When Bypass Surgery and Stents Are No Longer Possible

A complete guide for patients with advanced Peripheral Artery Disease and Chronic Limb-Threatening Ischemia — and what current research offers when standard treatments have stopped working

Written in the educational voice of Dr. York N. Hsiang, MB ChB, MHSc, FRCSC — Professor Emeritus of Surgery, UBC | Principal Investigator, Phase II ACP-01 Trial

If You Have Been Told There Is Nothing Left to Try, Read This First

You have already done the hard work. You showed up to every appointment, followed through with the procedures, and trusted the process — and yet, here you are.

A wound on your foot that will not heal. Pain in your leg that wakes you in the night. A surgeon you respect telling you, as gently as they can, that bypass surgery is no longer technically possible. That stenting cannot help. That the options have run out.

Perhaps the word amputation has been mentioned.

If that is where you are, this article was written for you — and for the family member or caregiver reading alongside you.

What follows is not a promotional pitch. It is a plain-language medical education resource based on current vascular science and peer-reviewed clinical research. My goal is to help you understand exactly what is happening in your leg, why conventional surgery sometimes cannot help, and what legitimate investigational research is now offering to patients in your situation.

You deserve honest information. Let’s start there.

Section 1: What Is Peripheral Artery Disease — and Why Does It Get Worse?

Peripheral Artery Disease, or PAD, is a condition where the arteries carrying blood to your legs become progressively narrowed or blocked. The underlying cause, in the vast majority of cases, is atherosclerosis — the gradual buildup of plaque made up of fat, calcium, and inflammatory tissue along the arterial wall.

Over time, this plaque narrows the artery from the inside. Less blood gets through. Less oxygen and nutrients reach the tissues of the leg and foot. Eventually, the gap between what the tissues need and what they receive becomes critical.

Who Is Most at Risk for PAD?

PAD is most common in people over 60 and is strongly associated with:

• Long-term smoking or a significant smoking history
• Type 1 or Type 2 diabetes, particularly when blood sugar has been difficult to control
• High blood pressure (hypertension) over many years
• Elevated cholesterol or triglycerides
• Chronic kidney disease
• A family history of heart disease or vascular disease
• Without effective treatment, the major amputation rate at one year is approximately 20–30%
• Cardiovascular events — heart attack and stroke — are significantly more common in patients with CLTI than in the general population
• The one-year mortality rate in patients with advanced CLTI is substantially higher than in those with less severe PAD
• Even after successful revascularization, patients require lifelong surveillance and medical management
• Open bypass surgery — using a vein or synthetic graft to route blood around a blocked artery, much like a highway detour
• Endovascular procedures — using catheters to reach the blockage from inside the artery, then opening it with a balloon (angioplasty) or holding it open with a metal stent
• Occluded — bypass grafts can close off when a blood clot forms or the disease progresses around the graft
• Restenosed — arteries treated with stents or angioplasty can re-narrow over time through a process called restenosis
• Changed the anatomy — repeated procedures can alter the arterial architecture in ways that make further surgery technically dangerous or impossible
• Florida, USA — under Florida Senate Bill 1768, which permits physician-supervised access to investigational therapies for eligible patients
• Toronto, Canada — through compassionate access pathways under physician oversight
• The Bahamas and Dominican Republic — through international research and access programs
• A high-volume academic vascular centre (most major university-affiliated hospitals)
• A vascular surgeon with specific experience in complex below-knee reconstruction
• An institution that performs regular multidisciplinary limb salvage rounds
• What is the published evidence base? Ask for the specific clinical trial data, the journal it was published in, and the patient population studied.
• What does the evaluation process involve? A legitimate program will conduct a thorough review of your imaging and medical history before offering any treatment recommendation.
• What are the realistic potential outcomes — and the risks? Honest programs discuss both possibilities with equal transparency.
• What does the comparator look like? For a no-option patient, the relevant comparison is not other surgical procedures — it may be major amputation or continued wound deterioration. Context matters when weighing an investigational option.
• Who is the clinical team, and what is their background? Medical leadership, institutional affiliations, and peer-reviewed publications are all signals of credibility.

