Microvascular resistance in response to iodinated contrast media in normal and functionally impaired kidneys

Abstract

SummaryContrast‐induced nephropathy (CIN) is considered to result from intrarenal vasoconstriction, and occurs more frequently in impaired than in normal kidneys. It was hypothesized that iodinated contrast media would markedly change renal blood flow and vascular resistance in functionally impaired kidneys. Thirty‐six patients were enrolled (32 men; mean age, 75.3 ± 7.6 years) undergoing diagnostic coronary angiography and were divided into two groups based on the presence of chronic kidney disease (CKD), defined as an estimated glomerular filtration rate (eGFR) of < 60 mL/min per 1.73 m2 (CKD and non‐CKD groups, n = 18 in both). Average peak velocity (APV) and renal artery resistance index (RI) were measured by Doppler flow wire before and after administration of the iodinated contrast media. The APV and the RI were positively and inversely correlated with the eGFR at baseline, respectively (APV, R = 0.545, P = 0.001; RI, R = −0.627, P < 0.001). Mean RI was significantly higher (P = 0.015) and APV was significantly lower (P = 0.026) in the CKD than in the non‐CKD group. Both APV (P < 0.001) and RI (P = 0.002) were significantly changed following contrast media administration in the non‐CKD group, but not in the CKD group (APV, P = 0.258; RI, P = 0.707). Although renal arterial resistance was higher in patients with CKD, it was not affected by contrast media administration, suggesting that patients with CKD could have an attenuated response to contrast media.

Pre-procedural renal resistive index accurately predicts contrast-induced acute kidney injury in patients with preserved renal function submitted to coronary angiography

“…All these observations are line with the observed propensity towards increased RRI in subjects exhibiting CI-AKI. Last but not least, invasive measurement of intra-renal blood flow directly before and after CM administration revealed a significant increase of resistance index (defined as ratio of mean blood pressure and average peak renal velocity) and decrease of peak systolic velocity [7]. …”

“…During both pre- and post-procedural examination patients remained in supine position, as the majority of the patients were confined to this position following CA via femoral access. The ideal method should employ the measurement of resistive index by an invasive Doppler flow wire [7], which regrettably was not implemented in our study. Still, this technique may prolong the duration of the procedure and increase CM use and could trigger renal circulatory complications.…”

“…A wide range of CI-AKI risk factors has so far been established, such as impaired baseline kidney function, volume of CM applied, dehydration, advanced age, diabetes mellitus and atherosclerosis severity [1–3, 6]. The development of renal injury is believed to be triggered by high osmolality and viscosity of CM, leading to increased renal vascular resistance [7] and renal tubular hypoxia, eventually causing tubular cell apoptosis [8]. Preexisting increased vascular stiffness, reflected by high central arterial pulse pressure could facilitate CI-AKI via impaired renal blood flow auto-regulation [9].…”

“…Yet, several factors can interfere with RRI values, including pulse blood pressure, heart rate and rhythm, presence of significant aortic valve stenosis, age, renal interstitial disease or vascular compliance [16]. Also, patients with chronic kidney disease were shown to have an altered and delayed vascular response to contrast media [7]. …”

Blunted renal vasoconstriction in patients with subclinical contrast‐induced renal injury

“…5 Recently, we reported that the Doppler flow wire method can be used to directly show the haemodynamics of the microvasculature of the kidney, and we demonstrated changes in microvascular haemodynamics following the administration of an iodinated contrast medium in a clinical setting. 6 However, changes in renal haemodynamics have not yet been fully validated in terms of the subclinical degree of kidney injury. All patients in the present study were scheduled for elective angiography without coronary intervention.…”