An SVT may occur when an extra electrical pathway exists in or between some of the structures of the heart. These abnormal pathways can make the electrical impulses that control your heart rate travel in a circular pattern within the heart, causing a tachycardia. These arrhythmias can be treated, but not cured, with medications.
Cardiac Ablation
One of our Clinical Cardiac Electrophysiologists may choose to treat your arrhythmia with a non-surgical procedure called a cardiac ablation. Often, this treatment permanently resolves the arrhythmia by destroying the abnormal pathway that causes it.
A cardiac ablation is like an Electrophysiology (EP) Study. If you have not already had an EP Study, the two procedures are frequently performed one after the other. The EP Study helps identify the specific type and location of the abnormal heart rhythm. Then, in a process called mapping, a catheter (small, flexible tube – as depicted in the image to the left) is manipulated until it locates the abnormal pathway that is causing the tachycardia. At this point, an ablation is performed.
A special catheter will be used to direct energy to the abnormal pathway in the heart. Most commonly used energy is called Radiofrequency (RF). Radiofrequency energy is a form of electrical energy that causes the tissue at the tip of the catheter to heat up, permanently damaging (ablating) that small area of tissue. When the abnormal pathway is destroyed, the heart’s electrical impulses can only travel through the normal conduction pathways, and the arrhythmia is eliminated.
ENERGY SOURCES
Radiofrequency (RF)
Radiofrequency (RF) Energy is radio waves that are converted to heat to ablate and create scar tissue. It reliably achieves transmurality and is the most widely used energy source in catheter ablations. In general, elevated temperatures are needed to make sure that all layers of tissue are ablated. Traditional catheters use unipolar radiofrequency energy, which simply means that the radiofrequency energy is transmitted from a single point at the catheter’s tip.
Cryo Energy
Cryo Energy is intense cold that is used to form ice crystals within the tissue, causing the cells to die and creating scar tissue. It may be easier to make lesions using cryothermy since the cold temperatures cause tissue to stick to the catheter. In addition, cryo energy may have fewer major complications. Studies have shown cryo energy to have a much lower incidence of thrombus (clot) formation than radiofrequency energy, which suggests that cryothermy could lower the risk of a stroke. Cryo energy can be used in single point catheters or balloon catheters.
Laser Energy
Laser Energy is light waves that are converted to heat to ablate and create scar tissue. It may be a safer heat-based energy than unipolar radiofrequency energy. With laser energy, the catheter does not need to be in direct contact with tissue, which could mean it will have fewer complications than radiofrequency energy. Unlike other energy sources, contact force is not a factor in whether a laser lesion is transmural. In addition, laser energy can be adjusted when ablating tissues of varying thickness, with higher energy applied to thicker tissue and lower energy applied to thinner structures in the heart.
Other energy sources, such as Microwave and High Intensity Focused Ultrasound (HIFU), have been studied but these energy sources are not widely used in catheter ablation.
CATHETER TYPES
The design and functionality of catheters is constantly evolving. Most atrial fibrillation ablations today use single point radiofrequency energy catheters, which have a success rate—freedom from atrial fibrillation—of about 70%. It is believed that different types of catheters could have higher success rates or fewer complications. Here are the diverse types of catheters available today for atrial fibrillation catheter ablations:
Single Electrode Radiofrequency Catheters
These catheters emit radiofrequency energy from a single point at the catheter tip. To make lesions, electrophysiologists ablate one spot after another, like drawing a line by making dots one after the other. If all the dots are not connected, afib could re-enter the heart in the unablated space (gap).
Multi-Electrode Radiofrequency Catheters
These catheters have several electrodes, each of which can deliver radiofrequency energy. These catheters can ablate a larger area of tissue than single point radiofrequency energy catheters, which could decrease procedure times. In addition, multielectrode catheters may be better at making contiguous lesions (lesion lines without any gaps) than single point catheters. Finally, these catheters can also deliver superficial bipolar radiofrequency energy, which may reduce injury to deeper tissues in certain areas of the heart.
Large Tip Catheters
These catheters require higher outputs and can form larger lesions that the standard 4 mm tip catheters. Disadvantages of the 8 mm tip have included a decreased resolution of electrograms, greater catheter stiffness, and therefore decreased compliance and maneuverability.
IRRIGATED TIP CATHETERS
Closed Irrigation
In this type of catheter saline is perfused via a pump mechanism through the catheter tip, turns around within the catheter tip, and returns to the pump. This represents a closed system because no saline is infused into the blood pool
Open Irrigation
Open Irrigation overcomes the limitations of non-irrigated ablation by lowering electrode and tissue surface temperature, bringing together the efficacy of power delivery with the safety of reduced char formation.
CONTACT FORCE SENSING RADIOFREQUENCY CATHETERS
During cardiac ablation, the contact force sensing Catheter enables the measurement of catheter tip contact force and direction inside the heart. If there is not enough force or pressure, the lesion formation may not be deep enough, which would allow recurrence of arrhythmia. If there is too much pressure, complications, such as steam pops, can occur. These catheters tell our Clinical Cardiac Electrophysiologists how much pressure is being applied to the catheter and tissue.
