Novel CHIP score may predict complex PCI outcomes, proposes JACC study

Complex high-risk and indicated percutaneous coronary interventions (CHIP-PCI) is a rapidly growing field that remains somewhat ill-defined with considerable variability among operators. Unlike risk assessment for coronary artery bypass grafting (CABG), which is based on established scoring systems like the STS (Society of Thoracic Surgeons) score or EuroSCORE II models, data on risk stratification for PCI are less robust.

In a recent study published in JACC Cardiovascular Interventions, Protty et al have proposed a new scoring system-the CHIP score based on both patient and procedural characteristics to define and predict outcomes of CHIP-PCI. This score was found to be associated with increased in-hospital major adverse cardiac and cerebrovascular events (MACCE). An arbitrary cut-off value of 5 has been proposed to define a CHIP case.

The authors studied more than 300,000 patients who underwent PCI in the United Kingdom to evaluate the baseline patient characteristics and procedural variables associated with increased risk MACCE, not just procedural complexity. A multiple logistic regression model was developed to identify variables associated with in hospital major adverse cardiac or cerebrovascular events (MACCE) and to construct a CHIP score. The cumulative effect of this score on patient outcomes was examined.

The investigators concluded following factors were associated with MACCE events

7 patient factors were :

1. age ≥80 years,

2. female sex,

3. previous stroke,

4. previous myocardial infarction

5. peripheral vascular disease,

6. ejection fraction <30%,

7. and chronic renal disease

The 6 procedural factors were

1. rotational atherectomy

2. left main PCI,

3. 3-vessel PCI,

4. dual arterial access,

5. left ventricular (LV) mechanical support

6. total lesion length >60 mm

Together these 13 factors constitute the CHIP score. As the CHIP score increased, an exponential increase in in-hospital MACCE and other adverse clinical outcomes was observed. Furthermore, authors noted the increase in CHIP score, as higher-risk PCI cases were performed, over the period of the analysis. This might be due to aging of the population, development of advanced PCI techniques and increased use of mechanical circulatory support.

The novel scoring system presented in the current study includes both patient and procedural parameters, which emphasizes that the concept of CHIP is based, not only on lesion complexity, but also on patient baseline characteristics.

For example although a Type A lesion in a patient with multiple comorbidities may be technically straightforward to treat with PCI, such patients remain at high risk of adverse outcomes. Therefore, in considering the implications of the current study, the development of tailored pathways for PCI cases, regardless of whether the CHIP score is driven by procedural or patient complexity, might lead to improvements in the clinical outcomes of these high risk cases.

An interesting finding is that the use of mechanical circulatory support has the strongest association with MACCE. Although the use of mechanical circulatory support is aimed to reduce MACCE, the increased risk noted is mainly due to the fact that LV support is preferentially used in patients with an inherently high-risk profile such as multivessel or left main disease, as well as low LV systolic function and tenuous hemodynamics.

Another interesting finding is that chronic total occlusion (CTO) was not considered a CHIP factor. The reason might be predominance of straightforward lower-risk CTO-PCI, a miscategorization of lesion severity, or that historically, many CTO-PCI interventions were not fully committed attempts.

Assessing cumulative CHIP factors and scores might be future target for risk modification such as focusing complex PCI to specific operators/centers, optimizing access site, intravascular imaging, and pharmacology.

Source: JACC CI: J Am Coll Cardiol Intv. 2022 Jan, 15 (1) 39–49