| Abstract | Moždani udar treći je vodeći uzrok smrti i drugi po učestalosti uzrok smrti među
kardiovaskularnim bolestima u razvijenim zemljama. Aterosklerotski plak karotidne arterije
uzrok je većine moždanih udara u bolesnika kod kojih je prisutan, bilo da uzrokuje
embolizaciju u moždani krvotok bilo da dovodi do značajnih hemodinamskih poremećaja
cerebralne cirkulacije. Predilekcijsko mjesto za nastanak aterosklerotskog plaka na
karotidnom stablu je bifurkacija zajedničke karotidne arterije odnosno bulbus unutarnje
karotidne arterije. Velike prospektivne randomizirane studije pokazale su korist od
endarterektomije unutarnje karotidne arterije u simptomatskih bolesnika te u nešto manjoj
mjeri i u onih bez simptoma. Zbog niske incidencije moždanog udara u asimptomatskih
bolesnika nameće se potreba da se identificiraju podskupine asimptomatskih bolesnika sa
povećanim rizikom, da bi se opravdalo kirurško liječenje. Histološki sastav plaka karotidne
arterije je upravo jedan od parametara koji bi mogli ukazivati na povećan rizik od moždanog
udara. Uz prisutne određene histološke karakteristike plaka indikacija za operaciju se može
donijeti i pri suženjima manjim od onih koja se sada smatraju indikacijom za operaciju.
Pokazano je da krvarenje u plak predstavlja znak nestabilnosti plaka i pogoduje njegovu
povećanju, te da predstavlja kritični trenutak kada stabilni plak prelazi u nestabilni
(vulnerabilni) plak, tj. plak koji češće dovodi do nastanka moždanog udara. Idealna
dijagnostička metoda morala bi pored točnog određivanja stupnja suženja, omogućiti i uvid u
sastav plaka, tj. ukazati na eventualno prisustvo karakteristika plaka koje ga čine
vulnerabilnim. Mi smo ovim radom pokazali da MSCT može otkriti plak kompliciran
krvarenjem sa osjetljivošću od 100% i specifičnošću od 70,4% uz graničnu vrijednost tkivne
gustoće od 33,8 HU. Drugim riječima, ni jedan plak kojemu je izmjerena gustoća veća od
33,8 HU nije bio kompliciran s krvarenjem. Prosječno suženje karotidnih arterija mjereno
MSCT-om bilo je 82,6% (± 9,6%), dok je doplerom dobiveno prosječno suženje od 80,4%
(±10,0%). (p=0,066878, Z= 1,832496, Wilcoxonov test ), što je potvrdilo visoku podudarnost
nalaza MSCT-a i doplera kod utvrđivanja stupnja suženja karotidne arterije. Našli smo da je
medijan tkivne gustoće AHA VIb tipa karotidnih plakova bio 14,7 HU (raspon -17,6 do
31,8), dok je medijan tkivne gustoće plakova nekompliciranih krvarenjem bio 54,3 HU
(raspon -23,6 do 150). Korištenjem Mann-Whitney U testa dobila se statistički značajna
razlika tkivne gustoće u navedene dvije skupine plakova (p=0,00003, U=97,00). Opisivanjem
ultrazvučno dominantno mekanih i miješanih plakova kao jedne grupe dobila se osjetljivost
ultrazvuka u otkrivanju krvarenja u plak od 100% i specifičnost od 48,1% . Time se UZV
osjetljivošću izjednačava MSCT-u dok mu je specifičnost manja za 22,3% (apsolutna razlika)
od one koju je pokazao MSCT. Bolji rezultati ultrazvuka zasigurno bi se dobili korištenjem
specijaliziranog softwarea koji omogućuje detaljniju analizu, detaljniju klasifikaciju i
kvantifikaciju dobivenih nalaza. Također postoji mogućnost da bi se korištenjem drugačije
(detaljnije) klasifikacije dobili drugačiji rezultati. Zbog količine zračenja i izlaganja
bolesnika kontrastnom sredstvu, MSCT iako prema ovoj studiji superiorniji u odnosu na UZV
u otkrivanju krvarenja u plak, kao jedina pretraga vjerojatno nije pogodna metoda za praćenje
dinamike progresije stupnja suženja niti za otkrivanje eventualne naknadne pojave krvarenja u
plak U ovom radu MSCT je pokazao vrlo visoku osjetljivost i umjerenu specifičnost u
otkrivanju krvarenja u karotidni plak. Plakovi sa tkivnom gustoćom iznad 33,8 HU nisu bili
komplicirani krvarenjem u plak. Tehnička poboljšanja CT opreme vjerojatno će poboljšati
specifičnost ove metode. Dopler i MSCT daju gotovo identične rezultate u mjerenju stupnja
suženja karotidne arterije. UZV je pokazao visoku osjetljivost ali nisku specifičnost u
otkrivanju krvarenja u plak. Primjenom odgovarajućeg softwarea vjerojatno bi se poboljšala
specifičnost ultrazvuka u otkrivanju krvarenja u plak. |
| Abstract (english) | Stroke is third leading cause of death and second leading cause of death among patients with
