{"id":6470,"date":"2026-10-19T09:48:57","date_gmt":"2026-10-19T09:48:57","guid":{"rendered":"https:\/\/phd.hi.is\/doktorsvorn\/doktorsvorn-i-laeknavisindum-marianna-gardarsdottir\/"},"modified":"2026-10-19T09:48:57","modified_gmt":"2026-10-19T09:48:57","slug":"doktorsvorn-i-laeknavisindum-marianna-gardarsdottir","status":"publish","type":"phd_defence","link":"https:\/\/phd.hi.is\/en\/doktorsvorn\/doktorsvorn-i-laeknavisindum-marianna-gardarsdottir\/","title":{"rendered":"Doktorsv\u00f6rn \u00ed l\u00e6knav\u00edsindum &#8211; Mar\u00edanna Gar\u00f0arsd\u00f3ttir"},"content":{"rendered":"<div class=\"field-items\">\n<div class=\"field-item even\" property=\"content:encoded\">\n<p>Fimmtudaginn 21. ma\u00ed ver Mar\u00edanna Gar\u00f0arsd\u00f3ttir doktorsritger\u00f0 s\u00edna \u00ed l\u00e6knav\u00edsindum vi\u00f0 L\u00e6knadeild H\u00e1sk\u00f3la \u00cdslands. Ritger\u00f0in ber heiti\u00f0: \u00de\u00e1ttur g\u00e1ttatifs og \u00f3s\u00e6\u00f0arst\u00edfleika \u00ed formger\u00f0 og starfsemi heilans. The role of atrial fibrillation and aortic stiffness in brain structure and function.<\/p>\n<p>Andm\u00e6lendur eru dr. Jens Cosedis Nielsen, yfirl\u00e6knir og pr\u00f3fessor vi\u00f0 \u00c1r\u00f3sah\u00e1sk\u00f3la, og dr. David F\u00e4llmar, d\u00f3sent vi\u00f0 H\u00e1sk\u00f3lasj\u00fakrah\u00fasi\u00f0 \u00ed Upps\u00f6lum.<\/p>\n<p>Umsj\u00f3narkennari og lei\u00f0beinandi var Dav\u00ed\u00f0 O. Arnar, pr\u00f3fessor og me\u00f0lei\u00f0beinandi var Sigur\u00f0ur Sigur\u00f0sson, framkv\u00e6mdastj\u00f3ri. Auk \u00feeirra s\u00e1tu \u00ed doktorsnefnd Thor Aspelund, pr\u00f3fessor og Vilmundur Gu\u00f0nason, pr\u00f3fessor.<\/p>\n<p>S\u00e6d\u00eds S\u00e6varsd\u00f3ttir, pr\u00f3fessor og deildarforseti L\u00e6knadeildar, stj\u00f3rnar ath\u00f6fninni sem fer fram \u00ed Ver\u00f6ld, \u00a0H\u00fas Vigd\u00edsar, Au\u00f0arsal og hefst kl. 09.00.<\/p>\n<p><strong>\u00c1grip<\/strong><\/p>\n<p>G\u00e1ttatif er algengast langvarandi hjartsl\u00e1ttartruflana og eykst t\u00ed\u00f0ni g\u00e1ttatifs me\u00f0 h\u00e6kkandi aldri. \u00dea\u00f0 er vel \u00feekkt a\u00f0 g\u00e1ttatif eykur h\u00e6ttu \u00e1 heilabl\u00f3\u00f0falli, en einnig hefur komi\u00f0 \u00ed lj\u00f3s a\u00f0 einstaklingar me\u00f0 langvarandi g\u00e1ttatif eru l\u00edklegri til a\u00f0 upplifa minnistruflanir. \u00de\u00e1 hafa breytingar \u00ed formger\u00f0 heilans s\u00e9st, jafnvel \u00e1n heilabl\u00f3\u00f0falls, en \u00e1st\u00e6\u00f0ur \u00feessa eru ekki a\u00f0 fullu \u00feekktar. \u00deessi ritger\u00f0 kanna\u00f0i hvort breytingar \u00e1 bl\u00f3\u00f0fl\u00e6\u00f0i fr\u00e1 hjartanu til heilans g\u00e6ti a\u00f0 einhverju leyti sk\u00fdrt \u00feessi \u00e1hrif.<\/p>\n<p>Heilinn er h\u00e1\u00f0ur st\u00f6\u00f0ugu bl\u00f3\u00f0fl\u00e6\u00f0i til a\u00f0 f\u00e1 n\u00e6gilegt s\u00farefni og n\u00e6ringarefni. \u00cd g\u00e1ttatifi ver\u00f0ur hjartsl\u00e1tturinn \u00f3reglulegur og minna skilvirkur og hefur jafnvel \u00e1hrif \u00e1 hvernig bl\u00f3\u00f0 er flutt til heilans. \u00cd fyrstu ranns\u00f3kninni s\u00e1st a\u00f0 hj\u00e1 eldri einstaklingum me\u00f0 langvarandi g\u00e1ttatif var bl\u00f3\u00f0fl\u00e6\u00f0i til heilans, sem m\u00e6lt var me\u00f0 segul\u00f3mun, minna en hj\u00e1 \u00feeim sem voru \u00ed e\u00f0lilegum s\u00ednustakti. Heilar\u00famm\u00e1l var einnig minna hj\u00e1 \u00feeim sem h\u00f6f\u00f0u langvarandi g\u00e1ttatif einstaklingum en ekki komu \u00ed lj\u00f3s nein \u00e1hrif \u00e1 minni og vitr\u00e6na getu.