Second-Degree Heart Block: Mobitz Type 1 Overview
Medically reviewed by Christopher Lee, MDMedically reviewed by Christopher Lee, MDThere are three degrees of heart block that are classified based on severity. With second-degree heart blocks, some signals from the atria (upper chambers of the heart) do not reach the vestibules (lower chambers).There are two subtypes of second-degree heart block: Mobitz type 1 (also called a Wenckebach block), which may or may not cause symptoms, and Mobitz type 2, which can cause problems pumping blood and irregular heartbeats.
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Quick 2nd-Degree Heart Block FactsHeart blocks are disruptions in the electrical signals that regulate and coordinate movements of the heart muscle as it pumps blood. They range from first-degree (mild) to third-degree (severe). In severe cases, electrical signals from the atria never reach the vestibules.Second-degree heart blocks partially disrupt the electrical signals. Healthcare providers categorize second-degree heart block subtypes—Mobitz type 1 and type 2—based on their physical signs on an electrocardiogram (ECG), which records the electrical activity of the heart using electrodes on the chest. Here's what providers look for:Mobitz type 1: Often, Mobitz type 1 does not cause noticeable symptoms. However, healthcare providers observe slower electrical signs on an ECG. They may recommend at-home pulse monitoring if you have an abnormally low pulse or experience other symptoms.Mobitz type 2: Type 2 second-degree heart block is more severe and causes irregular, slowed, or skipped heartbeats. This type impacts the heart's ability to supply the body with blood. Often, people with Mobitz type 2 need a pacemaker to ensure a normal heartbeat. Who Gets Diagnosed With 2nd-Degree Heart Block?A wide range of conditions and medications can raise the risk of second-degree heart block. These include:Congenital heart defects (present at birth)Cardiomyopathy (diseases that affect the heart muscles)Heart attack (myocardial infarction), when it damages the heart’s electrical systemHeart valve disease, which impacts the valves of the heartLyme disease, or other infectionsMaternal lupus (autoimmune disorder)Medication side effects, including certain beta-blockers, calcium channel blockers, digitalis, and othersSevere electrolyte abnormalities (hyponatremia)Thyroid disease (typically hypothyroidism)SymptomsThe symptoms of heart block depend on its severity. Whereas type 1 second-degree heart block doesn’t always cause symptoms, Mobitz type 2 is more likely to cause problems. Potential signs of second-degree heart block include:Chest pains, squeezing, or pressureDizziness, light-headedness, faintingFatigueHeart palpitations, a pounding, racing, or irregular heartbeatSome people experience asymptomatic and temporary first-degree heart block. It can arise in otherwise healthy young adults when they’re sleeping or at rest.
A Good PrognosisIt can be concerning to learn you have second-degree heart block. Untreated, this condition can lead to severe and even fatal complications. But the outlook is positive. Mobitz type 1 heart block is often benign, and with monitoring and medical treatment, most people can manage a type 2 heart block.Although pacemakers can limit some activities, they improve quality of life; with second-degree heart block, you can resume most normal activities.
How 2nd-Degree Heart Block Type 1 Looks on ECGSince second-degree heart block type 1 often doesn’t cause symptoms, healthcare providers usually only detect it on an ECG.On ECG, a regular heartbeat starts with a smaller, round P wave as electricity stimulates the atria. The P waves are followed by a period of no activity, or PR interval, before sharp waves of activity in the ventricles, or QRS waves.With Mobitz type 1 second-degree heart block, the PR intervals get longer, and QRS waves are delayed and then dropped, which happens cyclically and adopts a regular pattern. For instance, someone may have three P waves for every two QRS waves.Treatment and Pacemaker Surgery A cardiologist (heart specialist) will help you determine the best treatment for second-degree heart block. If you have no symptoms or are mild—as is often the case with type 1—you may not need a pacemaker to regulate your heartbeat. Most people with Mobitz type 1 do not require a pacemaker. Instead, a cardiologist may recommend:Changing medicationsKnowing warning symptomsLearning how to check your pulseRegular checkupsCardiologists consider pacemaker surgery in more severe, symptomatic cases of second-degree heart block. Pacemakers are small devices implanted under the skin near the chest or directly in the heart to regulate heart rhythm by transmitting electrical signals via wires and sensors connected to the atria and ventricles.Implanting a pacemaker is an appropriate treatment for cases that will not resolve on their own and run the risk of complications like heart arrhythmia, cardiac arrest, and heart failure.Management to Prevent 3rd-Degree Heart Block Progression If you have second-degree heart block, your cardiologist or healthcare provider may recommend making lifestyle changes to prevent it from worsening.Third-degree heart block is a medical emergency. It causes a complete disruption of electrical signals to the ventricles and can lead to severe complications.Steps to promote heart health and prevent complications include:Controlling cholesterolDietary changesImproving sleepLimiting or stopping alcoholManaging blood pressureManaging diabetesManaging stressManaging weightPhysical activityQuitting smokingOngoing Monitoring and Cardiologist Follow-Up If you have second-degree heart block, ongoing monitoring and follow-up are critical, even if you don’t have symptoms. Schedule regular follow-ups with a cardiologist. They will monitor your heart health and track any causes or complications of the condition. If you have a pacemaker, they will do regular maintenance checks.In addition, your provider may recommend tracking your pulse daily, showing you what to expect and what could mean trouble. Severe symptoms and signs of heart failure warrant calling your provider and getting emergency help. These include:Chest painsDifficulty breathing DizzinessFeeling faint, loss of consciousnessRacing, skipping, or irregular heartbeatSwelling in the legs, ankles, or feetWeaknessSummary Second-degree heart block occurs when electrical signals from the upper part of the heart are disrupted on their way to the lower part. Healthcare providers break it down into two types: Mobitz type 1 (Wenckebach heart block) and Mobitz type 2. Adopting heart-healthy lifestyle changes and managing risk factors, like diabetes or high blood pressure, help prevent second-degree heart block from getting worse. Read the original article on Verywell Health.
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