Introduction

The heart is a vital organ, working tirelessly in our bodies to keep us alive, even before birth. Consequently, there are a plethora of different things that can go wrong, causing the heart to malfunction. The ventricles are the larger bottom chambers of the heart, and they pump blood out of the heart: first to the lungs, and then to the rest of the body. This is done in sync so the heart can work efficiently and use pressure to its advantage to ensure the tireless heart doesn’t have to work too hard. However, when the heart can no longer pump blood from the ventricles in a regular rhythm, issues arise. This is called a ventricular arrhythmia. With many different changes to the regular rhythm of a heartbeat, many treatment avenues may be pursued. Specifically, this article will focus on ventricular arrhythmias in enlarged hearts and how they can be managed efficiently to ensure the best outcomes for patients.

How does a heart become enlarged?

One’s heart is ordinarily roughly the size of one’s fist, with children’s hearts being smaller than adults’. As we grow, our hearts grow with us, so they can keep pumping blood effectively to all the cells in our bodies. As we all know, our hearts are sensitive and can adapt to changes quickly, with heartbeats increasing whenever we are short of breath or afraid, and slowing when we take deep breaths. In the first couple of decades of life, about 1% of the heart muscles (cardiomyocytes) are regenerated each year, with this halving in later decades.^1,3 The heart can change to suit the body’s needs.⁴

For example, if you gain weight, more cells in the body require blood to reach them. Therefore, the same heart needs to work harder to pump blood to all the cells in your body. In other cases, if there are issues with oxygenating blood in the lungs or getting blood to the lungs in the first place due to any number of lung issues (hypertension etc.), then the heart ventricles will also have to pump harder to make sure that the blood can quickly pick up oxygen and travel around the body to prevent the cells in your body from dying. High blood pressure can also mean that the heart has to pump harder to make sure that the blood can reach all the cells, whilst fighting against the higher resistance in the blood vessels. All these demands on the heart can be straining. Over time, the heart can grow larger to accommodate these issues so it can pump once but generate more force with every beat. This allows it to pump harder without each cell having to pump harder than normal, or faster than is required in a normal state.

The condition of an enlarged heart, also known as cardiomegaly, can be good for reducing stress on the heart over a long time. However, with more heart cells working in sync to accommodate the body’s needs, there is an increased risk of the left and right ventricles irregularly pumping, also known as an arrhythmia. Although this is only one of the risks of an enlarged heart, with others including an increased risk of stroke, organ damage and fluid build-up in other parts of the body, it can be quite serious and have a multitude of downstream effects on the body. As such, treatment is often required to keep the heart functioning well.

Different types of ventricular arrhythmias

As there are different reasons why a heart may become enlarged, many types of ventricular arrhythmias can result. Treatment can sometimes be the same or different, depending on the extent and severity of the arrhythmia. Generally, there are approximately 14 different classes of arrhythmias which can be differentiated on electrocardiograms (ECGs). Generally, this shows that the blood is pumped from the atria into the ventricles, then the electrical signal in the heart travels down the central septum, depolarises the main body of the ventricles to push, and finally the topmost part of the ventricles contract to push the last bit of blood out of the ventricles. This is followed by a rest period, which lets the heart refill with blood before the cycle restarts.²

Arrhythmias in the ventricle can include issues such as:

• The ventricles pump earlier than they should, with very little/no blood into the ventricles (premature ventricular complex (PVC))
• The ventricles pump more frequently than they should (tachycardia)
• The ventricles pump when the heart should be relaxing (short-coupled PVC)
• The ventricles constantly contract for more than 3 beats without any relaxation or atrial contraction (non-sustained ventricular tachycardia)
• Changes in the pattern of how the pumping signal travels down the septum and up the ventricles (uniform or polymorphic ventricular arrhythmias)
• Irregular spasming of the heart where there is no distinct pumping action by the atria or the ventricles, making it very difficult to pump blood out of the heart properly (ventricular fibrillation)

Managing ventricular arrythmias^2,5

Because of the many issues that can arise, treatments for arrhythmias can differ depending on the type of ventricular arrhythmia.

All cardiac issues should first be treated with lifestyle changes, such as exercising more and eating healthy foods to lower blood pressure and encourage the body to heal. However, in severe cases, this may not be able to reverse the damage already caused to the heart, and other types of intervention may be required.

Types of ventricular tachycardia, which include the ventricles beating too quickly or beating during times of heart relaxation, can be treated with medications such as β-blockers. These medications block receptors in the heart, which can slow down how quickly the heart contracts. Other medications can be given to slow the irregularly active heart, such as amiodarone, flecainide, propafenone, or sotalol. Short-coupled PVC arrhythmias may also be treated with non-dihydropyridine calcium channel blockers like verapamil if a cardiac arrest is suspected.²

For medium severity, targeted arrhythmias, radiofrequency ablation can be used if the medication doesn’t work.² This technique focuses on destroying a small part of the enlarged heart muscle that is responsible for the irregular rhythm in a minimally invasive manner, thus leaving the patient with a healthy heart muscle. However, this can only be used for some arrhythmias where the responsible unhealthy heart muscle can be distinguished. Catheter ablation can also be used to destroy the responsible heart muscle in the enlarged heart, which may include freezing parts of the heart to destroy the unhealthy cells instead.² Both these methods are associated with their risks, and one may suit the patient better than the other.

For those with enlarged hearts and high risks, a loop recorder device may be inserted under the chest skin to monitor the heart rhythm, so if an arrhythmia is detected, the patient/ appropriate healthcare physicians can use the information to understand which type of ventricular arrhythmia is occurring over a long time. This is used to decide the best course of treatment if the type cannot be identified in the hospital with an ECG.

If the medication fails to work and the arrhythmia is widespread, an operation can insert an implantable cardioverter defibrillator (ICD) into the heart.⁵ Whenever an arrhythmia is detected,  this device delivers a small shock to the heart and makes the heart restart to beat with a regular rhythm.

In emergency cases of ventricular fibrillation, where the heart is unable to pump blood to the body due to spasms caused by the arrhythmias, defibrillators can deliver an electric shock to the heart to reset its function. If one is not available in emergencies, cardiopulmonary resuscitation (CPR) can be carried out by a caregiver: by breathing into the patient’s mouth and physically pumping blood around the body by pressing down on the chest in a regular rhythm until a defibrillator can be accessed.⁵ If the defibrillator doesn’t work, then medications and heart surgery can be corrective, with an ICD implanted to prevent further issues.

Left-ventricular assist devices (LVADs) can be inserted to help very poorly functioning hearts push blood around the body whilst a transplant is waited for in very severe cases where the enlarged heart is no longer able to function on its own due to arrhythmias and other issues.²

Summary

Many factors can cause an enlarged heart and compromise the heart’s ability to pump blood around the body in a regular rhythm. A lack of regularity can result in various issues, such as oedema or organ damage, so a regular ventricular rhythm is vital. Early treatments include lifestyle changes and medications that affect the heart, with later management including surgery to destroy the damaged cells or insert devices that can help monitor or control heart rhythms. In severely damaged hearts, LVADs can assist heart function until a transplant can be organised. Otherwise, electric shocks can be delivered to the heart in emergencies to reset the rhythm, although this may not always be successful.