RESUMO
BACKGROUND: Coronary artery bypass grafting (CABG) is a cornerstone treatment for coronary artery disease, with the use of saphenous vein grafts (SVGs) being prevalent. However, SVGs are susceptible to high failure rates due to graft inflammation, intimal hyperplasia, and atherosclerosis, leading to a substantial number of patients requiring revascularization. Percutaneous coronary intervention (PCI) of SVGs poses unique challenges, including increased risk of distal embolization and perforation due to the grafts' structure and atherosclerotic nature. The role of intravascular lithotripsy (IVL) in calcific SVG lesions has not been elucidated. METHODS: We retrospectively analyzed four cases of patients treated with IVL for SVG stenosis at Leiden University Medical Centre between May 2019 and December 2023. Quantitative coronary analysis and intravascular ultrasound were utilized to assess procedural success and mid- to long-term clinical outcomes were reported as well. RESULTS: In all 4 cases, IVL was performed in stent (2 due to calcific in-stent neoatherosclerosis; 2 bail-out due to extrinsic stent calcification). No major adverse cardiovascular events (MACE) were reported during mid- to long-term follow-up. The procedure demonstrated effective calcium cracking, leading to optimal stent expansion and minimal residual stenosis with a low risk of procedural complications. CONCLUSIONS: IVL represents a promising approach for managing calcified peri-stent SVG lesions, showing potential for safe and effective revascularization with minimal complications. These findings suggest that IVL could be incorporated into the treatment paradigm for calcified peri-stent SVG stenosis, warranting further investigation in larger, prospective studies to validate its efficacy and safety.
RESUMO
BACKGROUND: Intravascular lithotripsy (IVL) combined with rotational atherectomy (RA), known as Rotatripsy, is used to treat severe coronary artery calcification (CAC), though data on efficacy, midterm safety and use sequence is limited. We aimed to identify indicators for Rotatripsy use and to assess its safety and success rates, both acutely and at 1-year follow-up. METHODS: Patients undergoing Rotatripsy for severe CAC across six centers from May 2019 to December 2023 were included. Demographic, clinical, procedural and follow-up data were collected. Efficacy endpoints included device success (delivery of the RA-burr and IVL-balloon across the target lesion and administration of therapy without related complications), technical success (TIMI 3 flow and residual stenosis <30% by quantitative coronary analysis) and procedural success [composite of technical success with absence of in-hospital major adverse cardiovascular events (MACE: cardiac death, myocardial infarction or target vessel revascularization). Safety endpoints comprised Rotatripsy-related complications and MACE at 1-year follow-up. RESULTS: A total of 114 patients (75 ± 9 years, 78% male) underwent Rotatripsy for 120 lesions. In the majority of procedures RA was followed by IVL, mostly electively (n = 68, 57%) but also for balloon underexpansion (n = 37, 31%) and stent crossing failure (n = 1, 1%). Diverse and complex target lesions were addressed with an average SYNTAX score of 24.6 ± 13.0. Device, technical and procedural success were 97%, 94% and 93%, respectively. Therapy-related complications included two (2%) coronary perforations, one (1%) coronary dissection and one (1%) burr entrapment. At 1-year follow-up(present in 77(67%) patients), MACE occurred in 7(9%) cases. CONCLUSIONS: Over a 1-year follow-up period, Rotatripsy was safe and effective, predominantly using RA electively before IVL.
