EFFECTS OF BALLOON ANGIOPLASTY AND STENT IMPLANTATION ON INTRARENAL ECHO-DOPPLER VELOCIMETRIC INDEXES

This study was aimed at examining whether four intrarenal echo-Doppler velocimetric indices (pulsatility and resistive indices, acceleration and acceleration time) can be useful for assessing the effects of ren al artery dilation obtained with either angioplasty or stent implantat ion. Echo-Doppler studies were performed in 63 hypertensive patients w ith 68 renal artery stenoses (39 atherosclerotic and 29 fibromuscular) prior to and within five days after the dilation procedures (55 angio plasties, 13 stent implantations), which resulted in an average reduct ion of arterial narrowing from 79% to 20%. In 24 patients, the velocim etric indices were also examined in relationship to the venoarterial d ifferences of plasma renin activity and of angiotensin II across the s tenotic kidneys. We found that after dilation the values of the four i ndices had returned within the normal range in all but three arteries (one false negative for resistive index and two for acceleration time) . However, decrements in acceleration time was the only factor to be s ignificantly correlated with the reduction of arterial narrowing. More over, post-dilation values of this index were, on average, slightly bu t significantly higher in arteries that at follow-up developed resteno sis rather than in those that remained patent. For similar reductions in arterial narrowing the absolute changes of all indices were similar in atherosclerotic and fibromuscular stenotic arteries and, in a subs et of the atheromatous arteries, were also similar after angioplasty a nd stent implantation. No relationship was found with the changes in t he venoarterial differences of plasma renin activity and angiotensin I I. It appears that these intrarenal velocimetric indices and, in parti cular, acceleration time reliably reflect the technical success of ren al artery dilation. The acceleration time index may also be valuable f or predicting the restenosis of the dilated vessel. None of the indice s, however, mirrors the functional consequences of removal of renal ar tery stenosis as expressed through the changes in transrenal gradients of the components of the renin-angiotensin system.