Instantaneous Wave-Free Ratio versus Fractional Flow Reserve in Patients with Stable Angina Pectoris or Acute Coronary Syndromes - iFR-SWEDEHEART

Contribution To Literature:

Highlighted text has been updated as of November 4, 2021.

The iFR-SWEDEHEART trial showed that iFR was noninferior to FFR at preventing adverse cardiac events.


The goal of the trial was to evaluate if functional lesion assessment by instantaneous wave-free ratio (iFR) would be noninferior to FFR among patients with stable angina or acute coronary syndromes.

Study Design

  • Randomized
  • Parallel

Patients undergoing functional assessment of an indeterminant coronary lesion were randomized to iFR (n = 1,019) versus FFR (n = 1,018). Revascularization was recommended if the iFR value was ≤0.89 or the FFR value was ≤0.80.

  • Total number of enrollees: 2,037
  • Duration of follow-up: 12 months
  • Mean patient age: 67 years
  • Percentage female: 25%
  • Percentage with diabetes: 23%

Inclusion criteria:

  • Patients with stable angina or acute coronary syndrome (unstable angina or non-ST-segment elevation myocardial infarction [NSTEMI])
  • Indeterminant coronary stenosis 40-80% (non-culprit vessel in acute coronary syndrome patients)

Exclusion criteria:

  • Life expectancy <1 year
  • Killip class III or IV
  • Inability to tolerate adenosine
  • Previous coronary artery bypass grafting with patent graft to the interrogated vessel
  • Heavily calcified or tortuous vessel where inability to cross the lesion was expected

Other salient features/characteristics:

  • Radial access: 83%
  • Mean iFR: 0.91
  • Mean FFR: 0.82
  • Mean number of lesions evaluated: 1.55 with iFR vs. 1.43 with FFR (p = 0.002)
  • Functionally significant lesions: 29.2% with iFR vs. 36.8% with FFR (p < 0.0001)
  • Mean number of stents: 1.58 with iFR vs. 1.73 with FFR (p = 0.048)

Principal Findings:

The primary outcome, incidence of all-cause death, MI, or unplanned revascularization at 12 months, occurred in 6.7% of the iFR group versus 6.1% of the FFR group (p = 0.007 for noninferiority). The results were the same among tested subgroups.

Secondary outcomes:

  • Death: 1.5% for iFR vs. 1.2% for FFR
  • MI: 2.2% for iFR vs. 1.7% for FFR
  • Unplanned revascularization: 4.6% for iFR vs. 4.6% for FFR
  • Mild chest discomfort during the procedure: 2.6% with iFR vs. 31.4% with FFR

Long-term outcomes at 5 years:

  • Composite endpoint: hazard ratio (HR) 1.09 (95% confidence interval [CI] 0.90-1.33)
  • All-cause mortality: HR 1.20 (95% CI 0.89-1.62)
  • MI: HR 1.00 (95% CI 0.70-1.44)
  • Unplanned revascularization: HR 1.02 (95% CI 0.79-1.32)


Among patients undergoing functional determination of an indeterminant coronary stenosis for stable or unstable coronary disease, iFR was noninferior to FFR. The threshold to revascularize was ≤0.89 for iFR and ≤0.80 for FFR. Adverse cardiac events were similar between study groups at 12 months and 5 years. There was less procedure-associated chest pain in the iFR group. Slightly more lesions were interrogated with iFR, possibly due to the simplicity of the procedure and lack of procedure-related chest pain, which can sometimes occur with adenosine. The preferential use of iFR over FFR for indeterminant lesions can be considered.


Presented by Dr. Matthias Götberg at the Transcatheter Cardiovascular Therapeutics (TCT) Conference, Orlando, FL, November 4, 2021.

Götberg M, Christiansen EH, Gudmundsdottir IJ, et al., on behalf of the iFR-SWEDEHEART Investigators Instantaneous Wave-free Ratio versus Fractional Flow Reserve to Guide PCI. N Engl J Med 2017;376:1813-23.

Editorial: Bhatt DL. Assessment of Stable Coronary Lesions. N Engl J Med 2017;376:1879-81.

Presented by Dr. Matthias Götberg at the American College of Cardiology Annual Scientific Session (ACC 2017), Washington, DC, March 18, 2017.

Keywords: ACC17, ACC Annual Scientific Session, Acute Coronary Syndrome, Angina, Stable, Angioplasty, Coronary Angiography, Coronary Stenosis, Myocardial Infarction, Myocardial Revascularization, Outcome Assessment, Health Care, Registries, TCT21, Transcatheter Cardiovascular Therapeutics

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