Assuntos
Aterectomia Coronária , Doença da Artéria Coronariana , Litotripsia , Índice de Gravidade de Doença , Calcificação Vascular , Humanos , Masculino , Feminino , Idoso , Fatores de Tempo , Aterectomia Coronária/efeitos adversos , Resultado do Tratamento , Calcificação Vascular/diagnóstico por imagem , Calcificação Vascular/terapia , Calcificação Vascular/mortalidade , Doença da Artéria Coronariana/terapia , Doença da Artéria Coronariana/diagnóstico por imagem , Doença da Artéria Coronariana/mortalidade , Idoso de 80 Anos ou mais , Litotripsia/efeitos adversos , Fatores de Risco , Estudos Retrospectivos , Estados UnidosRESUMO
BACKGROUND: Use of intravascular lithotripsy (IVL) for treating peri-stent calcification is increasing. However, this indication remains 'off-label'. We aimed to investigate the efficacy and clinical outcomes of in-stent IVL. METHODS: Patients from five European centers who underwent in-stent IVL were included between 2019 and 2023. Demographic, clinical, procedural and follow-up data were collected from electronic hospital records. Angiographic and intracoronary imaging (ICI) data were analyzed in a centralized core-laboratory. RESULTS: Of 101 patients (71.2 ± 9.2 years), 56(55 %) received in-stent IVL for late stent failure (median 109 days post-PCI) due to calcific neoatherosclerosis or extra-stent calcification(late-IVL), while 45(45 %) underwent bail-out IVL due to stent infraexpasion (immediate-IVL). Both late-IVL and immediate-IVL significantly improved angiographic %diameter stenosis (73.7[59.6-89.8]% to 16.4 [10.4-26.9]%;p < 0.0001 and 28.6[22.5-43.3]% to 14.1[10.3-29.4]%;p < 0.0001, and minimum lumen area (MLA) (3.4 ± 1.2 to 8.6 ± 2.5 mm2;p < 0.002 and 5.4 ± 1.9 to 7.3 ± 1.9;p < 0.0001).Device(98 %) and procedural success(80 %) were high. MACE rates in-hospital (2 %), 30-days (3 %),6-months(5 %) and 1-year(7 %) were low and comparable in both groups. Acute diameter gain was lower in immediate-IVL (2.1 ± 0.7 mm vs. 0.5 ± 0.4 mm;p < 0.0001). This, however, was explained by significant differences in pre-IVL angiographic and ICI parameters (%diameter stenosis 73.7[59.6-89.8] vs. 28.6[22.5-43.3]%; p < 0.0001 and MLA (3.4 ± 1.2 vs 5.4 ± 1.9 mm2; p < 0.0001), whereas post-IVL percentage diameter stenosis (16.4(10.4-26.9) vs. 14.1(10.3-29.4);p = 0.914) and MLA (8.6 ± 2.5vs. 7.4 ± 1.9 mm2;p = 0.064) in late- and immediate-IVL were comparable. CONCLUSIONS: IVL in-stent due to peri-stent calcification is an effective strategy, both late and immediately after stent implantation. Overall, MACE rates at short- and mid-term were low and comparable in both groups, although clinical findings should be taken with caution.
Assuntos
Calcinose , Litotripsia , Intervenção Coronária Percutânea , Calcificação Vascular , Humanos , Constrição Patológica , Litotripsia/efeitos adversos , Stents , Resultado do Tratamento , Calcificação Vascular/diagnóstico por imagem , Calcificação Vascular/terapiaAssuntos
Anomalias dos Vasos Coronários , Fístula Vascular , Humanos , Resultado do Tratamento , Ecocardiografia , Fístula Vascular/diagnóstico por imagem , Fístula Vascular/etiologia , Fístula Vascular/cirurgia , Angiografia , Átrios do Coração/diagnóstico por imagem , Átrios do Coração/cirurgia , Angiografia CoronáriaRESUMO
Coronary access difficulty and stent compression by the juxtaposed aortic valve leaflet hamper percutaneous management of delayed coronary artery obstruction (CAO) after valve-in-valve (Edwards Sapien 3 in St. Jude Trifecta) transcatheter aortic valve replacement (TAVR). Here, we present a case of delayed post-TAVR CAO treated with intravascular lithotripsy and multistenting to overcome stent compression by the adjacent calcified leaflet.
