ABSTRACT
ABSTRACT BACKGROUND: Coronary artery disease is an important cause of morbidity and mortality. The impact of ventricular arrhythmias with impaired cardiac vagal activity is one of the most recently studied prognostic factors. However, there are no studies evaluating the phenomenon of heart rate turbulence (HRT) during physical exertion. OBJECTIVE: To study the behavior of HRT during exercise testing, among individuals after myocardial infarction. DESIGN AND SETTING: Feasibility study conducted in a university hospital among individuals 4-6 weeks after myocardial infarction. METHODS: All subjects underwent 24-hour Holter monitoring and ergometric stress testing. We considered that abnormal HRT was present if the turbulence onset was ≥ 0% or turbulence slope was ≤ 2.5 mm/relative risk interval. RESULTS: All 32 subjects were asymptomatic. Their median age was 58 years (interquartile range 12.8) and 70% were male. Abnormal HRT was associated with ventricular dysfunction in this population. We found no differences regarding the behavior of HRT, in relation to age, gender, smoking, systemic arterial hypertension, diabetes mellitus or dyslipidemia. Ergometric stress testing detected premature ventricular beats (PVB) in approximately 44% of the examinations, and these occurred both during the active phase of effort and in the recovery period. The low occurrence of several isolated PVB in beta-blocked subjects made it difficult to perform statistical analysis to correlate HRT between ergometric and Holter testing. CONCLUSION: The data obtained in this study do not support performing HRT through ergometric stress testing among patients who remain on beta-blockers post-myocardial infarction, for the purpose of assessing cardiac vagal activity.
ABSTRACT
Objective:To evaluate the clinical value of the transcutaneous neuromodulation (TN) in improving gastrointestinal function after gastrointestinal tumor operation.Methods:From April 2019 to June 2020, at The Affiliated People′s Hospital of Ningbo University, 100 patients who underwent gastrointestinal tumor surgery were included. The 100 patients were randomly divided into treatment group(receiving TN treatment, 50 cases)and control group (receiving sham TN treatment, 50 cases). The clinical data of the two groups was compared to evaluate the recovery of gastrointestinal function, which included the time of first defecation, time of first flatus, time of first ambulation, time of resuming diet, the incidence of nausea and vomiting within 3 d after operation and pain score (0 to 10). Heart rate variability (HRV) was compared between two groups to analyze the possible mechanism of TN improving gastrointestinal function after gastrointestinal tumor surgery. Independent sample t test and Chi-square test were used for statistical analysis. Results:Among 100 patients, there were 63 male and 37 female patients, the age was (67.0±11.3) years old, ranged from 28 to 92 years old. Compared with the control group, the time of first defecation, first flatus, first ambulation and resuming diet of treatment group reduced by 31.0%, 39.8%, 38.0% and 32.4% ((72.1±3.0) h vs.(104.5±2.9) h, (49.4±5.7) h vs.(82.1±3.1) h, (3.1±0.7) d vs.(5.0±0.9) d, (4.8±0.9) d vs. (7.1±0.8) d)), respectively; the pain scores on the day 2 and day 3 after operation and incidence of nausea and vomiting within 3 d after operation decreased by 50.0%, 65.5%, 26.0%(1.5±0.6 vs. 3.0±0.7, 1.0±0.6 vs. 2.9±0.6, 16.0%, 8/50 vs. 42.0%, 21/50), respectively, and the differences were statistically significant ( t=54.28, 35.72, 11.67, 13.66, 12.00 and 14.90, χ2=8.21, all P<0.01). The results of HRV analysis showed that the high frequency on day 3 was higher than that on day 1 of treatment group, and the ratio of low frequency to high frequency after operation was lower than that before operation of treatment group (0.5±0.1 vs. 0.4±0.1, 1.2±0.7 vs. 1.9±1.0), and the differences were statistically significant( t=-4.81 and 4.26, both P<0.01), which indicated TN could enhance vagal activity. Conclusions:TN promote the recovery of gastrointestinal function after gastrointestinal tumor operation, and can be used as an adjuvant therapy to accelerate the recovery of gastrointestinal function after gastrointestinal tumor operation.
