Percutaneous cardiac ablation
Preparing for the ablation
Most electrophysiologists need a few weeks notice to schedule an ablation depending on their schedule and the special equipment needed. Almost all ablations are elective procedures. Patients should therefore notify their doctor immediately if their health changes in any way before their schedule ablation procedure. Early notification might allow the doctor to schedule another patient who is waiting rather than waste the time.
Certain medications may need to be stopped before the ablation. Blood thinning medications are usually stopped before and ablation (usually not for Afib ablations). Antiarrhythmics are stopped days to a few weeks before the procedure. Typical instructions include making the patient NPO after midnight the night before the procedure. Our practice involves asking the patient to take their normal morning medications with a sip of water except that oral hypoglycemics are not given. Because the patient is NPO, only half of the normal dose of insulin is given in patients with diabetes.
Prepping the patient
Patients must show up at the hospital several hours before the procedure. Screening blood tests are drawn (unless they have already been done before the day of the procedure). An IV is started and informed consent for the procedure is obtained. The patient is then transported to the EP laboratory where the procedure will be done. There the patient is moved onto the fluoro bed and connected to the ECG wires. In this way, the rhythm can be monitored throughout the procedure. Defibrillation patches are applied to the chest wall in case the patient needs to be cardioverted. In some patients a Foley catheter is inserted. Next the groin and/or clavicular areas where the IV sheaths will be inserted are shaved and prepped. Sterile drapes are applied.
Sedation for the procedure
The average ablation procedure at our institution takes 3 hours. Some ablations are completed in less than 2 hours while others last 6 hours or longer. The only discomfort from an ablation is local anesthesia for insertion of the IV sheaths. Minor discomfort sometimes occurs if radiofrequency energy is used as the ablation source. Cryo energy causes no patient discomfort at all. Because it is very difficult to ask an unsedated patient to hold still on the fluoro table, our patients are attended by an anesthesia provider who provides deep sedation or general anesthesia for the procedure. Usually the patient stays asleep for the entire procedure, but occasionally with the patient asleep, the arrhythmia cannot be induced, and the patient must then be allowed to wake up partially. Most of our patients do not remember the procedure and have therefore an acceptable experience.
Risks of ablation
Major complications include death, stroke, and accidental damage to the AV node resulting in complete heart block requiring a permanent pacemaker, perforation of the heart with cardiac tamponade, myocardial infarction, pneumothorax and blood clot formation. Minor complications include pericardial or pleural effusion, respiratory embarrassment, femoral or phrenic nerve injury, pneumonia, and hypotension, bleeding or infection. Since almost all ablations involve a fluoroscope to position the catheters, there is some exposure to x-rays and the risks related to that exposure.
The ablation procedure
The diagnostic EP study will be performed by inserting hemostatic sheaths into the femoral and/or subclavian veins. Through these sheaths, long small temporary pacing catheters are passed under fluoroscopic guidance to the heart and positioned in the right atrium, near the His bundle, in the right ventricle and usually also in the coronary sinus. These catheters record activation of the heart and pacing can also be delivered to induce either tachycardias or bradycardias. In this way the heart electrical system can be assessed and arrhythmias induced. The patient’s arrhythmia can be induced in over 95% of the cases by putting in premature beats in either the atrium or the ventricle or by rapid burst pacing. Sometimes repeat stimulation after drugs like isoproterenol is required as well.
Next the intracardiac mapping procedure is performed. This involves moving a steerable catheter around the inside of the heart while the patient is in their arrhythmia to see where earliest activation occurs – this is the origin of the arrhythmia. Sometimes three-dimensional mapping systems are used for more complicated cases. For other cases such as Afib ablations, a special intracardiac ultrasound catheter is used to image intracardiac structures. Arrhythmias on the right side of the heart can be reached through the venous system. Arrhythmias on the left side of the heart can be reached via the femoral artery to the aorta then down through the aortic valve into the left ventricle. The second way is called trans-septal catheterization. With this technique, a needle is used to puncture the interatrial septum from the right atrium, which allows a long sheath to be passed into the left atrium.
