Due to an absence of standardised protocols, major amputation is being over utilised worldwide as a treatment for critical limb ischaemia, according to Mary Yost, president and senior analyst at The Sage Group LLC, who gave a presentation at the 2016 New Cardiovascular Horizons annual meeting (1–3 June, New Orleans, USA).
“The epidemiology of critical limb ischaemia is sparse, and there are no published worldwide estimates of the condition,” Yost told delegates. Estimates can be made by analysing global peripheral arterial disease prevalence, which increased by 24% to 202 million patients from 2000–2010, driven, Yost said, by the ageing global population (Fowkes et al, The Lancet). Importantly, this growth is more than twice as high in low and middle income countries compared with high income countries. Using these figures and assuming that critical limb ischaemia accounts for 11–15% of peripheral arterial disease cases (Nehler et al, J Vasc Surg and Yost, CLI Vol I) Yost estimates that 22–30 million people worldwide suffer from critical limb ischaemia, representing 31–42 million limbs at risk.
Commenting on the magnitude of these numbers Yost explained, “The only other critical limb ischaemia numbers that we have for comparison are those calculated by The Sage Group LLC for North America, South America, Mexico, India and Western Europe, totalling 11 million individuals in 2010. Since the population of these regions and countries represents 37% of the world population, this suggests that the 22–30 million range is reasonable and prevalence might be even be near the higher end.”
“Seventy per cent of all critical limb ischaemia is in low and middle income countries, which might seem surprising,” Yost said. Explaining why, aside from the fact that low-middle income countries have higher populations, she continued, “The age-specific prevalence of peripheral arterial disease is similar in the high and low-middle income countries and is similar in men and women. However, and this is key, peripheral arterial disease was significantly higher in women under the age of 60 years in low-middle income countries. Finally, and very importantly, there is a high and rapidly growing prevalence of diabetes in low-middle income countries.” The significance of the growing prevalence of diabetes is underscored by the fact that it increases relative risk of for critical limb ischaemia by six to seven times, and for peripheral arterial disease by two to four times—“a very strong risk factor,” Yost said.
Yost explained how the unique characteristics of diabetes in low-middle income countries can pre-dispose these populations to critical limb ischaemia. “In Mexico, for example (with a diabetes prevalence of 12.6%), only 5% of hyperglycaemia is adequately controlled and there is a very high prevalence of early onset diabetes (22% is in patients younger than 40 years). This results in longer exposure to hyperglycaemia, increasing the probability of developing chronic complications and adverse consequences such as amputation.”
A 2015 German study (Reinecke et al, European Heart Journal) found that critical limb ischaemia amputation and mortality rates remain high and relatively unchanged from those reported in TASC II in 2007—16% and 35% one-year mortality and 5% and 57% one-year amputation rates for Rutherford categories 4 and 6, respectively.
The number of major adverse cardiac events and major adverse leg events can be reduced using optimal medical management. However, citing US and British data, Yost suggested that “critical limb ischaemia patients are undertreated for their risk factors, even in comparison to intermittent claudication patients. Statins, antiplatelets and anti-hypertensives are all under utilised, glucose is inadequately controlled in 40% of cases and smoking persists in 27–52% of cases.” Such suboptimal medical management increases the risk of amputation and/or death by up to eight times.
Major amputation is “frequently” the first and only therapy used for critical limb ischaemia. “This seems to be a worldwide phenomenon,” Yost said, “with no angiogram performed in 51–73% of US patients and 37% of German patients who underwent amputation, and no revascularisation in 60–71% of US and 37% of German amputation patients.”
According to Yost, “The probability of amputation depends on who you are and where you live—the amputation lottery.” This lottery is not confined to the USA, but can be found in many other advanced economies including Germany, the UK, Netherlands and Canada. Amputation rates vary significantly by race, sex, age, socioeconomic status, hospital volume and geographic location. “This reflects variations in clinical decision-making and a lack of multidisciplinary teams,” Yost explained. Standardised protocols and further research on epidemiology, costs and consequences are important in addressing this, she concluded.