| Background:Chronic total occlusion (CTO) of a coronary artery is an obstruction of a native coronary artery with no luminal continuity for at least 3 months. CTO occurs in approximately 15% to 23% of patients who undergo conventional coronary angiography (CAG) and remains a great challenge for successful revascularization, for which the success rate is only 55%-80%. Recanalization of CTO is followed by a transient impairment of vasomotor function at distal coronary segments, which could lead to underestimation of the required stent size. However, successful recanalization for CTO is associated with improvements in patient health, left ventricular function and survive rate of the patients, it therefore remains a favored therapeutic option. Accompany with technical progress and increased operator experience, then success rate of PCI for CTO is increasing. Repeated attempts may be required for patients with longer-duration CTO, which leads to cicatrix formation caused by iatrogenic vascular injuries and repair with inflammation and fibrosis after a long period. For that reason, patients with failed percutaneous coronary intervention (PCI) treatment have higher complication rates and lower success rates in further PCIs. Therefore, attempting to successfully complete the PCI with minimal attempts is an ideal treatment for CTOs.Despite the lack of visualization of the occluded segment of CTOs, conventional coronary angiography remains the reference standard for evaluating coronary anatomy.conventional coronary angiography helps to observed the blood flow of the lesions, collateral circulation, and find the best pathway acrossing the occlusion. Euro CTO club considered some morphology characteristics, such as calcification, tortuous course, ostial or bifurcation lesions and so on can influent the PCI procedural success rate, and classified the CTO lesions into A and B grade. Olivari et al believedlesion length>15 mm or not measurable, moderate to severe calcifications, duration>180 days were significant predictors of PCI failure. While Morino et al concluded the presence of calcification, bending, blunt stump, occlusion length>20 mm can be the independent predictors unsuccessful PCI.However, recently, the superiority of noninvasive coronary computed tomography angiography (CCTA) for directly observing morphological characteristics of occluded lesions, especially calcification, has been highlighted. Rolf et al. even found that pre-CCTA promoted a higher success rate of PCI than in patients who did not undergo a pre-CCTA. Therefore, several studies have focused on morphological characteristics on CCTA, such as blunt stump, tortuous course, and calcification, which could predict a successful PCI procedure. Majority of scholars thought that calcificaiton of the CTO lesions were an important predictor of failed PCI. For example, Victoria et al thought an arc of calcium on CCTA which cannot be observed by CAG can predict failure in PCI for CTOs. Jen et al. concluded calcification length ratio of>0.5 remains to be the independent negative predictor of both technical success and procedural success. But Minghua Li et al observed sign of linear intrathrombus enhancement on CCTA which they thought were microvessels or recanalized lumens of CTO,and believed that was the predictor for successful PCI. However, neither the predictors of successful PCI on CCTA nor those on CAG were consistent in those studies.Objective:The purpose of the present study was to investigate whether morphological characteristics from pre-CCTA and CAGcould act as predictors of failed antegradePCI and could prompt an early retrograde procedure after a failed antegrade attempt for the appropriate patients, thus enabling successful revascularization as minimum times as possible.Patients and Methods:All patients underwent PCI treatment of CTO (not including in-stent occlusion) at our hospital between January 2012 and December 2013 were screened for enrollment in this retrospective study. Patients who underwent CCTA and CAG prior to their staged CCTA- and CAG-guided PCI were included. The interval between the conventional coronary angiography and/or staged PCI and CCTA could be 24 h to 1 month. All inpatients received intravenous hydration with 1 ml/kg/h of saline the day before and after CCTA examination and PCI procedure. The exclusion criteria included allergy to contrast media, undergoing a previous