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1.
Heart Rhythm ; 6(11): 1552-8, 2009 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-19786370

RESUMO

BACKGROUND: The vein of Marshall (VOM) is a left atrial (LA) vein that contains autonomic innervation and triggers of AF. Its location coincides with areas usually ablated during pulmonary vein (PV) antral isolation (PVAI). OBJECTIVE: This study sought to delineate the safety and ablative effects of ethanol infusion in the VOM during catheter ablation of atrial fibrillation (AF). METHODS: Patients undergoing PVAI (n = 14) gave consent for adjunctive VOM ethanol infusion. In 10 of 14 patients, the VOM was cannulated with an angioplasty wire and balloon. Echocardiographic contrast was injected in the VOM under echocardiographic monitoring. Two infusions of 100% ethanol (1 ml each) were delivered via the angioplasty balloon in the VOM. LA bipolar voltage maps were created before and after ethanol infusion. Radiofrequency ablation times required to isolate each PV and other procedural data were compared with those of 10 age-, sex-, AF type- and LA size-matched control subjects undergoing conventional PVAI. RESULTS: The VOM communicated with underlying myocardium, as shown by echocardiographic contrast passage into the LA. There were no acute complications related to VOM ethanol infusion, which led to the creation of a low-voltage area in the LA measuring 10.6 +/- 7.6 cm(2) and isolation of the left inferior PV in 4 of 10 patients. Radiofrequency ablation time required to achieve isolation of the left inferior PV was reduced (2.2 +/- 4 min vs. 11.4 +/- 10.3 min in control subjects, P <.05). CONCLUSION: VOM ethanol infusion is safe in humans, decreases radiofrequency ablation time in the left inferior PV, and may have a role as an adjunct to PVAI.


Assuntos
Fibrilação Atrial/tratamento farmacológico , Fibrilação Atrial/cirurgia , Circulação Coronária/efeitos dos fármacos , Etanol/administração & dosagem , Estudos de Casos e Controles , Ablação por Cateter , Terapia Combinada , Feminino , Átrios do Coração , Humanos , Infusões Intravenosas , Masculino , Pessoa de Meia-Idade , Resultado do Tratamento
2.
Circ Arrhythm Electrophysiol ; 2(1): 50-6, 2009 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-19756206

RESUMO

BACKGROUND: The vein of Marshall (VOM) is an attractive target during ablation of atrial fibrillation due to its autonomic innervation, its location anterior to the left pulmonary veins and drainage in the coronary sinus. METHODS AND RESULTS: We studied 17 dogs. A coronary sinus venogram showed a VOM in 13, which was successfully cannulated with an angioplasty wire and balloon. In 5 dogs, electroanatomical maps of the left atrium were performed at baseline and after ethanol infusion in the VOM, which demonstrated a new crescent-shaped scar, extending from the annular left atrium towards the posterior wall and left pulmonary veins. In 4 other dogs, effective refractory periods (ERP) were measured at 3 sites in the left atrium, before and after high-frequency bilateral vagal stimulation. The ERP decreased from 113.6+/-35.0 ms to 82.2+/-25.4 ms (p<0.05) after vagal stimulation. After VOM ethanol infusion, vagally-mediated ERP decrease was eliminated (from 108.6+/-24.1 ms to 96.4 +/-16.9ms, p=NS). The abolition of vagal effects was limited to sites near the VOM (ERP: 104+/-14 ms, vs 98.6+/-12.2 ms post vagal stimulation, p=ns), as opposed to sites remote to VOM (ERP: 107.2+/-14.9 ms, vs 78.6+/-14.7ms post vagal stimulation, p<0.05). To test feasibility in humans, 5 patients undergoing pulmonary vein antral isolation had successful VOM cannulation and ethanol infusion: left atrial voltage maps demonstrated new scar involving the infero-posterior left atrial wall extending towards the left pulmonary veins. CONCLUSIONS: Ethanol infusion in then VOM achieves significant left atrial tissue ablation, abolishes local vagal responses and is feasible in humans.


Assuntos
Fibrilação Atrial/terapia , Ablação por Cateter/métodos , Vasos Coronários , Etanol/administração & dosagem , Vagotomia/métodos , Animais , Fibrilação Atrial/patologia , Fibrilação Atrial/fisiopatologia , Cicatriz , Angiografia Coronária/métodos , Vasos Coronários/embriologia , Cães , Estudos de Viabilidade , Átrios do Coração/inervação , Átrios do Coração/patologia , Átrios do Coração/fisiopatologia , Humanos , Infusões Intravenosas , Flebografia , Resultado do Tratamento , Veia Cava Superior/embriologia
3.
J Am Soc Echocardiogr ; 22(9): 1040-6, 2009 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-19553079

