J Rehabil Med 43 ORIGINAL REPORT J Rehabil Med 2011; 43: 720–727 © 2011 The Authors. doi: 10.2340/16501977-0843 Journal Compilation © 2011 Foundation of Rehabilitation Information. ISSN 1650-1977 Objective: Cardiac rehabilitation is associated with cardiac autonomic and physiological beneits. However, it is unclear whether baseline left ventricular function (LVF) impacts on training-induced cardiac autonomic adaptations. The aim of this study was to assess the cardiac autonomic adaptations in patients with varying left ventricular function proiles un- dergoing coronary artery bypass grafting and cardiac reha- bilitation. Design: Assessor-blinded prospective trial. Patients: Forty-four patients undergoing coronary artery bypass grafting, divided into normal LVFN (≥ 55%, n = 23) or reduced LVFR (35–54%, n = 21) were evaluated. Method: Cardiac autonomic function was evaluated by heart rate variability indexes obtained both pre- and post-cardiac rehabilitation. All patients participated in a short-term (ap- proximately 5 days) supervised inpatient physiotherapy pro- gram. Results: There were differences in heart rate variability in- dexes, correlation dimension and SD2 according to time and group (e.g. interaction time (effect of cardiac rehabilitation) vs group (LVFN vs LVFR), p = 0.04). Simple main effects analysis showed that the LVFR group beneited to a greater degree from cardiac rehabilitation compared with the LVFN group. Heart rate variability indexes increased signiicantly in the former group compared with the latter. Conclusion: Among post-coronary artery bypass grafting patients engaged in short-term inpatient rehabilitation, those with reduced left ventricular function are most likely to have better cardiac autonomic adaptations to exercise- based rehabilitation. Key words: coronary artery bypass grafting; physiotherapy; ex- ercise therapy; autonomic nervous system; heart rate control. J Rehabil Med 2011; 43: 720–727 Correspondence address: Audrey Borghi-Silva, Cardiopul- monary Physiotherapy Laboratory, Nucleus of Research in Physical Exercise, Physiotherapy Department, Federal University of Sao Carlos, Sao Paulo, Brazil. Washington Luis Highway (SP 310) KM 235, 13565-905 São Carlos, Brazil. E-mail: audrey@ufscar.br Submitted January 21, 2011; accepted May 18, 2011 INTRODUCTION Heart rate variability (HRV) is the most frequently used non-invasive method for assessing autonomic activity and its inluence on the cardiovascular system. Thus, HRV is valu- able in providing information on the heart’s ability to respond to normal regulatory impulses that affect its rhythm (1). It is well known that after cardiac procedures such as cardiac valve surgery and coronary artery bypass grafting (CABG), HRV becomes signiicantly decreased (2, 3). Decreased HRV is associated with abnormal and insuficient adaptability of the autonomic nervous system and has been shown to be a predictor of hemodynamic instability and mortal- ity (1). In this context, compromised cardiac autonomic (CA) regulation may result in increased arrhythmia susceptibility and subsequent risk of cardiovascular death, more myocardial ischemic episodes and worsening clinical course after CABG with more inotropic support and longer periods in the intensive care unit (4–6). For these reasons, many investigators have focused on strategies positively impacting the CA system in patients undergoing cardiac surgery, one of which is exercise-based cardiac rehabilitation (CR) (7, 8). In previous studies, long- term outpatient CR was associated with favorable alterations in HRV potentially resulting from adaptations in peripheral and central neural pathways (9). Recently, however, our group has demonstrated that a short- term inpatient CR program results in early CA beneits in post- CABG patients (10). However, the inluence of key baseline characteristics on the impact of CA alterations following CR, such as left ventricular function (LVF), was not considered. A previous study (11) assessing physical performance re- ported that patients with poor LVF are most likely to respond favorably to inpatient CR. In addition, it is known that these patients are more likely to demonstrate impaired CA function, characterized by lower values of HRV (12). In this context, little information exists on how normal vs reduced LVF affects CA adaptations after inpatient CR in post-CABG patients. The aim of this study was to assess the CA adaptations in patients with normal and reduced LVF undergoing CABG and LeFT-VeNTRICULAR FUNCTION AND AUTONOMIC CARDIAC ADApTATIONS AFTeR SHORT-TeRM INpATIeNT CARDIAC ReHABILITATION: A pROSpeCTIVe CLINICAL TRIAL Renata Gonçalves Mendes, MSc 1 , Rodrigo Polaquini Simões, MSc 1 , Fernando de Souza Melo Costa, MSc 1 , Camila Bianca Falasco Pantoni, PT 1 , Luciana Di Thommazo, PT 1 , Sérgio Luzzi, MD 2 , Othon Amaral-Neto, MD 2 , Aparecida Maria Catai, PhD 1 , Ross Arena, PhD 3 and Audrey Borghi-Silva, PhD 1 From the 1 Cardiopulmonary Physiotherapy Laboratory, Nucleus of Research in Physical Exercise, Federal University of Sao Carlos, 2 Irmandade Santa Casa Misericordia Hospital, Araraquara, Sao Paulo, Brazil, and 3 Physical Therapy Program, University of New Mexico, Albuquerque, New Mexico, USA