How is heart block diagnosed?
Heart blocks can be diagnosed with a test called an electrocardiogram (ECG), which measures the heart's electrical activity. Heart blocks have a certain pattern, which the ECG machine records. In some instances, a special test called an
electrophysiologic study (EPS) uses probes placed into the heart to measure the flow and direction of electricity. A test called a Holter monitor can also diagnose the problem.
Symptoms associated with heart block depend upon the severity of the conduction disturbance and range from a complete lack of symptoms to syncope (fainting) and life-threatening collapse. For patients with intermittent heart block, symptoms can be more subtle and the diagnosis therefore less straightforward. Symptoms might include fatigue, breathlessness, palpitations, activity intolerance and intermittent lightheadedness without syncope. The diagnosis can be straightforward if the AV block is persistent and/or symptoms present during an evaluation while ECG is being recorded. Frequently, however, both the symptoms and the conduction disturbance occur intermittently, and in these cases an ambulatory ECG monitor (e.g., Holter monitor) might assist in recording the heart rhythm at the time symptoms are experienced.
Invasive electrophysiologic testing, a type of cardiac catheterization, is an invasive technique during which the electrical system of the heart is examined with small electrical catheters, and is sometimes used to evaluate the conduction system in a patient with suspected heart block. A newly available device called an implantable loop recorder (ILR) is also sometimes used to assist in making the diagnosis in a patient with a suspected bradyarrhythmia who has escaped diagnosis by traditional means. It is a very small electronic device that rests under the skin of the chest, monitors the ECG continuously, and makes and stores recordings during detected episodes of abnormal heart rhythm.