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Ann Thorac Surg 2004;77:831-837
© 2004 The Society of Thoracic Surgeons
a Department of Cardiothoracic Surgery, Baylor University Medical Center, Dallas, Texas, USA
* Address reprint requests to Dr Patel, Baylor University Medical Center, Suite 1201, Barnett Tower, Dallas, TX 75246, USA
e-mail: anpatel72{at}hotmail.com
Presented at the Thirty-ninth Annual Meeting of The Society of Thoracic Surgeons, San Diego, CA, Jan 31–Feb 2, 2003.
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Abstract |
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METHODS: A prospective analysis of patients undergoing cardiac surgery was performed. Patients with a prior pacemaker/defibrillator, history of arrhythmia, preoperative antiarrhythmic, age greater than 85 years, history of stroke, or intraaortic balloon pump were excluded. Temporary epicardial atrial cardioversion wires were placed on the right and left atrium. Bipolar atrial and ventricular pacing wires were also placed. The wires were tested in the operating room. Patients who went into postoperative arial fibrillation were cardioverted with 3 J, 6 J, or 9 J.
RESULTS: There were 45 patients enrolled. Sixteen patients (35%) went into postoperative arial fibrillation during their hospital stay. Mean time to onset of arial fibrillation was 2.6 ± 1.4 days after surgery. Fifteen patients were successfully cardioverted to sinus rhythm on the primary cardioversion, with mean of 5.7 ± 2.4 J. One patient was cardioverted at 6 hours after onset of arial fibrillation, at 6 J. Recurrent arial fibrillation occurred in 4 patients during their hospital stay. All 4 of these patients were cardioverted with a mean of 6.4 ± 2.6 J. All wires were removed the day before patients were discharged. There were no complications with wire insertion or removal. There were no adverse neurologic events. The mean hospital stay was 5.1 ± 2.2 days. All patients were in sinus rhythm at 1 month follow-up.
CONCLUSIONS: The use of a temporary atrial defibrillator to resynchronize patients in postoperative arial fibrillation is safe and effective.
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Introduction |
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TopAbstractIntroductionPatients and methodsResultsCommentDiscussionReferences |
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Patients and methods |
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TopAbstractIntroductionPatients and methodsResultsCommentDiscussionReferences |
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Lead placement
The temporary atrial defibrillation system consists of two monopolar cardioversion leads (one for each atrium), a bipolar atrial, and a bipolar ventricular pacemaker wire (Syncrus System; Guidant Corporation, Santa Clara, CA) [11]. The implantation of the leads and wires is performed in the following manner. The left atrial cardioversion lead is implanted first while the patient is still on the cardiopulmonary bypass (CPB) machine. However the lead is implanted after a mitral valve repair or replacement is performed or after the distal anastomosis is performed to the circumflex artery or to the obtuse marginal artery. This reduces the risk of dislodgement of the cardioversion lead. The heart is lifted anteriorly and toward the right mediastinum. The cardioversion lead is placed epicardially using two-four bites as to create a line. Epicardial placement is used to decrease the risk of bleeding which could be seen with full thickness or endocardial bites. The first bite is taken by the left inferior pulmonary vein. The next bite is taken within 5 mm of the left superior pulmonary vein. The tip of the lead is then bent or frayed to prevent dislodgement (Fig 1). The heart is then placed back into its normal position. During this process the cardioversion lead is draped along the left atrial appendage and brought out through the skin and secured with suture. The bipolar ventricular pacing wire is placed after the patient is removed from CPB. It is placed on the right or left ventricle in the usual fashion and bought the skin and secured with suture. The right atrial cardioversion lead can be placed after the patient is off CPB and the venous cannula is removed. This enables the right atrium to be filled and enable easier placement of the lead. This may also result in shallower bites and less bleeding. The right atrial cardioversion lead is also placed in a linear fashion starting from the inferior vena cava, down to Waterston's groove and then up to 5 mm away from the sinoatrial node using two to four epicardial bites. The cardioversion lead is draped along the lateral side of the right atrium (Fig 2). The right atrial bipolar pacemaker wire is placed on the right atrial appendage in the usual fashion (Fig 2). Both the right atrial cardioversion lead and pacemaker wire are brought out together through the skin and secured using suture. The leads and wires are tested using a temporary pacemaker to determine if adequate contact is present to sense and pace. The cardioversion wires are tested by attaching the leads or wires to the atrial lead of the temporary pacemaker and set at 10 mA. If the electrical spikes are observed on the electrocardiogram (ECG), then successful placement has occurred. After surgery the patients are taken to the intensive care unit and transferred to the telemetry unit when stable on continuous 24-hour ECG monitoring until discharge.
