Mechanism And Prevention Of Sudden Death And Arrhythmia Related To Military Stress

BACKGROUND:Stress is a feeling that's created when we react to particular events. It's the body's way of rising to a challenge and preparing to meet a tough situation with focus, strength, stamina, and heightened alertness. The events that provoke stress are called stressors, and they cover a whole range of situations—everything from outright physical danger to making a class presentation or taking a semester's worth of your toughest subject. A little of this stress can help keep you on your toes, ready to rise to a challenge. And the nervous system quickly returns to its normal state, standing by to respond again when needed. But when the stress become too seriously, it can wear out the body's reserves, leave a person feeling depleted or overwhelmed, weaken the body's immune system, and cause other problems. Military stress is some reactions of soldiers when they faced stress in the war. It has become one of the main causes of non-combat attrition. China's military stress research has clearly failed to that of foreign armies. The reports about the mechanism that military stress can hurt cardiovascular function, or cause arrhythmia were rare. More need to build a comprehensive response to military stress caused arrhythmia and sudden death prevention strategies.This research focuses on the relationship between acute stress and arrhythmia, and also focuses on the mechanisms how the stress lead to arrhythmias by using some data collected from the scene of military operations. Then we do some tests in the laboratory to study what role the sympathetic nerve play in stress on cardiac electrophysiology and arrhythmias.PURPOSE:The aim of this issue is to study whether the soldiers live in the military operations were hurt and what we can do to protect them. We compare the Holter data to syudy the incidence and the type of arrhythmia in the stress. And through application of ELISA, we make sure the changes of the NE, the AngⅡand the TNI in the guinea pigs' serum when these guinea pigs befall in acute stress. Record the AP, Ikr,Iks and Ikl in myocytes of guinea pigs some lived in stimulation and others lived in normal situation by using patch clamp. Medicate the metoprolol to prevent the arrhythmias. Make clear what theβ-blocker do to prevent injure by military stress and molecular mechanism of that effect.PART1 The changes on ECG of some Chinese soldiers because of the military stress TIME:2006 Mar.-2009 Dec.METHODS:Collected the Holter data of 103 servicemen in one Beijing military as a test group. At the same time, collected the Holter data of other 150 soldiers act as the control group. Compared the data of two groups. Made sure which index such as the incidence and the type of arrhythmia,HRV, TWA was different in two groups. All the peoples' Holter recording time were 22h-24h except one person. His schedule was 13h. The recording time of these two groups had no significant difference.RESULT:The incidence of atrial premature in the test group was 83.5%. It was lower than that of the control group which was 90%. In the test group, The average number of atrial premature was 80.6±6.4 times per person.But it was 24.1±11.6 in the control group. There were 9 persons who had paroxysmal atrial tachycardia in the test group, accounting for 8.74%. And in the control group, there were only 3 persons had paroxysmal atrial tachycardia, accounting for about 2%. The incidence of PVCs in the test group was 36.9%. it was 42.7% in the control group. The average number of PVCs was 823.5±64.4 times per person in the test group, while in the control group it was 59.4±41.8. In the test group.3 people had attacked ventricular tachycardia. Fortunately, no people in the control group had this terrible thing.The average heart rate in the test group was 76.1±8.8 times/min. It was faster than that of the control group. It was 69.2±6.3 times/min. In the time domain indices of HRV, RMSSD was higher in the test group, while several other indices, such as PNN50, SDANN, SDNN, and SDNNindex were all lower than that in the control group (P<0.05), They had statistically different.We analyzed TWA of both