Resting Pd/Pa and haemodynamic relevance of coronary stenosis as evaluated by fractional flow reserve.

BACKGROUND: Fractional flow reserve (FFR) currently represents the gold standard in the evaluation of the haemodynamic relevance of coronary stenoses. However, both intracoronary and intravenous adenosine may be tolerated poorly by some patients. Therefore, considerable interest had been focused in the last few years on new adenosine-free indexes to define the haemodynamic relevance of coronary stenoses. So far, few data have been reported on resting Pd/Pa and its correlation with FFR as evaluated with high-dose intracoronary adenosine administration, which is the aim of the current study.

MATERIALS AND METHODS: FFR was assessed in 120 patients with 137 intermediate lesions during cardiac catheterization by a pressure-recording guidewire (PrimeWire). FFR was calculated as the ratio of the distal coronary pressure to the aortic pressure at hyperaemia. Intracoronary doses of adenosine were administered up to 720 μg as intracoronary boli. Exclusion criteria were as follows: (a) allergy to adenosine; (b) baseline bradycardia (heart rate <50 bpm); (c) hypotension (blood pressure <90 mmHg); and (d) refusal to provide signed informed consent.

RESULTS: High doses of intracoronary adenosine were well tolerated, with no major side effects. Increasing doses up to 720 μg progressively decreased FFR values and increased the percentage of patients showing an FFR less than 0.80. Resting Pd/Pa showed good accuracy in the identification of patients with significant FFR values (<0.80) [area under the curve=0.9 (0.84-0.96), P<0.0001]. Using receiver-operating characteristic curves, we identified a threshold less than 0.93 as the best accurate cut-off value in the prediction of a positive FFR value. A value up to 0.88 was associated with a 100% positive predictive value, whereas a value of at least 0.95 was associated with a 95% negative predictive value.

CONCLUSION: This study showed that in intermediate lesions, resting Pd/Pa was related linearly to FFR. We identified 0.93 as the best cut-off value in the prediction of haemodynamically significant coronary stenosis as evaluated by FFR. However, cut-off values of 0.88 and 0.95 could provide the maximal predictive positive and negative values, suggesting the additional use of FFR only in patients with resting values within this range.