Overview of Electrophysiologic Study Indications and Evaluation
An Electrophysiology (EP) study is a type of heart procedure that doctors use to study and treat certain types of irregular heartbeats, known as arrhythmias. This procedure is done by inserting a small tube through the skin and into the heart. Once the tube is in place, doctors can study the way electricity flows through the heart. This information helps them understand how each part of the heart’s electrical system is working, where the arrhythmia is coming from, and how severe it is.
The main goals of doing an EP study are to see how well each part of the heart’s electrical system is working, find the exact spot where the arrhythmia is starting, determine the patient’s risk of future heart problems, and figure out what type of treatment or therapy they might need. For example, the doctor might decide to use a procedure called ablation to destroy the area of the heart that is causing the arrhythmia.
This article provides a general overview of EP studies, including the structure and function of the heart, the reasons why someone might need one, and their clinical importance in treating common heart problems.
Anatomy and Physiology of Electrophysiologic Study Indications and Evaluation
The heart’s electrical system includes special heart muscle cells and fibers that create and spread electrical signals. These signals start the heartbeat and help the four chambers of the heart to beat in sync. A specific heart study, known as an EP study, involves inserting special electrode catheters in the heart. This is typically done on the right side of the heart. These catheters generate electrical signals that help doctors understand the heart’s rhythms.
These electrodes can capture something called intracardiac electrograms (EGMs). In simple words, these are signals that are recorded within the heart and represent the electrical activity of the heart structures close to the recording electrode. For instance, the EGMs from the atrial (HRE) and ventricular(RVA/LV) catheters represent the electrical activity of the heart’s upper and lower chambers, respectively. The recordings also include information from what is called the his bundle (HBE) which is a part of the heart’s electrical system. The carotid sinus (CS) involves both the atrium and ventricles’ EGMs, with the atrial wave usually bigger and the ventricular waves smaller.
The readings during the EP study can be viewed using the labels displayed along the side of the reading. This helps one understand and relate the electrical activity with that seen on a regular ECG.
During this study, the electrode catheters are placed in different areas of the heart such as the high right atrium (HRA) which captures the electrical impulses from the natural pacemaker of the heart, the SA node. Another electrode is placed at the anterior tricuspid valve annulus (HBE) that records electrical impulses from the bundle of his, essentially a part of the hearts electrical system. A third one is placed in the right ventricle (RVA) to record from the lower tip of the heart. The coronary sinus (CS 1-8) records activity from the left atrium as it runs along the heart valve.
The study consists of five parts: measuring basic/foundational intervals, slow ventricular pacing, slow atrial pacing, additional atrial stimulus test, and extra ventricular stimulus test. This information is used to understand how well the heart’s electrical system is functioning.
Understanding the anatomy and function of the heart’s electrical system is important in diagnosing and treating heart conditions. The data from these studies helps physicians identify any irregularities in the heart’s rhythms and can provide important information to determine the best course of action for treatment.
Why do People Need Electrophysiologic Study Indications and Evaluation
If you have certain heart conditions, your doctor may suggest a form of testing called ‘electrophysiologic studies’ or EP studies. These help your doctor understand how electric signals move through your heart, which can be essential in identifying what’s causing a heart problem and figuring out the best treatment. Here, we’ll talk about why electrophysiologic studies might be needed for some common heart conditions:
Sinus node dysfunction: The sinus node is the heart’s natural pacemaker. It’s responsible for regulating the heart’s rhythm. If the sinus node is not working properly, it can cause several different issues, including slow heart rate (sinus bradycardia), heartbeat pause (sinus arrest), heartbeat block (sinoatrial block), and other conditions where the heart is not able to speed up as it should during exercise (chronotropic incompetence).
EP studies can be useful in diagnosing sinus node dysfunction but they’re not always necessary. They’re typically used when other, less invasive tests like exercise stress tests or monitoring devices were unable to provide a clear diagnosis or show a clear connection between the symptoms and a slow heart rate. EP studies can be also used to determine if the sinus node disease is a result of medication side effects or a problem with the autonomic nervous system, which controls involuntary body functions.
EP studies, however, are usually not used before putting a pacemaker in because they do not help guide the pacemaker placement. Also, putting a pacemaker in for a slow heart rate hasn’t been proven to help people live longer.
