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BACKGROUND: In vivo characterization of mitral valve dynamics relies on image analysis algorithms that accurately reconstruct valve morphology and motion from clinical images. The goal of such algorithms is to provide patient-specific descriptions of both competent and regurgitant mitral valves, which can be used as input to biomechanical analyses and provide insights into the pathophysiology of diseases like ischemic mitral regurgitation (IMR). OBJECTIVE: The goal is to generate accurate image-based representations of valve dynamics that visually and quantitatively capture normal and pathological valve function. METHODS: We present a novel framework for 4D segmentation and geometric modeling of the mitral valve in real-time 3D echocardiography (rt-3DE), an imaging modality used for pre-operative surgical planning of mitral interventions. The framework integrates groupwise multi-atlas label fusion and template-based medial modeling with Kalman filtering to generate quantitatively descriptive and temporally consistent models of valve dynamics. RESULTS: The algorithm is evaluated on rt-3DE data series from 28 patients: 14 with normal mitral valve morphology and 14 with severe IMR. In these 28 data series that total 613 individual 3DE images, each 3D mitral valve segmentation is validated against manual tracing, and temporal consistency between segmentations is demonstrated. CONCLUSIONS: Automated 4D image analysis allows for reliable non-invasive modeling of the mitral valve over the cardiac cycle for comparison of annular and leaflet dynamics in pathological and normal mitral valves. Future studies can apply this algorithm to cardiovascular mechanics applications, including patient-specific strain estimation, fluid dynamics simulation, inverse finite element analysis, and risk stratification for surgical treatment.
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BACKGROUND: As the intracardiac flow field is affected by changes in shape and motility of the heart, intraventricular flow features can provide diagnostic indications. Ventricular flow patterns differ depending on the cardiac condition and the exploration of different clinical cases can provide insights into how flow fields alter in different pathologies. METHODS: In this study, we applied a patient-specific computational fluid dynamics model of the left ventricle and mitral valve, with prescribed moving boundaries based on transesophageal ultrasound images for three cardiac pathologies, to verify the abnormal flow patterns in impaired hearts. One case (P1) had normal ejection fraction but low stroke volume and cardiac output, P2 showed low stroke volume and reduced ejection fraction, P3 had a dilated ventricle and reduced ejection fraction. RESULTS: The shape of the ventricle and mitral valve, together with the pathology influence the flow field in the left ventricle, leading to distinct flow features. Of particular interest is the pattern of the vortex formation and evolution, influenced by the valvular orifice and the ventricular shape. The base-to-apex pressure difference of maximum 2mmHg is consistent with reported data. CONCLUSION: We used a CFD model with prescribed boundary motion to describe the intraventricular flow field in three patients with impaired diastolic function. The calculated intraventricular flow dynamics are consistent with the diagnostic patient records and highlight the differences between the different cases. The integration of clinical images and computational techniques, therefore, allows for a deeper investigation intraventricular hemodynamics in patho-physiology.
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Ventrículos do Coração/fisiopatologia , Simulação por Computador , Ecocardiografia Tridimensional , Ventrículos do Coração/diagnóstico por imagem , Hemodinâmica , Humanos , Valva Mitral/diagnóstico por imagem , Valva Mitral/fisiopatologia , Modelos CardiovascularesRESUMO
BACKGROUND: The goal of this paper is to present a computational fluid dynamic (CFD) model with moving boundaries to study the intraventricular flows in a patient-specific framework. Starting from the segmentation of real-time transesophageal echocardiographic images, a CFD model including the complete left ventricle and the moving 3D mitral valve was realized. Their motion, known as a function of time from the segmented ultrasound images, was imposed as a boundary condition in an Arbitrary Lagrangian-Eulerian framework. RESULTS: The model allowed for a realistic description of the displacement of the structures of interest and for an effective analysis of the intraventricular flows throughout the cardiac cycle. The model provides detailed intraventricular flow features, and highlights the importance of the 3D valve apparatus for the vortex dynamics and apical flow. CONCLUSIONS: The proposed method could describe the haemodynamics of the left ventricle during the cardiac cycle. The methodology might therefore be of particular importance in patient treatment planning to assess the impact of mitral valve treatment on intraventricular flow dynamics.
