Chapters Archive – Page 18 of 22

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

Left bundle branch block (LBBB) Left bundle branch block (LBBB) results from anatomical or functional impairment of the left bundle branch (LBB), leading to a…

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

Intraventricular conduction delay (defect): constellations of bundle branch blocks and fascicular blocks (hemiblocks) This chapter discusses intraventricular conduction delays (defects), which are caused by functional or…

Management and treatment of AV block (atrioventricular blocks)

Management and treatment of AV blocks (AV-block 1, 2 & 3) Evaluation of patients with suspected AV blocks requires a thorough medical history (with emphasis on causes…

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)

Third-degree (complete) AV block: ECG criteria, clinical characteristics and management This chapter discusses third-degree AV block, which is synonymous with AV dissociation, complete AV block, AV block III…

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

Second-degree AV block: ECG criteria, clinical characteristics & management In this chapter, the focus will be on second-degree atrioventricular (AV) block. Before proceeding, it is…

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

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

First-degree AV block: ECG criteria, clinical characteristics & management This chapter discusses first-degree atrioventricular (AV) block, also referred to as 1st-degree AV block, AV block…

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

Atrioventricular block (AV block): definition, causes, diagnosis & management This article covers the fundamental principles of atrioventricular (AV) blocks, which are classified into three types:…

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

Non-ST Elevation Acute Coronary Syndromes (NSTE-ACS): Non-ST Elevation Myocardial Infarction (NSTEMI) and Unstable Angina (UA) The focus of this chapter is the diagnosis and management of…

Figure 1. The coronary arteries and their relation to the ECG leads. Localization of myocardial infarction / ischemia is done by using ECG changes to determine the affected area and subsequently the occluded coronary artery (culprit).

ECG localization of myocardial infarction / ischemia and coronary artery occlusion (culprit)

Using the ECG to localize myocardial infarction and the coronary occlusion Determining the localization of myocardial infarction and ischemia, as well as identifying the occluded coronary artery…

Figure 1. The component of the cardiac conduction system and the vascular supply. RCA = right coronary artery. LAD = Left anterior descending coronary artery. LCX = left circumflex coronary artery.

Supraventricular and intraventricular conduction defects in myocardial ischemia and infarction

Conduction defects caused by myocardial ischemia and infarction Bradycardia and conduction defects, such as bundle branch block, fascicular block and AV block, are common in…