To the Editor:
It was with great interest that we read the excellent article by de la Torre et al1 demonstrating the use of intravascular ultrasound (IVUS) in evaluating intermediate truncal lesions and suggesting that a cut-off value of 6 mm2 for the minimum luminal area (MLA) is safe in the long term.
The prognostic importance of left main trunk disease (LMT) is unquestionable. For this reason, the need arose to find a useful tool, whether physiological with a pressure guide wire, or anatomical using IVUS, which would permit us to adequately evaluate the severity of the defect and predict cases of future coronary events. Our team communicated the results of using the fractional flow reserve (FFR) in evaluating moderate LMT lesions in the short term.2 We studied 27 consecutive patients with 30%-50% apparent angiographic stenosis; of these cases, 20 did not undergo LMT revascularisation due to having a negative FFR. These patients presented a minimum luminal diameter (MLD) of 2.21 (0.61) mm, and a mean FFR of 0.88 (0.04). The MLD of the patients with a positive FFR was 1.8 (0.46) mm2. After a follow-up period of 3.5 years, there were no cardiovascular events apart from that described in our article2; only 3 patients died, from non-cardiovascular causes. This data confirms the long-term safety of postponing revascularisation with the additional information provided by the pressure guidewire.
Our study, like that of de la Torre et al,1 describes a subgroup of patients from daily clinical practice for which intracoronary diagnostic techniques are necessary to provide a more reliable diagnosis, given the obvious prognostic implication for LMT lesions. A small number of complications have been described for new treatments, such as the pharmacoactive stent or minimally invasive surgery, but it will always be higher if the treatments are unnecessary.
Both studies present similar clinical and angiographic characteristics, particularly a lesion MLD <2 mm in patients with a positive FFR and an MLA of £6 mm2. This could indicate that in patients with a MLD <2 mm, regardless of the stenosis percentage, one may opt for intervention rather than obtaining additional information using intracoronary diagnostic techniques. Similar results are described in studies by Beche et al3 and Jasti et al4 on evaluating intermediate lesions using intracoronary diagnostic techniques; all of these studies show that patients with coronary stenosis of the LMT and a MLD <2 mm are the ones with severe anatomical or functional stenosis. Even Abizaid et al5 state that patients with cardiovascular events and moderate LMT lesions are those with a MLD of 2 mm.
In conclusion, for moderately severe LCO defects, we are able to gather more information by physiological examination with a pressure guide wire or by anatomical examination with IVUS, both of which are complementary, safe techniques for postponing intervention. An MLD <2 mm would indicate a severe case in which it would be unnecessary to use either of the above techniques.