Overview

The heart and kidneys are essential organs that work together to keep the body functioning properly: 

• The heart circulates oxygenated blood all around the body in a bid to deliver nutrients and at the same time, eliminate waste products. The cardiovascular system includes the heart, blood and blood vessels¹
• Kidneys: Clean blood, get rid of unwanted substances in the body, and maintain blood pressure as well as the balance of electrolytes. It also plays a role in the production of red blood cells and the maintenance of strong bones²

The heart and kidneys are closely linked, and problems with one organ can affect the other: 

• Heart failure: Any obstruction can cause a backlog of blood in the heart, which can deprive the kidneys of the necessary doses of oxygenated blood. This can cause kidney disease²
• Kidney disease: For individuals suffering from a kidney ailment, the body fails to manufacture red blood cells and also to monitor blood pressure. This can lead to anaemia and problems with the heart³
• High blood pressure can result in increased water and sodium retention in the kidneys and cause blood vessel diseases and kidney diseases⁴
• When monitoring for possible heart disease, the doctors normally assess kidney function. Basic blood work can assess a person’s kidney function by examining the degree of creatinine, a waste by-product of the kidneys

Heart enlargement (Cardiomegaly)

Cardiomegaly refers to an increase in the size of the heart, otherwise known as an enlarged heart. It is not a disease per se – it is a symptom that another disease is targeting the heart. Certain other conditions, like pregnancy, impose a level of load on the heart. Other conditions can cause the heart muscle to thicken or the heart chambers to stretch, which makes the heart bigger.⁵

Causes

Cardiomegaly may result from any condition that affects the function of the heart, including damage to the heart, or any condition that makes the heart work harder than before, such as pregnancy. Sometimes, the heart muscles also weaken for a reason that is not very clear, and they become larger than usual. This condition is referred to as idiopathic cardiomyopathy.⁶

Conditions associated with an enlarged heart include:

1. Heart condition present at birth (congenital heart defect). Diseases of the heart may lead to abnormal physical attributes and function of the cardiac muscles, as they become bigger and tender
2. Damage from a heart attack. Heart remodelling, for example, scarring or other injuries to the building blocks of the heart, can compromise its ability to pump blood to vital organs of the body. This pressure causes an increase in the size of the muscle of heart muscle as well as failure of the heart
3. Cardiomyopathy usually weakens the heart muscle, making it stiff or thick. Some can cause restricted blood flow, making it tough for the heart to pump blood throughout the body.
4. Specifically, it is pericardial effusion, which is, in fact, an accumulation of fluid in the pericardium around the heart. An accumulation of fluid inside the sac that encapsulates the heart can lead to this cardiac dilation, which can be evidenced on a chest X-ray
5. Heart valve disease. Four valves in the heart help the blood to circulate correctly. Abnormality in any of the valves leads to the blockage of blood flow as well as an increased size of the heart chambers
6. High blood pressure or hypertension. If you have high blood pressure, then the heart may have to pump harder. These changes can make the heart muscle increase its size and become thin and weak
7. When the blood pressure in the arteries in the lungs is increased, it is called pulmonary hypertension. The heart has to pump harder to shift blood from the lungs through the heart and then in the reverse direction. Pulmonary hypertension might thus result in increased size or enlargement of the right side of the heart
8. Decreased haemoglobin and haematocrit, with or without anaemia. In anaemia, there are short healthy RBCs to transport an adequate flow of oxygen to the body tissues. To compensate for the small amounts of oxygen the body is supposedly receiving in the blood, the heart must pump out more blood
9. Thyroid disorders. Patients with an under-functioning thyroid gland (hypothyroidism) and an over-functioning thyroid gland (hyperthyroidism) are also vulnerable to heart trouble and may develop an enlarged heart
10. A condition in which the body contains excess amounts of iron (haemochromatosis). Iron can accumulate in different organs, like the heart. That could lead to enlargement of the left lower heart chamber
11. A type of amyloidosis localised in the heart that produces deposits of proteins that are not usually found in human tissues. This is a very uncommon disease that results from the build-up of certain proteins known as amyloids in the blood and clotting in the body organs, and the heart in particular. Then, in the heart, the amyloid protein deposit leads to an irreversible condition known as cardiac hypertrophy. The circulatory system has to circulate blood in the body, and the heart needs to pump harder to pump blood into the body
12. Aerobic exercise. In some athletes, the heart increases its gain in size due to repeated exertion and possibly sustained training. In general, this type of enlarged heart is not categorised as one, and therefore, it does not require any management
13. Fat around the heart. Some patients are usually overweight, and if the fat deposits are around the heart, then on X-ray, the fat is seen as a shadow around the heart. So, in most cases, no treatment is needed unless others are present that can affect the heart.

