Management of endothermal heat-induced thrombosis

Introduction

Endothermal heat-induced thrombosis (EHIT) refers to the propagation of thrombus into the deep vein contiguous with a superficial vein that has been ablated with endothermal methods ¹ including radiofrequency (RFA) and endovenous laser ablation (EVLA). Unlike deep venous thrombosis (DVT), EHIT is a unique entity that has a distinctive pathophysiology and behaves differently from a classic DVT. It is usually diagnosed using post-procedural venous duplex ultrasound within 72 h and 2 weeks of the index procedure, appearing as a hyperechogenic non-compressible lesion, sometimes associated with abnormal venous flow, and involving the saphenofemoral or saphenopopliteal junction. ¹

Due to the low incidence of this entity, risk factors for the development of EHIT are still unclear. Several proposed risk factors include personal history of venous thromboembolism, older age (>65 years old), male gender, and larger treated vein diameters, although this is based on inconsistent evidence. ¹ While EHITs are usually asymptomatic, and most regress spontaneously after a few weeks of observation or with a short course of anticoagulation, some have been associated with rare cases of pulmonary embolism. ² Due to this rare but potentially significant adverse event, which has been reported in up to 3% of cohorts,^3,4 diagnosis and management of EHIT should follow an evidence-based approach to ensure that patients receive timely and appropriate care.

Management recommendations

Despite the infrequent rates of EHIT, there may be opportunity to help prevent its occurrence. Underlying hypercoagulable states should be identified prior to intervention, and clinicians are reminded that it is safe to perform endothermal ablation whilst patients are on anticoagulation. Starting ablation >2.5 cm away from the saphenofemoral or saphenopopliteal junction may help reduce risk, although this recommendation is based on weak evidence (Grade 2C). It should also be noted that chemoprophylaxis and compression therapies post-procedurally do not help prevent development of EHIT although this is based on weak evidence as well.

Should patients develop EHIT, the first step in management is to classify the lesion according to the unified AVF-EHIT classification system, seen in Table 1 below. This classification system categorises EHIT based on the location and extent of thrombus, with extent of thrombosis increasing as class increases from I to IV.

Table 1.

AVF-EHIT classification system.

Class	Definition
IA	Thrombus propagation to the inferior epigastric vein
IB	Thrombus propagation to the saphenofemoral/saphenopopliteal junction
II	Thrombus propagation into the deep vein (<50% lumen)
III	Thrombus propagation into the deep vein (>50% lumen)
IV	Thrombus propagation leading to an occlusive deep vein thrombosis

Management should be tailored according to AVF-EHIT class and patient characteristics, with the management for EHIT being the same for both the great saphenous vein (GSV) and short saphenous vein (SSV). With class I, both subgroups require no treatment and no further surveillance ultrasound scans are required unless to evaluate for research purposes. In a small proportion of patients with class II EHIT and above, small cohort studies have suggested that EHIT can progress to higher classes,^3,5 and therefore, surveillance is required, and treatment may be indicated. In class II, patients may be stratified into low and high risk for thrombus propagation. If they are low risk, medical treatment may be withheld, and weekly ultrasound monitoring may be performed until resolution of the EHIT is documented. High risk patients may be treated with an antiplatelet, prophylactic anticoagulation or therapeutic anticoagulation. Weekly ultrasound monitoring is also indicated until documented resolution. In class III, patients may receive therapeutic anticoagulation with weekly ultrasounds to confirm resolution. Finally, treatment for patients with class IV EHITs should be individualised, with reference made to the CHEST guidelines for a provoked acute DVT Figure 1. This management is summarised in Table 2.

Figure 1.

The one-page guideline.

Table 2.

Management according to the AVF-EHIT classification system.

Class	Treatment
I	A) No treatment
	B) No treatment, but may be evaluated for research purposes
II	Low risk: No treatment, but weekly ultrasound until documented resolution
	High risk: Antiplatelet, prophylactic anticoagulation or therapeutic anticoagulation with weekly ultrasound until documented resolution
III	Therapeutic anticoagulation with weekly ultrasound until documented resolution
IV	Consideration for treatment consistent with CHEST guidelines for treatment of a provoked acute DVT

Discussion

This article provides a one-page clinical practice guideline summarising the clinical management of EHIT. It is part of a series of publications for the UIP One-Page Guidelines, which are aimed at ensuring that patients with venous disease receive timely and appropriate care based on current best evidence and expert consensus.

It must be noted that due to the rarity of this presentation, the literature available on EHIT is largely based on observational studies. In view of this, the quality of data is relatively poor but may be improved over time with prospective registries to help identify risk factors, ascertain if prevention strategies including VTE thromboprophylaxis are effective, and potentially determine if there is a need for routine duplex surveillance post-endothermal ablation. Whilst the evidence is being improved, clinicians who encounter any EHIT, incidental or otherwise, should be cognisant of the need to manage this condition with an evidence-based approach, tailoring management to the patient and EHIT characteristics.

For any healthcare providers who perform endothermal ablation or are involved in the care of patients who undergo such procedures, this article and summary document should serve as a reminder of EHIT as a potential sequela of this procedure. Clinicians and all members of the healthcare team should be aware that EHIT is not a classical DVT and as such has a different natural history and clinical course to DVTs. In EHIT, the coagulation system is usually not activated, with any extension of the thrombus above the level of ablation due to local processes. The vascular specialist should assess each patient carefully and tailor their management according to each individual case.