By Michael Springer MD FACC FHRS
The heart is like an engine. It has mechanical parts, fuel lines and an electrical system. The heart muscle and valves are the mechanical parts. The coronary arteries bring blood (fuel) to the muscle. The electrical system of the heart produces electrical currents that cause each heartbeat. The electrical system has cells that act as the pacemaker cells telling the heart how many times per minute to beat and cells that act as wires to help the current flow through the heart in proper order. The current causes the muscle cells to contract producing a pumping action.
When the electrical system of the heart malfunctions, it can produce abnormal heart rhythms called “arrhythmias.” Some of these arrhythmias produce few symptoms, are not dangerous and do not require treatment. Some are dangerous and require therapy. Some are not dangerous but produce symptoms.
The first step in evaluating an arrhythmia is to perform simple testing such as an EKG (electrocardiogram) and echocardiogram, an ultrasound picture of the heart. Usually these two tests along with a proper history and physical exam can determine whether an arrhythmia is dangerous. Most dangerous heart arrhythmias occur in people with additional heart conditions and weak heart muscle, such as may occur after a heart attack.
Many patients with no other heart disease will develop arrhythmias that produce symptoms. Most are not dangerous, but can produce severe symptoms such as dizziness or lightheadedness, fainting, shortness of breath and palpitations. These can be treated with medication or a procedure called catheter ablation. Medication is used to suppress the arrhythmia but must be taken every day and usually two to three times per day. Ablation is a curative procedure that cures the problem so no medication is required.
The most common arrhythmia treated with ablation is called SVT or supraventricular tachycardia. That means a fast heart rate coming from above the ventricles. The patient is placed on a procedure table and the skin over the femoral vein at the top of the thigh is cleaned with an antiseptic. Sterile drapes are placed over the patient. Intravenous sedation is given to relax the patient and lidocaine is injected as a local anesthetic over the femoral vein.
Two or three small tubes (sheaths) are placed into the vein and small catheters are placed through these to the right side of the heart where different parts of the electrical conduction system can be measured. These catheters not only record but can also pace the heart. Small electrical currents are delivered to the heart to produce paced beats. These paced beats are used to trigger the abnormal circuit responsible for the SVT. Then the catheters are used to map out the circuit. Finally, a catheter is used to deliver radiofrequency current (RF) to a part of the circuit to cauterize it and fix the problem.
FAQ’s about catheter ablation:
1. Does it hurt? Injecting the local anesthetic can sting but IV sedation is used to minimize discomfort. During RF delivery pain can occur so IV sedation is again used.
2. Does it work? Depending on the circuit, success rates are at least 95% for most SVT.
3. Is it risky? No procedure has zero risk. The risk of catheter ablation depends on where the circuit is located. 60% of the circuits are close to the normal conduction system. With these there is a 1% chance of damage to the normal system that may require a pacemaker. Less commonly, circuits are in the left atrium. Any work on the left side of the heart includes a risk of stroke because the blood from the left heart goes to the head and body. This risk is very low, much less than 1%, but not zero. There are other uncommon side effects that are not usually serious.
4. What is the recovery time? Procedures done in the morning usually permit patients to go home the same day. Strenuous exertion should be avoided for one week.
5. What about atrial fibrillation? Afib ablations are a special category. These procedures require more catheters, more time, general anesthesia and have unique risks. They can be very effective for patients with symptomatic afib not responding to at least two drugs.
Ablation is very effective at curing many types of arrhythmia without requiring long term drug use. These procedures should be discussed with an electrophysiologist before making any decisions.
Image from: http://we-help-each-other.org/heart-ablation/
Michael Springer MD FACC FHRS, is the Medical Director of Cardiac Electrophysiology Lab at Jewish Hospital, part of KentuckyOne Health. For more information, you can contact Dr. Springer at 502. 585-4321 or www.KentuckyOneHealth.org.