RESUMO

BACKGROUND: This study was performed in both animals and human subjects to test whether different approaches to calculate untwisting rate may lead to different results in the assessment of left ventricular (LV) relaxation. METHODS: In animal experiments, congestive heart failure was successfully induced in 8 adult dogs. Transthoracic echocardiography was performed with simultaneous LV pressure recording at baseline and the stage of heart failure. In the clinical study, 72 patients undergoing right-sided heart catheterization were studied by transthoracic echocardiography. LV twist was calculated as the difference between apical and basal rotations measured using two-dimensional speckle tracking. Untwisting rate was calculated using 3 different algorithms as the peak negative time derivative of twist (UR(max)) during early diastole, the slope of the linear regression of untwisting over time (UR(slope)), or the average untwisting over the isovolumic relaxation period (UR(mean)). RESULTS: UR(max) significantly correlated with tau and -dP/dt in dogs (r=-0.81 and 0.77, respectively, both P < .001) and was reduced at the stage of heart failure (P < .01). In 55 patients (76%) with adequate image quality, only UR(max) among untwisting rates calculated by 3 different algorithms was significantly related to tau (r=-0.51, P < .001). UR(max) was significantly lower in patients with tau>/=48 ms than in patients with tau<48 ms (P=.004), most of whom had a depressed LV ejection fraction. CONCLUSION: UR(max) best reflects LV relaxation in comparison with the 2 other algorithms.


Assuntos
Algoritmos , Ecocardiografia/métodos , Ventrículos do Coração/diagnóstico por imagem , Interpretação de Imagem Assistida por Computador/métodos , Disfunção Ventricular Esquerda/diagnóstico por imagem , Animais , Cães , Feminino , Humanos , Aumento da Imagem/métodos , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
4.
IEEE Trans Biomed Eng ; 56(2): 416-25, 2009 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-19272903

RESUMO

Intracardiac echocardiography (ICE) has proven to be useful for online anatomical imaging during catheterization. Our objective was to develop a speckle tracking method for myocardial motion estimation from ICE image sequences in order to provide a mean for regional functional imaging. Our approach was to solve two problems in motion estimation from 2-D ICE image sequences: nonrigid myocardial deformation and speckle decorrelation. To achieve robust noise resistance, we employed maximum likelihood estimation while fully exploiting ultrasound speckle statistics, and treated the maximization of motion probability as the minimization of an energy function. Nonrigid myocardial deformation was estimated by optimizing this energy function within a framework of parametric elastic registration. Evaluation of the method was carried out using a computer model that synthesized echocardiographic image sequences, and subsequently an animal model that provided continuous ICE images as well as reference measurements using sonomicrometry crystals. In conclusion, accurate estimation of regional myocardial deformation from ICE by novel speckle tracking is feasible. This approach may have important clinical implications for multimodal imaging during catheterization.


Assuntos
Ecocardiografia/métodos , Técnicas Eletrofisiológicas Cardíacas , Coração/fisiologia , Modelos Cardiovasculares , Processamento de Sinais Assistido por Computador , Algoritmos , Animais , Simulação por Computador , Cães , Técnicas de Imagem por Elasticidade , Eletrocardiografia , Modelos Animais , Modelos Estatísticos , Miocárdio , Reprodutibilidade dos Testes
5.
J Am Coll Cardiol ; 53(12): 1075-81, 2009 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-19298923

RESUMO

OBJECTIVES: This study was designed to investigate the properties of multiple bioelectric impedance signals recorded during congestive heart failure (CHF) by utilizing various electrode configurations of an implanted cardiac resynchronization therapy system. BACKGROUND: The monitoring of CHF has relied mainly on right-side heart sensors. METHODS: Fifteen normal dogs underwent implantation of cardiac resynchronization therapy systems using standard leads. An additional left atrial (LA) pressure lead sensor was implanted in 5 dogs. Continuous rapid right ventricular (RV) pacing was applied over several weeks. Left ventricular (LV) catheterization and echocardiography were performed biweekly. Six steady-state impedance signals, utilizing intrathoracic and intracardiac vectors, were measured through ring (r), coil (c), and device Can electrodes. RESULTS: Congestive heart failure developed in all animals after 2 to 4 weeks of pacing. Impedance diminished gradually during CHF induction, but at varying rates for different vectors. Impedance during CHF decreased significantly in all measured vectors: LV(r)-Can, -17%; LV(r)-RV(r), -15%; LV(r)-RA(r), -11%; RV(r)-Can, -12%; RV(c)-Can, -7%; and RA(r)-Can, -5%. The LV(r)-Can vector reflected both the fastest and largest change in impedance in comparison with vectors employing only right-side heart electrodes, and was highly reflective of changes in LV end-diastolic volume and LA pressure. CONCLUSIONS: Impedance, acquired by different lead electrodes, has variable responses to CHF. Impedance vectors employing an LV lead are highly responsive to physiologic changes during CHF. Measuring multiple impedance signals could be useful for optimizing ambulatory monitoring in heart failure patients.


Assuntos
Insuficiência Cardíaca/diagnóstico , Monitorização Ambulatorial , Animais , Modelos Animais de Doenças , Cães , Impedância Elétrica , Eletrodos Implantados , Insuficiência Cardíaca/fisiopatologia , Hemodinâmica , Marca-Passo Artificial , Função Ventricular Direita
6.
J Am Soc Echocardiogr ; 22(1): 95-8, 2009 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19131008