coronary artery bypass graft (CABG), and a history of acute myocardial infarction within 1 month. All the CTO lesions were treated as an individual lesions, the CTOs were divided into two groups:the successful antegradePCI (A-PCI) group and the failed A-PCI group. All of the patients signed the informed consent for each examination and treatment, and the study protocol was approved by the Guangdong General Hospital(Guangdong Academy of Medical Sciences) ethics committee.The duration of the CTOs depended on the diagnostic coronary angiography or clinical symptoms in the CTO artery distribution. Indications for pre-CCTA included lack of allergy to contrast media, no acute or chronic renal insufficiency (serum creatinine>1.5 g/dL [132.6 mmol/L]), no atrial fibrillation or other heart rhythm irregularity and no clinical history of uncontrolled hyperthyroidism or multiple myeloma.Indications for PCI included patients with angina or evidence of myocardial ischemia in the CTO artery distribution; the presence of viable myocardium supplied by the occluded artery revealed by stress echocardiography and/or single-photon emission computed tomography; lack of cardiac and renal insufficiency; and moderate to high (60%) confidence of successful PCI without major adverse cardiovascular events (MACE).Successful PCI was defined as attainment of a residual diameter stenosis of<20% and thrombolysis in myocardial infarction (TIMI) flow grade 3, without coronary artery dissection, perforation or acute re-occlusion, and without MACE happened during hospitalization.1.CCTA ProtocolA wide detector 256-slice CT scanner (Brilliance iCT; Philips Healthcare, Cleveland, Ohio, USA) was used for scanning. A Metoprolol Tartrate Tablets (25-50 mg) was sublingually used in patients with heart rates (HR) greater than 70 beats per minute at least half a hour. A bolus of contrast medium (Ultravist 370, Bayer Schering Pharma, Berlin, Germany) was injected into the antecubital vein at a rate of 1.5 ml/s, followed by 30 ml saline solution. A real-time bolus tracking technique (BolusPro, Philips Healthcare, Cleveland, Ohio, USA) was used for synchronization of the contrast medium injection and scanning; the region of interest was placed on the ascending aorta root, and image acquisition was started 5 s after the signal density reached a threshold of 180 Hounsfield units (HU). A prospective electrocardiographically gated CT angiography was performed with the following parameters:tube voltage,120 kV; tube current,120 mAs; collimation,128×0.625 mm; rotation time,270 ms; pitch, 0.18; and FOV,250 mm. The CT scan was performed from 1 cm below the tracheal bifurcation to 2 cm below the diaphragm. Electrocardiographically gated datasets were reconstructed at 70%,75%, and 80% of the cardiac cycle if the patient’s HR was less than 70 beats/min; additional datasets were reconstructed at 40%,45%, and 50% of the cardiac cycle if HR was>70 beats/min.The acquired datasets were sent to a Philips workstation (Extended Brilliance Workspace) for image post-processing and analysis. The post-process technology included volume rendering (VR), maximum intensity projection (MIP), multiplanar reformation (MPR), and curved planar reconstruction (CPR).2.CAG ProcedureA digital cardiac angiography system (AlluraXper FD10, Philips Medical System, Best, Netherlands) was used to obtain an average of 5 cineangiograms for the left coronary artery and 2 cineangiograms for the right coronary artery at 15 frames/s. Some patients underwent bilateral coronary artery angiography at the same time. The patients were placed in a supine position, and angiography of the coronary arteries was performed through the radial artery or the femoral artery. The gantry angles of the projections were selected at the discretion of the cardiologist.3.Assessment of ParametersThe following characteristics were evaluated on CCTA and CAG:lesion site (LAD/RCA/LCX/LM); the calcification degree of the lesion (none/slight/severe: calcified area was 0%/<50%/≥50%on CCTA or present/absent on CAG); stump morphology (sharp or blunt); lesion length (mm); ostial or bifurcation lesions; tortuous course (>45° or<45°); remodeling type; the presence of microchannels (linear or dot intrathrombus enhancement on CCTA and slender blood flow observed on CAG); bridging vessels (present or absent); the appearance of the occluded distal segment (good/bad:vessels filled well