The ablation procedure involves delivering energy through the ablation catheter, which is in contact with the target heart tissue. Radiofrequency (RF) energy is used to heat the tissue or cryoenergy to freeze the tissue. The energy kills the part of the heart which the catheter is touching producing a lesion. The typical RF lesion is about 6 x 6 x 6 mm in size, usually too small to weaken the heart wall in any way. If the ablation catheter was positioned properly then the arrhythmia origin is destroyed. A waiting period (usually 30 minutes or so) is observed to be sure that the arrhythmia origin does not recover function. If it does recover or if a second arrhythmia is induced, then the mapping and ablation procedure is repeated. Usually by the end of the procedure, no arrhythmia can be caused and the procedure then is considered successful. Rarely, other arrhythmias are found, but if these are not felt to have occurred clinically; they are usually ignored.
After the procedure
At the completion of the procedure, the patient goes to the recovery room where the IV sheaths are removed and pressure applied until bleeding is controlled and a band-aid applied to the site(s). After recovery the patient is transported back to their hospital room for a few hours of observation. A vast majority of our local patients do not spend the night in the hospital but go home in the early evening. Our patients that come from distance usually spend the night and then begin their journey home early in the afternoon of the next day. If the ablation result is favorable, the antiarrhythmic medications are stopped when the patient leaves the hospital. Usually anticoagulants are restarted at this time.
After the ablation for the patient
Small hematomas are typical at the site of the venous/arterial sheaths. Minor soreness in the chest is not unusual particularly if ablation involved areas near the sinus node, near the coronary sinus mouth or in the right ventricular outflow tract. Patients should not have severe chest pain, shortness of breath or recurrent arrhythmia. However after ablations near the AV node, sinus tachycardia may occur and last for days to weeks. This is called inappropriate sinus tachycardia and results from irritation of the autonomic nerves near the AV node. The tachycardia is called inappropriate since it occurs at rest and because it causes tachycardia out of proportion to the activity of the patient. Also withdrawal of beta-blockers for the ablation plays a role in some patients. This is usually transient and responds well to reassurance or to temporary beta blockade with subsequent weaning of the medications.
The other thing that frequently confuses patients is that they still have PVCs or PACs like they had before the ablation since these beats are not mapped and ablated. In fact before the ablation, it was these very beats, which provoked the arrhythmia. However, the mark of a successful ablation procedure is that these beats no longer provoke the arrhythmia as they did before ablation. We encourage patients to feel their pulse after these beats to ensure that the heart is not racing. We try to help them understand that every time this happens, it is a very good sign that the ablation procedure was a success.
Usually our patients are allowed to go home the evening after the procedure, but some spend the night in the hospital. Our usual recommendation is not to engage in strenuous exercise until 24 hours after the procedure. However going home and just lying around the house all day is also not advised because of the risk of DVT. We recommend doing normal activities at home. Motivated patients with sedentary jobs could return to work within 48 hours of the ablation procedure. Patients with strenuous jobs or those who had arterial access should probably wait up to 4 days. Sometimes the patient will be asked to come back to the EP’s office for a visit in 1-2 months. This would be particularly true for patients with WPW where an ECG can quickly predict whether the accessory pathway has recurred or not. For other patients, no follow up is required since there is nothing that can be tested in the office setting to prove that the ablation has succeeded. Ultimately, the passage of time without any more heart racing in a patient who is no longer taking heart rhythm medications strongly suggests that the procedure was a success.
