Chamber Enlargement Flashcards
What are the bounds of a normal P-wave axis?
+30° to +75°
Describe P-wave axis deviation in the presence of left or right atrial enlargement.
RAE may result in a P-wave axis >75° while LAE may result in a P-wave axis <30°
Note that P-wave axis deviation is neither sensitive nor specific for atrial enlargement, especially LAE, and should never be used in isolation to identify atrial enlargement.
The P-wave axis is generally most aligned with lead _______, making it the first choice of lead to look for atrial pathologies.
Lead II
Give indicators for right atrial enlargement
- Peaked P-wave morphology with amplitude >2.5mm in lead II (“P-pulmonale”)
- Due to enlargement of p-wave component attributable to Right atrial depolarization. Since R. atrium depolarizes first, this phenomenon increases overlap and leads to peaked morphology
- Prominent positive defleciton of P-wave in V1 (area under curve >1 small box)
- Potential P-wave axis >75°
Give indicators for left atrial enlargement
- Increased P-wave duration (>120ms)
- Notched P-wave appearance in lead II
- More prominent negative deflection of P in V1 (area under curve >1 small box)
Describe typical P-wave morphology in leads II and V1
- II: typically uniphasic, upright, with the largest amplitude of any lead, duration <120ms.
- V1: typically biphasic and isoelectric/equiphasic
Describe typical QRS morphology in V1 and V6
- V1: small inital r followed by dominant S wave
- r due to septal depolarization followed by S due to dominant L. ventricular depolarization away from V1
- V6: small initial q (septal/physiologic q) followed by dominant R
- q due to septal depolarization followed by dominant L. ventricular depolarization in direction of V6
Describe qualitative changes to QRS morphology in V1 and V6 in right ventricular hypertrophy
- V1: Shift to dominant R wave with small or absent s
- potential appearance of initial q and T-wave inversion
- V6: shift to equiphasic or S-dominant appearance
In summary, RVH leads to a reversal of normal QRS morphology in V1 and V6
Describe qualitative changes to QRS morphology in V1 and V6 in left ventricular hypertrophy
- V1: Deep, broad S-wave with potential loss of initial r
- V6: Tall, broad R-wave with potential loss of septal q.
- Potential T-wave inversion with downsloping ST depression
LVH leads to exageration of normal QRS morphology
Describe ECG changes due to secondary repolarization abnormalities in ventricular hypertrophy.
T-wave inversion and downsloping ST-depression in leads over the affected ventricle
Assess the following ECG for signs of chamber enlargement:
- Normal P-wave morphology in II and V1 (subtle pre-pathologic peaking in II suggestive of early RAE)
- Dominant R in V1 with downsloping ST-depression and T-wave inversion
- Equiphasic or dominant S in V6
- Right axis deviation
- Suggests RVH
The term “ventricular strain pattern” is no longer encouraged, and is instead referred to as __________
secondary repolarization abnormalities
Describe intrinsicoid deflection and how it can be used in assessing for ventricular hypertrophy
- intrinsicoid deflection is the duration from the initial QRS deflection to peak of the first R-wave
- Prolonged intrisicoid deflection is indicative of ventricular hypertrophy
- >35ms in RVH
- >45ms in LVH
Describe qualitative ECG findings in RVH
- Unusually tall R waves in V1 and V2 ± secondary repolarization abnormalities (downward sloping STD with T wave inversions)
- Unusually deep S in V5, V6, I, and aVL
- Right axis deviation (>+90°)
- Right atrial enlargement
- RBBB may be present
- Poor R-wave progression
Describe qualitative ECG findings in LVH
- Unusually tall R waves in V5, V6, I, and aVL ± secondary repolarization abnormalities (downward sloping STD with T wave inversions)
- Unusually deep S in V1 and V2
- Left axis deviation (< -30°)
- Left atrial enlargement
- LBBB may be present
- Delayed intrinsicoid deflection
Describe features of chamber enlargement seen in this ECG
- Multiple signs of LVH
- LAD (QRS axis ~ -60°)
- Sokolow-Lyon voltage criteria (SV1 + RV5 >> 35mm)
- Secondary repolarization abnormalities in V5, V6, I, and aVL
- Intrinsicoid deflection in V5 and V6 >0.050ms
Describe features of chamber enlargement seen in this ECG
- Multiple signs of RVH
- RAD (QRS axis ~ +150°)
- Prominent RV1 and SV6
- Secondary repolarization abnormalities in V1-V4
