Table of ContentsView AllTable of ContentsTypes and SymptomsCausesSeriousnessDiagnosisTreatmentPreventionComplications
Table of ContentsView All
View All
Table of Contents
Types and Symptoms
Causes
Seriousness
Diagnosis
Treatment
Prevention
Complications
Heart block is a delay or disruption within the heart’s electrical conduction system that controls the rhythm and beats, causing the heart to beat slowly or skip beats. Several possible causes of heart block exist. It may stem from aging of the conduction system, a prior heart attack, heart surgery, medication, or an infection.
There are three main types of heart block, and depending on the type, symptoms and treatment vary. First-degree heart block is the mildest type and often requires no treatment. Third-degree heart block is potentially life-threatening, and most people need the placement of a pacemaker (a small electronic device placed underneath the skin to help the heart beat normally).
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Types and Their Symptoms
To best understand heart block, you must first understand what occurs when the heart beats with an intactelectrical system.
The heart is a muscle with two upper chambers (right and left atria) and two lower chambers (right and left ventricles). It normally beats between 60 and 100 beats per minute (bpm).
Heart block can result in aslow heart rate (less than 60 bpm), which is known asbradycardia.
During a heartbeat, an electrical impulse (signal) spreads through the heart, triggering the chambers to contract (push blood) or relax (fill with blood) in a coordinated manner.
There are three types of heart block, and symptoms depend on the type.
First-Degree Heart Block
First-degree heart block is technically not a block. Instead, the electrical impulse is delayed or slowed as it spreads from the atria to the ventricles via the AV node. This is the mildest type of heart block and usually causes no symptoms.
Second-Degree (Incomplete) Heart Block
Second-degree heart block occurs when some of the heart’s electrical impulses from the atria reach the ventricles, and some are entirely blocked.
Second-degree heart block can be further classified into the following:
Mobitz type 1 is generally considered a benign (harmless) form of second-degree heart block, although it can progress to a higher degree of heart block.
Symptoms are usually absent with Mobitz type 1.
Symptoms of Mobitz type 2 include:
Third-Degree (Complete) Heart Block
Third-degree heart block is the most severe type because it means that no electrical impulses reach the ventricles from the atria.
Because no impulses reach the ventricles, the heartbeat slows significantly or, most dangerously, becomes absent.
Symptoms of third-degree heart block are the same ones as those seen with second-degree Mobitz type 2, although they are more severe and potentially life-threatening.
Bundle Branch Block: Another Conduction DisorderUnlike the above heart blocks (which involve a delay or block via the AV node), abundle branch blockreflects a slowing of the heart’s electrical impulse through one of the ventricles, causing them to contract at slightly different times.The two types of bundle branch blocks are:Left bundle branch blockRight bundle branch block
Bundle Branch Block: Another Conduction Disorder
Unlike the above heart blocks (which involve a delay or block via the AV node), abundle branch blockreflects a slowing of the heart’s electrical impulse through one of the ventricles, causing them to contract at slightly different times.The two types of bundle branch blocks are:Left bundle branch blockRight bundle branch block
Unlike the above heart blocks (which involve a delay or block via the AV node), abundle branch blockreflects a slowing of the heart’s electrical impulse through one of the ventricles, causing them to contract at slightly different times.
The two types of bundle branch blocks are:
Common Causes and Risk Factors
Heart block has many possible causes.
Common causes include:
Medications
Examples of such medications include:
Normal Variant
In some individuals, first-degree heart block or Mobitz type 1 second-degree heart block are a normal variant, meaning there is no underlying health problem. This is typically seen in young athletes.
Risk Factors
Factors that increase a person’s chance of developing heart block include:
How Serious Is a Heart Block?
Heart block may not be serious and may not require treatment, as in most cases of first-degree block.
In contrast, in some instances, heart block can be serious, if not life-threatening. Specifically, chronic bradycardia may result in heart failure, and third-degree heart block can lead to sudden cardiac death.
The primary test for diagnosing heart block is anelectrocardiogram(ECG).An ECG is a tool for visualizing the electrical impulse traveling through the heart as it beats.