Assuntos
Estenose da Valva Aórtica , Oclusão Coronária , Próteses Valvulares Cardíacas , Substituição da Valva Aórtica Transcateter , Humanos , Substituição da Valva Aórtica Transcateter/efeitos adversos , Resultado do Tratamento , Valva Aórtica/diagnóstico por imagem , Valva Aórtica/cirurgia , Oclusão Coronária/diagnóstico por imagem , Oclusão Coronária/etiologia , Oclusão Coronária/terapia , Estenose da Valva Aórtica/diagnóstico por imagem , Estenose da Valva Aórtica/cirurgia , Desenho de PróteseAssuntos
Angioplastia Coronária com Balão , Aterectomia Coronária , Doença da Artéria Coronariana , Litotripsia , Calcificação Vascular , Humanos , Aterectomia Coronária/efeitos adversos , Doença da Artéria Coronariana/diagnóstico por imagem , Doença da Artéria Coronariana/terapia , Angioplastia Coronária com Balão/efeitos adversos , Coração , Resultado do Tratamento , Calcificação Vascular/diagnóstico por imagem , Calcificação Vascular/terapia , Angiografia CoronáriaAssuntos
Artéria Torácica Interna , Infarto do Miocárdio , Humanos , Anastomose de Artéria Torácica Interna-Coronária/efeitos adversos , Artéria Torácica Interna/diagnóstico por imagem , Infarto do Miocárdio/diagnóstico por imagem , Infarto do Miocárdio/etiologia , Infarto do Miocárdio/terapia , Resultado do TratamentoRESUMO
Stent underexpansion is a common problem in heavily calcified coronary lesions treated with percutaneous coronary intervention, and has been associated with in-stent restenosis, stent thrombosis and, subsequently, poor clinical outcomes. Adequate preparation of heavily calcified coronary lesions (e.g. using non-compliant balloons, cutting/scoring balloons, rotational/orbital atherectomy or intravascular lithotripsy) prior to stent implantation is essential in preventing stent underexpansion. However, in certain cases the deployed stent may remain underexpanded despite extensive lesion preparation. To date, no consensus exists on how to treat stent underexpansion in this scenario. We present a cases series in which post-stenting intravascular lithotripsy was performed to treat acute stent underexpansion in heavily calcified lesions, describing the technical aspects, angiographic results as well as clinical outcomes at mid-term follow-up.
Assuntos
Aterectomia Coronária , Doença da Artéria Coronariana , Litotripsia , Calcificação Vascular , Aterectomia Coronária/efeitos adversos , Aterectomia Coronária/métodos , Angiografia Coronária , Doença da Artéria Coronariana/diagnóstico por imagem , Doença da Artéria Coronariana/terapia , Humanos , Stents , Resultado do Tratamento , Calcificação Vascular/diagnóstico por imagem , Calcificação Vascular/terapiaRESUMO
Electrical cardioversion (ECV), a mainstay in atrial fibrillation (AF) treatment, is unsuccessful in up to 10-20% of patients. An important aspect of the remodeling process caused by AF is the constitutive activition of the atrium-specific acetylcholine-dependent potassium current (IK,ACh â IK,ACh-c), which is associated with ECV failure. This study investigated the role of IK,ACh-c in ECV failure and setting the atrial defibrillation threshold (aDFT) in optically mapped neonatal rat cardiomyocyte monolayers. AF was induced by burst pacing followed by application of biphasic shocks of 25-100 V to determine aDFT. Blocking IK,ACh-c by tertiapin significantly decreased DFT, which correlated with a significant increase in wavelength during reentry. Genetic knockdown experiments, using lentiviral vectors encoding a Kcnj5-specific shRNA to modulate IK,ACh-c, yielded similar results. Mechanistically, failed ECV was attributed to incomplete phase singularity (PS) removal or reemergence of PSs (i.e. re-initiation) through unidirectional propagation of shock-induced action potentials. Re-initiation occurred at significantly higher voltages than incomplete PS-removal and was inhibited by IK,ACh-c blockade. Whole-heart mapping confirmed our findings showing a 60% increase in ECV success rate after IK,ACh-c blockade. This study provides new mechanistic insight into failing ECV of AF and identifies IK,ACh-c as possible atrium-specific target to increase ECV effectiveness, while decreasing its harmfulness.