RESUMO

BACKGROUND: Left ventricular (LV) twist dynamics play an important role in LV systolic and diastolic function. The aim of this preliminary study was to investigate LV twist dynamics in a canine model of reversible congestive heart failure (CHF). METHODS: Pacing systems were implanted in adult dogs, and continuous chronic right ventricular pacing (230-250 beats/min) was applied until CHF induction. Pacing was then stopped to allow the heart to recover. Echocardiography and LV catheterization were performed at baseline, during CHF while pacing was temporarily switched off, and during recovery. LV twist was computed as the difference between apical and basal rotation measured using 2-dimensional speckle tracking. Torsion was further calculated as LV twist divided by the LV long axis. The untwisting rate was computed as the peak diastolic time derivative of twist. RESULTS: In 6 dogs that completed the study, we found that CHF developed after 2 to 4 weeks of pacing, with LV end-diastolic volume, end-systolic volume, end-diastolic pressure, and the time constant of relaxation during isovolumic relaxation period (tau) all increasing significantly compared with baseline and recovering to normal levels 2 to 4 weeks after pacing was stopped. LV twist, torsion, and untwisting rate decreased significantly with CHF compared with baseline and improved during recovery from CHF. CONCLUSION: LV twist dynamics reflect pacing-induced CHF and its reversal as assessed by echocardiographic speckle tracking.


Assuntos
Insuficiência Cardíaca/diagnóstico por imagem , Insuficiência Cardíaca/fisiopatologia , Ventrículos do Coração/diagnóstico por imagem , Ventrículos do Coração/fisiopatologia , Contração Miocárdica , Disfunção Ventricular Esquerda/diagnóstico por imagem , Disfunção Ventricular Esquerda/fisiopatologia , Animais , Cães , Masculino , Projetos Piloto , Rotação , Torção Mecânica , Ultrassonografia
7.
Eur Heart J ; 29(10): 1283-9, 2008 May.
Artigo em Inglês | MEDLINE | ID: mdl-18385117

RESUMO

AIMS: To examine myocardial deformation and rotation in patients with heart failure, and elucidate the underlying mechanisms that account for normal ejection fraction (EF) in patients with diastolic heart failure (DHF). METHODS AND RESULTS: Fifty consecutive patients presenting with congestive heart failure (age: 58 +/- 16 years) underwent simultaneous right heart catheterization and transthoracic echocardiography. Left ventricular (LV) volumes, mass, EF, meridional, and circumferential wall stress were measured in addition to haemodynamic measurements. 2-D speckle tracking was applied to measure longitudinal, radial, and circumferential strain and twist. Twist was reduced only in patients with systolic heart failure (SHF: 5 +/- 2 degrees, DHF: 13 +/- 6 degrees, control: 14 +/- 5 degrees, P < 0.001). Circumferential strain was not different between DHF (-15 +/- 5%) and control groups (-20 +/- 3%, P > 0.05), though it was significantly lower in patients with SHF (-7 +/- 3%, P < 0.05). Importantly, longitudinal (DHF:-12%, SHF: -4%, control: -19%, P < 0.001) and radial (DHF: 28 +/- 9%, SHF: 14 +/- 8%, control: 47 +/- 7%, P < 0.001) strains were significantly lower in both heart failure groups than in controls, and were depressed to a larger extent in SHF patients than in those with DHF (both P < 0.05). CONCLUSION: LV longitudinal and radial strains are reduced, but circumferential deformation and twist are normal in DHF patients. On the other hand, in patients with SHF, longitudinal, radial, and circumferential deformation, and twist are all reduced. Multivariable regression analysis suggests that preserved LV twist and circumferential strain may contribute to normal EF in patients with DHF.


Assuntos
Insuficiência Cardíaca Diastólica/fisiopatologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Caracteres Sexuais , Estresse Mecânico , Volume Sistólico/fisiologia , Função Ventricular
8.
J Am Coll Cardiol ; 51(6): 651-9, 2008 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-18261685

RESUMO

OBJECTIVES: The aim of this study was to validate a novel, angle-independent, feature-tracking method for the echocardiographic quantitation of regional function. BACKGROUND: A new echocardiographic method, Velocity Vector Imaging (VVI) (syngo Velocity Vector Imaging technology, Siemens Medical Solutions, Ultrasound Division, Mountain View, California), has been introduced, based on feature tracking-incorporating speckle and endocardial border tracking, that allows the quantitation of endocardial strain, strain rate (SR), and velocity. METHODS: Seven dogs were studied during baseline, and various interventions causing alterations in regional function: dobutamine, 5-min coronary occlusion with reperfusion up to 1 h, followed by dobutamine and esmolol infusions. Echocardiographic images were acquired from short- and long-axis views of the left ventricle. Segment-length sonomicrometry crystals were used as the reference method. RESULTS: Changes in systolic strain in ischemic segments were tracked well with VVI during the different states of regional function. There was a good correlation between circumferential and longitudinal systolic strain by VVI and sonomicrometry (r = 0.88 and r = 0.83, respectively, p < 0.001). Strain measurements in the nonischemic basal segments also demonstrated a significant correlation between the 2 methods (r = 0.65, p < 0.001). Similarly, a significant relation was observed for circumferential and longitudinal SR between the 2 methods (r = 0.94, p < 0.001 and r = 0.90, p < 0.001, respectively). The endocardial velocity relation to changes in strain by sonomicrometry was weaker owing to significant cardiac translation. CONCLUSIONS: Velocity Vector Imaging, a new feature-tracking method, can accurately assess regional myocardial function at the endocardial level and is a promising clinical tool for the simultaneous quantification of regional and global myocardial function.


