Rapid ECG Review: High-Yield Cardiology Tracings for NEET PG Medicine

ECG Interpretation (Myocardial Infarction)

• ECG image with ST elevation in LEAD II, III, and aVF and reciprocal changes of ST depression in V1,2,3,4 indicating Inferior wall MI.
• In lead II:
  • P wave present, no Q wave
  • Characteristic ST elevation present - Tomb Stone Pattern (ST elevation is convex in an upward direction)
• In Inferior wall MI, the thrombus mainly presents in RCA

ECG Findings in MI (Myocardial Infarction)

Hyperacute T wave (Earliest ECG finding)

• Normal size criteria of T wave:
  • Vertical height is <5mm in limb leads & <10 mm in chest leads
• More than normal size of T wave - Hyperacute T wave
• Indicates Myocardial Ischemia.
• Develops within seconds of infarction

2. ST elevation

• Significant ST elevation:
  • For Male patients: The rise is ≥ 2mm
  • For female patients: The rise is ≥1.5mm
• Also called current of injury.
• Indicates Myocardial injury.
• Myocardial injury is best identified by cardiac biomarkers
• Develops within minutes of infarction

3. Q waves/ Pathological Q waves

• In a normal individual, the Q wave is within one small square
• Indicates Cell Death or Previous MI
• A deep Q wave persists for the whole life.
• Usually develops after >1hr of infarction

4. T wave Inversion

ST elevation is associated with a T wave inversion.

Tombstone Pattern/ Pardee sign ECG

• Tombstone pattern/ Pardee sign (Pardee waves refers to the symmetric inversion of T waves during an acute coronary syndrome or myocardial ischemia.)
• Significant ST elevation present in V2, V3, V4, V5,V6, Lead I, aVL and reciprocal change ST elevation is present in Lead III, aVR
• The above findings indicate: Extensive anterior wall MI
• High risk of developing Cardiogenic shock, Pulmonary edema, and Sudden cardiac death
• Sudden cardiac death: Death within 1 hour of being seen or heard. It could be Ventricular fibrillation or Pulseless Ventricular Tachycardia (PVT) and need defibrillation.

Sinus Arrhythmia ECG

Normal sinus rhythm with variable R-R interval that is not tachyarrhythmia is known as Sinus arrhythmia. Occurs as a result of vagal tone variation which is produced by the phases of respiration.

• ECG shows variable RR intervals like in the above figure.
• Here HR is varies from 100 to 75bpm (this is not tachyarrhythmia: HR>100bpm)
• P wave with QRS complex present - normal sinus rhythm.
• Normal sinus rhythm + Varying HR = Sinus arrhythmia.

Atrial Fibrillation ECG

• An ECG showing both increasing and decreasing variations of HR with an absence of a P wave and the presence of twitching indicates Atrial Fibrillation.
• Due to atrial twitching, clots develop in the Left Atrial
• Appendage is seen.
  • Blockage in the brain causes stroke
  • Blockage in the mesenteric arteries causes infarction of bowel with lower GI bleeding presenting as very severe abdominal pain, and if not identified will lead to gangrene of the intestine
• There is a variable R-R interval
• The pulse in AF is often described as irregularly irregular.
• Atrial Fibrillation is the most common sustained arrhythmia

Multi-Focal Atrial Tachycardia ECG

• Patient with COPD with recurrent episodes of palpitations and dizzy spells.
• P waves are present - variable morphology/height
  • ≥ 3 different varieties of P wave should be present
• Variable R-R interval (HR >100/min)
• Rx: DOC: Verapamil
• DC Shock is Contraindicated.

Atrial Flutter ECG

• Atrial flutter is a variant of Atrial fibrillation, only the site of heart involvement is different.
• Characteristic ECG finding: Saw Tooth Pattern.
• The macro re-entrant circuit around the cavotricuspid isthmus in the right side of the heart is responsible.
• Rx:
  • Rate control with esmolol
  • Anticoagulants
  • Ibutilide
  • If Ibutilide fails - Low-intensity DC shock with 25-50 J.

