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1.
Anesth Analg ; 139(5): 986-996, 2024 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-39136954

RESUMO

Transcatheter aortic valve replacement (TAVR) has become the dominant procedural modality for aortic valve replacement in the United States. The reported rates of neurological complications in patients undergoing TAVR have changed over time and are dependent on diagnostic definitions and modalities. Most strokes after TAVR are likely embolic in origin, and the incidence of stroke has decreased over time. Studies have yielded conflicting results when comparing stroke rates between TAVR and surgical aortic valve replacement (SAVR), especially due to differences in diagnostic criteria and neurocognitive testing. In this narrative review, we summarize the available data on the incidence of stroke, delirium, and cognitive decline after TAVR and highlight potential areas in need of future research. We also discuss silent cerebral ischemic lesions (SCILs) and their association with a decline in postoperative neurocognitive status after TAVR. Finally, we describe that the risk of delirium and postoperative decline is increased when nonfemoral access routes are used, and we highlight the need for standardized imaging and valid, repeatable methodologies to assess cognitive changes after TAVR.


Assuntos
Substituição da Valva Aórtica Transcateter , Humanos , Substituição da Valva Aórtica Transcateter/efeitos adversos , Fatores de Risco , Delírio/etiologia , Delírio/diagnóstico , Delírio/epidemiologia , Complicações Pós-Operatórias/etiologia , Complicações Pós-Operatórias/diagnóstico , Complicações Pós-Operatórias/epidemiologia , Estenose da Valva Aórtica/cirurgia , Acidente Vascular Cerebral/etiologia , Acidente Vascular Cerebral/epidemiologia , Resultado do Tratamento , Incidência , Valva Aórtica/cirurgia
2.
J Mol Cell Cardiol ; 167: 52-66, 2022 06.
Artigo em Inglês | MEDLINE | ID: mdl-35358843

RESUMO

Mitochondrial calcium (mCa2+) uptake couples changes in cardiomyocyte energetic demand to mitochondrial ATP production. However, excessive mCa2+ uptake triggers permeability transition and necrosis. Despite these established roles during acute stress, the involvement of mCa2+ signaling in cardiac adaptations to chronic stress remains poorly defined. Changes in NCLX expression are reported in heart failure (HF) patients and models of cardiac hypertrophy. Therefore, we hypothesized that altered mCa2+ homeostasis contributes to the hypertrophic remodeling of the myocardium that occurs upon a sustained increase in cardiac workload. The impact of mCa2+ flux on cardiac function and remodeling was examined by subjecting mice with cardiomyocyte-specific overexpression (OE) of the mitochondrial Na+/Ca2+ exchanger (NCLX), the primary mediator of mCa2+ efflux, to several well-established models of hypertrophic and non-ischemic HF. Cardiomyocyte NCLX-OE preserved contractile function, prevented hypertrophy and fibrosis, and attenuated maladaptive gene programs in mice subjected to chronic pressure overload. Hypertrophy was attenuated in NCLX-OE mice, prior to any decline in cardiac contractility. NCLX-OE similarly attenuated deleterious cardiac remodeling in mice subjected to chronic neurohormonal stimulation. However, cardiomyocyte NCLX-OE unexpectedly reduced overall survival in mice subjected to severe neurohormonal stress with angiotensin II + phenylephrine. Adenoviral NCLX expression limited mCa2+ accumulation, oxidative metabolism, and de novo protein synthesis during hypertrophic stimulation of cardiomyocytes in vitro. Our findings provide genetic evidence for the contribution of mCa2+ to early pathological remodeling in non-ischemic heart disease, but also highlight a deleterious consequence of increasing mCa2+ efflux when the heart is subjected to extreme, sustained neurohormonal stress.


Assuntos
Insuficiência Cardíaca , Trocador de Sódio e Cálcio , Animais , Cálcio/metabolismo , Sinalização do Cálcio , Cardiomegalia/metabolismo , Insuficiência Cardíaca/metabolismo , Humanos , Camundongos , Mitocôndrias/metabolismo , Miócitos Cardíacos/metabolismo , Trocador de Sódio e Cálcio/genética , Trocador de Sódio e Cálcio/metabolismo , Remodelação Ventricular
3.
Cureus ; 16(9): e69343, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-39398829

RESUMO

The clinical years of medical school are a time when students navigate a new learning environment. Due to inexperience, discordance may exist between veteran attendings and students who do not have their bearings in this new setting. We propose a solution to strengthen the clinician-student relationship by promoting a culture of goal-oriented clinical education via a two-pronged approach. First, standardized learning objectives should be established for each clinical rotation. Second, and arguably more importantly, students should create individualized goals to complement these objectives and further their personal educational interests. Once a culture of goal-oriented clinical education is implemented, we believe students will navigate their clinical years with increased confidence and competence. In this piece, we discuss our personal attitudes toward why clinicians and students should set goals, how they can set them, and what these goals should include. Once goals are established, feedback must be provided to students to continue the learning process. This comes in the form of comments from supervising preceptors who focus on areas of interest identified by the student, as well as from the results of standardized assessments. We passionately believe that together, the synergism of goal setting, feedback, and assessment creates a perfect mixture conducive to the formation of a positive learning environment.

