The heart is a continuously working organ, and medical professionals use a variety of tests to assess its condition, function, and electrical stability. These diagnostic procedures determine the cause of symptoms, monitor treatment effectiveness, and evaluate the risk of future cardiac events. Tests range from simple, non-invasive recordings of electrical signals to advanced imaging and procedures that require temporary entry into the body. Each test provides a unique view into heart health, contributing to a comprehensive understanding of a patient’s cardiovascular status.
Tests That Measure Electrical Activity
The heart’s rhythm is governed by a precise electrical system, and the primary tool for measuring this activity is the Electrocardiogram (ECG or EKG). This non-invasive test uses electrodes placed on the skin to detect and record the small electrical changes that occur during each heartbeat, typically over about ten seconds. An ECG provides information on the heart rate, rhythm regularity, and the strength and timing of electrical impulses. Changes in the pattern can suggest various cardiac conditions, including previous heart attacks, issues with blood flow, or an enlarged heart.
Since many heart rhythm problems (arrhythmias) are intermittent and may not occur during a brief, standard ECG, doctors often use ambulatory monitoring devices. A Holter monitor is a small, portable device worn for 24 to 48 hours that continuously records every heartbeat as a patient goes about daily activities. This extended recording period increases the chance of capturing irregular heartbeats that a brief resting ECG might miss.
For less frequent symptoms, a cardiac event recorder is used, which can be worn for several weeks. Unlike the continuous Holter monitor, an event recorder generally only records electrical activity when the patient manually activates it upon feeling symptoms like palpitations or dizziness. Some advanced recorders save data from a few minutes before activation, capturing the rhythm leading up to the symptom. An implantable loop recorder, a small device placed under the skin, can monitor the heart’s rhythm for several years, which is beneficial for very rare or unexplained symptoms.
Imaging Tests That Show Structure and Function
Medical imaging provides visual information about the physical condition of the heart muscle, valves, and surrounding blood vessels. The Echocardiogram (echo) uses high-frequency sound waves (ultrasound) to create real-time moving images of the heart. This test is effective for evaluating heart valve function, assessing how well the heart muscle pumps blood, and measuring the size and shape of the heart chambers. Doppler echocardiography is often included to measure the speed and direction of blood flow through the chambers and valves.
Cardiac Computed Tomography (CT) scans use X-rays and computer processing to produce detailed cross-sectional or three-dimensional images of the heart. A common application is Coronary CT Angiography, where a contrast dye is injected to visualize the coronary arteries and detect blockages or narrowing caused by plaque buildup. The Coronary Calcium Scan uses a standard CT scan without dye to measure the amount of calcium in the coronary arteries, which predicts future cardiac events.
Cardiac Magnetic Resonance Imaging (MRI) employs strong magnetic fields and radio waves to generate highly detailed pictures of the heart’s anatomy and tissue characteristics. Unlike CT, MRI does not use ionizing radiation. It is the standard for accurately measuring the volume of the heart chambers and the ejection fraction (the percentage of blood pumped out with each beat). Cardiac MRI is superior for identifying scar tissue within the heart muscle, often resulting from a past heart attack, and for evaluating heart inflammation.
Procedures That Assess Performance Under Stress
Stress testing evaluates how the heart performs when it is forced to work harder, revealing problems not apparent at rest. The most common method involves controlled physical exertion, typically walking on a treadmill or cycling, while continuously monitoring the heart’s electrical activity. This approach works because diseased arteries may supply enough blood at rest but fail to meet the increased demand during exercise, causing symptoms or ECG changes.
For individuals unable to exercise, a Pharmacological Stress Test is performed. A medication, such as adenosine or dobutamine, is administered intravenously to mimic exertion by increasing the heart rate or dilating blood vessels, simulating the stress response. Stress tests often incorporate imaging techniques to enhance diagnostic accuracy.
A Stress Echocardiogram captures ultrasound images of the heart immediately before and after peak stress to look for new abnormalities in heart wall movement, indicating insufficient blood flow. A Nuclear Stress Test involves injecting a small amount of a radioactive tracer, which is then imaged at rest and after stress. Areas of the heart muscle receiving adequate blood flow absorb the tracer and appear brightly on the scan, while areas with poor blood flow appear less bright, pinpointing blockages in the coronary arteries.
Invasive Diagnostic Procedures
Invasive procedures are reserved for when non-invasive tests do not provide sufficient detail or when a high-risk condition is strongly suspected. Cardiac Catheterization involves inserting a long, thin, flexible tube called a catheter into a blood vessel, usually in the wrist or groin. The catheter is guided using X-ray images into the heart chambers and coronary arteries.
The most common application is Coronary Angiography, which focuses on the arteries that supply the heart muscle. During angiography, a contrast dye is injected through the catheter, making the coronary arteries visible on X-ray images (angiograms). This technique is the standard for precisely identifying the location and severity of blockages or narrowing in the coronary arteries.
Cardiac catheterization also allows for the direct measurement of pressures within the heart chambers and major blood vessels. This pressure data is valuable for evaluating heart valve function and determining the severity of conditions like heart failure. While considered higher risk than non-invasive testing, these procedures provide the most accurate internal information and can often be immediately converted into therapeutic interventions, such as angioplasty and stent placement, to treat identified blockages.