Correlation Between the Electrocardiogram and Regional Wall Motion Abnormalities as Detected by Echocardiography in Patient with Acute Anterior and Inferior Myocardial Infarction

Yochai Birnbaum, Mohammad Saeed, David Ware

The Division of Cardiology, University of Texas Medical Branch, Galveston, Texas, USA

Correspondence: Yochai Birnbaum, The Division of Cardiology, 5,106 John Sealy Annex, 301 University Blvd, Galveston, Texas 77555-0553, USA. E-mail: yobirnba@utmb.edu, phone +1 409 772 1533, fax +1 409 772 4982

1.    Introduction

The ECG classification of the subtypes of myocardial infarction (MI) is based on correlation between the distribution of the Q waves and autopsy findings. However, it is unclear whether ST deviation on the presenting ECG carries similar significance concerning regional myocardial involvement as Q waves in the same leads on the more advanced stage of MI. Several studies correlated ECG patterns with coronary angiography. However, data concerning correlation between ECG patterns and regional myocardial involvement are scarce.

We assessed the correlation between ST deviation on the presenting ECG and regional wall motion abnormalities (RWMA), as assessed by trans-thoracic echocardiogram in patients with first acute MI involving the inferior (n=109)[Golovchiner, 2002] and anterior wall (n=132)[Porter, 2000]. Our findings suggest that a new classification of inferior and anterior acute MI is warranted, based on the correlations between the ECG in the acute phase of MI to coronary angiographic findings and RWMA or segmental perfusion as assessed by echocardiography, radionuclide perfusion and magnetic resonance images.

2.    Material and Methods

In two separate retrospective studies we correlated the admission ECG findings with RWMA of the left ventricle, as assessed by trans-thoracic echocardiogram performed within 24 h of admission. We excluded patients with a history of previous MI, intraventricular conduction defects, ventricular or ventricular paced rhythm, left ventricular hypertrophy and patients without echocardiography study (most of these patients died shortly after admission).

ST depression (ST↓) was defined as ≥ 0.1 mV horizontal or downward sloping depression, ST elevation (ST↑) as ≥ 0.1 mV elevation, and isoelectric ST when the ST amplitude was greater than -0.1 mV but smaller than 0.1 mV. RWMA was assessed using the 16-segment method. Global wall motion score was calculated as the sum of the RWMA score in all 16 segments.

3.    Results

3.1. Inferior Acute MI

ST↓ in V1 and V2 was associated with RWMA of the mid-posterior segment (p<0.02 for both leads). The specificity of ST↓ in V1 and V2 for RWMA in mid-posterior segment was 87% and 57%, and the sensitivity 36% and 70%, respectively. Patients with ST↓ in V2 or V3 had worse global RWMA score then patients without ST↓ in these leads (p=0.009 and p=0.025, respectively). Patients with ST↑ in V1, but not in V2 or V3, had a higher prevalence of right ventricular involvement (88%, 21%,15%) in patients with ST↑, isoelectric ST or ST↓ in this lead; p< 0.0001). ST↑ in V5 was associated with more frequent involvement of the apical portion of the inferior wall (p<0.02), with specificity of 88% and sensitivity of 33%. Global RWMA score tended to be worse for patients with ST↑ in V5 (21.00±4.06; 20.26±3.10; and 22.17±3.76; for patients with ST↑, isoelectric ST, and ST↓, respectively; p=0.075). ST↑ in V6 was associated with RWMA in the mid-posterior segment (p<0.006), with specificity of 91% and sensitivity of 33%, and worse global RWMA score (20.69±3.71; 20.30±3.43; and 22.61±3.24, respectively; p=0.022).

3.2. Anterior Acute MI

ST↑ in I and aVL was not associated with specific pattern of regional dysfunction. ST↑ in the “inferior” leads was not associated with more apical or infero-posterior regional dysfunction. Basal anterior, anteroseptal and septal regional dysfunction were seen more often in patients with ST↑ in V1 (49% vs. 25% p=0.006; 37% vs. 19% p=0.027; 35% vs. 17% p=0.048, respectively). In contrast, patients with ST↑ in V2 had more RWMA in the apical inferior region (84% vs. 53%; p=0.01). ST↑ in V5 and V6 was not associated with more apical or lateral wall motion abnormalities.

