Translesional PRESSURE Measurements to Assess Clinical Relevance of a Mesenteric Artery Stenosis (PRESSURE-study)

Chronic mesenteric ischemia (CMI) is an incapacitating disease with a vast impact on quality of life due to severe abdominal pain after a meal, resulting in fear of eating and subsequent severe weight loss. CMI has an incidence of 9.2 per 100,000, which increases with age to up to 44.3 per 100,000 in persons of ≥80 years. These incidence rates are higher than the incidence rates of other more well-known diseases, such as esophageal cancer (4.3 per 100,000) or ruptured abdominal aortic aneurysms (7.0 per 100,000), and even approximates the incidence of Crohn's disease (10.9 per 100,000). The prevalence of atherosclerotic mesenteric artery stenosis, the leading cause of CMI, is even higher (6-29%). An extensive collateral circulation protects the gut against ischemia in the majority of patients. Hence, not all mesenteric artery stenoses result in CMI and only those stenoses that are hemodynamically significant should be treated. Treatment decisions for atherosclerotic CMI are currently based on history, stenosis severity on imaging, and signs of mesenteric ischemia during a functional test. However, sufficiency of the collateral circulation cannot be assessed, resulting in substantial failure of patient-reported symptom relief after stent placement (27-31% in single vessel disease), unnecessary complications and avoidable healthcare expenses.

The Dutch Mesenteric Ischemia Study group (DMIS) consists of experts in the field of CMI and aims to improve both the quality of care and the quality of life of CMI patients by initiating and designing studies to provide patient-centered and evidence-based solutions to pending challenges in the field of CMI. In recent years the DMIS has been searching for a reliable tool to assess hemodynamic significance of a mesenteric artery stenosis, while accounting for the collateral circulation, in order to guide treatment decisions and avoid clinically unbeneficial revascularization procedures. In a retrospective study flow velocities were increased in the unaffected mesenteric artery when either the CA or SMA were stenosed. The increased blood flow in the unaffected vessel could indicate a well-functioning collateral network where blood flow is rerouted to prevent chronic mesenteric ischemia.

Another retrospective cohort study reports that intra-arterial pressure measurements, using a 4Fr catheter, could predict clinical success of mesenteric artery revascularization with an 86% sensitivity and 83% specificity. In this retrospective study, pressure gradients were obtained after administration of a vasodilator. With these pressure measurements, the Pd/Pa ratio and the fractional flow reserve (FFR) were measured. The Pd/Pa ratio is the pressure distal to the stenosis divided by pressure in the aorta and the FFR is the Pd/Pa ratio under hyperemic conditions, after administration of a vasodilator. Mesenteric artery pressure measurements could be a promising tool for the assessment of hemodynamic and clinical relevance of mesenteric artery stenosis, since pressure gradients will only occur in mesenteric arteries with a severe stenosis and an insufficient collateral circulation.

The previously performed retrospective study yielded promising results, but had some methodological limitations. Pressure measurements in the conducted study were only obtained in a subset of CMI patients by the decision of the interventional radiologist, with pressure measurements in general only performed when the radiologist was in doubt about the significance of the stenosis. This could have potentially led to selection bias and makes reproducibility of this study difficult to the general population of CMI patients as a whole. In the proposed study, the investigator will perform pressure measurements in the general population of CMI patients with a consensus diagnosis of CMI who are scheduled for endovascular treatment, hypothesizing that stenosis grade (%) alone cannot predict hemodynamic significance accurately. By obtaining pressure measurements in all CMI patients, including borderline, high-grade stenoses and occlusions, the investigators aim to evaluate the (in)sufficiency of the mesenteric collateral network by measuring pressure gradients over the stenotic lesion. The investigators hope such pressure gradients can predict clinical treatment success for all CMI patients. If positive results are obtained in this study, the investigators hope these measurements can serve as a decision-making tool in suspected CMI patients (to stent or not to stent).

