Right and left bundle branch block: what does it mean on an ECG and is it dangerous?

Other names: Блокада ножки пучка Гиса, блокада правой ножки пучка Гиса, блокада левой ножки пучка Гиса, неполная блокада правой ножки, БПНПГ, БЛНПГ, блокада передней ветви левой ножки

Bundle branch block is a violation of the conduction of electrical impulses along the right or left branches of the conduction system, which distributes excitation to the ventricles of the heart. Because of this, one of the ventricles is excited late, which is clearly visible on the ECG. The blockade itself usually does not cause complaints and is often discovered by chance. Incomplete blockade of the right leg is often found in healthy people and is considered a normal variant. Complete blockade of the left leg, on the contrary, almost always indicates heart disease: hypertension, coronary artery disease, cardiomyopathy or aortic valve disease. A blockade that appears for the first time against the background of chest pain is especially dangerous - it can be a sign of a heart attack and requires immediate call 103. The prognosis depends on the underlying disease.

🧾 МКБ-10: I45.1, I44.7 🏥 Where it is treated: 8 Finding on ECGRight is often safeLeft - a reason to examine the heart

👨‍⚕️ Which doctor

Cardiologist, arrhythmologist

🔬 Diagnostics

ECG, echocardiography, Holter monitoring, stress tests and CT coronary angiography if indicated

💊 Treatment

Treatment of underlying heart disease; for heart failure - resynchronization therapy, for high-degree blockades - a pacemaker

📈 Prognosis

With an isolated right blockade - favorable; with the left it is determined by the condition of the heart

⚠️ At risk

Arterial hypertension, coronary heart disease, valve defects, cardiomyopathies, age

⏱ When to see a doctor

Planned; emergency - first-time blockade with chest pain

🚨 See a doctor urgently

With these signs do not wait for a scheduled appointment — the condition requires emergency care.

Боль или давление в груди, особенно дольше 15 минут — звоните 103
Обмороки и предобморочные состояния
Одышка в покое или при небольшой нагрузке
Резкие перебои, очень редкий пульс
Отёки ног, быстрая прибавка веса за несколько дней
Впервые выявленная блокада левой ножки у человека с факторами риска

What is a bundle of His and what types of blockades are there?

The electrical impulse from the atria passes through the atrioventricular node into the bundle of His, which divides into the right and left bundle branches. The right leg leads to the right ventricle, the left branch branches into anterior and posterior branches to the left ventricle. Due to this, both ventricles contract almost simultaneously. When one of the legs is blocked, the impulse bypasses the affected area along the muscle more slowly, and the contraction becomes asynchronous. On the ECG this is manifested by expansion and change in the shape of the ventricular complexes. The blockade can be complete or incomplete, permanent or transient.

Incomplete blockade of the right leg
Complete block of the right leg
Blockade of the anterior or posterior branch of the left leg
Complete blockade of the left leg
Two-bundle and three-bundle blockades
Transient blockades that occur with increased heart rate

Reasons

Incomplete and even complete blockade of the right leg can occur in healthy people, including children and athletes. It also occurs in diseases that overload the right side of the heart: pulmonary embolism, chronic lung diseases, atrial septal defect. Left leg block is rare in a healthy person. Its main causes are long-term arterial hypertension with myocardial hypertrophy, coronary heart disease and heart attack, dilated cardiomyopathy, aortic stenosis, and myocarditis. With age, the conduction system is gradually replaced by connective tissue, which also leads to blockages.

Variant of the norm - more often for incomplete right blockade
Arterial hypertension
Coronary heart disease, heart attack
Cardiomyopathies and myocarditis
Valve defects and congenital defects
Pulmonary embolism
Age-related fibrosis of the conduction system

Symptoms

The bundle branch block itself is not felt. Complaints, if any, are related to the heart disease that caused it: shortness of breath, fatigue, chest pain, swelling. With prolonged blockade of the left leg, asynchronous contraction of the ventricles can worsen the pumping function of the heart and worsen heart failure. The combination of several blockades sometimes turns into a complete transverse blockade, in which the pulse sharply decreases, dizziness and fainting occur. Therefore, with double-bundle blockades, observation by a cardiologist is important, even without complaints.