Assuntos
Acetilcolina/metabolismo , Fibrilação Atrial/metabolismo , Cardioversão Elétrica/efeitos adversos , Canais de Potássio Corretores do Fluxo de Internalização/metabolismo , Canais de Potássio/metabolismo , Potenciais de Ação , Animais , Fibrilação Atrial/genética , Fibrilação Atrial/fisiopatologia , Fibrilação Atrial/terapia , Técnicas de Silenciamento de Genes , Átrios do Coração/metabolismo , Átrios do Coração/fisiopatologia , Humanos , Miócitos Cardíacos/metabolismo , Miócitos Cardíacos/patologia , Técnicas de Patch-Clamp , Canais de Potássio/genética , Canais de Potássio Corretores do Fluxo de Internalização/genética , RatosRESUMO
AIMS: Fibrosis increases arrhythmogenicity in myocardial tissue by causing structural and functional disruptions in the cardiac syncytium. Forced fusion of fibroblastic cells with adjacent cardiomyocytes may theoretically resolve these disruptions. Therefore, the electrophysiological effects of such electrical and structural integration of fibroblastic cells into a cardiac syncytium were studied. METHODS AND RESULTS: Human ventricular scar cells (hVSCs) were transduced with lentiviral vectors encoding enhanced green fluorescent protein alone (eGFP↑-hVSCs) or together with the fusogenic vesicular stomatitis virus G protein (VSV-G/eGFP↑-hVSCs) and subsequently co-cultured (1:4 ratio) with neonatal rat ventricular cardiomyocytes (NRVMs) in confluent monolayers yielding eGFP↑- and VSV-G/eGFP↑-co-cultures, respectively. Cellular fusion was induced by brief exposure to pH = 6.0 medium. Optical mapping experiments showed eGFP↑-co-cultures to be highly arrhythmogenic [43.3% early afterdepolarization (EAD) incidence vs. 7.7% in control NRVM cultures, P < 0.0001], with heterogeneous prolongation of action potential (AP) duration (APD). Fused VSV-G/eGFP↑-co-cultures displayed markedly lower EAD incidence (4.6%, P < 0.001) than unfused co-cultures, associated with decreases in APD, APD dispersion, and decay time of cytosolic Ca(2+) waves. Heterokaryons strongly expressed connexin43 (Cx43). Also, maximum diastolic potential in co-cultures was more negative after fusion, while heterokaryons exhibited diverse mixed NRVM/hVSC whole-cell current profiles, but consistently showed increased outward Kv currents compared with NRVMs or hVSCs. Inhibition of Kv channels by tetraethylammonium chloride abrogated the anti-arrhythmic effects of fusion in VSV-G/eGFP↑-co-cultures raising EAD incidence from 7.9 to 34.2% (P < 0.001). CONCLUSION: Forced fusion of cultured hVSCs with NRVMs yields electrically functional heterokaryons and reduces arrhythmogenicity by preventing EADs, which is, at least partly, attributable to increased repolarization force.
