**4.4. Current CLI diagnostic: can we effectively assess the real ischemic burden?**

A series of high-performance technologies conceived to assess tissue-related arterial disease were introduced in the last two decades. These methods afford high or low invasiveness and focus on different targets in evaluating CLI hemodynamic and tissue changes [29, 30]. With each passing year, novel or modernized diagnostic techniques strive for accurately scoring the degree of perfusion tissue impairment in mixed series of patients and arterial pathologies [1, 2, 27–32].

It has been showed that first *detailed clinical assessment* of each tissue defect is mandatory in all presentations [36, 38, 39, 40]. Basic characteristics of each ulcer (surface and depth), its precise location(s), and the appended inflammatory extensions before and after revascularization should be carefully analyzed and scored by trained clinical teams [38, 39].

The majority of available diagnostic techniques can be roughly divided into *macro-* and *microcirculatory* investigation tools. Some "routine" *noninvasive macro-vascular exams* such as the ankle-brachial index (ABI < 0.5, severe ischemia), the toe-brachial index (TBI < 0.7, presence of PAD), the ankle and toe pressure (<40 mm Hg, threat of the limb), the exercise stress testing, and the Doppler and Duplex assessments are well-documented and own undeniable benefits, and drawbacks [33–35, 37, 39]. Meticulous Doppler evaluation avails real usefulness for knowledgeable clinicians in determining antegrade versus retrograde tibial, pedal, or collateral flow toward the wound zone [24, 39]. It may also yield helpful information over the remnant "large caliber" collaterals in the targeted foot ischemic area [24, 35, 39]. A precise mapping of lower limb arteries specifying eventual stenosis, occlusions, and secondary collateral flow represents a valuable *preoperative* or *follow-up* guide for any interventionist in planning wound-directed revascularization [39].

Other low-invasiveness techniques for detecting "large" arteries and collaterals include lastgeneration multislice computed tomographic angiography (CTA with "Dual energy") and the magnetic resonance angiography (MRA adding "BOLD sequences") [33, 39]. The "Dual energy" CTA imaging represents a current evaluation method in our team experience for patients with normal renal function. This technology allows accurate calcific plaques removal in tibial and foot vessels and provides a true BTK "lumenograms" in these patients [39].

Despite notable progress in both techniques, these two methods host similar iodine or gadolinium-based contrast disadvantages, being contraindicated in allergic patients or for those suffering from chronic renal insufficiency [33, 39].

Unfortunately, in the daily clinical practice, most of diabetic or renal CLI patients with threatening foot ulcers often associate advanced nephropathy that challenges the use of Iodine or Gadolinium contrast agents.

Probably the most accustomed *macro-circulatory* yet *invasive* available test is represented by the digital subtraction arteriography (DSA) of the inferior limb arteries [1, 3, 28, 38].

DSA is currently recognized as a "key exam" in accurate ischemic flow assessment and classification [1–3, 38, 39]. It is cited to afford best available spatial resolution required to establish main arterial trunks and collaterals (>500 µm diameter) morphological details toward the wound zone [1, 3, 27, 35, 38]. DSA also enables appropriate diagnostic for eventual anatomical variables and their collateral network in each specific arterial pattern [1, 27, 35]. This *quantitative* information becomes essential in understanding individual vascular anatomy for performing eventual *direct* (wound targeted) or *indirect* (collateral supported) arterial revascularization to the wound zone [24–26, 39]. Peripheral angiography consequently helps in determining the most appropriate and "feasible" target vessel to be treated [23–26, 35].

It is shown that DSA affords the interventionist valuable *qualitative* information about *the severity* of distal leg ischemia (the "desert" foot presentation). It also provides accurate characteristics of run-off vessels, the integrity of foot arches, and clues about potential technical difficulties in long chronic total occlusions (CTO) recanalization (the presence of concave/ convex atherosclerotic caps) [1, 21, 29, 39]. This technology provides corresponding information about extensive calcifications, tortuosities, and available arterial-arterial communicants or "blush" irrigation around the ulcer's zone [25, 26, 31, 35, 39]. Inasmuch DSA bears evoked drawbacks due to iodine contrast (allergic or renal failure reactions), it also carries the eventual access-related risk for hemorrhagic complications (0.8–3% of cases) [27, 33, 39].

Modern wound practitioners equally avail latest *micro-vascular noninvasive* diagnostic technology, with soaring applications in the last two decades. Among these methods, some showed promising results such as the consecrated transcutaneous oxygen pressure [1–3, 33, 39]; the novel vascular optical tomographic imaging (VOTI) [41]; the "real-time" Laser-Doppler skin perfusion pressure [33, 35, 39]; the continuous tissue oxygen saturation foot-mapping (StO2); and the recent 99mTc Scintigraphic, the PET, and the single-photon emission computed tomography (SPECT) scans (owning specific CLI 3-D detection at molecular level) [35, 39]. Parallel *microcirculatory* yet, more *invasive* exploration was recently documented gathering intraoperative "Indocyanine green" angiography (ICGA) [42, 43], the "Indigo Carmine" angiography [44], and the foot "micro-oxygen sensors" (MOXYs) technology, all with encouraging applications during wound-targeted revascularization [45].

