Q&A: Dr. Salman Allana on CTO PCI Skill, Volume & Outcomes

In the evolving field of complex coronary intervention, chronic total occlusion (CTO) percutaneous coronary intervention (PCI) remains among the most technically demanding procedures, particularly when performed via a retrograde approach. While institutional and operator experience are known to influence outcomes, the specific impact of individual operator volume on the success and complications of retrograde CTO PCI has not been well defined. In a new analysis from the PROGRESS-CTO registry, Allana et al. compare nearly 4,000 retrograde CTO PCIs performed by higher-volume operators (HVOs, ≥20 cases/year) versus lower-volume operators (LVOs, <20 cases/year), providing new insights into how operator experience shapes case selection, procedural complexity, success rates, and adverse outcomes in this high-stakes subset of interventional cardiology. The results have significant implications for clinical care systems and procedural training.

An interview with lead author, Salman Allana, MD:

Amit Goyal, MD: You set out to examine the difference in outcomes for coronary CTO PCI between high-volume and low-volume operators. You decided to return to training after practicing as a full-fledged interventional cardiologist to pursue greater mastery in complex coronary interventions. In your mind, why is this comparison between HVOs and LVOs important to examine?

CTOs are among the most complex of coronary interventions, especially when advanced techniques such as retrograde and dissection reentry are employed. CTO PCI teaches us that failure is always a distinct possibility, and we need to master multiple skills and techniques to succeed. High-volume operators perform these techniques more frequently and continue to learn and improve their skills at a much faster pace, which allows them to achieve success and minimize complications in these complex interventions.

Dr. Goyal: Can you please share the nuts and bolts of how you and your colleagues planned your study?

Dr. Allana: Using the PROGRESS CTO registry, we examined the baseline characteristics and outcomes of 3,802 retrograde CTO PCIs performed at 44 centers between 2012 and 2023. Technical success was defined as successful revascularization with <30% residual diameter stenosis and Thrombolysis In Myocardial Infarction (TIMI) flow grade 3. Procedural success was defined as technical success without in-hospital major adverse cardiac events (MACE), which included death, myocardial infarction, urgent repeat target vessel revascularization, tamponade, and stroke. The median annual number of retrograde CTO PCIs was 20 per operator. We therefore defined the lower-volume operators (LVOs) and higher-volume operators (HVOs) as those performing <20 vs ≥20 retrograde CTO PCIs annually, respectively, and compared outcomes between them.

Dr. Goyal: Did you find any differences in case selection between LVOs and HVOs?

Dr. Allana: We did. HVOs performed more complex cases. The J-CTO score, a measure of CTO lesion complexity, was significantly higher among cases performed by HVOs. There was a higher proportion of coronary artery bypass graft surgery (CABG) patients, who inherently have more complex lesions, among HVOs. Also, CTO lesions treated by HVOs had longer occlusion length, moderate to severe calcification, and moderate to severe tortuosity. Use of mechanical circulatory support and high-risk retrograde collateral was also significantly higher among HVOs. Overall, HVOs performed CTO PCI in more complex lesions and also performed these in higher-risk patients.

Dr. Goyal: So, high-volume operators were taking on more complex lesion subsets. Were there differences in outcomes in terms of success and complications?

Dr. Allana: Yes, there were. Despite HVOs undertaking more complex and higher-risk CTOs, their technical and procedural success rates were significantly higher (almost 9% absolute difference in technical success) when compared to LVOs. The in-hospital MACE rate was also higher among HVOs. In multivariable analysis, higher operator retrograde volume was independently associated with higher technical success, but not with in-hospital major adverse cardiac events (MACE). This suggests that the higher in-hospital MACE rate was related to the more complex and higher-risk cases performed by HVOs.

Dr. Goyal: What are the implications for practice? Are there specific phenotypes of CTOs that may be appropriate for LVOs to attempt before referring to HVO colleagues, especially within the context of access to such operators?

Dr. Allana: It is reasonable for LVOs to attempt low-complexity CTO lesions and refer higher-complexity lesions, as well as all unsuccessful attempts, to HVOs. However, this course must be taken with the goal and intention of continuing to learn and improve technical skills. If that is not the goal and/or there is no progress, then CTOs should be referred to operators who perform these procedures routinely. Ultimately, CTO PCI should be performed by operators who are facile with all CTO PCI techniques.

Dr. Goyal: Finally, what are the implications for training the future generation of interventional cardiologists, as the field continually expands and becomes increasingly more nuanced in several different directions, including structural, peripheral, and congenital spaces?

Dr. Allana: CTO PCI is much different from routine or even complex non-CTO PCI. Just like structural, peripheral, or congenital heart disease, this is a separate specialty within interventional cardiology. Having a growth mindset is key. The techniques and equipment used in performing CTO PCI continue to evolve, and many programs have identified the need to train fellows in CTO and complex PCI by offering a dedicated fellowship year. Fellows interested in this field should seek out those training opportunities.

Biography

Dr. Salman Allana is an Assistant Professor of Internal Medicine at UT Southwestern Medical Center and Director of the Complex Coronary Artery Disease and Chronic Total Occlusion (CTO) Program. A board-certified interventional cardiologist, Dr. Allana specializes in the management of complex and high-risk coronary interventions, with a clinical and research focus on CTO PCI, cardiogenic shock, coronary physiology, and mechanical circulatory support.

Dr. Allana received his medical degree from the Aga Khan University in Pakistan before completing his internal medicine residency and fellowships in cardiovascular disease and interventional cardiology at the University of Wisconsin. He went on to complete advanced training in CTO and CHIP (Complex and High-Risk Indicated PCI) at the Minneapolis Heart Institute.

A Fellow of both the American College of Cardiology and the Society for Cardiovascular Angiography and Interventions, Dr. Allana has served on the Structural Heart Disease Council and contributed to numerous peer-reviewed publications and major cardiology textbooks, including Topol’s Textbook of Interventional Cardiology and Manual of Chronic Total Occlusions. He is widely recognized for his commitment to advancing complex coronary care through both innovative practice and academic leadership.