Electrocardiography Changes in Acute Coronary Syndrome
Yosep Sutandar,B.Med
The definition of acute coronary syndrome depends on the specific characteristics of each element of the triad of clinical presentation (including a history of coronary artery disease),electrocardiographic changes, and biochemical cardiac markers. Acute Coronary Syndrome is a clincal spectrum consist of Unstable Angina, Non-ST Elevation Myocardial Infarction(NSTEMI), and ST Elevation Myocardial Infarction. The main clinical finding of ACS is angina or chest pain. Early diagnosis of ACS without ST elevation is characterized on increases of Troponin, Cardiac Enzyme. If Troponin positively increases, the diagnosis is NSTEMI. And If negative, the diagnosis is unstable angina pectoris (UAP).
Electrocardiography Findings in Unstable Angina Pectoris and NSTEMI
In normal ECG, T wave would be positive in lead I, II, dan V3 until V6; and negative or inverted in lead aVR; variated in lead III, aVF, aVL, and V1; and rarely found in V2. In case of Ischemic, T wave will be inverted, symmetrical, and commonly temporary ( in symptomatic patient). In this case, myocardial injury hasn’t occur, based on assessment in CK-MB or Troponin normally contents. And the diagnosis is Unstable Angina Pectoris (UAP). Otherwise, if inverted T wave persistent, Troponin usually increases, and the diagnosis changes from UAP to NSTEMI. UAP and NSTEMI commonly cause by non-occlusive Thrombus, mild occlusion (Spontaneously Reperfused is possible), or Collateral Circulatory Compensated Occlusion.
Typical findings of Depressed ST more than 0.5 mm(0.05 mV) in two or more lead, or deep T wave inversion and symmetric. Morphology of Depressed ST is downsloping. Depressed ST in UAP and NSTEMI tend to be transient and dynamic.
Electrocardiography Findings in STEMI
When STEMI is occurring, morphologic changes in electrocardiography occurred with time:
- Hyperacute T wave. In the early period of STEMI, Prominent T wave can be found in ECG. The prominent T wave is similar to Hyperacute T wave, which is T wave whose in extremity lead more than 6 mm and precordial lead more than 10 mm. Hyperacute T wave is suggestively indicate STEMI has occurred and happened 30 minutes after onset of symptoms. In the other hand, Prominent T wave is not always specifically indicates for ischemia.
- Early elevation of ST Segment. If occlusion is occurred for long time and has significant degree of occlusion (90% of coronary lumen) prominent T wave could be followed by ST Segment Deviation. Elevation of ST Segment indicates an irreversible injury of myocardial muscle to death cell (can be measured by Troponin Bio Marker Assessment) and the location involved the epicardial layer. The diagnosis of STEMI is enforced if there are elevation of ST segment more than 0.1 mV (1mm) in extremity lead and more than 0.2 mV (2mm) in precordial lead in two or more in consistent lead.
- Typical Convex elevation of ST Segment
- Disappearing R wave, in the other part pathologic R wave occurring.Patologic Q Wave related to transmural infarction which accompanied by fibrosis of entire wall. In 75% patient,it occurred from hours to days.
- Inverted T Wave. After long period of STEMI and coronary reperfusion hasn’t been implemented, elevation of ST Segment is disappearing and turning back to isoelectric line. Along with it, Inverted T Wave is occurring. T Wave normally found after days, weeks, or months.
- ST Segment turns back to Normal. ST segment usually stable in 12 hours, then completely resolution after 72 hours. ST Segment elevation usually disappeared in 2 weeks in 95% Inferior Myocardial Infarction and 40% Anterior Myocardial Infarction. Elevated ST Segment persistently in 2 weeks related to higher morbidity. And if ST Segment elevation settles for months, ventricle aneurism might be occurred.
Location of Acute Coronary Syndrome
To determine the location of ischemia or myocardial infarction and the prediction of involved coronary artery, two or more leads are needed.
I Lateral | aVR | V1 Septal | V4 Anterior |
II Inferior | aVL Lateral | V2 Septal | V5 Lateral |
III Inferior | aVF Inferior | V3 Anterior | V6 Lateral |
