Role Of Optical Coherence Tomography In Peripheral Pulmonary Artery Diseases In Clinical Setting

Background: Optical coherence tomography （OCT） is a new imaging techniquewith high resolution and suitable for imaging in small and peripheral vessels. OCThas been extensively employed in intracoronary arteries imaging. However, to date,using OCT technique in peripheral pulmonary artery in patients has seldom beenreported.Objective: To investigate the optimizing OCT imaging conditions for peripheralpulmonary arteries in patients and identify factors affecting quality of images inperipheral pulmonary artery imaging.Method: Patients with suspected abnormalities of peripheral pulmonary arterieswere enrolled. The optimizing imaging conditions was identified by comparisontraditional and modified imaging methods. Analyzed baseline characteristics of OCTimages obtained from patients with normal pulmonary pressure and no pulmonaryarteries diseases which finally confirmed by clinical or histological examination.There layers thicknesses of vascular wall were measured and compared in all images and different groups which were divided, according to inside diameter size. Therelationship between clarity of OCT images and size of lumen at occlusion ballooninflated position was identified through comparison the light density of images indifferent groups which were divded according to size of lumen at occlusion ballooninflated position. Dynamically observe OCT images to investigate causes for artifactimages and differentiated artifact image from luminal lesions images.Result: The graph for relation between inflated pressure and outside diameter wasdelineated. Five patients were enrolled and25segments from17peripheralpulmonary arteries were imaged with traditional and modified methods. High qualityOCT images were obtained in four segments （24%） with traditional method and22segments （88%） with modified ones,（P＜0.01）. No significant adverse events wereobserved in both methods.The OCT images obtained from8patients with normal pulmonary pressure and nopulmonary arteries diseases were analyzed. The thickness of three layer structure ofvessel wall were measured from378high clearly images. The results showed that theintima, media, and adventitia thickness were （0.10±0.03） mm,（0.08±0.02） mm, and（0.16±0.05） mm, respectively. There layers thickness were not significant different indifferent size inside diameter groups, except the media thickness in larger lumengroup was significant thick than small lumen group （P＜0.05）. The clarity of imageswas higher in fewer diameters in position of occlusion balloon than large one.Artifacts in OCT images demonstrated two different types, one is vessel walldistortion and other is blurring which look like the mural red thrombi. The walldistortion may be cause from elevated stroke volume and the blurring may be causeby deeply breathing move. Differentiation blurring images from mural red thrombican be made by dynamically observed and repeated imaging in same segment.Conclusion:1. The modified imaging method is suitable for peripheral pulmonaryartery imaging.2. These intima, media, and adventitia thickness of peripheralpulmonary arteries in vessels with inside diameter from0.95to3.62mm in patientswith normal pulmonary artery pressure and no pulmonary vascular disease was （0.10 ±0.03） mm,（0.08±0.02） mm, and （0.16±0.05） mm, respectively. The mediathickness in larger lumen group was bigger than small lumen group （P＜0.05）.3.Clarity of images is higher in fewer diameter of occlusion balloon inflating positionthan large one.4. Vessel wall distortion and images blurring are frequently OCTartifact images which may be caused by elevated stroke volume and deeply breathingmove. The blurring images can be differentiated from mural red thrombi bydynamically observed and repeat imaging. Background: Peripheral pulmonary thrombus （PPT） is not rare in clinical setting,according to autopsies researches. Owing to a lack of valuable diagnostic tools forperipheral pulmonary arteries, a number of patients with PPT are not properlydiagnosed or confirmed during lifetime. Development of new technologies forvisualization thrombi in living patient, therefore, is conceivably expected. Opticalcoherence tomography （OCT） is a recently developed optical imaging technique. Theunique advantages of OCT are not only its high resolution （range of10to20μm）,suitable for imaging in small