Ventricular Excitability and Refractoriness in the Hypothermic Dog

1957 ◽  
Vol 189 (3) ◽  
pp. 591-595 ◽  
Author(s):  
E. T. Angelakos ◽  
E. G. Laforet ◽  
A. H. Hegnauer
Keyword(s):  
Heart Rate ◽  
Ventricular Fibrillation ◽  
Response Latency ◽  
Refractory Period ◽  
Cardiac Cycle ◽  
Significant Alteration ◽  
Entire Cardiac Cycle ◽  
Refractory Periods ◽  
Rate Of Recovery ◽  
Increased Susceptibility

Measurements of ventricular exctiability through the entire cardiac cycle of the dog under progressive hypothermia show that the ventricular refractory period (measured as absolute, total or functional refractory period) is greatly prolonged. This effect is not secondary to the changes in heart rate since normothermic animals with surgical A-V block having heart rates similar to those obtained under hypothermia do not show any great prolongation in the ventricular refractory period. At heart temperatures ranging from 38° to 23°C there is no significant alteration in the diastolic excitability of the ventricle. The rate of recovery of diastolic excitability and the response latency were greatly prolonged as reflected in the marked increase in the duration of the relative and functional refractory periods. It is suggested that the increased susceptibility of the hypothermic myocardium to ventricular fibrillation may be related to the observed changes in the rate of recovery of excitability.

scholarly journals Late, but Before Schedule-A Bigeminal Rhythm with Blocked Premature Junctional Beats

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Daniel Manna
Keyword(s):  
Heart Rate ◽  
Refractory Period ◽  
Cardiac Cycle ◽  
Ecg Monitoring ◽  
P Waves ◽  
Abrupt Decrease ◽  
Ambulatory Ecg ◽  
Ambulatory Ecg Monitoring ◽  
Ectopic Beats ◽  
Activation Site

Premature supraventricular ectopic beats are common findings in ambulatory ECG monitoring. Blocked ectopic beats may occur if the premature beat coincides with the refractory period of the downstream conductive tissues. We report of an uncommon, symptomatic bigeminal rhythm which resulted in an abrupt decrease of the heart rate because of blocked P waves. The blocked P waves appeared uncommonly late in the cardiac cycle because of a very His-near activation site. For anatomic reasons treatment was difficult and the patient received a pacemaker.

Low vagally-mediated heart rate variability and increased susceptibility to ventricular arrhythmias in rats bred for high anxiety

2014 ◽  
Vol 128 ◽  
pp. 16-25 ◽  
Author(s):  
Luca Carnevali ◽  
Mimosa Trombini ◽  
Gallia Graiani ◽  
Denise Madeddu ◽  
Federico Quaini ◽  
...  
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Ventricular Arrhythmias ◽  
High Anxiety ◽  
Increased Susceptibility

Blood pressure, heart rate, and adrenal catecholamines prior to ventricular fibrillation

1961 ◽  
Vol 201 (1) ◽  
pp. 109-111 ◽  
Author(s):  
Noel M. Bass ◽  
Vincent V. Glaviano
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Ventricular Fibrillation ◽  
Coronary Occlusion ◽  
Marked Decrease ◽  
Mean Blood Pressure ◽  
Plasma Adrenaline ◽  
Acute Coronary Occlusion ◽  
Before And After

Heart rate, mean blood pressure, adrenal blood flow, and adrenal plasma adrenaline and noradrenaline were compared before and after ligation of the anterior descending coronary artery in dogs anesthetized with chloralose. One group of 12 dogs responded to acute coronary occlusion with a sudden and marked decrease in mean blood pressure (mean, 31%) and heart rate (mean, 18%) followed by an early onset (mean, 227 sec) of ventricular fibrillation. Another group of nine dogs responded with slight decreases in mean blood pressure (mean, 13%) and heart rate (mean, 5%), during which time ventricular fibrillation occurred late (mean, 30 min) or not at all. While the two groups were statistically different in mean blood pressure and heart rate, the minute output of adrenal catecholamines in either group was not found to be related to the early or late occurrence of ventricular fibrillation.

scholarly journals Cardiac workload of dressers in underground manual coal mines

1970 ◽  
Vol 32 (2) ◽  
pp. 11-17 ◽  
Author(s):  
R Saha ◽  
A Samanta ◽  
NC Dey
Keyword(s):  
Heart Rate ◽  
Physiological Stress ◽  
Coal Mines ◽  
Recovery Process ◽  
Technological Advancement ◽  
Institute Of Medicine ◽  
Cardiac Strain ◽  
Rate Of Recovery ◽  
Ergonomic Interventions ◽  
Cardiac Cost

Introduction: Occupational disorders invite absenteeism amongst the miners. Though rapid technological advancement has happened, yet assessment of cardiac workload was largely ignored in underground coal mines in India. Methods: Physiological stress was evaluated in terms of working heart rate, net cardiac cost and relative cardiac cost. Heart rate was measured during their course of work by heart rate monitor at the coal face. Recovery heart rates and environmental heat load were also assessed. Results: Heart rate was found to be 117 and 122 beats/min respectively in first and second spell. NCC (49.7 and 54.8 beats /min) and RCC (47% and 52%) exhibit significant variations between spells, whereas rate of recovery had been very poor amongst the workers who regularly exceeded recommended levels of cardiac strain indices. The nature of work depicted it as a heavy job although recovery trend categorizes it heavier than that. ET and WBGT were above the recommended limits as per the guidelines of WHO and ACGIH. Conclusions: High physiological demand of the job with towering heat stress was found to hinder the recovery process and may cause deleterious impacts on the workers. Ergonomic interventions were highly felt towards job organization and up gradation of environmental conditions. Keywords: Coalmines; dressers; workload DOI: http://dx.doi.org/10.3126/joim.v32i2.4938 Journal of Institute of Medicine, August, 2010; 32: 11-17

scholarly journals Optimal Length of Heart Rate Variability Data and Forecasting Time for Ventricular Fibrillation Prediction Using Machine Learning