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Ventrículos do Coração/diagnóstico por imagem , Hemodinâmica , Hidrodinâmica , Imageamento Tridimensional , Modelagem Computacional Específica para o Paciente , Ultrassonografia , Função Ventricular , Humanos , Modelos CardiovascularesRESUMO
Comprehensive visual and quantitative analysis of in vivo human mitral valve morphology is central to the diagnosis and surgical treatment of mitral valve disease. Real-time 3D transesophageal echocardiography (3D TEE) is a practical, highly informative imaging modality for examining the mitral valve in a clinical setting. To facilitate visual and quantitative 3D TEE image analysis, we describe a fully automated method for segmenting the mitral leaflets in 3D TEE image data. The algorithm integrates complementary probabilistic segmentation and shape modeling techniques (multi-atlas joint label fusion and deformable modeling with continuous medial representation) to automatically generate 3D geometric models of the mitral leaflets from 3D TEE image data. These models are unique in that they establish a shape-based coordinate system on the valves of different subjects and represent the leaflets volumetrically, as structures with locally varying thickness. In this work, expert image analysis is the gold standard for evaluating automatic segmentation. Without any user interaction, we demonstrate that the automatic segmentation method accurately captures patient-specific leaflet geometry at both systole and diastole in 3D TEE data acquired from a mixed population of subjects with normal valve morphology and mitral valve disease.
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Inteligência Artificial , Ecocardiografia Tridimensional/métodos , Ecocardiografia Transesofagiana/métodos , Interpretação de Imagem Assistida por Computador/métodos , Valva Mitral/diagnóstico por imagem , Reconhecimento Automatizado de Padrão/métodos , Técnica de Subtração , Algoritmos , Humanos , Aumento da Imagem/métodos , Modelos Cardiovasculares , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
The course of cardiac remodeling after an acute cardiac MI, might affect the orientation of the cardiac muscle fibers as well as their contraction behavior. This may result in alteration of the untwisting during isovolumic relaxation phase, which might have effects on rapid early filling phase. In the present article, the variation of the time constant of isovolumic pressure drop (tau) has been studied during the course of cardiac remodeling after different types of induced myocardial infarction (MI) in sheep. The results for each group show different patterns of change in tau. The normalized tau curve in all three groups of anteroapical, anterobasal and posterobasal MI group show a rise 30 minutes after infarction. Two weeks later, the pressure drop constants decline to a lower level than baseline and by eight weeks after infarction, the time constant reached around the baseline level.
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OBJECTIVE: To examine the effect of an integrated surgical approach to the treatment of acute type A dissections. SUMMARY BACKGROUND DATA: Acute type A dissection requires surgery to prevent death from proximal aortic rupture or malperfusion. Most series of the past decade have reported a death rate in the range of 15% to 30%. METHODS: From January 1994 to March 2001, 104 consecutive patients underwent repair of acute type A dissection. All had an integrated operative management as follows: intraoperative transesophageal echocardiography; hypothermic circulatory arrest (HCA) with retrograde cerebral perfusion (RCP) to replace the aortic arch; HCA established after 5 minutes of electroencephalographic (EEG) silence in neuromonitored patients (66%) or after 45 minutes of cooling in patients who were not neuromonitored (34%); reinforcement of the residual arch tissue with a Teflon felt "neo-media"; cannulation of the arch graft to reestablish cardiopulmonary bypass at the completion of HCA (antegrade graft perfusion); and remodeling of the sinus of Valsalva segments with Teflon felt "neo-media" and aortic valve resuspension (78%) or replacement with a biologic or mechanical valved conduit (22%). RESULTS: Mean age was 59 +/- 15 (range 22-86) years, with 71% men and 13% redo sternotomy after a previous cardiac procedure. Mean cardiopulmonary bypass time was 196 +/- 50 minutes. Mean HCA with RCP time was 42 +/- 12 minutes (range 19-84). Mean cardiac ischemic time was 140 +/- 45 minutes. Eleven percent of patients presented with a preoperative neurologic deficit, and 5% developed a new cerebrovascular accident after dissection repair. The in-hospital death rate was 9%. Excluding the patients who presented neurologically unresponsive or with ongoing cardiopulmonary resuscitation (n = 5), the death rate was 4%. In six patients adverse cerebral outcomes were potentially avoided when immediate surgical fenestration was prompted by a sudden change in the EEG during cooling. Forty-five percent of neuromonitored patients required greater than 30 minutes to achieve EEG silence. CONCLUSION: The authors have shown that the surgical integration of sinus segment repair or aortic root replacement, the use of EEG monitoring, partial or total arch replacement using RCP, routine antegrade graft perfusion, and the uniform use of transesophageal echocardiography substantially decrease the death and complication rates of acute type A dissection repair.
