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ECG in acute coronary syndrome

Patients presenting acutely unwell secondary to compromised myocardial blood supply are said to be suffering from an acute coronary syndrome (ACS). Based on clinical findings, ECG abnormalities and blood test analysis, acute coronary syndromes can be divided into three categories: –

  1. ST elevation MI (STEMI)  correlates with complete vessel occlusion and
  2. NonST-elevation MI (NSTEMI)  correlate with partial vessel occlusion
  3. Unstable angina (UA)

Stemi sequence of ECG changes

When an atheromatous plaque ruptures in a coronary vessel, and the clot which forms completely obliterates the vascular lumen, the entire thickness of the myocardial wall supplied by that vessel becomes ischemic and is at risk of infarction. These events produce a series of changes on the ECG in the leads overlying the area of myocardium at risk of death.

Stemi ECG changes: Variable and modified by intervention

  • Hyperacute T waves-  (Onset) 2-5 minutes, (Resolution) Hours
  • ST elevation-  (Onset) 20-30 minutes,  (Resolution) Days to 2 weeks
  • Terminal QRS portion
  • Alterations-  (Onset) 30 minutes to hours, (Resolution) Hours
  • T wave inversion-  (Onset) Variable, (Resolution) Variable (usually weeks)
  • Pathological Q waves*-  (Onset) 9 to 24 hours, (Resolution) permanent
  • *Early Q waves which may be transient are an important and common variant.

 

Stemi localisation

In blockage of the right coronary artery (RCA), the inferior surface of the ventricles is infarcted, an inferior STEMI. 1B. The inferior leads are in the bottom right-hand corner of the ECG

In blockage of the left anterior descending artery (LAD) the septum and anterior surface of the ventricles is infarcted, an anterior STEMI. 2B. Four of the chest leads examine the septum (V1 and V2) and anterior surface of the ventricles (V3 and V4).

Incomplete blockage of the Left circumflex the lateral wall of the left ventricle is infarcted, a lateral STEMI. Leads I, aVL, V5and V6 examine this area of the heart.

 

Nstemi and unstable angina

The classical ECG abnormalities associated with ischaemia are depression of the ST segment below the isoelectric line (this is the most common finding) or inversion of T waves in leads with dominant R waves (loss of concordance).

On occasion, ischemia manifests as a combination of both ST depression and T wave inversion.

If an episode of ischemia resolves with no infarct developing, the patient is said to have suffered an episode of unstable angina. If an infarct develops it is termed a non-ST elevation MI (NSTEMI)

As the ECG changes of unstable angina and NSTEMI are identical the two entities cannot be distinguished based purely on the analysis of the ECG. You need a second test to separate the two. If the patient develops elevated levels of cardiac markers in the blood in association with the ECG changes we’ve described, they are said to have had a NSTEMI. If the blood levels remain normal they have had pure ischemia (unstable angina).

In marked contrast to STEMI, the distribution of the ECG changes among the leads correlates poorly with the vessel obstructed in NSTEMI.

The ecg in acute coronary syndrome (ACS)

Acute coronary syndrome (ACS)

Patients presenting acutely unwell secondary to compromised myocardial blood supply are said to be suffering from an acute coronary syndrome (ACS). Based on clinical findings, ECG abnormalities and blood test analysis, acute coronary syndromes can be divided into three categories

  1. ST elevation MI (STEMI)- correlates with complete vessel occlusion
  2. Non-ST-elevation MI (NSTEMI)- correlate with partial vessel occlusion
  3. Unstable angina (UA)

Stemi sequence of ECG changes

When an atheromatous plaque ruptures in a coronary vessel, and the clot which forms completely obliterates the vascular lumen, the entire thickness of the myocardial wall supplied by that vessel becomes ischemic and is at risk of infarction. These events produce a series of changes on the ECG in the leads overlying the area of myocardium at risk of death.

Stemi ECG changes: variable and modified by intervention

 

  • Hyperacute T waves- (Onset) 2-5 minutes, (Resolution) hours
  • ST elevation- (Onset) 20-30 minutes, (Resolution) days to 2 weeks
  • Terminal QRS portion
  • Alterations- (Onset) 30 minutes to hours, (Resolution) hours
  • T wave inversion: – (Onset) variable, (Resolution) variable (usually weeks)
  • Pathological Q waves*: – (Onset) 9 to 24 hours, (Resolution) permanent
  • *Early Q waves which may be transient are an important and common variant.

 

Stemi localisation

In blockage of the right coronary artery (RCA), the inferior surface of the ventricles is infarcted, an inferior STEMI. 1B. The inferior leads are in the bottom right-hand corner of the ECG

In blockage of the left anterior descending artery (LAD) the septum and anterior surface of the ventricles is infarcted, an anterior STEMI. 2B. Four of the chest leads examine the septum (V1 and V2) and anterior surface of the ventricles (V3 and V4).

Incomplete blockage of the Left circumflex the lateral wall of the left ventricle is infarcted, a lateral STEMI. Leads I, aVL, V5and V6 examine this area of the heart.

 

Nstemi and unstable angina

The classical ECG abnormalities associated with ischaemia are depression of the ST segment below the isoelectric line (this is the most common finding) or inversion of T waves in leads with dominant R waves (loss of concordance).

On occasion, ischemia manifests as a combination of both ST depression and T wave inversion.

If an episode of ischemia resolves with no infarct developing, the patient is said to have suffered an episode of unstable angina. If an infarct develops it is termed a non-ST elevation MI (NSTEMI)

As the ECG changes of unstable angina and NSTEMI are identical the two entities cannot be distinguished based purely on the analysis of the ECG. You need a second test to separate the two. If the patient develops elevated levels of cardiac markers in the blood in association with the ECG changes we’ve described, they are said to have had a NSTEMI. If the blood levels remain normal they have had pure ischemia (unstable angina).

In marked contrast to STEMI, the distribution of the ECG changes among the leads correlates poorly with the vessel obstructed in NSTEMI.

CategoryCardiology

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