Acquired AV block: This is a condition where the electrical signals between the upper and lower chambers of the heart are blocked. Pacemakers can help improve symptoms in people with a complete block. Patients with a mild degree of block usually do not need a pacemaker, while those with more severe block may need one, even without an EP study. EP studies are generally used when other tests cannot pinpoint where the block is occurring.
Bundle branch block or intraventricular conduction delay: These are conditions where the electrical signals in the heart are slowed down or blocked. These conditions put people at a risk of developing a complete block. Patients who are at risk of their heart problem worsening could benefit from getting a pacemaker. An EP study may be used to identify these at-risk patients. This type of testing is especially beneficial for patients experiencing unexplained fainting. However, these tests are not normally performed in patients who have no symptoms.
Narrow QRS complex tachycardia: This term refers to rapid heart rhythms that originate in the upper chambers (atria) of the heart. These are heart rates faster than 100 beats per minute with a specific pattern on the EKG reading (QRS less than 120ms). Sometimes, the cause of these heart rates cannot be determined with non-invasive tests and an EP study can help find the cause and guide treatment, often involving catheter ablation.
Wide QRS complex tachycardia: These are rapid heart rhythms that originate in the lower chambers (ventricles) of the heart. They result in wider EKG readings (QRS more than 120ms). These conditions include ventricular tachycardia and certain other rapid heart rates originating from the atria or junctions between the atria and ventricles.
When a Person Should Avoid Electrophysiologic Study Indications and Evaluation
There are certain situations in which a heart test known as an electrophysiology study can’t be done:
If a person has a blood infection or sepsis, a severe condition that occurs when the body’s response to an infection causes injury to its own tissues and organs, the study can’t be carried out.
People suffering from a sudden and severe worsening of heart failure not caused by an irregular heartbeat (arrhythmia) also can’t undergo this study, because it might actually trigger an arrhythmia.
If there’s an increased risk of severe bleeding, for instance due to an extremely high INR (a measure of how fast the blood clots) or DIC (a condition that leads to small blood clots throughout the body), the study would be too risky.
Lastly, it can’t be done if there’s an infection or blood clot at the site where doctors would need to insert a tube for the study. This could be, for example, a blood clot in a large vein in the leg (femoral DVT) or an inflammation of the skin and underlying tissues in the lower leg (cellulitis).
Possible Complications of Electrophysiologic Study Indications and Evaluation
Just like with any procedure that involves piercing the skin, there are certain risks involved. These risks may include damaging a blood vessel, severe bleeding that needs a blood transfusion, an infection from where they put the catheter in, heart attack, stroke, and even death due to poor blood flow and related problems. Conducting an electrophysiology (EP) study also carries certain risks. In an EP study, multiple electrodes (small devices that transfer electrical currents) are placed at different points in the heart. This could potentially lead to damage to important parts of the heart such as the tricuspid valve, which helps manage blood flow in the heart, or the walls of the heart’s chambers. If the heart chambers were to be punctured, this could lead to a condition called cardiac tamponade that could potentially be fatal. This condition occurs when the heart can’t pump properly due to buildup of fluid or blood around it.
What Else Should I Know About Electrophysiologic Study Indications and Evaluation?
An electrophysiology study is a medical test that can help doctors understand if a patient is at risk for certain heart diseases. Also, it can precisely diagnose issues affecting the heart’s electrical system.
Diagnostic Uses
a) This test becomes necessary when patients faint without any known heart rhythm disorders or in people with heart conditions such as ischemic heart disease, sinus node dysfunction (the heart’s natural pacemaker not working properly), or sinus bradycardia (slow heart rate). It can also be used for people who have a blockage in two of the three pathways that distribute electrical impulses to the heart (bifascicular block), experience heart palpitations, or work in high-risk jobs like driving or air traffic control.
b) Doctors use the electrophysiology study when a patient suffers from a fast heart rate (tachycardia) involving wide electrical waves in the heart, and non-invasive testing is not conclusive.
c) If someone survives a cardiac arrest (heart suddenly stopping), this test can be a part of the diagnostic investigation.
Risk Stratification Uses
a) This test is used to prevent sudden cardiac death in people with heart disease, abnormalities in the heart’s electrical signals (AV conduction abnormalities), young patients showing early symptoms of dangerous heart rhythm disorders (pre-excitation syndromes), and inherited heart disorders. It’s also used for individuals with acquired disorders like sarcoidosis (an inflammatory disease that can affect the heart) and amyloidosis (a rare disease causing abnormal protein buildup).