Paroxysmal Supraventricular Tachycardia ECG

• Based on the HR in lead 2, the ECG shows tachyarrhythmia.
• Constant R-R interval
• QRS is on the lower side of the normal
• Global ST depression is present - Evidence of sub-endocardial ischemia.
• Merged P and T wave - Hidden P wave
• Also known as AV nodal re-entrant tachycardia (AVNRT) i.e., the narrow QRS complex tachycardia

Wolf Parkinson White (WPW) Syndrome

ECG findings:

• There is change in the slope of the upswing of R wave - Delta waves.
  • Short PR interval because of fast conduction in the heart (PR interval is inversely related to HR)
  • ‘q' wave is absent - Since the current is not involving the AV nodal pathway and bundle of HIS
  • Change in the upswing of R wave - Delta waves
  • Broader RS complex:
    • Delta wave contributes to a broader RS complex
    • Intermyocyte conduction: The current travels through the myocytes (slower) instead of the Purkinje fibers (Fastest conducting fiber in the heart)
  • PJ interval remains normal
    • PJ= (↓) PR+ (↑) qRS
    • The amount of PR reduction is equal to the increase in the RS complex

Hypothermia ECG findings

• Prolonged PR interval - due to slowing of the heart in hypothermia.
• An inverted P wave might be present - due to AV node firing the atria retrogradely
• A deflection/notch in the downswing of R wave - Osborn wave
• Ideal site for checking core temperature: Pulmonary Artery (invasive)
• Preferred site for checking core temperature: Lower esophagus

Ventricular Tachycardia ECG findings

• HR ≃ 200 bpm
• Shortened R-R interval
• Broad qRS complex (Normal qRS complex is 2-2.5 small squares i.e., 80 to 100 milliseconds)
• Tachycardia with Broad qRS complex indicates VT
• All of the broad qRS complexes are monomorphic. Therefore, the given ECG shows Monomorphic VT
• Josephson Sign: A slight notch which is exclusively noted in VT

Hyperkalaemia ECG Findings

• HR >60 bpm.
• Tall-tented T waves are present (>10mm in chest leads, >5mm in limb leads).
• In hyperkalemia, ECG is not reliable. It is just supportive evidence.
• Serum electrolytes - more reliable
• Increased R-R interval - K+ slows the heart
• ST elevation is seen
• The amplitude of the P wave decreases and gradually disappears.
• PR interval increases and the broad QRS complex merges with T wave - the Sine wave pattern. Occurs just before diastolic arrest
• Hyperkalemia can lead to death by causing diastolic arrest (K+ slows the heart)

Bradyarrhythmias ECG Findings

• No. of squares between R-R interval increases
• P wave is not deciphered or it is inverted which indicates malfunctioning of the SA node
• Heart rate = 300/60 = 50bpm
• SA node is not functioning properly (SA node normally fire - 60-100 bpm)
• On exertion - heart will not be able to generate the required amount of cardiac output leading to a syncopal episode

Second-degree Heart Block

Mobitz I or Wenckebach phenomenon

• Increasing trend of the PR interval (starting from P to the starting of the Q wave, it is not till the R wave)
• There is a P wave but no qRS complex
• There is missed beat experienced by a person who feels their own pulse
• Subsequently, there is a reset in heart rhythm and a serial prolongation of the PR interval followed by a missed beat.
• There is slow conduction via the AV node

Mobitz II heart block

• The PR interval for 1st , 2nd and 3rd time is constant
• Then there is a P wave followed by a missed beat, then again rhythm is reset
• The PR interval that comes subsequently will be almost of the same size

Third-degree heart block/Stokes-Adam syndrome

• R-R interval here is increased
• Heart rate ˂ 40 bpm
• QRS complex is relatively broad
• There is an A:V dissociation: No. of R waves and P waves do not match
• People with Stokes Adam syndrome will have hampering with the quality of their life
• Dual chamber/dual lead pacemaker is used on a priority
• Patients could have 'a' wave in JVP or frog waves in the JVP
• There is no conduction via AV node

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