Many people have more than one of these risk factors — and the combination significantly accelerates how quickly the disease progresses.

The Three Stages of PAD: From Mild to Limb-Threatening

PAD does not arrive all at once. It typically progresses through recognizable stages:

Stage 1 — Asymptomatic PAD

The arteries are narrowing, but the body compensates. No symptoms yet. Many people are unaware they have PAD at this stage. It is often found incidentally on a vascular ultrasound or ankle-brachial index test.

Stage 2 — Claudication

The legs begin to cramp or ache during walking, then recover with rest. This happens because the narrowed arteries can supply enough blood at rest, but cannot meet the increased demand of exercise. Most people with claudication can manage the condition medically and with supervised exercise.

Stage 3 — Chronic Limb-Threatening Ischemia (CLTI)

Blood flow is now so severely reduced that the tissues cannot meet even their basic needs — even at rest. This is the stage where patients develop the symptoms that bring them to seek urgent help: persistent leg and foot pain at night, wounds that refuse to heal, and in the most severe cases, tissue that begins to die.

Section 2: Recognizing Chronic Limb-Threatening Ischemia (CLTI)

CLTI is not just "bad circulation." It is a specific clinical condition with defined characteristics, and it carries a serious prognosis if not treated effectively. Understanding what CLTI looks and feels like is the first step toward getting the right care.

The Three Warning Signs of CLTI

1. Ischemic Rest Pain

This is pain in the foot, toes, or lower leg that occurs at rest — not just with walking. It is most severe at night, when the legs are horizontal and gravity no longer helps push blood toward the feet. Many patients describe having to hang their legs off the side of the bed, or sleep in a chair, to get any relief.

The pain is typically described as a burning or aching sensation in the foot or toes. It is not muscle cramps. It is the pain of tissue that is not receiving enough oxygen.

2. Non-Healing Wounds

Wounds on the foot, heel, toes, or lower leg that do not improve after weeks of appropriate wound care are a hallmark of CLTI. These wounds — also called ischemic ulcers — fail to heal because the tissue around them lacks the blood supply needed to support the cellular activity of wound repair.

Standard wound care treatments — dressings, antibiotics, offloading — can slow progression, but they cannot substitute for adequate circulation. Without restored blood flow, these wounds tend to worsen rather than improve.

3. Tissue Necrosis or Gangrene

In the most advanced cases, tissue begins to die. This may present as blackening or darkening of a toe, part of the foot, or a larger area of the lower leg. This is a medical emergency and typically leads to urgent amputation if circulation cannot be restored.

What the Numbers Tell Us About CLTI

CLTI is not a rare condition, and its consequences are serious. The clinical data consistently show:

These are sobering numbers. But they also explain why researchers and clinicians are working urgently to find better solutions — particularly for the patients for whom conventional surgery is no longer possible.

Section 3: Why Bypass Surgery and Stents Sometimes Stop Being an Option

When a patient is diagnosed with CLTI, the first goal is always to restore blood flow — a process called revascularization. Vascular surgeons approach this in two main ways:

When these procedures are successful, the results can be dramatic. Wounds heal. Pain resolves. Limbs are saved. For many patients, revascularization is an effective and durable solution.

But not for everyone. And not forever.

Why Some Patients Cannot Have Bypass Surgery or Stenting

The feasibility of revascularization depends entirely on anatomy — specifically, which arteries are blocked and what remains of the vessels below the blockage.

Bypass surgery requires two things: a usable conduit (typically a vein harvested from the patient’s own leg), and a target vessel below the blockage — a relatively healthy artery to connect the bypass to. In patients with disease limited to large vessels like the aorta or femoral arteries, these targets are usually available.

But in patients with disease that extends into the smaller calf and foot arteries — the tibial and peroneal vessels — there may be no suitable target remaining. There is nowhere for the bypass to attach. The plumbing has been compromised all the way to the end.