vessel, but also intrinsic potential for differentiating redthrombi from white one.Objective: To investigate the feasibility and sensitivity of visualization peripheralpulmonary arteries thrombi and differentiating red thrombi from white ones usingOCT and to evaluate the guiding role of OCT technique in anticoagulation treatmentof pulmonary thrombi.Method: Patients with highly suspected PPT were enrolled, according to clinicalmanifestation and relative examinations. Selective pulmonary angiography （SPA） andOCT imaging at same peripheral pulmonary arteries were performed. Thrombus aspiration was performed as filling defected signs were demonstrated in proximal ofvessels by angiography. Thrombus was diagnosed by SPA, according to filling defectsigns and thrombus was diagnosed by OCT images, according the OCT image criteriaof thrombi in coronary artery. The sensitivity of OCT and SPA techniques indiagnosis thrombi was evaluated through comparing the number of thrombus detectedin different diameter pulmonary arteries segments in length of OCT imaging. Thecross-sectional areas of thrombi which were detected by OCT imaging but miss bySPA technique in OCT images were measured. Anticoagulation treatment withwarfarin over half year was administrated as middle to larger numbers of thrombiwere detected in OCT images. After half year anticoagulation treatment, OCTreexamination same segmental pulmonary arteries was performed. The guiding role ofOCT in anticoagulation treatment was evaluated through investigating the relationshipbetween patient’s symptom,6minute walk test, pulmonary artery pressure and area ofthrombi of OCT images before and after treatment.Result: Twenty-one patients were enrolled. Filling defect signs in proximal vesseslwere detected in3patients by angiography technique and aspiration thrombus withcatheter was successfully performed in one of3patients. These retrieved materialswere confirmed red thrombi by histological examination. Ninety-eight segmentalperipheral pulmonary arteries with ideal both angiography and OCT images wereobtained and divided into three groups, according to the size of luminal diameters.The distal, middle and proximal group included48,94, and41segments respectively.A total number of102thrombi images were found by SPA technique, the distal,middle, and proximal group included13,59, and30thrombi respectively. A totalnumber of189thrombi were found by OCT technique and the distal, middle, andproximal group included49,104, and36thrombi respectively. Seventy-nine （42%） of189thrombi were red thrombi and110（58%） were white thrombi identification byOCT images. The sensitivity of detecting small thrombi by OCT was advantaged thanSPA in luminal diameter less than3mm of peripheral pulmonary arteries （P＜0.01）.Thrombus with cross-sectional area less than （0.58±0.31） mm²was difficultly foundby SPA technique. Middle to larger number of thrombi was showed by OCT technique in7of21patients. After over half year anticoagulation treatment, thesepatients’ symptoms were improved, the mean distance of6MWT was lengthened, andmeans pulmonary artery pressure was decreased, and which was consistent with thedecreased cross-sectional area of thrombi measured by OCT technique.Conclusion:1. The OCT imaging can be used to diagnose thrombi in peripheralpulmonary arteries in vivo and differentiate red thrombi from white ones.2. Thesensitivity of OCT was superior to SPA in detecting thrombi in luminal diameter lessthan3mm peripheral pulmonary arteries. Thrombus with cross-sectional area lessthan0.58mm²was difficultly found by SPA technique owing to relative poorresolution.3. OCT technique can be used to guide anticoagulation treatment bydetecting peripheral pulmonary arteries thrombi. Background: Idiopathic pulmonary artery hypertension （IPAH） is a lifethreatening disease with a progressive elevation in pulmonary artery pressure andvascular resistance that result from peripheral small arteries abnormalities such as,remodeling, plexiform lesions and thrombotic lesions. The investigation of pulmonaryartery morphology in IPAH has been limited because the biopsy is not free ofcomplications in patients with pulmonary artery hypertension. The unique advantagesof optical coherence tomography are not only high resolution but also suitable forsmall intravascular imaging.Objective: To provide objective morphological abnormalities in peripheral pulmonary arteries of IPAH patient