<\/p>\n<p>\u00cd annarri ranns\u00f3kn voru einstaklingar me\u00f0 g\u00e1ttatif rannsaka\u00f0ir fyrir og eftir rafvendingu, sem getur komi\u00f0 hjartsl\u00e6ttinum \u00ed r\u00e9ttan s\u00ednustakt. \u00deeir sem f\u00f3ru \u00ed r\u00e9ttan takt eftir \u00e1rangursr\u00edka rafvendingu s\u00fdndu auki\u00f0 bl\u00f3\u00f0fl\u00e6\u00f0i til heilans, en \u00feeir sem voru \u00e1fram \u00ed g\u00e1ttatifi s\u00fdndu enga breytingu \u00e1 bl\u00f3\u00f0fl\u00e6\u00f0is. \u00deetta bendir til \u00feess a\u00f0 l\u00e6gra bl\u00f3\u00f0fl\u00e6\u00f0i til heilans \u00ed g\u00e1ttatifi s\u00e9 ekki vi\u00f0varandi heldur geti aukist \u00feegar r\u00e9ttum takti er n\u00e1\u00f0.\u00a0<\/p>\n<p>\u00cd ritger\u00f0inni var l\u00edka sko\u00f0a\u00f0 tengt \u00e1stand, \u00f3s\u00e6\u00f0arst\u00edfleiki. \u00deegar f\u00f3lk eldist getur \u00f3s\u00e6\u00f0in, er liggur fr\u00e1 hjartanu, st\u00edfna\u00f0. \u00deetta hefur \u00e1hrif \u00e1 hvernig \u00fer\u00fdstingsbylgjur bl\u00f3\u00f0sins fer\u00f0ast um l\u00edkamann og getur auki\u00f0 \u00e1lag \u00e1 sm\u00e1ar \u00e6\u00f0ar, me\u00f0al annars \u00ed heilanum. Ni\u00f0urst\u00f6\u00f0urnar s\u00fdndu a\u00f0 einstaklingar me\u00f0 st\u00edfari \u00f3s\u00e6\u00f0 h\u00f6f\u00f0u l\u00e6gra bl\u00f3\u00f0fl\u00e6\u00f0i til heilans og aukin merki um sm\u00e1a\u00e6\u00f0asj\u00fakd\u00f3m \u00ed heilanum, auk \u00feess sem heilar\u00famm\u00e1l var minna, en ekki s\u00e1ust \u00e1hrif \u00e1 vitr\u00e6na getu.<\/p>\n<p>Samanteki\u00f0 benda \u00feessar ni\u00f0urst\u00f6\u00f0ur til a\u00f0 b\u00e6\u00f0i \u00f3reglulegur hjartsl\u00e1ttur og st\u00edf \u00f3s\u00e6\u00f0 geti haft \u00e1hrif \u00e1 heilann me\u00f0 breytingum \u00e1 bl\u00f3\u00f0fl\u00e6\u00f0i til heilans. \u00c1 me\u00f0an aldur er mikilv\u00e6gasti \u00fe\u00e1tturinn sem hefur \u00e1hrif \u00e1 heilann og heilaheilsu geta hjartsl\u00e1ttur og \u00e1stand \u00e6\u00f0a \u00e1tt sinn \u00fe\u00e1tt \u00ed snemmkomnum \u00e1hrifum \u00e1 heilann sem geta s\u00ed\u00f0ar birst sem \u00ed \u00e1hrifum \u00e1 vitr\u00e6na getu. Skilningur \u00e1 \u00fev\u00ed hvernig sj\u00fakd\u00f3mar \u00ed hjarta- og \u00e6\u00f0akerfinu hafa \u00e1hrif \u00e1 heilaheilsu getur gefi\u00f0 v\u00edsbendingar um hvernig h\u00e6gt er a\u00f0 vernda heilann og vitr\u00e6na getu til framt\u00ed\u00f0ar me\u00f0 h\u00e6kkandi aldri f\u00f3lks.\u00a0\u00a0<\/p>\n<p><strong>Abstract<\/strong><\/p>\n<p>Atrial fibrillation is the most common long-lasting heart rhythm disorder and becomes more frequent with increasing age. It is well known that atrial fibrillation increases the risk of stroke and in recent years researchers have also found that people with atrial fibrillation are more likely to experience memory problems and changes in brain structure, even without stroke, but the cause is not fully understood. This thesis explored whether changes in blood flow between the heart and the brain might help explain this connection.<\/p>\n<p>The brain does depend on a steady supply of blood flow to receive oxygen and nutrients. In atrial fibrillation, the heartbeat becomes irregular and less efficient, and this may affect how blood is delivered to the brain. In the first study, older individuals with long-lasting atrial fibrillation had lower blood flow to the brain compared with those who were in normal sinus heart rhythm. They also had smaller brain volumes but differences in cognitive function were, however, not observed.