Autonomic Nervous System and Stress to Predict Secondary Ischemic Events after Transient Ischemic Attack or Minor Stroke: Possible Implications of Heart Rate Variability

Figure 1. Chronic stress, the nervous system, and development of the stress-related disorders. Chronic stressors, such as aging, diet, cigarette smoking, alcohol consumption, and psychological stress, continuously and cumulatively affect the stress systems [autonomic nervous system (ANS) and hypothalamic–pituitary–adrenocortical (HPA) axis], which lead to excessive production of stress hormones such as catecholamines and cortisol. These stress hormones affect the target tissues and cause various metabolic disorders, such as hypertension, diabetes, and dyslipidemia, which act as “secondary” stressors, and may progressively impair ANS function and ultimately lead to cardiovascular and cerebrovascular diseases.

Figure 2. Possible link between stress, autonomic nervous system (ANS) and progression of ischemic stroke. This process illustrates that the initial stress (as risk factors) affects ANS function and causes a dysfunctional ANS response to stress, which combined with the initial stressors causes the development of stress-related disorders. Acting as secondary stressors, these stress-related disorders may further impair ANS function and predispose to transient ischemic attack (TIA) or minor stroke. Finally, the initial and secondary stressors, along with dysfunctional ANS responses, contribute to the development of secondary ischemic events. Acute stressors precipitate the development of both initial TIA and minor stroke events and subsequent ischemic events. This vicious cycle leads to an accumulation of stress that affects the entire body, which potentially promotes the development of initial TIAs and the secondary ischemic events.

Figure 3. The logic of the heart rate variability (HRV)-based stress predictive model. All risk factors (stressors) have effects during the progression from transient ischemic attack (TIA) to the development of outcome events (ischemic stroke, TIAs, cardiovascular diseases, and vascular death). Autonomic nervous system (ANS) is directly affected by the risk factors/stressors; on the other hand, dysfunctional ANS activity conversely contributes to the development of risk factors/stressors. If correct, this model would suggest that whether HRV parameters (as markers of ANS) can predict the occurrence of secondary outcome events.