4.    Discussion

The present studies are unique because we tried to correlate ST deviation in the presenting ECG with RWMA as assessed by echocardiography. Some of our findings are in disagreement with the classical ECG classification of acute MI and with ECG-coronary angiographic correlations.

4.1. Inferior Acute MI

ST↓ in leads V1-V2 is associated with RWMA in the mid-posterior segment. Other studies found an association between ST↓ in precordial leads with posterior wall involvement. We pinpointed this association to be with the mid-posterior segment, but not with the basal-posterior, apical-posterior, or the basal, mid or apical-inferior segments. Birnbaum, et al. using the angiographic substudy of the GUSTO-I study, found that patients with inferior acute MI and ST↓ in V1-V3 have less often proximal right artery occlusion, whereas there was no difference in the prevalence of mid or distal right coronary artery occlusion between patients with or without ST↓ in V1-V3. Proximal right artery occlusion may result in concomitant posterior left ventricular and right ventricle involvement. This may cause attenuation of ST↓ in V1-V3.

ST↑ in V6 is associated with RWMA in the mid-posterior segment and worse global RWMA score, but not with apical or lateral involvement, as is commonly believed. Thus, patients with inferior acute MI and ST↑ in V6 should probably be classified as “inferoposterior” and not “inferolateral” MI. Involvement of apical segment of inferior wall was found in relatively small number of patients (17%) and correlated with ST↑ in lead V5.

4.2. Anterior Acute MI

Previous studies have shown ST↑ in aVL during the acute phase of anterior acute MI to be highly predictive of a left anterior descending (LAD) artery occlusion proximal to the first diagonal branch. However, there was no significant difference in the occurrence of regional dysfunction of the lateral segments between patients with and without ST↑ in either lead I or aVL.

Usually patients with ST↑ in both the anterior and inferior leads have occlusion of a long LAD that wraps the cardiac apex. In contrast, proximal LAD occlusion is associated with ST↓ in the inferior leads. In contrast to the angiographic findings, in the present study there was no difference in regional dysfunction in the apical, inferior or posterior segments between patients with and without ST↑ in leads II, III, and aVF.

Previously we did not find an association between ST↑ in lead V1 and an LAD occlusion proximal to the first septal branch. However, in the present study, basal septal, basal anteroseptal and basal anterior regional dysfunction were seen more often in patients with ST↑ in lV1. Moreover, patients with ST↑ in V1 had worse global RWMA score, suggesting proximal LAD involvement. While ST↑ ³0.2 mV in V2 is associated with a trend towards worse global RWMA score, ST↑ in V2 was not associated with more basal RWMA, or septal involvement. Patients with ST↑ in V2 had more apical inferior regional dysfunction.

Lead V5 and V6 are thought to face the apical portion of the anterior or lateral aspects of the left ventricle. Hence, ST↑ in these leads during anterior acute MI is considered to indicate more extensive apical or lateral involvement. However, our findings do not support this belief. The significance of ST↑ in V5 and V6 remains to be elucidated.

These data suggests that the classical classification of the ECG subtypes of acute MI should be replaced by a new classification system based on correlation between ST deviation in the various leads and coronary anatomy and extent of infarction.

References

Golovchiner G, Matz I, Iakobishvili Z, Porter A, Strasberg B, Solodky A, Imbar S, Birnbaum, Y. Correlation between the electrocardiogram and regional wall motion abnormalities as detected by echocardiography in first inferior acute myocardial infarction. Cardiology. 98:81-91; 2002.

Porter A, Wyshelesky A, Strasberg B, Vaturi M, Solodky A, Shapira Y, Imbar S, Sagie A, Battler A, Birnbaum Y. Correlation between the electrocardiogram and regional wall motion abnormalities as detected by echocardiography in anterior acute myocardial infarction. Cardiology. 94:118-126; 2000.