Derivation and validation of the ISAR score to predict the risk of repeat percutaneous coronary intervention for recurrent drug-eluting stent restenosis.

BACKGROUND

The treatment of drug-eluting stent (DES) in-stent restenosis (ISR) is challenging as it has a high risk of recurrence.

AIMS: The aim of this analysis was to develop and validate a model to predict the risk of repeat percutaneous coronary intervention (PCI) for recurrent DES-ISR.

METHODS

A retrospective, observational analysis was performed including consecutive patients treated with PCI for DES-ISR at two centres in Germany. Included patients were randomly divided into training and validation cohorts. Two regression analyses identified factors associated with repeat PCI for recurrent DES-ISR up to 1 year. The discriminative ability of the resultant model was then compared to a benchmark ISR classification model using bootstrap resampling. A classification and regression tree analysis and a numerical scoring system (the ISAR score) were used to predict the risk of repeat PCI for recurrent DES-ISR based on the identified predictors.

RESULTS

We included 1,986 patients in the current analysis, divided randomly into training (1,471 patients, 1,778 lesions) and validation (515 patients, 614 lesions) cohorts. Four factor variables (a non-focal ISR pattern, a time interval to ISR of <6 months, ISR of the left circumflex artery and ISR in a calcified vessel) were associated with repeat PCI for recurrent DES-ISR at 1-year follow-up. On bootstrap resampling analysis, the C-statistic for the model including these four variables was 0.60 (95% confidence interval [CI]: 0.57-0.63), whereas the C-statistic for the benchmark ISR classification model was 0.54 (95% CI: 0.52-0.57), a difference that was statistically significant (delta C-statistic 0.062; 95% CI: 0.035-0.094; p<0.001). The cumulative incidence of repeat PCI for recurrent DES-ISR was over three times higher in DES-ISR lesions with an ISAR score of ≥3 in comparison to lesions with an ISAR score of 0.

CONCLUSIONS

This study developed and validated a risk prediction model for repeat PCI for recurrent DES-ISR at 1-year follow-up. This model served to generate the ISAR score, a standardised tool that can be used to predict the 1-year risk of repeat PCI for recurrent DES-ISR.