visualization by OCT imaging for diagnosisIPAH.Method: Patients with IPAH were enrolled and OCT imaging in peripheralpulmonary arteries were performed. OCT images collected from patients with nopulmonary artery diseases and normal pulmonary artery pressure were recorded ascontrol. These data including total vessel area, luminal area, mean intima thickness,relative intima thickness, intima area and percent of intima area were measured andcompared from two groups. The percent of eccentric intima thickness was calculatedin IPAH group. The OCT images from the two groups were divided into low lobesvessels and no low lobes vessels, according to position of imaging arteries. Measuredand compared these data including total vessel area, intima thickness and intima areafrom low lobes and no low lobes vessels in two groups.Results: Twenty-six segments ideal OCT images were obtained from5IPAHpatients and36segments ideal OCT images were obtained from8patients as control.The mean area of lumen in two groups was similar （P＞0.05）, indicated that the sizeof vessels from the two groups was similar. Mean intima thickness and mean intimaarea in IPAH were （0.29±0.08） mm and （1.28±0.56） mm², respectively andsignificant thickening than control （0.10±0.03）mm and（0.53±0.13）mm²,respectively （P＜0.01for each）. The36percent of intima thickening was observed inIPAH team. Nineteen segments OCT images from low lobes group and16segmentsfrom no low lobes group in contral group. Fifteen segments OCT images from lowlobes group and11segments from no low lobes group in IPAH. The mean area oflumen of low lobes and no low lobes was similar in two groups （P＞0.05）. The meanintima thickness and mean intima area in low lobes and no low lobes were similar incontral group. In IPAH group, the mean intima thickness in low lobes was （0.33±0.11） mm thickening than no low lobes （0.26±0.08） mm （P＜0.05）, and the meaninitma area in low lobes was （1.32±0.27） mm²bigger than no low lobes group was（0.91±0.22） mm²,（P＜0.01）.Conclusion:1. OCT imaging is a potent technique for detecting morpholgyabnormalities in IPAH patients.2. The intima of peripheral pulmonary arteries was significantly thickening in patients with IPAH than control and36%intima thickeningwas eccentric in patients with IPAH which frequently found at bifurcate position.3.The intima thickness and area are similar in low lobes vessels with no low lobesvessels in contral group but thickness was significant in low lobes than no low lobesin IPAH patients. Background: Optical coherence tomography is a new intravascular imagingtechnique that provides high resolution intraluminal cross-sectional images of vessel.However, an inherent limitation of this technique is the need to displace blood duringimaging which cause organs or tissues ischemia. The safety of OCT imaging inperipheral pulmonary arteries has not reported.Objective: To evaluate the safety of OCT imaging in peripheral pulmonary arteriesin the clinical setting.Method: The M2system OCT equipments and occlusion balloon catheter wereused during imaging. OCT imaging was performed during occlusion of the artery witha compliant balloon and continuous flushing. These physical signs of subjectsincluding SaO₂, blood pressure, electrocardiogram, pulse beats during procedure wererecorded. All complications relative with OCT imaging, operation procedure and≦48hours postprocedure were recorded.Results: A total of105peripheral pulmonary arteries from26patients wereunderwent OCT imaging. One hundred and thirty-six segments ideal OCT movies outof162segments were obtained. Mean vessel occlusion time was （45.36±9.24） s and mean occlusion balloon pressure was （0.65±0.18） atmospheres. Flushing withlactated Ringer’s solution was performed at a rate of （0.86±0.45） ml／s. Hemoptysiswas occurred in3patients （12%） with pulmonary systolic pressure more than65mmHg. Decreasing of SaO₂was observed in14patients and myocardial ischemiaST-T wave change was documented in7patients who all were recoved after treatmentor operation over. Severe complications including death, shock, fatal arrhythmia andvessel dissection or rupture were not observed.Conclusion:1. Peripheral pulmonary artery OCT imaging is safe in the clinicalsetting.2. Hemoptysis was frequently occurred in patients with pulmonary systolicpressure more than65mmHg.3. To avoid hemoptysis occurring result frompuncturing small vessel by guidwire, gently action was need.