and cardiac death occurred more in those with aVR ST depression ≥1 mm. In anterior MI subgroup, three coronary vessels involvement was found more in those with ST >+1 mm. The use of integrilin in anterior MI, inferior MI, and inferior/right ventricle MI subgroups was reported to be 80%, 75%, and 75%, respectively, with no difference.
In 25 consecutive patients with first episode of STEMI, we prospectively evaluated admission ECG for aVR lead ST elevation ≥1 mm and aVR lead ST depression ≥1 mm.
In patients with anterior STEMI, with the use of multivariate analysis, admission aVR ST elevation ≥1 mm was found to be a strong and independent predictor of MACE within 30 days of discharging (P value for trend .002).
In patients with inferior (± RV) STEMI, with the use of multivariate analysis, admission aVR ST depression ≥1 mm was found to be a strong and independent predictor of MACE within 30 days of discharging (P value for trend .01).

| DISCUSSION
ECG, as an available noninvasive method, has been used worldwide for more than 70 years to diagnose ischemic heart diseases. Of the 12 leads studied in the ECG, the aVR lead can be considered the most  11 The last thoracic lead (V6) is located in the axillary midline, and a V7 lead in the axillary dorsal line can show extensive ischemia of the heart apex more clearly.
This finding indicates the importance of the mirror image in aVR, which is mostly a reflection of ischemia in the apex of the heart, and shows the mirror image of the V7 lead more than other leads. This means that ST depression more in the aVR lead indicates more ST elevation not only in V5 and V6 but also in V7. 12 The use of ST-segment, T-wave, and Q-wave in the aVR lead to evaluate the current or past status of previous or current MI patients has been suggested in various studies. 13 In 2012, Kukla et al 14 reported that the changes in the aVR lead occurred in half of the patients with MI and were significantly associated with poor disease prognosis.
In this study, we showed that in patients with anterior MI, MAX STE was significantly higher in patients with ST < À1 mm and significantly lower in patients with ST > +1 mm. Also, ST-segment resolution was significantly lower in patients À1 mm < ST < + 1 mm.
Regarding the anatomy of coronary artery involvement and its relationship with changes in the aVR lead, no significant relationship was found in our study. However, in anterior MI patients, ST elevation in aVR was associated with greater three coronary vessels involvement.
This finding has also been reported in the study of Beyranvand et al. 15 We showed in this study that in patients with inferior MI, SUM STE was significantly higher in patients with ST < À1 mm. Such patients had also slightly higher Selvester score. Additionally, in patients suffering inferior plus right ventricle MI patients, SUM STE was significantly higher in patients with ST < À1 mm compared to patients with

| CONCLUSION
In patients with anterior STEMI, admission aVR STE ≥1 mm was found to be a strong and independent predictor of MACE within 30 days of discharging. On the other hand, in patients with inferior STEMI, aVR ST depression ≥1 mm was found to be a strong and independent predictor of MACE within 30 days of discharging.

FUNDING
None.

CONFLICT OF INTEREST
The authors have stated explicitly that there are no conflicts of interest in connection with this article. Mani Hassanzadeh had full access to all of the data in this study and takes complete responsibility for the integrity of the data and the accuracy of the data analysis.

TRANSPARENCY STATEMENT
The corresponding author affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned (and, if relevant, registered) have been explained.

DATA AVAILABILITY STATEMENT
The data that support the findings of this study are available from the corresponding author upon reasonable request.

ETHICS STATEMENT
This study was approved by the Ethics Committee of the Shiraz University of Medical Sciences (IR.SUMS.MED.REC.1398.552).