Lead aVR: Importance of the "Forgotten 12th Lead" in Patients With ACS

Amal Mattu, MD, FAAEM, FACEP


April 06, 2009


In recent years, more studies have demonstrated the importance of lead aVR during the analysis of the 12-lead electrocardiogram (ECG) in patients with acute coronary syndrome (ACS). These studies have indicated that lead aVR is a strong predictor of left main coronary artery (LMCA) occlusion when used in isolation[1] or in conjunction with other leads.[2] Studies have indicated that the presence of simultaneous ST-segment elevation (STE) in leads aVR + aVL[3] or the presence of STE in aVR that exceeds the amount of STE in lead V1[4,5] is highly specific for LMCA occlusion in patients with ACS. Other studies have discussed STE in lead aVR in less specific terms, simply citing that this finding is indicative of either LMCA occlusion or left anterior artery occlusion,[6,7] or indicative of either LMCA occlusion or triple-vessel disease.[8] The magnitude of STE in lead aVR that is considered significant is inconsistent among these articles; some articles have evaluated any STE in aVR, whereas others have focused on STE greater than 1 mm. This difference may account for the varying specificities for LMCA involvement. Regardless, the literature continues to show with increasing consistency that STE in lead aVR in patients with ACS is associated with more ominous coronary occlusions. Patients with LMCA occlusions, left anterior artery occlusions, or triple-vessel occlusions have a worse prognosis, requiring more aggressive immediate therapy and often bypass surgery. Emergency physicians who find ECG predictors of any of these 3 conditions in their patients with ACS (whether ST-segment elevation myocardial infarction [STEMI] or non-STE ACS) would be prudent to mobilize resources for rapid invasive therapy. Additionally, because many of these patients will require coronary artery bypass grafting, it certainly seems advisable to withhold clopidogrel.[4] Below is a summary of one more study that adds to the literature indicating that STE in lead aVR predicts more pronounced coronary occlusions and a worse prognosis.

Admission ST-Segment Elevation in Lead aVR as the Factor Improving Complex Risk Stratification in Acute Coronary Syndromes

Szymanski FM, Grabowski M, Filipiak KJ, Karpinski G, Opolski G
Am J Emerg Med. 2008;26:408-412


Szymanski and colleagues evaluated the association of STE in lead aVR with mortality. The investigators assessed 205 consecutive patients with non-STEMI ACS for STE in lead aVR of at least 0.5 mm. Patients were divided into 3 risk groups on the basis of their Thrombolysis in Myocardial Infarction (TIMI) risk score,[9] a validated ACS scoring system that is used to gauge 14-day risk for adverse outcome in patients admitted with ACS. Low-risk patients had 0-2 points; intermediate-risk patients had 3-4 points; and high-risk patients had 5-7 points on the TIMI scale. STE in lead aVR was found in 114 patients. The researchers found that the presence of STE in aVR was a strong and independent predictor of 30-day mortality (odds ratio, 7.8). During this 30-day period, 18 patients (8.8%) died. Of those who died, 16 of 18 (88.9%) had STE in aVR vs 98 of 187 (52.4%) of the survivors who had STE in aVR. Mortality also increased with the severity of STE in aVR. Mortality was 2 of 91 (2.2%) for patients without STE in aVR, 8 of 74 (10.8%) for patients with STE of 0.5 mm, 4 of 29 (13.8%) for patients with STE of 1 mm, 2 of 9 (22.2%) for patients with STE of 1.5-2.5 mm, and 2 of 4 (50%) for patients with STE of ≥ 3 mm. The increases in mortality were statistically significant.


When considering the TIMI risk stratification scores, the researchers discovered that patients with STE in aVR, when compared with patients without STE in aVR, had higher death rates in the low-risk (18.5% vs 0%) and intermediate-risk groups (15.5% vs 2.6%). The study authors concluded that STE in lead aVR in patients with ACS was a good predictor of short-term mortality and could be used synergistically with TIMI scores for early stratification of risk. The takeaway point is simple: When patients with ACS, including non-STE ACS, demonstrate STE in lead aVR, the aggressiveness of early management must be increased. These patients have more complex coronary lesions and will likely benefit from earlier invasive therapy.



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