Improving Care of Mycotic Aneurysms: Can We Identify the Ideal Endovascular Candidate?

Infective native aortic aneurysms (INAA) are a relatively rare but challenging pathology, with debated management strategies. Evidence is scarce, especially when considering the mid to long term prognosis, making research like that presented by Jutidamrongphan et al. especially relevant.1Jutidamrongphan W. Kritpracha B. Sörelius K. Chichareon P. Chongsuvivatwong V. Sungsiri J. et al.Predicting infection-related complications after endovascular repair of infective native aortic aneurysms.Eur J Vasc Endovasc Surg. 2023; 65: 425-432Abstract Full Text Full Text PDF Scopus (1) Google Scholar These authors report on the outcomes of treatment of INAA using standard endovascular devices. The objective was to predict the risk of infection related complications based on pre-operative clinical, laboratory, and imaging findings. Being a single arm and single centre retrospective series, it has inherent limitations, but it comprises a relatively large cohort of 98 patients treated over 16 years. Much has been said about the terminology used for infective (or infected) aortic aneurysms, with most of the literature using the term “mycotic”, as proposed by Osler in 1885. This term originated from the fungal aspect of endocarditis associated with aortic infections, but it has also been interpreted as describing the mushroom like radiological appearance that is often observed. This terminology can cause some confusion, as most infections are not fungal in origin. However, it remains an umbrella definition for a multitude of mechanisms and agents (bacteria, fungi, and even viruses), with variable presentations, virulence, and consequences. A recent meta-analysis of the management of INAA demonstrated that early outcomes are, unsurprisingly, improved with endovascular strategies when compared with open surgery. More importantly, it also showed no significant differences in the mid to long term, which was more unexpected.2Sörelius K. Wanhainen A. Mani K. Infective native aortic aneurysms: call for consensus on definition, terminology, diagnostic criteria, and reporting standards.Eur J Vasc Endovasc Surg. 2020; 59: 333-334Abstract Full Text Full Text PDF PubMed Scopus (24) Google Scholar However, it must be recognised that all studies included in this synthesis were retrospective in nature and important biases are likely. The findings of this important study led to a recommendation in the 2019 European Society for Vascular Surgery’s (ESVS) abdominal aortic aneurysm guidelines, which states that the management of INAA should be individualised and that endovascular management is an acceptable alternative (Class IIa, Level C).3Wanhainen A. Verzini F. Van Herzeele I. Allaire E. Bown M. Cohnert T. et al.Editor’s Choice – European Society for Vascular Surgery (ESVS) 2019 Clinical Practice Guidelines on the Management of Abdominal Aorto-iliac Artery Aneurysms.Eur J Vasc Endovasc Surg. 2019; 57: 8-352Abstract Full Text Full Text PDF PubMed Scopus (1421) Google Scholar The study by Jutidamrongphan et al. adds strength and discrimination to this recommendation by improving patient selection using a risk score, but it shares the same limitations of prior research. Some specifics of this study are worth mentioning. An accurate diagnosis is critical for the effectiveness of the subsequent risk score. However, in many cases the diagnosis was based on clinical assumption, with a low rate of positive cultures and no functional or molecular imaging. Although it is well recognised that a proportion of patients with vascular infections never have positive blood cultures, a diagnosis by assumption creates uncertainty over the real aetiology. Similarly, it may also be that the aneurysm is a sequela of a subdued infection, in which case the outcome of endovascular treatment would be expected to be similar to that of its degenerative counterpart. When deciding which treatment option is preferable for an individual patient, it is logical to differentiate an active arterial infection from an aneurysm of infectious origin but where microorganisms are no longer present or active. This is a critical aspect, because implanting a graft (endovascular or open) in tissue that is no longer actively infected seems like a reasonable and durable option. Conversely, an implant in an actively infected tissue will probably result in subsequent graft infection, with dramatically different implications. This nuance is implicit in the identified risk factors of positive blood cultures and psoas muscle involvement. While the criteria proposed by Sörelius et al. for the diagnosis of mycotic aneurysms are followed, advised, and probably sufficient for clinical use,3Wanhainen A. Verzini F. Van Herzeele I. Allaire E. Bown M. Cohnert T. et al.Editor’s Choice – European Society for Vascular Surgery (ESVS) 2019 Clinical Practice Guidelines on the Management of Abdominal Aorto-iliac Artery Aneurysms.Eur J Vasc Endovasc Surg. 2019; 57: 8-352Abstract Full Text Full Text PDF PubMed Scopus (1421) Google Scholar unequivocal demonstration of infection (through molecular imaging such as positron emission tomography or white blood cell scintigraphy) could result in a more robust risk score. A second aspect for consideration is that the interpretation that endovascular repair of INAA should, based on this research, be performed primarily by endovascular repair is unjustified. The literature, including the present study, and recommendations like the aforementioned ESVS clinical practice guidelines are not effusively supportive of an endovascular first approach: it is considered an acceptable alternative, requiring tailoring to the individual. The good candidate is probably the patient at high risk for open repair and at low risk of late infectious complications. Another aspect worth mentioning is the large discrepancy (up to 10 times greater) in the incidence of INAA in Asia vs. Europe and North America. This may also translate into differences in outcomes when using one treatment strategy or another, which is an issue that must be explored further. Lastly, why female sex and renal insufficiency, specifically, appear to be prognostic factors remains unexplained. In conclusion, Jutidamrongphan et al. present important research on INAAs, and the resulting risk stratification is encouraging, and will hopefully lead to replication efforts, including systematic functional or molecular imaging. By identifying risk factors for infectious complications, this work may already improve individualised decision making for this complex group of patients. However, it should not be interpreted as proof for the preferential use of endovascular devices in infected aortas. F.B.G. has received proctoring and speaker fees from Medtronic, Cook Medical, and WL Gore. None.