Eur J Cardiothorac Surg 1998;13:625-628
© 1998 Elsevier Science NL
Atrial fibrillation after surgery of the lung: clinical analysis of risk factors1
Wojciech Dyszkiewicz,
Mariusz Skrzypczak
Department of Thoracic Surgery, Karol Marcinkowski University of Medical Sciences, 62 Szamarzewski St., Pozna
, Poland
Received 28 September 1997;
received in revised form 17 March 1998;
accepted 24 March 1998.
Corresponding author. Tel./fax: +48 61 8669053.
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Abstract
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Objective: The aim of this study was to determine which of the clinical parameters are the most valuable in predicting postoperative atrial fibrillation after lung surgery. Materials and methods: Retrospective analysis was carried out on 298 patients after pulmonary resection necessitated mainly by lung cancer. The following parameters were investigated: age and sex, disturbances of cardiac rhythm, history of ischemic heart disease, diabetes and atherosclerosis, NYHA classification and type of surgical procedure. In addition, the duration of surgery, variations in oxygen saturation, changes in systemic blood pressure and heart-rate were noted intraoperatively. Statistical analysis was performed using Fisher's exact test. Results and conclusions: Atrial fibrillation occurred in 25 cases (8.4%) and more frequently after pneumonectomy (24%). Other factors contributing to atrial fibrillation after lung surgery were: history of ischemic heart disease, congestive heart failure, intraoperative cardiac arrest and the need for rethoracotomy.
Key Words: Surgery of the lung • Postoperative supraventricular arrhythmia
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Introduction
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Supraventricular cardiac arrhythmias, especially atrial fibrillation (AF) are the most common rhythm disturbances in patients following cardiac or pulmonary surgery
[1]
[2]
[3]. The overall rate of postoperative arrhythmia in a large series of pulmonary resections was 3.2–21%
[3]. The incidence of this complication is probably related to the magnitude of the operative procedure performed, occurring more frequently postpneumonectomy than postlobectomy. The reason why postoperative atrial fibrillation is of importance lies, not only in the immediate haemodynamic consequences in often critically ill patients, but also in the longer term potential for atrial thrombosis and systemic embolization
[4]. The main aim of our study was to ascertain whether there are factors which predispose to postoperative atrial fibrillation and if so, how important are they from the clinical standpoint.
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Material and methods
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Two-hundred and ninety-eight patients who had undergone pulmonary resections were retrospectively analysed. Reasons for the resection were: malignant tumours (73%), benign tumours (10%), tuberculosis (5%) and other lung diseases (12%). There were 227 men and 71 women, aged from 47 to 75 years (mean age: 66±10 years). The patients were divided into two groups depending upon the occurrence or absence of atrial fibrillation. Group I consisted of 273 patients who were free from rhythm disturbances. The remaining 25 patients exhibited episodes of atrial fibrillation and were placed in Group II. Once atrial fibrillation was diagnosed immediate treatment was introduced. Firstly special care was taken to maintain potassium levels above 4 mmol/l. Additionally magnesium sulphate (2.0–4.0 g/day) was administered in by continuous drip. In patients with severe hemodynamic impairment direct-current cardioversion was used. The remaining patients in Group II were treated with Verapamil, either alone or in combination with Amiodarone, Digoxin or Quinidine. We were able to restore stable sinus rhythm in all 25 patients who developed postoperative atrial fibrillation.
Our retrospective analysis considered those preoperative, intraoperative and postoperative factors which may contribute to or are associated with, the incidence of postoperative AF. Patients, who presented preoperatively with atrial fibrillation were not included to this study. In both groups we analysed the patient's age, sex and some elements of the clinical histories such as history of ischemic heart disease, dysrhythmias, congestive heart failure (NYHA classification), diabetes and systemic hypertension. General laboratory investigations included those for serum electrolytes, cardiac enzymes, arterial blood gases and hemoglobin. Chest x-rays, ultrasonography of the abdomen, lung spirometry and ECG were also performed routinely in all patients. ECG monitoring was carried out continuously for the first 3 postoperative days. In our analyses of the intraoperative records interest was focused on the duration of the operation, variations in the oxygen saturation of arterial blood (SO2<90%), systemic hypotension (decrease of more than 30% of initial value), hypertension (over 180 mmHg), bradycardia (<50), tachycardia (>140) or cardiac arrest. Postoperative complications, especially haemorrhage and the need for rethoracotomy, atelectasis or pulmonary edema as well as the mortality rate in both groups, were also investigated. Finally, we considered the incidence of AF in relation to both the reason for, and type of, surgery carried out.
