What is Ventricular Fibrillation?
Ventricular arrhythmia (VA) refers to problems with the heart’s rhythm that start in its lower chambers, called ventricles. These complications include a variety of conditions such as ventricular tachycardia (VT), where the heart beats too fast, premature ventricular contractions (PVC), irregular heartbeats, and ventricular fibrillation (VF), where the heart quivers instead of pumping.
One type of arrhythmia is called Wide Complex Tachycardia (WCT), which is any fast heartbeat that has a specific pattern on an electrocardiogram (ECG), a test that checks the electrical activity of your heart. VF, a type of WCT, is caused by disorganized electrical signals, often making the heart beat over 300 times a minute. It’s important to note that VF is a very dangerous condition because it disturbs the heart’s normal functioning, which can lead to sudden cardiac death (SCD) if not treated promptly.
Almost 70% of people who have a cardiac arrest, which is when the heart suddenly stops beating reliably, have VF. Without immediate treatment, VF can cause death within minutes. Survival rates for people who suffer VF outside hospitals have slightly increased, but many survivors have lasting brain damage or neurological problems due to a lack of oxygen during the cardiac arrest.
What Causes Ventricular Fibrillation?
Ventricular fibrillation (VF), a serious type of heart rhythm disorder, is often linked to pre-existing heart disease. It’s been found that between 3% to 12% of patients who experience myocardial infarction (MI) or a heart attack, develop VF during the first phase.
Heart attack patients who show full blockage in their heart’s blood vessels (coronary occlusion), damage to the front wall of the heart (anterior wall infarction), irregular heartbeat (atrial fibrillation) and chest pain before a heart attack (pre-infarction angina) have a higher chance of developing VF.
There are also several common conditions linked with VF. These include electrolyte imbalances (low/high potassium levels, low magnesium levels), acidosis (too much acid in the body), low body temperature, low oxygen levels, different types of heart disease (cardiomyopathies), a family history of sudden heart-related deaths, genetic defects affecting heart rhythm (congenital QT abnormalities, Brugada syndrome), alcohol consumption, and having a history of ventricular arrhythmia (VA) especially specific types of irregular heartbeats (monomorphic or polymorphic VT).
In some cases, these irregular heartbeats can lead to VF in susceptible individuals. There’s a growing understanding that our genes can make us more likely to experience VF. The AGNES research study identified a particular genetic marker (at 21q21) that appears to make individuals more prone to VF.
Risk Factors and Frequency for Ventricular Fibrillation
In 2017, the American Heart Association estimated that there were 356,500 cases of sudden heart attacks outside of a hospital setting. About 23% of these cases were treated by emergency services and were initially diagnosed with ventricular fibrillation or ventricular tachycardia, which are serious heart conditions. In fact, more than 60% of all deaths from heart conditions are due to sudden cardiac arrests, making it the top cause of death worldwide.
Modern medical devices like the implantable cardioverter-defibrillator have helped to decrease these numbers. It has been observed in multiple studies that ventricular fibrillation is the most frequent abnormal heart rhythm found in patients with sudden cardiac death. Moreover, in patients admitted to the hospital with a heart attack, between 5% and 10% have ventricular fibrillation or ventricular tachycardia, and an additional 5% will develop these conditions within 48 hours of being admitted. However, these figures might be an underestimation, as they often do not include those who suffer a sudden cardiac arrest outside of the hospital.
Looking at data from the Resuscitation Outcomes Consortium, about 31.4% of patients with ventricular fibrillation survive until they are discharged from the hospital.
Signs and Symptoms of Ventricular Fibrillation
Ventricular fibrillation (VF) often presents itself as a sudden cardiac arrest, which can lead to sudden cardiac death. This happens when the heart’s ventricles don’t properly contract, leading to insufficient blood flow. Some patients might experience symptoms like chest pain, difficulty breathing, nausea, and vomiting before the event. For those with known heart conditions like coronary artery disease or congestive heart failure, they might notice worsening symptoms like chest pain, shortness of breath, difficulty breathing at night, and swelling of the feet. At the time of the VF event, patients usually lose consciousness, become unresponsive, and no detectable pulse. Without immediate medical help, this can lead to death in just a few minutes. People with implantable cardioverter defibrillators (ICDs) installed for preventing such heart rhythm issues can experience shocks from the device firing during VF.
Testing for Ventricular Fibrillation
When you experience sudden symptoms, doctors use different methods to diagnose what might be going wrong. One such method is using an ECG, or an electrocardiogram, which is a test that measures the electrical activities of the heart.
Specific ECG findings that doctors look for can include fibrillation waves, which vary in size and shape, and a fast heart rate anywhere from 150 to 500 beats per minute. Furthermore, if you experience three or more episodes of fibrillation or receive several shocks from an implantable cardioverter defibrillator (ICD) within 24 hours, this is referred to as a fibrillation storm.
