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ECG Analysis — Lakshmi Narayan, 50-year-old Male, 88 kg

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Patient Details

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Primary Diagnosis: Right Bundle Branch Block (RBBB)

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1. Rate & Rhythm

• Heart rate: 86 bpm — normal sinus rate
• Rhythm: Regular sinus rhythm — P waves are present and upright in lead II, with consistent PR intervals, confirming normal sinoatrial node origin
• PR interval: Normal (~160–180 ms)

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2. Key RBBB Features on This ECG

V1 — The Hallmark Lead

• RSR' pattern ("M-shape" or "rabbit ears") — the most diagnostic feature of RBBB
  • Initial small r wave (septal depolarization, intact)
  • S wave (normal LV activation)
  • Large R' wave (delayed, slow RV activation via cell-to-cell conduction through the septum)
• QRS is wide (≥ 120 ms / 3 small squares)
• Discordant T-wave inversion in V1–V3 (appropriate secondary repolarization change — not ischemic)

V4–V6 and Lateral Leads (I, aVL, V5, V6)

• Wide, slurred S waves — the terminal delayed depolarization of the RV creates a late negative deflection in the lateral leads
• This is the mirror image of the R' seen in V1

Lead I

• Broad, slurred S wave — characteristic lateral RBBB finding

Lead II (Rhythm strip)

• Clearly shows regular, widened QRS complexes with the characteristic terminal slurring

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3. Why RBBB Happens — Electrophysiology

1. The impulse travels from the SA node → AV node → Bundle of His → splits into left and right bundle branches simultaneously
2. Both ventricles depolarize at nearly the same time

• The right bundle branch is blocked or delayed
• The left ventricle activates normally via the left bundle
• The right ventricle is activated late, via slow cell-to-cell spread across the interventricular septum from left to right
• This delayed RV activation creates the wide terminal R' in V1 and wide terminal S waves in lateral leads
• QRS widens to ≥ 120 ms because total ventricular depolarization takes longer

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4. Axis

• Normal axis on this ECG — RBBB alone does not shift the axis
• If left axis deviation were present (as it appears borderline here), this would indicate bifascicular block (RBBB + Left Anterior Fascicular Block — a common combination)

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5. ST–T Changes

• T-wave inversion in V1–V3: This is appropriate (secondary) discordance — a normal consequence of abnormal depolarization, NOT a sign of ischemia
• Rule: In RBBB, T waves should be discordant (opposite direction) to the terminal QRS deflection. In V1–V3 the terminal deflection is positive (R'), so T-wave inversion is expected and normal

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6. QRS Width

• At 25 mm/sec paper speed, 1 small square = 40 ms
• The QRS complex here appears ≥ 3 small squares wide (≥ 120 ms) — confirming complete RBBB (vs. incomplete RBBB which is < 120 ms)

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Summary Table: RBBB Diagnostic Criteria

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Clinical Significance in This Patient

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Reference ECG for Comparison

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ECG Analysis — Mrs. Mandelbiu (approximate name)

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Computer-Reported Findings (as printed on the ECG)

Computer Interpretation (printed):

1. Sinus Tachycardia
2. Leftward Axis
3. Incomplete Right Bundle Branch Block
4. ST & T Abnormality — Consider:
5. High Lateral Ischemia OR Left Ventricular Strain
6. UNCONFIRMED REPORT

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Detailed ECG Interpretation

1. Sinus Tachycardia (HR: 103 bpm)

• Heart rate 103 bpm — just above the normal upper limit of 100 bpm → sinus tachycardia
• P waves are present and regular, originating from the SA node
• Each P wave is followed by a QRS complex → normal AV conduction
• PR interval: 148 ms — normal (normal 120–200 ms)
• This is not a primary arrhythmia; it is a secondary/reactive tachycardia — the underlying cause must be identified and treated

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2. Leftward Axis

• Axis: -18° (noted on ECG as "leftward axis")
• Normal axis is −30° to +90°; this is borderline left axis deviation
• May suggest left anterior fascicular block (LAFB), left ventricular hypertrophy, or inferior MI — must correlate clinically

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3. Incomplete Right Bundle Branch Block (iRBBB)

• QRS duration: 90 ms (normal < 120 ms) — this is why it is incomplete RBBB, not complete RBBB
• Incomplete RBBB criteria: QRS 100–119 ms with RSR' morphology in V1–V2
  • (In this ECG the machine reports 90 ms — at the lower boundary; this may represent an early/partial delay)
• The right bundle branch is partially blocked — the right ventricle is still activated via the bundle branch, but with a slight delay
• iRBBB alone is usually a benign variant, especially in young or middle-aged women; does not require treatment per se

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4. ST & T Abnormality — High Lateral Ischemia vs. LV Strain

What the ECG shows:

• ST depression and/or T-wave changes in the high lateral leads — leads I, aVL (V4–V5 region)
• "High lateral" refers to the territory supplied by the first diagonal branch of the Left Anterior Descending artery (LAD) or the circumflex artery (LCx)

Two possible explanations:

QTc: 451 ms

• Borderline prolonged (normal < 440 ms men, < 460 ms women)
• May reflect ischemia, electrolyte imbalance, or drug effect
• Needs monitoring — at risk for Torsades de Pointes if QTc worsens

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Summary of ECG Diagnosis

Sinus tachycardia at 103 bpm, incomplete RBBB, leftward axis, with ST–T abnormality in high lateral leads — suggestive of lateral ischemia (NSTEMI/ACS) vs. LV strain. Requires urgent clinical correlation.

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Treatment Approach

STEP 1 — Immediate Assessment (Emergency)

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STEP 2 — Investigations (Stat)

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STEP 3 — Medical Treatment

A. If ACS / NSTEMI confirmed (troponin positive or dynamic ECG changes):

Per Goldman-Cecil Medicine: "A polypill strategy with aspirin (100 mg daily), ramipril (2.5–10 mg daily), and atorvastatin (20–40 mg daily) is preferred for preventing recurrent myocardial ischemic events."

B. For Sinus Tachycardia:

• DO NOT treat the tachycardia directly without finding the cause
• If ACS-related → beta blocker (metoprolol) will treat both
• If fever → antipyretics; if anemia → transfusion; if anxiety → anxiolytics + reassurance
• If "Inappropriate Sinus Tachycardia" (after all causes excluded): Ivabradine (selective If-channel blocker) is first-line

C. For QTc Prolongation (451 ms):

• Correct electrolytes: target K⁺ > 4.0 mEq/L, Mg²⁺ > 2.0 mEq/L
• Avoid QT-prolonging drugs: erythromycin, antifungals, haloperidol, metronidazole
• Monitor QTc on serial ECGs

D. For LV Strain (if ischemia excluded, hypertension-related):

• Intensify antihypertensive therapy: ACE inhibitor ± calcium channel blocker (amlodipine)
• Target BP < 130/80 mmHg
• Echo to assess LVH and guide therapy

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STEP 4 — Invasive Strategy Decision (if NSTEMI confirmed)

• Recurrent ischemia despite medical therapy
• Elevated troponin
• New ST depression
• Hemodynamic instability
• Reduced EF < 40%

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STEP 5 — Long-Term Management

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Clinical Bottom Line

This ECG of Mrs. Mandelbiu shows sinus tachycardia (103 bpm), incomplete RBBB, left axis deviation, and high lateral ST–T abnormality — a combination that demands urgent evaluation for Acute Coronary Syndrome (NSTEMI). The most critical next step is serial troponin and 2D echo. If troponin is positive or symptoms are present (chest pain, dyspnea), initiate DAPT + anticoagulation + beta blocker + statin immediately and plan for coronary angiography.