Statistical analysis
The association between groups and the differences between two proportions were compared by using Fisher's exact test. P-Values less than 0.05 were considered significant.
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Results
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Preoperative risk factors in patients with and without AF are compared in Table 1. Atrial fibrillation was significantly more frequent in patients with a history of ischemic heart disease or symptoms of congestive heart failure.
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Table 1. Comparison of preoperative factors in patients without AF (Group I) or with AF (Group II) following lung surgery
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Intraoperative factors that may contribute to postoperative AF are presented in Table 2. As shown in this table, the greater the extent of pulmonary resection (pneumonectomy) and the occurrence of intraoperative cardiac arrest significantly increased the prevalence of AF. Cardiac arrest during the operation occurred only in two patients who developed AF subsequently (Group II).
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Table 2. Comparison of intraoperative factors in patients without AF (Group I) and with AF (Group II) following lung surgery
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Postoperative factors in both groups of patients are compared in Table 3. The only factor which was found significantly more frequently in patients with postoperative AF was the need for rethoracotomy. In Table 4 the incidence of AF in patients operated on for lung cancer is compared with the incidence in those operated on for other lung diseases. The same table also shows the incidence of AF in relation to the surgical procedure used. The incidence of AF was approximately the same in the two groups depending only on the extent of surgical procedure performed. However, the comparison of AF occurring in total number of patients operated for lung cancer or other lung diseases revealed a trend to more frequent AF in patients with lung cancer. There was no significant difference in the overall mortality rate between Group I and II namely 3 and 4%, respectively.
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Table 3. Comparison of postoperative factors in patients without AF (Group I) and with AF (Group II) following lung surgery
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Table 4. Comparison of incidence of AF in patients operated on for lung cancer and in those operated on with other lung diseases in relation to the surgical procedure performed
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Discussion
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Although arrhythmias occurring after pulmonary resections were first reported in 1943 by Currens and Bailey, much speculation still exists regarding their etiology. Most authors consider increased vagal tone, hypoxemia, hypercapnia, intraoperative fluid imbalance and pericardial handling to be deciding factors
[1]
[2]
[3]
[5]. Intraoperative hypotension has also been related to increased risk of arrhythmia
[3] but we were unable to prove this in our patients. Equally, we did not find advanced age to be an important factor accounting for AF.
Several previous studies have failed to demonstrate any significant relation between either preoperative pulmonary function, indications for surgery or lung cancer staging and the development of AF. On the other hand, Ritchie et al.
[6] has shown that cardiac arrhythmias may be linked to malignancy. Beck-Nielsen et al.
[1] also reported a greater frequency of postoperative AF in patients with lung cancer
[1] and the same tendency was observed in our study (Table 4). Ten percent of our patients with lung cancer developed AF postoperatively, compared with only 4% of our patients with other pulmonary diseases. We were also able to demonstrate a correlation between the magnitude of the surgical resection performed and postoperative AF. Arrhythmia occurred in 12 patients postpneumonectomy (24%) but in only 11 patients postlobectomy (6%) or in two patients following wedge resections (3%). Such a relationship has also been reported by Motta and Ratto
[5]. Besides pneumonectomy, the need for rethoracotomy also contributed significantly to atrial fibrillation. In most cases bleeding was the main reason for reoperation. The two cases of cardiac arrest were found in our study only in the group of patients who subsequently developed AF. However, the small number of cases and various factors which may lead to intraoperative cardiac arrest (hypovolemia, myocardial ischemia, increased vagal tone, etc.) do not allow for any definite conclusion to be drawn as to its contribution to postoperative AF. In our study, a history of ischemic heart disease and preoperative symptoms of congestive heart failure (NYHA III) posed a significant risk of postoperative AF. This corroborated the data of other authors
[2]
[3].
The etiology of postoperative dysrhythmias is still poorly understood. It is of interest that about 30% of the human population is thought to be predisposed to develop atrial fibrillation. These are individuals with an increased susceptibility to AF due to different refraction times within the same areas of the atrium
[7]. This electrophysiological anomaly can become more intense when ischemia or electrolyte imbalance occur during surgery resulting in postoperative arrhythmia. In our study we delineated only a limited number of pre-, intra- and post-operative factors which may increase the risk of occurrence of such complication in patients undergoing thoracic surgery. We were not able to confirm many of the factors mentioned by other authors as predisposing to AF. This may be due to the retrospective character of the study. It follows that further prospective studies are needed to clarify existing controversies about the underlying mechanism of postoperative atrial fibrillation.
