Detrimental sequelae on the wall of the internal mammary artery caused by hydrostatic dilation with diluted papaverine solution.

We studied the effect of hydrostatic dilation of the internal mammary artery used for coronary revascularization in 10 patients (aged 45 to 79 years, median 63 years). Diluted papaverine solution was injected in the lumen of distal segments of the internal mammary artery, the musculophrenic artery, or the superior epigastric artery that had been obtained at operation; injection was followed by hydrostatic dilation not exceeding a sheer force of 50 gm. In 12 control patients (aged 42 to 76 years, median 64 years) in whom the internal mammary artery had also been harvested for elective myocardial revascularization, similar arterial segments were wrapped in sponges soaked in papaverine solution of the same dilution. In the nondilated group the median (with interquartile range) number of fenestrations in the internal elastic lamina increased from the elastic (21, 7) to the elastomuscular (41, 11) and muscular segments (89, 12) (elastic-elastomuscular: p = 0.006; elastic-muscular: p = 0.006; elastomuscular-muscular: p = 0.003) (Wilcoxon signed-rank test). In none of the three histologic segments were full-thickness disruptions of the intima and disruptions of the internal elastic lamina seen. Similarly, in the dilated group the number of fenestrations in the internal elastic lamina increased from the elastic (25, 18) to the elastomuscular (43, 9) and muscular (100, 13) segments (p values 0.01, 0.01, and 0.006, respectively). In addition, in 20% of the elastic sections, in 17% of the elastomuscular sections, and in 35% of the muscular sections of the dilated group, disruptions of the intima and internal elastic lamina were seen. Comparison of the number of fenestrations in internal elastic lamina in the three histologic segments between the nondilated and dilated groups revealed a significantly greater value in the muscular segments of the latter group (p = 0.01) (Mann-Whitney U test). We concluded that (1) hydrostatic dilation of the internal mammary, musculophrenic, and superior epigastric arteries may have detrimental effects on the histologic characteristics of the intima and the internal elastic lamina and (2) the number of fenestrations in the internal elastic lamina of these arteries is related to the presence or absence of elastic lamellae in the media.