Mobitz type II atrioventricular block

Mobitz type II atrioventricular block is a specific type of heart rhythm disorder that affects the electrical conduction system of your heart. In a healthy heart, electrical signals travel from the upper chambers (atria) to the lower chambers (ventricles) through a pathway called the atrioventricular (AV) node. This coordinated electrical activity ensures that your heart beats in a regular, effective rhythm. With Mobitz type II AV block, there is an intermittent interruption in this electrical pathway. Sometimes the electrical signal passes through normally, but occasionally it gets completely blocked, preventing the ventricles from receiving the signal to contract. This creates an irregular heartbeat pattern where some expected heartbeats are "dropped" or missing. Unlike other types of AV blocks, the timing between the atria and ventricles remains constant when the signal does get through, but the blocked beats occur without warning. This condition is considered more serious than other types of second-degree AV blocks because it can unpredictably progress to complete heart block, where no electrical signals reach the ventricles. Understanding your condition is the first step in managing it effectively with your healthcare team.

Many people with Mobitz type II AV block may not experience noticeable symptoms initially, especially if the blocked beats occur infrequently. However, as the condition progresses or if more beats become blocked, symptoms typically develop and can significantly impact daily life. The most common symptoms include feeling dizzy or lightheaded, particularly when standing up or during physical activity. You may experience episodes of feeling faint or actually fainting (syncope), which occurs because your brain isn't receiving enough oxygen-rich blood due to the irregular heartbeat. Many people also report feeling unusually tired or weak, even during routine activities that previously didn't cause fatigue. Some individuals notice their heart beating irregularly or feel like their heart is "skipping beats." You might experience chest discomfort, shortness of breath, or difficulty exercising at your usual level. These symptoms can be intermittent and may vary in intensity depending on how frequently the electrical blocks occur. It's important to seek immediate medical attention if you experience fainting episodes, severe dizziness, chest pain, or significant shortness of breath, as these could indicate that your condition is worsening or that you're at risk for more serious complications.

Mobitz type II AV block can result from various factors that damage or interfere with the heart's electrical conduction system. The most common cause is coronary artery disease, where blocked or narrowed arteries reduce blood flow to the heart muscle, including the areas responsible for electrical conduction. Heart attacks can also damage the conduction pathways, leading to this type of block. Other heart conditions that can cause Mobitz type II include cardiomyopathy (disease of the heart muscle), myocarditis (inflammation of the heart muscle), and infiltrative diseases like sarcoidosis or amyloidosis. Previous heart surgery, particularly procedures involving the area near the AV node, can sometimes result in conduction problems. Certain medications can contribute to AV blocks, including some blood pressure medications (particularly beta-blockers and calcium channel blockers), anti-arrhythmic drugs, and digitalis. While less common, some people may be born with conduction system abnormalities, though Mobitz type II is more typically an acquired condition that develops later in life. Age-related changes in the heart's electrical system can also play a role, as the conduction pathways may become less efficient over time. In some cases, despite thorough evaluation, no specific underlying cause can be identified, which is referred to as idiopathic Mobitz type II AV block.

Treatment for Mobitz type II AV block typically focuses on preventing the progression to complete heart block and managing symptoms. Since this condition has a significant risk of suddenly progressing to complete heart block, most patients will need a permanent pacemaker, even if symptoms are minimal initially. A pacemaker is a small device implanted under the skin, usually below your collarbone, with wires (leads) that connect to your heart. The pacemaker monitors your heart rhythm continuously and delivers electrical impulses when it detects that natural electrical signals are blocked. This ensures that your heart maintains a regular, adequate rhythm. The pacemaker implantation is typically done as an outpatient procedure under local anesthesia with sedation. Before pacemaker implantation, your doctor will review all medications you're taking and may need to adjust or discontinue drugs that could be contributing to the conduction problem. However, it's important not to stop any heart medications without consulting your doctor, as some are necessary for other heart conditions. Once you have a pacemaker, you'll need regular follow-up appointments to monitor the device's function and your heart rhythm. Modern pacemakers can be checked remotely through special monitors in your home, reducing the frequency of office visits. Your healthcare team will also provide guidance on lifestyle considerations with a pacemaker, such as avoiding strong magnetic fields and informing other healthcare providers about your device before certain medical procedures.

The outlook for people with Mobitz type II AV block is generally very good when properly managed with appropriate treatment. With a pacemaker, most individuals can return to their normal activities and maintain an excellent quality of life. The device effectively prevents the dangerous progression to complete heart block and eliminates symptoms related to the irregular heart rhythm. Without treatment, Mobitz type II AV block carries significant risks because it can unpredictably progress to complete heart block, which can be life-threatening. This is why cardiologists typically recommend pacemaker implantation even for patients with minimal symptoms. The progression to complete block can happen suddenly and without warning, making preventive treatment essential. Modern pacemakers are highly reliable devices with batteries that typically last 8-12 years or longer, depending on how often the device needs to pace your heart. Most people with pacemakers can participate in most activities, including exercise, travel, and work, with very few restrictions. Regular follow-up care ensures that any issues with the device or changes in your heart condition are detected and addressed promptly. Your overall prognosis also depends on any underlying heart conditions that may have caused the AV block. Working closely with your cardiology team to manage these conditions, along with maintaining a heart-healthy lifestyle, can help optimize your long-term outlook and reduce the risk of other heart problems.

Current research in heart rhythm disorders continues to improve treatment options and outcomes for patients with Mobitz type II AV block. Scientists are developing more advanced pacemaker technologies, including leadless pacemakers that are entirely contained within the heart, eliminating the need for wires running from a chest device to the heart. These newer devices may reduce complications and improve patient comfort. Researchers are also investigating better ways to predict which patients with AV blocks are at highest risk for progression to complete heart block, potentially allowing for more personalized treatment decisions. Advanced imaging techniques and genetic studies are providing new insights into the underlying causes of conduction system diseases. Ongoing clinical trials are evaluating new pacemaker algorithms that can more naturally mimic the heart's normal electrical patterns, potentially improving quality of life and heart function for patients. Some studies are also exploring whether certain medications or interventions might help preserve the heart's natural conduction system in specific cases. While Mobitz type II AV block is well-understood and effectively treated with current technology, these research advances offer hope for even better outcomes and quality of life improvements in the future. Your cardiologist can provide information about any clinical trials that might be relevant to your specific situation and keep you informed about new developments in treatment options.