What Happens During an ECG?An ECG entails placing 12 electrodes on a person’s chest, arms, and legs. The electrodes are connected to a machine via wires. The machine records the heart’s electrical signals, translating them as a pattern of wavy, spiky lines on paper that a provider can read.
What Happens During an ECG?
An ECG entails placing 12 electrodes on a person’s chest, arms, and legs. The electrodes are connected to a machine via wires. The machine records the heart’s electrical signals, translating them as a pattern of wavy, spiky lines on paper that a provider can read.
The lines of an ECG reading consist of these three components:
Normally, the PR interval (the distance between the P and R waves) on the ECG paper is 200 milliseconds (or five small boxes).
ECG abnormalities seen with heart block include:
If the ECG shows a heart block, a focused medical history, physical exam, and various diagnostic tests help providers determine the underlying cause.
For instance, they may inquire about:
They will also listen to your heart and lungs with a stethoscope and check your heart rate.
The following tests may also be performed:
ReferralSome individuals with a heart block are referred to anelectrophysiologist—a cardiologist with special training in understanding the heart’s electrical activity. An electrophysiologist can perform a study to help find the precise location of the block, which helps guide the treatment plan.
Referral
Some individuals with a heart block are referred to anelectrophysiologist—a cardiologist with special training in understanding the heart’s electrical activity. An electrophysiologist can perform a study to help find the precise location of the block, which helps guide the treatment plan.
Treatment Options
The treatment of heart block depends primarily on the type and severity.
The treatment ofMobitz type 2 second-degree and third-degree blocksdepends on whether the person is hemodynamically unstable or stable.
PacemakerApacemakeris a device implanted underneath the skin near the heart muscle. It sends electrical impulses to the heart to prevent it from beating too slowly.
Pacemaker
Apacemakeris a device implanted underneath the skin near the heart muscle. It sends electrical impulses to the heart to prevent it from beating too slowly.
For all cases of heart block, healthcare providers will work to determine the underlying cause and reverse it, if possible (e.g., medication toxicity or electrolyte imbalance).
A permanent pacemaker is generally indicated in all symptomatic blocks, even if the cause is reversed. It’s also indicated in people with Mobitz type 2 second-degree heart block or third-degree block who do not have a reversible cause.
There is no surefire way to prevent heart block. However, certain lifestyle practices may help lower your chances of developing it.
For example, adopting heart-healthy habits can help prevent heart attacks. Such habits include:
Heart Healthy Foods: What to Eat and What to Avoid
Other proactive steps you can take to help prevent heart block include:
Complications and Treatment Side Effects
Potential complications or side effects of pacemaker placement include:
Can You Live Normally With a Heart Block?Most people with heart block live normal, full lives as long as they follow their healthcare provider’s care plan.If you have a pacemaker, you may have some restrictions, such as avoiding contact sports.
Can You Live Normally With a Heart Block?
Most people with heart block live normal, full lives as long as they follow their healthcare provider’s care plan.If you have a pacemaker, you may have some restrictions, such as avoiding contact sports.
Summary
Heart block causes the heart to beat slowly or skip beats due to a delay or block in the heart’s electrical system. Many possible causes of heart block exist, including a medication side effect, heart attack, infection of the heart’s lining or valves, or an electrolyte imbalance (e.g., high potassium in the bloodstream).