### **4.5. The CLI multimodal approach: a novel contemporary concern**

It has been showed that first *detailed clinical assessment* of each tissue defect is mandatory in all presentations [36, 38, 39, 40]. Basic characteristics of each ulcer (surface and depth), its precise location(s), and the appended inflammatory extensions before and after revascularization

The majority of available diagnostic techniques can be roughly divided into *macro-* and *microcirculatory* investigation tools. Some "routine" *noninvasive macro-vascular exams* such as the ankle-brachial index (ABI < 0.5, severe ischemia), the toe-brachial index (TBI < 0.7, presence of PAD), the ankle and toe pressure (<40 mm Hg, threat of the limb), the exercise stress testing, and the Doppler and Duplex assessments are well-documented and own undeniable benefits, and drawbacks [33–35, 37, 39]. Meticulous Doppler evaluation avails real usefulness for knowledgeable clinicians in determining antegrade versus retrograde tibial, pedal, or collateral flow toward the wound zone [24, 39]. It may also yield helpful information over the remnant "large caliber" collaterals in the targeted foot ischemic area [24, 35, 39]. A precise mapping of lower limb arteries specifying eventual stenosis, occlusions, and secondary collateral flow represents a valuable *preoperative* or *follow-up* guide for any interventionist in

Other low-invasiveness techniques for detecting "large" arteries and collaterals include lastgeneration multislice computed tomographic angiography (CTA with "Dual energy") and the magnetic resonance angiography (MRA adding "BOLD sequences") [33, 39]. The "Dual energy" CTA imaging represents a current evaluation method in our team experience for patients with normal renal function. This technology allows accurate calcific plaques removal in tibial and foot vessels and provides a true BTK "lumenograms" in these patients [39].

Despite notable progress in both techniques, these two methods host similar iodine or gadolinium-based contrast disadvantages, being contraindicated in allergic patients or for

Unfortunately, in the daily clinical practice, most of diabetic or renal CLI patients with threatening foot ulcers often associate advanced nephropathy that challenges the use of Iodine

Probably the most accustomed *macro-circulatory* yet *invasive* available test is represented by the

DSA is currently recognized as a "key exam" in accurate ischemic flow assessment and classification [1–3, 38, 39]. It is cited to afford best available spatial resolution required to establish main arterial trunks and collaterals (>500 µm diameter) morphological details toward the wound zone [1, 3, 27, 35, 38]. DSA also enables appropriate diagnostic for eventual anatomical variables and their collateral network in each specific arterial pattern [1, 27, 35]. This *quantitative* information becomes essential in understanding individual vascular anatomy for performing eventual *direct* (wound targeted) or *indirect* (collateral supported) arterial revascularization to the wound zone [24–26, 39]. Peripheral angiography consequently helps in determining the most appropriate and "feasible" target vessel to be treated [23–26, 35]. It is shown that DSA affords the interventionist valuable *qualitative* information about *the severity* of distal leg ischemia (the "desert" foot presentation). It also provides accurate

digital subtraction arteriography (DSA) of the inferior limb arteries [1, 3, 28, 38].

should be carefully analyzed and scored by trained clinical teams [38, 39].

planning wound-directed revascularization [39].

254 Wound Healing - New insights into Ancient Challenges

those suffering from chronic renal insufficiency [33, 39].

or Gadolinium contrast agents.

Bell et al. first proposed the notion of critical limb ischemia in 1982 for defining severe arterial flow deprivation that currently inflicts major limb amputation threat [46]. In their original publication, the authors characterize CLI essentially on *macro-vascular hemodynamic criteria*, such as the measured AP <40 mm Hg in the presence of rest pain and <60 mm Hg when tissue necrosis is noted [46]. It should be mentioned that in the original form of this concept, the diabetic group of CLI patients was deliberately excluded since neuropathy and infection are often associated and make more complex real ischemic stratification [46]. During the next 30 years, the term of CLI was broadly, yet most of the times inappropriately, used [29–32, 47] as to characterize a much larger hierarchy of severe arterial presentations, including diabetic and renal subjects [27, 30, 46–49]. Although the particular threshold from "reversible" to "irrecoverable" limb ischemia still dwells imprecise [27, 29, 31, 34], it is accepted that CLI often implies a poor limb outcome without prompt revascularization [1–3, 27, 30, 46, 47]. An eloquent 1527 CLI subjects review analysis recently performed by Abu Dabrh et al. on the natural history of untreated "severe" or "critical" ischemic limbs revealed 22% all-cause mortality, 22% major amputation, and 35% worsening in wound evolution rates at 1 year [48]. The almost similar observation was reported in 2016 by Vallabhaneni et al. in a 443 CLI cohort assembling more than 60% diabetics and 20% dialyzed patients [49]. They found 32 and 56% mortality rate at 1 and 3 years, respectively, and 24 and 31% major amputation rates at the same time intervals [49]. The authors conclude that not all patients were encompassing current ABI- and TBIaccepted CLI *macro-vascular* criteria, obviously are at high risk for major amputation [49].