Assuntos
Vasos Coronários/fisiopatologia , Isquemia Miocárdica/fisiopatologia , Reperfusão Miocárdica , Miocárdio , Animais , Velocidade do Fluxo Sanguíneo , Vasos Coronários/diagnóstico por imagem , Dobutamina , Cães , Endocárdio , Feminino , Masculino , Modelos Animais , Isquemia Miocárdica/diagnóstico por imagem , Propanolaminas , Sístole , Ultrassonografia
9.
Am J Physiol Heart Circ Physiol ; 294(2): H1002-9, 2008 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-18083892

RESUMO

Multiple imaging modalities are employed independent of one another while managing complex cardiac arrhythmias. To combine electrical, anatomical, and functional imaging in a single catheter system, we developed a balloon catheter that carried 64 electrodes on its surface and an intracardiac echocardiography (ICE) catheter through a central lumen. The catheter system was inserted, and the balloon was inflated inside the left ventricle (LV) of eight dogs with 6-wk-old infarction, created by occlusion in the left anterior descending coronary artery. Anatomy was constructed by ICE imaging (9 MHz) through the balloon. Single-beat noncontact mapping (NCM) was performed via the multielectrode array to reconstruct unipolar endocardial electrograms during sinus rhythm. Standard contact mapping (CM) of the endocardium was also carried out for reference. Myocardial infarction in anterior LV extending from the middle to apical regions was localized both by ICE and NCM and validated by CM and pathology. The overall difference in the activation times between NCM and CM was 3 +/- 1 ms. Unipolar voltage in infarcted middle anterior LV was smaller than the voltage in normal middle inferior LV both by NCM (11 +/- 4 vs. 16 +/- 3 mV; P = 0.002) and CM (11 +/- 3 vs. 20 +/- 4 mV; P < 0.001). Unipolar voltage was also inversely related to infarct transmurality, both by NCM (r = -0.87; P = 0.005) and CM (r = -0.94; P < 0.001). The infarct area by ICE (7.7 +/- 2.9 cm(2)) was in agreement with CM (bipolar voltage, <1 mV; and area, 7.6 +/- 3.3 cm(2); r = 0.80; P = 0.016). Meanwhile, the voltage threshold that depicted the infarct area by NCM was directly related to the smallest unipolar voltage reconstructed within the infarct (r = 0.96; P < 0.001). In conclusion, combining NCM and ICE imaging in a single catheter system is feasible. The preclinical development of such an integrated system and its evaluation in experimental myocardial infarction demonstrate capabilities for single-beat mapping at multiple sites as well as the online assessment of anatomy and myocardial function.


Assuntos
Cateterismo Cardíaco/instrumentação , Coração/anatomia & histologia , Coração/fisiologia , Animais , Interpretação Estatística de Dados , Cães , Ecocardiografia , Eletrocardiografia , Eletrofisiologia , Endocárdio/anatomia & histologia , Endocárdio/diagnóstico por imagem , Endocárdio/fisiologia , Testes de Função Cardíaca , Ventrículos do Coração , Infarto do Miocárdio/fisiopatologia , Taquicardia Ventricular/fisiopatologia , Função Ventricular Esquerda/fisiologia
10.
Artigo em Inglês | MEDLINE | ID: mdl-19162728

RESUMO

Electrical impedance tomography (EIT) detects tissue composition inside a medium by determining its resistive properties, and uses various electrode configurations to pass a small electric current and measure corresponding potential. We investigated the feasibility of reconstructing scarred tissue inside the heart wall by employing EIT on the basis of a catheter carrying a plurality of electrodes and placed inside the blood-filled heart cavity. We built a computer model of the biological medium, and reconstructed the resistivity distribution using the finite element method and Tikhonov regularization. The results established the successful implementation of the numeric methods and the possibility of localizing and quantifying scarred myocardium. Novel application of EIT from inside the heart cavity could be useful during catheterization and may complement other diagnostic modalities. Further research is necessary to assess the impact of several factors on the accuracy of the reconstruction and include number of electrodes, catheter location, and scar size.


Assuntos
Mapeamento Potencial de Superfície Corporal/métodos , Diagnóstico por Computador/métodos , Impedância Elétrica , Modelos Cardiovasculares , Infarto do Miocárdio/diagnóstico , Pletismografia de Impedância/métodos , Tomografia/métodos , Simulação por Computador , Humanos
11.
Circulation ; 116(22): 2580-6, 2007 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-17998458

