science

Right bundle branch block

Right bundle branch block is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Right bundle branch block rather than just read about it. In short: A right bundle branch block (RBBB) is a heart block in the right bundle branch of the electrical conduction system. During a right bundle branch block, the right ventricle is not directly activated by impulses traveling through the right bundle branch.

Key takeaways

Right bundle branch block belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Right bundle branch block to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Right bundle branch block from memory before moving on to harder problems.

Reference excerpt

A right bundle branch block (RBBB) is a heart block in the right bundle branch of the electrical conduction system. During a right bundle branch block, the right ventricle is not directly activated by impulses traveling through the right bundle branch. However, the left bundle branch still normally activates the left ventricle. These impulses can then travel through the myocardium of the left ventricle to the right ventricle and depolarize the right ventricle this way. As conduction through the myocardium is slower than conduction through the bundle of His-Purkinje fibres, the QRS complex is seen to be widened. The QRS complex often shows an extra deflection that reflects the rapid depolarisation of the left ventricle, followed by the slower depolarisation of the right ventricle.

Incomplete right bundle branch block An incomplete right bundle branch block (IRBBB) is a conduction abnormality in the right bundle branch block. While a complete RBBB has a QRS duration of 120 ms or more, an incomplete RBBB has a wave duration between 100 and 120 ms. It has a relatively high prevalence, a study conducted on young Swiss military conscripts with a mean age of 19 years found a prevalence of 13.5%. It affects patients of all ages, more commonly males and athletes, however it is not always a benign finding. Therefore, if abnormalities are detected on the physical exam, further testing should be done to exclude heart disease. There is no consensus in the literature regarding criteria for diagnosis. However, according to the American Heart Association/American College of Cardiology Foundation/Heart Rhythm Society (AHA/ACCF/HRS) it is defined by the following finding in adults:

QRS wave duration between 100 and 120 ms. rsr, rsR, or rSR in leads V1 or V2. S wave of longer duration than R wave or greater than 40 ms in leads I and V6. Normal R wave peak time in both V5 and V6, but greater than 50 ms in V1. The first three criteria are needed for diagnosis. The fourth is needed when a pure dominant R waver is present on V1.

Causes Common causes include normal variation, changes in bundle branch structure - such as mechanical stretching, chest trauma, right ventricular hypertrophy or strain, congenital heart disease such as atrial septal defect, and ischemic heart disease. In addition, a right bundle branch block may also result from Brugada syndrome, Chagas disease, pulmonary embolism, rheumatic heart disease, myocarditis, cardiomyopathy, or hypertension. Causes for incomplete right bundle branch block (IRBBB) often involve exercise-induced right ventricular remodeling, increased right ventricular (RV) free wall thickness, especially in athletes due to prolonged endurance exercise.

Diagnosis

The criteria to diagnose a right bundle branch block on the electrocardiogram:

The heart rhythm must originate above the ventricles (i.e., sinoatrial node, atria or atrioventricular node) to activate the conduction system at the correct point. The QRS duration must be more than 100 ms (incomplete block) or more than 120 ms (complete block). There should be a terminal R wave in lead V1 (often called "R prime," and denoted by R, rR', rsR', rSR', or qR). There must be a prolonged S wave in leads I and V6 (sometimes referred to as a "slurred" S wave). The T wave should be deflected opposite the terminal deflection of the QRS complex. This is known as appropriate T wave discordance with bundle branch block. A concordant T wave may suggest ischemia or myocardial infarction.

Treatment The underlying condition may be treated by medications to control hypertension or diabetes, if they are the primary underlying cause. If coronary arteries are blocked, an invasive coronary angioplasty may relieve the impending RBBB.

Epidemiology Prevalence of RBBB increases with age due to changes in the heart's conduction system. It's estimated up to 11.3% of the population by the age of 80 have RBBB.

Gallery

See also Bundle branch block Intraventricular block Left bundle branch block

References

External links

Illustrations

Worked examples

Example 1 — a first encounter with Right bundle branch block

Start with the simplest possible case. Write down what Right bundle branch block claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Right bundle branch block before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Right bundle branch block ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Right bundle branch block

In research: Right bundle branch block appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Right bundle branch block in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Right bundle branch block is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cardiac arrhythmia, so understanding it makes those chapters shorter.
In everyday life: Look for Right bundle branch block outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Right bundle branch block in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Right bundle branch block means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Right bundle branch block out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Right bundle branch block in simple terms?

Why does Right bundle branch block matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Right bundle branch block?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Right bundle branch block.