|Year : 2019 | Volume
| Issue : 3 | Page : 105-109
Correlation between the diagnostic accuracy of the electrocardiogram and coronary angiography in localization of occluded artery in acute ST-elevation myocardial infarction: A single-center experience
Denny T Dyna1, Bino Benjamin2, Louis Francy1
1 Department of Medicine, Jubilee Mission Medical College, Thrissur, Kerala, India
2 Department of Cardiology, Jubilee Mission Medical College, Thrissur, Kerala, India
|Date of Web Publication||30-Sep-2019|
Dr. Bino Benjamin
Department of Cardiology, Jubilee Mission Medical College, Thrissur, Kerala
Source of Support: None, Conflict of Interest: None
Background: The electrocardiogram (ECG) remains the crucial tool in the diagnosis of acute ST-elevation myocardial infarction (STEMI) other than coronary angiography (CAG). However, the specificity of the ECG in culprit vessel localization is limited due to the individual variations in coronary anatomy as well as by the presence of preexisting coronary artery disease. The current observational study was designed to establish the correlation between the diagnostic accuracy of ECG with CAG to predict the culprit artery in STEMI.
Materials and Methods: A total of 140 consecutive STEMI (ST elevation of >2 mm in at least 2 contiguous leads) patients were enrolled over 1.5 years at a tertiary care center in India. Based on ECG criteria, evaluated by blinded observer, patients were categorized into anterior, inferior with or without right ventricular infarction, and posterior wall myocardial infarction. Each group was further divided based on the culprit artery.
Results: A total of 96 (68.6%) were males and 109 (77.9%) were 51–70 years. ECG showed perfect agreement (κ = 0.895, 0.882, and 0.853, respectively) with CAG in the diagnosis of proximal left anterior descending (LAD), proximal right coronary artery (RCA), and mid and distal RCA. It showed just fair agreement (κ = 0.348) with CAG in the diagnosis of distal LAD. Moreover, ECG showed perfect agreement (κ = 1) with CAG in the identification of both LAD proximal to D1 and distal to S1 and left circumflex artery.
Conclusion: In STEMI patients, the diagnostic accuracy of ECG exhibits good correlation and agreement with CAG to predict the culprit vessels except for distal LAD.
Keywords: Coronary angiogram, diagnostic accuracy, electrocardiogram, ST-elevation myocardial infarction
|How to cite this article:|
Dyna DT, Benjamin B, Francy L. Correlation between the diagnostic accuracy of the electrocardiogram and coronary angiography in localization of occluded artery in acute ST-elevation myocardial infarction: A single-center experience. Heart India 2019;7:105-9
|How to cite this URL:|
Dyna DT, Benjamin B, Francy L. Correlation between the diagnostic accuracy of the electrocardiogram and coronary angiography in localization of occluded artery in acute ST-elevation myocardial infarction: A single-center experience. Heart India [serial online] 2019 [cited 2019 Oct 22];7:105-9. Available from: http://www.heartindia.net/text.asp?2019/7/3/105/268168
| Introduction|| |
The coronary angiography (CAG) is used as the standard for the diagnosis of coronary artery disease (CAD). It is important in the conditions like ST-elevation myocardial infarction (STEMI) where the prompt diagnosis is required to activate the cardiac catheterization team to perform primary percutaneous coronary intervention. However, CAG is associated with rare complications such as contrast agent reactions or rarely death occurs in 0.10%–0.14% cases. Among the techniques available for the diagnosis of ischemic heart disease, the electrocardiogram (ECG) remains a crucial tool to diagnose acute STEMI. However, the specificity of the ECG in culprit vessel localization in STEMI is limited due to the individual variations in coronary anatomy as well as by the presence of preexisting CAD.
As ECG is noninvasive, relatively cheap, readily available, and reliable diagnostic tool, it is used as an initial investigation in almost all cardiac diseases. Along with the diagnosis of STEMI, ECG helps in the early identification of the culprit vessel before angiography, in risk stratification depending on the affected vessel, and further management depending on ST-segment depression or elevation., Further, it helps to determine microvascular perfusion in patients with thrombolysis in myocardial infarction Grade 3 flow, the early diagnosis of right ventricular (RV) infarct, and primary management and the identification of infarct territory size when CAG is inconclusive. ECG is the gold standard to identify the presence and location of acute myocardial infarction (MI).