2021 ◽  
Vol 2021 ◽  
pp. 1-5
Author(s):  
Da Un Jeong ◽  
Getu Tadele Taye ◽  
Han-Jeong Hwang ◽  
Ki Moo Lim
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Ventricular Fibrillation ◽  
World Health ◽  
Artificial Neural Network Classifier ◽  
Life Threatening ◽  
Causes Of Mortality ◽  
Health Organization ◽  
Forecast Time ◽  
Data Length

Ventricular fibrillation (VF) is a cardiovascular disease that is one of the major causes of mortality worldwide, according to the World Health Organization. Heart rate variability (HRV) is a biomarker that is used for detecting and predicting life-threatening arrhythmias. Predicting the occurrence of VF in advance is important for saving patients from sudden death. We extracted features from seven HRV data lengths to predict the onset of VF before nine different forecast times and observed the prediction accuracies. By using only five features, an artificial neural network classifier was trained and validated based on 10-fold cross-validation. Maximum prediction accuracies of 88.18% and 88.64% were observed at HRV data lengths of 10 and 20 s, respectively, at a forecast time of 0 s. The worst prediction accuracy was recorded at an HRV data length of 70 s and a forecast time of 80 s. Our results showed that features extracted from HRV signals near the VF onset could yield relatively high VF prediction accuracies.

Respiration-dependent Movements of the Column of Stylidium gvaminifolium

1981 ◽  
Vol 8 (1) ◽  
pp. 45 ◽  
Author(s):  
G.P Findlay ◽  
N Findlay
Keyword(s):  
Refractory Period ◽  
Angular Displacement ◽  
Metabolic Energy ◽  
Original Position ◽  
Firing Process ◽  
Mechanical Stimuli ◽  
Anaerobic Conditions ◽  
Absolute Refractory Period ◽  
Refractory Periods ◽  
Graded Responses

The column of the trigger plant, Stylidium graminifolium, when fully set responds to mechanical stimuli by flipping through an angle of about 4 radians in a fast firing movement lasting about 15-30 ms, and then slowly resetting to its original position in about 400 s. After resetting there is an absolute refractory period of about 500 s during which no further response to stimuli can be initiated, followed by a relative refractory period when graded responses increasing in rate and magnitude with time can be obtained. The resetting movement and the process, occurring during the refractory period, allowing subsequent firing to occur, are inhibited when the air surrounding the column is replaced by nitrogen. The firing movement, however, is not affected by these anaerobic conditions. Thus the firing movement is caused by passive physical forces, rapidly utilizing potential energy from a store built up during the previous resetting and refractory periods. Removal of the labellum, which the column touches when set, causes the column to oscillate with amplitude of about 3-3.5 radians and period of 1-2 ks. When the column is held at a constant angular displacement it develops an oscillatory torque with similar period. These oscillations are inhibited at all stages of the cycle by anaerobic conditions. It appears that the oscillatory behaviour is not a slowed-down firing process followed by normal resetting, but is linked throughout the cycle to the metabolic energy supply.

Changes in selected parameters of health and physical fitness following a sixteen-week deployment at sea

1994 ◽  
Vol 80 (1) ◽  
pp. 22-29
Author(s):  
P W King-Lewis ◽  
A J Allsopp
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Physical Fitness ◽  
Exercise Group ◽  
Lower Percentage ◽  
Resting Heart Rate ◽  
Percentage Body Fat ◽  
Cardiac Recovery ◽  
Test Occasion ◽  
Rate Of Recovery

AbstractThe effects of 16 weeks at sea upon selected parameters of health and physical fitness were investigated in 30 male volunteers (from a total crew of 48 men) prior to, and immediately following deployment. The 30 subjects were assigned toeither an exercise group, ‘Ex’ (n=12), or a non-exercising group, ‘Nil ex ’ (n = 18), according to their reported participation in vigorous training or sports. Body mass index (BMI), calculated from height and weight, revealed that prior to deployment 13 of the 30 subjects (two in the Ex group) had a BMI over 25 kg.m−2 (i. e. overweight), and a further three subjects (all ‘non-exercisers’) had values of 30 kg.m−2 or more (obese). In addition, the diastolic blood pressure of two subjects was in excess of 95 mmHg and five subjects had resting heart rates above 89 beats per minute. Retrospective comparisons between the Ex and Nilex groups revealed a significantly lower percentage body fat (P<0.01) and a faster rate of cardiac recovery (P<0.05) following a standardised bout of exercise in the Ex group, albeit that these individuals were significantly younger (mean age of 24 years) than those in the Nilex group (32 years). Following deployment, in the Nilex group, comparisonof pre- and post values showed that resting heart rate was elevated (P<0.01) on return from sea. Similarly, in the Nilex group heart rate while performing the standardised exercise about was also elevated (P<0.05) on the second test occasion. In the Ex group, heart rate measures during and foJlowing exercise indicated a significantly slower rate of recovery (P<0.05) on the second test occasion.

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