Intravascular imaging and 12-month mortality after unprotected left main stem PCI : an analysis from the British Cardiovascular Intervention Society database

Selected in JACC Cardiovascular Interventions by D. Milasinovic , P. Xaplanteris

This retrospective analysis of the BCIS nationwide database compares the outcomes of unprotected left main PCI with and without the use of intravascular imaging (IVUS or OCT).

Reviewers

Dejan Milasinovic

@MilasinD18

Interventional cardiologist / Cardiologist

Clinical Centre of Serbia - Belgrade, Serbia

Panagiotis Xaplanteris

@panosxap

Interventional cardiologist / Cardiologist

CHU Saint-Pierre - Bruxelles, Belgium

Our Comment

Why this study – the rationale/objective?

The role of intravascular imaging to guide left main (LM) PCI is not yet firmly established, having currently a class IIa, level of evidence B recommendation in the ESC guidelines. This retrospective analysis of the BCIS nationwide database compares the outcomes of unprotected left main PCI with and without the use of intravascular imaging (IVUS or OCT).

How was it executed – the methodology?

• 11,264 unprotected left main PCI procedures performed between 2007 and 2014 were included.
• Patients were split in two groups, use of intravascular imaging versus conventional angiography, and propensity matching was used to account for differences in baseline characteristics.
• Logistic regression was used to explore the association between imaging and outcomes, including 12-month mortality and in-hospital MACCE (composite of death, stroke, or myocardial infarction or reinfarction, depending on indication).

What is the main result?

• The proportion of LM PCI to total PCIs increased from 2.0% in 2007 to 4.1% in 2014.
• A trend for increased use of intravascular imaging was noted (30.2% in 2007 to 50.2% in 2014, p <0.001).
• The factors associated with imaging use included stable angina presentation, bifurcation left main stem disease, previous PCI and radial access.
• The use of intravascular imaging was more frequent with the increasing operator experience, with the exception of the most experienced operators with the largest LM PCI volumes, where imaging use decreased.
• Imaging-guided LM PCI was associated with a lower rate of coronary complications, including fewer coronary dissections and lower rates of slow flow, and less in-hospital MACCE.
• Imaging guidance was also associated with a lower risk of 30-day (OR: 0.540; 95% CI: 0.430 to 0.680; p < 0.001) and 12-month (OR: 0.660; 95% CI: 0.570 to 0.770; p < 0.001) mortality.

Distal LM bifurcation

Distal LM bifurcation

Critical reading and the relevance for clinical practice

This nationwide retrospective analysis is important for a number of reasons.

First, it provides insights from a large scale, real-world database reflecting contemporary clinical practice and taking into account procedures from operators of varying expertise. The salutary effects of intravascular imaging for the percutaneous treatment of LM disease remain to be verified in a randomized controlled trial.

Second, the use of imaging is associated with lower MACCE and reduced mortality at 1 month and 1 year. Such an immediate benefit of an imaging modality on both a combined and a hard endpoint is hard to contest and makes the case for its widespread use in what is probably the most challenging anatomy for interventional cardiologists. However, this being a retrospective analysis from a registry, it is unknown if imaging was used both pre and post stenting and how it specifically modified the stenting procedure.

Third, the use of imaging results in more vessels being treated with more and longer stents implanted. Given the higher spatial resolution of IVUS and OCT compared to angiography, the underlying disease is put into evidence more accurately and therefore more diseased coronary segments demanding PCI come to attention.

Fourth, IVUS remains the modality of choice, with reported use in more than 90% of the imaging cases. Nonetheless, OCT emerges as an alternative modality, given its inherent restrictions (large diameter of the LM causing image dropout, use of contrast agent problematic in the setting of impaired kidney function).

Central to the overall interpretation is that in this observational study the patients treated without imaging were sicker, comorbidities such as peripheral arterial disease, chronic renal disease and low ejection fraction were more frequent in the angiography group as compared to the imaging group. Although the propensity matching can account for the difference in the known variables, the possibility of residual confounding cannot be ignored.

In summary, despite its observational character, this study provides valuable pieces of information regarding the potential of intracoronary imaging guidance to improve outcomes after LM PCI, with more pronounced benefit in complex lesions and seemingly regardless of the operator’s experience.