Functional renal hemodynamics in patients with and without renal artery stenosis

Atherosclerosis consists of a chronic systemic inflammatory response in the
walls of arteries, resulting in plaques within the arterial wall. In case of
coronary artery and renal artery stenosis, these plaque lesions can result in
cardiac angina and hypertension, respectively.
Treatment of these stenoses by percutaneous transluminal angioplasty and stent
placement may lead to improvement in perfusion in affected arteries. However,
the effect of these interventions in both heart and kidneys are variable.
Pressure and flow measurement is a technique used in cardiac catheterization to
measure the significance of atherosclerotic lesions in coronary arteries. A
pressure difference across a stenosis indicates the severity of the lesion.
This technique has proven to be a reliable parameter to determine the
significance of an atherosclerotic plaque lesion in patients with coronary
disease. At present current techniques are insufficient to identify patients
with renal artery stenosis, who may benefit from PTA and stent placement. We
believe that measurement of pressure and flow in renal arteries may identify
the culprit lesion in patients with renal artery stenosis. In the present study
our aim is to assess the reproducibility of pressure and flow measurements in
one of the renal arteries in patients undergoing elective cardiac
catheterization.

This study aims to investigate the feasibility and reproducibility of
simultaneous pressure and flow measurements in the renal artery, and derived
parameters in patients undergoing elective coronary pressure and flow
measurements, at rest and during pharmacologically induced hyperaemia.

Cohort study with invasive measurements

Participants are exposed to an additional 30ml of contrast medium for renal
angiography. The same 0.014-inch guide wire with pressure and flow sensors
(Combowire, Volcano, San Diego, US) that is used to perform the elective
coronary pressure and flow measurements is subsequently placed in one of the
renal arteries and advanced, if present, past a stenosis. A renal hyperaemic
response is induced by an intra-renal bolus of 50µg*kg-1 dopamine. This can be
performed safely without any significant systemic effects on haemodynamics. The
procedures as proposed are preformed twice. The duration of the coronary
catheterization will be lengthened by 20 minutes. A total of 50ml of blood is
collected during catheterization.
Renal pressure and flow measurements as proposed in this study may enable us to
determine the hemodynamic functionality of a given renal artery stenosis and
the viability of renal microvasculature. These factors, we believe, greatly
determine the effectiveness of percutaneous transluminal angioplasty in renal
artery stenosis, and may ultimately aid in selecting patients with unilateral
or bilateral renal artery stenosis who will benefit from PTA with stent
placement.