RESUMEN
Background:@#Endothelial dysfunction, the initial pathogenic factor in atherosclerosis, can be alleviated via transient limb ischemia. We observed the effects of regular transient limb ischemia (RTLI) on atherosclerosis in hypercholesterolemic rabbits.@*Methods:@#Twenty-eight rabbits were randomized to control, cholesterol, sham, ischemia groups (n=7 each) between October 2010 and March 2011. They were fed a normal diet in the control group and hypercholesterolemic diet in other groups for 12 weeks. Six cycles of RTLI were performed once per day on the ischemia group. Serum samples were prepared to measure the total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) before the experiment (W0), at the end of weeks 4, 8, 12 (W4, W8, W12). The whole aorta was harvested at W12 and stained using Sudan IV to identify the plaque. The plaque area was measured using Image J. Results were analyzed by analysis of variance or rank sum test.@*Results:@#Concentrations of TC in the cholesterol group were higher than those in the control group at W4 (29.60 [23.75, 39.30] vs. 1.00 [0.80, 1.55], Z = –2.745, P = 0.006), W8 (41.78 [28.08, 47.37] vs. 0.35 [0.10, 0.68], Z = –2.739, P = 0.006), W12 (48.32 [40.04, 48.95] vs. 0.61 [0.50, 0.86], Z = –2.739, P = 0.006). Similar results were obtained for HDL-C and LDL-C. Serum concentrations of TC, HDL-C, and LDL-C in the hypercholesterolemic groups had no differences (all P > 0.05). The percentage of plaque area in the cholesterol group was higher than that in the control group (47.22 ± 23.89% vs. 0, Z = –2.986, P = 0.003). Square root of the percentage of plaque area was smaller in the ischemia group than that in the cholesterol (0.44 ± 0.13 vs. 0.67 ± 0.18, P = 0.014) or sham groups (0.44 ± 0.13 vs. 0.61 ± 0.12, P = 0.049).@*Conclusion:@#In hypercholesterolemic rabbits, RTLI might prevent atherosclerosis progression by reducing the percentage of plaque area.
RESUMEN
Introducción La edad es un predictor independiente de riesgo en pacientes con enfermedad coronaria. Esto podría explicarse por la falta de adaptación a la isquemia miocárdica aguda. El precondicionamiento es un mecanismo por el cual episodios repetitivos de isquemia inducen en el miocardio una tolerancia mayor a episodios subsiguientes. Objetivo Evaluar el desarrollo de precondicionamiento isquémico en pacientes añosos. Material y métodos Se incluyeron 65 pacientes sometidos a angioplastia coronaria electiva (< 70 años [n = 47] y ≥ 70 años [n = 18]). Se evaluó el desarrollo de precondicionamiento durante tres períodos de oclusión coronaria. Por ECG intracoronario se midió la elevación del ST al final de cada dilatación y se registró el porcentaje de resolución del ST a la tercera dilatación respecto del máximo valor registrado. Los datos se presentan como mediana e intervalo intercuartil 25/75%. Resultados No hubo diferencias significativas en las características clínicas basales. El máximo ST registrado, el ST a la tercera dilatación y el porcentaje de resolución del ST fueron 14 (9/24) mm, 8 (4/14) mm y 23,8% (0/55,5) para los pacientes jóvenes y 9,5 (5/18) mm (p = ns), 6,5 (4/ 16) mm (p = ns) y 5,5% (0/20) (p = 0,04) para los añosos. Al estratificar por grupos etarios, la proporción de pacientes que alcanzaron una resolución del ST ≥ 50% mostró una distribución lineal por chi cuadrado de tendencia (p = 0,025). Conclusiones Nuestro estudio sugiere que el precondicionamiento isquémico se encontraría disminuido en pacientes añosos. La funcionalidad de este mecanismo menguaría en forma progresiva con el envejecimiento.
Introduction Age is an independent risk predictor in patients with coronary disease. This could be explained by the lack of adaptation to acute myocardial ischemia. Preconditioning is a mechanism whereby repeated ischemia episodes induce in the myocardium an increased tolerance to further episodes. Objective To assess the development of ischemic preconditioning in elderly patients. Material and methods Sixty five patients who underwent elective coronary angioplasty were enrolled (<70 years [n=47] and ³70 years [n=18]). Preconditioning development was assessed during three periods of coronary occlusion. ST elevation at the end of each dilation was measured by intra coronary EKG, and ST resolution percentage after the third dilation was recorded and compared to the maximum recorded value. Data are presented as mean and inter-quartile interval 25/75%. Results There were no significant differences in the clinical baseline characteristics. The maximum ST recorded, ST after the third dilation and ST resolution percentage were 14 (9/24) mm, 8 (4/14) mm y 23.8% (0/55.5) for the young patients and 9.5 (5/ 18) mm (p = ns), 6.5 (4/16) mm (p=ns) and 5.5% (0/20) (p=0.04) for the elderly. Upon stratification per age group, the ration of patients that reached an ST resolution ≥ 50% showed a linear distribution by chi square for trend (p=0.025). Conclusions Our study suggests that ischemic preconditioning would be decreased in elderly patients. The functionality of this mechanism would progressively decrease with aging.