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Reference: ORBITA trial (Lancet 2017 Nov 1 early online) (level 2 [mid-level] evidence)
- Percutaneous coronary intervention (PCI) with stents may be considered in patients with stable single-vessel stenosis that is symptomatic despite optimized medical therapy, but previous trials assessing its potential benefit were not blinded.
- The recent ORBITA trial is a sham-controlled double-blinded trial in which 200 adults with stable symptomatic single-vessel coronary stenosis were randomized to PCI vs. sham procedure and were assessed for exercise capacity and symptoms at 6 weeks. All patients had intensive antianginal medication optimization before randomization.
- The ORBITA trial was powered to detect a 30 second difference in change from baseline in cardiopulmonary exercise capacity, assessed as a treadmill test that could be stopped for any one of a number of reasons.
- PCI did not significantly increase exercise capacity compared to the sham procedure, but several factors prevent this result from being definitive. The effects of PCI on angina are unclear: there were non-significant differences in favor of PCI in angina-specific outcomes, but this trial is likely underpowered to detect an effect on them.
PCI with stent implantation may be considered for patients with stable single-vessel stenosis that is symptomatic despite optimized medical therapy (J Am Coll Cardiol 2017). PCI has not been shown to reduce mortality or risk of myocardial infarction in these patients, and while some trials have shown that it may reduce angina, others have not and none were blinded (Can J Cardiol 2013, Circ Cardiovasc Interv 2012). The recent ORBITA trial is a sham-controlled double-blinded trial evaluating PCI in 200 adults with stable symptomatic single-vessel coronary stenosis ≥ 70% occlusion. Exclusion criteria included recent acute coronary syndrome, left main stem coronary disease, previous coronary artery bypass grafting, and other cardiopulmonary conditions. All patients had intensive 6-week antianginal medication optimization with 1-3 telephone consultations/week. Patients were then randomized to PCI with drug-eluting stents vs. sham procedure (at least 15 minutes of sedation). All patients were given dual antiplatelet therapy. Double blinding continued until the 6-week follow-up assessment. The primary outcome was the difference between groups in a change in cardiopulmonary exercise capacity, assessed with exercise on a treadmill until symptoms (angina, dyspnea, or fatigue), heart rhythm or blood pressure abnormalities, or marked ST-segment deviation were observed. The trial was powered to detect a 30 second difference in the mean change from baseline in exercise time.
The mean exercise times at baseline were 528 seconds with PCI vs. 490 seconds with the sham procedure (statistical comparison not reported). Exercise time increased by mean 28.4 vs. 11.8 seconds for a non-significant difference of 16.6 seconds (95% CI -8.9 to +42 seconds). There were also no significant differences in the rates of angina improvement (in 52% vs. 45% by the Canadian Cardiovascular Society angina grading scale), rates of freedom from angina (in 39% vs. 29%), or changes from baseline in angina frequency or stability (by the Seattle Angina Questionnaire) (each of these differences favored PCI, but they are related and so should not be considered independent from one another). Differences in quality of life (EQ-5D-5L) and risk of death (Duke Treadmill Score) were also not significant. No patients died, and 5 had perioperative major bleeding.
The ORBITA trial found that PCI added to optimized antianginal medication did not significantly increase exercise capacity at 6 weeks more than a sham procedure. It also did not find significant differences between groups in angina-specific outcomes. However, multiple factors prevent these results from being definitive. The 95% CI in the difference in increase in exercise capacity cannot exclude clinically significant differences in favor of PCI. Also, it is unclear how the difference in mean baseline exercise capacity affects subsequent gains. Regarding angina-specific outcomes, this trial did not find statistically significant differences between groups, but it was not powered to detect an effect on angina (the primary outcome of exercise capacity was assessed as a treadmill test that could be stopped for any one of a number of reasons). Moreover, the difference in rates of freedom from angina was similar to the statistically significant difference found in the much larger COURAGE trial (NEJM 2007). Together, these points suggest that PCI in addition to optimized medical therapy might reduce angina but that this trial was underpowered to detect this effect. Finally, whether or not these results persist beyond the 6-week follow-up—far less than previous trials—remains to be seen. On the other hand, the uses of a sham control and double blinding are important design characteristics that reduce bias compared to other trials, particularly for pain and other subjective outcomes. Overall, the ORBITA trial presents evidence that any benefit on functional outcomes of PCI for patients with single-vessel stenosis have yet to be definitively demonstrated.
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