groups people. Chose the data when the heart rate had 60 consecutive sinus rhythm at lest in the early morning about 9:00. The results show:the positive rate of TWA in test group was 65.10%, significantly higher than 39.56% which was in the control group. And the threshold of TWA about the two groups were 205.6±7.4μV,167.7±8.3μV(P<0.01).CONCLUSION:In stressful situations, military persons had more atrial arrhythmia, ventricular arrhythmia than usual, but the severity of arrhythmia increased. Stress was one reason for arrhythmia happened or increased in our military persons.Stress provoked persons took part in training with sympathetic hyperactivity. inhibition of the vagus nerve and autonomic disorders. In Stress state, TWA-positive rate of soldiers participating in the training was higher. It increased the risk of getting arrhythmia. Military stress was one important reason to cause arrhythmias in the war.Part 2 Mechanism for stress-induced arrhythmiaMETHODS:Used noise combined with light as the stressor to stimulate guinea pigs 12 hours continuously. Manufacture stimulated animal models. Recorded ECG of laboratory animals, and applied the ELISA detection of acute stress conditions, guinea pigs serum norepinephrine (NE), angiotensinⅡ(ANGⅡ) and cardiac troponinⅠ(TNI) content.Isolated guinea pigs ventricular myocytes by using enzymatic method. Selected guinea pigs single ventricular myocyte which was in good condition and calcium-resistant. Established of whole-cell patch clamp mode. Applicated Iso 1.0μmol/L as a tool for medicine, to establish a cell model of acute stress. Recorded AP, Ikr, Iks, Ikl and other current of guinea pig single ventricular myocyte by patch. Analyzed mechanisms in ion channel for stress-induced arrhythmia.RESULTa Animal model of acute stress by using guinea pigs were established and guinea pig single ventricular cell was isolated.Signs of Stress:guinea pigs who were experienced stress may notice some of the following signs, sadness or depression, hair became dry and upright, curl up in the cage corner, kept a low voice call and developt eating disorders.The average heart rate of stressed guinea pigs was faster than the control ones. During the observation period, in the control group there was no arrhythmia. But six guinea pigs in the test group had different types of arrhythmia.Every type of arrhythmia did ont last long time. The results of ELISA showed NE, ANGII and TNI in serum of stressed guinea pigs. Their contents were 965.76±18.92 pg/ml,98.18.±11.06pg/ml and 2.71±0.32 ug/L. All of them were significantly higher than them in the control group serum. And in the control group serum, they were 423.58±7.46pg/ml,35.87±2.69pg/ml and 0.24±0.05 ug/L. Suggest that in stress situations, the incidence of arrhythmia animals increased significantly, NE and NGII were also significantly increased and led to TNⅠincreased.b Record AP in stressed guinea pigs single ventricular myocytes Test temperature was about 25℃, using 1.0μmol/L Iso and1.0μmol/L Iso+1.0μmol/ L Met to perfuse in the cell pool. After that, APD of the single cell had changed. But the change was too little. At 37℃, 1.0μmol/L Iso shorted the APD of single ventricular myocyte significantly. APD50 of guinea pig ventricular myocytes in the control group were shorted from 245.1±12.3ms to 207.6±9.4ms, and APD90 of them were shorted from 325.8±21.5ms 277.3±15.7ms (P<0.01, n=10). Used 1.0μmol/L Iso+1.0μmol/L Met, APD of cells had little change, compared with the control group, the change had no significant difference.c Effects on Ikr of guinea pigs single ventricular myocytes by IsoAt 25℃,1.0μmol/L I so had almost no effect on IKr,tail, while at 37℃,Ikr,tail increased significantly after using 1.0μmol/L Iso. When the cell depolarized to+70 mV,IKr,tail current density was increased from 40±3.4 pA/pF to 83.4±6.7 pA/pF (P<0.01, n=12) with Iso, while perfused with 1.0μmol/L Iso+1.0μmol/L Met,IKr,tail current density was increased to 49.1±2.9 pA/pF only, and had no significant difference with the control group, (P>0.05, n=10). Furthermore, after perfusion of 1.0μmol/L Iso, the current at all potentials were increased significantly. The current density changed more when the