If you're experiencing concerning symptoms that your doctor suspects could be caused by an underlying heart condition, he or she has likely ordered a battery of heart tests.

These may include:

• Electrocardiogram (EKG or ECG)
• Echocardiogram
• Stress test
• CT scan
• Coronary angiogram
  
  

"These are common, routine cardiac tests that a doctor orders when someone is experiencing chest pain, palpitations, shortness of breath and unexplained weakness or fatigue," says Dr. Tariq Dayah, an interventional cardiologist at Houston Methodist. "They're the first step in assessing how the heart is functioning, to help confirm or rule out a potential diagnosis."

These tests are also sometimes used to screen for heart issues, or to help plan treatment for an already diagnosed heart condition, or to check whether your treatment plan is working.

Here's how each of these tests works, why they're ordered and what the results mean:

1. Electrocardiogram

"An electrocardiogram is a routine cardiac screening test that's very useful and inexpensive," says Dr. Dayah. "We use it as a baseline check of a person's heart to help diagnose symptoms like chest pain and palpitations."

It's often referred to as an ECG or, more commonly, an EKG.

What is an EKG?

An EKG, which can be performed in your doctor's office, detects the electrical activity of the heart, recording information about your heart's rhythm. An abnormal rhythm can be a sign that your heart isn't functioning properly for one reason or another.

It's just a snapshot, though — providing about six to ten seconds of information about your heart's current rhythm.

"Sometimes we need more than this, particularly when trying to diagnose symptoms that come and go," adds Dr. Dayah. "In these cases, we use continuous EKG — also called an event monitor or Holter monitoring — which records the heart's rhythm over an extended period of time."

You can think of it as a wearable EKG device, continuously recording your heart's electrical activity as you go about your typical day. Your doctor may request that you wear it anywhere from 24 to 48 hours.

What does an EKG show?

"An EKG is used to determine whether the heart's rhythm is regular or irregular," explains Dr. Dayah. "It can also help evaluate whether a blockage may be reducing blood flow to the heart."

An EKG can help diagnose:

• An irregular heart rhythm (arrhythmia), such as atrial fibrillation (AFib), atrial flutter or heart block
• Heart disease
• Heart attack (current or previous)
• Heart failure
  
  

2. Echocardiogram

"People are used to hearing the word sonogram and thinking of a baby picture taken during pregnancy, but an echocardiogram is also a sonogram — instead it's just a picture of the heart," says Dr. Dayah.

What is an echocardiogram?

Also known as a cardiac ultrasound or echo, an echocardiogram uses sound waves to create pictures of your heart.

There are two main types of echocardiogram:

• Transthoracic echocardiogram – the most common type, in which the heart is visualized from outside of the body via the vantage point of the thoracic cavity
• Transesophogeal echocardiogram – used when a more detailed image is needed, visualizes the heart from the vantage point of the esophagus
  
  

"We're able to get more accurate images through transesophageal echocardiogram, but the tradeoff is that it's more invasive," explains Dr. Dayah. "It requires us to put the person to sleep and place the ultrasound probe down the esophagus, also known as the food pipe."

The benefit is that the esophagus sits right behind the heart — meaning a transesophageal echocardiogram provides a better view.

"This level of detail isn't always needed, though" adds Dr. Dayah.

What does an echocardiogram show?

"Through an echocardiogram, we're able to visualize the heart in real time," says Dr. Dayah. "We can evaluate whether there are issues with the heart's valves, walls and muscle tissue, as well as how effectively blood is flowing."

An echocardiogram can help diagnose:

• Heart valve disease
• Structural heart defects, like adult congenital heart disease (ACHD)
• Abnormalities in heart muscle, such as cardiomyopathy
• Heart failure
• Blood clots in the heart
  
  

3. Cardiac stress test

"A stress test is a fairly simple, readily accessible test that helps assess whether the heart is functioning optimally," says Dr. Dayah.

What is a stress test?

A stress test uses an EKG to measure how the heart responds during either physical or chemical stimulation.

There are three types of cardiac stress test:

• Exercise stress test – the heart is stimulated via activity on a treadmill
• Chemical stress test – for people who cannot exercise on a treadmill, the heart is stimulated by an IV-injectable drug
• Nuclear perfusion stress test – a more sensitive analysis, the heart is stimulated through either an exercise or chemical stress test, but imaging is also performed to visualize blood flow
  
  

What does a stress test show?