Assuntos
Antiarrítmicos/farmacologia , Arritmias Cardíacas/metabolismo , Técnicas de Cocultura , Ventrículos do Coração/citologia , Miocárdio/metabolismo , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/metabolismo , Potenciais de Ação/fisiologia , Animais , Células Cultivadas , Ventrículos do Coração/efeitos dos fármacos , Humanos , RatosRESUMO
AIMS: Atrial fibrillation (AF) is the most common cardiac arrhythmia and often involves reentrant electrical activation (e.g. spiral waves). Drug therapy for AF can have serious side effects including proarrhythmia, while electrical shock therapy is associated with discomfort and tissue damage. Hypothetically, forced expression and subsequent activation of light-gated cation channels in cardiomyocytes might deliver a depolarizing force sufficient for defibrillation, thereby circumventing the aforementioned drawbacks. We therefore investigated the feasibility of light-induced spiral wave termination through cardiac optogenetics. METHODS AND RESULTS: Neonatal rat atrial cardiomyocyte monolayers were transduced with lentiviral vectors encoding light-activated Ca(2+)-translocating channelrhodopsin (CatCh; LV.CatChâ¼eYFP↑) or eYFP (LV.eYFP↑) as control, and burst-paced to induce spiral waves rotating around functional cores. Effects of CatCh activation on reentry were investigated by optical and multi-electrode array (MEA) mapping. Western blot analyses and immunocytology confirmed transgene expression. Brief blue light pulses (10 ms/470 nm) triggered action potentials only in LV.CatChâ¼eYFP↑-transduced cultures, confirming functional CatCh-mediated current. Prolonged light pulses (500 ms) resulted in reentry termination in 100% of LV.CatChâ¼eYFP↑-transduced cultures (n = 31) vs. 0% of LV.eYFP↑-transduced cultures (n = 11). Here, CatCh activation caused uniform depolarization, thereby decreasing overall excitability (MEA peak-to-peak amplitude decreased 251.3 ± 217.1 vs. 9.2 ± 9.5 µV in controls). Consequently, functional coresize increased and phase singularities (PSs) drifted, leading to reentry termination by PS-PS or PS-boundary collisions. CONCLUSION: This study shows that spiral waves in atrial cardiomyocyte monolayers can be terminated effectively by a light-induced depolarizing current, produced by the arrhythmogenic substrate itself, upon optogenetic engineering. These results provide proof-of-concept for shockless defibrillation.
Assuntos
Fibrilação Atrial/terapia , Luz , Miócitos Cardíacos/efeitos da radiação , Optogenética , Potenciais de Ação , Animais , Animais Recém-Nascidos , Fibrilação Atrial/genética , Fibrilação Atrial/metabolismo , Fibrilação Atrial/fisiopatologia , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Western Blotting , Estimulação Cardíaca Artificial , Células Cultivadas , Channelrhodopsins , Estudos de Viabilidade , Imunofluorescência , Vetores Genéticos , Átrios do Coração/metabolismo , Átrios do Coração/fisiopatologia , Átrios do Coração/efeitos da radiação , Lentivirus/genética , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Miócitos Cardíacos/metabolismo , Técnicas de Patch-Clamp , Ratos Wistar , Fatores de Tempo , Transdução Genética , Transfecção , Imagens com Corantes Sensíveis à VoltagemRESUMO
BACKGROUND: Atrial fibrillation is the most common cardiac arrhythmia. Ventricular proarrhythmia hinders pharmacological atrial fibrillation treatment. Modulation of atrium-specific Kir3.x channels, which generate a constitutively active current (I(K,ACh-c)) after atrial remodeling, might circumvent this problem. However, it is unknown whether and how I(K,ACh-c) contributes to atrial fibrillation induction, dynamics, and termination. Therefore, we investigated the effects of I(K,ACh-c) blockade and Kir3.x downregulation on atrial fibrillation. METHODS AND RESULTS: Neonatal rat atrial cardiomyocyte cultures and intact atria were burst paced to induce reentry. To study the effects of Kir3.x on action potential characteristics and propagation patterns, cultures were treated with tertiapin or transduced with lentiviral vectors encoding Kcnj3- or Kcnj5-specific shRNAs. Kir3.1 and Kir3.4 were expressed in atrial but not in ventricular cardiomyocyte cultures. Tertiapin prolonged action potential duration (APD; 54.7±24.0 to 128.8±16.9 milliseconds; P<0.0001) in atrial cultures during reentry, indicating the presence of I(K,ACh-c). Furthermore, tertiapin decreased rotor frequency (14.4±7.4 to 6.6±2.0 Hz; P<0.05) and complexity (6.6±7.7 to 0.6±0.8 phase singularities; P<0.0001). Knockdown of Kcnj3 or Kcnj5 gave similar results. Blockade of I(K,ACh-c) prevented/terminated reentry by prolonging APD and changing APD and conduction velocity restitution slopes, thereby altering the probability of APD alternans and rotor destabilization. Whole-heart mapping experiments confirmed key findings (e.g., >50% reduction in atrial fibrillation inducibility after I(K,ACh-c) blockade). CONCLUSIONS: Atrium-specific Kir3.x controls the induction, dynamics, and termination of fibrillation by modulating APD and APD/conduction velocity restitution slopes in atrial tissue with I(K,ACh-c). This study provides new molecular and mechanistic insights into atrial tachyarrhythmias and identifies Kir3.x as a promising atrium-specific target for antiarrhythmic strategies.