BALLOON CATHETERS
After the balloon catheter is inserted into the left atrium, the Clinical Cardiac Electrophysiologist inflates the balloon at the tip of the catheter. Balloon catheters can ablate a larger area of tissue than single point radiofrequency catheters, which enhances the prospects that lesions will be contiguous (without gaps) and could shorten procedure times. There are balloon catheters using cryothermy, laser energy, and even radiofrequency energy.
Atrial Fibrillation Ablation
Atrial fibrillation is the most common irregular heart rhythm, affecting about 2.5 million people in the US, with more than 200,000 new cases of atrial fibrillation diagnosed each year. Atrial fibrillation is an abnormal heart rhythm originating in the upper chambers of the heart (right and left atria). Several impulses begin and spread throughout the atria, causing a rapid, irregular, and disorganized heartbeat.
Ablation is proving to be successful for many patients with atrial fibrillation. The procedure is indicated for those:
• With a history of chronic, persistent, or paroxysmal atrial fibrillation
• Those who have failed antiarrhythmic drugs
• Those who have had complications from antiarrhythmic drugs
ABLATION TECHNIQUES
Pulmonary Vein Isolation (PVI)
is a minimally invasive procedure in which a flexible catheter is inserted into the heart via a vein in the leg to electrically isolate the pulmonary veins from the rest of the heart. In majority of patients this procedure can eliminate or significantly reduce the severity and frequency of atrial fibrillation episodes.
Please note that not all patients may be appropriate candidates for catheter ablation of atrial fibrillation. A thorough evaluation and pre-testing will be conducted to see if this procedure is appropriate.
Electrophysiology Study
Several tests are performed at our Southwest Cardiovascular Interventional Center (SWCVIC)
Ambulatory Surgical Center by one of our Clinical Cardiac Electrophysiologists collaborating with a team of highly skilled nurses and technicians. These tests help pinpoint the location, the type of arrhythmia, and how the arrhythmia responds to treatment. The results from the EP Study will be used by your Clinical Cardiac Electrophysiologist to study your heart’s electrical function and locate sites inside your heart that may be causing abnormal heart rhythms.
During the Electrophysiology Study, the patient is sedated, and small catheters are guided to the heart. The heart’s rhythm is recorded as tiny amounts of electricity is delivered through the catheter. This internal recording is often compared with an external recording (from electrodes placed on the patient’s chest and back) taken at the same time.
Left Atrial Appendage Closure Devices
Atrial fibrillation can cause blood to stagnate and form clots in a sac-like structure called left atrial appendage. If a clot forms, it can increase your chances of having a stroke. Oral anticoagulants (blood thinners) are recommended to prevent a stroke in patients with atrial fibrillation. If a patient does not want to take blood thinners or has contraindications/bleeding problems with blood thinners, then a left atrial occlusion device may be considered.
The idea is to occlude the left atrial appendage so that blood clots cannot exit the appendage and so the stroke risk is reduced without taking blood thinners.
Currently, the two types of left atrial appendage occlusion procedures are the WATCHMAN Implant Device (as depicted in the image provided to the left) and the LARIAT Procedure (as depicted in the image provided to the right).
The Watchman Implant Device is umbrella mesh-like device that can be placed at the opening of left atrial appendage. Using standard techniques, like ones used in atrial fibrillation ablation procedure, the Watchman Implant Device is guided into the heart through a flexible tube inserted through a vein in your upper leg. The Clinical Cardiac Electrophysiologist measures the size of the left atrial appendage to determine which size Watchman Implant Device to use. Then the Clinical Cardiac Electrophysiologist deploys the Watchman Implant Device at the left atrial appendage. Testing and additional pictures are taken to make sure that the device is seated correctly.
Lariat Procedure
The LARIAT Suture Delivery Device is a suture-based device used to occlude left atrial appendage. By means of standard techniques, like ones used in left atrial ablation procedure, a magnetic wire is placed inside of the left atrial appendage. Then, via a percutaneous epicardial approach, a second magnetic wire is placed in the sac of the heart (pericardial space) from outside by doing a tiny puncture below the breastbone. This second wire then finds the first magnetic wire in the Left Atrial Appendage (LAA). Next, over this magnetic wire bridge, a LARIAT suture is inserted over the wire in the pericardial space to find the LAA and snare it, resulting in necrosis of the LAA. Following the procedure, the only thing that remains in the body is a suture ligating the LAA.
DC Cardioversion
Cardioversion is a procedure used to convert an irregular or abnormal heart rhythm to a normal heart rhythm by applying high energy shock. Common rhythms that may require elective cardioversion include atrial fibrillation, atrial flutter, and ventricular tachycardia.
Cardiopulmonary Stress Test (CPX)
Cardiopulmonary exercise testing, often abbreviated as CPX, CPEX or CPET, is now the ‘gold standard’ objective tool for the evaluation of cardiopulmonary function and fitness. It is an entirely non-invasive and objective method of assessing integrative exercise responses involving the pulmonary, cardiovascular, and skeletal muscle systems, which are not reflected through the measurement of individual organ system function. Therefore, a CPX or CPET evaluates the way in which your heart, lungs and circulation simultaneously respond to exercise.