Multiple studies showed that ECG with ST-segment depression in the inferior leads predicts a culprit lesion proximal to the origin of the first diagonal branch of the left anterior descending (LAD) artery with high diagnostic accuracy., Therefore, the objective of the current study was to reestablish the diagnostic accuracy of ECG compared with the reference standard CAG in patients with STEMI. To do so, the current study was designed to calculate the sensitivity, specificity, negative predictive value (NPV), positive predictive value (PPV), and diagnostic accuracy of ECG in the interpretation of culprit vessel in patients with STEMI.
| Materials and Methods|| |
Study design and population
This was an observational study carried out over 1½ year period at a tertiary care center in India. Among the admitted patients at our facility, we enrolled 140 consecutive patients who were diagnosed with STEMI, who was being taken for primary angioplasty. Patients with signs and symptoms of acute MI with ST segment elevation of >2 mm in at least 2 contiguous leads on ECG were included in the study. The patients with a history of previous MI or coronary artery bypass graft, left bundle branch block, preexcitation and paced rhythm, old infarct/subacute infarct, and left ventricular hypertrophy as determined by the Sokolow index were excluded. Written informed consent was obtained from the patients enrolled in the study. The study was approved by the Institutional Ethics Committee.
Patients were categorized into three groups based on ECG criteria: anterior wall MI, inferior wall MI, and posterior wall MI. Each group was further divided into subgroups based on the site of occlusion within the artery. The ECG criteria to identify the site of occlusion are mentioned in [Table 1].,,,,
The ECGs were analyzed by an independent observer who was blinded to the findings of CAG. The primary outcomes of the study were sensitivity, specificity, PPV, NPV, and diagnostic accuracy of ECG in localizing the culprit vessel as compared to CAG.
Sample size calculation
The sample size of 140 has been calculated by Aday and Cornelius formula: n = Z21− α/2 P (1 − P)/d2, where, n = sample size, Z21− α/2 = Confidence interval, P = estimated proportion, d = desired precision. Data on the number of patients with STEMI admitted in the center in the previous year were also considered.
The statistical analyses were performed using the SPSS statistical package. The categorical variables presented as counts and percentages. For comparison, the Chi-square test or the McNemar's test was used. P < 0.05 was considered statistically significant. For categorical data, the chance-corrected index of agreement (κ value) was interpreted as: perfect agreement (κ = 0.81–1.00); substantial agreement (κ = 0.61–0.80); moderate agreement (κ = 0.41–0.60); fair agreement (κ = 0.21–0.40); slight agreement (κ = 0.00–0.20); or poor agreement (κ< 0.00).
| Results|| |
The baseline characteristics of all 140 patients are listed in [Table 2]. Among them, 68.6% of patients were male and 77.9% were in the age range of 51–70 years. For majority of the patients, heart rate (60–100/min; 95.7% patients), systolic blood pressure (121–140; 78.6% patients), and diastolic blood pressure (71–90; 76.4% patients) were within the normal range. The frequencies of culprit vessels as predicted by CAG and ECG are presented in [Table 3].
|Table 3: Frequency of culprit vessels predicted by electrocardiogram and coronary angiogram|
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The diagnostic accuracy of ECG for proximal LAD was 95% (sensitivity 87.90%, specificity 100%, PPV 100%, and NPV 92.13%). ECG showed perfect agreement with CAG with a Kappa value of 0.895. However, ECG showed just a fair agreement (κ = 0.348) with CAG in the diagnosis of distal LAD. The diagnostic accuracy found was 95% with a sensitivity of 100%, specificity of 94.90%, PPV of 100%, and NPV of 22.20%. The value of kappa was 1 when the culprit lesion was in LAD proximal to D1 and distal to S1 and left circumflex (LCX) artery, showing perfect agreement between diagnostic accuracy of ECG and CAG. The respective diagnostic accuracy for the vessels was 100%, whereas sensitivity, specificity, PPV, NPV, and diagnostic accuracy for proximal right coronary artery (RCA) and mid and distal RCA were 88.60%, 97.90%, 95.10%, 94.9%, and 95% and 93.1%, 95.5%, 84.4%, 98.1%, and 95%, respectively. The respective Kappa values were 0.882 and 0.853 showing perfect agreement between the ECG and CAG [Table 4].
|Table 4: Culprit vessel by electrocardiogram versus culprit vessel by coronary angiogram|
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| Discussion|| |
The current population-based observational study, in a cohort of 140 patients with intermediate-risk STEMI, confirms that the ECG has good reliability and perfect agreement (K value is between 0.81 and 1.00) in the detection of all the culprit vessels (except distal LAD when k = 0.348) compared to CAG. Furthermore, ECG displayed significant diagnostic accuracy ranged from 95% to 100%. The diagnostic accuracy was 100% in the detection of LAD artery proximal to D1 and distal to S1 and LCX artery.
Among the enrolled patients, 68.6% STEMI patients were males and 77.9% were in the age range of 51–70 years. The clinical spectrum found in our study matches with another study from Kerala conducted by Misiriya et al., which reported that 79% were males suffering from STEMI with a mean age of 56 years at the major medical center in Kerala.
