Patchy fibrosis promotes trigger–substrate interactions that both generate and maintain atrial fibrillation

Fibrosis has been mechanistically linked to arrhythmogenesis in multiple cardiovascular conditions, including atrial fibrillation (AF). Previous studies have demonstrated that fibrosis can create functional barriers to conduction which may promote excitation wavebreak and the generation of re-entry, while also acting to pin re-entrant excitation in stable rotors during AF. However, few studies have investigated the role of fibrosis in the generation of AF triggers in detail. We apply our in-house computational framework to study the impact of fibrosis on the generation of AF triggers and trigger–substrate interactions in two- and three-dimensional atrial tissue models. Our models include a reduced and efficient description of stochastic, spontaneous cellular triggers as well as a simple model of heterogeneous intercellular coupling. Our results demonstrate that fibrosis promotes the emergence of focal excitations, primarily through reducing the electrotonic load on individual fibre strands. This enables excitation to robustly initiate within these single strands before spreading to neighbouring strands and inducing a full tissue focal excitation. Enhanced conduction block can allow trigger–substrate interactions that result in the emergence of complex, re-entrant excitation patterns. This study provides new insight into the mechanisms by which fibrosis promotes the triggers and substrate necessary to induce and sustain arrhythmia

Полинеоплазии у больных увеальной меланомой по данным позитронно-эмиссионной томографии, совмещенной с компьютерной томографией (два клинических случая)

In addition to abdominal ultrasound and chest X-ray, positron emission tomography combined with computed tomography (PET/CT) has been increasingly used to diagnose metastatic disease in patients with uveal melanoma. We present two clinical cases of the second malignancy (synchronous polyneoplasia, colon cancer) that was eventually found during PET/CT in uveal melanoma patients performed to exclude dissemination of the neoplasm. It was shown that hybrid PET/CT is the most informative method in the diagnosis and monitoring of uveal melanoma patients. During one diagnostic procedure it enables to diagnose early stages of secondary malignancies, in addition to the assessment of metastatic dissemination.Наряду с ультразвуковым исследованием органов брюшной полости и рентгенографией органов грудной клетки для диагностики метастатической болезни у пациентов с увеальной меланомой все шире используют позитронно-эмиссионную томографию, совмещенную с компьютерной томографией (ПЭТ/КТ). Представлены два клинических наблюдения второй злокачественной опухоли (синхронной полинеоплазии – рака толстой кишки), ставшие случайной находкой при выполнении ПЭТ/КТ исследования больным увеальной меланомой с целью исключения генерализации опухолевого процесса. Показано, что наиболее информативным методом диагностики и мониторинга больных увеальной меланомой является гибридная технология ПЭТ/КТ, которая позволяет в рамках одного исследования помимо оценки распространенности метастатического процесса диагностировать вторые злокачественные опухоли на ранней стадии