We know nowadays that CLI associates a modest quality of life to the high rate of major amputations and that about 60% of mortality is documented between 3 and 5 years following the initial diagnostic [1–3, 32, 46, 47–49].

Parallel papers focusing on equivalent *macro-vascular* hemodynamic standards (ABI, TBI, AP, TP, etc.), equally fail to explain this huge heterogeneity encountered in CLI "limb salvage" and dedicated treatments [47–49]. Struggling to provide more accurate CLI categorization, several conspicuous classifications systems were proposed in the last two decades [1, 3, 30, 47].

Owning the Bollinger angiographic scale [50], the Trans-Atlantic Inter-Society initial Consensus (TASC I and II) [3, 51], the Rutherford staging of PAD [52], and the European recommendations for CLI management [53], complementary definitions yet adding only TcPO2 *microcirculatory* references were settled [27, 47, 53].

In the recent years, novel PAD classification systems were developed alike the Graziani morphologic arteriographic indexation in diabetics [54], the Toursarkissian angiographic scoring for distal limb salvage bypass [55], and the "Jenali" tibial run-off classification system, with appended below-the-knee intervention protocol [56]. This latest is based on three grades for main infragenicular arterial trunks fluency associating three levels of time-related collaterally filling (at 3–6–9 s) [56].

Undoubtedly, all abovementioned iconographic scoring systems excel in meticulous angiographic anatomy analysis, yet only partially address concomitant wound index or baseline *microcirculatory* perfusion status [30, 39].

Despite real efforts in stratifying CLI intimate mechanisms, to date, all evoked classifications add a little emphasis on coupled *macro-* and *microcirculatory* evaluation, including individual wound characteristics [30, 39].

They also fail to quantify eventual threshold [47] below which inferior limb perfusion becomes nonviable without opportune revascularization [27–30, 47]. The risk of developing CLI and ischemic wounds seems considerably increased in diabetic patients, although prone to more frequently endure systemic ischemic events compared to general population [3, 27, 31].

Contemporary clinical expertise allows better knowledge over the multifaceted "Diabetic Foot Syndrome" (DFS) presentation that gathers arteriopathy, neuropathy, sepsis, pressure injuries, and cellular and molecular metabolic disturbances, in myriads of different clinical archetypes [31, 57]. A vehement need for more specific CLI delineation in these patients was increasingly recollected in modern vascular literature.

### **4.6. Does healing process in diabetics follow same predictable "standards" alike other CLI patients?**

Soaring progress in arterial ulcers treatment is however confronted with an exponentially increasing number of diabetic CLI subjects each year [1, 31]. To date, the prevalence of purely neuropathic, ischemic, and combined neuro-ischemic foot ulcers in patients with diabetes was estimated at 35, 15, and 50% rates, respectively [57–59].

Reported DFS singularities include (1) the regular tibial trunks *calcifications* [2, 30, 31, 57] that match the extent of local neuropathy [25, 31], (2) the "end-artery occlusive disease" (EAOD) concept [59], (3) an impaired *arterio-* and *angiogenesis* [60], (4) a specific *collateral deprivation* following chronic inflammation and septic thrombosis of small vessels [31, 35, 57–59], (5) intrinsic vascular or *matrix impaired regeneration* [61], and (6) characteristic neuro-ischemic *compartmental hyper pressure* foot syndromes [62].

We know nowadays that CLI associates a modest quality of life to the high rate of major amputations and that about 60% of mortality is documented between 3 and 5 years following

Parallel papers focusing on equivalent *macro-vascular* hemodynamic standards (ABI, TBI, AP, TP, etc.), equally fail to explain this huge heterogeneity encountered in CLI "limb salvage" and dedicated treatments [47–49]. Struggling to provide more accurate CLI categorization, several conspicuous classifications systems were proposed in the last two decades [1, 3, 30, 47].

