The evaluation of a third degree heart block begins with a history and physical examination.

Physical findings in someone with a third degree heart block may include:

• Slow pulse
• Low blood pressure

Tests are necessary to make the diagnosis of a third degree heart block.

Tests that may be used to evaluate a third degree heart block include:

• Electrocardiogram
• This test can show the heart rhythm, rate, and signs of a heart attack
• Electrolyte profile
• Kidney profile
• Cardiac enzymes
• Cardiac monitoring
• Chest x-ray: may be normal, or show an enlarged heart
• Normal chest x-rays
• Enlarged heart on x-ray
• Cardiac catheterization
• Dye is injected into the coronary arteries.
• Cardiac stress test:
• An ECG is performed before, during, and after a prolonged period exercise on a treadmill to study its effect on the heart tracing.
• Echocardiogram:
• A test that uses sound waves to form images of the inside of the heart
• MRI scan of the heart:
• Shows detailed images of the heart and coronary arteries
• Detects structural abnormalities of the heart
• SPECT scanning of the heart:
• Detects blood flow abnormalities to heart muscle
• Thallium heart scan
• Coronary artery CT scanning:
• Checks for possible obstructions in the coronary arteries
• Can show a build-up of calcium in a coronary artery
• MUGA scan
• Intracardiac electrophysiologic study:
• The heart is stimulated with tiny electrical currents in order to find the cause of an arrhythmia