After surviving a fibrillation episode, doctors should carefully review your medical history and current medications. Doctors will also check for reversible causes of fibrillation such as imbalances of electrolytes (the minerals that help your body’s functions), acidosis (high levels of acid in your blood), and hypoxia (a shortage of oxygen). They also look for underlying heart disease with a heart scan (echocardiogram) and an emergency image of your blood vessels (angiogram). It is important to note than more than half of all Out of Hospital Cardiac Arrest cases reveal significant heart disease upon examination.
Alongside an ECG, some of the other recommended tests include blood tests to check for electrolytes, arterial blood gas, complete blood cell count, heart enzymes, drug levels, toxicology screen, and B-type natriuretic peptide (BNP) levels, which can indicate heart failure. The ECG may be able to identify further issues such as heart attack, Brugada Syndrome (a condition that causes a disruption of the heart’s normal rhythm), Long or Short QT interval (heart rhythm disorders that can cause fast, chaotic heartbeats), Wolff-Parkinson-White Syndrome (an extra electrical pathway between your heart’s upper and lower chambers causing a rapid heartbeat), digitalis toxicity (a complication arising from the drug digitalis), or an Epsilon sign (a mark that indicates arrhythmogenic right ventricular cardiomyopathy, a type of heart disease).
An echocardiogram is typically conducted to check the motion of the heart wall, how well the heart is pumping blood (ejection fraction), and any issues with the heart valves. It can also spot any fluid that might have gathered around the heart due to cardiopulmonary resuscitation (CPR).
Finally, once the patient is stable, an electrophysiology study (EPS) can be carried out. This test will measure the electrical activity and electrical pathways of your heart, which can help doctors determine how to manage your fibrillation, and where it might be starting. People who have inducible fibrillation may be candidates for an ICD, a small device placed in the chest or abdomen to help control irregular heart rhythms.
Treatment Options for Ventricular Fibrillation
Patients coming in with a condition known as ventricular fibrillation (VF), a serious heart rhythm disturbance, must receive immediate medical care due to its high risk of death. The medical team should launch into clear, well-established care guidelines to increase the patient’s chances of survival.
While started with life-saving CPR, the heart’s rhythm should be assessed. In the event of VF, a medical device called a defibrillator is used to deliver an electrical shock to the heart to try and restore a normal rhythm. The quicker the defibrillation, the better: patients who receive immediate defibrillation have a higher survival rate compared to those for whom the procedure is delayed.
Along with defibrillation, patients may receive certain medications like epinephrine and amiodarone. Amiodarone has been shown to improve patient survival until they reach the hospital. It’s also important to identify and treat the underlying cause of VF during the resuscitation process. Once normal heart function has been restored, doctors can then assess if coronary artery disease (a common heart condition) is present.
Preventing VF from happening in the first place is a major focus. Since a less severe heart rhythm disorder (ventricular tachycardia, or VT) often progresses into VF, identifying these other rhythm disorders early can help prevent VF. Those who have a family history of inherited heart rhythm disorders should have genetic testing and counseling to better understand and manage their risk.
Amiodarone was studied as a drug to prevent sudden cardiac death, but its effectiveness is disputed. There’s no clear evidence to suggest that it benefits survival more than a placebo or an implantable cardioverter-defibrillator (ICD), a small device placed in the chest to regulate abnormal heart rhythms. Some other drugs, like statins and beta-blockers, have shown potential for reducing the risk of sudden cardiac death.
ICDs have proven to be beneficial in preventing sudden cardiac death in several control trials. They’re recommended for patients at higher risk of life-threatening VF and those who’ve experienced VF or sustained VT before. This small device can continuously monitor heart rhythm and deliver an electrical shock if an irregular heart rhythm is detected, helping to avoid sudden cardiac death.
What else can Ventricular Fibrillation be?
It’s crucial to distinguish between ventricular fibrillation (VF) and other conditions such as pulseless electrical activity or asystole, as treatment varies according to specific guidelines. Other sudden collapse causes like aortic dissection and pulmonary embolism should also be kept in mind. Some conditions may look like VF on a heart monitor and should be ruled out. These include:
- Polymorphic ventricular tachycardia
- Torsade de pointes
- Ventricular flutter
- Pulseless electrical activity
- Accelerated idioventricular rhythm
- SVT with aberrancy
What to expect with Ventricular Fibrillation
The prognosis, or likely course, of Ventricular Fibrillation (VF, a severe heart rhythm problem) depends on the speed of intervention and use of a defibrillator. Early intervention can lead to survival rates as high as 50%. For patients with ST-elevation MI (a type of heart attack), having VF in less than 24 hours increases the risk of death compared to those who experience VF after 24 hours.
Ventricular Fibrillation happening outside the hospital can be often reversed as defibrillators are available in many places nowadays. However, the chance of successfully reversing VF drops by 5-10% for every minute that passes. Even in an ideal scenario, 30-40% of patients would survive, but a lot of them may develop residual neurological issues due to lack of oxygen. Complete recovery is uncommon.
Possible Complications When Diagnosed with Ventricular Fibrillation
Possible Consequences:
- Brain damage due to lack of oxygen
- Irregular heart rhythms after defibrillation
- Injuries resulting from CPR and revival efforts
- Skin burns
- Long-term disabilities
- Heart muscle injury
- Death