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Aneurisma Aórtico/cirurgia , Dissecção Aórtica/cirurgia , Adulto , Idoso , Idoso de 80 Anos ou mais , Prótese Vascular , Ponte Cardiopulmonar , Ecocardiografia Transesofagiana , Eletroencefalografia , Feminino , Humanos , Hipotermia Induzida , Masculino , Pessoa de Meia-Idade , Monitorização Intraoperatória/métodos , Estudos RetrospectivosRESUMO
BACKGROUND: In patients with acute profound cardiogenic circulatory failure unresponsive to conventional resuscitation, we instituted immediate aggressive application of extracorporeal membrane oxygenation (ECMO) to restore circulatory stability. Long-term hemodynamic support was accomplished with an early "bridge" to ventricular assist device (VAD) before definitive treatment with cardiac transplantation. METHODS: A respective review of ECMO and VAD data registries was instituted. RESULTS: From May 1996 to July 2000, 23 patients were placed on ECMO support for profound cardiogenic circulatory failure. Eleven patients (47%) were withdrawn from support due to severe neurologic injury or multisystem organ failure. Three patients (13%) were weaned off ECMO with good outcome. Nine patients (39%) were transferred to a VAD. Two patients expired while on VAD support, and 7 of the VAD-supported patients (78%) survived to transplantation. Overall survival was 43%. CONCLUSIONS: Emergent ECMO support is a salvage approach for cardiac resuscitation once conventional measures have failed. In neurologically intact patients, the early transfer to a VAD quickly stabilizes hemodynamics, avoids complications, and is essential for long-term circulatory support before definitive treatment with cardiac transplantation.
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Reanimação Cardiopulmonar , Oxigenação por Membrana Extracorpórea , Transplante de Coração , Coração Auxiliar , Choque Cardiogênico/cirurgia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Mortalidade Hospitalar , Humanos , Masculino , Pessoa de Meia-Idade , Exame Neurológico , Sistema de Registros , Estudos Retrospectivos , Choque Cardiogênico/mortalidade , Taxa de Sobrevida , Resultado do TratamentoRESUMO
Retrograde cerebral perfusion with hypothermic circulatory arrest confers additional cerebral protection during repair of type A aortic dissection. We present a 42-year-old man with acute type A aortic dissection and a persistent, left superior vena cava. Cannulation of the right and left superior vena cava is used for retrograde perfusion of both hemispheres with bilateral monitoring of electroencephalogram and somatosensory-evoked potentials during and after the hypothermic circulatory arrest interval.
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Aneurisma da Aorta Torácica/cirurgia , Dissecção Aórtica/cirurgia , Isquemia Encefálica/prevenção & controle , Encéfalo/irrigação sanguínea , Parada Cardíaca Induzida , Complicações Intraoperatórias/prevenção & controle , Veia Cava Superior/cirurgia , Adulto , Eletroencefalografia , Potenciais Somatossensoriais Evocados/fisiologia , Humanos , Masculino , Monitorização Intraoperatória , Veia Cava Superior/anormalidadesAssuntos
Anticorpos Monoclonais/uso terapêutico , Fibrinolíticos/uso terapêutico , Fragmentos Fab das Imunoglobulinas/uso terapêutico , Infarto do Miocárdio/terapia , Inibidores da Agregação Plaquetária/uso terapêutico , Complexo Glicoproteico GPIIb-IIIa de Plaquetas/antagonistas & inibidores , Stents , Ativador de Plasminogênio Tecidual/uso terapêutico , Abciximab , Terapia Combinada , Humanos , Infarto do Miocárdio/mortalidade , Remodelação Ventricular/efeitos dos fármacosRESUMO
The objective of this article is to provide an orderly and concise approach to the treatment of the unstable cardiac surgery patient. The common causes of hemodynamic instability in this patient population are reviewed. The various pharmacologic, mechanical, and electric therapeutic options available for each clinical situation are explored, and a sequential treatment algorithm is developed.
