Introduction

Sudden Cardiac Arrest (SCA), as the name suggests, is the unexpected loss of heart function, which leads to unconsciousness and collapse. This condition can be fatal in minutes, so it requires immediate attention.¹ Different heart conditions can be responsible for SCA, and heart enlargement (cardiomegaly) is one of those conditions.² Heart enlargement is generally caused by some underlying conditions, which make the heart grow more than normal to function properly. So its treatment requires focus on managing the underlying conditions.³

Importance of preventing SCA in patients with heart enlargement

Structural and electrical changes due to heart enlargement lead to abnormal heart rhythm and impaired pumping function of the heart, which is responsible for life-threatening arrhythmias like ventricular tachycardia or fibrillation. These conditions can trigger Sudden Cardiac Arrest (SCA), so early addressing of structural issues and the electrical

abnormalities associated with heart enlargement is required. This can be achieved through regular monitoring, medication, and the use of devices like implantable cardioverter-defibrillators (ICDs), which can significantly reduce the chances of SCA and improve patient health. 

Understanding sudden cardiac arrest (SCA)

 SCA and its causes

Sudden cardiac arrest refers to a condition in which the heart suddenly stops beating due to loss of electrical function. Most of the time, it is caused by rapid and irregular functioning of the ventricles (ventricular fibrillation). Since it leads to Sudden Cardiac Death (SCD), early intervention with cardiopulmonary resuscitation (CPR) or an automated external defibrillator (AED) can be helpful to restart the heart and restore normal heart rhythm.⁴

Many reasons are responsible for Sudden Cardiac Arrest (SCA), but enlarged heart, arrhythmia, and coronary artery disease are three major contributing factors. An enlarged heart or cardiomyopathy occurs when the heart muscle becomes too thick and stretched, which makes the heart contract abnormally. Arrhythmias occur due to the disruption of electrical signals in the heart, which results in an unusual heartbeat and irregular pumping of blood. 

In coronary artery disease, arteries supplying blood to the heart get clogged, and the heart gets limited blood flow. Additionally, cardiac rhythm gets disturbed, and both these factors can lead to cardiac arrest.⁵ 

Risk factors for sudden cardiac arrest

Different factors are responsible for increasing the risk of sudden cardiac arrest (SCA). For example, the chances of  SCA increase with the increase in age, especially after menopause for women. People with black skin tone have twice the risk of experiencing sudden cardiac arrest (SCA) compared to people with white skin tone.⁶ People with previous heart problems like heart attack, irregular heartbeat and structural heart defects are more susceptible to SCA. Habits like heavy drinking and the consumption of drugs like cocaine, amphetamines, or marijuana also increase the risk of sudden cardiac arrest.⁶ Other health conditions like diabetes, kidney disease, or sleep apnea raise the chances.

Heart enlargement (cardiomegaly): Causes and risks

Common causes of heart enlargement

Heart enlargement can happen due to different reasons, including high blood pressure, coronary artery disease, and heart valve disease.⁷ Anaemia and thyroid disorders can lead to heart problems, which can also result in heart enlargement. Pregnancy can also cause a temporary enlargement of the heart.⁸ 

Cardiomyopathy is an acquired or hereditary disease of the heart muscle. This condition also causes the heart to become thick or rigid, making it difficult for the heart to pump blood to the body, and can lead to heart failure. Alcohol abuse is one of the main factors responsible for cardiomyopathy. Additionally, the use of stimulants like cocaine and methamphetamine can also lead to heart enlargement..

How enlargement increases the risk of arrhythmias and sudden cardiac arrest:

According to the American Heart Association, heart enlargement (cardiomegaly) causes structural and electrical abnormalities in the heart, which increase the risk of cardiac arrest by disturbing cardiac rhythm. Prior heart attack or other chronic heart conditions result in scarring of heart tissue, which can disturb the electrical signals and ultimately lead to life-threatening fibrillation or ventricular tachycardia. Additionally, thickened and weakened heart muscles in an enlarged heart also cause electrical instability. These factors collectively contribute to the chances of Sudden Cardiac Arrest (SCA) in patients with an enlarged heart.²

Prevention strategies for SCA in heart enlargement patients 

Prevention of Sudden Cardiac Arrest (SCA) in enlarged heart patients requires a mixed approach, which includes:

Lifestyle modifications

Individuals should consume a heart-healthy diet that mainly contains fruit, vegetables and whole grains. They should also minimise intake of salt, trans fats and sugar, which prevent obesity, high blood pressure and other cardiovascular problems. Regular exercise is important to strengthen the heart and improve blood circulation. However, the intensity of the exercise should be based on individual's heart condition, as recommended by a cardiologist. Quit smoking, because it causes atherosclerosis (hardening of the arteries), which produces an extra burden on the heart.

Medical management

Patients with heart enlargement are prescribed medicines including beta-blockers, angiotensin-converting enzyme (ACE) inhibitors, angiotensin II receptor blockers (ARBs), and diuretics. These are used to prevent further heart damage, to manage heart failure, and to reduce arrhythmias. In high-risk patients, implantable cardioverter-defibrillators (ICDs) can be implemented to monitor the heart's rhythm and correct dangerous arrhythmias, such as ventricular fibrillation, that may lead to SCA.²

Monitoring and risk factor management

For early intervention, regular screening of hypertrophic cardiomyopathy, arrhythmias, valvular diseases, and other cardiac abnormalities is essential. This includes genetic testing for conditions like Long QT syndrome or Brugada syndrome, which predispose individuals to arrhythmias. Screening relatives for asymptomatic left ventricular dysfunction (a condition that leads to heart failure) helps to identify individuals at risk before symptoms arise.

Emergency preparedness

Since SCA often strikes without warning, educating family members, caregivers, and even community members on cardiopulmonary resuscitation (CPR) and how to use an automated external defibrillator (AED) is important. Immediate CPR can save valuable time before medical help arrives.²

Family education and Genetic counselling

Family history

Understanding one’s family history of heart disease or sudden cardiac death is critical for assessing individual risk. Family members of patients with known heart conditions should be educated about their cardiovascular health and the importance of regular screening. For those with inherited heart conditions, consulting with a genetic counsellor can help identify any genetic predispositions to arrhythmias or cardiomyopathies, facilitating early diagnosis and personalised prevention strategies.

Conclusion

Preventing sudden cardiac arrest (SCA) in patients with heart enlargement requires a comprehensive approach that addresses both the underlying causes and the resulting structural and electrical changes in the heart. By adopting lifestyle modifications such as a heart-healthy diet, regular exercise, and smoking cessation, coupled with medical management through medications and devices like implantable cardioverter-defibrillators (ICDs), the risk of life-threatening arrhythmias can be significantly reduced. Regular monitoring, early screening, and genetic counselling also play critical roles in identifying at-risk individuals and facilitating timely interventions. Furthermore, educating patients and their families about emergency response measures like CPR and AED use can help save lives in cases of sudden cardiac arrest.