"As heart rate is elevated, we're looking for changes on the EKG that indicate a blockage in arteries of the heart," says Dr. Dayah. "If a nuclear perfusion stress test is used, we're additionally looking at the imaging we obtain to determine whether a certain area isn't getting adequate blood flow."

A cardiac stress test can help diagnose:

• Coronary artery disease
• An arrhythmia (irregular heart rhythm), such as atrial fibrillation (AFib), atrial flutter or heart block
• Heart valve disease
  
  

4. Cardiac CT scan

A CT scan is a compilation of several X-ray images that are digitally combined to create a cross-section of the body part being imaged.

What is a cardiac CT scan?

"In the case of a cardiac CT scan, we're using the CT scanner to form a detailed 3D view of your heart and arteries," says Dr. Dayah.

There are two different types of cardiac CT scans:

• CT calcium score test – also referred to as a cardiac calcium CT scan or heart scan, a screening tool used to help determine a person's risk of heart disease, heart attack and stroke
• CT angiogram – also referred to as a cardiac CT scan with contrast, a noninvasive alternative to the traditional, catheter-based coronary angiogram
  
  

Both tests provide a view of your heart and arteries, but each is ordered for a different reason.

"A calcium score test is used to screen people between the age of 40 to 70 who are at increased risk for heart disease, either because they're a smoker, they have high cholesterol, they're overweight, or they have a strong family history of heart disease," explains Dr. Dayah. "A CT angiogram, on the other hand, is used for people who are experiencing unexplained chest pain but are low risk for heart disease, and there's not enough evidence to warrant performing a catheter-based diagnostic procedure yet."

What does a calcium score test show?

A calcium score test helps visualize the buildup of plaque, cholesterol-containing deposits that can clog your arteries and slow blood flow to the heart. This can increase a person's risk of heart disease and ultimately, heart attack and stroke.

"The results let us know if hard plaque buildup is present or not," says Dr. Dayah. "This helps us determine a person's risk of heart disease and can also help assess the severity of it."

Information like this helps your cardiologist determine how aggressive they need to be in preventing or treating heart disease — for instance, whether lifestyle modifications are sufficient or cholesterol medications or other tests and treatments are needed?

What does a CT angiogram show?

During a CT angiogram, IV-injected contrast dye is used to visualize the arteries that supply the heart with blood, showing any narrowing or blockages that might exist.

"It's a really helpful tool for people who are having symptoms of a blockage but are low risk for heart disease," says Dr. Dayah. "We're concerned, but not to the point that we're ready to order a more invasive test just yet."

A negative CT angiogram rules out the concern. However, if a blockage is detected, a second procedure called coronary angioplasty may be required to treat it.

5. Coronary angiogram

"A coronary angiogram is the gold standard for diagnosing a blockage in an artery supplying the heart," says Dr. Dayah. "It's an invasive test, though, so we have to have convincing evidence that blockage is likely — whether that's an abnormal stress test, EKG or CT angiogram, or the person's symptoms are severe enough."

What is an angiogram?

Similar to a CT angiogram, a traditional angiogram uses contrast dye and X-ray imaging to help visualize the coronary arteries. What's different, however, is that the dye is delivered using a catheter — a thin, flexible tube that an interventional cardiologist threads through your arteries to the specific point of interest. The procedure is performed in what's called a cardiac catheterization laboratory.

"We access the coronary artery either through an artery in the groin or, more recently, the wrist," explains Dr. Dayah. "Entering through the wrist is preferred since it reduces recovery time and risk of complications. Once the catheter is navigated to the area of concern, we inject the contrast dye and are able to visualize and assess the artery."

Since a catheter is in place, the interventional cardiologist can also take next steps if they're needed.

What does an angiogram show?

Through this detailed look at the heart arteries, a coronary angiogram helps identify whether plaque buildup has caused a narrowing of an artery, an indication of coronary artery disease. Blockages can also be seen, and the extent of the blockage can be determined.

"Since we're already in there, we can also place stents to open any blockages we might identify," adds Dr. Dayah. "So a coronary angiogram isn't just a diagnostic tool. We can provide treatment at that time, if needed."