17 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Mitchell LB.Overview of heart block. InMerck Manual Consumer Version. Merck & Co., Inc. 2023.Sauer WH.Second-degree atrioventricular block: Mobitz type I (Wenckebach block). In: UpToDate, Link MS (Ed), Wolters Kluwer.Sauer WH.Second-degree atrioventricular heart block: Mobitz type II. In: UpToDate, Link MS (Ed), Wolters Kluwer.Sauer WH.Third-degree (complete) atrioventricular block. In: UpToDate, Link MS (Ed), Wolters KluwerNational Heart, Lung, and Blood Institute.Arrhythmias: conduction disorders.Kusumoto FM, Schoenfeld MH, Barrett C, et al.2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines, and the Heart Rhythm Society.J Am Coll Cardiol. 2019;74(7):932-987. doi:10.1016/j.jacc.2018.10.043National Organization for Rare Disorders.Congenital heart block.British Heart Foundation.Watch: What are beta blockers and what do they do in your body?Block ML, Basile J.Major side effects and safety of calcium channel blockers. In: UpToDate, Elliott WJ (Ed), Wolters Kluwer.Virgadamo S, Charnigo R, Darrat Y, Morales G, Elayi CS.Digoxin: a systematic review in atrial fibrillation, congestive heart failure and post myocardial infarction.World J Cardiol. 2015;7(11):808-16. doi:10.4330/wjc.v7.i11.808Mitchell LB.Atrioventricular block. InMerck Manual Professional Version. Merck & Co., Inc. 2023.Kerola T, Eranti A, Aro AL, et al.Risk factors associated with atrioventricular block.JAMA Netw Open. 2019;2(5):e194176. doi:10.1001/jamanetworkopen.2019.4176Cascino T, Shea MJ. (2023).Electrocardiography. InMerck Manual Consumer Version. Merck & Co., Inc.American Heart Association.Atherosclerosis.Clémenty N, Fernandes J, Carion PL, et al.Pacemaker complications and costs: a nationwide economic study.J Med Econ. 2019;22(11):1171-1178. doi:10.1080/13696998.2019.1652186MedlinePlus.Heart block.Johns Hopkins Medicine.Heart block.
17 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Mitchell LB.Overview of heart block. InMerck Manual Consumer Version. Merck & Co., Inc. 2023.Sauer WH.Second-degree atrioventricular block: Mobitz type I (Wenckebach block). In: UpToDate, Link MS (Ed), Wolters Kluwer.Sauer WH.Second-degree atrioventricular heart block: Mobitz type II. In: UpToDate, Link MS (Ed), Wolters Kluwer.Sauer WH.Third-degree (complete) atrioventricular block. In: UpToDate, Link MS (Ed), Wolters KluwerNational Heart, Lung, and Blood Institute.Arrhythmias: conduction disorders.Kusumoto FM, Schoenfeld MH, Barrett C, et al.2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines, and the Heart Rhythm Society.J Am Coll Cardiol. 2019;74(7):932-987. doi:10.1016/j.jacc.2018.10.043National Organization for Rare Disorders.Congenital heart block.British Heart Foundation.Watch: What are beta blockers and what do they do in your body?Block ML, Basile J.Major side effects and safety of calcium channel blockers. In: UpToDate, Elliott WJ (Ed), Wolters Kluwer.Virgadamo S, Charnigo R, Darrat Y, Morales G, Elayi CS.Digoxin: a systematic review in atrial fibrillation, congestive heart failure and post myocardial infarction.World J Cardiol. 2015;7(11):808-16. doi:10.4330/wjc.v7.i11.808Mitchell LB.Atrioventricular block. InMerck Manual Professional Version. Merck & Co., Inc. 2023.Kerola T, Eranti A, Aro AL, et al.Risk factors associated with atrioventricular block.JAMA Netw Open. 2019;2(5):e194176. doi:10.1001/jamanetworkopen.2019.4176Cascino T, Shea MJ. (2023).Electrocardiography. InMerck Manual Consumer Version. Merck & Co., Inc.American Heart Association.Atherosclerosis.Clémenty N, Fernandes J, Carion PL, et al.Pacemaker complications and costs: a nationwide economic study.J Med Econ. 2019;22(11):1171-1178. doi:10.1080/13696998.2019.1652186MedlinePlus.Heart block.Johns Hopkins Medicine.Heart block.