Determination of biomechanical, anatomical and patophysiological factors influencing wall strength of the abdominal aortic aneurysm and their role in the abdominal aortic aneurysm rupture risk assessment

Uvod. Aneurizma abdominalne aorte je potencijalno fatalno oboljenje koje se preventivno može lečiti hirurški. Rizik od hirurškog lečenja je sve manji međutim ma koliko bile retke komplikacije mogu biti fatalne ili prouzrokovati težak invaliditet. Upravo zato je od velikog značaja poznavanje rizika od rutpure aeurizme koji se trenutno procenjuje samo na osnovu najvećeg prečnika aneurizme što se pokazuje kao nedovoljno precizno. Ispitivanje uticaja drugih parametara (biomehaničkih, anatomskih, patomorfoloških) na nastanak rupture bi moglo da napredi procenu rizika od ove fatalne komplikacije. Metod. Ispitivanje je sprovedeno po tipu prospektivne studije koja je obuhvatila 288 bolesnika sa aneurizmom abdominalne aorte koji su ispitivani ili operisani na Klinici za vaskularnu i endovaskularnu hirurgiju KCS u periodu od januara 2012 do decembra 2015 godine. Na osnovu podataka dobijenih multislajsnom kompjuterizovanom tomografijom kod bolesnika su ispitivani biomehanički parametri koji deluju na zid aneurizme (napon, prečnik ekvivalentan riziku od rupture) kao i morfoloki parametri koji bi mogli da ukažu na patofiziološke procese u aneurizmatskoj kesi (zapreminu aneurizme, intraluminalnog tromba, angulacije). Uzorci prednjeg zida aneurizmatske kese ispitivani su testom inflacije i na taj način im je određivana snaga i elastičnost dok je iz uzorka seruma odreživana aktivnost matriksne metaloproteinaze 9. Rezultati. Značajno više osoba ženskog pola je bilo u grupi bolesnika sa simptomatskom odnosno rupturiranom aneurizmom abdominalne aorte, 5/23 (21.73%) prema 12/75 (16%), p=0.005. Multivarijantni model kojim su uključeni pol, životna dob, maksimalni prečnik aneurizme (MAD,OR=1.063), relativna zapremina intraluminalnog tromba (rILT, OR=1.039) i ukupna zapremina aneurizme (UZA,OR=1.006) su značajni prediktori rupture aneurizme abdominalne aorte sa najvećim naponom u zidu (PWS,OR=1.010) dijametra ekvivalentan riziku od rupture (RRED,OR=1.031). Merene su vrednosti AUC i cc za iste parametre u modelu koji kombinuje MAD, TZA i rILT: MAD (0.790, cc=75%), PWS (0.713, cc=73%), RRED (0.717, cc=55%), TAV (0.756, cc=79%), rILT (0.656, cc=60%) i MAD+TAV+rILT (0.797, cc=82%). Nije dobijena statistički značajna razlika između vrednosti serumske MMP 9 i snage zida, test korelacije je iznosio 0.174, p=0.135. Konstatovana je statistički značajna povezanost između serumske koncentracije MMP 9 i srednjeg napona u intraluminalnom trombu (cc - 0.371, p=0.016), najvećeg rizika od rupture (p=0.04) i volumena intraluminalnog tromba (cc 0.324, p=0.03). Zaključak. Imajući u vidu zadate ciljeve kao i prikazane rezultate može se zaključiti da je zid aneurizme abdominalne aorte slabije snage kod aneurizmi koje su već rupturirale ili izazivale simptome čime je pokazano da snaga zida ima važnu ulogu u procesu nastanka rupture. Na snagu aneurizmatskog zida je uticala jedino relativna debljina intraluminalnog tromba. Serumska koncetracija MMP – 9 se, prema rezultatima ovog istraživanja, ne može koristiti za procenu snage aneurizmatskog tkiva prilikom predviđanja rizika od rupture aneurizme abdominalne aorte. Biomehanički, anatomski odnosno morfološki parametri mogu začajno unaprediti predviđanje rizika od rupture u odnosu na korišćenje samog dijametra. Najkorisniji su najveći napon, zapremina aneurizme, relativna zapremina intraluminalnog tromba i dijametar ekvivalentan riziku od rupture. Korišćenjem ovih parametara moć predviđanja nastanka rupture se povećava sa 73% na 83.9%.Introduction. Abdominal aortic aneurysm is potentialy fatal disease that can be treated with preventive operation. Surgical risk, although improving, can lead to death or disability. In this regard it is of high importance to assess risk of rupture that is nowdays expressed in correlation to aneurysm diameter what was shown to be less accurate. Assessment of correlation between other parameters (biomechanical, anatomical, patomorphological) and risk of aneurysm rupture might improve rupture risk assesment and facilitate decision making. Methods. This research was conducted in prospective manner at the Clinic for Vascular and Endovascular surgery and included 288 patients with abdominal aortic aneurysm in the period from January 2012 to December 2015. Images from multisliced computed tomography were used for biomechanical analysys to estimate peak wall stress and rupture risk equvivalent diameter by finite element analysys. Morphological parameters as aneurysm and intraluminal thrombus volume, angulations and anatomical parmeters were assessed from these images as well. Samples of anterior wall of aneurysm were tested with inflation test estimating tissue elasticity and strength while serum level of matrix metalloproteinase 9 were measured as well. Results. There were significantly more females in the R group: 5/23 (21.73%) comparing to 12/75 (16%) in 4A group, p=0.005. In a multivariable model, including gender and age as confounder variables, maximal aneurysm diameter (MAD,OR= 1.063), relative intraluminal thrombus (rILT,OR=1.039) and total aneurysm (TAV,OR=1.006) volume continued to be a significant predictors of AAA rupture with peak wall stress (PWS,OR=1.010) and rupture risk equivalent diameter (RRED,OR=1.031). AUC values and correct classification (cc) for the same parameters and model that combines MAD, TAV and rILT were measured: MAD (0.790, cc=75%), PWS (0.713, cc=73%), RRED (0.717, cc=55%), TAV (0.756, cc=79%), rILT (0.656, cc=60%) and MAD+TAV+rILT (0.797, cc=82%) Conclusion. Based on aim and presented results aneurysm wall is weaker in ruptured and symptomatic aneurysm outlining importance of wall strength in rupture developement. Wall strength correlated with relative thrombus thickness. Serum level of MMP-9, based on these restults, can not be used for tissue strength assessment however thrombus formation can be suspected in elevated levels of MMP 9. Biomechanical, anatomical and moprhological paramters can improve rupture prediction in comparison to maximal diameter only. The most usefull paramters are peak wall stress, aneurysm volume, relative intraluminal thrombus and rupture risk equivalent diameter. Using these paramters rupture prediction is increased from 73% to 83.9%

Front Lines of Thoracic Surgery

Front Lines of Thoracic Surgery collects up-to-date contributions on some of the most debated topics in today's clinical practice of cardiac, aortic, and general thoracic surgery,and anesthesia as viewed by authors personally involved in their evolution. The strong and genuine enthusiasm of the authors was clearly perceptible in all their contributions and I'm sure that will further stimulate the reader to understand their messages. Moreover, the strict adhesion of the authors' original observations and findings to the evidence base proves that facts are the best guarantee of scientific value. This is not a standard textbook where the whole discipline is organically presented, but authors' contributions are simply listed in their pertaining subclasses of Thoracic Surgery. I'm sure that this original and very promising editorial format which has and free availability at its core further increases this book's value and it will be of interest to healthcare professionals and scientists dedicated to this field