Cardiomegaly overview

# Overview
Cardiomegaly is defined as an enlargement of the heart above its normal size.  Cardiomegaly is generally first detected on chest X ray, and less often it is detected on routine physical examination.  Cardiomegaly may be the first sign of an occult systemic or cardiovascular disease.

# Pathophysiology
Cardiomegaly involves two main processes in the heart muscle.  Hypertrophy causes the heart to enlarge due to thickening to the cardiac muscle, and dilation causes enlargement due to stretching of the heart muscle.  Dilation occurs as a result of volume overload in the heart.

# Causes
There are many causes for the condition of cardiomegaly, including medications, genetic conditions, endocrine conditions, infectious processes, toxins and iatrogenic causes.

# Differentiating Cardiomegaly from other Diseases
There is a large differential for cardiomegaly, as it is a finding that is seen in many conditions.  The differential can be narrowed based on the chamber of the heart affected, and whether the cardiomegaly is caused by dilation or by hypertrophy.  Other physical findings, imaging studies, and laboratory findings need to be taken into consideration when determining the underlying diagnosis caused the manifestation of an enlarged heart.

# Diagnosis

## History and Symptoms
The history and symptoms can suggest the underlying cause of cardiomegaly.  The patient may have a history of rheumatic heart disease or congenital heart disease, or a history of alcohol abuse which may suggest dilated cardiomyopathy.  Symptoms such as chest pain, or other cardiac or respiratory symptoms may help in illiciting the underlying cause.

## Physical Examination
A comprehensive physical examination with a thorough cardiac exam will reveal cardiomegaly, and may indicated the nature of the underlying cause.  The body habitus of the individual needs to be taken into account when evaluating findings on cardiac examination.

## Laboratory Findings
Laboratory tests that should be obtained when a person is suspected or known to have cardiomegaly are: a complete blood count, thyroid stimulating hormone levels, and a blood urea nitrogen.  These are common, high yield tests.  Other tests can be ordered based on suspicions as to the underlying cause of the cardiomegaly, obtained through patient history and physical examination.

## Electrocardiogram
An EKG is a standard method of evaluating a patient with cardiomegaly.  It can help to determine the cause, severity, and the specific chamber which is affected.  A q wave would indicate an area of muscle death accounting for the enlargement, and ST elevation may suggest a myocardial infarction, myocarditis or pericarditis.

## Chest X Ray
Cardiomegaly is easily visualized on chest x ray.  Cardiomegaly is traditionally defined as a cardiothoracic ratio that is more than 0.5 on a PA film.  Other findings on chest x ray can help to determine the specific chamber that is contributing most to the enlargement of the heart.

## Echocardiogram
Echocardiogram recommended for those patients presenting suspected valvular disease, aberrant chamber size, ventricular function, and wall motion abnormalities.

## Other Diagnostic Studies
Exercise or pharmacological stress testing may be indicated in those patients suspected of having coronary artery disease.  Patients suspected of having valvular disease or coronary artery disease may need a cardiac catheterization for full evaluation following echocardiography.

# Treatment

## Medical Therapy
There are both acute and chronic pharmacotherapies used to manage the cardiomegaly.  Diuretics and ACE inhibitors are the standard therapy for chronic management of cardiomegaly.  Acute therapies include digoxin, diuretics, antiarrhythmics, pre-load and after-load reducing medications.

## Surgery
In patients who are awaiting a transplant for end-stage symptomatic heart failure, implantable ventricular assist devices may serve as a temporary aid for compensation. Transplantation may be considered in a few cases.