Which ecg change is indicative of myocardial injury

This leads to ST segment elevations in the leads which observe the ischemic area. For example, ST segment elevations in V3—V4 indicates ongoing transmural ischemia located in the anterior wall of the left ventricle. The more intensive the ischemia, the greater the ST segment elevation. Although ST-segment elevations are the hallmark of transmural ischemia, they are actually preceded by hyperacute T-waves.

These T-waves are symmetric, broad based and have high amplitude. They occur immediately within seconds following occlusion of the coronary artery.

It is believed that hyperacute T-waves are caused by increased concentrations of potassium along with changes in the repolarization in the ischemic area. Hyperacute T-waves have a short duration and they diminish within a few minutes, after which the ST segment becomes elevated. Since hyperacute T-waves are of very short duration and they arise the moment that the occlusion occurs, it is uncommon to spot these in clinical practice.

However, clinicians who regularly see patients with chest discomfort will certainly encounter hyperacute T-waves every now and then ischemia is a highly dynamic process and some patients will develop the complete occlusion while monitored.

Also note that high T-waves but not hyperacute may persist for a few hours following the occlusion. It should also be noted that ECG leads whose exploring electrode is angled approximately opposite to the leads showing ST-segment elevations may show ST segment depressions. This is simply because these leads record the same ST-vector, but from the opposite direction.

Such ST-segment depressions are referred to as reciprocal ST-segment depressions. The injury currents in subendocardial ischemia which manifests as NSTE-ACS redirects the ST-vector such that it becomes directed from the epicardium to the endocardium and the back Figure 4. This results in ST-segment depressions and T-wave inversions. However, the leads displaying these ECG changes are not necessarily indicative of the ischemic area. In other words, ST-segment depressions or T-wave inversions in leads V3—V4 do not indicate that the ischemia is located anteriorly.

It follows that ST-segment depressions and T-wave inversions cannot localize the ischemic area. T-wave Changes in Ischemia and Infarction.

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Conduction Defects. Overview of atrioventricular AV blocks. These include a horizontal ST segment that forms a sharp angle with the ascending limb of the T wave 6 and U wave inversion following an upright T wave. ST segment and T wave changes are often nonspecific and can occur in a variety of conditions, but they should be considered as possible indicators of ischemia in patients presenting with chest pain.

ECG changes of infarction include ST elevation indicating injury , Q waves indicating necrosis , and T-wave inversion indicating ischemia and evolution of the infarction.

These changes are called the indicative changes of infarction and occur in leads facing the damaged tissue. Reciprocal changes are the mirror image of the indicative changes and are often seen in leads recording from the opposite area of the heart. Reciprocal changes include taller-than-normal R waves mirror image of Q waves , ST depression mirror image of ST elevation , and tall T waves mirror image of T-wave inversion.

Table 2 shows the leads in which indicative and reciprocal changes are recorded with different types of MI. The earliest ECG changes that occur with acute coronary artery occlusion are tall, peaked, and often wide-based T waves.

The first ECG change seen clinically is usually ST segment elevation, which indicates myocardial injury in tissue underlying the electrodes. The presence of large R waves and ST depression in V 1 -V 3 indicates that the posterior wall is also involved in the infarct. Q waves are the indicative change of infarction necrosis. Many leads can record normal Q waves, which are less than 0.

Other conditions can also cause abnormal Q waves on the ECG, but in a patient with chest pain and ST elevation, Q waves are considered diagnostic of infarction. Q waves usually appear within 8 to 12 hours of ST elevation if the artery is not reperfused; however, some patients do not develop Q waves until days after the MI.

In addition to ST elevation, other ECG changes can indicate acute injury, including an ST segment that pulls up to the peak of the T wave with no obvious J point visible; tall, peaked T waves; and symmetrical T-wave inversion. Table 3 shows acute injury patterns. Some ECG changes can indicate either ischemia or injury eg, T-wave inversion , and most of the ECG changes that occur in ischemia and injury can also be seen in other conditions eg, electrolyte imbalances, other cardiac disease processes.

