Wahaj Aman, Mohammad Hafizullah.
Instantaneous wave-free ratio (IFR)-AN emerging technique.
Pak Heart J Nov ;50(3):135-8.

The advent of fractional flow reserve (FFR)changed the landscape of viewing and interpreting coronary artery lesions, particularly intermediate ones. FFR is defined as ratio of the pressure distal to a stenosis (Pd) relative to the pressure proximal to the stenosis (Pa). For FFR to be accurate intra-coronary resistanc must be constant and minimal so that the change in pressure across a lesion is proportional to change in blood flow, this requires hyperemia induced by a vasodilating agent typically adenosine. The use of coronary physiology to guide revascularization has been found to improve patient outcomes and defer stenting of non-ischemic lesions compared with angio-graphic assessment. National Cardiovascular Data Registry (NCDR), FFR evaluation across US was being performed in only 6% of intermediate lesions. The lack of utilization primarily stems from the cost and administration of adenosine. Adenosine is contraindicated inpatients with asthma, severe COPD, bradycardia and hypotension. Additionally, it may require central venous access. In IFR-SWEDEHEART, 2,037 patients were enrolled at 15 centers in Sweden, Denmark and Iceland. A total of 2,019 patients in this study were treated according to protocol, with 1,012 patients receiving iFR and 1,007 receiving FFR. This documented a substantial reduction in patient discomfort, with just 3 % of iFR reporting discomfort compared to 68 % of FFR. A primary end point event occurred in 68 patients (6.7%) in iFR group and in 61 patients (6.1%) in FFR group (95% confidence interval [CI],?'1.5 to 2.8; p=0.007 for non-inferiority; hazard ratio, 1.12; 95% CI, 0.79 to 1.58; p=0.53). The rates of myocardial infarction,target-lesion re-vascularization, re-stenosis, and stent thrombosis did not differ significantly between the two groups. A significantly higher proportion of patients in the FFR group than in the iFR group reported chest discomfort during the procedure.Significant lesions were found in 29.2 percent of patients undergoing iFR and 36.8 percent undergoing FFR. To conclude, if there is a significant lesion that strongly correlates with stress tests, then one should go ahead and revascularize the indicated lesion. However, if the lesion is not absolutely correlating, then one should opt for iFR/FFR evaluation. With reduced procedure length, requirement of fewer stents and elimination of need for a vasodilator drug should translate into significant cost savings iFR appears to be more promising technology.

PakMediNet -Pakistan's largest Database of Pakistani Medical Journals - http://www.pakmedinet.com