Evaluation of cerebral autoregulation by application of apnea test in patients with symptomatic carotid stenosis before and after carotid endarterectomy

TCD apnea test kao neinvazivna i bezbedna neuroultrasonografska metoda pruža korisne informacije o vazomotornoj reaktivnosti (VMR) u procesu indirektnog sagledavanja funkcionisanja moždane autoregulacije. Vazomotorna reaktivnosti podrazumeva sposobnost dilatacije ili konstrikcije moždanih arteriola nastale kao odgovor na određeni vazoaktivni stimulus, najčešće ugljen dioksid. Cilj ove doktorske disertacije bio je ispitivanje i analiziranje promene karotidne hemodinamike kod bolesnika sa ishemijskim moždanim udarom (IMU) ili tranzitornim ishemijskim atakom (TIA) i simptomatskom karotidnom stenozom u preoperativnom i tromesečnom postoperativnom periodu, kao i procena revaskularizacionog efekta karotidne endarterektomije (KEA).U istraživanje je uključeno 60 hospitalizovanih bolesnika koji su doživeli prvi IMU i TIA u zoni vaskularizacije arterije cerebri anterior (ACA) i arterije cerebri medije (ACM), svi sa karotidnom stenozom, ACI ≥70%. Bolesnici su bili hospitalizovani na Klinici za neurologiju, Kliničkog Centra Vojvodine, Klinici za kardiovaskularnu hirurgiju, Instituta za kardiovaskularne bolesti Vojvodine i Klinici za vaskularnu hirurgiju, u Novom Sadu. U odnosu na kliničke manifestacije bolesni i su podeljeni u tri grupe: bolesnici sa TIA i amaurosis fugax, sa parcijalnim infarktom u zoni ACA ili ACM i sa lakunarnim infarktom. Istraživanje je analiziralo uticaj promenljivih i nepromenljivih vaskularnih faktora rizika na pojavu IMU i TIA, ali i na VMR, procenjivanu kroz indeks zadržavanja daha (Breath Holding Index, BHI) ipsilateralno i kontralateralno u odnosu na karotidnu stenozu. Analizirana je povezanost stepena karotidne stenoze sa vrednostima BHI preoperativno, povezanost BHI sa težinom kliničke slike, uticaj kolateralnog krvotoka na VMR, distribucija BHI u pojedinim tipovima IMU i TIA kao i komparacija BHI u pre i u postoperativnom periodu od 30 i 90 dana. Na osnovu sprovedenog istraživanja, došlo se do zaključaka da je redukovana VMR preoperativna karakteristika karotidne stenoze ipsilateralno kao i karakteristika različitih tipova IMU i TIA ipsilateralno; postoji negativna korela ija izmeĐu stepena karotidne stenoze i BHI vrednosti. Nije potvrđena hipoteza da veći roj razvijenih kolateralnih puteva uslovljava očuvanu VMR; utvrđena je pozitivna korelacija između BHI vrednosti u preoperativnom i postoperativnom periodu; redukovana VMR ima negativan uticaj na težinu kliničke slike. Prepoznavanje vrednosti TCD apnea testa, koji se može koristiti kao komplementarna metoda drugim vazoaktivnim testovima u praćenju karotidne hemodinamike, od posebne je važnosti neurologu i vaskularnom hirurgu. Time bi se doprinelo daljoj evaluaciji mehanizma nastanka IMU, planiranju terapijskog pristupa i determinisanju prognoze operisanih bolesnika. Činjenica da većina neuroloških odeljenja poseduje TCD aparat, apnea test postaje dostupan svakom neurologu u kliničkom radu, posebno u našim uslovima, kada se do drugih drugih, skupljih metoda, teško stiže ili nam ostaju nedostižne.TCD apnea test, as a noninvasive and safe neuroultrasonographic method, provides useful information about vasomotor reactivity (VMR) in the indirect evaluation of cerebral autoregulation. Vasomotor reactivity is the ability of cerebral arterioles to constrict or to dilate in response to a vasoactive stimulus, mainly carbon dioxide. The aim of this doctoral thesis was to investigate and analyze changes in carotid hemodynamics in patients with ischemic stroke (IS) or transient ischemic attack (TIA) and symptomatic carotid stenosis in the preoperative and three-month postoperative period as well as the assessment of revascularisation effect of carotid endarterectomy (CEA). The study included 60 hospitalized patients who experienced a first ischemic stroke or TIA in the vasularisation area of anterior cerebral artery (ACA) and middle cerebral artery (MCA), all with carotid stenosis ≥70% ACI. Patients were hospitalized at the Clinic of Neurology, Clinical Center of Vojvodina, Department of Cardiovascular Surgery, Institute of Cardiovascular Diseases and the Department of Vascular Surgery in Novi Sad. Considering clinical manifestations of stroke, the patients were divided into three groups: patients with TIA and amaurosis fugax, with partial infarction in area ACA or ACM and with lacunar infarct. The study analyzed the impact of variabile and unvariable vascular risk factors on the incidence of ischemic stroke and TIA, but also on VMR, evaluated through Breath Holding Index (Breath Holding Index, BHI) on the ipsilateral and contralateral side from carotid stenosis. We analysed the correlation between the degree of carotid stenosis with preoperative values of BHI, BHI correlation to the severity of clinical findings, the impact of collateral circulation to the VMR, distribution of BHI in certain types of ischemic stroke and TIA as well as comparison of BHI in the pre and postoperative period of 30 and 90 days. On the basis of this research came the conclusion that reduced VMR is characteristic of ipsilateral carotid stenosis in preoperative period as well as number of developed collateral characteristics of different types of ipsilateral ischemic stroke and TIA; there is a negative correlation between the degree of carotid stenosis and BHI values. The hypothesis that the greater pathways causes preservation of VMR was not confirmed, while the positive correlation between BHI values in the preoperative and postoperative period was established. Reduced VMR has a negative impact on the degree of clinical picture severity. Recognizing the importance of TCD apnea test method, that can be used as a complementary method to other vasoactive tests in monitoring of carotid hemodynamics, is of special importance to the neurologists and vascular surgeons. This would contribute to the further evaluation of mechanism of ischemic stroke, planning of therapeutic approach and determining the prognosis of treated patients. The fact that most of neurological department has TCD device, apnea test becomes available to every neurologist in clinical work, specially in our conditions, when other methods remain unattainable