The ECG is not specific in diagnosing anything other than the rhythm, but it remains a useful diagnostic tool, especially in the patient presenting with ACS. A year-old woman with mild epigastric pain and nonradiating chest pressure, which she described as being 2 on a point scale 0, no pain; 10, worst possible pain , presented to the emergency department ED.

She had a history of hypertension and high cholesterol and was a smoker. Her medications included atenolol Tenormin , omeprazole Prilosec , premarin, and atorvastatin Lipitor. Figure 7 is her admission ECG. Do you see anything suspicious for myocardial ischemia, injury, or infarction on her ECG? She was sent home, where she continued to have pain for the next few hours. She returned to the ED when her pain worsened.

On readmission, her pain was 8 on a scale of and radiated to her jaw and left shoulder. Which artery is the culprit? What is her rhythm? Her cardiologist was notified and she was sent immediately to the cardiac catheter laboratory, where she was found to have a totally occluded right coronary artery RCA. She was started on heparin and Integrilin and received two stents to her RCA. Figure 9 is her ECG taken the morning after her stent insertion.

Her postprocedure recovery was uneventful and she was discharged 2 days later with clopidogrel Plavix , atorvastatin, metoprolol, and premarin prescribed. Suspicious MI refers to the clinical manifestations, myocardial enzymes and other tests and coronary CTA and other examinations suggest that the patient may have MI, which is evaluated by a professional cardiologist.

By analyzing the TWAC morphology of a lot of clinical data, it is found that the curve of normal people has less fluctuation, and the curve of patients with MI is mostly jagged changes in different cardiac cycles. It shows that the T-wave area curve has a significant correlation with ischemic heart disease. Figure 2. Figure 3. Experiment results are shown in Table 2. Table 2.

The method used in this study to interpret the degree of coronary stenosis was physician visual assessment PVA , which is based on the personal experience of the surgeon. Judgment is relatively subjective.

Studies have pointed out that the severity of stenosis of coronary lesions in PVA in China is significantly higher than quantitative coronary angiography QCA and there is a large difference between hospitals and doctors Zhang et al. Therefore, the presence of false-negative patients does not rule out the possibility of overestimation of coronary artery disease caused by PVA.

Single-vessel disease is more common in false-negative patients, while multiple-vessel disease is more common in true-positive patients. The range of MI caused by single vessel disease is relatively small, and negative results are easily obtained.

In addition, collateral circulation is another factor of false negative results. The collateral circulation rate of patients in the false negative group is higher than that in the true positive group. Collateral circulation can improve the heart blood supply and may make TWAC negative. A total of 21 false-positive patients was included in this study, 15 of whom had chest tightness and chest pain.

Although coronary angiography showed negative results, the possibility of MI could not be completely ruled out. The data indicate that MI is still possible without significant coronary stenosis Tonino et al. The clinical manifestations of all these false positive patients were typical CHD and showed a higher incidence of coronary atherosclerosis than the true negative group.

T wave can reflect the heterogeneity of ventricular repolarization in patients and predict cardiovascular disease to a certain extent. T wave is a potential wave formed by repolarization of ventricular cells. Repolarization is an active energy-consuming process.

When MI occurs, the heart cannot normally deliver blood and nutrients. Therefore, insufficient supply of myocardial energy will cause myocardial contraction and diastolic function is impaired, which may cause T wave changes in patients with ischemic cardiomyopathy. Studies have shown that the degree of T wave changes in aVL leads reflects the degree of ventricular muscle excitement recovery time, and reflects the heterogeneity of ventricular muscle repolarization.

