Assessing the interrelation between oestrogen receptor status, heart rate variability and serum nitric oxide in breast cancer patients: Understanding their prognostic relevance.

Abstract

e12564 Background: Heart Rate Variability (HRV) is a non-invasive procedure to assess cardiac functions and provides an index of autonomic function that intricately controls vascular tone. Studying the alteration in HRV with agents producing oxidative stress will provide useful information about disease progression. Lower HRV indicates low level of Parasympathetic Nervous System activation and dysregulation of cardiac functions. Elements of tumour microenvironment like prostaglandin E2, oestrogen and hypoxia stimulate nitric oxide (NO) production which reacts with free radicals released by tumour tissue forming oxidising agents. NO enhances oxidative stress causing vascular dysfunction. Very few studies have reported an interrelationship between NO and HRV parameters in breast cancer. The aim of the study is to verify the relation between HRV and serum NO levels in ER+ and ER- breast cancer groups. Methods: Study design: Analytical, Cross sectional. Sample Size: 135 women above 20 years of age with and without breast cancer. 69 women with histologically proven breast cancer in different stages and 66 women who were healthy age matched controls were included. Oestrogen Receptor (ER) status was obtained from clinical records. Out of 69 women with breast cancer, 31 were ER- with 15 in stage 1 and 16 in stage 2. 38 women were ER+ with 5 in stage 2 and 33 in stage 3. Serum NO was measured using colorimetry. Heart Rate Variability was measured from lead II ECG using Power Lab 15T and lab chart software. Serum NO levels and HRV parameters were compared between ER groups. Results: ER+ women had higher HRV with parasympathetic predominance compared to ER- with p<0.001. ER+ women also had higher serum NO levels compared to ER- group with p<0.001. Though no direct correlation was noticed between NO and HRV, multiple analysis of variance showed significant (p<0.001) difference of all values across the groups. irrespective of menopausal status. Conclusions: A significant difference was observed in HRV of ER+ and ER- women with breast cancer. Most ER+ women were in stage 3 with significantly higher NO levels. Serum NO is expected to be the factor most responsible for HRV changes particularly in stage 3/ER+. Parasympathetic predominance seen in ER+ women possibly is due to high NO levels.[Table: see text]