Difference Between Mobitz 1 and Mobitz 2

Difference Between Mobitz 1 and Mobitz 2: Mobitz 1 and Mobitz 2 are the two primary types of second-degree heart block. The Atria and ventricles of the heart may have abnormally delayed or even blocked impulse conduction. According to the severity of the blocks, these conditions are classified as Atrioventricular Blocks. An electrocardiogram (ECG) can be used to diagnose AV blocks of the first, second, and third degrees. The length of the PR interval in an ECG is prolonged by a delay in the conduction of impulses into the ventricles through the AV node. Some action potentials decline away without continuing to the ventricles when there is a PR interval with a duration of 0.25 to 0.45 seconds. In such cases, there will be a P wave without a QRS-T wave in its wake. A Second-Degree Heart Block is the medical term used for this situation.

Difference Between Mobitz 1 and Mobitz 2

Characteristics	MOBITZ 1	MOBITZ 2
Definition	A form of second-degree AV block known as Mobitz 1, refers to an irregular heartbeat (arrhythmia) where the length of the PR interval gradually lengthens until an impulse is totally blocked before reaching the ventricles.	A form of second-degree AV block known as Mobitz type II refers to an abnormal cardiac rhythm where the length of the PR interval is prolonged and the duration is constant, and occasionally an impulse is lost before reaching its target.
Heart Block	There is little chance of developing a total heart block.	The chances of developing a total heart block are high.
Causes	Medications such as digoxin, beta-adrenergic blockers, calcium-channel blockers, and amiodarone, as well as increased parasympathetic activation of the nervous system, can all result in a reversible conduction block that causes Mobitz type I block.	People without underlying structural cardiac problems hardly ever have Mobitz type II block. The most frequent causes are myocardial infarction or a heart attack, and conditions that affect the heart muscle walls, like cardiomyopathies.
Symptoms	Most patients continue to have no symptoms.	Compared to those who have Mobitz 1, people with Mobitz 2 are more likely to experience symptoms. Syncope and dizziness are the typical symptoms
Treatment	A temporary or permanent cardiac pacemaker may be implanted to help people with persistent symptoms.	A permanent pacemaker is necessary for the treatment of Mobitz type II block.
Prognosis	Mobitz 1 is a benign rhythm that commonly indicates an AV node obstruction and has favorable progress.	Mobitz 2 has a worse prognosis since it frequently manifests a block after the AV node, either at the bundle of His or its branches, and is more likely to progress to a third-degree block.

What is Mobitz 1?

A form of second-degree AV block known as Mobitz 1, refers to an irregular heartbeat (arrhythmia) where the length of the PR interval gradually lengthens until an impulse is totally blocked before reaching the ventricles. Wenckebach Block or Type 1 Second Degree Heart Block are other names for Mobitz 1. All three terms can be used interchangeably to refer to the same ECG rhythm.

Causes

Medications that slow nodal conduction, such as digoxin, beta-adrenergic blockers, calcium-channel blockers, and amiodarone, as well as increased parasympathetic activation of the nervous system (increased vagal tone), which is frequently observed in healthy athletes, can all result in a reversible conduction block that causes Mobitz type I block. A heart attack, heart muscle wall disorders (cardiomyopathies), myocarditis (inflammation of the heart muscle), endocarditis (infection of the inner layer of the heart), inherited heart defects, infiltrative and autoimmune disorders, and cardiac surgery are additional causes of Mobitz type I block.

Signs and Symptoms

Mobitz type I block typically doesn’t cause any symptoms in the people who are affected. When exercising, some people may occasionally experience lightheadedness, vertigo, or exhaustion. Rarely, Mobitz type I block may result in syncope, a transient loss of consciousness caused by a temporary reduction in the brain’s oxygen supply.

Diagnosis

During a regular ECG, Mobitz type I block is frequently discovered accidentally. An in-depth examination of the PR interval on the ECG strip is necessary to make the diagnosis of Mobitz type I block. The sinus node in Mobitz I is functioning normally and fires when it should, resulting in regular P wave occurrence. However, as atrial impulses pass through the AV node, they become more difficult to conduct with each passing impulse. This causes the PR interval to gradually lengthen until one impulse is entirely blocked. As a result, QRS complexes are occasionally dropped, which can cause bradycardia with more P waves than QRS complexes on the ECG.

