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Are current smokers paradoxically protected against atrial fibrillation after cardiac surgery?
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Surgery.
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Surgery.
2009 (English)In: Nicotine & tobacco research, ISSN 1462-2203, E-ISSN 1469-994X, Vol. 11, no 1, 58-63 p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: The hyperadrenergic condition following surgical stress and inotropic drugs have been identified as leading causes for postoperative atrial fibrillation (AF). Smokers are characterized by higher catecholamine levels and tolerance. We tested the hypothesis that smoking patients are less prone to develop postoperative AF. METHODS: A total of 3,245 coronary artery bypass and valvular procedures were reviewed. Predictors of AF and interaction between variables were explored by multivariable logistic regression. AF-predictive scores were created and validated for goodness of fit, and receiver operating characteristic curves were created. RESULTS: Postoperative AF occurred in 26% of patients. Smokers accounted for 15% of the study population and demonstrated a reduced incidence of postoperative AF compared with nonsmoking individuals (20% vs. 27%, p < .001). Multivariate analysis revealed a significant interaction between smoking status and inotropic support requirement. The AF-protective effect of smoking was confounded by inotropic drugs. However, when we excluded from analysis the patients with inotropic support, smoking conferred a 46% risk reduction of AF (odds ratio [OR] = 0.54, 95% CI = 0.34-0.87, p = .011). In addition, age, valvular surgery, and hypertension were independently associated with AF. Postoperative AF increased the length of hospitalization, without affecting hospital mortality. AF was associated with an increased 1-year mortality (p = .002). DISCUSSION: Current smokers are less prone to develop AF after cardiac surgery. Our data support the hypothesis that hyperadrenergic state and catecholamines are key mechanisms in the pathophysiology of postoperative AF.

Place, publisher, year, edition, pages
2009. Vol. 11, no 1, 58-63 p.
URN: urn:nbn:se:umu:diva-22328DOI: 10.1093/ntr/ntn011PubMedID: 19246442OAI: diva2:214474
Available from: 2009-05-05 Created: 2009-05-05 Last updated: 2010-07-12Bibliographically approved
In thesis
1. Atrial fibrillation after cardiac surgery: an analysis of risk factors, mechanisms, and survival effects
Open this publication in new window or tab >>Atrial fibrillation after cardiac surgery: an analysis of risk factors, mechanisms, and survival effects
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Despite the recent improvements in surgical techniques and postoperative patient care, atrial fibrillation (AF) remains the most frequent complication after cardiac surgery. Although postoperative AF is often regarded as a benign clinical condition, this arrhythmia has significant adverse effects on patient recovery and postoperative survival. Its exact pathophysiology has not yet been elucidated. The present thesis aims to analyze AF risk factors and their interaction, pre-existing histological explanatory alterations of the atrium, the AF impact on postoperative survival and the compliance of a prophylactic drug regimen.

Methods: During a 10-year period, consecutive cardiac surgery cases with complete data on AF occurrence and postoperative survival were extracted. All patients were operated on for coronary or valvular surgery, with cardiopulmonary bypass (CPB). Hospital and long-term survival data were obtained from Swedish population registry. Study I) Isolated coronary artery bypass grafting (CABG, n=7056), aortic valve replacement (n=690) and their combination (n=688) were considered. Independent AF risk factors and AF effects on early and 1 year mortality were investigated. Study II) Patients affected by postoperative AF among isolated CABG patients (n=7621), valvular surgeries (n=995) and their combination (n=879) were studied. Long-term survival was obtained and prognostic factors identified. Study III) Seventy patients were randomized to on-pump (n=35) or off-pump (n=35) CABG. Samples from the right atrial appendage were collected and histology was evaluated by means of light and electronic microscopy with reference to preexistent alterations related to postoperative AF. Study IV) Cardiac surgery patients with complete data on smoking status (n=3245) were reviewed. Effects of smoking on AF development and interaction among variables were explored. Study V) CABG patients without clinical contraindications to receive oral sotalol (80 mg twice daily) and magnesium were prospectively enrolled (n = 49) and compared with a matched contemporary control CABG group (n = 844). The clinical compliance to the AF prophylactic drug regimen was tested.

Results: The overall AF incidence was around 26%, subdivided into 23%, 40% and 45% for isolated CABG, valve procedures and their combined surgeries, respectively. Age was the strongest predictor of postoperative AF. Coronary disease superimposed risk factors with reference to myocardial conditions at CPB weaning. Considering the preoperative smoking condition, smokers demonstrated a reduced AF incidence compared to non-smokers (20% versus 27%, p<0.001). An interaction between smoking status and inotropic support was observed: without this interaction smoking conferred a 46% risk reduction of AF (p=0.011). At the histological level, myocyte vacuolization and nuclear derangement represented anatomical independent AF predictors (p=0.002 and p=0.016, respectively). CPB exposure was not associated to postoperative AF nor histological changes. Although, postoperative AF increases the length of hospitalization in all patient groups, it did not affect the hospital survival. However, AF independently impaired the late survival, a phenomenon seen in the CABG group only. With reference to the tested sotalolmagnesium drug regimen, only 55% of CABG patients were compliant to the treatment, with marginal effects on AF occurrence.

Conclusions: In addition to age, details at the CPB weaning period, pre-existing histopathological changes, the hyperadrenergic state and catecholamines are key mechanisms in the pathophysiology of postoperative AF. In particular, the CPB period hides valuable information for timely AF prophylactic stratifications. Further, compliance effects due to patient selection should also be considered in a prophylactic therapy model. Postoperative AF increases late mortality after isolated CABG surgery, but not after valvular procedures. Although the mechanisms are unclear, our results draw the attention to possible AF recurrence after hospital discharge, indicating a strict postoperative surveillance.

Place, publisher, year, edition, pages
Umeå: Kirurgisk och perioperativ vetenskap, 2008. 40 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1156
atrial fibrillation, adult, cardiac surgery, coronary artery bypass grafting, valvular surgery, cardiopulmonary bypass, mortalilty, histology, catecholamines, embolism
National Category
urn:nbn:se:umu:diva-1798 (URN)978-91-7264-580-6 (ISBN)
Public defence
2008-09-25, Sal D, Tandläkarhögskolan, Byggnad 1 D, NUS, Umeå, 13:00 (English)
Available from: 2008-09-02 Created: 2008-09-02 Last updated: 2009-06-11Bibliographically approved

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