4.
bioRxiv ; 2023 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-37131819

RESUMO

Background: Mitochondrial calcium (mCa2+) uptake through the mitochondrial calcium uniporter channel (mtCU) stimulates metabolism to meet acute increases in cardiac energy demand. However, excessive mCa2+ uptake during stress, as in ischemia-reperfusion, initiates permeability transition and cell death. Despite these often-reported acute physiological and pathological effects, a major unresolved controversy is whether mtCU-dependent mCa2+ uptake and long-term elevation of cardiomyocyte mCa2+ contributes to the heart's adaptation during sustained increases in workload. Objective: We tested the hypothesis that mtCU-dependent mCa2+ uptake contributes to cardiac adaptation and ventricular remodeling during sustained catecholaminergic stress. Methods: Mice with tamoxifen-inducible, cardiomyocyte-specific gain (αMHC-MCM × flox-stop-MCU; MCU-Tg) or loss (αMHC-MCM × Mcufl/fl; Mcu-cKO) of mtCU function received 2-wk catecholamine infusion. Results: Cardiac contractility increased after 2d of isoproterenol in control, but not Mcu-cKO mice. Contractility declined and cardiac hypertrophy increased after 1-2-wk of isoproterenol in MCU-Tg mice. MCU-Tg cardiomyocytes displayed increased sensitivity to Ca2+- and isoproterenol-induced necrosis. However, loss of the mitochondrial permeability transition pore (mPTP) regulator cyclophilin D failed to attenuate contractile dysfunction and hypertrophic remodeling, and increased isoproterenol-induced cardiomyocyte death in MCU-Tg mice. Conclusions: mtCU mCa2+ uptake is required for early contractile responses to adrenergic signaling, even those occurring over several days. Under sustained adrenergic load excessive MCU-dependent mCa2+ uptake drives cardiomyocyte dropout, perhaps independent of classical mitochondrial permeability transition pore opening, and compromises contractile function. These findings suggest divergent consequences for acute versus sustained mCa2+ loading, and support distinct functional roles for the mPTP in settings of acute mCa2+ overload versus persistent mCa2+ stress.

5.
bioRxiv ; 2023 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-37873405

RESUMO

The balance between mitochondrial calcium (mCa2+) uptake and efflux regulates ATP production, but if perturbed causes energy starvation or mCa2+ overload and cell death. The mitochondrial sodium-calcium exchanger, NCLX, is a critical route of mCa2+ efflux in excitable tissues, such as the heart and brain, and animal models support NCLX as a promising therapeutic target to limit pathogenic mCa2+ overload. However, the mechanisms that regulate NCLX activity remain largely unknown. We used proximity biotinylation proteomic screening to identify the NCLX interactome and define novel regulators of NCLX function. Here, we discover the mitochondrial inner membrane protein, TMEM65, as an NCLX-proximal protein that potently enhances sodium (Na+)-dependent mCa2+ efflux. Mechanistically, acute pharmacologic NCLX inhibition or genetic deletion of NCLX ablates the TMEM65-dependent increase in mCa2+ efflux. Further, loss-of-function studies show that TMEM65 is required for Na+-dependent mCa2+ efflux. Co-fractionation and in silico structural modeling of TMEM65 and NCLX suggest these two proteins exist in a common macromolecular complex in which TMEM65 directly stimulates NCLX function. In line with these findings, knockdown of Tmem65 in mice promotes mCa2+ overload in the heart and skeletal muscle and impairs both cardiac and neuromuscular function. We further demonstrate that TMEM65 deletion causes excessive mitochondrial permeability transition, whereas TMEM65 overexpression protects against necrotic cell death during cellular Ca2+ stress. Collectively, our results show that loss of TMEM65 function in excitable tissue disrupts NCLX-dependent mCa2+ efflux, causing pathogenic mCa2+ overload, cell death and organ-level dysfunction, and that gain of TMEM65 function mitigates these effects. These findings demonstrate the essential role of TMEM65 in regulating NCLX-dependent mCa2+ efflux and suggest modulation of TMEM65 as a novel strategy for the therapeutic control of mCa2+ homeostasis.

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