Assuntos
Fibrilação Atrial/fisiopatologia , Regulação para Baixo/fisiologia , Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/fisiologia , Átrios do Coração/fisiopatologia , Miócitos Cardíacos/fisiologia , Acetilcolina/farmacologia , Potenciais de Ação/efeitos dos fármacos , Potenciais de Ação/fisiologia , Animais , Venenos de Abelha/farmacologia , Células Cultivadas , Modelos Animais de Doenças , Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/efeitos dos fármacos , Átrios do Coração/efeitos dos fármacos , Miócitos Cardíacos/citologia , Miócitos Cardíacos/efeitos dos fármacos , Ratos , Ratos Wistar , Fatores de Tempo , Imagens com Corantes Sensíveis à VoltagemRESUMO
AIMS: Cardiac hypertrophy and fibrosis are associated with potentially lethal arrhythmias. As these substrates often occur simultaneously in one patient, distinguishing between pro-arrhythmic mechanisms is difficult. This hampers understanding of underlying pro-arrhythmic mechanisms and optimal treatment. This study investigates and compares arrhythmogeneity and underlying pro-arrhythmic mechanisms of either cardiac hypertrophy or fibrosis in in vitro models. METHODS AND RESULTS: Fibrosis was mimicked by free myofibroblast (MFB) proliferation in neonatal rat ventricular monolayers. Cultures with inhibited MFB proliferation were used as control or exposed to phenylephrine to induce hypertrophy. At Day 9, cultures were studied with patch-clamp and optical-mapping techniques and assessed for protein expression. In hypertrophic (n = 111) and fibrotic cultures (n = 107), conduction and repolarization were slowed. Triggered activity was commonly found in these substrates and led to high incidences of spontaneous re-entrant arrhythmias [67.5% hypertrophic, 78.5% fibrotic vs. 2.9% in controls (n = 102)] or focal arrhythmias (39.1, 51.7 vs. 8.8%, respectively). Kv4.3 and Cx43 protein expression levels were decreased in hypertrophy but unaffected in fibrosis. Depolarization of cardiomyocytes (CMCs) was only found in fibrotic cultures (-48 ± 7 vs. -66 ± 7 mV in control, P < 0.001). L-type calcium-channel blockade prevented arrhythmias in hypertrophy, but caused conduction block in fibrosis. Targeting heterocellular coupling by low doses of gap-junction uncouplers prevented arrhythmias by accelerating repolarization only in fibrotic cultures. CONCLUSION: Cultured hypertrophic or fibrotic myocardial tissues generated similar focal and re-entrant arrhythmias. These models revealed electrical remodelling of CMCs as a pro-arrhythmic mechanism of hypertrophy and MFB-induced depolarization of CMCs as a pro-arrhythmic mechanism of fibrosis. These findings provide novel mechanistic insight into substrate-specific arrhythmicity.
