What is Cardiomegaly?
Although the heart muscles contract and expand to facilitate the pumping of blood, the overall size of the heart remains the same. From birth up until your early 20s, your heart grows consistently, at which point it stops. The size of the heart is the same size as your fist, and it grows in size at that same rate from birth. After reaching this optimum size, your heart will stop growing, unless there is another factor causing it to. 
If the heat keeps growing in size, this isn’t a good sign, and it might be indicative of an underlying cause. When a person’s heart is larger than it should be, larger than their fist, this state is referred to as cardiomegaly. It is not a medical condition in and of itself but is more of a state of the heart which signals a probably serious underlying condition. 
How does Cardiomegaly develop?
As mentioned earlier, the heart pumps blood by contracting and expanding, but this is what you see from the outside. What’s really happening is the heart muscles contracting and relaxing, not the entire heart. In fact, only the muscles around the ventricles, the bottom half of the heart, do the pumping, so really it’s only the bottom part of the heart that expands/contracts. 
A problem may arise outside the heart, though, that affects the normal pumping of blood. For example, high blood pressure due to narrowing and hardening of blood vessels can hinder the passage of blood. Blood vessels are usually flexible to accommodate the pressure of the blood, but if they are inflexible, the passage of blood becomes more difficult.
Normal Heart vs. Cardiomegaly
Sensing this reduced blood supply to various parts of the body, your brain sends a signal to the heart to pump more blood and harder to compensate the resistance. The ventricles then become enlarged to accommodate more blood, and this stretches the muscles until they become thinner. Remember, the heart does not grow when you’re past your early twenties, so the heart muscles are unable to become any stronger. Instead, they become stretched out leading the increased size of the heart, cardiomegaly.
If the enlargement continues when the underlying cause is ignored, eventually the heart muscles become overstretched and unable to pump blood, leading to congestive heart failure.
How do you know you have Cardiomegaly?
Since the enlargement of the heart happens gradually and naturally, you may not notice any symptoms of your now enlarged heart. In fact, you will only start to notice the symptoms of congestive heart failure when your enlarged heart is beginning to fail, and some of these include: 
- rapid breathing especially when performing a physically tasking activity or when lying flat
- fatigue due to insufficient supply of oxygen and nutrients through the body
- leg swelling and edema, because the heart is unable to provide enough pressure to pump blood from the extremities
- heart palpitations and arrhythmias when the heart itself isn’t getting enough oxygen
- weight gain around the midsection
What can cause Cardiomegaly?
The most common causes of cardiomegaly are medical conditions that affect the cardiovascular system. The most common one is high blood pressure, which forces the heart to pump blood harder to compensate for the increased pressure in the blood vessels. Other cardiovascular causes include: 
- Coronary artery disease – when the arteries become wider due to increased blood pressure or a rapid heart rate. eventually, these wide arteries lower blood pressure forcing the heart to pump blood harder to compensate for the lost pressure
- Heart valve disease – several issues can cause the heart valves to fail, including infections, heart defects, and rheumatic fever, all of which prompt the ventricles to pump blood harder
- Fluid build-up around the heart – when fluid builds up around the pericardium, it may cause the heart to appear larger than it actually is
- Cardiomyopathy – this is a disease that directly affects the heart muscles, causing them to become thicker and stiffer
Still, there are causes which may not be directly related to the heart, such as:
- Thyroid disorders – both hypothyroidism and hyperthyroidism can affect the heart’s functioning by affecting the body’s metabolic rate
- Anaemia – without adequate red blood cells, the heart has to work harder to ensure there is adequate supply of oxygen around the body
- Excess iron in the body – excess iron that isn’t metabolized or excreted begins to accumulate around body organs, including the heart, causing the heart muscles to become weaker
- Amyloidosis – this is a condition which circulated abnormal proteins around the body through the blood and depositing them inside organs such as the heart
- HIV infection
- Drug abuse – cocaine and alcohol abuse can lead to the same
- Genetics – it is likely to acquire cardiomegaly if a close relative already has the condition
Diagnosis and Treatment of Cardiomegaly
To establish whether your symptoms are caused by cardiomegaly, tests are carried out using X-ray, CT scans, and MRI. All these are to establish the size of your heart and to check for any other anomalies in the heart’s structure. An electrocardiogram records electrical activity from your heart to establish your heart’s rhythm while an echocardiogram is used to illustrate how effectively your heart is pumping blood. Both of these tests are used to establish the extent of damage, and the location of severe damage. Blood tests may then be done just to rule out any other possible causes of the enlargement. 
X-Ray presentation of Cardiomegaly
Most people are able to recover normal heart functions, but only if the condition is detected early, after which it is not possible to repair the damage. Therefore, medications are prescribed to such affected individuals, and they may have to take them for the rest of their lives. Common medications for cardiomegaly include diuretics to reduce blood pressure by triggering frequent urination, ACE inhibitors, ARBs, and beta-blockers, also to reduce blood pressure. There are other medications which are aimed at improving the heart’s functioning such as antiarrhythmics and digoxin.
If the condition is too developed, a pacemaker may be used to regulate the heartbeat, or surgery performed to fix the problem. Some surgical procedures include bypass surgery and heart valve surgery. In the worst cases, a heart transplant may be needed if the heart muscles are damaged beyond repair.
- Heart size and its growth Available from: http://www.medicaldaily.com/pulse/human-body-grows-different-rates-its-organs-which-parts-never-stop-320560
- Definition of cardiomegaly Available from: https://en.wikipedia.org/wiki/Cardiomegaly
- Mechanism of the heart Available from: https://en.wikipedia.org/wiki/Cardiomegaly#Mechanism
- Symptoms of cardiomegaly Available from: http://www.webmd.com/heart-disease/guide/enlarged-heart-causes-symptoms-types#1
- Causes of cardiomegaly Available from: http://www.mayoclinic.org/diseases-conditions/enlarged-heart/basics/causes/con-20034346
- Diagnosing and treating cardiomegaly Available from: http://www.mayoclinic.org/diseases-conditions/enlarged-heart/basics/tests-diagnosis/con-20034346