What is Left Ventricular Noncompaction Cardiomyopathy?
Left ventricular non-compaction (LVNC) is a rare heart condition where the heart muscle (myocardium) is abnormally thick and sponge-like in one layer, and thinner in another. It is defined by visible muscle bundles (trabeculae), that connect deep recesses of the muscle with the main heart chamber (ventricular cavity). Although it generally affects the left side of the heart, cases of it affecting both left and right sides have also been reported. LVNC can be associated with muscle disorders, heart structural abnormalities, and genetic defects.
Sometimes, the diagnosis of this condition can be challenging because the same increased muscle tissue to regular heart tissue ratio used to identify LVNC can also be seen in about 20% of people without any heart disease. This ratio can also increase in normal conditions like pregnancy or high-level athletic activity. This probably happens due to an increased workload on the heart (preload).
LVNC often doesn’t show any symptoms; however, in certain cases, it could lead to a high risk of blood clots, poor heart function, dangerous irregular heartbeat, and even sudden cardiac death. Furthermore, LVNC can be associated with birth defects in the heart such as holes in the heart wall (ventricular septal defects), narrowing of the pulmonary artery (pulmonic stenosis), abnormalities of the tricuspid valve (Ebstein’s anomaly), underdeveloped left side of the heart (hypoplastic left heart syndrome), or two-leaf aortic valve (bicuspid aortic valve).
Recent studies suggest that the term “noncompaction” might not be entirely accurate. The increased muscle tissue (trabecular tissue) and compacted heart muscle (myocardial) layers seem to develop independently. However, as current classification systems recognize LVNC as a distinct heart condition, in this context, we will use LVNC to refer to the excessive heart muscle tissue.
Research suggests there are probably two different processes responsible for the increased heart muscle tissue (left ventricular trabecular tissue): 1) Genetic mutations causing the muscle layer to overdevelop compared to the compact layer, often emerging during childhood and associated with certain gene mutations, muscle disorders, and heart structural abnormalities. 2) Conditions that increase the heart’s workload like pregnancy, athletic training, and disorders of the oxygen-carrying component of blood (hemoglobinopathies). These conditions usually occur in adults and can often be reversible. This could also just be a normal variant in some people.
What Causes Left Ventricular Noncompaction Cardiomyopathy?
In the past, people believed that certain changes in heart development, specifically in the muscle tissues, could lead to a condition in which the heart muscle did not compact as it should. This was thought to be why some people ended up with a thinner layer of heart muscle. However, recent research paints a different picture.
Modern studies suggest that different parts of the heart muscle actually develop independently of one another. As such, it seems like the term “noncompaction,” which is used to describe the phenomenon of the heart muscle not compacting, might not be accurate. The same studies also suggest that having larger amounts of heart muscle may not necessarily be a problem related to heart development. This is because a similar pattern is also found in healthy individuals, athletes, and pregnant adults. Experts think that patients with larger amounts of heart muscle could have other heart-related conditions.
In some instances, it’s still unclear what exactly causes this development, whether it’s increased blood volume, a genetic predisposition, or potentially both.
For some patients, there’s no clear family history or identifiable genetic mutation linked to this condition. It’s thought that around 15 to 20 percent of such cases could be inherited and may show up earlier than those cases without a family history. Up to half of the patients with this condition could have relatives with another type of heart condition, like hypertrophic or dilated cardiomyopathy. Currently, about 40 different gene locations are associated with the structure of the heart muscle.
The most common genetic mutations linked to this condition involve certain proteins. Similarly, some patients with this condition can have a syndrome called Barth syndrome, which is linked to mutations in a specific gene. Additionally, this condition is common in up to 20 percent of patients with certain types of muscular dystrophy, and it’s associated with a quicker decline in heart function and higher mortality.
This condition is also linked to other neuromuscular disorders, like myotonic dystrophy and mitochondrial disorders. However, the exact cause-and-effect relationship between these conditions remains unknown and is an area of active research.
Risk Factors and Frequency for Left Ventricular Noncompaction Cardiomyopathy
LVNC, or left ventricular non-compaction, can be found in unborn babies and has a reported occurrence of around 0.8 per 100,000 infants per year and 0.12 per 100,000 children per year. Although LVNC can be found in people of all ages, it’s generally more common in children. A large number of these cases don’t show symptoms and hence never get diagnosed. Its prevalence is thought to be very rare, ranging between 0.014% to 0.26%.
However, the occurrence of LVNC significantly increases in those with a family history of heart muscle disease or known genetic mutations. LVNC happens to be 2 to 3 times more common in men than in women.
