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IntroductionLeft atrial (LA) tissue characteristics may play an important role in atrial fibrillation (AF) induction and perpetuation. Although frequently used in clinical practice, computed tomography (CT) has not been employed to describe differences in LA wall properties between AF patients and controls. We sought to noninvasively characterize AF-associated differences in LA tissue using CT.MethodsCT images of the LA were obtained in 98 consecutive patients undergoing AF ablation and in 89 controls. A custom software algorithm was used to measure wall thickness and density in four prespecified regions of the LA.ResultsOn average, LA walls were thinner (-15.5%, 95% confidence interval [CI] -23.2 to -7.8%, P < 0.001) and demonstrated significantly lower density (-19.7 Hounsfield Units [HU], 95% CI -27.0 to -12.5 HU, P < 0.001) in AF patients compared to controls. In linear mixed models adjusting for demographics, clinical variables, and other CT measurements, the average LA, interatrial septum, LA appendage, and anterior walls remained significantly thinner in AF patients. After adjusting for the same potential confounders, history of AF was associated with reduced density in the LA anterior wall and increased density below the right inferior pulmonary vein and in the LA appendage.ConclusionApplication of an automated measurement algorithm to CT imaging of the atrium identified significant thinning of the LA wall and regional alterations in tissue density in patients with a history of AF. These findings suggest differences in LA tissue composition can be noninvasively identified and quantified using CT.

Communication between the gametophytes is vital for angiosperm fertilisation. Multiple CrRLK1L‐type receptor kinases prevent premature pollen tube burst, while another CrRLK1L protein, FERONIA (FER), is required for pollen tube reception in the female gametophyte. We report here the identification of two additional CrRLK1L homologues, HERCULES RECEPTOR KINASE 1 (HERK1) and ANJEA (ANJ), which act redundantly to promote pollen tube growth arrest at the synergid cells. HERK1 and ANJ localise to the filiform apparatus of the synergid cells in unfertilised ovules, and in herk1 anj mutants, a majority of ovules remain unfertilised due to pollen tube overgrowth, together indicating that HERK1 and ANJ act as female determinants for fertilisation. As in fer mutants, the synergid cell‐specific, endomembrane protein NORTIA (NTA) is not relocalised after pollen tube reception; however, unlike fer mutants, reactive oxygen species levels are unaffected in herk1 anj double mutants. Both ANJ and HERK1 associate with FER and its proposed co‐receptor LORELEI (LRE) in planta. Together, our data indicate that HERK1 and ANJ act with FER to mediate female–male gametophyte interactions during plant fertilisation. Synopsis: The CrRLK1L receptor kinases HERK1 and ANJ are genetically redundant during pollen tube reception in Arabidopsis. Both proteins interact with the CrRLK1L receptor FER and its putative co‐receptor LRE, however the role of FER in fertilisation extends to production of reactive oxygen species in ovules while HERK1 and ANJ are not involved in this process. Double mutants of HERK1 and ANJ produce fewer seeds as pollen tube overgrowth occurs in the majority of ovules in a maternally‐controlled phenotype.HERK1 and ANJ are both expressed in the synergid cells, where other fertilisation components in the form of CrRLK1L receptor FERONIA, its co‐receptor LORELEI, and downstream protein NORTIA are also located.Kinase activity of HERK1 and ANJ is not required for complementation of the pollen tube reception phenotype.HERK1 and ANJ interact with FER and LRE.Unlike FER, HERK1 and ANJ are not required for pre‐fertilisation production of reactive oxygen species. [ABSTRACT FROM AUTHOR]