When Prior Procedures Have Already Failed

Many patients who are now facing “no-option” CLTI have already undergone revascularization procedures in the past. Over time, these interventions may have:

When multiple experienced vascular surgeons conclude that further reconstruction is not feasible, that is what the term “no-option CLTI” formally means. It is a recognized clinical designation. It is not a failure of the surgeon, and it is not a judgment about the patient. It is an anatomical reality — and it is more common than many patients realize.

Section 4: What Is Actually Happening in Your Leg — The Biology of Critical Ischemia

To understand why researchers are now studying biological therapies, it helps to understand what is actually happening at the tissue level in advanced CLTI. Because the problem — and the solution — is not only about large arteries.

The Visible Arteries Are Only Part of the Picture

When a surgeon looks at your angiogram — the imaging test that maps blood flow in the arteries — they are seeing the large and medium-sized vessels: the aorta, the femoral artery, the tibial arteries. These are the highways.

But the actual delivery of oxygen and nutrients to your tissues happens through a completely different system: the microcirculation — a dense, microscopic network of tiny capillaries and arterioles that threads through every muscle, every layer of skin, every healing wound.

In patients with long-standing diabetes and advanced PAD, the microcirculation itself is often severely damaged. The tiny vessels have thickened walls, reduced flexibility, and impaired function. This means that even when a large artery is successfully opened by surgery, the tissue downstream may no longer have the capillary infrastructure to benefit from the restored flow.

This is one of the central reasons why reopening a blocked artery does not always save the limb.

Why Non-Healing Wounds Are More Than a Blood Flow Problem

It is tempting to think of a non-healing wound as simply a wound that lacks enough blood. The reality is more complex.

When tissue is starved of oxygen — a state called ischemia — a cascade of biological events is triggered:

1. Cells shift to an inefficient, emergency form of metabolism that produces toxic byproducts
2. The toxic byproducts trigger a widespread inflammatory response
3. Inflammation damages the already-fragile blood vessels in the surrounding tissue
4. The damaged vessels impair the delivery of healing cells and growth factors
5. The wound environment becomes self-perpetuating: ischemia causes inflammation, inflammation worsens ischemia
6. A small volume of the patient’s blood is drawn through a standard peripheral blood draw — no surgery, no bone marrow procedure
7. The blood is processed in a specialized laboratory to isolate and concentrate the angiogenic progenitor cell population
8. The concentrated cells are then delivered by targeted injection into the ischemic tissue of the affected limb
9. The delivered cells release pro-angiogenic growth factors, stimulate the formation of new capillaries, and promote the biological conditions needed for tissue survival and wound healing

A non-healing wound, in this sense, is not a wound waiting for blood flow. It is a wound caught in a biological stalemate. Breaking that stalemate requires something different from mechanical pipe-clearing. It requires biological repair — rebuilding the microvasculature from within.

Section 5: Why Researchers Are Studying a New Type of Treatment

The recognition that a significant population of CLTI patients cannot benefit from conventional surgery has driven decades of serious scientific investment in an alternative: biological therapies that stimulate the body’s own repair mechanisms.

The foundational insight is this: the body already knows how to grow new blood vessels.

Angiogenesis: The Body’s Own Repair System

Angiogenesis is the process by which new capillaries and blood vessels form from existing ones. It is not a theoretical concept — it happens naturally in your body every time a wound heals or a tissue recovers from injury. Under normal circumstances, cells in an oxygen-deprived area release chemical signals — growth factors — that stimulate nearby blood vessels to sprout and grow new branches toward the ischemic tissue.

In younger, healthier patients, this process is relatively efficient. In patients with advanced PAD, diabetes, and the vascular damage that comes with decades of disease, the angiogenic response is significantly impaired. The body’s repair signal is weak. Fewer stem and progenitor cells are mobilized. The ischemic tissue is less responsive.

The question driving the research is: can this process be restored or amplified therapeutically?

Cell-Based Therapies: A Different Kind of Medicine

Early attempts to stimulate angiogenesis used gene therapy — delivering specific growth factor genes directly to ischemic tissue. The biology was promising, but clinical results were inconsistent. Delivering a single growth signal in isolation does not replicate the complex, co-ordinated biological process that normally occurs.