RESUMO

BACKGROUND: Recent studies validated the measurement of left ventricular (LV) untwisting rate (UR) by speckle tracking echocardiography. A few reports suggest that it may provide additional noninvasive insight into LV diastolic function. METHODS AND RESULTS: Simultaneous echocardiographic imaging and LV pressure measurements (7F Millar catheters) were performed in 8 adult dogs. Loading conditions were altered by caval occlusion, whereas lusitropic state was changed by dobutamine and esmolol infusion. Inferior vena cava occlusion at all experimental stages (baseline, dobutamine, esmolol) led to a significant decrease (P < or = 0.01) in LV end-systolic volume (ESV) and a significant increase in UR (P = 0.03). The best relation was observed between LV UR and ESV (r = -0.8, P < 0.001). The clinical study was conducted in 67 patients (age 57+/-17 years, 19 women) undergoing simultaneous right heart catheterization and echocardiographic imaging, with 20 healthy subjects as a control group. There were 34 patients with ejection fraction (EF) <50% (25+/-9%), and 33 patients with normal EF and diastolic dysfunction (64+/-7%). Patients with LV systolic dysfunction had a significantly lower UR (-55 omicron/s) in comparison with the control group (-89 omicron/s) and patients with normal EF (-104 omicron/s, P < 0.05), and the determinants of LV UR were twist, ESV, and tau (r2 = 0.83, P < 0.001). In patients with diastolic dysfunction and normal EF, twist and ESV were the independent predictors (r2 = 0.71, P < 0.001). CONCLUSIONS: LV UR is reduced in patients with depressed EF, but not in those with diastolic dysfunction and normal EF, and is primarily determined by twist and ESV.


Assuntos
Ecocardiografia/métodos , Volume Sistólico , Disfunção Ventricular Esquerda/patologia , Adulto , Idoso , Animais , Estudos de Casos e Controles , Cães , Feminino , Insuficiência Cardíaca Diastólica , Humanos , Masculino , Pessoa de Meia-Idade , Pressão Ventricular
12.
Circulation ; 115(11): 1376-83, 2007 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-17339549

RESUMO

BACKGROUND: Diastolic strain rate (SR) measurements that comprise all left ventricular (LV) segments are advantageous over myocardial velocity for assessment of diastolic function. Mitral early diastolic velocity (E)/SR ratio during the isovolumetric relaxation (IVR) period can be used to estimate LV filling pressures. METHODS AND RESULTS: Simultaneous echocardiographic imaging and LV pressure measurements (7F catheters) were performed in 7 adult dogs. Loading conditions were altered by saline infusion and caval occlusion, and lusitropic state was changed by dobutamine and esmolol infusion. A curve depicting global SR was derived from each of the 3 apical views, and SR was measured during IVR (SR(IVR)) and early LV filling (SR(E)). SR(IVR) had a strong correlation with time constant of LV pressure decay during the IVR period (tau) (r=-0.83, P<0.001), whereas SR(E) was significantly related to LV end-diastolic pressure (r=0.52, P=0.005) in the experimental stages where tau was <40 ms. In 50 patients with simultaneous right heart catheterization and echocardiographic imaging, mitral E/SR(IVR) ratio had the best correlation with mean wedge pressure (r=0.79, P<0.001), as well as in 24 prospective patients (r=0.84, P=0.001). E/SR(IVR) was most useful in patients with ratio of E to mitral annulus early diastolic velocity (E/Ea ratio) 8 to 15 and was more accurate than E/Ea in patients with normal ejection fraction and regional dysfunction (both P<0.01). CONCLUSIONS: Global SR(IVR) by 2-dimensional speckle tracking is strongly dependent on LV relaxation. E/SR(IVR) can predict LV filling pressures with reasonable accuracy, particularly in patients with normal ejection fraction and in those with regional dysfunction.


Assuntos
Diástole/fisiologia , Ecocardiografia Doppler/métodos , Insuficiência Cardíaca/diagnóstico por imagem , Função Ventricular Esquerda/fisiologia , Pressão Ventricular/fisiologia , Antagonistas Adrenérgicos beta/farmacologia , Adulto , Idoso , Aminoglicosídeos , Animais , Cateterismo Cardíaco , Cardiotônicos/farmacologia , Diástole/efeitos dos fármacos , Dobutamina/farmacologia , Cães , Enedi-Inos , Feminino , Insuficiência Cardíaca/fisiopatologia , Frequência Cardíaca , Humanos , Masculino , Pessoa de Meia-Idade , Valva Mitral/fisiologia , Modelos Cardiovasculares , Valor Preditivo dos Testes , Propanolaminas/farmacologia , Pressão Propulsora Pulmonar , Função Ventricular Esquerda/efeitos dos fármacos , Pressão Ventricular/efeitos dos fármacos
13.
Am J Physiol Heart Circ Physiol ; 292(3): H1561-7, 2007 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-17122196

RESUMO

Atrial arrhythmias, primarily atrial fibrillation, have been independently associated with structural remodeling and with inflammation. We hypothesized that sustained inflammatory signaling by tumor necrosis factor (TNF) would lead to alterations both in underlying atrial myocardial structure and in atrial electrical conduction. We performed ECG recording, intracardiac electrophysiology studies, epicardial mapping, and connexin immunohistochemical analyses on transgenic mice with targeted overexpression of TNF in the cardiac compartment (MHCsTNF) and on wild-type (WT) control mice (age 8-16 wk). Atrial and ventricular conduction abnormalities were always evident on ECG in MHCsTNF mice, including a shortened atrioventricular interval with a wide QRS duration secondary to junctional rhythm. Supraventricular arrhythmias were observed in five of eight MHCsTNF mice, whereas none of the mice demonstrated ventricular arrhythmias. No arrhythmias were observed in WT mice. Left ventricular conduction velocity during apical pacing was similar between the two mouse groups. Connexin40 was significantly downregulated in MHCsTNF mice. In contrast, connexin43 density was not significantly altered in MHCsTNF mice, but rather dispersed away from the intercalated disks. In conclusion, sustained inflammatory signaling contributed to atrial structural remodeling and downregulation of connexin40 that was associated with an increased prevalence of atrial arrhythmias.