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Results |
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Comment |
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The patients who went into postoperative atrial fibrillation had the "RAVE" (Rate control, correction of Acidosis, correction of Volume, and correction of Electrolytes) correction. The rate control is very important in patients who are taking preoperative ß blockers. These patients have a great risk having ß blocker withdrawal after surgery. All of the patients once off any vasopressors were restarted on their preoperative medications. The acidosis is important in patients in the intensive care unit. The patient's arterial blood gas is obtained and corrected to a base deficit of -2 or greater. This is to ensure that medical therapy has the optimal acid/base environment to function. The volume is corrected to euvolumia as tolerated. Patients are aggressively treated with diuretics after cardiac surgery. This may also serve as a trigger to for postoperative atrial fibrillation. The electrolytes obtained are ionized magnesium, ionized calcium, and potassium. All three electrolytes are corrected before cardioversion is attempted. As all these issues are being addressed, the patients are given the intravenous antiarrhythmic and then cardioverted.
The rational for very early cardioversion is related to the longer a stays in atrial fibrillation, the harder it is to return them to normal sinus rhythm. Minimal sedation is required due to very small amount of energy delivered to the patient. After the initial cardioversion, there were four patients with recurrent postoperative atrial fibrillation. Upon examination of the onset of the recurrence it was determined that this occurred within a couple of hours from switching from intravenous amiodarone to the oral form. As a result of this finding, we now give the oral amiodarone 6 hours after the intravenous has been started. This prevents the sudden drop in amiodarone levels in the blood. Once sinus rhythm is maintained with the protocol there was concern with removal of the wires and the potential for bleeding. Techniques using an S- or O-shaped pattern may have more contact but may increase the risk of bleeding. This is one of the reasons why we devised the linear wire implantation technique [11]. This reduces the resistance while removing the wires and hopefully reduces bleeding complications. The linear technique does decrease the amount of surface contact of the wires with the epicardium. However, we have found that this has not decreased the success of cardioversion.
The cardioversion leads in this study are different than the ones described by Kleine and Liebold [15, 19]. The leads in this study are made of a silver alloy to decrease oxidation. This enables the leads to function longer than the standard stainless steel leads. Stainless steel leads usually stop working within 5 days after surgery.
The high rate of successful cardioversion using the epicardial defibrillation leads is a multifactorial process. First, correct placement of leads adjacent to both the right and left pulmonary veins on the atrial tissue must be performed. Early cardioversion after correction of magnesium, potassium, and calcium, along with correction of acidosis and maintaining a euvolumic state are all important. The use of an antiarrhythmic for suppression of recurrence of atrial fibrillation is also a significant contributing factor. The earlier the patients are cardioverted after onset of atrial fibrillation, the easier it is to obtain and maintain sinus rhythm.
The use of a temporary epicardial atrial defibrillator when used in conjunction with a medical therapy protocol may help in treatment of postoperative atrial fibrillation. Further studies are required to compare this new combination therapy with standard medical therapy.
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Discussion |
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DR PATEL: Since the time of this abstract we have now placed more than 220 wire implants. We completed a cost analysis of our first set of patients compared with standard medical therapy. We found a decreased length of stay, which has resulted in a decreased cost. So the cost of implanting wires in all patients having cardiac surgery has been offset by the improved length of stay and decreased need for anticoagulation and readmission for postoperative atrial fibrillation.
