Objective: Phobic anxiety is a risk factor for poor prognosis following Acute Coronary Syndrome (ACS). A psychophysiological marker of vagal function, autonomic dysfunction may play a critical role in this relationship. The aim of the study was two-fold: to assess whether phobic anxiety was characterised by autonomic dysfunction (heart rate variability) in the short (1-month) and longer term (12-months) following ACS, and (ii) to quantify the extent to which HRV parameters modified the effect of phobic anxiety on all-cause hospital readmission over 2 years. Methods: The ADVENT study followed 416 ACS patients. At 1-month following discharge (T0), phobic anxiety and autonomic functioning were assessed using the Crown Crisp Index (CCI) and 11 indices of heart rate variability (HRV), respectively. HRV was measured again at 12-months (T1) (n = 359). Hospital readmission (all cause) was derived from an audit of hospital records by two medically trained research fellows. Generalised linear modelling (GLM) was used to first determine the association between CCI score at T0 and HRV parameters at T0 and T1. Binary logistic regression was used to measure the relationship between CCI scores and readmission (yes/no) and the extent to which HRV parameters modified this effect. Results: CCI scores were associated with 7 of the 11 indices of HRV: Average RR (ms), SDRR (ms), RMSSD (ms), SDSD (ms), pRR50 (%), LF Powers (ms2) and HF Powers (ms2) at T0 but not T1. CCI scores at T0 significantly predicted likelihood of readmission to hospital in the subsequent 2 year period. No parameter of HRV at T0 modified this effect. Limitations: We were unable to provide adjudicated major adverse coronary events outcome data, or account for changes in medication adherence, diet or physical activity. Conclusions: While phobic anxiety is associated with both reduced vagal function in the short term after an ACS event and 2 year all cause readmission, HRV does not appear to be the pathway by which phobic anxiety drives this outcome.
Hypercapnia increase minute ventilation (V'E) with little effect on heart rate (HR), whereas hypoxia may increase HR without affecting V'E. However, the effects of hypercania and hypoxia on both heart rate variability (HRV) and the clustering of the heart beats during spontaneous breathing (respiratory sinus arrhythmia -RSA) are not clear. "From abstract"