Clinical Study Of IVUS In Optimizing The Outcome Of Stent Implantation Of Atherosclerotic Stenosis Proximal To Coronary Myocardial Bridge

Background:Due to the hemodynamical change,the proximal coronary artery segment of myocardial bridge tends to develop atherosclerostic stenosis.Studies have indicated that stent implantation on these stenositc lesions lead to higher incidence of major adverse cardiac events(MACEs)than those without myocardial bridge.The possible explanation is that the stent extended into the myocardial bridge or,on the other side,the stent did not fully cover the stenostic lesions.So,how to optimize the stent implantation in this situation is a key question the interventionlists meet in clinical practice.Intravascular ultrasound(IVUS)is more accurate in the diagnosis of myocardial bridge than coronary angiography.IVUS study found that 34% stent implantation guided by angiography was not in the exact position,which result in more MACEs.This indicates that IVUS may be more helpful and can improve the outcome of stent implantation in this setting.Objective:Based on our previous studies,we designed this study in order to confirm the hypothesis that use of IVUS can optimized the outcome of coronary angiography guided stent implantation for stenostic lesions proximal to myocardial bridge.Methods:From July 2013 to July 2018,all patients who were admitted for acute coronary syndrome(ACS)undergoing interventional therapy were consecutively screened.Patients with both stenostic lensions of over 70% proximal to myocardial bridge and evidence of myocardial ischemia,single vessel disease,or less than 50% stenoses in other coronary artery,were included into this study.The basic clinical parameters including laboratory data were collected within 24 hours of admission.Selective coronary angiography was performed at the third to fifth day.If angiography found systolic compression and diastolic decompression of coronary artery segments(milking effect),myocardial bridge was diagnosed and the extent of compression was calculated.If there was over 70% of coronary artery stenosis proximal to myocardial bridge and evidence of myocardial ischemia(ECG,UCG or SPECT),stent was implanted under the guidance of coronary angiography(angiography guided stent implantation AGSI)or under the guidance of intrvascular ultrsound(IVUS guided stent implantation IGST).Guidewire protection was performed if main diagnal was related.When necessary,two stent technique(culotte or CRUSH)was used.If side branch was seriously compressed after one stent strategy,provisional T procedure(TAP)was used.For IVUS guided stent implantation,IVUS was used to detect the exact begining positon of myocardial bridge and the stenosis lesion,the reference vessel diameter to guide stent size and its placement.Stent was placed not only avoid extension into myocardial bridge,but also fully cover the stenostic lesion.The procedure was finished if there was not residual stenosis of over 10% and no serious side branch compression,grade 3 TIMI blood folw.The clinical data such as gender,age,BMI,history of dibetes mellitus,hypertension,lipid abnormality,smoking,the serum level of total cholesterol,low density lipoprotein cholesterol,triglycerides,estimated glomerular filter rate(eGFR)and alanine aminotransferase,left ventricle end diastole diameter(LVEDD),ejection fraction(LVEF)were all collected.Procedure related parameters such as compression of myocardial bridge,extent of stenosis of target lesion and related diagnal pre and post procedure,total stent length,diameter,strategy,contrast use were also recorded.Major adverse cardiac events such as angina,acute myocardial infarction,intrastent thrombosis,heart failure,sudden death were followed up to 6 months.Coronary angiography was repeated at 6-12 month for all patients.IVUS was performed for the AGSI patients at 6-12 follow up.Intrastent qnd intrasegment late lumen diameter loss was respectively calculated.Diameter stenosis of 30-50% was defined intimal proliferation while over 50% diameter stenosis was defined as restenosis.Results:Totally,one hundred and twenty four patients was included into this study,with 66 patients in AGSI and 58 in IGSI.The basic demographic data such as diabetes,family history,level of TC and LDL-C was significantly different between the two groups,while all the rest were not different.Angiographically,the extent of myocardial bridge compression,stenosis of proximal coronary segment,the length of stenostic lesion,diagnal stenosis were all comparable.Two stent strategy was less used in IGSI than AGSI(1.8% vs 11.8%,p <0.05).The stent diameter was larger in IGSI group than in AGSI group(3.17�0.39 mm vs 2.97�0.40 mm,p <0.05).The total stent length was shorter in IGSI than AGSI group(25.85�9.34 mm vs 30.76�12.95 mm p <0.05).After IVUS re-examination during follow up,29.5%(18/61)of stent implantation in AGSI group extended into myocardial bridge(p <0.01),while 14.75%(9/61)of stent implantation did not fully cover the stenostic lesions.Totally,44.26%(27/61)stent were not placed at the exact position.Stent implantation in IGSI group tended to less related to left main,but not reach statistical significance(7.14% vs14.75% p >0.05)At sixth months follow up,the MACEs was more in AGSI than that in IGSI(37.7% vs 14.3% p =0.01).the incidence of angina was more in AGSI than that in IGSI(21.3% vs3.6% p <0.01).The incidence of target vessel ravascularization was higher in AGSI than that in IGSI(18.00% vs 11.15 % P p =0.01).There was no significant difference in the respect of acute myocardial infarction,heart failure,malignant arrhythmia and sudden cardiac death.Repeated angiography at 6-12 months indicated that the late lumen diameter loss was smaller in IGSI group than in AGSI group(0.61�0.57 vs 0.87�0.65 p <0.05).The extent of stenosis was milder in IGSI group than in AGSI group(23.22�21.48 vs 32.59�23.71 p <0.05).If taken >50% diameter loss as criteria of restenosis,the incidence of restenosis was lower in IGSI group than in AGSI group(8.9% vs 23% p <0.05).If taken 30-50% diameter loss as intimal proliferation,the incidence tended to be lower in ISGI than in ASGI group(12.5% vs 23% p =0.14).There was no difference in respect of intrastent thrombosis and stent rupture.Logistic regression indicated that factors related to major adverse cardiac events includes the residual stenosis of diagnal,not use of IVUS,stent length,left ventricle ejection fraction and LDL-C level.Not use IVUS is independent predicator of late poor outcome.Conclusion:Angiography guided stent implantation in stenostic coronary artery segment proximal to myocardial bridge leads to inaccurate stent position.IVUS is helpful in strategy making,stent size choosing and stent landing,which improve the late outcomes.Not use IVUS is independent predicator of late poor outcome.