VQI analysis highlights impact of PAD on dialysis access outcomes 

Peripheral artery disease (PAD) is a strong predictor of poor outcomes after hemodialysis access creation, according to a recent study led by Mahmoud Malas, MD, using data from the Vascular Quality Initiative (VQI). Vascular Specialist spoke with Malas about the study’s findings and what they mean for preoperative planning, risk stratification and postoperative surveillance in dialysis access patients. 

Vascular Specialist: Can you provide an overview of the study and its primary objective? 

Mahmoud Malas, MD: This is an interesting study because the prior literature looked at patients with PAD getting bypass or stent or another procedure to revascularize their limb to see if dialysis affects the outcome. This is the first time it was done in reverse. We looked at patients getting dialysis and we wanted to see how PAD affects the outcome.  

Specifically, we looked at the impact of peripheral arterial occlusive disease on outcomes of dialysis access surgery, with a focus on the upper extremity. This is not a coincidence because PAD is very prevalent among patients with end-stage renal disease undergoing dialysis. Depending on the literature you look at, anywhere between 17% to 48% of patients on dialysis have PAD.  

This particular relationship, the effect of PAD on dialysis, has not been studied before and is not very well characterized. We focused on arteriovenous fistula and graft. We wanted to see how PAD affects access function, loss of patency and complications that can happen after the procedure, such as mortality, length of stay, bleeding and thrombosis post-op and steal syndrome. We compared outcomes between patients who have PAD and those who don’t. We also compared different stages of PAD and how it impacts outcomes of dialysis access. 

Vascular Specialist: What were the most important results from the study? 

Malas: The very interesting finding was that the severity of PAD was associated with progressively worse outcomes after upper extremity hemodialysis access creation. We had a very large cohort and that's the beauty of the VQI. There were 78,600 dialysis access procedures included. Of those, 33% did not have PAD and 61% had asymptomatic PAD. A small percentage, 3%, were claudicants and 4% had critical limb threatening ischemia (CLTI).  

We found that patients with PAD had the lowest rate of diabetes and were less likely to be on preventive medication like aspirin or a statin. The patients with claudication tended to be older, White, have a history of smoking and have higher rates comorbidity, like coronary artery disease and congestive heart failure. For asymptomatic PAD patients, they were more likely to be female. Patients with CLTI were the youngest group, but they had the highest rate of diabetes. We used a regression model to try our best to adjust for these cofounders.  

After adjusting for all the different variables, the 30-day mortality increased progressively as PAD severity progressed. Asymptomatic PAD patients had a 55% increased risk in the odds of mortality 30 days post-op. Claudicants had almost double the odds and patients with CLTI had a three-fold increased risk. 

The second thing we looked at is the length of hospital stay. We found patients with asymptomatic PAD and CLTI had an increased length of stay. Claudicants and CLTI were both independently associated with increased risk of steal syndrome. Additionally, all PAD stages were associated with loss of primary patency at six months. Unfortunately, the VQI doesn’t have a lot of long term data and it's hard to follow up on patients with dialysis. But at six months, we found that there was five-fold increase in the risk of losing the patency of the fistula. 

Vascular Specialist: How should PAD status be incorporated into preoperative risk stratification and dialysis access planning? 

Malas: That's a very important question because our findings have several implications for clinical decision making. First, recognizing that the patient has PAD, even if they're asymptomatic, should prompt us to individualize access planning. Second, a comprehensive, preoperative vascular assessment is crucial. That includes evaluation of material inflow, vessel diameter and physiologic reserve. When there's significant inflow disease or significant PAD involved, the inflow needs to be corrected before dialysis access creation. Third, we need to optimize medical therapy for these patients. Finally, the post-operative surveillance should be closer in patients with PAD. This allows early detection of stenosis or ischemic complications like steal syndrome. If we find a stenosis early on, we can intervene on it before the patient loses the access completely.  

We teach in vascular surgery that anytime you evaluate a patient for access, you need to feel their pulse, you need to make sure they have good radial flow, you need to look at the Allen test and make sure there's perfusion through the deep and superficial palmar arch. The reality, unfortunately, is that it doesn't happen every single time. Even if you feel one of the pulses are missing, not necessarily every patient gets evaluated further after that.  

One of the cool things about vascular surgery is that we run vascular labs and we do physiologic studies. Part of my protocol for vascular lab study is that any patient who's getting dialysis should get a preoperative evaluation. That should not only include the diameter of the veins, but looking at the brachial artery, the radial artery, the ulnar artery, the diameter and the flow. If we found it on a physical exam, the study can be confirmatory. We also look at the subclavian artery to see if there's inflow disease.  

The interesting part is, even if the patient is asymptomatic, that can affect the outcome. So, how do you identify these patients? You can see them in a physical exam and see they have gangrene on their toe or they can tell you that they can't walk to the mailbox without having pain but a lot of these patients don't even know they have PAD. We need to be more diligent in identifying PAD because even if they're asymptomatic, the outcome is going to be different. 

Vascular Specialist: If you could give one key takeaway from this study, what would it be? 

Malas: The key takeaway is that PAD, even in asymptomatic form, is a strong predictor of poor outcomes following dialysis access creation. As disease severity progresses, the risk of 30-day mortality, prolonged length of stay and loss of patency significantly increase. Identifying PAD before surgery can help guide risk assessment and procedure planning. The data also support closer follow-up after surgery, which can improve outcomes for these patients. 

Vascular Specialist: What future research would you like to see to build upon these findings? 

Malas: We have a few limitations that point to areas for future research. For instance, our PAD classification relied on clinical documentation rather than objective measurement. We did not have ankle brachial indexes (ABI) evaluated. Further study should incorporate that data because we can precisely make the diagnosis of PAD and we can quantify it based on how severe the arterial disease is. We didn’t have data on prior intervention or revascularization. That could also influence both PAD classification and outcomes. The biggest limitation is the six month follow up. We need longer follow up studies to look at the long-term durability. We also like only looked at primary patency and not functional patency. Further study needs to be done to look at that.