Attention then turned to cell-based therapies — approaches that use living cells to deliver the full, physiologically regulated mixture of growth signals that the body itself would produce in a functioning angiogenic response. The cells involved are called angiogenic progenitor cells — a population of specialized cells normally found circulating in the bloodstream that home to areas of low oxygen and participate in new vessel formation.

In patients with advanced PAD, these cells are present in reduced numbers and reduced function. The idea behind therapeutic delivery is to concentrate and deliver a meaningful quantity of these cells directly to the ischemic tissue — giving the body’s own repair system the resources it needs to do its job.

Section 6: Investigational ACP-01 — What the Research Shows

ACP-01 is an investigational autologous angiogenic cell therapy developed by Hemostemix. The term “autologous” is fundamental to understanding why this approach is distinct: the cells used in ACP-01 are derived exclusively from the patient’s own peripheral blood.

There is no donor involved. There is no risk of immune rejection. The therapy works with what your own body produces.

How ACP-01 Works: Step by Step

The process is designed to replicate and amplify what the body would naturally attempt — but cannot adequately achieve on its own in a patient with advanced PAD.

The Phase II Clinical Trial: What the Data Showed

A Phase II randomized controlled trial of ACP-01 was conducted at Vancouver General Hospital, one of Canada’s leading academic vascular centres. The trial enrolled patients with Rutherford Class 5 and 6 disease — the most severe categories of limb-threatening ischemia, representing patients with active tissue loss and gangrene.

A sub-analysis of the trial examined outcomes specifically in the cohort of patients who had baseline ulceration — active non-healing wounds at the time of enrollment. These are among the most medically complex and high-risk CLTI patients.

The data also showed that mortality at 12 months was 4.8% in the treated group compared with 12.5% in the placebo group.

Where ACP-01 Is Currently Available

Because ACP-01 remains investigational, patient access is currently limited to specific regulated pathways. These include:

In all cases, patients undergo a formal evaluation process — reviewing their imaging, medical history, and prior treatment — before any determination is made about suitability.

Section 7: How to Think About Your Options at This Stage

If you have reached the point where conventional revascularization is no longer possible, evaluating what comes next is one of the most important decisions you will face. Here is a framework for thinking about it clearly.

Step 1: Make Sure “No-Option” Is Genuinely the Conclusion

Before accepting that revascularization cannot help you, it is worth confirming that conclusion with more than one opinion. Vascular surgery is a technically demanding specialty, and expertise varies significantly between institutions. There are cases where a surgeon experienced in complex distal bypass or tibial-level reconstruction can identify an option that was not apparent elsewhere.

Consider seeking evaluation at:

That said, when multiple experienced surgeons at credible institutions have reached the same conclusion, it is reasonable to accept that conclusion and explore what research pathways may be available.

Step 2: Ask the Right Questions About Any Investigational Therapy

When evaluating any investigational option, ask these questions of the clinical team:

Step 3: Involve Your Care Team

Your primary care physician, your current vascular surgeon, and your wound care team all have valuable context about your specific situation. A legitimate investigational program will welcome communication with your existing care team — not discourage it.

If a program asks you to avoid sharing information with your doctor, that is a red flag.

A Final Word

Being told that standard treatments have been exhausted is one of the hardest things a patient can hear. The combination of fear, uncertainty, and physical pain that accompanies advanced CLTI is real, and I do not want to minimize it.

What I want to offer instead is this: accurate information, placed in your hands, at the moment you need it most.

There is real, peer-reviewed scientific evidence that biological approaches to limb ischemia may offer meaningful benefit to patients for whom no mechanical option remains. That evidence is early-stage — honest science always is, at some point in its development — but it is genuine, it has been published and scrutinized, and it is advancing.

The fact that you are reading this, researching, asking questions — that matters. The right next step is an honest conversation with a clinical team who can review your specific situation and tell you plainly whether you might be a candidate for ongoing research, and what that would actually involve.

You deserve clarity. You deserve time to ask questions without pressure. And you deserve to make whatever decision is ahead of you from a place of knowledge, not fear.

