Current Cardiology Reviews (v.10, #2)

The Evidence Base for Revascularisation of Chronic Total Occlusions by Alan Bagnall, Ioakim Spyridopoulos (88-98).
When patients with ischaemic heart disease are considered for revascularisation the Heart Team's aim is tochoose a therapy that will provide complete relief of angina for an acceptable procedural risk. Complete functional revascularisationof ischaemic myocardium is thus the goal and for this reason the presence of a chronic total occlusion(CTO) - which remain the most technically challenging lesions to revascularise percutaneously - is the most common reasonfor selecting coronary artery bypass surgery [1]. From the behaviour of Heart Teams it is clear that physicians believethat CTOs are important. Yet when faced with patients with CTOs for whom surgery appears excessive (e.g. nonproximalLAD) or too high risk, there remains a reluctance to undertake CTO PCI, despite significant recent advances inprocedural success and safety and a considerable body of evidence supporting a survival benefit following successfulCTO PCI. This article reviews the relationship between CTOs, symptoms of angina, ischaemia and left ventricular dysfunctionand further explores the evidence relating their treatment to improved quality of life and prognosis in patientswith these features.

Chronic total occlusion (CTO) pathophysiology has been described in a few, small studies using post mortemhistology, and more recently, in vivo intravascular ultrasound (IVUS) to analyse the constituents of occluded segments.Recent improvements in equipment and techniques have revealed new insights into physical characteristics of occludedcoronaries, which in turn enable predictable procedural success. The purpose of this review is to consider the publishedevidence describing CTO pathophysiology from the perspective of the hybrid algorithm approach to CTO PCI.;Methods: Literature searches using “Chronic Occlusion”, “angioplasty”, and” pathology” as keywords. Further searcheson “coronary” “collateral”, “Viability”. Bibliographies were scrutinised for further key publications in an iterative process.Papers describing animal models were excluded.

Procedure Planning: Anatomical Determinants of Strategy by Colm Hanratty, Simon Walsh (108-119).
In contemporary practice there are three main methods that can be employed when attempting to open a chronictotal occlusion (CTO) of a coronary artery; antegrade or retrograde wire escalation, antegrade dissection re-entry and retrogradedissection re-entry. This editorial will attempt to clarify the anatomical features that can be identified to help whendeciding which of these strategies to employ initially and help understand the reasons for this decision.

The Role for Adjunctive Image in Pre-procedural Assessment and Peri-Procedural Management in Chronic Total Occlusion Recanalisation by Rodrigo Estevez-Loureiro, Matteo Ghione, Kadriye Kilickesmez, Pilar Agudo, Alistair Lindsay, Carlo Di Mario (120-126).
Non invasive coronary angiography with multislice computed tomography has exquisite sensitivity to detectcalcium and even the faintest late contrast filling of the distal vessel. Calcium burden and occlusion length are still valuablemarkers of duration, complexity and success of the recanalisation procedure. The ability to visualise the vessel also inthe occluded segment, especially if calcified, can also help the operator to understand where to pierce the proximal cap instumpless occlusions and to predict unusual courses, especially in very tortuous arteries. Imaging side by side CT imagesand angiography during the recanalisation procedure is an established practice in many active CTO laboratories and algorithmsfor co-registration are designed to overcome the challenges of systo-diastolic and respiratory motion. Intravascularultrasound is used in almost all cases by the experienced Japanese CTO operators but most of the times its main use is abetter identification of the diseased segment after predilatation to ensure complete stent cover and appropriate stent expansion,an application similar to other complex non occlusive lesions. The specificity of IVUS during CTO recanalisation isthe identification of the vessel path in stumpless occlusions and the guidance of wire reentry especially during reverseControlled Retrograde Anterograde Tracking. Optical coherence tomography has limitations in the setting of CTO recanalisationbecause of the need of forceful contrast flushing to clear blood, contraindicated in the presence of anterogradedissections, and the limited penetration. The variability in the use of both non-invasive and invasive imaging during CTOrecanalisation is immense, going from more than 90% in Japan to less than 20% in Europe and intermediate penetration inthe USA. Probably the explanation is almost only in availability and cost because all countries see a progressive increaseof use suggesting that these methods are becoming an established tool for guidance of CTO recanalisation.

