Introduction

Obesity has become a significant continual health issue around the world. Its prevalence rate is increasing in developed and developing countries. According to data from the World Health Organisation (WHO) from the global population those that are above the age of 18 are overweight (39%) and from these are obese (13%).¹ Weight is defined by body mass index (BMI) and can be calculated by a weight and height ratio (kg/m²). BMI is used to classify weight and to highlight whether an individual is underweight, of a normal weight, overweight or obese.²  

Cardiomegaly is a condition of the heart, where it has increased in size. It is typically a symptom that is enlightening of another health condition that may be affecting the heart. Some conditions (such as pregnancy) increase workload on the heart. Whereas, other conditions thicken the heart muscle or cause the wall chambers to dilate causing the heart to enlarge. Obesity plays an important role in atherosclerosis and coronary artery disease. This is mainly due to the factor of obesity altering structural and functional changes of the heart, and ultimately causing heart failure. The altered structure of the heart increases atrial fibrillation and sudden cardiac arrest.³         

Many studies as discussed by Ashraf have demonstrated there to be a relationship between obesity and cardiovascular diseases. These include acute myocardial infarction, stable coronary disease, heart failure, cardiac arrhythmias as well as sudden cardiac arrest. The increase in incidence of cardiovascular disorders has also shown a link with other conditions, such as hypertension, diabetes, dyslipidaemias and sleep apnea.¹  

Understanding heart enlargement (cardiomegaly)

Dilation cardiomyopathy 

This is where the walls of the heart become thin and dilate (stretch out), ultimately weakening the muscle. This enlarges the heart and leads to heart failure as the heart loses the ability to pump blood efficiently. 

Hypertrophy

The walls of the heart thicken, which causes the heart to function less efficiently. This is commonly seen in athletes and in pregnancy as the hearts in these groups go through a longer period of workload. Individuals may experience left ventricular hypertrophy (LVH) where the muscle is thickened of the left lower ventricle of the beating organ. This is the main chamber of the heart that goes through the majority of the function of pumping blood to the rest of the body. This condition is a cause of hypertension or aortic stenosis.

Symptoms

Cardiomegaly may not display symptoms until the condition becomes severe. Individuals may experience the following symptoms:

• Chest pain
• Heart palpitations e.g fluttering, rapid or a pounding heartbeat
• Arrhythmia e.g irregular heartbeat 
• Shortness of breath
• Dizziness  
• Fainting
• Swelling
• Rapid exhaustion due to physical activity 

Diagnosis

A diagnosis is usually taken place by a doctor by doing a physical examination of the heart as well as making an assessment of the following:

• Signs and symptoms
• Family history
• Medical history
• Test results

A physical examination to diagnose an enlarged heart may include:

• Echocardiogram 
• Electrocardiogram
• Chest X-ray 
• MRI (magnetic resonance imaging)
• Exercise stress test
• Blood tests (to test for thyroid disease and infectious causes)

Mechanisms linking obesity to heart enlargement

• Increased cardiac workload
• Hypertension (high blood pressure)
• Metabolic changes and hormonal imbalances

Obesity has an association with increased levels of plasma renin and aldosterone activity and high insulin levels. Which contributes to left ventricular hypertrophy (LVH). 

• Fat Deposition Around the Heart

One major hallmark of obesity is the increase in adipose tissue (body fat). Adipose tissue is a type of connective tissue that specialises in storing body fat (triglycerides). Adipose tissue not only plays a part in storing energy but also protects and insulates various body parts. Adipose tissue produces bioactive peptides, such as adipokines that may have an adverse effect on obese individuals due to the association with cardiac events.   

• Sleep apnea and respiratory issues

As adipose tissue in obesity is excessive, total blood volume also increases. As a result stroke volume and cardiac output are also elevated. Metabolic demands in obese patients are increased due to a larger cardiac output. As the heart rate is higher in comparison to a normal BMI due to an increase in sympathetic activation, stroke volume in obesity is also elevated. The left ventricle dilates to accommodate the blood from the venus return ultimately turning into hypertrophic.        

Adipokines have an effect on various organs in the body and regulate energy balance, angiogenesis, blood pressure, immunity, insulin sensitivity, lipid metabolism as well as hemostasis. In obesity adipokines are increased which causes an imbalance of differing physiological functions; these are linked with cardiovascular diseases. Leptin regulates the balance of the food that is consumed and energy metabolism. The increase of secreted leptin (by the extra adipose tissue) in obesity contributes to insulin resistance causing metabolic syndrome and predisposing to the adverse effects of cardiovascular disorder.    

Obesity has a direct increased risk of restrictive cardiomyopathy and heart failure due to the effects of diastolic dysfunction. The myocardial fibres that are infiltrated by fatty deposits in obese individuals cause myocardial structural deformity and dysfunction of the atria and the ventricles. Due to the pressure effect of adipose tissue, the myocardial cells degenerate leading to fibrosis. Usually the formation of adipose tissue causes myocardial cells to separate. This is further enhanced by an inflammatory process that is in relation to excessive secretion of adipokines. The consequence of fatty infiltration may eventually lead to restrictive cardiomyopathy. The increased pericardial fat content is characteristic of elevated risk of cardiomyopathy and worse cardiac outcomes.       

Individuals who are less active and those that are obese possess a higher pericardial fat count in comparison to those with a normal weight and are more active. Dilated cardiomyopathy in obesity is less common due to concomitant cardiac arrhythmias, coronary artery disease and hypertension. Although there is a higher risk of arrhythmia corresponding to sudden death of those who are morbidly obese. Obese patients are likely to possess an increased cardiac output, LVH, restrictive cardiomyopathy (a result of fatty tissue accumulation) which leads to the development of clinical syndrome of heart failure. From the associated risk factors the indirect effects are sleep apnea, which further supplement the risk of developing heart failure.²        

Preventive and treatment approaches

Reduction in weight can lead to dramatic effects on the cardiovascular system in obese patients. My formulating a structured weight loss programme can prevent unwanted cardiovascular effects that have an impact on obesity. Modifying dietary intake and increasing physical activity by organising an exercise programme. This will promote a negative energy balance which causes reduced levels of adipose tissue and a drop in adipokines. By reducing weight and exercising more leptin levels decrease, which overall reduce negative cardiovascular outcomes. Renin levels are also decreased due to weight loss. Insulin levels and aldosterone activity significantly improve the left ventricular wall thickness and function. 

Ashraf and Baweja have discussed that by making lifestyle interventions, such as exercise regimes, weight loss, caloric restrictions can significantly reduce up to 60% in developing diabetes type 2. 

Behavioural therapy could enhance diet and complying to exercise. Another suggestion to manage weight loss is to undergo surgically induced weight loss. This technique is helpful to reduce poor cardiovascular outcomes in morbidly obese individuals who have exhausted other means of weight loss options. Studies have shown promising short and long term improvements in morbidity and mortality after losing weight surgically.²      

Summary 

Obesity is a metabolic disorder, with increased rates of cardiovascular morbidity and mortality. Obesity is on the rise globally and currently is a pandemic in the United States as well as other western countries. It has a prevalence across all ages and races. Data has shown 50% of Amercians are overweight and around 30% are obese.²  
An individual with an excessive weight is at risk of attaining cardiovascular diseases. This is the consequence of obesity, however, there are other medical conditions that are associated with obesity (diabetes, insulin resistance, hypertension and sleep apnea). As the risk of cardiovascular disease is significantly higher in obese individuals, regular cardiology screening is crucial. Controlling symptom free obese patients are required for an early diagnosis and treating subclinical medical conditions.¹