The arrhythmia may recur in 2-15% of patients. Early recurrences (less than 6-12 months) usually mean a recurrence of the original cause of the arrhythmia whereas later recurrences may signal the appearance of a new arrhythmia. The exception to this is for patients having ablation for atrial fibrillation in which recurrences in the first 2 months or so do not necessarily mean that the ablation procedure failed. Options for patients with recurrence include the four original options:
- Doing nothing to prevent or cure the arrhythmia
- Taking medications
- Having another ablation either with the same physician or referral to another center
- Having open-heart surgery
Wellens H. Catheter ablation for cardiac arrhythmias. N Engl J Med. 2004; 351: 1172-1174
A good general review of ablation
Scheinman M, Calkins H, Gillette P etal. NASPE policy statement on catheter ablation: personnel, policy, procedures and therapeutic recommendations. PACE. 2003; 26: 789-799
A consensus paper from a group of prominent electrophysiologists
Scheinman M. Catheter ablation: a personal perspective. J Cardiovasc Electrophysiol. 2001; 12: 1083-1088
A good history of catheter ablation from one of the two pioneers
Skanes A, Klein G, Krahn A and Yee R. Cryoablation: potentials and pitfalls. J Cardiovasc Electrophysiol. 2004; 15: S28-S34
A scholarly review of cryoablation
Friedman P. Catheter cryoablation of cardiac arrhythmias. Current Opinion in Cardiology. 2005; 20: 48-54
A thorough review of cryoablation for cardiac arrhythmias
Stobie P and Green M. Cryoablation for septal accessory pathways: has the next ice age arrived? J Cardiovasc Electrophysiol. 2003; 14: 830-831
A somewhat skeptical editorial on cryoablation
Nakagawa H, Arruda M, Hazlitt A etal. Key references on radiofrequency catheter ablation (RFCA). Circulation. 1995; 91: 238-243
A listing of references on various ablation procedures for more in-depth study
Other articles about ablation
Packer D. Three-dimensional mapping in interventional electrophysiology: techniques and technology. J Cardiovasc Electrophysiol. 2005; 16: 1110-1116
A review of the various techniques with contrasts and comparisons
Bubien R, Knotts-Dolson S, Plumb V etal. Effect of radiofrequency catheter ablation on health-related quality of life and activities of daily living in patients with recurrent arrhythmias. Circulation. 1996; 94: 1585-1591
A study showing improved quality of life after ablation
Perisinakis K, Damilakis J, Theocharopoulos N et.al. Accurate assessment of patient effective radiation dose and associated detriment risk from radiofrequency catheter ablation procedures. Circulation. 2001; 104: 58-62
A discussion of the risks of using the fluoroscopy during ablation
DePonti R, Cappato R, Curnis A etal. Trans-septal catheterization in the electrophysiology laboratory. Data from a multicentric survey spanning 12 years. J Am Coll Cardiol. 2006; 47: 1037-1042
A discussion of the outcomes of this procedure including risks
Chu E, Kalman J, Kwasman M, etal. Intracardiac echocardiography during radiofrequency catheter ablation of cardiac arrhythmias in humans. J Am Coll Cardiol. 1994; 24: 1351-7
A review of using this technique to image intracardiac structures
Vora A, Green M, and Tang A. Safety and feasibility of same day discharge in patients undergoing radiofrequency catheter ablation. Am J Cardiol. 1998; 81: 233-235
A retrospective study suggesting that ablation can be safely performed as an outpatient
Epstein L, Chiesa N, Wong N etal. Radiofrequency catheter ablation in the treatment of supraventricular tachycardia in the elderly. J Am Coll Cardiol. 1994; 23: 1356-62.
Ablation is a very good option even for elderly people with SVT
Kugler J, Danford D, Houston K, etal. Radiofrequency catheter ablation for paroxysmal supraventricular tachycardia in children and adolescents without structural disease. Am J Cardiol. 1997; 80: 1438-1443
A registry showing the safety of ablation in children without structural heart disease
Scheinman M and Huang S. The 1998 NASPE prospective catheter ablation registry. Pacing and Cardiac Electrophysiology. 2000; 23: 1020-1028
Results of a prospective registry of 3357 RF ablation from 68 centers. The success rates for the following conditions were: AV nodal ablation with permanent pacemaker – 97%, AVNRT (SVT) – 96% with 1% risk of a permanent pacemaker, AVRT (including some with WPW) – 94%, atrial flutter – 86%, atrial tachycardia – 52-80%, and idiopathic VT – 86%
Bathina M, Mickelsen S, Brooks C, etal. Safety and efficacy of hydrogen peroxide plasma sterilization for repeated use of electrophysiology catheters. J Am Coll Cardiol. 1998; 32: 1384-1388
This form of resterilizing and reusing EP catheters is safe for patients and cost-effective for hospitals