potential shift more. It mean the Iso was certain voltage-dependent. All current density changed, but too small.1.0μmol/L Iso made the channel half-inactivation voltage (V0.5) shifted to hyperpolarization, from -47.5±7.2 pA/pF as same as the control group moved to -71.1±5.23 pA/pF, but did not change the curve slope (k). Used 1.0μmol/L Iso +1.0μmol/L Met, neither V0.5 or k changed much. Compared with the control group,1.0μmol/L Iso made the current recovered after quick inactivation increased. The recovery time constant are reduced at all test voltages. At-30 mV the time constant shorted from 1.34±0.21 s to 0.52±0.08 s.1.0μmol/L Iso+1.0μmol/L Met, changes of both amplitude and constant of the recovery current were not significant. All drugs did not affect the rectification characteristics of channel.d Effects on Iks of guinea pigs single ventricular myocytes by Iso At 37℃, after the application of 1.0μmol/L Iso, IKs,step and IKs,tail current density increased significantly.IKs,step increased from 92.3±10.2 pA/pF to 173.1±16.2 pA/pF (P< 0.01, n= 10).Perfused 1.0μmol/L Iso+1.0μmol/L Met,IKs,tail changed little from 22.3±2.5 pA/pF to 28.4±5.2 pA/pF (P>0.05, n=10). The original current map showed, Iso increased IKs,step in the early depolarizing time (1s) much stronger than the end (4 s) time. From theⅠ-Ⅴcurve of the current, we could see the current was activated at about-20 mV. The tail current increased, and showed significant outward rectification accompanied with the stimulation pulse moved. The effects were became greater after applicated with 1.0μmol/L Iso.Its effects were strong voltage dependent. While after perfused with 1.0μmol/L Iso+1.0μmol/L Met, IKs, tail current density were also increased at all potentials, but the extent of increase were small.The steady-state activation curve of IKs in all ventricular myocytes had no significant difference, V0.5 and k wre same (P>0.05). Compared with the control group, 1.0μmol/L Iso increased the constant of the channel inactivation time. And this effect became stronger while the voltage shifted higher. At-20 mV, the inactivation time constant prolonged from 475±35 ms to 2015±76 ms (P<0.01, n=10). 1.0μmol/L Iso+1.0μmol/L Met prolonged the time constant to 502±31ms only, seemed no significant difference. 1.0μmol/L Iso increased recovery current density after chronic inactivation in every test voltage. And with voltage positive shifting, the scope of current density increased obviously. At+60 mV, the restoration current density increased from 63.2±5.9pA/pF to 180.2±13.4 pA/pF(P<0.01, n=10).e Effects on Ikl of guinea pigs single ventricular myocytes by IsoAt 37℃, used local perfusion to add 1.0μmol/L Iso and 1.0μmol/L Iso+1.0μmol/ L Met in the cell pool. Three groups of IKl current density were 85.1+0.5 pA/pF,83.9±0.3pA/pF和86.7±0.7 pA/pF when the membrane potential was-140 mV. They had no significant difference.Ⅰ-Ⅴcurve showed voltage-dependent of the three groups had no significant difference.CONCLUSIONIso shorted APD50 and APD90 in guinea pig single ventricular myocytes, had stronger effects on the APD90. But for APA and RMP Iso had no effect.Iso increased IKr, tail of single guinea pig ventricular myocyte, It was voltage-dependent. This increase was significantly reduced while applicated both Iso and Met.Effects on Ikr,tail of guinea pigs single ventricular myocytes by Iso were related with the temperature. At room temperature Iso had no functions. On the contrary, it had effects at 37℃. This effect was achieved mainly by reducing the channel steady-state inactivation and accelerating the channel inactivation recovery. Iso had little effects on IKr,tail of the steady-state activation, fast inactivation constant, the voltage dependence and rectification.The effects on both IKs,step and IKs,tail by Iso were increased, and had characteristics of voltage-dependent. The effects of drugs on IKs,step were stronger in earlier depolarizing period than later.Iso increased IKr,tail was mainly due to prolong channel inactivation time constant, stimulated the channel's slow inactivation recovery, but had little effects on the steady-state activation, steady-state inactivation.Iso had no influence on the IKl.