cardiovascular diseases in developed countries. Atherosclerotic carotid plaque is the main
cause of most strokes in people with carotid artery disease, by either causing embolisation or
reducing blood flow through cerebral circulation. Carotid artery bifurcation and proximal
segment of the internal carotid artery are the usual locations of the atherosclerotic carotid
plaque. Large randomized trials showed benefit of carotid endarterectomy in symptomatic
patients and to a lesser degree in asymptomatic patients. To justify carotid endarterectomy in
asymptomatic patients, higher risk supgroups of asymptomatic patients should be identified.
Histological content of the atherosclerotic plaque could be one of the indicators of its higher
propensity for causing a stroke. When certain histological characteristics of the plaque are
present, decision for carotid endarterectomy could be made even when degree of stenosis is
lower than that currently considered to be an indication for carotid endarterectomy. It has
been shown that occurence of hemorrhage within the atherosclerotic plaque represents a
transition point when a stable plaque becomes unstable (vulnerable) plaque i.e. it becomes
more prone to causing a neurologic event. The ideal diagnostic method should provide precise
measurement of the degree of carotid artery stenosis, and in the same time it should be able
to give information about histological content of the plaque thus detecting some
characteristics of the plaque that make it vulnerable. With this study, we showed that MSCT
could detect hemorrhage within the atherosclerotic carotid plaque with a sensitivity of 100%
and specificity of 70,4% with a cut-off value of tissue density of 33.8 HU. We found that no
plaque with tissue density greater then 33.8 HU was complicated with hemorrhage within the
plaque. The mean carotid artery stenosis measured by MSCT and doppler was 82.6% (±
9.6%) and 80.4% (±10.0%), respectively (p=0.066878, Z=1.832496, Wilcoxon test). These
results confirmed a high degree of concordance of MSCT and doppler in measuring degree of
carotid artery stenosis. The median tissue density of the plaques AHA type VIb was 14.7 HU
(range -17.6 to 31.8), and the median tissue density of the plaques not complicated with
hemorrhage was 54.3 HU (range -23.6 to 31.8). The Mann-Whitney U test showed significant
difference between these two groups (p=0.00003, U=97.00). If plaques presented on
ultrasound as predominantly soft and those of combined content had been considered as a
single group we reached specificity of ultrasound in detecting hemorrhage within the plaque
of 100% and specificity of 48.1%. By doing so, we equalled sensitivity of ultrasound with
sensitivity of MSCT but at the cost of the specificity that was 22.3% (absolute difference) less
than specificity of MSCT. Better results of ultrasound analysis would probably be obtained by
using a specialized software which enables more detailed analysis, more detalied
classification and quantification of the results. Also, there is posibility that different results
would be found if different (more detailed) classification was used. Although we showed that
MSCT was superior to ultrasound in detecting hemorrhage within the plaque, it is probably
not the ideal method for niether follow up of the progression of carotid artery stenosis nor for
detecting later occurence of the hemorrhage within the plaque, due to the exposure of the
patients to radiation and contrast agent. In this study MSCT showed very high level of
sensitivity and moderate level of specificity in detecting hemorrhage within the
atherosclerotic plaque. The plaques with tissue density above 33.8 HU were not complicated
with hemorrhage. Techical advancement of the CT equipment will probablay increase the
specificity of the method. MSCT and doppler showed almost identical results in measuring
degree of the carotid artery stenosis. Ultrasound showed very high level of sensitivity and
low level of specificity in detecting hemorrhage within the plaque. By using specialized
software, the specificity of the ultrasound could probably be increased. |