Assuntos
Fibrilação Atrial/fisiopatologia , Conexinas/genética , Regulação da Expressão Gênica , Fator de Necrose Tumoral alfa/genética , Animais , Eletrocardiografia , Coração/fisiopatologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos ICR , Camundongos Transgênicos
14.
Proc Natl Acad Sci U S A ; 103(46): 17378-83, 2006 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-17085580

RESUMO

TGF-beta-activated kinase-1 (TAK1), also known as MAPKK kinase-7 (MAP3K7), is a candidate effector of multiple circuits in cardiac biology and disease. Here, we show that inhibition of TAK1 in mice by a cardiac-specific dominant-negative mutation evokes electrophysiological and biochemical properties reminiscent of human Wolff-Parkinson-White syndrome, arising from mutations in AMP-activated protein kinase (AMPK), most notably, accelerated atrioventricular conduction and impaired AMPK activation. To test conclusively the biochemical connection from TAK1 to AMPK suggested by this phenotype, we disrupted TAK1 in mouse embryos and embryonic fibroblasts by Cre-mediated recombination. In TAK1-null embryos, the activating phosphorylation of AMPK at T172 was blocked, accompanied by defective AMPK activity. However, loss of endogenous TAK1 causes midgestation lethality, with defective yolk sac and intraembryonic vasculature. To preclude confounding lethal defects, we acutely ablated floxed TAK1 in culture by viral delivery of Cre. In culture, endogenous TAK1 was activated by oligomycin, the antidiabetic drug metformin, 5-aminoimidazole-4-carboxamide riboside (AICAR), and ischemia, well established triggers of AMPK activity. Loss of TAK1 in culture blocked T172 phosphorylation induced by all three agents, interfered with AMPK activation, impaired phosphorylation of the endogenous AMPK substrate acetyl CoA carboxylase, and also interfered with activation of the AMPK kinase LKB1. Thus, by disrupting the endogenous TAK1 locus, we prove a pivotal role for TAK1 in the LKB1/AMPK signaling axis, an essential governor of cell metabolism.


Assuntos
MAP Quinase Quinase Quinases/metabolismo , Complexos Multienzimáticos/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Transdução de Sinais , Proteínas Quinases Ativadas por AMP , Animais , Células Cultivadas , Ativação Enzimática , MAP Quinase Quinase Quinases/genética , Camundongos , Camundongos Transgênicos , Miocárdio/enzimologia , Fosforilação , Ligação Proteica , Ratos
15.
J Clin Invest ; 116(7): 2012-21, 2006 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-16823493

RESUMO

Arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVC) is a genetic disease caused by mutations in desmosomal proteins. The phenotypic hallmark of ARVC is fibroadipocytic replacement of cardiac myocytes, which is a unique phenotype with a yet-to-be-defined molecular mechanism. We established atrial myocyte cell lines expressing siRNA against desmoplakin (DP), responsible for human ARVC. We show suppression of DP expression leads to nuclear localization of the desmosomal protein plakoglobin and a 2-fold reduction in canonical Wnt/beta-catenin signaling through Tcf/Lef1 transcription factors. The ensuing phenotype is increased expression of adipogenic and fibrogenic genes and accumulation of fat droplets. We further show that cardiac-restricted deletion of Dsp, encoding DP, impairs cardiac morphogenesis and leads to high embryonic lethality in the homozygous state. Heterozygous DP-deficient mice exhibited excess adipocytes and fibrosis in the myocardium, increased myocyte apoptosis, cardiac dysfunction, and ventricular arrhythmias, thus recapitulating the phenotype of human ARVC. We believe our results provide for a novel molecular mechanism for the pathogenesis of ARVC and establish cardiac-restricted DP-deficient mice as a model for human ARVC. These findings could provide for the opportunity to identify new diagnostic markers and therapeutic targets in patients with ARVC.


Assuntos
Displasia Arritmogênica Ventricular Direita , Desmoplaquinas/metabolismo , Transdução de Sinais/fisiologia , Proteínas Wnt/metabolismo , beta Catenina/metabolismo , gama Catenina/metabolismo , Adipogenia/fisiologia , Animais , Displasia Arritmogênica Ventricular Direita/metabolismo , Displasia Arritmogênica Ventricular Direita/patologia , Núcleo Celular/metabolismo , Células Cultivadas , Desmoplaquinas/genética , Eletrofisiologia , Embrião de Mamíferos/anatomia & histologia , Embrião de Mamíferos/fisiologia , Átrios do Coração/citologia , Átrios do Coração/patologia , Humanos , Camundongos , Camundongos Knockout , Miócitos Cardíacos/citologia , Miócitos Cardíacos/fisiologia , Fenótipo , RNA Interferente Pequeno/genética , RNA Interferente Pequeno/metabolismo , Fatores de Transcrição TCF/metabolismo , Proteínas Wnt/genética , beta Catenina/genética , gama Catenina/genética
16.
Conf Proc IEEE Eng Med Biol Soc ; Suppl: 6689-92, 2006.
Artigo em Inglês | MEDLINE | ID: mdl-17959487