Assuntos
Arritmias Cardíacas/etiologia , Cardiomegalia/complicações , Miócitos Cardíacos/metabolismo , Potenciais de Ação , Animais , Animais Recém-Nascidos , Antiarrítmicos/farmacologia , Arritmias Cardíacas/metabolismo , Arritmias Cardíacas/patologia , Arritmias Cardíacas/fisiopatologia , Arritmias Cardíacas/prevenção & controle , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio Tipo L/efeitos dos fármacos , Canais de Cálcio Tipo L/metabolismo , Cardiomegalia/metabolismo , Cardiomegalia/patologia , Cardiomegalia/fisiopatologia , Células Cultivadas , Técnicas de Cocultura , Conexina 43/metabolismo , Fibroblastos/metabolismo , Fibroblastos/patologia , Fibrose , Junções Comunicantes/efeitos dos fármacos , Junções Comunicantes/metabolismo , Cinética , Miócitos Cardíacos/efeitos dos fármacos , Miócitos Cardíacos/patologia , Técnicas de Patch-Clamp , Fenilefrina/farmacologia , Ratos , Canais de Potássio Shal/metabolismo , Imagens com Corantes Sensíveis à VoltagemRESUMO
AIMS: Sustained ventricular fibrillation (VF) is maintained by multiple stable rotors. Destabilization of sustained VF could be beneficial by affecting VF complexity (defined by the number of rotors). However, underlying mechanisms affecting VF stability are poorly understood. Therefore, the aim of this study was to correlate changes in arrhythmia complexity with changes in specific electrophysiological parameters, allowing a search for novel factors and underlying mechanisms affecting stability of sustained VF. METHODS AND RESULTS: Neonatal rat ventricular cardiomyocyte monolayers and Langendorff-perfused adult rat hearts were exposed to increasing dosages of the gap junctional uncoupler 2-aminoethoxydiphenyl borate (2-APB) to induce arrhythmias. Ion channel blockers/openers were added to study effects on VF stability. Electrophysiological parameters were assessed by optical mapping and patch-clamp techniques. Arrhythmia complexity in cardiomyocyte cultures increased with increasing dosages of 2-APB (n > 38), leading to sustained VF: 0.0 ± 0.1 phase singularities/cm(2) in controls vs. 0.0 ± 0.1, 1.0 ± 0.9, 3.3 ± 3.2, 11.0 ± 10.1, and 54.3 ± 21.7 in 5, 10, 15, 20, and 25 µmol/L 2-APB, respectively. Arrhythmia complexity inversely correlated with wavelength. Lengthening of wavelength during fibrillation could only be induced by agents (BaCl(2)/BayK8644) increasing the action potential duration (APD) at maximal activation frequencies (minimal APD); 123 ± 32%/117 ± 24% of control. Minimal APD prolongation led to transient VF destabilization, shown by critical wavefront collision leading to rotor termination, followed by significant decreases in VF complexity and activation frequency (52%/37%). These key findings were reproduced ex vivo in rat hearts (n = 6 per group). CONCLUSION: These results show that stability of sustained fibrillation is regulated by minimal APD. Minimal APD prolongation leads to transient destabilization of fibrillation, ultimately decreasing VF complexity, thereby providing novel insights into anti-fibrillatory mechanisms.
Assuntos
Potenciais de Ação , Junções Comunicantes/metabolismo , Miócitos Cardíacos/metabolismo , Fibrilação Ventricular/metabolismo , Potenciais de Ação/efeitos dos fármacos , Animais , Animais Recém-Nascidos , Compostos de Boro/toxicidade , Células Cultivadas , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Junções Comunicantes/efeitos dos fármacos , Canais Iônicos/efeitos dos fármacos , Canais Iônicos/metabolismo , Cinética , Moduladores de Transporte de Membrana/toxicidade , Miócitos Cardíacos/efeitos dos fármacos , Técnicas de Patch-Clamp , Perfusão , Ratos , Fibrilação Ventricular/induzido quimicamente , Fibrilação Ventricular/fisiopatologia , Imagens com Corantes Sensíveis à VoltagemRESUMO
