Numerical analysis of the pressure drop across highly-eccentric coronary stenoses: application to the calculation of the fractional flow reserve.

BACKGROUND: Fractional flow reverse (FFR) is the gold standard assessment of the hemodynamic significance of coronary stenoses. However, it requires the catheterization of the coronary artery to determine the pressure waveforms proximal and distal to the stenosis. On the contrary, computational fluid dynamics enables the calculation of the FFR value from relatively non-invasive computed tomography angiography (CTA). METHODS: We analyze the flow across idealized highly-eccentric coronary stenoses by solving the Navier-Stokes equations. We examine the influence of several aspects (approximations) of the simulation method on the calculation of the FFR value. We study the effects on the FFR value of errors made in the segmentation of clinical images. For this purpose, we compare the FFR value for the nominal geometry with that calculated for other shapes that slightly deviate from that geometry. This analysis is conducted for a range of stenosis severities and different inlet velocity and pressure waveforms. RESULTS AND CONCLUSIONS: The errors made in assuming a uniform velocity profile in front of the stenosis, as well as those due to the Newtonian and laminar approximations, are negligible for stenosis severities leading to FFR values around the threshold 0.8. The limited resolution of the stenosis geometry reconstruction is the major source of error when predicting the FFR value. Both systematic errors in the contour detection of just 1-pixel size in the CTA images and a low-quality representation of the stenosis surface (coarse faceted geometry) may yield wrong outcomes of the FFR assessment for an important set of eccentric stenoses. On the contrary, the spatial resolution of images acquired with optical coherence tomography may be sufficient to ensure accurate predictions for the FFR value.

[Incidence of ischemic heart disease in the HERMEX study and its association with classical cardiovascular risk factors]. / Incidencia de cardiopatía isquémica en el estudio HERMEX y su asociación con los factores de riesgo cardiovascular clásicos.

OBJECTIVES: Knowledge about the incidence of coronary heart disease in our country is scarce and its sources are not comparable. Our aim was to determine the incidence of ischemic heart disease in a population cohort in a 7 years of follow-up, as well as the risk associated with the different classical cardiovascular risk factors. METHODS: Cohort study with a population sample of 2833 subjects, selected by the simple random method in a population between 25 and 79, from the Don Benito - Villanueva de la Serena (Badajoz) health area, response rate was 80.5%. All episodes of angina pectoris, lethal and non-lethal myocardial infarction were collected in individuals with no previous history of cardiovascular disease. Cumulative incidences and incidence rates adjusted per 100,000 person-years by sex and overall were calculated. RESULTS: From 2833 initial cohort participants, 103 were excluded due to a history of cardiovascular disease and 61 for losses, 2669 completed the follow-up (94.2%). The median follow-up was 6.9 years (IR 6.5-7.5), 56.4% women; 59 events were recorded. The overall incidence rate of ischemic heart disease was 327 cases/100,000 person-years, corresponding to 470 cases/100,000 for men and 211 cases/100,000 people-years for women. The classical cardiovascular risk factors that were associated with a higher risk of presenting events in the follow-up were dyslipidemia and arterial hypertension, in addition to male sex and age. CONCLUSIONS: The incidence of ischemic heart disease in the urban-rural population of Extremadura is high. The classical cardiovascular risk factors most strongly associated with events were dyslipidemia, and arterial hypertension.