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Baixo Débito Cardíaco/terapia , Procedimentos Cirúrgicos Cardíacos , Complicações Intraoperatórias/terapia , Complicações Pós-Operatórias/terapia , Choque/terapia , Circulação Assistida , Débito Cardíaco , Oxigenação por Membrana Extracorpórea , Hemodinâmica , Humanos , Contração MiocárdicaRESUMO
Mechanisms of bleeding common to virtually all patients after heart surgery are platelet dysfunction, enhanced fibrinolysis, dilution of all components of the coagulation system, and the presence of heparin and protamine. The use of warfarin is increasing in patients with heart disease requiring surgery. The replenishment of vitamin K-dependent factors beyond a normal prothrombin time is not assessable, and the dilution associated with cardiopulmonary bypass can reach coagulopathic levels. Optimal preoperative preparation is required and intraoperative therapy initiated when indicated. Individualized heparin and protamine dosing, antifibrinolytic drug administration, minimization of blood loss and dilution, and minimal time on cardiopulmonary bypass are basic adjuncts to meticulous surgical hemostasis. When bleeding is observed in the postoperative period, a sequential assessment of the probable cause leads to initial therapy while laboratory test results are obtained. Ongoing assessment for hemodynamic instability caused by accumulated mediastinal blood is needed while managing the bleeding patient. A chest radiograph and transesophageal echocardiogram can be useful in diagnosing cardiac tamponade.
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Perda Sanguínea Cirúrgica/prevenção & controle , Procedimentos Cirúrgicos Cardíacos , Hemostasia Cirúrgica , Hemostasia , Hemorragia Pós-Operatória/terapia , Algoritmos , Anticoagulantes/uso terapêutico , Ponte Cardiopulmonar , Humanos , Inibidores da Agregação Plaquetária/uso terapêutico , Medição de RiscoAssuntos
Transplante de Órgãos , Adulto , Órgãos Artificiais , Criança , Infecções por Citomegalovirus/etiologia , Rejeição de Enxerto , Acessibilidade aos Serviços de Saúde , Transplante de Coração/efeitos adversos , Coração Auxiliar , Hepatite B/etiologia , Hepatite C/etiologia , Teste de Histocompatibilidade , Humanos , Terapia de Imunossupressão , Transplante das Ilhotas Pancreáticas , Transplante de Rim/efeitos adversos , Transplante de Rim/imunologia , Transplante de Fígado/efeitos adversos , Transplante de Pulmão/efeitos adversos , Neoplasias/etiologia , Transplante de Pâncreas , Recidiva , Doadores de TecidosRESUMO
BACKGROUND: Large-volume hemoptysis during cardiopulmonary bypass is an infrequent, but life-threatening event. Rapid airway clearance and control are the primary prerequisites for successful management. METHODS: The cases of 3 patients with different sources of exsanguinating hemoptysis during cardiopulmonary bypass managed initially with rigid bronchoscopy were reviewed. RESULTS: In all patients, airway control was rapidly established and weaning from cardiopulmonary bypass CPB was accomplished. Two patients survived the operative procedure. The other patient died in the operating room of unremitting bilateral pulmonary hemorrhage. CONCLUSIONS: Major hemoptysis during cardiopulmonary bypass is best dealt with initially by rapid airway control and cessation of bypass in an expeditious manner. An algorithm for suggested management is provided. The rigid bronchoscope is the optimal tool for initial management and it should always be available. Definitive treatment is determined by the cause and the persistence of hemorrhage once these maneuvers have been performed.