Symptoms

Many people with cardiomegaly will remain asymptomatic at the early stages, with the condition worsening as time goes on.⁶ The symptoms you may experience include:

• Shortness of breath
• Chest pain
• Heart palpitations (rapid, fluttering, or pounding heartbeat)
• Arrhythmia (irregular heartbeat)
• Dizziness
• Fainting
• Rapid exhaustion with physical activity
• Swelling

Kidney function and kidney diseases

The kidneys are vital organs that perform many functions in the body, including:

• Filtering blood: The kidneys work like a filter, which cleanses the blood and throws off the waste products dissolved in water, chiefly in the form of urine. The kidneys are unique organs of the human body that filter about 120 – 150 litres of blood daily
• Regulating chemicals: In the bodily system, kidneys help in the chemical balancing of complexes such as sodium, potassium, and calcium, among others
• Controlling blood pressure: The kidneys also secrete hormones that regulate high blood pressure
• Stimulating red blood cell production: They also secrete hormones, which help the bone marrow to form red blood cells
• Producing vitamins: The kidneys generate vitamins that are necessary for the regulation of growth

Chronic kidney disease

Chronic Kidney Disease (CKD) is defined as a primary renal disease that manifests clinical signs of kidney function decline over a certain period. It is defined by the presence of kidney damage or a decreased estimated glomerular filtration rate (eGFR) of less than 60 ml/min/1.73 m,² persisting for three months or more.⁵ CKD can arise from various causes, including diabetes and hypertension, and it significantly impacts overall health, leading to complications such as cardiovascular disease, anaemia, and bone disorders.⁷

Progression of CKD over time

CKD progresses through five different stages

• Stage 1: Kidney Damage with Normal Function
• Stage 2: Chronic Kidney Disease – With a Mild Reduction in Kidney Function
• Stage 3: Moderate Decrease in Kidney Function

Subdivisions:

• Stage 3a: eGFR 45-59
• Stage 3b: eGFR 30-44
• Stage 4: Severe Decrease in Kidney Function
• Stage 5: Kidney Failure

CKD has extensive health implications

• Cardiovascular Disease: Increased risk due to the interplay between kidney function and heart health
• Anaemia: Resulting from reduced erythropoietin production by damaged kidneys
• Bone Disease: The altered metabolism of calcium and phosphorus leads to bone disorders
• Fluid and Electrolyte Imbalance: Can cause complications such as hypertension and oedema⁷

The link between heart enlargement and kidney function

The relationship between heart enlargement (cardiomegaly) and kidney function is significant, as both conditions are interlinked in a complex manner that affects patient outcomes. Here’s an overview of how these two vital organs influence each other.

Connection between heart enlargement and kidney function

1. Cardiovascular-Kidney Interaction

Of course, hypertension and diabetes are also risk factors for both CKD and heart disease among adults. This interaction plays a positive and negative cycling role that suggests one organ system pulling down the performance of the other. For example, when the patient develops renal disease, the heart becomes overburdened when pumping blood and can cause heart failure and enlargement.⁸

• Prognostic Value of Cardiothoracic Ratio (CTR)

Some investigations published in the recent past have focused on the application of the cardiothoracic ratio (CTR) in estimating the survival of patients with CKD. However, they found an association between a higher CTR and higher risks of developing end-stage renal disease or dying from cardiovascular causes. Specifically, patients with baseline CTRs greater than 0.57 showed significantly worse outcomes compared to those with lower ratios. This suggests that monitoring heart size can be crucial in managing CKD.⁹

• Mechanisms of Interaction

The kidneys are involved in controlling blood pressure and water levels, which have a direct impact on the health of the heart. Reduced kidney function means that fluid accumulation can soon ensue, which raises blood pressure, creating an extra burden on the heart. On the other hand, diseases like Congestive heart failure can cause clinical deterioration in renal function because of inadequate oxygen supply to the kidneys.¹

Clinical implications

• Increased Risk of Complications:

Investigating hospitalisations related to worsening kidney function shows that patients with CKD have an increased risk for cardiovascular diseases such as heart failure. Around one in four CKD patients might suffer from CCF, and this risk rises as the patient’s renal disease progresses.¹

• Treatment Strategies

Managing both conditions concurrently is essential. For instance, drugs developed for the treatment of diabetes, like SGLT-2 inhibitors, demonstrated a cardio-renal protection effect. Also, one can treat risks associated with both heart and kidney diseases with the following lifestyle changes: exercise and diet.⁸

• Importance of Multidisciplinary Care

Cooperation between nephrologists and cardiologists is crucial when it comes to planning the best treatment strategy for patients with heart enlargement and renal failure. Such an approach can allow for better treatment outcomes as numerous aspects must be considered when treating both disorders.¹

Summary

The heart and kidneys work together to maintain proper body function, and interconnected problems can arise. Heteromorphic cardiomegaly may present other problems of the body due to the influence of such factors as hypertension or anaemia. Chronic kidney disease decreases overall health and can cause other problems, including heart disease. The relationships between nephrology and cardiology are very significant in managing people with heart enlargement issues and kidney problems.