with contrast medium and withoutsignificant stenosis≥50% /poor visualization or stenosis≥50%) and the score of the collateral vessels (good/bad:present/absent on CCTA or score of 3/score of 0-2 on CAG using the classification of Rentrop). The diameter of the occluded vessel (Do) and the adjacent normal vessel (DN) were measured by CCTA, which determined the type of vascular remodeling (DO/DN≥1 or<1 representing positive or negative remodeling, respectively, Figure 1). All of the characteristics were independently evaluated by two experienced observers who were blinded to the examination findings.4.Percutaneous Coronary Intervention TechniqueThe CCTA-and CAG-guided PCI procedure involved placing the CT and fluoroscopic images side by side before or during the PCI. The CCTA images were reconstructed with post-processing software to show similar images with a closed angle as in the CAG image (Figure 2). The procedure was abandoned if the radiation dose or the total contrast agent exceeded the maximum tolerance of the patients or when complications, such as coronary dissection and perforation, occurred, which could not be ameliorated after treatment.5. Statistical AnalysisEach CTO lesion was regarded as an independent observation for the purpose of the statistical analysis. The statistical analysis was performed using a commercially available statistical software package (SSPS, version 13.0; SPSS, ChiCAGo, III). The quantitative variables were expressed as the means ± standard deviations or median (quartiles). Inter- and intra-observer agreement were expressed as percentages of agreement and as Cohen k values for categorical variables. The t-test was used for normally distributed data, whereas the Mann-Whitney U test was used for data that were not normally distributed,and the chi-squared test was used for categorical variables. The paired-samples t-test, Mann-Whitney U test and McNemar’s test were used to detect the differences between the same characteristics on CCTA and CAG Univariate statistical tests were first performed with binary logistic regression to identify variables of CCTA and CAG associated with failed A-PCI. A multivariate model for the prediction of A-PCI procedure failure was fitted by including variables that were significant (P<0.05) in the univariate analysis. For the multivariate analysis, continuous variables were treated as categorical variables using the cutoff values that were determined by the Youdan’s criterion after receiver operating characteristic (ROC) curve analysis. P<0.05 was considered statistically significant.Results:1.Clinical Characteristics and PCI ResultsDuring the study period,658 patients with 702 CTO lesions were screened, and 103 patientswith 108 CTO lesions who underwent pre-CCTA were enrolled into the study(Indications for pre-PCI CCTA:55 cases were suspected coronary artery disease, 34 cases were confirmed by angiography but with insuffucient confidence,and 14 ceses were experienced failed PCI). The total success rate, the A-PCI and R-PCI success rate of lesions with pre-CCTA were higher than those without, among which the difference of the total success rate was statistically significant (Total:94/108 (87.0%) vs 454/594 (76.4%), P= 0.016, A-PCI:80/108 (74.0%) vs 401/594 (67.5%), P= 0.215; R-PCI:14/15 (93.3%) vs 53/61 (86.9%), P= 0.678; respectively). There are 80 cases included in the successful A-PCI group, while 28 cases were included into the failed A-PCI group.15 of the 28 cases which failed A-PCI were attempted to a retrogradePCI (R-PCI) procedure, and just 1 failed(excluded for attempted R-PCI:3 cases had complications,4 cases were with poorly developed collateral vessels,2 cases were with poorly visualized distal segment, and 2 cases were with poor physical condition). There were significant differences in lesion duration, procedure time and times of PCI attempts between the failed A-PCI group and the successful A-PCI group (P< 0.05). Other clinical characteristics were not significant different betweeen the two group, and the site of the lesion in the failed A-PCI group was not significantly different from the successful A-PCI group(P=0.080). The cutoff value for CTO duration determined by further ROC curve analysis was 6.5 months. Five cases of coronary artery perforation, one case of coronary dissection and one case of cardiac tamponade occurred. All of these complications disappeared after