Abstract-The function of heart rate variability (HRV) has been studied over the years, but less is known about the factors predicting recovery from work stress during sleep. The availability to register reliable data for short-time HRV has raised the interest to find the congestive HRV signal. The objective of this study was to identify individual-level factors related to work and leisure-time predicting the recovery of autonomic nervous system (ANS) during congestion measured by 24-h HRV. 15 subjects (11 men, aged 22 to 71, and 4 women, aged 54 to 63) with severe congestive heart failure (NYHA class 3-4). This group of subjects was part of a larger study group receiving conventional medical therapy prior to receiving the oral inotropic agent, milrinone. Questionnaire data was gathered with a self-administered questionnaire of individual characteristics, perceived work ability, stress and psychological resources. The individual recordings are each about 20 hours in duration, and contain two ECG signals each sampled at 250 samples per second with 12-bit resolution over a range of ±10 millivolts. In this study, we only calculate first 15 minus of each subject.Index Terms-Pointcaré plot, heart rate variability, chaos, congestive heart failure.
I. INTRODUCTIONHeart failure (HF), often called congestive heart failure (CHF) or congestive cardiac failure (CCF), occurs when the heart is unable to provide sufficient pump action to maintain blood flow to meet the needs of the body [1]- [3]. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition is diagnosed by patient physical examination and confirmed with echocardiography. Blood tests help to the etiology diagnosis. Treatment depends from severity and etiology of heart failure. In a chronic patient already in a stable situation, treatment commonly consists of lifestyle measures such as smoking cessation, light exercise, dietary changes, and medications. Sometimes, depending from etiology, it is treated with implanted devices (pacemakers or ventricular assist devices) and occasionally a heart transplant is required.Common causes of heart failure include myocardial infarction and other forms of ischemic heart disease, hypertension, valvular heart disease, and cardiomyopathy [4]. The term heart failure is sometimes incorrectly used for other cardiac-related illnesses, such as myocardial infarction (heart attack) or cardiac arrest, which can cause heart failure but are not equivalent to heart failure.Heart failure is a common, costly, disabling, and potentially deadly condition. [4] In developed countries, around 2% of adults suffer from heart failure, but in those over the age of 65, this increases to 6-10% [4], [5]. It is widely recognized that exercise training induces acute and chronic adaptations in heart rate (HR), but the exact mechanisms that mediate these changes are not clear [1]-[4]. It is hypothesized that training can affect autonomic regulation causing reduction in the sympathetic nerve...