RESUMO

INTRODUCTION: The study tested the feasibility of differentiating radiofrequency ablation lesions from normal myocardium and quantifying their dimensions by myocardial contrast echocardiography (MCE). METHODS AND RESULTS: In 11 normal dogs, we created 14 focal and 4 linear lesions at different left ventricular sites.MCE was performed both before and after ablation by using an intracardiac echocardiography catheter (9 MHz)and infusing contrast microbubbles through the left coronary artery. An independent observer examined the lesion pathology. We found that intracardiac echocardiography alone could not delineate lesion dimensions. However, after ablation, MCE localized the lesions as well-defined, low-contrast areas within the normally opacified myocardium. Lesion dimensions byMCE immediately after ablation and 30 minutes later were similar. In 12 focal lesions, the average maximum depth (5.55 +/- 1.38 mm) and average maximum diameter(10.38 +/- 2.09 mm) by MCE were in excellent agreement with the pathologic depth (5.20 +/- 1.45 mm) and diameter(10.61 +/- 1.67 mm). Two focal lesions could not be detected by MCE and later were found to be superficial. Three-dimensional MCE correctly reconstructed the extent and shape of linear lesions compared to pathology (length: 18.7+/- 5.7 vs 18.5 +/- 5.6 mm; maximum longitudinal cross-sectional area: 81.2 +/- 9.6 vs 76.0 +/-10.3 mm(2)). CONCLUSION: MCE accurately localized and quantified radiofrequency ablation lesions in the normal leftv entricle. This new application of MCE may advance'ablation for managing ventricular arrhythmias that involve intramural or epicardial regions by providing instantaneous anatomic feedback on the effects of ablation during catheterization.


Assuntos
Ablação por Cateter/métodos , Ecocardiografia/métodos , Ventrículos do Coração/diagnóstico por imagem , Coração/fisiopatologia , Animais , Cães , Feminino , Sistema de Condução Cardíaco/fisiologia , Masculino , Miocárdio
17.
Am J Physiol Heart Circ Physiol ; 290(2): H724-31, 2006 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-16183729

RESUMO

We sought to assess the role of regional diastolic function by Doppler echocardiography in predicting myocardial viability. Sixteen dogs underwent left anterior descending coronary artery (n = 8) or circumflex (n = 8) occlusion. All animals were imaged at baseline and 1-8 wk postinfarction (post-MI). In 10 dogs, invasive hemodynamic monitoring with a conductance catheter placed in the left ventricle (LV) was performed at the above time points. Dobutamine was infused at 1-8 wk post-MI to determine LV contractile reserve. Histomorphological analysis was performed to determine the presence of viable myocardium and changes in interstitial matrix. Post-MI, diastolic strain rate measurements (in radial and longitudinal planes) decreased significantly in the distribution of the diseased artery (P < 0.01) and on multiple regression analysis were determined by time constant of LV relaxation, end-diastolic pressure, regional stiffness, and the ratio of cellular infiltration to collagen deposition in the interstitial matrix. Among several indexes, diastolic strain rate during dobutamine infusion readily identified segments with >20% transmural infarction and related best to the extent of interstitial fibrosis (r = -0.86, P < 0.01). In an animal model of healing canine infarcts, diastolic strain rate by Doppler echocardiography appears to be a promising novel index of myocardial viability.


Assuntos
Ecocardiografia , Coração/fisiopatologia , Infarto do Miocárdio/patologia , Infarto do Miocárdio/fisiopatologia , Sobrevivência de Tecidos , Animais , Cardiotônicos/farmacologia , Diástole , Dobutamina/farmacologia , Cães , Feminino , Coração/efeitos dos fármacos , Hemodinâmica , Masculino , Infarto do Miocárdio/diagnóstico por imagem , Miocárdio/patologia , Estresse Mecânico , Sístole , Fatores de Tempo
18.
J Appl Physiol (1985) ; 100(2): 679-84, 2006 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-16195393

RESUMO

We sought to examine the hemodynamic determinants and clinical application of the peak acceleration rate of early (Ea) diastolic velocity of the mitral annulus by tissue Doppler. Simultaneous left atrial and left ventricular (LV) catheterization and Doppler echocardiography were performed in 10 dogs. Preload was altered using volume infusion and caval occlusion, whereas myocardial lusitropic state was altered with dobutamine and esmolol. The clinical application was examined in 190 consecutive patients (55 control, 41 impaired relaxation, 46 pseudonormal, and 48 restrictive LV filling). In addition, in 60 consecutive patients, we examined the relation between it and mean wedge pressure with simultaneous Doppler echocardiography and right heart catheterization. In canine studies, a significant positive relation was present between peak acceleration rate of Ea and transmitral pressure gradient only in the stages with normal or enhanced LV relaxation, but with no relation in the stages where the time constant of LV relaxation (tau) was > or =50 ms. Its hemodynamic determinants were tau, LV minimal pressure, and transmitral pressure gradient. In clinical studies, peak acceleration rate of Ea was significantly lower in patients with impaired LV relaxation irrespective of filling pressures (P < 0.001) and with similar accuracy to peak Ea velocity (area under the curve for septal and lateral peak acceleration rates: both 0.78) in identifying these patients. No significant relation was observed between peak acceleration rate and mean wedge pressure. Peak acceleration rate of Ea appears to be a useful index of LV relaxation but not of filling pressures and can be applied to identify patients with impaired LV relaxation irrespective of their filling pressures.


