CONTENTS

• rsr' in V1: clinical approach
  • [1] WPW
  • [2] RBBB
  • [3] High lead placement
  • [4] Brugada-II, sodium channel blocker, hyperkalemia
  • [5] Pectus excavatum
  • [6] Athlete
  • [7] ARVC
  • [8] Pulmonary hypertension (PE or RVH)
  • [9] iRBBB (incomplete RBBB)
  • [10] Normal variant rsr'

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approach to rsr' in V1

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[#1/10] is there WPW? 📖

• Short PR interval.
• Delta-wave.

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[#2/10] is there RBBB? 📖

• [1] QRS >120 ms.
• [2] V1 and/or V2 has one of the following:
  • [a] rsr', rsR' or rSR'. The R' or r' is usually wider than the initial R-wave. 
  • [b] Wide R-wave, which is often notched (>50 ms to peak, with normal R peak time in V5-V6)
    • This includes a qR pattern. qR in V1 suggests RBBB plus either anterior Q-wave MI or severe RVH. (19281930)
• [3] Prolonged terminal S-wave in I and V6, either:
  • S duration > R duration, or
  • S duration > 40 ms.

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[#3/10] is there high placement of V1/V2?

• ⚠️ Suspect high lead placement if two or more of the following are present: (19242281)
• [1] V1 has an entirely negative P-wave (this may occur with LAA, but in LAA, it would often be accompanied by a broad P-wave in lead II).
• [2] V2 has a negative or biphasic P-wave (it should be purely positive).
• [3] QRS in aVR looks similar to V1 (and sometimes V2).
• [4] Poor R-wave progression.
• [5] Morphologic abnormalities may include:
  • RSR' in V1 and/or V2:
    • If seen, an Rsr' pattern supports that this is a false incomplete RBBB (generally, the right bunny ear should be taller).
    • There should be an absence of prominent/blunted S-waves in leads I and V6 (arguing against a global alteration in right ventricular depolarization).
  • STE, often in a saddleback configuration. (22938933) 
  • TWI in V2 (TWI may be normal in V1, but generally not in V2). However, persistent juvenile TWI may TWI in V2. 📖
  • Q wave in V2 can mimic an old septal MI.
  • Prominent R-wave in V1 (less common).

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[#4/10] Brugada, hyperkalemia, Na channel blockers 

hyperkalemia 📖

• 🔑  Peaked T-waves.
• 🔑  P-waves widen, PR increases, and eventually, P-waves disappear.
• 🔑  Bradycardia, blocks, and/or pauses.
• 🔑  QRS widening (may mimic RBBB or VT; can be >200 ms).
• 🔑  Infarct mimic (STE in V1-V2; often triangular STE diving into TWI).
• 🔑 Terminal right axis deviation (large S-I +/- S-V6; RSR' in V1).

sodium channel blockers 📖

• It often causes a tall R wave in aVR.

Brugada II pattern 📖

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[#5/10] pectus excavatum

• V1:
  • RsR' with fast inscription (sharp r').
  • P-wave is generally negative.
  • ST segment may have mild STE with a descending slope.
  • T-wave is usually negative or plus/minus.
• V6
  • No mismatch in QRS duration.
• 💡 Shares similarities with high placement of leads V1/V2.

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[#6/10] athlete 

rsr' pattern in athletes: 

• V1 shows
  • rsr' that is peaked and sharp.
  • No STE or minimal STE (<1 mm).
  • T-wave is negative and sometimes deep.
• Significance: seen in 35-50% of athletes. This may relate to physiological RV enlargement.

other common ECG changes in athletes may include:

• High vagal tone:
  • Sinus bradycardia.
  • First-degree AV block.
  • Mobitz I block during rest.
• High voltage R-waves in the precordium (without other criteria for LVH).
• Early repolarization.
• Isolated PVCs.

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[#7/10] is there ARVC (arrhythmogenic right ventricular cardiomyopathy)?

ECG findings in ARVC

• RV conduction delays, such as:
  • Slurred S wave in V1-V3 (~10%).
  • Incomplete or complete RBBB (~30%).
• Epsilon wave (~20% sensitivity, high specificity):
  • Low-amplitude wave usually best seen in right precordial leads.
  • Key finding: you may see a slight separation between the QRS complex and the epsilon wave.
  • This usually implies severe ARVC.
  • Ddx may include cardiac sarcoidosis, acute MI, and Brugada syndrome. (29272363)
• TWI seen in V1-V3 (up to 80% of patients). (29272363)
  • TWI can extend further and sometimes involve the inferior leads. (de Luna 2022)
  • TWI may progress gradually over time, correlating with RV volume. (29272363)
• Arrhythmias
  • VT may be sustained or nonsustained:
    • Usually, VT shows LBBB morphology with left QRS axis deviation (positive in aVL). Multiple different morphologies may occur in a patient.
    • VT may resemble RV outflow tract VT.
  • Some patients may have very frequent PVCs.
• Other features that may be seen:
  • Early repolarization is often seen.
  • QRS fragmentation may occur.

clinical significance of ARVC

• Usually transmitted in an autosomal dominant fashion.
• Clinical presentation may involve tachyarrhythmias or right-sided heart failure. (Griffin 2022)
• Echocardiography may reveal a localized RV aneurysm or RV failure. Cardiac MRI has higher sensitivity.
• Treatment:
  • Amiodarone has some demonstrated efficacy in ARVC.
  • Long-term therapy generally involves an ICD, sometimes additionally with radiofrequency ablation.

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[#8/10] is there pulmonary hypertension (PE or RVH)? 📖

features that may support PE/RVH:

• RAA (right atrial abnormality).
• Tall R' wave in V1.
• Prominent S-wave in leads I +/- V6.
• RV strain pattern in right precordial leads.

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[#9/10] incomplete RBBB (iRBBB)

⚠️ The term iRBBB is used very flexibly in the literature, and there is no universal consensus about how to define it.

ECG findings in iRBBB

• Rough diagnostic criteria: (21138928)
  • [1] Top normal QRS duration:
    • ~110-120 ms. (21138928)
    • 90-120 ms. (O'Keefe 2021)
  • [2] V1 or V2 has: rsr, rsR, or rSR.
  • [3] Leads I and V6 with S wave of greater duration than R wave, or >40 ms.
  • [4] Normal R peak time in leads V5-V6, but greater than 50 ms in lead V1. (19281930)
• Other features:
  • Reduced S-wave depth in V1-V2. (34100724)
  • Slurring of the downstroke or upstroke of the S-wave. (34100724)
• ⚠️ No features of RVH/PE (listed in the section above).

clinical significance of incomplete RBBB:

• Given the various definitions of iRBBB, the clinical significance is unclear.
• iRBBB is not uncommon, and it may be a benign finding.
• iRBBB can progress to complete RBBB.
• iRBBB is a risk factor for early-onset, lone atrial fibrillation. (21138928)
• iRBBB has been associated with pulmonary embolism and facioscapulohumeral muscular dystrophy. (34100724)

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[#10/10] normal variant rsr'

• ECG features may include:
  • V1 with rsr' or rSr' pattern.
  • QRS duration often <100 ms.
  • S-wave is extremely sharp, without slurring.
  • r-wave amplitude is <7 mm.
  • r' amplitude is smaller than either r or S waves.
• Results from delayed activation of the basal part of the right ventricle
• This is seen in ~2% of the population (men > women, often younger).
• Not a precursor of RBBB.

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questions & discussion

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