treatment.2.CCTA CharacteristicsOcclusion stump were more frequently manifested blunt or absent in the failed A-PCI group(18/28 vs 33/80, P=0.048). The median lesion length was 23.62 mm; the lesions with failed A-PCI (28.37mm (15.88,49.30)) were longer than those with successful A-PCI (22.77 mm (14.66,30.54), P=0.025). The cutoff value determined by further ROC curve analysis was 31.89 mm. The tortuos course were more frequently found in the failed A-PCI group (6/28 vs 4/80,P=0.010), and ostial or bifurcation lesions were more likely to be failed in the A-PCI(13/28 vs 21/80,P=0.049). Negative remodeling was visualized in 14 cases of the failed A-PCI group (50.0%), which was significantly more prevalent than that in the successful A-PCI group (P<0.001). Five of the 14 negative remodeling lesions underwent attempted staged R-PCI; 1 case failed, and its degree of negative remodeling (DO/Dn) was<0.5, whereas the other 4 cases showed 0.5<Do/Dn<1. Calcification in our cases was eccentric, scattered or sandwich biscuit-like (Figure 2) and without 360° arc calcified lesions. There were 4 extremely severe calcification cases (calcified area> 90%), and 3 of them achieved success. Other detailed data are shown in Table 2. The inter-observer agreement on CCTA was good for all of the lesions (k=0.75). The intra-observer agreement for observer 1 and observer 2 was also good for all of the lesions (k=0.77 and k=0.82, respectively).3.C AG CharacteristicsOcclusion stump were more frequently manifested blunt or absent in the failed A-PCI group. Ostial or bifurcation lesions(17/28 vs 18/80,P<0.001) and tortuous courses were more frequently observed in the failed A-PCI group(22/28 vs 39/80, P=0.008; 14/28 vs 19/80, P=0.016, respectively). The median lesion length was 23.62 mm; the lesions with failed A-PCI (28.37mm (15.88,49.30)) were longer than those with successful A-PCI (22.77 mm (14.66,30.54), P=0.025). Other characteristics on CAG showed no difference between the two groups (P=0.340-0.915). The 15 cases that underwent attempted R-PCI showed good collateral vessels (score of 3 in 14 cases, score of 2 in 1 case) and good visualization of the occluded distal segment (14/15). The inter-observer agreement on CAG was good for all of the lesions (k= 0.73). The intra-observer agreement for observer 1 and observer 2 was good for all of the lesions (k=0.76 and k=0.79, respectively). The ostial or bifurcation lesion observed on CAG was not significantly different from that on CCTA (P=0.82), while other signs observed on CAG were significantly different from those on CCTA (P<0.001-0.03, P value(2) shown in Table 3).4.Multivariate AnalysisWhen the same variables by both CAG and CCTA were predictive of A-PCI failure by univariate analysis (stump morphology, tortuous course and lesion length), only one (the better predictor which can be observed or measured directly) was entered into the multivariable analysis. In the multivariate model, the independent negative predictor identified on CAG was ostial or bifurcation lesions (OR=8.02; 95% CI= 1.90,35.36; P=0.005), whereas on CCTA, the negative predictors included the presence of negative remodeling (OR=137.82; 95% CI=11.69,1624.36;P< 0.001) and a lesion length greater than 31.89 mm (OR=7.04; 95% CI=1.72,28.86; P= 0.007). Stump morphology, tortuous course on CAG and CCTA, and CTO duration greater than 6.5 months were not independent predictors after the multivariate analysis (P>0.05 for each). The success rate of A-PCI in cases without negative remodeling was 85.0%(79/93), and the total success rate of PCI in these cases was 96.8% (90/93). Two or more risk factors for A-PCI failure were present in 20/108 patients (18.5%). Compared to patients with 0 or 1 risk factors, those with 2 or 3 risk factors had a markedly lower A-PCI success rate (4/20 (20.0%) vs.76/88 (86.4%), P <0.001).Conclusions:The negative predictors for successful A-PCI were negative remodeling and CTO lesion length on CCTA as well as ostial or bifurcation lesions on CAG. For appropriate patients after a failed A- attempt, selecting an early R-PCI could be a suitable choice for minimum iatrogenic vessel injury and radiation dosage, contributing to rapid successful revascularization. In addition, an initial R-PCI (rather than A-PCI) attempt might be considered in patients with 2 or more high risk features for A-PCI failure. |
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