Aims: Fractional flow reserve measurement is based upon achieving maximum hyperemia. A 40 microg intracoronary (IC) adenosine bolus sometimes seems insufficient, and we therefore sought to assess the possible role of 100-150 microg boli in routine.
Methods and results: 108 intermediate (49+/-16%) stenoses were consecutively studied with 6F catheters. A history of myocardial infarction in the territory of the explored artery or myocardial hypertrophy were the exclusion criteria. Mean FFR was 0.82+/-0.12 with a 40 microg adenosine bolus and decreased to 0.80+/-0.12 and 0.80+/-13 respectively with 100microg and 150 microg boli (P<0.001 vs 40microg in both cases; 100 vs 150 microg, NS). The 40 microg bolus failed to diagnose 8 out of 30 (27%) significant stenoses (i.e., final FFR <0.75). The large boli led to 12 (11%) transient asymptomatic and spontaneously resolving AV blocks without other side-effects.
Conclusion: FFR underestimated a quarter of intermediate stenoses with the currently used 40microg IC adenosine bolus. A large bolus up to 150 microg appears to be accurate and safe for routine FFR measurement.