BACKGROUND: Advancing the retrograde microcatheter (MC) into the antegrade guide catheter during retrograde chronic total occlusion (CTO) percutaneous coronary intervention (PCI) can be challenging or impossible, preventing guidewire externalization. OBJECTIVES: To detail and evaluate all the techniques focused on wiring to achieve intubation of the distal tip of a microcatheter, balloon, or stent with an antegrade or retrograde guidewire, aiming to reduce complications by minimizing tension on fragile collaterals during externalization and enabling rapid antegrade conversion in various clinical scenarios. METHODS: We describe the two main techniques, tip-in and rendezvous, and their derivatives such a facilitated tip-in, manual MC-tip modification, tip-in the balloon, tip-in the stent, deep dive rendezvous, catch-it and antegrade microcatheter probing. We provide case studies that demonstrate the effectiveness of these techniques in complex scenarios involving extreme vessel angulation, severe calcification, fragile collaterals, and challenging retrograde MC crossing without externalization. CONCLUSION: The development of advanced variants along with traditional techniques to establish retrograde guidewire connection and antegrade conversion has led to the establishment of a cohesive group of methods known as portal techniques. These approaches serve as strategic advantages in retrograde CTO-PCI, providing a valuable and feasible alternative to conventional retrograde connection techniques, particularly when those techniques fail. Their ability to avoid the externalization process reduces potential damage to collateral channels and the ostium of the donor artery, potentially leading to a reduction in complication rates.

AOU Policlinico G Rodolico San Marco Catania Italy

Cardio Center IRCCS Humanitas Research Hospital Rozzano Milan Italy

Cardiology Department Niculae Stancioiu Heart Institute Cluj Napoca Romania

Cardiovascular Department Clinique Saint Joseph Vivalia Arlon Belgium

Cardiovascular Jolimont Hospital La Louvière Belgium

Clinic of Internal Medicine and Cardiology Heart Center Lahr Lahr Germany

Clinique MontLégia Department of Cardiovascular MontLégia Liège Belgium

Department of Cardiology University Hospital Basel Basel Switzerland

Department of Cardiovascular Hôpital Valenciennes Valenciennes France

Edith and Benson Ford Heart and Vascular Institute Henry Ford Hospital Henry Ford Health System Wayne State University Detroit Michigan USA

Frimley Park Hospital NHS Foundation Trust Camberley UK

HartCentrum Ziekenhuis Aan de Stroom Middelheim Antwerp Belgium

Interventional Cardiology Department County Hospital Cakovec Cakovec Croatia

Kardiologické centrum Agel Pardubice Czech Republic

Minneapolis Heart Institute and Minneapolis Heart Institute Foundation Minneapolis Minnesota USA

Prince of Wales Hospital Chinese University Hong Kong Hong Kong China

University Clinical Center Niš Niš Serbia

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