Take for example this angiogram on shown below. Do you think the this LAD stenosis is flow limiting? Why not vote here and see what others think?
When you learn angiography you quickly realise that the interpretation is difficult. When you work for a number of bosses you start to see a difference in their practice. Some always see a moderate lesion as severe, or a severe lesion as critical. The phrase "the angiogram often underestimates the severity of disease" is often be heard in the catheter lab control room as the guide catheter is being opened ready for angioplasty. Whilst there is usually agreement about the mild (<30%) and severe (>80%) lesions it is the moderate ones which are most difficult and unfortunately most common.
As I teach my fellows the percent stenosis is the wrong way to think about lesions, rather we should say whether we believe a lesion to be flow limiting or not. Flow limitation is dependent on the stenosis but also on the reference vessel size, the lesion length, the size of the territory supplied by the vessel and the presence or absence of collaterals. The issue of interpretation is vital to the individual patient since it determines what treatment is recommended, You don't want a cardiologist to put in a stent or offer bypass surgery if your coronary artery lesion is not flow limiting.
Recent studies have revealed what we knew all along namely that when coronary artery disease is moderate it is not possible to accurately know by visual assessment whether the lesion(s) are flow limiting or not. We need better methods not based on anatomy but rather on physiology. I have previously written about the RIPCORD trial but recently a large French registry has published its results which support the idea that the angiogram is difficult to interpret and that use of a pressure wire to measure fractional flow reserve (FFR) alters the cardiologists decision making.
The R3F study looked at 1000 people having a diagnostic angiogram. The vessels were assessed and significant lesions documented. The patients symptoms and the results of any non-invasive investigations were considered and a recommendation made as to whether the patient should have medical therapy, angioplasty or bypass surgery. After this the cardiologists performed a pressure wire measurement (FFR) of any stenosis. The results were then used to determine whether the stenosis was flow limiting and with this information in hand the treatment recommendation adjusted. So for example if a patient had a 40% stenosis on the angiogram with medical therapy recommended initially but then the pressure wire was significant (e.g. FFR 0.74) the recommended treatment would be to offer an angioplasty.
Using the pressure wire data the overall number of people recommended for medical therapy, angioplasty or bypass did not change but the decision for an individual patient changed 43% of the time. Overall the decision changed in 33% of patients initially recommended to have medical therapy and 50% of patients recommended to have angioplasty or bypass surgery.
These results are very important for individual patients since the treatment recommendation means the difference between just taking tablets versus having a procedure or an operation. We don't know yet whether a pressure wire guided approach makes a difference to clinical endpoints such as survival, mortality, rates of heart attacks and a large trial is needed to answer this question.
For the moment when a moderate stenosis is diagnosed the patient should be asking their cardiologist what is the FFR?