Frequently Asked Questions

These are the questions patients most often bring to their first conversation with our clinical team.

1. What does it actually mean to have “no-option” CLTI?

“No-option” CLTI is a recognized clinical designation for patients in whom standard revascularization procedures — bypass surgery, angioplasty, stenting — are not technically feasible, have already been attempted without lasting success, or carry unacceptably high procedural risk. It does not mean that nothing can be done about your condition. It specifically means that conventional mechanical restoration of blood flow through surgery is not available. Investigational biological therapies are being studied specifically for this patient population.

2. My bypass failed and my stent closed. Can I still be considered for investigational therapy?

Prior failed revascularization does not disqualify you from consideration for investigational therapy. The Phase II trial of ACP-01 specifically enrolled patients who were defined as having no conventional options remaining — including patients with prior failed bypass and stenting. Whether you are individually appropriate requires a review of your specific imaging and medical history. The best first step is to request an evaluation consultation.

3. My wound has not healed in three months. How long is too long to wait?

Any wound on the foot or lower leg in a patient with known PAD or diabetes that has not shown clear improvement after four to six weeks of appropriate wound care warrants urgent vascular evaluation. In CLTI patients, a non-healing wound is not simply a wound care problem — it is a sign of critically reduced perfusion. Delays in addressing the underlying vascular cause are consistently associated with worse outcomes, including higher rates of major amputation. Do not wait for the wound to become an emergency.

4. Should I get a second opinion before agreeing to an amputation?

Yes, without hesitation, and I would say this even as a vascular surgeon myself. A second — and sometimes third — opinion from an experienced vascular surgeon at a high-volume academic centre is entirely appropriate before proceeding with major amputation. There are cases where limb salvage options not initially identified become apparent with additional expertise or imaging. Even when the conclusion is the same, having multiple experienced clinicians agree provides important context for your decision-making. After exhausting conventional options, it is also appropriate to ask about investigational research programs.

5. What is angiogenesis, and why does it matter for my condition?

Angiogenesis is the biological process by which new blood vessels form and grow. It is your body’s natural response to areas of poor blood supply: cells in oxygen-deprived tissue release chemical signals that stimulate nearby vessels to sprout new branches. In patients with advanced PAD, this repair response is impaired — fewer angiogenic cells are mobilized, and the ischemic tissue responds less effectively. Investigational cell therapies like ACP-01 are designed to amplify this process by delivering a concentrated dose of the patient’s own angiogenic cells directly to the affected tissue, with the goal of stimulating new capillary formation and improving microvascular perfusion.

6. Is ACP-01 a proven treatment? Is it approved?

No. ACP-01 is an investigational therapy. It is not approved by Health Canada, the FDA, or any other regulatory authority for general clinical use. It is available through specific regulated access pathways — in Florida under Senate Bill 1768, in Toronto through compassionate access, and internationally in the Bahamas and Dominican Republic. All patients undergo individual evaluation before any treatment discussion. The published Phase II clinical data is encouraging, but it is early-stage evidence, not the standard required for regulatory approval.

7. Will my insurance cover this? What does it cost?

In most cases, standard health insurance plans do not cover therapies that have not received regulatory approval. Coverage varies by jurisdiction, insurer, and individual policy — and it is worth contacting your insurer directly to ask specifically about investigational therapy coverage. Patients who choose to pursue investigational options through regulated access programs typically do so on a private basis after exhausting covered treatments. The Hemostemix clinical team provides transparent, upfront information about all associated costs during the evaluation process. There is no cost for the initial consultation.

About This Article

This educational resource reflects the scientific perspective of Dr. York N. Hsiang, MB ChB, MHSc, FRCSC — Professor Emeritus of Surgery, University of British Columbia, and former Head of Vascular Surgery at Vancouver General Hospital. Dr. Hsiang is the Principal Investigator for the Phase II clinical trial of ACP-01 in no-option Critical Limb-Threatening Ischemia.

Clinical data referenced: Henderson et al. (2024), Phase II sub-analysis, Vancouver General Hospital. For full citations and scientific publications, visit hemostemix.com/scientific-publications.