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Ponte Cardiopulmonar , Hemoptise/terapia , Complicações Intraoperatórias/terapia , Idoso , Idoso de 80 Anos ou mais , Algoritmos , Broncoscopia , Pré-Escolar , Evolução Fatal , Feminino , Humanos , Pessoa de Meia-IdadeRESUMO
BACKGROUND: Expansion of an acute myocardial infarction predicts progressive left ventricular (LV) dilatation, functional deterioration, and early death. This study tests the hypothesis that restraining expansion of an acute infarction preserves LV geometry and resting function. METHODS AND RESULTS: In 23 sheep, snares were placed around the distal left anterior descending and second diagonal coronary arteries. In 12 sheep, infarct deformation was prevented by Marlex mesh placed over the anticipated myocardial infarct. Snared arteries were occluded 10 to 14 days later. Serial hemodynamic measurements and transdiaphragmatic quantitative echocardiograms were obtained up to 8 weeks after anteroapical infarction of 0.23 of LV mass. In sheep with mesh, circulatory hemodynamics, stroke work, and end-systolic elastance return to preinfarction values 1 week after infarction and do not change subsequently. Ventricular volumes and ejection fraction do not change after the first week postinfarction. Control animals develop large anteroapical ventricular aneurysms, increasing LV dilatation, and progressive deterioration in circulatory hemodynamics and ventricular function. At week 8, differences in LV end-diastolic pressure, cardiac output, end-diastolic and end-systolic volumes, ejection fraction, stroke work, and end-systolic elastance are significant (P<0.01) between groups. CONCLUSIONS: Preventing expansion of acute myocardial infarctions preserves LV geometry and function.
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Ventrículos do Coração/patologia , Infarto do Miocárdio/terapia , Função Ventricular Esquerda/fisiologia , Análise de Variância , Animais , Materiais Biocompatíveis , Progressão da Doença , Infarto do Miocárdio/patologia , Infarto do Miocárdio/fisiopatologia , Polietilenos , Polipropilenos , Ovinos , Telas CirúrgicasRESUMO
Although iron, vitamin B12, and folate deficiency have been well documented after gastric bypass operations performed for morbid obesity, there is surprisingly little information on either the natural course or the treatment of these deficiencies in Roux-en-Y gastric bypass (RYGB) patients. During a 10-year period, a complete blood count and serum levels of iron, total iron-binding capacity, vitamin B12, and folate were obtained in 348 patients preoperatively and postoperatively at 6-month intervals for the first 2 years, then annually thereafter. The principal objectives of this study were to determine how readily patients who developed metabolic deficiencies after Roux-en-Y gastric bypass responded to postoperative supplements of the deficient micronutrient and to learn whether the risk of developing these deficiencies decreases over time. Hemoglobin and hematocrit levels were significantly decreased at all postoperative intervals in comparison to preoperative values. Moreover, at each successive interval through 5 years, hemoglobin and hematocrit were decreased significantly compared to the preceding interval. Folate levels were significantly increased compared to preoperative levels at all time intervals. Iron and vitamin B12 levels were lower than preoperative measurements and remained relatively stable postoperatively. Half of the low hemoglobin levels were not associated with iron deficiency. Taking multivitamin supplements resulted in a lower incidence of folate deficiency but did not prevent iron or vitamin B12 deficiency. Oral supplementation of iron and vitamin B12 corrected deficiencies in 43% and 81% of cases, respectively. Folate deficiency was almost always corrected with multivitamins alone. No patient had symptoms that could be attributed to either vitamin B12 or folate deficiency Conversely, many patients had symptoms of iron deficiency and anemia. Lack of symptoms of vitamin B12 and folate deficiency suggests that these deficiencies are not clinically important after RYGB. Conversely, iron deficiency and anemia are potentially serious problems after RYGB, particularly in younger women. Hence we recommend prophylactic oral iron supplements to premenopausal women who undergo RYGB.
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Anastomose em-Y de Roux , Deficiência de Ácido Fólico/sangue , Derivação Gástrica , Deficiência de Vitamina B 12/sangue , Feminino , Ácido Fólico/sangue , Deficiência de Ácido Fólico/etiologia , Hematócrito , Hemoglobinas/análise , Humanos , Ferro/sangue , Complicações Pós-Operatórias , Fatores de Tempo , Vitamina B 12/sangue , Deficiência de Vitamina B 12/etiologia , Vitaminas/administração & dosagemRESUMO
An unusual presentation of a granular cell tumor is reported with a review of the natural history and pathologic characteristics of this tumor. Our patient was asymptomatic and presented with a mass in the inferior right neck on routine physical examination. Preoperative radiologic evaluation suggested a parathyroid adenoma but the normal parathormone level was inconsistent with this diagnosis. At surgery, a firm mass was identified inferior to the right lobe of the thyroid gland and was found to represent a granular cell tumor densely adherent to the trachea. This case demonstrates a unique presentation for this relatively rare neoplasm which was treated with complete surgical resection.
