Results
A total of 370 patients (mean age, 61.5 ± 11 years; 84.6% males) was prospectively enrolled in this registry. Clinical, angiographic, and procedural characteristics of the study population are listed in Table 1 and Table 2. According to study definitions, the Resolute ZES was used for an off-label indication in 311 patients (84%), accounting for 397 lesions (86.3%). Off-label indications to Resolute ZES implantation are reported in Table 3. Acute MI <72 hours represented the most frequent off-label indication, since it was found in 187 patients (50.5%). Patients in the on-label group were more likely to undergo PCI for stable coronary artery disease and had a higher baseline ejection fraction. In contrast, off-label patients were more likely to have a previous PCI history, longer lesions, and more frequently type C lesions treated. As a result, the latter group received more stents, with longer stented segments.
Clinical follow-up was available in 366 patients (98.9%), with a mean of 17.3 ± 6 months and is reported in Table 4. Follow-up duration was not statistically different between on- and off-label patients (P=.89).
MACE rate for all patients enrolled in the registry was 8.5% (95% CI, 6%-11.8%). In on-label patients, there was a lower MACE occurrence (3.4%; 95% CI, 0.9%-11.5%) as compared to off-label patients (9.4%; 95% CI, 6.7%-13.2%), but this difference was not statistically significant (P=.13). The relative risk of MACE for the off-label compared with on-label group was 2.97 (95% CI, 0.69–12.8). Kaplan-Meier curves representing the cumulative incidence of MACE at follow-up are shown in Figure 1. TVR rate in the overall cohort was 5.2% (95% CI, 6%-11.8%), with no significant difference (P=.75) between the on-label (3.4%; 95% CI, 0.9%-11.5%) and off-label group (5.5%; 95% CI, 3.5%-8.7%). Death and MI rates in the overall population were 4.1% (95% CI, 2.5%-6.6%) and 2.7% (95% CI, 1.5%-4.9%), respectively (of interest, all cases occurred in off-label patients). Nine patients had ST, with an overall ST rate of 2.5% (95% CI, 1.3%-4.6%). Four cases were early ST and 5 were late ST. Noteworthy, 5 out of 7 definite STs occurred in patients who underwent PCI with overlapping Resolute ZESs. Two late STs were due to premature dual-antiplatelet therapy discontinuation. No very late ST occurred during the study period. Among 185 acute MI patients who completed follow-up, clinical outcomes were: MACE 7% (95% CI, 4.1%-11.6%), death 5.4% (95% CI, 3%-9.7%), MI 2.7% (95% CI, 1.2%-6.2%), TVR 2.7% (95% CI, 1.2%-6.2%), and ST 2.7% (95% CI, 1.2%-6.2%).
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Figure 1.
Probability of major adverse cardiac events (MACE) at follow-up between patients with off- and on-label indications. Time-to-event curves were calculated with the Kaplan-Meier method and the log-rank test was to compare between-group differences.
A multivariable model that included insulin-treated diabetes mellitus, three-vessel disease, previous revascularization, and previous MI showed that off-label Resolute ZES implantation did not significantly affect MACE occurrence (HR, 3.96; 95% CI, 0.89–17.6; P=.071). Differently, previous revascularization was associated with MACE (HR, 7.01; 95% CI, 1.41–9.37; P=.008). The Hosmer-Lemeshow statistic was not significant (P=.87), confirming that the model appropriately fit the data.