BackgroundWith the development of specialized equipment and the retrograde technique. success rates for percutaneous coronary intervention (PCI) of chronic total occlusions (CTOs) have increased from 60 to 90% in the past 10 years. Performing PCI via a collateral channel from the contralateral artery. using two guiding catheters. https://www.roneverhart.com/Western-Digital-Ultrastar-DC-HC550-WUH721816ALE6L0-0F38460-16TB-7-2K-RPM-SATA-6Gb-s-512e-ISE-3-5in-Hard-Drive/