Clinical utility of low-pressure implantation of drug-eluting stent into very small vessels

Determinants and prognostic implications of instantaneous wave-free ratio in patients with mild to intermediate coronary stenosis: Comparison with those of fractional flow reserve

The instantaneous wave-free ratio (iFR) is used for assessing the hemodynamic severity of a lesion, as an alternative to the fractional flow reserve (FFR). We evaluated the relationship between iFR and FFR in detail and the clinical significance of iFR in patients with mild to intermediate coronary artery stenosis. We recruited consecutive 323 patients (421 lesions) with lesions exhibiting 30% to 80% diameter stenosis on angiography in whom FFR and iFR were measured. In the total lesions, mean diameter stenosis was 48.6% ± 9.0%, and physiological significance, defined by FFR of 0.80 or less or by iFR of 0.92 or less, was observed in 32.5% or 33.5%, respectively. Mismatch between iFR and FFR was observed in 18.1% of the lesions. Clinical factors did not predict FFR value; however, gender, diabetes mellitus, aortic stenosis, anemia, high-sensitivity CRP value, and renal function predicted iFR value. In multivariate logistic analysis after adjustment for FFR value, gender (p < 0.001), diabetes mellitus (p = 0.005), aortic stenosis (p = 0.016), high-sensitivity CRP (p < 0.001), and renal function (p = 0.003) were all independent predictors of iFR value. In Kaplan-Meier analysis, the baseline iFR predicted the subsequent major cardiovascular events (MACE) (hazard ratio, 2.40; 95% CI, 1.16–4.93; p = 0.018) and the results of the iFR-guided strategy for predicting rates of MACE and myocardial infarction/revascularization were superior to those of the FFR-guided strategy. In conclusion, significant clinical factors predicted iFR value, which affected the prognostic capacity. The iFR-guided strategy may be superior in patients with mild to intermediate stenosis.

Clinical and angiographic factors predicting fractional flow reserve and explaining the visual-functional mismatch in patients with intermediate coronary artery stenosis

BACKGROUND

Visual-functional mismatch between coronary angiography and fractional flow reserve (FFR) has been reported, and the underlying reason remains poorly understood. Therefore, the relationship between angiographic measurements and FFR was evaluated, and predictors for FFR in intermediate coronary artery stenosis were determined.

METHODS

Consecutive 314 patients (405 lesions) with a lesion of 30-80% angiographic diameter stenosis who underwent invasive FFR were recruited. The myocardial area supplied by the coronary artery distal to the stenosis was evaluated using a modified version of the Bypass Angioplasty Revascularization Investigation (BARI) score. Participants underwent follow-up, and major cardiovascular events (MACE), including all-cause death, myocardial infarction (MI), and unplanned revascularization were recorded.

RESULTS

Although % diameter stenosis was correlated with FFR (R = 0.279, P < 0.001), diameter stenosis-FFR mismatch was observed in 37.8% of the lesions. Although FFR values were not associated with clinical factors, such as age, sex, and comorbidities, it was correlated with minimal lumen diameter (MLD), diffuse lesion, presence of proximal lesion, and BARI score. In addition, the lesions in left anterior descending (LAD) coronary artery showed low FFR values compared with those in the left circumflex coronary artery or right coronary artery. In multivariate logistic analysis, MLD (β coefficient = 0.330), diffuse lesion (β coefficient = -0.266), proximal lesion (β coefficient = -0.144), BARI score (β coefficient = -0.219), and LAD lesion (β coefficient = -0.293) were all independent predictors for FFR value. The estimated FFR value based on these factors showed smaller mismatch and higher sensitivity. No difference was observed in the event rates for MACE and MI or revascularization between the FFR-guided and estimated FFR-guided strategies.

CONCLUSIONS

MLD, diffuse lesion, proximal lesion, BARI score, and lesion vessel were independent predictors for FFR in intermediate coronary stenosis. Not only the extent of local lesion stenosis but also the amount of myocardial supply and the lesion location may determine the physiological significance and explain the visual-functional mismatch. The estimation of FFR by these factors may be useful in clinical practice.

[Proposed model of vascular trauma by mean of mechanical characterization of endovascular prostheses (stents) based on structural analysis by FEA]

OBJECTIVE

The accumulated evidence on angioplasty techniques with stents has raised a controversy about the factors that influence the final vascular response. Indeed, several studies have shown there might be re-stenosis between 30% to 40% about 6 months after placement, relating to the design of the device as one of the main causes. This paper proposes the functional characterization of endovascular stents, analyzing its mechanical influence in the vascular system and predicting implicit traumatic factors in the vessel.

METHODS

A structural analysis was made for several computational models of endovascular stents using Finite Element Analysis in order to predict the mechanical behavior and the vascular trauma. In this way, the stents were considered as tubular devices composed of multiple links under radial pressure loads, reflecting stress concentration effects.

RESULTS

The analysis allowed to visualize how the geometry of stents is adjusted under several load conditions, in order to obtain the response of "solid-solid" interaction between the stent and the arterial wall. Thus, an analysis was performed in order to calculate stress, and a conceptual model that explains its mechanical impact on the stent-vessel interaction, was raised, to infer on the functionality from the design of the devices.

CONCLUSIONS

The proposed conceptual model allows to determine the relationship between the conditions of mechanical interaction of the stents, and warns about the effects in what would be the operation of the device on the vascular environment.