Clinical Study Of Treadmill Exercise Stress Echocardiography For Left Ventricular Function Assessment In Patients With Acute Myocardial Infarction Treated With Primary Percutaneous Intervention

Objective: To investigate the left ventricular function changes in patients with acute ST-segment elevation myocardial infarction(STEMI)detected by treadmill exercise stress echocardiography(TESE)12 months after the first emergency percutaneous coronary intervention(PCI).Methods: A total of 34 patients with initial STEMI and 12 months after primary PCI who were admitted to our hospital from January 2017 to December 2018 were enrolled as the PCI group,33 healthy adults with negative coronary examination were enrolled as the normal control group.The PCI group was divided into non-target vessel segments subgroup suppled by non-occluded coronary artery and target vessel segments subgroup suppled by occluded coronary artery according to the 17-segments left ventricular model recommended by American Heart Association.TESE were performed in control group and PCI group 12 months after PCI.Echocardiographic imgings were obtained and assessed including 3 cardiac cycles of parasternal left ventricle long axis,apical 4 chamber(AP4C),apical 2 chamber(AP2C)and apical 3 chamber(AP3C)views before and postexercise.The analyzed paremeters include the thickness of interventricular septum and left ventricular posterior wall,left ventricular end-diastolic diameter(LVEDD),left ventricular end-diastolic volume(LVEDV)and end-systolic volume(LVESV),left-ventricular ejection fraction(LVEF),Left atrial volume index(LAVI),mitral valvular early diastolic and late diastolic velocity(E,A),deceleration time of mitral valve E wave(DT),the peak velocity of tricuspid regurgitation(TR),and early diastolic velocity of mitral annulus(e')(Mean values of the velocities of interventricular septum and lateral wall),E/e',E/A,e' reserve value and LVEF reserve value.QLab 10.0 software was used to measure the left ventricle globle longitudinal strain(GLS),the systolic longitudinal strain(SLS)of 17 segments,GLS reserve value and SLS reserve value in all subjects before and after exercise.Exercise tolerance,exercise time,clinic symptoms,and the changes of heart rate(HR),blood pressure and electrocardiogram(ECG)were recorded.The clinical data of the subjectswere collected.SPSS version 23.0 was used for analysis,statistical significe was set at P<0.05.Results:(1)The PCI group had a higher prevalence of smoking,body mass index,hypertension,diabetes,hyperlipidemia,medication,and increased serum myocardial biochemical indicators(P<0.05).(2)The systolic blood pressure(SBP)was higher at resting state in the patients of the PCI group(P<0.05),there were no significant differences of postexercise SBP,diastolic blood pressure,HR,exercise tolerance,exercise duration time,abnormal electrocardiographic changes and clinic symptoms between the two groups(P>0.05).(3)The thickness of interventricular septum in the PCI group was thicker and the postexercise LVESV was lager than that in the control group,the difference were statistically significant(P<0.01).No significance differences were found in thickness of LVPW,LVEDD,LVEDV and LVESV at resting state between the two groups(P>0.05).(4)The GLS and LVEF at resting state were not different significantly between the two groups(P>0.05);The GLS,LVEF and LVEF reserve after exercise were lower in PCI group than that in the control group(P<0.05),the GLS and LVEF were obviously increased frome rest to peak stress in the two groups(P<0.01),but more higher in the control group than that in PCI group(P<0.05).The resting SLS,peak SLS and SLS reserve had a gradually declining trendency in control group,non-target vessel segments and target vessel segments in PCI group.The resting SLS was lower in target vessel segments subgroup than that in non-target vessel segments subgroup and in control group(P<0.05);the postexercise SLS was lower in target vessel segments subgroup than in control group(P<0.05).There was no statistically significant difference in SLS before and postexercise between non-tager vessel segments sudgroup and control group(P>0.05).The postexercise SLS of the three segments groups were significantly higher than that before exercise(P<0.01).(5)E/e' ratio of mitral valve at resting and peak state was normal in control group.There were 7 patients in PCI group with elevated resting E/e' ratio.Compared with those with normal E/e' ratio,the patients with elevated resting E/e' ratio had a higher A,lower e' at resting and peak state(P<0.05).The variable e' was significantly higher at stress state than resting state in all subjects,but the increase in the control group was higher than that in the PCI group(P< 0.01).(6)Age,resting and postexercise E/e' were negatively associated with exercise tolerance(P<0.05).There was no correlation between LVEF,GLS,e' and exercise tolerance.(7)The parameters measured in this study such as strain had a good repeatability within and between observers.Conclusions:(1)The postexercise changes of heart rate and blood pressure in patients with STEMI and12 month after primary PCI were normal physiological reaction.(2)The overall systolic function reserve of left ventricle in patients with STEMI after primary PCI may be decreased subclinically,which was potenially related to the incomplete systolic function recover of ischemia myocardium supplied by target vessel.(3)Left ventricular early diastolic function is often decreased in patients with STEMI after primary PCI,and may be obvious impaired in some patients,the diastolic dysfunction is more obvious than systolic function impairment.(4)The E/e' ratio of mitral valve was negatively correlated with exercise tolerance in patients with STEMI after primary PCI,suggesting that clinical symptoms such as decreased exercise tolerance may be partially associated with left ventricular diastolic dysfunction.