Conclusion
Factors, which have been found to be significantly associated with atrial fibrillation following pulmonary resections are: (1) preoperative: a history of ischemic heart disease and symptoms of congestive heart failure; (2) intraoperative: pneumonectomy and cardiac arrest; (3) postoperative: haemorrhage and the need for rethoracotomy.
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Footnotes
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Presented at the 11th Annual Meeting of the European Association for Cardio-thoracic Surgery, Copenhagen, Denmark, September 28 – October 1, 1997. 
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Appendix A. Conference discussion
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Dr Benfield (Sacramento, California): In my experience atrial fibrillation has most often occurred around the second or third postoperative day. I haven't actually tabulated this, and so I'm wondering if in your review you did note when during the postoperative period the fibrillation occurred. Secondly, I have noted that when the atrial fibrillation occurs it's most often at a time when the pulmonary secretions aren't being raised well and when there may be some degree of either recognized or subclinical temporary atelectasis. Did you note or did you not note any correlation between atelectasis and the occurrence of atrial fibrillation?
Dr Dyszkiewicz: Regarding your first question about the days of occurrence: in 80% of our cases atrial fibrillation occurred within the first 3 days. I did not show it, but it is interesting that most of the other authors also emphasized that there are 2 or 3 crucial days for atrial fibrillation to occur. So we really saw the same as you. For the remaining 20%, it may occur at any time and we were able to detect it up to 7 days. We use continuous ECG monitoring up to the 3rd day, and later, Holter analyzers. So our results are approximately the same as yours, but 80% occurred within the first 3 days. Concerning the second question, we also checked if there was any correlation with postoperative atelectasis, especially on the 1st or 2nd day, because it could be linked to the atrial fibrillation occurring at the same time, but we did not find any significant correlation.
Dr Venuta (Rome, Italy): In the past it has been a common attitude in several centres to digitalize patients at high risk immediately after the operation, especially when a pneumonectomy was performed, and since you reported a retrospective analysis of your data, I would like to ask you if you did digitalize any of these patients at high risk or you just treated complications when they occurred after the operation. Thank you.
Dr Dyszkiewicz: I am also a cardiac surgeon, and as I am well aware that digitalization has failed many times as a prophylactic drug in any rhythm disturbances, we didn't use it. Many other authors deny that digitalization gives any improvement or diminishes the number of atrial fibrillation after operation. What is more, digitalization can, even by itself, generate atrial fibrillation. This is a well-known phenomenon in cardiology. So we never use any drugs like digitalis. In fact we never use any drugs before operation but our approach when atrial fibrillation does occur is very aggressive. We are keen to reverse the fibrillation as soon as possible by electrical defibrillation. It was successful in 80% of our cases, and, if not, we used either Verapamil or beta blocking agents intravenously. So we had a nice rate of about 80% of our patients with stable sinus rhythm. Only in the remaining 20% we observed a recurrence of atrial or other supraventricular rhythm disturbances, but that's not the question to be answered here.
Dr Nazari (Pavia, Italy): I wonder if you checked the shift of the mediastinum after the surgical procedure and if you found any correlation between the entity of displacement of the mediastinum and the incidence of atrial fibrillation.
Dr Dyszkiewicz: Yes. This can be attributed to those cases which were treated by pneumonectomy. After pneumonectomy there is always, or very often, a shift of the mediastinum. So it might be that this is one of the factors which also contributes to the atrial fibrillation.
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References
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- Beck-Nielsen J., Sorenson H.R., Astroup P. Atrial fibrillation following thoracotomy for non cardiac disease, in particular cancer of the lung. Acta Med Scan 1973;193:425-427.[Medline]
- Cheng T.O. Postoperative supraventricular tachyarrhythmias. Ann Thorac Surg 1982;3:528-530.
- Von Knorring J., Lepantalo M., Lindgren L., Lindford O. Cardiac arrhythmias and myocardial ischemia after thoracotomy for lung cancer. Ann Thorac Surg 1992;53:642-647.[Abstract]
- Ziomek S., Read R.C., Tobler G. Thromboembolism in patients undergoing thoracotomy. Ann Thorac Surg 1993;56:223-225.[Abstract]
- Motta G., Ratto G.B. Complications of surgery in the treatment of lung cancer: their relationship with the extent of resection and preoperative respiratory function tests. Acta Chir Belg 1989;89:161-163.[Medline]
- Ritchie A.J., Danton M., Gibbons J.R. Prophylactic digitalization in pulmonary surgery. Thorax 1992;47:41-42.[Abstract]
- Cox J.L. A perspective of postoperative atrial fibrillation in cardiac operations. Ann Thorac Surg 1993;56:405-408.[Medline]
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Abstract
Introduction