AIMS: Arrhythmogenesis in cardiac fibrosis remains incompletely understood. Therefore, this study aims to investigate how heterocellular coupling between cardiomyocytes (CMCs) and myofibroblasts (MFBs) affects arrhythmogeneity of fibrotic myocardial cultures. Potentially, this may lead to the identification of novel anti-arrhythmic strategies. METHODS AND RESULTS: Co-cultures of neonatal rat CMCs and MFBs in a 1:1 ratio were used as a model of cardiac fibrosis, with purified CMC cultures as control. Arrhythmogeneity was studied at day 9 of culture by voltage-sensitive dye mapping. Heterocellular coupling was reduced by transducing MFBs with lentiviral vectors encoding shRNA targeting connexin43 (Cx43) or luciferase (pLuc) as control. In fibrotic cultures, conduction velocity (CV) was lowered (11.2 ± 1.6 cm/s vs. 23.9 ± 2.1 cm/s; P < 0.0001), while action potential duration and ectopic activity were increased. Maximal diastolic membrane potential (MDP) of CMCs was less negative in fibrotic cultures. In fibrotic cultures, (n = 30) 30.0% showed spontaneous re-entrant tachyarrhythmias compared with 5% in controls (n = 60). Cx43 silencing in MFBs made the MDP in CMCs more negative, increased excitability and CV by 51% (P < 0.001), and reduced action potential duration and ectopic activity (P < 0.01), thereby reducing re-entry incidence by 40% compared with pLuc-silenced controls. Anti-arrhythmic effects of Cx43 down-regulation in MFBs was reversed by depolarization of CMCs through I(k1) inhibition or increasing extracellular [K(+)]. CONCLUSION: Arrhythmogeneity of fibrotic myocardial cultures is mediated by Cx43 expression in MFBs. Reduced expression of Cx43 causes a more negative MDP of CMCs. This preserves CMC excitability, limits prolongation of repolarization and thereby strongly reduces the incidence of spontaneous re-entrant tachyarrhythmias.
Assuntos
Conexina 43/genética , Diástole/fisiologia , Terapia Genética/métodos , Miócitos Cardíacos/fisiologia , Taquicardia/prevenção & controle , Potenciais de Ação/fisiologia , Animais , Animais Recém-Nascidos , Conexina 43/metabolismo , Fibroblastos/patologia , Fibroblastos/fisiologia , Fibrose/patologia , Fibrose/fisiopatologia , Sistema de Condução Cardíaco/fisiologia , Lentivirus/genética , Miocárdio/patologia , Miócitos Cardíacos/patologia , Técnicas de Patch-Clamp , Cultura Primária de Células , RNA Interferente Pequeno/genética , Ratos , Ratos Wistar , Taquicardia/genética , Taquicardia/fisiopatologiaRESUMO
AIMS: Cardiac fibrosis is associated with increased incidence of cardiac arrhythmias, but the underlying proarrhythmic mechanisms remain incompletely understood and antiarrhythmic therapies are still suboptimal. This study tests the hypothesis that myofibroblast (MFB) proliferation leads to tachyarrhythmias by altering the excitability of cardiomyocytes (CMCs) and that inhibition of MFB proliferation would thus lower the incidence of such arrhythmias. METHODS AND RESULTS: Endogenous MFBs in neonatal rat CMC cultures proliferated freely or under control of different dosages of antiproliferative agents (mitomycin-C and paclitaxel). At Days 4 and 9, arrhythmogeneity of these cultures was studied by optical and multi-electrode mapping. Cultures were also studied for protein expression and electrophysiological properties. MFB proliferation slowed conduction from 15.3 ± 3.5 cm/s (Day 4) to 8.8 ± 0.3 cm/s (Day 9) (n = 75, P < 0.01), whereas MFB numbers increased to 37.4 ± 1.7 and 62.0 ± 2%. At Day 9, 81.3% of these cultures showed sustained spontaneous reentrant arrhythmias. However, only 2.6% of mitomycin-C-treated cultures (n = 76, P < 0.0001) showed tachyarrhythmias, and ectopic activity was decreased. Arrhythmia incidence was drug-dose dependent and strongly related to MFB proliferation. Paclitaxel treatment yielded similar results. CMCs were functionally coupled to MFBs and more depolarized in cultures with ongoing MFB proliferation in which only L-type Ca(2+)-channel blockade terminated 100% of reentrant arrhythmias, in contrast to Na(+) blockade (36%, n = 12). CONCLUSION: Proliferation of MFBs in myocardial cultures gives rise to spontaneous, sustained reentrant tachyarrhythmias. Antiproliferative treatment of such cultures prevents the occurrence of arrhythmias by limiting MFB-induced depolarization, conduction slowing, and ectopic activity. This study could provide a rationale for a new treatment option for cardiac arrhythmias.