Owning the Bollinger angiographic scale [50], the Trans-Atlantic Inter-Society initial Consensus (TASC I and II) [3, 51], the Rutherford staging of PAD [52], and the European recommendations for CLI management [53], complementary definitions yet adding only TcPO2

In the recent years, novel PAD classification systems were developed alike the Graziani morphologic arteriographic indexation in diabetics [54], the Toursarkissian angiographic scoring for distal limb salvage bypass [55], and the "Jenali" tibial run-off classification system, with appended below-the-knee intervention protocol [56]. This latest is based on three grades for main infragenicular arterial trunks fluency associating three levels of time-related collat-

Undoubtedly, all abovementioned iconographic scoring systems excel in meticulous angiographic anatomy analysis, yet only partially address concomitant wound index or baseline

Despite real efforts in stratifying CLI intimate mechanisms, to date, all evoked classifications add a little emphasis on coupled *macro-* and *microcirculatory* evaluation, including individual

They also fail to quantify eventual threshold [47] below which inferior limb perfusion becomes nonviable without opportune revascularization [27–30, 47]. The risk of developing CLI and ischemic wounds seems considerably increased in diabetic patients, although prone to more frequently endure systemic ischemic events compared to general population [3, 27, 31].

Contemporary clinical expertise allows better knowledge over the multifaceted "Diabetic Foot Syndrome" (DFS) presentation that gathers arteriopathy, neuropathy, sepsis, pressure injuries, and cellular and molecular metabolic disturbances, in myriads of different clinical archetypes [31, 57]. A vehement need for more specific CLI delineation in these patients was increasingly

**4.6. Does healing process in diabetics follow same predictable "standards" alike other CLI**

Soaring progress in arterial ulcers treatment is however confronted with an exponentially increasing number of diabetic CLI subjects each year [1, 31]. To date, the prevalence of purely neuropathic, ischemic, and combined neuro-ischemic foot ulcers in patients with diabetes was

the initial diagnostic [1–3, 32, 46, 47–49].

256 Wound Healing - New insights into Ancient Challenges

*microcirculatory* references were settled [27, 47, 53].

erally filling (at 3–6–9 s) [56].

wound characteristics [30, 39].

*microcirculatory* perfusion status [30, 39].

recollected in modern vascular literature.

estimated at 35, 15, and 50% rates, respectively [57–59].

**patients?**

The EAOD theory emphasizes that in the collateral-depleted diabetic limb, "each millimeter of skin" up to the "entire foot" may rely upon one particular artery with *terminal* distribution [59], while this valuable vessel may be auspiciously targeted by "wound directed" revascularization, according to the angiosome concept [24–26].

Modern diabetic ulcer understanding builds a complete design of multifaceted and potentially devastating CLI effects in these patients [2, 31, 57–62].

Enthralling scientific works in the last decade evoke a possible central mechanism playing a pivotal role in different DFS pathological changes [59, 63]. Thus, chronic hyperglycemia may enhance at the mitochondrial-level expanded free radicals production, altering normal metabolic and cellular activity [63]. This malfunction affects more particularly normal regeneration at the *microcirculatory* level (vasa-vasorum and vasa-nervorum) also the tissue binding matrix [58, 59–61].

Arteriopathy and neuropathy, albeit regular DFS features (in different proportions) [58, 59], may probably share the same pathological emergence in the vast diabetic complications puzzle [57–59, 63].

Trying to stratify main DFS characteristics, a few classification systems were proposed. It should be mentioned the "Wagner" stratification [64], the PEDIS (perfusion, extent/size, depth/ tissue loss, infection, sensation/neuropathy) [65], the University of Texas (UT) [66], the sepsis, arteriopathy, denervation (SAD) scale [67], the diabetic ulcer severity score (DUSS) [68], the multiple ulceration, wound area, pedal pulse, and ulcer duration (MAID) classification [69], and the "St. Elian wound score system" [70], rejoicing unanimously recognized popularity and documented clinical benefits [57–59].

However, most of these classifications fail to provide concomitant *perfusion* information [35, 47]; individual *ulcer features* [47]; *infection, denervation*, or *gangrene* specifications [47]; systemic factors report [2, 30] (Section 4.5); and healing prognosis [2, 40, 47]. All these clinical entities seem to bear a huge interest in healing evaluation [2, 31, 37, 39].

In same effort to fully perceive each DFS presentation, the remarkable WIfI classification [47] recently brought together Wound grades, Ischemia levels, and foot Infection ranked in a unitary view, as important variables for appended wound prognosis [47]. However, diabetic neuropathy [36, 58, 71] and concurrent systemic variables influencing tissue recovery [57, 61, 72] are not included in this model of examination. In a parallel analysis, owing a consecutive 249 CLI wounds series, Azuma et al. [72] found that beyond diabetes (including neuropathy and infection), equally end-stage renal disease (ESRD), Rutherford category 6 (including or not the heel), and low albumin levels, represented significant factors in the complex tissue recovery cascade beyond prompt revascularization [72].
