Chapters Archive – Page 18 of 22 – The Cardiovascular

Figure 2. Two ECGs showing left and right ventricular hypertrophy.

Biventricular hypertrophy ECG and clinical characteristics

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Atrial and ventricular enlargement: hypertrophy and dilatation on ECG

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Figure 1. These ECGs show the difference between normal conduction, left bundle branch block (LBBB) and right bundle branch block (RBBB). As evident from these ECGs, the cardinal difference between normal conduction and bundle branch blocks is the QRS duration: bundle branch blocks are caused by dysfunctional bundle branches, which results in slow (and abnormal) activation of ventricular myocardium and thus prolonged QRS duration. A QRS duration of 120 ms (0.12 s) is required to diagnose bundle branch block. Also note that both left bundle branch block (LBBB) and right bundle branch block (RBBB) cause marked ST-T changes, including ST elevations, ST depressions and inverted (negative) T-waves. These ST-T changes are due to abnormal repolarization and they are expected to occur in both LBBB and RBBB. Finally, note that there are marked difference in the ECG pattern between LBBB and RBBB. These ECGs are printed at paperspeed 50 mm/s.

Left bundle branch block (LBBB): ECG criteria, causes, management

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Figure 1. Components of the ventricular conduction system and the temporal association between the ECG and impulse transmission through the heart. An intranventricular conduction delay may occur whenever any of the main components of the conduction system is dysfunctional.

Intraventricular conduction delay: bundle branch blocks & fascicular blocks

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Management of AV blocks (treatment)

Management and treatment of AV block (atrioventricular blocks)

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Figure 1. Third-degree AV block (complete heart block, AV dissociation).

Third-degree AV block (3rd degree AV block, AV block 3, AV block III)

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Figure 1. Second-degree AV block Mobitz type 1, also known as Wenckebach block.

Second-degree AV block: Mobitz type 1 (Wenckebach) & Mobitz type 2 block

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Figure 1. ECG in first-degree AV block. Both conventional paper speeds are shown.

First-degree AV block (AV block I, AV block 1)

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Figure 1. Components of the ventricular conduction system and the temporal association between the ECG waveforms and impulse transmission through the heart. Atrioventricular (AV) blocks occur due to dysfunction in the conduction system.

Overview of atrioventricular (AV) blocks

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NSTEMI (Non-ST Elevation Myocardial Infarction) & Unstable Angina: Diagnosis, Criteria, ECG, Management

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