Most often occurs without symptoms
Shortness of breath and weakness in heart failure
Chest pain due to coronary artery disease
Dizziness and fainting as the blockade progresses
Swelling of the legs

Diagnostics

The diagnosis is made by ECG, where characteristic changes in the complexes are visible. It is important to compare it with previous cardiograms: a long-existing blockade is assessed differently than a blockade that appeared for the first time. Echocardiography is required to assess chamber size, wall thickness, valves and contractility. Holter monitoring detects transient conduction disturbances and pauses. With left leg block, a conventional stress ECG is not very informative, so stress echocardiography, perfusion methods, or CT coronary angiography are used to exclude coronary artery disease. A natriuretic peptide test helps to suspect heart failure.

ECG and comparison with previous recordings
Echocardiography
Holter ECG monitoring
Stress echocardiography or CT coronary angiography
NT-proBNP
Blood tests for electrolytes

Treatment and observation

Isolated blockade of the right leg in a person with a healthy heart does not require treatment; routine examinations are sufficient. With left leg block and other options, the main task is to treat the cause: control blood pressure, coronary artery disease, heart failure. With reduced contractility of the left ventricle and wide blockade of the left leg, cardiac resynchronization therapy using a special stimulator is effective. When transitioning to high-degree blockades with fainting, a pacemaker is implanted. There are no special tablets that eliminate the blockade itself.

Regular ECG monitoring
Blood pressure control
Treatment of coronary disease and heart failure
Resynchronization therapy according to indications
Pacemaker for high-degree blockades
Quitting smoking and controlling cholesterol

Services and prices for this diagnosis

Based on official price lists of Tashkent clinics. The exact cost is determined after examination.

🔬 Diagnostics

Консультация кардиолога + ЭКГ с расшифровкой ЭхоКГ — эхокардиография (УЗИ сердца)from 165 000 Суточное мониторирование сердечной деятельности (холтеровское)from 200 000 Натрийуретический пептид (NT-proBNP)

Frequently asked questions: Bundle branch block

Is incomplete right bundle branch block dangerous?+

Most often not. Incomplete blockade of the right leg is often found in healthy children, adolescents and athletes and is considered a normal variant. When first detected, the doctor usually prescribes an ultrasound of the heart to rule out congenital defects and overload of the right side. If the heart is healthy, routine monitoring is sufficient.

What is the danger of left bundle branch block?+

Left leg block usually indicates heart disease: hypertension, coronary artery disease, cardiomyopathy. In addition, it masks signs of infarction on the ECG and may impair left ventricular function. Therefore, when it is detected, an examination by a cardiologist is necessary, even if the person feels well.

Is it possible to play sports with a bundle branch block?+

With isolated right bundle branch block and normal echocardiography, restrictions are usually not necessary. When the left leg is blocked, the permissible loads are determined by the cardiologist after an examination, since much depends on the underlying heart disease.

Is there a cure for bundle branch block?+

There are no pills that eliminate the blockade itself. They treat the disease that caused it, and if necessary, use stimulants: resynchronization devices for heart failure or a pacemaker for high-degree blockades. Sometimes a transient blockade disappears after the cause is eliminated.

Can blockade occur during a heart attack?+

Yes. New blockade, especially of the left leg, in combination with chest pain may be a sign of an acute heart attack. In this case, you cannot wait: you need to call 103. This is why it is useful for people with a known block to keep a copy of the ECG for comparison.

The information on this page is for reference only and does not replace a doctor consultation. Only a qualified specialist can make a diagnosis and prescribe treatment after an in-person examination.