Signs and Symptoms of Left Ventricular Noncompaction Cardiomyopathy
Left Ventricular Noncompaction (LVNC) can occur in people of all ages, from babies to seniors. Diagnosis can sometimes happen by surprise during a heart scan, or symptoms may start showing in adulthood or even during infancy and childhood. For those who exhibit symptoms, the most common is heart failure. Other signs to watch out for include irregular heart rhythms, blood clots, and unexpected sudden death. A fascinating study noted that 61% of LVNC patients also had signs of nerve-muscle diseases upon detailed examination.
Deep irregularities in the heart muscle associated with LVNC can lead to the formation of blood clots and potentially blockages. The occurrence of these blockages is estimated to be between 13% and 24% in adults and anywhere from 0% to 38% in children. These blockages may result in temporary lack of blood to the brain (transient ischemic attacks), stroke, intestinal tissue death due to lack of blood (mesenteric infarction), heart attack, or peripheral embolism (blockage in other blood vessels).
For those diagnosed with LVNC who show no symptoms, have a normal heart scan result, and a normal heart function at the time of diagnosis, it’s crucial to dig into the family’s health history. The aim is to see if there are any instances of heart muscle disease or sudden death due to heart-related problems. Regular follow-ups are vital for such people, with some experts recommending a heart scan every three years.
Testing for Left Ventricular Noncompaction Cardiomyopathy
When diagnosing Left Ventricular Noncompaction Cardiomyopathy (LVNC), a condition where heart muscle appears spongy due to prominent heart muscle projections, a few different types of medical imaging can be used. Transthoracic echocardiography (an ultrasound of your heart seen through your chest wall) and Cardiac Magnetic Resonance (CMR – an MRI scan of your heart) are usually the main methods. Sometimes, Computed Tomography (CT – specialized X-ray test) and transesophageal echocardiogram (an ultrasound of your heart using a probe passed down your throat) may also be used.
Echocardiography is often used first because it’s quick and simple. The diagnosis is made if a particular ratio related to the heart muscle’s appearance (non-compacted to compacted myocardium ratio) is more than 2.0. Echocardiography can also detect other heart conditions that may be present. For adults who are obese, it might be hard to get a good echocardiography image, so a version that uses a special contrast dye can give better results, making it easier to see the difference between blood and heart muscle.
If the echocardiography doesn’t give a clear enough picture, CMR can be used. This technique can better distinguish between normal and non-compacted heart muscle (areas that appear more spongy). It’s useful for confirming the diagnosis when the echocardiography images aren’t definitive. Additionally, it gives a better view of any blood clots in the heart chambers and can show any heart muscle scarring, which can increase the risk of irregular heartbeats. This technique uses a different ratio (non-compacted to compacted myocardium ratio > 2.3) for diagnosis.
The Electrocardiogram (ECG) – a test that records the electrical activity of the heart – is also often used, although there isn’t a specific ECG result that indicates LVNC. Most LVNC patients show some kind of abnormal ECG, such as increased voltage of the complexes of waves that represents a heartbeat, a specific type of delayed conduction of the electrical signal through the heart (left bundle branch block), and changes in certain waves of the ECG related to heart muscle recovery after an electric signal (ST/T wave abnormalities).
Irregular heart rhythms, or arrhythmias, are also common with LVNC. Patients can present with atrial fibrillation (an irregular and often rapid heart rate), bradycardia (slow heart rate), or other abnormal rhythms. The risk of dangerous ventricular arrhythmias (arrhythmia originating in lower chambers of the heart) and fibrillation (very rapid irregular contractions of heart muscles) is higher when the efficiency with which the heart pumps blood is less than 35%. Atrial fibrillation is most common in adults, with 25-30% of LVNC patients experiencing it. Children with LVNC often present an abnormal electrical circuit in the heart (Wolf-Parkinson-White syndrome) or slow heart rate (sinus bradycardia).
Treatment Options for Left Ventricular Noncompaction Cardiomyopathy
Treatments for LVNC (Left Ventricular Noncompaction), a condition that affects the muscles of the heart, include managing related issues like atrial fibrillation (an irregular heart rhythm), thromboembolism (blood clots), and arrhythmias (irregular heartbeats). It’s challenging to determine the risk of blood clots for patients with LVNC if there are no other contributing factors like atrial fibrillation, presence of clot in the left ventricle of heart, or reduced EF (ejection fraction – a measure of how well your heart pumps blood).
Doctors must take all relevant factors into consideration in their treatment approach. The CHADS2/CHA2DS2-Vasc scores, scientific tools used to measure stroke risk, can help identify patients who are at risk. Blood thinning or anticoagulation medicines are typically recommended over antiplatelet agents, which have been found to be less effective. Direct oral anticoagulants (DOACs) which help to prevent blood clots, are generally the preferred method of prevention. Vitamin K antagonists, another kind of anticoagulant, are a standard treatment for existing blood clots, however, more evidence is showing that DOACs could also be used in such situations, though it has not yet been studied in children.