DR ROGER C. MILLAR (Salt Lake City, UT): The question I had was related to increased costs. A standard set of pacing wires costs $30. You are putting in a $600 set of pacing wires. Also, the protocol you outlined of adding IV amiodarone bolus is quite expensive. It adds nearly $1,000 over starting PO amiodarone. You've got to sell your hospital on increasing costs $1,500 or more for the patients. Some of that is used even in those patients you don't use the atrial defibrillation on. Do some of the savings come from doing this on the ward instead of moving them to an intensive care unit? Is that what you have been doing with your protocols?
DR PATEL: To address all your questions: First, the device is about $500 to $600. However the cost of amiodarone is no longer $1,000. As of October 2002, amiodarone is now a generic medication that costs, IV, $140 to $200 per day for 24-hour usage. The oral form of it is down to about 80 cents per tablet for the 400 mg dose
When looking at the cardioversion, the patients are cardioverted both in the ICU and up on the floor, so we don't have to bring patients back. Our sedation protocol is so minimal that it is not conscious sedation. So as long as we actually sedate less than 2 mg of Versed, then we do not have a CRNA or anesthesiologist on standby. When we actually cardiovert these patients, we don't even open up a crash cart. So the cost savings are related to the avoidance of multiple problems that have been used with standard therapy.
DR MILLAR: Last question and then I'll relinquish the microphone. Who actually does the cardioversion? Do the staff physicians do this or is it supervised by someone else, such as a cardiologist?
DR PATEL: Good question. The first 90% of cardioversions were performed by us. Since that time we have had the cardiologists involved and we are training some of the nurse practitioners and physician assistants to cardiovert these patients. We just wanted to first prove that it is safe and effective before we relinquished the cardioversion.
DR JOHN D. PUSKAS (Atlanta, GA): My observation of your ability to convert most patients in 30 minutes suggests that you had someone very near. I'm guessing it was you with a beeper strapped to you for the duration of the study.
It would seem that the benefit to those patients is precisely that early conversion. And so my question is, if you had a beeper strapped to you and a set of external paddles rather than these internal wires and had used a similar amiodarone protocol, what differences do you think you might have seen in clinical efficacy and cost?
DR PATEL: The difference that you'd see if you used external paddles on these patients is related to the sedation, the analgesia, and the postoperative pain that would be involved. Giving an external defibrillation on the floor would involve at least CRNA or some other form of anesthesiology because you wouldn't be able to DC cardiovert or most patients wouldn't like it if they got a shock of 300 joules across their chest while on a telemetry floor. In the ICU in an intubated patient that may be possible. The success rate is related to the duration of time. The earlier the onset and the quicker return to sinus rhythm would improve patient outcomes.
DR PUSKAS: Am I to understand then that you do not perform external cardioversions on your telemetry floor?
DR PATEL: We do perform them. But there has to be a CRNA or an anesthesiologist present to give the medications. These internal wires allow for a low energy defibrillation, which alleviate extra personnel required for post procedure monitoring. Once a DC cardioversion is performed on a floor, there is a significant amount of postprocedure monitoring that is done. The low energy defibrillation patients are monitored only for about 30 minutes after this procedure is performed.
DR ALVAN W. ATKINSON (Raleigh, NC): You mentioned several parameters that you looked at, obviously metabolic parameters. Did you look at hematocrit? I don't think you mentioned it.
DR PATEL: I did not mention it as an independent factor but we try to keep the hematocrit above 30 if possible.
DR ATKINSON: And did you have any—I guess you didn't or you would have reported them—any ventricular fibrillation or other negative, more serious arrhythmias?
DR PATEL: When we first started the study we expected that there would be. That is why when asked if any of the ancillary personnel performed this cardioversion, we said no. If there was an adverse event with this new device/procedure we wanted to be present in order to treat the problem as soon as possible. But we have been very fortunate that we have not had any adverse events related to this procedure.
DR ATKINSON: I think you need to look at your cost analysis. I frankly think it's somewhat superficial. I mean our standard protocol is IV Cardizem until 24 hours after the atrial fibrillation has ceased, and moving on to amiodarone and so forth. And when you look at it, unless the patient has very high, uncontrolled tachyarrhythmias, we don't cardiovert people. But at the end of 5 days, most of the patients in our institution are in sinus rhythm from routine postoperative atrial fibrillation, and they haven't had internal paddles, they haven't had people going to the bedside. They simply had a drip of Cardizem and maybe some oral amiodarone. So I think you have to be very strict about what medications and who is doing what, before you simply say it's cost-effective because we saved a day of hospitalization.