Management

Mobitz 1 can be treated by the following:

• The first step in treating Mobitz type I is to address any potential reversible reasons for nodal blocks, such as stopping any drugs that can inhibit nodal conduction and addressing any electrolyte imbalances, such as hyperkalemia. Electrolyte imbalances can be treated with particular drugs or intravenous (IV) fluid administration.
• When possible, treatment for AV block, which is a result of another heart problem can include addressing the specific cause.
• Some symptomatic people may also benefit from treatment with drugs like atropine that momentarily enhance AV node conductivity.
• A temporary or permanent cardiac pacemaker may be implanted to help people with persistent symptoms or those who are at high risk of developing an advanced heart block.

What is Mobitz 2?

A form of second-degree AV block known as Mobitz type II refers to an abnormal cardiac rhythm where the length of the PR interval is prolonged and the duration is constant, and occasionally an impulse is lost before reaching its target. Mobitz type II can be recognized on an ECG by the occurrence of irregular, non-conducted P waves without gradual lengthening of the PR interval. Compared to people with Mobitz type I, those with Mobitz type II typically have more frequent and severe symptoms.

Causes

People without underlying structural cardiac problems hardly ever have Mobitz type II block. The most frequent causes are myocardial infarction or a heart attack, and conditions that affect the heart muscle walls, like cardiomyopathies. Less frequent causes include myocarditis, an infection of the heart’s inner layer, endocarditis, infiltrative and autoimmune diseases like hemochromatosis and amyloidosis, inflammatory diseases like rheumatic fever and Lyme disease, as well as cardiac surgery like mitral valve replacement. The nodal block is typically attributed to progressive cardiac conduction system damage brought on by fibrosis, or scarring, of the heart tissue when no particular cause can be determined.

Signs and Symptoms

Fatigue, dyspnea, and chest discomfort are among the symptoms of Mobitz type II block, however, the severity varies from person to person. These symptoms are linked to decreased cardiac output. Multiple impulses can be stopped at once, which can significantly lower cardiac output and cause bradycardia, hypotension, and hemodynamic instability. People may have a quick and unexpected onset of hemodynamic instability, which increases the chance of syncope or an unexpected cardiac arrest.

Diagnosis

ECG results are used to diagnose Mobitz 2 block. Similar to Mobitz type I, Mobitz type II causes blocked atrial impulses. The main distinction between the two is that, in Mobitz I, the PR interval gradually lengthens prior to a block, whereas in Mobitz II, P waves are blocked quite haphazardly and are not preceded by a lengthening of the PR interval. In contrast, the PR interval in conducted beats is constant and P waves seem to advance steadily. It is common to see a ratio, such as a 2:1 or 3:1 Mobitz II AV block, between the total number of beats that are performed and those that are not.

Management

Treatment of Mobitz 2 includes:

• When treating Mobitz type II, the first step is to address any potentially reversible causes of nodal blocks, such as stopping any drugs that might slow nodal conduction (such as digoxin, beta-blockers, calcium-channel blockers, and amiodarone) and correcting any electrolyte imbalances, such as hyperkalemia.
• When possible, treatment for AV block that results from another heart problem may also target the precise underlying cause.
• A permanent pacemaker, which is a device that continuously monitors a person’s heart rhythm and, if it detects a delay, sends an electrical signal into the ventricles to cause them to contract, is ultimately necessary for the treatment of Mobitz type II block.

FAQs on Mobitz 1 and Mobitz 2

Q1: What is second-degree heart block?

Answer:

The length of the PR interval in an ECG is prolonged by a delay in the conduction of impulses into the ventricles through the AV node. In such cases, there will be a P wave without a QRS-T wave in its wake. This situation is termed as Second-Degree Heart Block.

Q2: What is Wenckebach Block?

Answer:

A form of second-degree AV block known as Mobitz 1, refers to an irregular heartbeat (arrhythmia) where the length of the PR interval gradually lengthens until an impulse is totally blocked before reaching the ventricles. Wenckebach Block is the other name for Mobitz 1.

Q3: How ECG results are different in the case of Mobitz 1 and 2?

Answer:

The main distinction between the two is that, in Mobitz I, the PR interval gradually lengthens prior to a block, whereas in Mobitz II, P waves are blocked quite haphazardly and are not preceded by a lengthening of the PR interval.

Q4: What are the symptoms of Mobitz 1 block?

Answer:

Mobitz type I block typically doesn’t cause any symptoms in the people who are affected. When exercising, some people may occasionally experience lightheadedness, vertigo, or exhaustion.