Compared with ST-T changes, aVL lead T-wave changes have a higher sensitivity for the diagnosis of myocardial ischemia, which is significantly related to the number of coronary artery disease vessels and the degree of myocardial ischemic injury Tepetam et al. It can be speculated that if the adjacent area of the left anterior descending branch ischemia, the T wave of lead aVL should also change.

Therefore, the T wave change of lead aVL also corresponds to the anterior descending branch of the left anterior descending coronary artery. As shown in Figure 3B , the aVR lead curve fluctuates in a zigzag manner, and the coordinate points in some cardiac cycles exceed the abscissa and become positive values. Studies have shown that the morphological changes of the T wave in lead aVR are of great significance in predicting cardiovascular death, and its value is higher than other ECG leads, comparable to the changes in the ST segment of the aVR lead Tan et al.

If the amplitude of the inverted T wave becomes smaller, it means that the risk of cardiovascular death is gradually increased.

When the inverted T wave becomes upright, the risk of cardiovascular death is higher. The aVR lead has been used only to judge the origin of the heart rhythm, and its role has been seriously underestimated. The aVR lead has a special position on the frontal six-axis system, that is, the aVR lead axis is between the I and II lead axes, the angle between the aVR lead axis and the ventricular depolarization vector is the smallest, and the projection is the largest, which is the most sensitive lead to the changes of the ventricular depolarization vector.

Coronary atherosclerosis causes a series of electrophysiological changes that affect ventricular repolarization Downar et al. During cardiac ischemia, the duration of action potential and conduction velocity decrease, leading to a heterogeneous repolarization process Janse et al. Studies have shown that ischemia increases the repolarization dispersion between normal and ischemic fibers, and between the epicardium and the endocardium Coronel et al.

The repolarization pattern has a continuous fluctuation Arini et al. This fluctuation refers to the change in the amplitude of the T wave or the change in the ST segment between different cardiac cycles. The amplitude of these bipolar alternations dispersions is usually in the microvolt range and cannot be visually recognized. Computer-based signal processing and analysis technology can detect subtle ECG changes. TWA represents the alternation of cardiac repolarization, is an indicator of ventricular tachycardia and ventricular fibrillation in ischemic myocardium, and can be used as an indicator of risk stratification of acute myocardial infarction.

The disadvantage of TWA is that it is susceptible to breathing, electrode and skin interference, wire movement and body position changes, and further research is needed. TWAC analyzes subtle ECG signal changes and amplifies such subtle changes to detect abnormal dynamics of cardiac repolarization, and is robust to acquisition noise, baseline drift and T wave morphology. TWAC is the T-wave area curve of 12 leads with the cardiac cycle.

Different leads of the electrocardiogram record electrical signals at different positions of the heart. Therefore, the degree of fluctuation of TWAC on different leads reflects the degree of stenosis at specific blood vessels to a certain extent. This paper analyzed the TWAC and coronary angiography results of some patients, and found that the T wave changes on leads V 3 ,V 4 , aVL corresponded to the obstruction of the left anterior descending branch of the coronary artery, and the T wave changes on the aVR lead predicted the stenosis at left trunk coronary arteries.

There are some limitations in this study. First, coronary angiography shows that coronary artery stenosis is not equivalent to MI Tonino et al. It cannot be ruled out that coronary angiography could not determine the myocardial ischemia relatively accurately. It has been confirmed by extensive randomized controlled studies that FFR is the gold standard for evaluating the physiological significance of coronary artery stenosis.

Changes in hemodynamic factors such as contractile force. Secondly, the sample size is small, and more clinical research is needed to further verify the TWAC method. Preliminary test results show that the proposed method has good sensitivity, specificity, and accuracy for MI detection, especially for the CHD patients with no obvious ECG changes.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation. The studies involving human participants were reviewed and approved by the Zhejiang Second Hospital Review Board.

RL and XZ contributed to the algorithm and the statistical analysis. JZ and RD contributed to the clinical data collection and interpretation.

All authors contributed to the writing, critical reading, and approval of the manuscript.