The diagnostic study conducted by Braat et al. reported that ST-segment elevation of >1 mm in lead V4R in patients with acute inferior MI has 100% sensitivity, 87% specificity, and 92% diagnostic accuracy in predicting an occlusion above the first right ventricle branch of RCA. The study has included 84 acute inferior wall MI patients within 10 h of symptoms onset and concluded that ECG can expedite the treatment procedure (thrombolysis or percutaneous coronary intervention) after the positive diagnosis of occluded artery in CAD patients.
Another study conducted by Hosseini et al. in 138 inferior STEMI patients retrospectively reviewed ECG and angiography films. They reported that in patients with ST-elevation at lead III ≥ than lead II showed 96% sensitivity, 45% specificity, 83% PPV, and 82% NPV in the prediction of RCA vessel. In acute RV infarction patients, sensitivity, specificity, PPV, NPV, and diagnostic accuracy of ST-elevation at lead V4R on ECG in the prediction of proximal RCA occlusion were found to be 100%, 68.2%, 66.7%, 100%, and 80.6%, respectively. In our study, sensitivity, specificity, PPV, NPV, and diagnostic accuracy for proximal RCA and mid and distal RCA were 88.60%, 97.90%, 95.10%, 94. 9%, and 95% (κ = 0.882) and 93.1%, 95.5%, 84.4%, 98.1%, and 95% (κ = 0.853), respectively, for ECG as compared to CAG. The results showed that the observation in our study is consistent with the previous reports and showed that ECG has good correlation with CAG in the diagnostic of RCA.
The results are further supported by previous multiple studies. Among them, the study conducted by Bayram and Atalay reported that the sensitivity, specificity, PPV, and NPV of the ECG in the prediction of RCA were 86%, 94%, 95%, and 56%, respectively, in inferior wall STEMI patients with ST-elevation in lead III was > ST elevation in lead II. Another study in totally occluded coronary artery with inferior wall MI reported that the PPV and NPV of ST elevation in lead III exceeding that of lead II in the prediction of proximal and mid-RCA was 97% and 77%, respectively. In addition, in the current study, the number of patients with RCA (n = 43) as the culprit artery is greater than LCX (n = 4). This finding was consistent with studies done by Zimetbaum et al., Hosseini et al., and Sohrabi et al. who concluded that RCA was much more likely than the LCX to contain the culprit lesion in inferior wall MI.
Engelen et al. conducted the study to evaluate the value of ECG in localizing the culprit vessel in patients with acute anterior MI. They reported that sensitivity, specificity, PPV, and P value in the prediction of distal LAD were 95%, 87%, 46%, and 0.022, respectively, for ST depression at aVL lead. The sensitivity, specificity, PPV, and P value in the prediction of LAD occlusion proximal to S1 were 95%, 86%, 70%, and 0.000, respectively, for ST-elevation at aVR lead. We got similar observations in the detection of LAD. In the current study, the sensitivity, specificity, PPV, NPV, and P value for the prediction of proximal LAD were 87.9%, 100%, 100%, 92.13%, and 0.016, respectively, and for distal LAD, it were 100%, 94.90%, 100%, 22.20%, and 0.016. The sensitivity, specificity, PPV, NPV, and P value for the detection of LAD artery proximal to D1 and distal to S1 were 100% and 1.
There could be several reasons for the poor correlation of the ECG with CAG in the identification of distal LAD in the current study. Among ECGs recorded in the acute stage, the one showing the most pronounced abnormalities was selected for the study. It is not sure whether our findings are still applicable when patients reach the catheterization laboratory late. In some of these cases, the thrombus in mid LAD could migrate distally or undergo spontaneous/partial thrombolysis by the time CAG is performed. Here, even though the culprit lesion is mid LAD, it would be wrongly categorized as distal LAD during CAG. In cases where mid and distal LAD is diseased, it is difficult to categorize the culprit lesion exactly. In some of these cases, even though the most critical lesion is in the distal LAD, it may get categorized as mid LAD, due to the involvement of the mid LAD also.
The diagnostic accuracy of ECG has its limitations. Moreover, ECG inadequately represents the posterior, lateral, and apical walls of the left ventricle. Since CAG is the contemporary reference standard, there is a need for further studies in large populations to extrapolate the findings of the study mechanistically.
| Conclusion|| |
The ECG is an easily available, noninvasive diagnostic tool for the acute coronary syndrome, particularly STEMI. Its diagnostic accuracy exhibits good correlation and agreement with CAG in the prediction of culprit vessels except when the culprit lesion is in the distal LAD. As ECG identifies the proximal occlusions of the coronary arteries precisely, it thereby helps in the early prognostication and triage in the management of patients with acute coronary syndromes in the emergency room.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4]