PARR-2
FDG-PET viability to guide revascularization, a pragmatic randomized management trial
Quick Answer
PARR-2 (Beanlands et al., J Am Coll Cardiol 2007) was the randomized controlled trial that tested whether FDG-PET viability imaging to guide management improves outcomes in patients with severe left-ventricular dysfunction and suspected coronary disease being considered for revascularization. In the overall population, PET-assisted management did not significantly beat standard care for the composite cardiac outcome — but a prespecified subgroup that actually adhered to PET recommendations, at an experienced center (the Ottawa-FIVE substudy), did benefit. It frames the real-world role and limits of viability imaging.
The trial
Design: randomized controlled trial, 430 patients with severe LV dysfunction and suspected coronary disease considered for revascularization, work-up, or transplant. Randomized to management assisted by ¹⁸F-FDG-PET viability imaging versus standard care without PET. Primary endpoint: a composite of cardiac death, myocardial infarction, or cardiac hospitalization.
Key result
In the intention-to-treat population, FDG-PET–assisted management did not significantly reduce the composite cardiac outcome versus standard care. However, outcomes improved when PET recommendations were followed, and the Ottawa-FIVE substudy (experienced center, integrated PET-and-management team, adherence to recommendations) showed a significant benefit — highlighting that the value of viability imaging depends on acting on the result and on local expertise.
Why it mattered
PARR-2 is the key randomized data point on FDG-PET viability–guided management. Its nuanced result — neutral overall, beneficial when recommendations are followed at experienced centers — tempered enthusiasm for routine viability-driven revascularization and shaped how viability testing is positioned: useful for decision-support in selected patients, not a guarantee of outcome improvement. It sits alongside STICH in the broader viability-and-revascularization debate.
Context & caveats
PARR-2 was a pragmatic management trial: crossover, non-adherence to PET recommendations, and evolving heart-failure therapy dilute an intention-to-treat signal. The STICH viability substudy likewise questioned whether viability status predicts a survival benefit from surgery. Viability imaging (FDG-PET, or rest-redistribution thallium) is best used where its result will genuinely change the revascularization decision.
Self-Check
Q1. What did PARR-2 test?
Answer: Whether FDG-PET viability–guided management improves cardiac outcomes versus standard care in severe LV dysfunction considered for revascularization.
Q2. What was the overall (intention-to-treat) result?
Answer: No significant benefit for PET-assisted management over standard care in the whole population.
Q3. When did PET-guided management help?
Answer: When PET recommendations were followed at an experienced center — the Ottawa-FIVE substudy showed a significant benefit.
Q4. What is the practical teaching point?
Answer: Viability imaging helps only when its result will change the decision and is acted upon; it is decision-support, not a guaranteed outcome improver.
Key References
- Beanlands RSB, et al. F-18-fluorodeoxyglucose positron emission tomography imaging-assisted management of patients with severe left ventricular dysfunction and suspected coronary disease: a randomized, controlled trial (PARR-2). J Am Coll Cardiol 2007;50:2002–2012. doi:10.1016/j.jacc.2007.09.006
Evidence & sources
https://nuc.med/parr-2-trial/ Report an issue