Anticoagulation Therapy (Blood thinning therapy)
LVNC with normal heart function: Even with normal heart function, deep recesses in the heart caused by LVNC could slow blood flow and lead to clot formation. Experts recommend considering anticoagulant therapy for these patients to prevent blood clots even though there’s no formal guidance.
LVNC with reduced heart function: If a patient has LVNC with reduced heart function, this could increase the risk of blood clot formation and consequent events such as stroke due to sluggish blood flow. In these situations, blood thinning therapy is usually administered when the ejection fraction is less than 40% or if the patient has a history of blood clots or atrial fibrillation.
LVNC with associated arrhythmias: About 25% to 30% of patients with LVNC also experience atrial fibrillation. These patients tended to have weaker heart function and higher chances of abnormal backflow of blood through the heart valves. For these patients, oral blood-thinning medication is recommended.
Management of congestive heart failure: Additional treatments may be needed for patients with a larger than normal LVNC and congestive heart failure, a condition where the heart can’t pump sufficient blood to the body. This might include diuretics (drugs that reduce fluid build-up), ACE inhibitors (which facilitate blood flow), or ARBs (which relax blood vessels). For patients with both LVNC and hypertrophic cardiomyopathy (a disease where heart muscle becomes abnormally thick), beta blockers or calcium channel blockers could be beneficial. Around 12% of patients with LVNC may progress to end-stage congestive heart failure and may then require a heart transplant.
Arrhythmia management: Irregular heart rhythms are managed according to standard procedures, and some patients, particularly those with severe irregular heartbeats, may benefit from an implanted cardiac defibrillator (ICD), a device that helps regulate heart rhythm. ICDs are recommended for patients whose ejection fraction is lower than 35%, in addition to blood-thinning therapy.
What else can Left Ventricular Noncompaction Cardiomyopathy be?
When identifying if a patient has Left Ventricular Noncompaction Cardiomyopathy (LVNC), doctors should also consider other conditions that could show an increased thickness of the left ventricle wall on medical images. These conditions could include:
- Left ventricular hypertrophy
- Dilated or hypertrophic cardiomyopathy
- Left ventricle thrombus (blood clot)
- False tendons
- Cardiac fibromas (heart tumors)
- Endomyocardial fibrosis (a type of heart disease)
- Cardiac metastasis (cancer spread to the heart)
What to expect with Left Ventricular Noncompaction Cardiomyopathy
The future health outcomes or prognosis for patients with left ventricular non-compaction (LVNC), a rare congenital heart condition, varies widely. This depends on the patient’s current health status, and if a genetic cause for this condition has been identified. Patients experiencing weakened heart muscle function, blood clot events, or irregular heartbeats (arrhythmias) are likely to have a more challenging health journey. If a patient’s LVNC diagnosis is linked with a known genetic mutation, it’s recommended that their closest relatives are also tested for this condition.
When children get diagnosed with LVNC, data from 10-year follow-up studies indicate that 90% of them had a reduction in heart muscle function. If LVNC is accompanied by heart failure and irregular heartbeats, the mortality rate is 13%. For adults diagnosed with LVNC, a six-year follow-up study showed a mortality rate of 50%, with 12% of those needing a heart transplant. In some cases, LVNC is highly connected with neuromuscular disease, which predicts a more severe prognosis. Generally, factors that indicate higher mortality include reduced heart muscle function, irregular heartbeats, and blood clot events.
Possible Complications When Diagnosed with Left Ventricular Noncompaction Cardiomyopathy
LVNC, or Left Ventricular Noncompaction, can cause heart problems, deadly heart rhythm disorders, and blood clots. These complications might eventually lead to a stroke. In cases of LVNC that are caused by genetic mutations and appear during childhood, the health issues often stem from related problems with the heart’s structure or muscle diseases. In adults, these health issues are majorly related to a decrease in the heart’s ability to pump blood, which could lead to heart rhythm disorders and stroke.
Main Effects:
- Heart problems
- Lethal heart rhythm disorders
- Blood clots leading to potential stroke
- Cardiac structure problems or muscle diseases (in children with genetic mutations)
- Decreased ability of the heart to pump blood leading to heart rhythm disorders and stroke (in adults)
Preventing Left Ventricular Noncompaction Cardiomyopathy
Having more knowledge about Left Ventricular Noncompaction (LVNC), a heart muscle disorder, can help identify it earlier in patients and their family members who might also be effected due to its genetic nature. By understanding this condition and how it progresses, patients can seek timely and correct medical help, which can help prevent complications like erratic heart rhythm (arrhythmias) and blood clots in the blood vessels (thromboembolism). Being informed can also help patients follow their treatment plan more closely. Plus, maintaining a healthy lifestyle, such as staying at a healthy weight, preventing diabetes, and managing blood pressure can also be beneficial.