<\/p>\n<p>In a second study, people with atrial fibrillation were examined before and after electrical cardioversion, which may restore normal sinus heart rhythm. Individuals who successfully returned to normal rhythm showed an improvement in brain blood flow, but those who remained in atrial fibrillation did not. This suggests that reduced blood flow in atrial fibrillation may not be permanent and can improve when normal rhythm is restored.<\/p>\n<p>The thesis also examined a related condition called aortic stiffness. As people age, the large artery leaving the heart, the aorta, can become stiffer. This changes how blood pressure waves travel through the body and may increase stress on small blood vessels, including in the brain. The results showed that individuals with stiffer arteries had lower blood flow to the brain and more signs of degenerative changes in the brain, as well as smaller brain volume. Cognitive performance was not affected.<\/p>\n<p>Together, these findings suggest that both irregular heart rhythm and stiffened aorta may affect the brain through changes in blood flow to the brain. While aging remains the most important factor influencing brain structure and brain health, heart rhythm and vascular health appear to play an early role in structural and functional changes in the brain. Understanding how cardiac and vascular conditions influence brain health may help guide future strategies to protect cognitive function as people grow older.<\/p>\n<p><strong>Um doktorsefni\u00f0<\/strong><\/p>\n<p>Mar\u00edanna Gar\u00f0arsd\u00f3ttir er f\u00e6dd 1969 \u00ed Reykjav\u00edk. H\u00fan lauk st\u00fadentspr\u00f3fi fr\u00e1 n\u00fdm\u00e1ladeild Menntask\u00f3lans \u00ed Reykjav\u00edk 1989 og emb\u00e6ttispr\u00f3fi fr\u00e1 L\u00e6knadeild H\u00e1sk\u00f3la \u00cdslands 1999. A\u00f0 loknu kand\u00eddats\u00e1ri starfa\u00f0i Mar\u00edanna \u00e1 augndeild og r\u00f6ntgendeild Landsp\u00edtala og h\u00e9lt svo utan til s\u00e9rn\u00e1ms vi\u00f0 Sahlgrenska h\u00e1sk\u00f3lasj\u00fakrah\u00fasi\u00f0 og Barnasp\u00edtala Viktor\u00edu drottningar \u00ed Gautaborg. Mar\u00edanna lauk s\u00e9rn\u00e1mi \u00ed myndgreiningu 2007 og sneri \u00fe\u00e1 heim til starfa sem s\u00e9rfr\u00e6\u00f0il\u00e6knir \u00e1 Landsp\u00edtala. Fr\u00e1 2024 hefur Mar\u00edanna starfa\u00f0 sem forst\u00f6\u00f0uma\u00f0ur myndgreiningar\u00fej\u00f3nustu Landsp\u00edtala. Foreldrar Mar\u00ed\u00f6nnu eru Maia Sigur\u00f0ard\u00f3ttir s\u00e1lfr\u00e6\u00f0ingur (l\u00e9st 2012) og Gar\u00f0ar G\u00edslason h\u00e6star\u00e9ttard\u00f3mari. Maki Mar\u00ed\u00f6nnu er Sveinbj\u00f6rn J\u00f3hannesson, h\u00fasasmi\u00f0ur og vi\u00f0skiptafr\u00e6\u00f0ingur, og d\u00e6tur hennar eru Maia og Arna Snorrad\u00e6tur.<\/p>\n<\/div><\/div>","protected":false},"featured_media":5889,"template":"","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"_phd_date_start":"2026-05-21T09:00:00+00:00","_phd_date_end":"2026-05-21T12:00:00+00:00","_phd_location":"Ver\u00f6ld - H\u00fas Vigd\u00edsar Au\u00f0arsalur","_phd_admission":"A\u00f0gangur \u00f3keypis","_phd_thesis_title":"\u00de\u00e1ttur g\u00e1ttatifs og \u00f3s\u00e6\u00f0arst\u00edfleika \u00ed formger\u00f0 og starfsemi heilans. 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