Ecg

Fundamentals of ECG interpretation

Part IDr. Anil Barkul

MD(MED) DTCD

E.C.G BASICS

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PART II

Electrocardiogram (ECG)

Provides representation of the electrical activity of the heart

Extremely important diagnostic tool for various cardiac dysfunctions

Used extensively in healthcare systems

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WILLIAM ENTHOVAN.

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Dr. Nagel developed the first telemetry unit for transmitting E.C.G.recordings via radio waves from the field to the hospital.

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ECG in heart disease

v1 v2v3

v4v5

v6

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Summary of events of cardiac cycle

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1111

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ECG Reported as:

1.Standardisation 9.QRS Complex

2.Voltage 10.QRS Duration

3.Rate 11.ST Segment

4.Rhythm 12.T Wave

5.Axis 13.QT Interval

6.Position 14.U Waves

7.P Waves 15. Conclusion

8.PR Interval

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Step - Rate

Method

Count the number of R waves for a six second interval and multiply by ten

3 sec 3 sec

6 sec

(can be used for regular & irregular)

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Step - Rate

Method :

Count the number of 5mm squares in R-R interval and divide into 300

300150

10075

6050

4337

3330 … slow

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Step 1 - Rate

RATE:

Tachycardia exists if the rate is greater than 100 beats/min.

Bradycardia exists if the rate is less than 60 beats/min.

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Step : Rhythm

RHYTHM:

Determine if the ventricular rhythm is regular or irregular (pattern to irreg.?)

R-R intervals should measure the same

P-P intervals should also measure the same

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STEP - Rhythm

IRREGULAR

REGULAR

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STEP - Rhythm Example

• Irregularly Irregular

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STEP 3 – Is the P Wave Normal?

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STEP 3 - Is the P Wave Normal ?

Normal P wave with no QRS complex

NormalSame Shape

Associated with a QRS Complex?

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STEP 4 –PR Interval/Relationship

Consistent PRI of <0.20 secs is normal, lengthened or variant

PRIs could indicate an AV block

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STEP 5 –QRS DURATION

• A narrow QRS complex (< 0.12), indicates the impulse has

followed the normal conduction pathway

• A widened QRS complex (> 0.12), may indicate the impulse was generated

somewhere in the ventricles

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STEP 6 – ST segment & T wave

• Ventricular repolarization characterized on ECG as ST

segment and T wave

• Changes in ST segment and T wave often seen in

ischemic heart disease

ST depression T wave inversion ST elevation

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Identifying ST segment changes30

Regional association with ECG

Area of infarction

Leads associated Vessels involved

Inferior Leads II, III, and aVF; ST elevations Right coronary artery, left circumflex

Posterior Leads V1, V2, V3 ST depression; large R wave

Proximal right coronary artery, left circumflex

Anterior Leads V1, V2, V3, V4; ST elevation Left anterior descending

Lateral Leads V1, AVL, V5, V6; ST elevation Left circumflex

Rightventricular

Elevations in leads II, III, aVF, andV1; elevation greater in III thanII; large R wave V4

Proximal right coronary artery

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ST elevation myocardial infarction (STEMI)

ST elevation 1 mm or more in 2 contiguous leads

ST elevation in II, III & aVF

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Evolving infarction:

ECG progression

A. Normal ECG prior to MI

B. Ischemia from coronary artery occlusion results in ST depression (not shown) and peaked T-waves

C. Infarction from ongoing ischemia results in marked ST elevation

D/E. Ongoing infarction with appearance of pathologic Q-waves and T-wave inversion

F. Fibrosis (months later) with persistent Q- waves, but normal ST segment and T- waves

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Sequence of changes seen during evolution of MI

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Clinical implications of ECG changes…

Peaked T waves◦Present only for 5-30

mins after onset of MI

◦Intervention at this stage may prevent infarction; improved outcomes than initiating therapy at later stages

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Clinical implications of ECG changes …

ST segment elevation◦Injury to myocardium ◦Patients with largest ST

deviation benefit most from fibrinolysis

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Clinical implications of ECG changes …

Pathological Q waves ◦May develop within 1-2 hrs of onset

of symptoms of acute MI, though often they take 12 hrs to appear

◦ If ST segment elevation and Q waves evident on ECG and chest pain is of recent onset, patient may benefit from thrombolysis or direct intervention

◦Absence of Q waves post fibrinolysis may serve as favorable prognostic indicator

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Clinical implications of ECG changes…

T wave inversion ◦Late sign of evolving MI; occurs in

3/4th patients with completed MI ◦May persist for months and

occasionally remains a permanent sign of infarction

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Clinical implications of ECG changes

Normalization of ST segment◦Last ECG change during MI; occurs when

transmural MI progresses to completed infarction

◦ST elevation with an inferior MI may take up to two weeks to resolve, may persist even longer with anterior MI and may persist indefinitely if left ventricular aneurysm develops

◦Role of reperfusion therapy limited

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Evolving ECG in STEMI

Middle-aged male presents to emergency medical service with chest pain; initial ECG demonstrates nonspecific abnormalities; within 15 minutes during transport, ECG demonstrates significant inferior ST segment elevation, consistent with inferior wall STEMI

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Inferior Wall STEMI

ST elevation in II, III & aVF

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Anterior Wall STEMI

ST elevation in V1-V5

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Anterolateral MI

This person’s MI involves both the anterior wall (V2-V4) and the lateral wall (V5-V6, I, and aVL)!

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Unstable angina/NSTEMI

ECG ST-segment depression or prominent T-wave inversion and/or positive biomarkers of necrosis in absence of ST-segment elevation and appropriate clinical setting (chest discomfort or anginal equivalent)

NSTEMI if elevated biomarkers present (Troponin T, Troponin I or Creatine Kinase- MB [CK-MB])

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UA vs. NSTEMI

T wave inversion in II, III, aVF, V1-V6

If biomarkers normal, Unstable angina

If biomarkers elevated, NSTEMI45

Angina

Patient complained of chest pain

A.ST depression

B.5 minutes later, after nitroglycerin, ST segments revert to normal with relief of angina

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Prinzmetal’s angina with transient ST elevationPatient with history ofexertional and restangina

A. Baseline resting ECG shows non-specific inferior ST-T changes

B. With chest pain, ST elevations in II, III, aVF and reciprocal ST depression in I and aVL

C. Return of ST segments to baseline after nitroglycerin

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Summary

ECG an essential adjunct to clinical history & physical examination in patients with chest pain

ECG adds considerable information for risk stratification and clinical decision support for treatment strategies in ACS

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ECG.exe

Ecg.exe

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Dr.Anil BarkulMD(Med.)DTCD

Consulting Physician,Beed

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