***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVE : To investigate whether ischaemic preconditioning could reduce myocardial injury , as manifest by troponin T release , in patients undergoing elective coronary artery bypass surgery . DESIGN : R and omised controlled trial . SETTING : Cardiothoracic unit of a tertiary care centre . PATIENTS : Patients with three vessel coronary artery disease and stable angina admitted for first time elective coronary artery bypass surgery were invited to take part in the study ; 33 patients were r and omised into control or preconditioning groups . INTERVENTION : Patients in the preconditioning group were exposed to two additional three minute periods of myocardial ischaemia at the beginning of the revascularisation operation , before the ischaemic period used for the first coronary artery bypass graft distal anastomosis . MAIN OUTCOME MEASURE : Serum troponin T concentration at 72 hours after cardiopulmonary bypass . RESULTS : The troponin T assays were performed by blinded observers at a different hospital . All patients had undetectable serum troponin T ( < 0.1 microgram/l ) before cardiopulmonary bypass , and troponin T was raised postoperatively in all patients . At 72 hours , serum troponin T was lower ( P = 0.05 ) in the preconditioned group ( median 0.3 microgram/l ) than in the control group ( median 1.4 micrograms/l ) . CONCLUSIONS : The direct application of a preconditioning stimulus in clinical practice has been shown , for the first time , to protect patients against irreversible myocyte injury OBJECTIVE To test the hypothesis that short periods of ischemia may increase the myocardial protection obtained with intermittent crossclamping of the aorta . METHODS In the control group ( 18 patients ) , surgery was performed with  systemic hypothermia at 32 degrees C and intermittent crossclamping of the aorta . Extracorporeal circulation was used . In the preconditioning group ( 17 patients ) , 2 crossclampings of the aorta lasting 3min each were added prior to the intermittent crossclamping of the conventional technique with an interval of 2min of reperfusion between them . Blood sample s for analyses of pH , pCO2 , pO2 , sodium , potassium , calcium , and magnesium were obtained from the coronary sinus at the beginning of extracorporeal circulation ( time 1 ) , at the end of the first anastomosis ( time 2 ) , and at the end of extracorporeal circulation ( time 3 ) . RESULTS No difference was observed in the results of the 2 groups , except for a variation in the ionic values in the different times of blood withdrawal ; sodium values , however , remained stable . All patients had a good clinical outcome . CONCLUSION The results of intermittent crossclamping of the aorta with moderate hypothermia were not altered by the use of ischemic preconditioning Background —Ventricular fibrillation ( VF ) and tachycardia ( VT ) are the common and potential life-threatening complications after CABG . Ischemic preconditioning ( IP ) has been proved effective in reducing ischemia reperfusion arrhythmia in animals and humans . Whether IP is effective in suppressing postoperative VF/VT in patients with CABG has not been studied . Methods and Results —Eighty-six patients with CABG with stable and unstable 3-vessel disease were equally r and omly assigned into an IP and a control group . The patients who received IP received 2 periods of 2-minute ischemia followed by 3-minute reperfusion . Twenty-four-hour electrocardiographic data were collected . IP result ed in fewer cases of VF after declamping ( 48.8 % versus 79.1 % in IP and control , P = 0.004 ) and a shorter VF period ( 2.28±0.44 versus 4.41±0.51 minutes , P = 0.002 ) . The episodes of VT were significantly reduced in patients in the IP group during early reperfusion and 24 hours after reperfusion ( 0.65±0.16 versus 3.71±0.46 , P = 0.000 and 0.07±0.04 versus 2.12±1.41 , P = 0.002 , respectively ) . De novo sustained VT occurred in 3 control patients as against none in the IP group after surgery . As a result , IP significantly curtailed the mechanical ventilation period and reduced the need for inotropes . Conclusions —IP significantly reduced postoperative VF/VT  in patients with CABG with 3-vessel disease . Suppression