Synergy Between Percutaneous Coronary Intervention With Taxus And Cardiac Surgery

; Associate Editor-In-Chief: Atif Mohammad, M.D.

Related Key Words and Synonyms: SYNTAX, Taxus, Drug Eluting Stents, SYNTAX Score, SYNTAX trial, CABG, Coronary artery bypass graft, PCI, Angioplasty

Overview
SYNTAX which is the abbreviation for "Synergy between Percutaneous Coronary Intervention with Taxus and Cardiac Surgery" was a prospective clinical trial conducted in 85 sites in 17 countries across Europe and the United States.The purpose of this study was to assess objective revascularization strategy and treatment protocol for patients with previously untreated 3-vessel disease or left main coronary artery disease and identify the populations for whom only one will be better.Previous clinical trials comparing bare metal stents with CABG have shown similar survival rates but higher revascularization rates in patients having bare metal stents. Randomized clinical trials have also shown Drug Eluting Stents (DES)as compared with Bare Metal Stents (BMS), to show better results in terms of repeat revascularization, myocardial infarction and deaths especially in more complex anatomical cases .Currently, the guidelines for 3 vessel disease or left main is the patient to go for bypass surgery. The SYNTAX trial was conducted to assess the efficacy of Taxus which is a Paclitaxel coated drug eluting stent as compared to CABG for effective means of revascularization in patients with three vessel disease or left main disease.

Methods of Study
1800 patients were enrolled in the study.An interventional cardiologist and Cardiac surgeon both assessed patients eligible for the study according to the study criteria. Patients which were determined to have equivalent results with either CABG or PCI were randomly assigned to either arm.Patients for whom one treatment was effective were assigned to parallel registry-PCI registry for CABG ineligible patients and likewise CABG registry for PCI ineligible patients.

SYNTAX Score
Diagnostic angiograms and electrocardiograms were individually assessed by staff at an independent site who were unaware of treatment status of patients.A SYNTAX Score was designed for scoring of the coronary angiograms according to their severity of disease. The SYNTAX score was used as a diagnostic tool for comprehensive anatomical assessment of patients with coronary artery disease .Higher scores reflect more complex disease and lower scores less severe.Patients with left main disease with 1 or 2 vessel disease had higher scores as compared to 3-vessel disease.A high score was considered > 33 and a low score was defined as < 22.

SYNTAX Scores and definitions of individual Coronary Artery Segments


1.RCA Proximal:From the ostium to one half the distance to the acute margin of the heart 2.RCA Mid:From the end of the first segment to acute margin of the heart 3.RCA Distal:From the acute margin of the heart to the origin of the posterior descending artery 4.Posterior descending artery:Running in the posterior interventricular groove 16.Posterolateral branch from the RCA :Posterolateral branch originating from the distal coronary artery distal to the crux 16a.Posterolateral branch from the RCA :First posterolateral branch from segment 16 16b.Posterolateral branch from the RCA :Second posterolateral branch from the segment 16 16c.Posterolateral branch from the RCA :Third posterolateral branch from the segment 16 5.Left main: From the ostium of the LCA through bifurcation into the left anterior descending and left circumflex branches 6.LAD Proximal:Proximal to and including first major septal branch 7.LAD Mid:LAD immediately distal to the origin of first septal branch and extending to the point where LAD forms an angle (RAO)view .If this angle is not identifiable this segment ends at one half the distance from the first septal to the apex of the heart. 8.LAD Apical:Terminal portion of LAD, beginning at the end of previous sement and extending to or beyond the apex. 9.First Diagonal:The first diagonal originating from segment 6 or 7 9a.First Diagonal a :Additional first diagonal originating from segment 6 or 7 ,before segment 8 10.Second Diagonal:Orginating from segment 8 or the transition between segment 7 and 8 10a.Second Diagonal:Additional second diagonal originating from segment 8 11.Proximal Circumflex:Main stem of circumflex from its origin of left main and including origin of first obtuse marginal branch. 12.Intermediate/Anterolateral artery:Branch from trifurcating left main and including origin of first obtuse marginal branch. 12a.Obtuse marginal a:First side branch of circumflex running in general to the area of obtuse margin of the heart. 12b.Obtuse marginal b:Second additional branch of circumflex running in the same direction as 12. 13.Distal Circumflex artery:The stem of circumflex distal to the origin from the most distal obtuse branch, and running along the posterior left atrioventricular groove.Caliber may be small or artery absent. 14.Left Posterolateral:Running to the posterolateral surface of the left ventricle.May be absent or a division of obtuse marginal branch. 14a.Left Posterolateral a :Distal from 14 and running in the same direction. 14b.Left Posterolateral b :Distal from 14 and 14a and running in the same direction. 15.Posterior descending :Most distal part of dominant left circumflex when present.It gives origin to the septal branches.When this artery is present,segment 4 is usually absent.

