Introduction:
Improvement in exercise capacity is a therapeutic goal of percutaneous coronary intervention (PCI) for stable coronary artery disease (CAD). Cardiopulmonary exercise testing (CPET) provides an accurate quantification of cardio-respiratory fitness through analysis of ventilatory gas exchange (VGE). The aim of this secondary analysis from the ORBITA trial is to determine the placebo-controlled effect of PCI on VGE parameters and determine if pre-randomisation exercise capacity predicts the placebo-controlled efficacy of PCI.
Methods:
Following a 6-week medication optimisation phase, patients with severe single vessel CAD underwent pre-randomisation treadmill CPET using the smoothed modified Bruce protocol. Patients were then randomly assigned to PCI or a placebo procedure. At the end of the 6-week follow up period, patients underwent repeat CPET before being unblinded to treatment allocation.
Results:
CPET data was available for 195 patients (mean age 66.1 ± 9.1, 73.3% male). At baseline, peak oxygen uptake (VO
2
) was 21.5±6.7ml/kg/min in the PCI arm (n=102) and 20.6±6.6ml/kg/min in the placebo arm (n=93). At follow up, there was no significant benefit from PCI over a placebo procedure for any ventilatory gas exchange (peak VO
2
, p=0.826; O
2
-pulse plateau, p=0.638) or haemodynamic parameter (rate-pressure product, p=0.215). Although PCI resulted in significantly improved patient-reported freedom from angina (OR, 2.58 [95% CI, 1.35-14.92] p=0.004) and angina frequency score (OR, 1.73 [95% CI, 1.02 to 2.96], p=0.0432), there was no detectable interaction between peak VO
2
and these endpoints (P
interaction(int)
=0.715 and P
int
=0.588 respectively). Similarly, pre-randomisation peak VO
2
did not predict the placebo-controlled benefit of PCI on physical limitation (P
int
=0.293), quality of life (P
int
=0.380), EuroQOL 5 visual analogue score (P
int
=0.695), Canadian Cardiovascular Society angina class (P
int
=0.120) or exercise time (P
int
=0.897).
Conclusions:
When assessed against placebo, PCI does not improve VGE or exercise capacity, assessed by CPET. Furthermore, pre-randomisation exercise capacity does not predict the placebo-controlled effect of PCI on symptom relief, even in patients with lower functional capacity.
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