Assuntos
Diástole , Valva Mitral/diagnóstico por imagem , Função Ventricular Esquerda , Animais , Velocidade do Fluxo Sanguíneo , Cães , Ecocardiografia Doppler/métodos , Humanos , Pessoa de Meia-Idade , Pressão Propulsora Pulmonar , Análise de Regressão , Fatores de Tempo , Pressão Ventricular
19.
J Cardiovasc Electrophysiol ; 16(8): 879-84, 2005 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-16101631

RESUMO

INTRODUCTION: Pulmonary vein (PV) isolation has proven to be an effective therapy for atrial fibrillation (AF). However, clinical evidence suggests that suppression of AF after PV isolation could not be fully attributed to the interruption of electrical conduction in and out of the PVs. Furthermore, little is known regarding the effects of ablation around the PVs on the atrial electrophysiological properties. We aimed to study the changes in atrial response to vagal stimulation (VS) after PV ablation (PVA). METHODS: We studied 11 adult mongrel dogs under general anesthesia. Bilateral cervical sympathovagal trunks were decentralized. Propranolol was given to block sympathetic effects. Multipolar catheters were placed into right atrial appendage (RAA), distal and proximal coronary sinus (CSD, CSP), and left atrial free wall (LAFW). PVA was performed via trans-septal approach. Atrial effective refractory period (AERP) and vulnerability window (VW) of AF were measured with and without VS before and after ablation to isolate the PVs. RESULTS: After ablation, AERP shortening in response to VS significantly decreased in the left atrium (43.64 +/- 21.57 vs 11.82 +/- 9.82 msec, P < 0.001 at LAFW; 50.91 +/- 26.25 vs 11.82 +/- 14.01 msec, P < 0.001 at CSP; 50 +/- 31.94 vs 17.27 +/- 20.54 msec, P < 0.005 at CSD), while the response to VS did not change significantly at RAA (58.18 +/- 28.22 vs 50.91 +/- 22.12 msec, P = 0.245). After ablation, atrial fibrillation VW during VS narrowed (20.63 +/- 11.48 vs 5.63 +/- 8.63 msec, P < 0.03 at LAFW; 26.25 +/- 12.46 vs 5.00 +/- 9.64 msec, P = 0.001 at CSP; 28.75 +/- 18.47 vs 6.88 +/- 7.53 msec, P < 0.02 at CSD, and 33.75 +/- 24.5 vs 16.25 +/- 9.91 msec, P = 0.03 at RAA). CONCLUSIONS: Ablation around the PV ostia diminishes left atrial response to VS and decreases the atrial VW. The attenuated vagal response after ablation may contribute to the suppression of AF.


Assuntos
Fibrilação Atrial/prevenção & controle , Ablação por Cateter/métodos , Átrios do Coração/inervação , Veias Pulmonares/cirurgia , Nervo Vago/fisiologia , Animais , Cães , Feminino , Átrios do Coração/fisiopatologia , Masculino , Período Refratário Eletrofisiológico
20.
Ultrasound Med Biol ; 31(1): 15-21, 2005 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-15653226

RESUMO

Cardiac function and hemodynamics are routinely evaluated during catheterization in patients with heart disease. Although intracardiac echocardiography (ICE) has been employed in guiding electrophysiology procedures, it has not been effectively used in assessing hemodynamics. We tested the utility of ICE in measuring left ventricular (LV) volume throughout the cardiac cycle. In four normal dogs (weight = 26 to 37 kg), a 10-F sheath was inserted through the femoral artery and placed inside the LV along its major axis. An ICE catheter (9 F, 9 MHz) was then inserted through the sheath into the LV. The ICE catheter was pulled back inside the sheath in 1-mm intervals starting from the apex, and 2-D tomographic images were continuously acquired while gating to respiration. Subsequently, the ICE catheter was replaced by a conductance catheter to measure single-beat volume signals. Stroke volume was determined by thermodilution for validation. All measurements were made in each dog while pacing the atrium at two different cycle lengths (range = 300 to 500 ms). The endocardial boundary was digitized from the ICE images throughout the cardiac cycle and LV volume was computed by integrating multiple segments along the major axis (range = 55 to 70 mm). We found that ICE accurately reconstructed LV 3-D anatomy. Stroke volume by ICE was in excellent agreement with thermodilution (error = 3.8 +/- 3.0%, r = 0.99, n = 8) and was highly reproducible. Morphology of LV volume signals correlated well with corresponding instantaneous volume signals derived by conductance (r = 0.93, n = 8). In conclusion, ICE accurately reconstructs LV anatomy and volume throughout the cardiac cycle in the normal heart. This approach could facilitate interventional diagnostic and therapeutic procedures.


Assuntos
Ecocardiografia Tridimensional/métodos , Função Ventricular Esquerda , Animais , Cateterismo Cardíaco , Débito Cardíaco , Cães , Condutividade Elétrica , Feminino , Ventrículos do Coração/anatomia & histologia , Ventrículos do Coração/diagnóstico por imagem , Hemodinâmica , Masculino , Variações Dependentes do Observador , Termodiluição/métodos
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