Advances in Procedural Techniques - Antegrade by William Wilson, James C. Spratt (127-144).
There have been many technological advances in antegrade CTO PCI, but perhaps most importantly hasbeen the evolution of the “hybrid' approach where ideally there exists a seamless interplay of antegrade wiring, antegradedissection re-entry and retrograde approaches as dictated by procedural factors. Antegrade wire escalation withintimal tracking remains the preferred initial strategy in short CTOs without proximal cap ambiguity. More complexCTOs, however, usually require either a retrograde or an antegrade dissection re-entry approach, or both. Antegradedissection re-entry is well suited to long occlusions where there is a healthy distal vessel and limited “interventional”collaterals. Early use of a dissection re-entry strategy will increase success rates, reduce complications, and minimiseradiation exposure, contrast use as well as procedural times. Antegrade dissection can be achieved with a knuckle wiretechnique or the CrossBoss catheter whilst re-entry will be achieved in the most reproducible and reliable fashion bythe Stingray balloon/wire. It should be avoided where there is potential for loss of large side branches. It remains to beseen whether use of newer dissection re-entry strategies will be associated with lower restenosis rates compared withthe more uncontrolled subintimal tracking strategies such as STAR and whether stent insertion in the subintimal spaceis associated with higher rates of late stent malapposition and stent thrombosis. It is to be hoped that the algorithms,which have been developed to guide CTO operators, allow for a better transfer of knowledge and skills to increase uptakeand acceptance of CTO PCI as a whole.

Adjunctive Strategies in the Management of Resistant, 'Undilatableµ Coronary Lesions After Successfully Crossing a CTO with a Guidewire by Sara L. Fairley, James C. Spratt, Omar Rana, Suneel Talwar, Colm Hanratty, Simon Walsh (145-157).
Successful revascularisation of chronic total occlusions (CTOs) remains one of the greatest challenges in theera of contemporary percutaneous coronary intervention (PCI). Such lesions are encountered with increasing frequency incurrent clinical practice. A predictable increase in the future burden of CTO management can be anticipated given theageing population, increased rates of renal failure, graft failure and diabetes mellitus. Given recent advances and developmentsin CTO PCI management, successful recanalisation can be anticipated in the majority of procedures undertakenat high-volume centres when performed by expert operators.Despite advances in device technology, the management of resistant, calcific lesions remains one of the greatest challengesin successful CTO intervention. Established techniques to modify calcific lesions include the use of high-pressurenon-compliant balloon dilation, cutting-balloons, anchor balloons and high speed rotational atherectomy (HSRA). Novelapproaches have proven to be safe and technically feasible where standard approaches have failed. A step-wise progressionof strategies is demonstrated, from well-recognised techniques to techniques that should only be considered whenstandard manoeuvres have proven unsuccessful. These methods will be described in the setting of clinical examples andinclude use of very high-pressure non-compliant balloon dilation, intentional balloon rupture with vessel dissection or balloonassisted micro-dissection (BAM), excimer coronary laser atherectomy (ECLA) and use of HSRA in various 'offlabel'settings.

Despite a short lag period since its development the retrograde approach has been increasingly integratedwithin the treatment strategies for the percutaneous treatment of coronary chronic total occlusions. This review article discusswhich anatomical features argue most powerfully for its use, the specific skills required for its uptake and the technologywhich has facilitated these developments.

Medical Treatment of Aortic Aneurysms in Marfan Syndrome and other Heritable Conditions by Christine H. Attenhofer Jost, Matthias Greutmann, Heidi M. Connolly, Roland Weber, Marianne Rohrbach, Angela Oxenius, Oliver Kretschmar, Thomas F. Luscher, Gabor Matyas (161-171).
Thoracic aortic aneurysms can be triggered by genetic disorders such as Marfan syndrome (MFS) and relatedaortic diseases as well as by inflammatory disorders such as giant cell arteritis or atherosclerosis. In all these conditions,cardiovascular risk factors, such as systemic arterial hypertension, may contribute to faster rate of aneurysm progression.Optimal medical management to prevent progressive aortic dilatation and aortic dissection is unknown. ?-blockers havebeen the mainstay of medical treatment for many years despite limited evidence of beneficial effects. Recently, losartan,an angiotensin II type I receptor antagonist (ARB), has shown promising results in a mouse model of MFS and subsequentlyin humans with MFS and hence is increasingly used. Several ongoing trials comparing losartan to ? -blockersand/or placebo will better define the role of ARBs in the near future. In addition, other medications, such as statins andtetracyclines have demonstrated potential benefit in experimental aortic aneurysm studies. Given the advances in our understandingof molecular mechanisms triggering aortic dilatation and dissection, individualized management tailored tothe underlying genetic defect may be on the horizon of individualized medicine. We anticipate that ongoing research willaddress the question whether such genotype/pathogenesis-driven treatments can replace current phenotype/syndromedrivenstrategies and whether other forms of aortopathies should be treated similarly. In this work, we review currentlyused and promising medical treatment options for patients with heritable aortic aneurysmal disorders.