of VT during early reperfusion and 24 hours after reperfusion suggests early and delayed IP phenomena in patients undergoing CABG surgery UNLABELLED Ischaemic preconditioning , with brief periods of ischaemia separated by reperfusion , increases myocardial resistance to infa rct ion . In addition , preconditioning leads to preservation of myocardial adenosine triphosphate ( ATP ) during ischaemia . We propose that ischaemic preconditioning may share fundamental similarities with intermittent aortic cross-clamping utilised during aorto-coronary bypass surgery . The aim of this study was to test the hypothesis that controlled aortic cross-clamping is a form of preconditioning using conservation of ATP as the end point . Patients r and omised to the preconditioned group ( preconditioned , n = 10 patients ) , received a preconditioning stimulus of two 3-min periods of cross-clamping separated by 2 min of reperfusion prior to an ischaemic insult of 10 min ischaemia and ventricular fibrillation . In the control group ( control , n = 10 patients ) hearts received 10 min cross-clamping with fibrillation without prior preconditioning .  Myocardial ATP , creatine phosphate ( CP ) , and lactate were determined from biopsy specimens taken at the onset of cardiopulmonary bypass ( A ) , at the end of preconditioning ( B ) , and at the end of 10 min of ischaemic insult ( C ) . RESULTS expressed as mean + /- SE ( mumol/g dry weight ) . Preconditioning result ed in a significant depletion of the myocardial ATP content ( preconditioned , B : 11.7 + /- 0.9 vs A : 19.8 + /- 1.4 ; P < 0.01 ) . Furthermore 10 min of ischaemia result ed in a significant depletion of ATP in the control patients ( control , C : 7.2 + /- 0.3 vs B : 19.5 + /- 1.2 ; P < 0.005 ) . ( ABSTRACT TRUNCATED AT 250 WORDS OBJECTIVE To study the relationship between ischemic preconditioning ( IP ) and lactate production and their impact on coronary artery bypass graft surgery patients . DESIGN Prospect i ve , r and omized , controlled study . SETTING University hospital . PARTICIPANTS Eighty 3-vessel disease coronary artery bypass graft surgery patients with stable and unstable angina pectoris . INTERVENTIONS The IP patients were preconditioned with 2 periods of 2-minute ischemia followed by 3-minute reperfusion before aortic cross-clamping . MEASUREMENTS AND MAIN RESULTS The cardiac index ( CI ) after surgery was significantly higher in the IP group than in controls among stable patients ( p = 0.013 ) . IP was not effective in CI recovery in unstable patients . The baseline values of lactate production were 11.6 % , 20.3 % , -7.0 % , and -2.9 % in stable IP , stable control , unstable IP , and unstable control patients . Compared with baseline , lactate production increased significantly after the IP protocol ( 39.0 % and 47.5 % in the stable and unstable patients ) , and operation ( 47.5 % , 31.7 % , 35.4 % , and 35.6 % in stable IP , stable control , unstable IP , and unstable control patients ) but not after 10 minutes of cardiopulmonary bypass ( 29.7 % and 19.0 % in the stable and unstable patients ) . There were no differences among the groups in lactate production after the operation . Lactate production after the IP protocol was negatively associated with CI recovery after surgery in the IP patients ( p = 0.026 ) . CONCLUSION The IP effects do not include modulation of lactate production . IP induces lactate production , but it seems not to be involved in the triggering process OBJECTIVE To investigate the interrelationship of free radicals ( FRs ) , ischemic preconditioning ( IP ) , and hemodynamic function in coronary artery bypass graft ( CABG ) patients . DESIGN Prospect i ve , r and omized , and controlled clinical study . PATIENTS Forty CABG patients were r and omized into an IP group ( n = 20 ) and a control group ( n = 20 ) . INTERVENTION The IP group was preconditioned with two cycles of two-min ischemia followed by 3-min reperfusion before cross-clamping . MEASUREMENT AND RESULTS FR content in coronary sinus blood was measured directly using alpha-phenyl-N-tert-butylnitrone-electron spin-trapped spectroscopy . A small amount of FRs was generated after the IP protocol ( 5.6 % above the baseline ) but not in control subjects . A larger