Electrical Activity Heart Tests

Multiple open-heart surgeries, in combination with single ventricle heart disease, can lead to scarring within the heart. The scarring can cause rhythm and electrical abnormalities in Fontan patients. Some patients will need a pacemaker that generates a low-energy electrical pulse to prompt the heart to beat at a normal rate. The clinic will evaluate the heart’s rhythm using these screening tests:

  • An Electrocardiogram (EKG or ECG)

    An ECG translates the heart’s electrical activity into line tracings on paper giving information on heart rhythm and condition.
  • 24-hour Holter monitor

    Electrodes (small electricity-conducting patches) are stuck onto a patient’s chest and attached to a small recording monitor. The battery-operated monitor is carried in a pocket or small pouch worn around the patient’s neck or waist.
    • The monitor records the heart’s electrical activity.
    • Patients keep a diary of activities performed while wearing the monitor, noting how they feel.
    • After 24-48 hours, patients will return the monitor to the clinic.
    • A physician at the clinic will look at the recordings for any abnormal heart rhythms.
  • Pacemaker testing

Heart Failure Test

B-Type Natriuretic Peptide (BNP) is a substance secreted from the lower chambers of the heart (ventricles) that is caused by increased pressure from developing or worsening heart failure. We will check the BNP with a blood test.

Exercise Stress Test

An exercise stress test is an excellent way of monitoring heart performance and is a screening tool used to test the effects of exercise on the heart. To conduct the test, a patient walks on a treadmill or pedals an exercise bicycle. The patient will begin at a slow pace and will then be asked to walk or pedal faster and/or on an incline. During the test, the patient’s breathing, exhaled gases, electrocardiogram, blood pressure, and oxygen saturation will be monitored by an exercise technician. An exercise stress test can be a valuable tool to monitor and record changes in the performance of a patient’s heart over many years.

Cardiac Catheterization

Cardiac catheterization is a procedure in which a catheter (a thin flexible tube) is passed into either side of the heart by way of a blood vessel in the groin, neck, or arm. Most patients have had catheterization procedures as part of their previous evaluations. Cardiac catheterization is the only way to precisely measure pressures within the Fontan circulation and lung arteries. High Fontan pressures may indicate problems with the lung or heart function and may require additional investigation and treatment. Cardiac catheterization may also allow transcatheter interventions that can improve blood flow or heart function without surgery.

Cardiac MRI and CT Scans

Cardiac MRI uses radio waves, magnets, and a computer to create both still and moving pictures of the heart and blood vessels. Compared to echocardiograms, which are limited by the penetration of sound waves, cardiac MRI provides more detailed pictures of the beating heart and blood vessels in order to evaluate structure and function. Unlike CT scans, an MRI doesn’t use ionizing radiation, so it doesn’t increase the risk for cancer. Cardiac MRI is the only noninvasive imaging test that can differentiate healthy heart muscle tissue from dead or non-healthy tissue, while also providing valuable insight into heart function and determining if there is any narrowing in the arteries and veins. In patients with a pacemaker, ICD, or other metal implants, an MRI may not be recommended. These patients may undergo a CT scan instead.