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Mitchell LB.Overview of heart block. InMerck Manual Consumer Version. Merck & Co., Inc. 2023.Sauer WH.Second-degree atrioventricular block: Mobitz type I (Wenckebach block). In: UpToDate, Link MS (Ed), Wolters Kluwer.Sauer WH.Second-degree atrioventricular heart block: Mobitz type II. In: UpToDate, Link MS (Ed), Wolters Kluwer.Sauer WH.Third-degree (complete) atrioventricular block. In: UpToDate, Link MS (Ed), Wolters KluwerNational Heart, Lung, and Blood Institute.Arrhythmias: conduction disorders.Kusumoto FM, Schoenfeld MH, Barrett C, et al.2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines, and the Heart Rhythm Society.J Am Coll Cardiol. 2019;74(7):932-987. doi:10.1016/j.jacc.2018.10.043National Organization for Rare Disorders.Congenital heart block.British Heart Foundation.Watch: What are beta blockers and what do they do in your body?Block ML, Basile J.Major side effects and safety of calcium channel blockers. In: UpToDate, Elliott WJ (Ed), Wolters Kluwer.Virgadamo S, Charnigo R, Darrat Y, Morales G, Elayi CS.Digoxin: a systematic review in atrial fibrillation, congestive heart failure and post myocardial infarction.World J Cardiol. 2015;7(11):808-16. doi:10.4330/wjc.v7.i11.808Mitchell LB.Atrioventricular block. InMerck Manual Professional Version. Merck & Co., Inc. 2023.Kerola T, Eranti A, Aro AL, et al.Risk factors associated with atrioventricular block.JAMA Netw Open. 2019;2(5):e194176. doi:10.1001/jamanetworkopen.2019.4176Cascino T, Shea MJ. (2023).Electrocardiography. InMerck Manual Consumer Version. Merck & Co., Inc.American Heart Association.Atherosclerosis.Clémenty N, Fernandes J, Carion PL, et al.Pacemaker complications and costs: a nationwide economic study.J Med Econ. 2019;22(11):1171-1178. doi:10.1080/13696998.2019.1652186MedlinePlus.Heart block.Johns Hopkins Medicine.Heart block.
Mitchell LB.Overview of heart block. InMerck Manual Consumer Version. Merck & Co., Inc. 2023.
Sauer WH.Second-degree atrioventricular block: Mobitz type I (Wenckebach block). In: UpToDate, Link MS (Ed), Wolters Kluwer.
Sauer WH.Second-degree atrioventricular heart block: Mobitz type II. In: UpToDate, Link MS (Ed), Wolters Kluwer.
Sauer WH.Third-degree (complete) atrioventricular block. In: UpToDate, Link MS (Ed), Wolters Kluwer
National Heart, Lung, and Blood Institute.Arrhythmias: conduction disorders.
Kusumoto FM, Schoenfeld MH, Barrett C, et al.2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay: executive summary: a report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines, and the Heart Rhythm Society.J Am Coll Cardiol. 2019;74(7):932-987. doi:10.1016/j.jacc.2018.10.043
National Organization for Rare Disorders.Congenital heart block.
British Heart Foundation.Watch: What are beta blockers and what do they do in your body?
Block ML, Basile J.Major side effects and safety of calcium channel blockers. In: UpToDate, Elliott WJ (Ed), Wolters Kluwer.
Virgadamo S, Charnigo R, Darrat Y, Morales G, Elayi CS.Digoxin: a systematic review in atrial fibrillation, congestive heart failure and post myocardial infarction.World J Cardiol. 2015;7(11):808-16. doi:10.4330/wjc.v7.i11.808
Mitchell LB.Atrioventricular block. InMerck Manual Professional Version. Merck & Co., Inc. 2023.
Kerola T, Eranti A, Aro AL, et al.Risk factors associated with atrioventricular block.JAMA Netw Open. 2019;2(5):e194176. doi:10.1001/jamanetworkopen.2019.4176
Cascino T, Shea MJ. (2023).Electrocardiography. InMerck Manual Consumer Version. Merck & Co., Inc.
American Heart Association.Atherosclerosis.
Clémenty N, Fernandes J, Carion PL, et al.Pacemaker complications and costs: a nationwide economic study.J Med Econ. 2019;22(11):1171-1178. doi:10.1080/13696998.2019.1652186
MedlinePlus.Heart block.
Johns Hopkins Medicine.Heart block.
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