Atrial fibrillation after cardiac surgery : an analysis of risk factors, mechanisms, and survival effects
Year: 2008
Type: dissertation
Study design: Observational Study
Abstract: Background: Despite the recent improvements in surgical techniques and postoperative patient care, atrial \nfibrillation (AF) remains the most frequent complication after cardiac surgery. Although postoperative AF is \noften regarded as a benign clinical condition, this arrhythmia has significant adverse effects on patient \nrecovery and postoperative survival. Its exact pathophysiology has not yet been elucidated. The present \nthesis aims to analyze AF risk factors and their interaction, pre-existing histological explanatory alterations \nof the atrium, the AF impact on postoperative survival and the compliance of a prophylactic drug regimen. \nMethods: During a 10-year period, consecutive cardiac surgery cases with complete data on AF occurrence \nand postoperative survival were extracted. All patients were operated on for coronary or valvular surgery, \nwith cardiopulmonary bypass (CPB). Hospital and long-term survival data were obtained from Swedish \npopulation registry. Study I) Isolated coronary artery bypass grafting (CABG, n=7056), aortic valve \nreplacement (n=690) and their combination (n=688) were considered. Independent AF risk factors and AF \neffects on early and 1-year mortality were investigated. Study II) Patients affected by postoperative AF \namong isolated CABG patients (n=7621), valvular surgeries (n=995) and their combination (n=879) were \nstudied. Long-term survival was obtained and prognostic factors identified. Study III) Seventy patients were \nrandomized to on-pump (n=35) or off-pump (n=35) CABG. Samples from the right atrial appendage were \ncollected and histology was evaluated by means of light and electronic microscopy with reference to preexistent \nalterations related to postoperative AF. Study IV) Cardiac surgery patients with complete data on \nsmoking status (n=3245) were reviewed. Effects of smoking on AF development and interaction among \nvariables were explored. Study V) CABG patients without clinical contraindications to receive oral sotalol \n(80 mg twice daily) and magnesium were prospectively enrolled (n = 49) and compared with a matched \ncontemporary control CABG group (n = 844). The clinical compliance to the AF prophylactic drug regimen \nwas tested. \nResults: The overall AF incidence was around 26%, subdivided into 23%, 40% and 45% for isolated CABG, \nvalve procedures and their combined surgeries, respectively. Age was the strongest predictor of \npostoperative AF. Coronary disease superimposed risk factors with reference to myocardial conditions at \nCPB weaning. Considering the preoperative smoking condition, smokers demonstrated a reduced AF \nincidence compared to non-smokers (20% versus 27%, p<0.001). An interaction between smoking status and \ninotropic support was observed: without this interaction smoking conferred a 46% risk reduction of AF \n(p=0.011). At the histological level, myocyte vacuolization and nuclear derangement represented anatomical \nindependent AF predictors (p=0.002 and p=0.016, respectively). CPB exposure was not associated to \npostoperative AF nor histological changes. Although, postoperative AF increases the length of \nhospitalization in all patient groups, it did not affect the hospital survival. However, AF independently \nimpaired the late survival, a phenomenon seen in the CABG group only. With reference to the tested sotalolmagnesium \ndrug regimen, only 55% of CABG patients were compliant to the treatment, with marginal \neffects on AF occurrence. \nConclusions: In addition to age, details at the CPB weaning period, pre-existing histopathological changes, \nthe hyperadrenergic state and catecholamines are key mechanisms in the pathophysiology of postoperative \nAF. In particular, the CPB period hides valuable information for timely AF prophylactic stratifications. \nFurther, compliance effects due to patient selection should also be considered in a prophylactic therapy \nmodel. Postoperative AF increases late mortality after isolated CABG surgery, but not after valvular \nprocedures. Although the mechanisms are unclear, our results draw the attention to possible AF recurrence \nafter hospital discharge, indicating a strict postoperative surveillance.
Author: Giovanni Mariscalco
Language: English
Subfield: Cardiology and Cardiovascular Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W1727255336