Heart Rate Variability (HRV) analysis has become an important tool in assessing human Autonomic Nervous System (ANS) activity in recent years. Orthostatic challenge is one of the most common tests to detect ANS dysfunction. In this study we looked at the changes in ANS activity of normal subjects to orthostatic challenge and compared the results of 3 different HRV analysis methods: Time-Domain Methods, HRV spectral analysis without respiratory analysis (RA) and with RA. Although all three methods have indicated an increase in sympathetic activity and a decrease in parasympathetic activity from baseline to stand, the only significant increase in sympathetic activity was observed in HRV with RA method. Additional information from RA enables isolating the sympathetic and parasympathetic branches in HRV signals and therefore reflects ANS changes more accurately. On the other hand, sympathetic and parasympathetic power may not be separated properly if respiration-dependent fluctuations in HRV are ignored. It is expected that the differences between methods would be very clear with low respiratory rates. However, we focused on studies with normal respiratory rates and have also found significant differences among the methods.

In the nonsurvivors, low flow, low MAP, and reduced tissue perfusion were associated with pronounced increases in PSNS and lesser increases in SNS activity. In the survivors, higher CI, MAP, and PtcO2/FIO2 values were associated with lesser increases in both PSNS and SNS activities.

BackgroundRanolazine (RAN) reduces cardiac sodium channel 1.5’s late sodium current in congestive heart failure (CHF), reducing myocardial calcium overload, potentially improving left ventricular (LV) function. RAN blocks neuronal sodium channel 1.7, potentially altering parasympathetic and sympathetic (P&S) activity. The effects of RAN on LV ejection fraction (LVEF) and P&S function in CHF were studied.MethodsMatched CHF patients were given open-label RAN (1000 mg po-bid) added to guideline-driven therapy (RANCHF, 41 systolic, 13 diastolic) or no adjuvant therapy (control, NORANCHF, 43 systolic, 12 diastolic). Echocardiographic LVEF and P&S measures were obtained at baseline and follow-up (mean 23.7 months).ResultsLVEF increased in 70% of RANCHF patients, an average of 11.3 units. Mean LVEF remained unchanged in NORANCHF patients. P&S measures indicated cardiovascular autonomic neuropathy (P≤0.1 bpm2) in 20% of NORANCHF patients at baseline and in 29% at follow-up (increasing in both groups). At baseline, 28% of patients had high sympathovagal balance (SB), RAN normalized SB over 50% of these; in contrast, the NORANCHF group had a 20% increase in patients with high SB.ConclusionsRAN preserves or improves LVEF and decreases high SB in CHF.

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The ANS method enables quantitative assessment of CAN by independently and simultaneously quantifying the two branches of the ANS, sympathetic and parasympathetic. The ANS method modifies standard spectral analysis of HRV (without RA analysis) by incorporating spectral analysis of RA. The ANS method appears to model the normal and abnormal responses to upright posture and changes in vasopressor therapy with greater fidelity than the HRV method. Independent, simultaneous assessment of progressive parasympathetic and sympathetic dysfunction, autonomic imbalance, and responses of the two ANS branches to therapy seems to enable early detection and early intervention. Orthostasis, by way of example, illustrates that frequent, sensitive assessments of both ANS branches can improve the negative outcomes associated with CAN.

Surges in autonomic activity in the period immediately after emergency department admission of trauma patients were associated with pronounced increases in cardiac index, mean arterial pressure, and heart rate and reduced tissue oxygenation.

BackgroundCoronary heart disease (CHD) is a major health concern, affecting nearly half the middle-age population and responsible for nearly one-third of all deaths. Clinicians have responsibilities beyond diagnosing CHD, including risk stratification of patients for major adverse cardiac events (MACE), modifying the risks and treating the patient. In this first of a two-part review, identifying risk factors is reviewed, including more potential benefit from autonomic testing.MethodsTraditional and non-traditional, and modifiable and non-modifiable risk factors for MACE where compared, including newer risk factors, such as inflammation, carotid intimal thickening, ankle-brachial index, CT calcium scoring, and autonomic function testing, specifically independent measurement of parasympathetic and sympathetic (P&S) activity.ResultsThe Framingham Heart Study, and others, have identified traditional risk factors for the development of CHD. These factors effectively target high-risk patients, but a large number of individuals who will develop CHD and MACE are not identified. Many patients with CHD who appear to be well-managed by traditional therapies still experience MACE. In order to identify these patients, other possible risk factors have been explored. Advanced autonomic dysfunction, and its more severe form, cardiac autonomic neuropathy, have been strongly associated with an elevated risk of cardiac mortality and are diagnosable through P&S testing.ConclusionsIndependent measures of P&S activity, provides additional information and has the potential to incrementally add to risk assessment. This additional information enables physicians to (1) specifically target more high-risk patients and (2) titrate therapies, with autonomic testing guidance, in order to minimize risk of cardiac mortality and morbidity.

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