ABSTRACT
BACKGROUND: chronic hypoxia increases basal ventilation and pulmonary vascular resistance, with variable changes in arterial blood pressure and heart rate, but it's impact on heart rate variability and autonomic regulation have been less well examined. We studied changes in arterial blood pressure, heart rate and heart rate variability (HRV) in rabbits subjected to chronic normobaric hypoxia (CNH; PB ~ 719 mmHg; FIO2 ~ 9.2%) for 14 days and assess the effect of autonomic control by acute bilateral vagal denervation. RESULTS: exposure to CNH stalled animal weight gain and increased the hematocrit, without affecting heart rate or arterial blood pressure. Nevertheless, Poincaré plots of the electrocardiographic R-R intervals showed a reduced distribution parallel to the line of identity, which interpreted as reduced long-term HRV. In the frequency domain, CNH reduced the very-low- (< 0.2 Hz) and high-frequency components (> 0.8 Hz) of the R-R spectrograms and produced a prominent component in the low-frequency component (0.2-0.5 Hz) of the power spectrum. In control and CNH exposed rabbits, bilateral vagotomy had no apparent effect on the short- and long-term HRV in the Poincaré plots. However, bilateral vagotomy differentially affected higher-frequency components (> 0.8 Hz); reducing it in control animals without modifying it in CNH-exposed rabbits. CONCLUSIONS: These results suggest that CNH exposure shifts the autonomic balance of heart rate towards a sympathetic predominance without modifying resting heart rate or arterial blood pressure.
Subject(s)
Animals , Male , Rabbits , Vagotomy , Blood Pressure/physiology , Heart Rate/physiology , Hypoxia/physiopathology , Blood Glucose/physiology , Body Weight/physiology , Chronic Disease , Disease Models, Animal , HematocritABSTRACT
A study was conducted to examine the recovery of vagal activity after strenuous exercise based on changes in the magnitude of respiratory cardiac cycle variability, changes in the phase of this variability and the mechanism of the change. Six healthy male university students were studied for 5 h after exhaustive treadmill running. For cardiac cycle (RR) and blood pressure, the magnitude of respiratory variability and phase difference between respira-tory variability and respiration were measured. Respiratory period and tidal volume were maintained at 6 s and 21, respectively.<BR>1. The amplitude of respiratory RR variability decreased markedly after exercise and returned almost to normal after 2 h of recrvery. The phase of RR delayed with exercise, proceeded rapidly 2 h after exercise and progressively after that.<BR>2. The amplitude and phase of respiratory systolic blood pressure variability were almost stable before and after exercise.<BR>Based on these results, we conclude that vagal activity inhibited by strenuous exercise recovers about 2 h after the end of exercise. The delay in the phase of respiratory cardiac cycle variability with exercise may reflect inhibition of vagal activity.
ABSTRACT
Epidural anesthesia is a popular regional anesthetic technique for total hip replacement (THR). It s benefits are reduced blood loss, less need for transfusion, and decreased chance of deep vein thrombosis, and if necessary, it provides longstanding postoperative analgesia with small dose of epidural narcotics through indwelling epidural catheter. The wellknown cardiovascular effects are bradycardia and hypotension according to the degree of sympathetic blockade. These occur usually early in the anesthetic period and the course is benign and are easily treated. We report a case of sudden extreme bradycardia and hypotension during THR under epidural anesthesia that was not associated with hypoxemia, obvious respiratory depression, or systemic toxic reaction. It is concluded that the most likely cause would be a sudden large increase in vagal activity which results from marked reduction in venous return and inadequate oxygenation of myocardium with the assumption of prolonged iatrogenic hemodilution and undercorrected hypovolemia. The patient who receives epidural anesthesia should require constant monitoring and vigilance throughout all procedure.