DR PATEL: When we did our comparative study we compared standard medical therapy to it. It's true that a majority of the patients if left alone will go back to sinus rhythm with medical therapy as we've all seen. It's only about 2% who go into a chronic state.
But also looking at what are the neurological complications that may be attributed to postoperative atrial fibrillation, if we return these patients to both not only electrical sinus rhythm but also mechanical, that should alleviate the need for anticoagulation and potential neurological complications that are associated; even though small, every patient that has it is pretty significant.
DR ATKINSON: I think that echo is very interesting though, that immediate cardioversion doesn't end up with immediate normal atrial function. And that's probably why if you don't do immediate cardioversion they're much harder to cardiovert.
DR PATEL: That's true. In the electrophysiology literature it's been shown that there are standards saying that afibrillation begets afibrillation. So the longer you keep someone in afibrillation, the more difficult to get them out. But it's also related not only to the electrical phenomena but also the mechanical stunning, which has a significant impact as seen in some of the maze patients, that it's a long time after you return them to sinus rhythm that you'll actually see echographic evidence of return of mechanical function.
DR ANTONE J. TATOOLES (Oak Lawn, IL): We've used these wires in several patients. It's unfortunate in your video you didn't show your patient at the time of cardioversion. Our experience has been that these patients do have discomfort. Can you comment on the degree of patient discomfort associated with different energy levels? Have you compared patient discomfort using wires to external cardioversion?
DR PATEL: We have actually during our larger study taken pain scores for all of these patients—precardioversion, immediately after, and 6 hours after that. The patients actually do receive a mild jolt. Most patients in our later studies who actually have AICDs and have had a AICD fire, have felt that this is significantly less. But there is no difference in 3, 6, or 9 joules in the relative or perceived pain in these patients.
What you actually will see is, instead of what you see in DC cardioversion, the patient almost levitates off the bed, this patient almost looks like they're about to sit up. And it's related to where you place the wire in relation to the phrenic nerve. If you place it very posterior, you will see stimulation of the phrenic nerve and they look like they're about to hiccup and actually sit up on you.
But there is some discomfort with it and that is why we use a little bit of Versed and just standard analgesia. There have been some protocols proposed in Europe where they actually did the initial cardioversion without any sedation; and only if multiple cardioversions were needed, they sedated these patients.
DR JAN PIRK (Prague, Czech Republic): I am using this technique routinely and I did this defibrillation in more than 100 patients. I agree with you it's a very, very elegant method and the patients like it very much. Why did you exclude patients in the age over 85? I think these patients are in the very high risk of atrial fibrillation.
DR PATEL: The exclusion criteria were based initially not only for just safety purposes but actually to get it through our internal review board. Once the institutional review board saw the study and the results of the first 45 patients, they have actually opened it up and we actually implant wires in all patients regardless of age or other comorbidities. And actually we see a lot different cardioversion rates. They are all successful. But we actually use these in maze patients, balloon pumps—those are the patients who actually benefit from this therapy even more than the standard coronary patients who are young.
DR CRAIG R. SMITH (New York, NY): It sounds like this series is accumulating with admirably few adverse events. But I will predict that if you do this often enough, you will have someone who goes into ventricular fibrillation, and you will have someone whose atrial wire comes out with a piece of atrium still attached, and either of those things can be fatal if they happen in the wrong location. So I would stay tuned on safety.
DR PATEL: Oh, definitely. That's why we pay so close attention to this. There is a significant risk, especially with that left atrial wire, of tearing something out. So in reoperative patients we have actually modified our technique for safety, just to decrease the amount of dissection you have to do posterior. And along with also the worry that you will send some of these patients into ventricular tachycardias. That is a concern and that's why we still are aggressive. We're the ones who cardiovert as opposed to giving it to the ancillary staff.
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