Scoring for Adverse Lesions Characteristics
Adverse lesions are more specifically scored according to their particular characteristic by either multiplying or adding by a certain factor. Type A lesions are defined as lesions not involving the ostium of side branch, in the main vessel proximal to the ostium of the side branch. Type B lesions are defined as lesions not involving the ostium of side branch, in the main vessel distal to the ostium of the side branch. Type C lesions are defined as lesions not involving the ostium of side branch, in the main vessel both proximal and distal to the ostium of the side branch. Type D lesions are defined as lesions involving the ostium of side branch, in the main vessel proximal and distal to the ostium of the side branch. Type E lesions are defined as lesions involving only the ostium of side branch. Type F lesions are defined as lesions involving only the ostium of side branch,in the main vessel proximal to the ostium of the side branch. Type G lesions are defined as lesions involving only the ostium of side branch,in the main vessel distal to the ostium of the side branch.

Adapted from publication
 * Trifurcations are scored for segments 3/4/16/16a, 5/6/11/12, 11/12a/12b/13, 6/7/9/9a and 7/8/10/10a.
 * Bifurcations are scored for segments 5/6/11, 6/7/9, 7/8/10, 11/13/12a, 13/14/14a, 3/4/16 and 13/14/15.
 * Severe tortuosity was defined one or more bends of 90° or more, three or more bends of 45° to 90° proximal of the diseased segment.
 * Aorto-ostial was defined for immediate origin of coronary arteries from the aorta.
 * Diffuse/small vessels disease was defined as diseases involving more then 75% of the of length of the segment of 2 mm vessel diameter.
 * Co-dominance is not used as a option while scoring for dominance.

Clinical SYNTAX Score
There has been a debate over the prognostic implications of the SYNTAX score.To improve this and include clinical variables, a Clinical SYNTAX Score was calculated which is

Clinical SYNTAX Score= SYNTAX Score x modified ACEF score whereby the modified ACEF score is patients age(years),ejection fraction + 1 point for every 10 ml the creatinine clearance \60 ml min per 1.73 m2.Patients with a significantly low score<15.6 had higher MACCE as compared to patients with high CSS(Clinical SYNTAX Score) i.e. >27.The c-statistic for CSS was 0.69 and 0.62 for 5 year mortality and for 5-year MACCE respectively.The c-scores for the SYNTAX score for 5-year mortality and MACCE were 0.62 and 0.59 respectively.Thus, the Clinical variables included in the SYNTAX score improved its prognostic outcomes significantly.

NERS New Risk Stratification Score
The New Risk Stratification score was developed as a prognostic score for patients undergoing left main stenting.It had a total of 54 variables with 17 being clinical, 33 angiographic and 4 procedural.The NERS score was derived from 260 patients who had unprotected LM disease and were about to undergo PCI.It also included 337 patients from a left main registry.A NERS score of more then 25 demonstrated a sensitivity and specificity of 92.0% and 74.1% MACCE respectively, which was significantly higher than SYNTAX intermediate risk 20.5% and 25.4% respectively and SYNTAX higher risk 70.5% and 35.2%respectively. The New Risk Stratification Score was found to be prognostically a better score as compared to SYNTAX but only for patients undergoing left main stenting.Still further studies are needed to validate the SYNTAX score alongwith other scores used during QCA as a prognostic scoring criteria in patients undergoing PCI.