Understanding a few basics about how your heart works can be an important part of managing dilated cardiomyopathy (DCM) and help you feel more confident and involved in your care. Heart function tests help your care team evaluate the heart’s structure, pumping ability, rhythm, and monitor changes over time.
Knowing what these tests measure (and why they matter) can help you better understand your condition and take an active role in decisions about your care.
Ejection Fraction (EF)
Ejection fraction (EF) measures the percentage of blood the left ventricle pumps out with each contraction. It is a measure of how well the heart is contracting.
EF Ranges:
- Normal EF: 50–65%
- Borderline or mildly reduced EF: (41–49%)
- Reduced EF: 40% and less
Why it matters:
- EF is a key indicator, but it’s only one part of the story. Your symptoms, lifestyle, and other test results are just as important for your care team to see the full picture.
- EF does not always match how you feel day-to-day — some people with low EF feel fine, while others with normal or near normal EF may notice fatigue or shortness of breath.
How it’s measured:
- Echocardiogram (Echo): Most common method; uses ultrasound to see heart chambers and calculate EF.
- Cardiac MRI: Provides a highly detailed view of the heart structure and tissue.
Other tests: CT scans or angiograms can provide additional information about heart structure.
Heart Imaging Tests
Heart imaging tests provide a visual understanding of the heart’s size, structure, and function.
Common imaging tests include:
- CT scan / Coronary Angiogram:
Evaluates coronary arteries and heart structure; often used to rule out blockages or identify structural abnormalities. - Echocardiogram (Echo):
Measures chamber size, wall thickness, valve function, and EF. This non-invasive test (like a pregnancy ultrasound) is essential for diagnosing and monitoring DCM over time. - Cardiac MRI:
Provides detailed imaging of the heart muscle and tissue; especially helpful for identifying scarring, inflammation, or prior injury. - Chest X-ray:
Can show heart enlargement or fluid in the lungs.
Heart Rhythm Tests
DCM increases the risk of arrhythmias (abnormal heart rhythms). Rhythm tests help detect electrical changes in the heart.
- Electrocardiogram (EKG / ECG):
Measures the heart’s electrical activity and can detect arrhythmias, heart block, or signs of prior heart injury. - Holter Monitor:
A portable EKG that is worn for 24–48 hours to capture intermittent rhythm changes. - Event Monitor:
Worn for weeks; records heart rhythm when symptoms occur. - Implantable Loop Recorder:
A small device placed under the skin for long-term rhythm monitoring when symptoms are infrequent or unexplained.
Blood Tests
Blood tests provide important information about how your heart is functioning and how your body is responding to DCM and treatment.
- BNP / NT-proBNP:
Hormones released when the heart is under stress; help detect heart failure or monitor worsening symptoms. Higher levels often correlate with more fluid retention or ‘stretch’ in the heart muscle. - Troponin:
Indicates recent heart muscle injury. - Kidney & Liver Function, Electrolytes:
Important for monitoring the effects of heart failure and medications.
Exercise & Stress Testing
Exercise testing shows how your heart performs under physical stress – information that may not be visible when you’re at rest.
Types of Tests:
- Stress Test / Treadmill Test:
Evaluates how your heart responds to physical activity and may identify problems that may not appear at rest. - Cardiopulmonary Exercise Test (CPET):
Measures oxygen use and functional capacity; often used in advanced heart failure evaluation.
Why it matters:
- Provides an objective measure of your exercise tolerance.
- Helps guide safe activity levels, treatment decisions, and therapy planning.
Patient Tips
- Bring an up-to-date list of all medications and supplements to every test.
- Keep track of your baseline heart rate, blood pressure, and symptoms.
- Ask your care team to explain test results in plain language.