In an in-vitro study (currently under submission) in which postprandial states in the superior mesenteric artery (SMA) and celiac artery (CA) were simulated, pressure measurements were obtained using a 4Fr macrocatheter, microcatheter and pressure wire. It showed that especially for a stenosis ≥75% or a longer stenosis, the 4Fr catheter tended to overestimate the fractional flow reserve (FFR) when compared to the microcatheter, due to partial obstruction of the residual vessel lumen by the relatively large size of the 4Fr catheter compared to microcatheter or pressure wire. Taking this into consideration together with a wider applicability and lower costs, they recommended the microcatheter for clinical use.

In addition, intra-arterial stress pressure measurements with a vasodilator (nitroglycerin) could make the measurements more reliable, since intestinal ischemia mainly occurs after a meal when blood flow is maximal and expected to increase by 30-150%. Ischemia in CMI is thus temporary and this dynamic process causes false negative tests when blood flow is not maximal. Intra-arterial injection of nitroglycerin is able to increase the mesenteric blood flow, thereby challenging the compensatory capacity of the mesenteric circulation and predicting clinical success of revascularization. In a retrospective study, the Pd/Pa ratio after administration of nitroglycerin yielded the most promising results with the highest sensitivity and specificity.

Intra-arterial nitroglycerin is already routinely administered during coronary angiography for cardiology patients. Moreover, intra-arterial vasodilators can be used as treatment for acute nonocclusive mesenteric ischemia (NOMI). In the retrospective study, no adverse events related to intra-arterial nitroglycerin had occurred, making intra-arterial pressure measurements a safe and useful tool to guide future treatment decisions (to stent or not to stent). Successful implementation of this strategy could result in a substantial reduction of the number of unbeneficial mesenteric artery revascularizations, thereby avoiding potential loss of quality of life due to complications and a reduction of healthcare expenses.

Intra-arterial pressure measurements could also enlighten the debate on other topics regarding mesenteric artery revascularization. Current guidelines define a stenosis severity of ≥70% as significant in single vessel disease, while a ≥50% stenosis of the SMA is considered significant when accompanied by a ≥70% stenosis of the CA. These definitions are mainly based on expert opinion and cannot be supported with solid evidence. Intra-arterial pressure measurements could prove whether use of the current definitions should be continued or whether the definitions should be revised. The latter seems more probable, since hemodynamic significance of a mesenteric artery stenosis depends on a combination of both stenosis severity and the compensatory capacity of the collateral circulation, which cannot be assessed on computed tomography angiography (CTA) or magnetic resonance angiography (MRA). A future definition could state that pressure measurements are mandatory in all patients to confirm that revascularization is indicated.

The current recommendation to revascularize both mesenteric arteries in patients with multivessel disease of CA and SMA is another example of a recommendation that could be revised based on results of intra-arterial pressure measurements. Pressure measurements could identify those patients in whom stenting of both vessels is indicated. Measurement of normal pressures in the CA, after SMA revascularization, suggests that the CA stenosis is no longer hemodynamically relevant. Revascularization of the CA is in this case no longer indicated and both the possible complications of CA revascularization and the unneeded expenses of CA stenting can be avoided.

Intra-arterial pressure measurements are currently the most promising tool to guide clinical decision-making in patients with suspected CMI. Implementation of pressure measurements could result in major improvements in quality of life by tailoring treatment to the patient's needs, thereby improving the clinical success of mesenteric artery revascularization and decreasing complication risks. This will ultimately result in a reduction of population-based healthcare costs by facilitating allocation of healthcare resources to those patients actually benefitting from treatment. The DMIS has designed a multicenter study to determine the predictive value of intra-arterial pressure measurements after administration of nitroglycerin using a microcatheter to predict clinical success of mesenteric artery revascularization, to set an optimal cut-off for the guidance of treatment decisions, and to determine cost-effectiveness of future clinical implementation of intra-arterial pressure measurements.

Primary Objective:

• To assess the predictive performance of the Pd/Pa ratio after administration of a vasodilator to predict the clinical success of mesenteric artery stenting