amount was generated 10 min after declamping in both groups ( 8.4 % in IP protocol and 7.7 % in control subjects ) . Hemodynamic function recovered better in the IP group at 1 h and 6 h after declamping . There was a significant negative correlation between FR generation after declamping and left ventricular stroke work index ( LVSWI ) at 1 h and 6 h after declamping ( r = -0.71 and - 0.59 , respectively ) in the control subjects but not in the IP group . There was a significant positive correlation between FR generation after the IP protocol and cardiac index at 1 h and 6 h ( r = 0.50 and 0.61 , respectively ) and LVSWI at 1 h and 6 h ( r = 0.56 and 0.54 , respectively ) after declamping in the IP group but not in the control subjects . CONCLUSION FR generation after the operation correlates with ventricular functional depression in CABG patients . IP protects the stunning heart but does not alter FR generation . The association of better hemodynamic recovery after CABG with FR generation during the IP period suggests that FRs might act as one of the triggers for IP OBJECTIVES We intended to investigate whether ischemic preconditioning ( IP ) enhances myocardial performance in patients who undergo off-pump coronary artery bypass grafting ( CABG ) . DESIGN A controlled , r and omized , prospect i ve study . SETTING A university hospital . PATIENTS Thirty-two patients with left anterior descending coronary artery ( LAD ) or two-vessel heart disease ( including LAD ) who were to undergo off-pump CABG were r and omized into an IP group and a control group . INTERVENTIONS IP was induced by occluding the LAD twice for a 2-min period followed by 3-min LAD reperfusion before bypass grafting of the first coronary vessel . MEASUREMENTS AND RESULTS Registration included hemodynamic data from the peripheral artery and the pulmonary artery , and the measurement of cardiac troponin I ( CTnI ) and creatine kinase isoenzyme MB ( CK-MB ) values . IP result ed in a complete recovery of the mean stroke volume index ( SVI ) after the operation . In the control subjects , the mean SVI showed a significant reduction postoperatively ( p = 0.039 ) . On the first postoperative day , the increase in the mean heart rate ( HR ) was also significantly lower in the IP patients . The CTnI level was statistically significantly lower in the IP group ( p = 0.043 ) , and IP patients tended to have a smaller CK-MB release after surgery ( not significant ) . The duration of mechanical ventilation , the length of stay in the ICU , and the use of inotropic medication did not increase after the IP protocol . CONCLUSIONS Two cycles of regional 2-min IP in the LAD , followed by 3 min of reperfusion , proved to be applicable and safe in patients undergoing off-pump myocardial revascularization , it tended to decrease the immediate myocardial enzyme release , it prohibited the postoperative increase in HR , and it enhanced the recovery of SVI BACKGROUND Our previous work has shown that preconditioning can promote the recovery of cardiac function in patients having an open heart procedure . Because preconditioning is regarded as the most powerful form of endogenous myocardial protection , we tested the hypothesis that preconditioning protects against myocardial ischemia-reperfusion injury in patients undergoing prolonged cold crystalloid cardioplegic arrest . METHODS Thirty patients who had rheumatic heart disease and required both aortic and mitral valve replacement were studied . Patients were r and omly divided into two equal groups . Preconditioning was accomplished using two cycles of 2-minute occlusion of the vena cava and aorta followed by 3 minutes of reperfusion under cardiopulmonary bypass . All hearts were arrested with 4 degrees C St. Thomas ' Hospital cardioplegic solution .  Myocardial protective effects were assessed by changes in myocardial levels of adenosine triphosphate , electrocardiographic activity , leakage of myocardial enzymes , and myocardial contractility . RESULTS The adenosine triphosphate content in ischemic myocardium was higher in the preconditioning group than in the control group ( p < 0.05 90 minutes after ischemia 
    Output:
    
The effect disappeared when the analyses were restricted to patients receiving ICCF .