Pacemaker Implantation
A pacemaker is a small electronic device that helps the heart to beat at a proper rate. It keeps track of your normal heartbeat and can sense when it becomes too slow. When that happens, the pacemaker generates a small electrical impulse, like the heart’s natural impulse. This keeps your heart beating at a normal pace.
Your pacemaker has two main parts: the Pulse Generator (the Pulse Generator has been depicted in red in the image to the left) and the Pacing Lead(s) (the Pacing Leads have been depicted in blue in the image to the left). The Pulse Generator is a small, flat, lightweight metal case that contains a tiny computer and battery. This is the part that generates the electrical impulses. The Pacing Leads are wires covered by soft, flexible plastic. Working together to regulate your heart, they monitor how well the heart is beating and will send electrical impulses from the Pulse Generator to the heart when it senses it is necessary.
Defibrillation Implantation
Ordinarily, your heart beats at a regular, steady pace called a normal sinus rhythm. It is regulated electrically by the sinus node. However, if certain cells in the lower chamber of your heart (the ventricles) begin to generate their own electrical impulses, these can override the heart’s normal electrical control mechanism. These impulses do not follow the heart’s normal conduction pathway and may prevent the heart from pumping enough blood and oxygen through the body. One situation, called Ventricular Tachycardia (VT), may cause you to feel fluttering in the chest or throat or a sensation of dizziness and lightheadedness. Because less blood is pumped with each beat, your body and brain receive less oxygen-carrying blood, which may result in dizziness, blackouts, or fainting, and even unconsciousness. Sometimes VT can be prevented or treated with medications. In other cases, an electrical device is needed to deliver an impulse to the heart to stop the arrhythmia.
When the Ventricular Arrhythmia becomes even more rapid and unstable, it causes a condition called Ventricular Fibrillation (VF). This is a serious condition when the heart is quivering, and no longer pumps any blood, this can lead to a cardiac arrest. The only way to correct Ventricular Fibrillation is to quickly deliver a strong electrical shock to the heart to stop the abnormal rhythm and prompt the heart’s normal electrical conduction system to take over again. This process is called defibrillation.
YOUR IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR (ICD)
When emergencies cause life-threatening arrhythmias, and a patient is being rushed to a hospital in an ambulance or is at a medical facility, defibrillation is done with an external device called a defibrillator. Paddles are placed against the chest, and a strong electrical impulse is delivered through the heart. However, if your arrhythmia (either Ventricular Tachycardia or Fibrillation) occurs in routine situations, an automatic Implantable Cardioverter-Defibrillator (ICD) can be implanted to monitor and deliver whatever therapy is necessary. It will be programmed to detect and diagnose either Ventricular Tachycardia or Ventricular Fibrillation and will deliver the therapy necessary to correct your abnormal heart rhythms.
One of our Clinical Cardiac Electrophysiologist may choose to implant a defibrillator in your body to monitor your heart rhythm around the clock and to immediately correct any dangerous arrhythmias should they occur.
The ICD has two components: the Generator (the Generator has been depicted in red in the image to above) and the Pacing Lead(s) (the Pacing Leads have been depicted in blue in the image above). The Generator is a small, flat, lightweight case that holds a tiny computer and battery. This will generate the electrical impulses used to regulate your heartbeat. The Pacing Leads are wires covered with soft, flexible plastic. They are connected to the generator and “tell” it how the heart is beating. The Pacing Leads also transmit the electrical impulses from the Generator to the heart.
Laser Lead Extraction
Our Clinical Cardiac Electrophysiologists at Southwest Cardiovascular Interventional Center (SWCVIC)
Ambulatory Surgical Center specialize in removing leads (pacemaker and/or defibrillator wires attached to the heart) by minimally invasive procedure called as laser lead extraction. The procedure involves use of laser sheaths that breaks up the scar tissue built around leads (as depicted in the image to the left). The procedure is minimally invasive and requires considerable operator expertise. One of our Clinical Cardiac Electrophysiologists will discuss all the options with you and your family before scheduling the procedure.
Cardiac Resynchronization
Heart failure is a common and serious medical condition. Heart failure develops slowly over time as your heart muscle gradually weakens. The “failure” refers to your heart’s inability to pump enough blood to meet your body’s needs. Congestive heart failure is a progressive condition in which the heart’s function gradually deteriorates resulting in diminished cardiac performance and pumping ability. Blood flow to the organs is reduced, leading to a variety of symptoms including shortness of breath, lack of energy, swelling, etc. Patients with heart failure often require repeated hospitalizations for treatment and adjustment of medications. Medications have been the mainstay of therapy for heart failure. However, patients with extreme forms of heart failure often remain highly symptomatic despite maximum medical therapy and face grave risk.
Contact Southwest Cardiovascular Interventional Center (SWCVIC) Ambulatory Surgical Center (ASC) today by Clicking Here to setup a consultation with one of our Clinical Cardiac Electrophysiologists if you or your family have any questions or concerns regarding your cardiac health. We are here to help you improve your cardiac health for a better and healthier tomorrow!