The application of new global vascular guidelines for chronic limb-threatening ischemia (CLTI) provides an opportune and worthwhile window to revisit the concept of critical limb ischemia (CLI) along with its implications as a worldwide healthcare issue.
Peripheral arterial disease (PAD) leading to CLI is a growing problem around the world. More than nine million Americans have PAD, including 30% aged 70 and over, with many patients believing that significant leg pain is just a part of getting old. CLI itself is also on the rise worldwide, particularly in light of the explosion in diabetes. It is estimated that by the year 2040, more than 640 million patients across the globe will be suffering from the condition. This includes a significant increase outside of North America, particularly in the Asia-Pacific region. There are more patients worldwide with PAD than those with other well recognized disease entities, including heart failure, Alzheimer’s disease, cancer, HIV/AIDS and those related to the opioid addiction problem. This virtual epidemic will increase the cost of the disease globally to well over $600 billion. Additionally, the rate of women with PAD has now crept up on the rate among men.
In 1982, at an international vascular symposium, CLI gained attention as a condition in patients without diabetes who have chronic ischemia as a major threat to a limb. Symptoms—rest pain and tissue loss—and the physical examination (pulse exam) have always been important in the diagnosis and evaluation of CLI, but physiologic criteria were also included in the analysis. These criteria have included an ankle-brachial index of less than 0.3, an absolute systolic blood pressure less than 15mmHg at the ankle, an absolute systolic blood pressure less than 30mmHg at the toe, and a decrease in PVR (pulse volume recording) waveforms (<5mm) and PPG (photoplethysmogram) waveforms (<4mm).
In the 1980s and 1990s, the Rutherford and Fontaine classifications gained popularity. These classification systems included categories consistent with CLI. In the Rutherford system, categories 4?6—and Fontaine’s stages 3 and 4—are consistent with CLI. The Trans-Atlantic Inter-Society Consensus Document on Management of Peripheral Arterial Disease (TASC) II document from 2008 added to the classification of CLI with a focus on arterial anatomy as well as ischemic symptoms, and objectively proven PAD. This classification system was adopted by the American Heart Association and American College of Cardiology in 2016.
The Society for Vascular Surgery (SVS) has been an advocate of the Wound, Ischemia and foot Infection (WIfI) classification system, which incorporates a classification of the wound, degree of ischemia and extent of infection. Most recently, several vascular societies—including the SVS, the European Society for Vascular Surgery and the World Foundation of Vascular Surgery—have issued global vascular guidelines, renaming the disease CLTI.
The guidelines state that the term CLI is outdated and fails to encompass the full spectrum of the disease as well as moderate practice. CLTI is proposed as a broader category in order to decrease delays in therapy and avoid amputation. The authors of these guidelines feel that previous classification systems did not capture the full range of neuro-ischemic compromise involved with these patients and felt that a specific hemodynamic threshold for CLI may not be appropriate. But they did advocate for certain hemodynamic criteria based on the patient’s clinical presentation. The authors supported the use of the WIfI system proposed by the SVS.
Despite the refinement in definition and management guidelines, much work remains to be done in terms of awareness and delivery of care. The public and healthcare policy advocates do not fully understand this disease process or its implications in terms of care and cost to our healthcare system. TASC II pointed out that after one year of CLI therapy, only 25% of patients were alive with the resolution of their symptoms. Lower extremity amputation and an underappreciated mortality rate continue to impact patients with CLI. An incident diagnosis of CLI has a higher five-year mortality than most diseases with the exception of lung cancer, with a 46% survival rate at five years among Medicare beneficiaries who have no prior diagnosis of CLI. The impact of a major amputation is profound.
Meanwhile, it is also increasingly recognized that there is a disparity in the delivery of care based on angiography and socioeconomic status: availability of care for patients with CLI and amputation rates appear to correlate nationally, although this does not impart causation. There are also racial and ethnic disparities.
Therefore, there is fertile ground for progress to be made in the delivery of care for the growing number of patients with CLI/CLTI related to PAD. As vascular specialists, we must continue to raise awareness among patients, nonvascular physicians and healthcare policymakers on this important issue. As vascular specialists, we must help impact and alleviate the disparity of care delivered based on both geography and socioeconomic status. As vascular specialists, we must focus on reduction of amputation and the progress that has been made in this regard as well as prosthetic development to maintain the ambulatory status and health of our patients.
Finally, as vascular specialists, we must make use of this opportunity. We have to make certain that these patients are on appropriate adjunct medical therapy in the form of statins, antiplatelet agents and other medical regimens in order to decrease the mortality associated with this condition. Although this may seem a daunting task, much progress has been made. The future appears ripe for a major impact to be made on a significant healthcare problem.
Richard F. Neville is associate director of the Inova Heart and Vascular Institute, vice- chairman in the department of surgery and system director of vascular services. Neville also has an academic appointment as clinical professor of surgery at George Washington University.