What is right bundle branch block in ECG?
Right bundle branch block (RBBB) is due to an anatomical or functional dysfunction in the right bundle branch, such that the electrical impulse is blocked. Refer to Figure 1 for an overview of the components of the ventricular conduction system, including the right bundle branch. In the setting of RBBB, depolarization (i.e activation) of the right ventricle will depend on electrical impulses spreading from the left ventricle. However, the electrical impulse that spreads from the left ventricle (to the right ventricle) will spread slowly because it travels partly or entirely outside of the conduction system. The slow spread of the impulse will result in a slow (and abnormal) activation of the right ventricle, which yields a bizarre and prolonged QRS complex on ECG. The hallmark of right bundle branch block is QRS duration ≥0,12 seconds, large R’-wave in V1/V2 and a broad and deep S-wave in V5/V6. Figure 2 illustrates a normal ECG, a right bundle branch block (RBBB) and a left bundle branch block (LBBB). Show
ECG criteria for right bundle branch block (RBBB)
If the QRS duration is ≥0,110 seconds but <0,12 seconds, the right bundle branch block is said to be incomplete. Note that a second r-wave (r’) may occur as a normal variant in lead V1 (the normal variant has normal QRS duration). Moreover, the normal septal q-waves (seen in V5, V6) are not affected by right bundle branch block. Occasionally the right bundle branch block only displays a broad and notched R-wave in V1 (instead of two R-waves); in that scenario the R-wave peak time should be >0.05 seconds. Electrophysiology of right bundle branch block (RBBB)Under normal circumstances both ventricles are depolarized simultaneously, but the ECG is dominated totally by electrical vectors generated by the left ventricle, because its muscle mass is substantially larger than the right ventricle. However, in right bundle branch block, the right ventricle is depolarized after the left ventricle, and therefore its electrical vectors may come to expression. The right ventricles electrical vector appears on the later part of the QRS complex, in the form of R’-wave (the vector yielding R’ is directed anteriorly and rightward). Because depolarization of the right ventricle is abnormal, repolarization will also be abnormal. Such repolarization abnormalities are termed secondary ST-T changes. This manifests on the ECG as discordant ST-T segments, meaning that the ST-T segment is directed oppositely to the QRS complex. As shown in Figure 1, the positive QRS complex in V1 is followed by negative ST-T segment with ST-segment depression and T-wave inversion. Similar changes are typically seen in V2. Right bundle branch block does not alter the electrical axis of the heart. Axis deviation indicates that there is concomitant fascicular block. Left axis deviation suggests concomitant left anterior fascicular block. Right axis deviation suggests concomitant left posterior fascicular block. Clinical significance of right bundle branch block (RBBB)Right bundle branch block in asymptomatic individuals is not correlated with adverse outcomes. On the other hand, new right bundle branch block in patients with chest pain may indicate occlusion in the left anterior descending artery. Finally, new right bundle branch block in patients experiencing dyspnea (particularly if acute) may indicate pulmonary embolism. In the vast majority of cases, however, right bundle branch block is a benign finding with little if any impact of cardiovascular prognosis. Young individuals rarely display right bundle branch block. However, incomplete right bundle branch block occurs occasionally even in younger persons. A large prospective cohort study evaluated the association between right bundle branch block and mortality over a period of 20 years in otherwise healthy individuals; no association was found. Causes of right bundle branch block (RBBB)
Diagnosis of ischemia and infarction in the setting of RBBBRight bundle branch block does not interfere with diagnosis of ischemia/infarction. It is possible to diagnose pathological Q-waves (because the initial part of the QRS is not affected by the RBBB). Acute ischemia (ST-T changes) may also be judged as usual, despite the bundle branch block. Note that acute cor pulmonale with RBBB may cause large Q-waves in V1–V3, II, III and/or aVF. Next chapterLeft bundle branch block (LBBB): ECG, criteria, causes & management Overview of Intraventricular Conduction Defects Left bundle branch block (LBBB in acute myocardial infarction (AMI) and acute coronary syndromes (ACS) Fascicular block (hemiblock): left posterior fascicular block (LPFB) and left anterior fascicular block (LAFB) Nonspecific intraventricular conduction delay View all chapters in Supraventricular and Intraventricular Conduction Defects Is a right bundle branch block serious?How serious is a right bundle branch block? If you have no symptoms and no heart disease, a right bundle branch block is not serious. But if you've already had heart failure or a heart attack along with right bundle branch block, it puts you at a higher risk of death.
What does a right bundle branch block indicate?Right bundle branch block (RBB) is an electrocardiogram finding resulting in a widened QRS and electrocardiographic vector changes. Although usually benign, this finding can represent underlying myocardial disease and is a predictor of mortality in certain patient populations.
What is the treatment for a right bundle branch block?If you have bundle branch block with low heart-pumping function, you may need cardiac resynchronization therapy (biventricular pacing). This treatment is similar to having a pacemaker implanted. But you'll have a third wire connected to the left side of your heart so the device can keep both sides in proper rhythm.
Is a right bundle branch block normal?Right bundle branch block is a normal finding in adults of all ages. Many individuals with RBBB have no evidence of structural heart disease and isolated RBBB occurs more commonly than isolated left bundle branch block (LBBB).
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