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Tumor de Células Granulares/diagnóstico , Neoplasias da Traqueia/diagnóstico , Adulto , Diagnóstico Diferencial , Feminino , Tumor de Células Granulares/diagnóstico por imagem , Tumor de Células Granulares/patologia , Tumor de Células Granulares/cirurgia , Humanos , Radioisótopos do Iodo , Cintilografia , Glândula Tireoide/diagnóstico por imagem , Neoplasias da Traqueia/diagnóstico por imagem , Neoplasias da Traqueia/patologia , Neoplasias da Traqueia/cirurgia , UltrassonografiaRESUMO
OBJECTIVE: To determine whether prophylactic oral iron supplements (320 mg twice daily) would protect women from iron deficiency and anemia after Roux-en-Y gastric bypass. DESIGN: Prospective, double-blind, randomized study in which 29 patients received oral iron and 27 patients received a placebo beginning 1 month after Roux-en-Y gastric bypass. SETTING: Tertiary care medical center. PATIENTS AND INTERVENTIONS: Complete blood cell count and serum levels of iron, total iron binding capacity, ferritin, vitamin B12, and folate were determined preoperatively and at 6-month intervals postoperatively in 56 menstruating women who had Roux-en-Y gastric bypass. MAIN OUTCOME MEASURE: Incidence of iron deficiency and other hematological abnormalities in each treatment group. RESULTS: Hemoglobin, hematocrit, and vitamin B12 levels were significantly decreased compared with preoperative values in both groups. Conversely, folate levels increased significantly over time in both groups. Oral iron consistently prevented development of iron deficiency in the iron group. Ferritin levels did not change significantly in the iron group. However, in placebo-treated patients, ferritin levels 2 years postoperatively were significantly decreased compared with preoperative levels. There was no difference in the incidence of anemia between the 2 groups. However, the incidence of microcytosis was substantially greater (P=.07) in placebo-treated than iron-treated patients. CONCLUSIONS: Prophylactic oral iron supplements successfully prevented iron deficiency in menstruating women after Roux-en-Y gastric bypass but did not consistently protect these women from developing anemia. On the basis of these results we now routinely recommend prophylactic iron supplements to menstruating women who have Roux-en-Y gastric bypass.
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Anemia Ferropriva/prevenção & controle , Derivação Gástrica/efeitos adversos , Deficiências de Ferro , Ferro/uso terapêutico , Adulto , Anastomose em-Y de Roux , Anemia Ferropriva/etiologia , Método Duplo-Cego , Feminino , Derivação Gástrica/métodos , Humanos , Pessoa de Meia-Idade , Estudos ProspectivosRESUMO
OBJECTIVE: This study tests the hypothesis that neither small nor large myocardial infarctions that include the anterior papillary muscle produce mitral regurgitation in sheep. METHODS: Coronary arterial anatomy to the anterior left ventricle and papillary muscle was determined by dye injection in 41 sheep hearts and by triphenyl tetrazolium chloride in 13. Development of acute or chronic mitral regurgitation and changes in left ventricular dimensions were studied by use of transdiaphragmatic echocardiography in 21 sheep after infarction of 24% and 33% of the anterior left ventricular mass. These data were compared with previous data from large and small posterior left ventricular infarctions. RESULTS: Ligation of two diagonal arteries infarcts 24% of the left ventricular mass and 82% of the anterior papillary muscle. Ligation of both diagonals and the first circumflex branch infarcts 33% of the left ventricle and all of the anterior papillary muscle. Neither infarction causes mitral regurgitation, although left ventricular cavity dimensions increase significantly at end systole. After the smaller infarction, the left ventricular cavity enlarges 150% over 8 weeks without mitral regurgitation. CONCLUSIONS: In sheep small and large infarctions of the anterior wall that include the anterior papillary muscle do not produce either acute or chronic mitral regurgitation despite left ventricular dilatation. In contrast large posterior infarctions produce immediate mitral regurgitation owing to asymmetric annular dilatation and discoordination of papillary muscle relationships to the valve. After small posterior infarctions that include the posterior papillary muscle, mitral regurgitation develops because of annular and ventricular dilatation during remodeling.
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Insuficiência da Valva Mitral/complicações , Infarto do Miocárdio/complicações , Infarto do Miocárdio/patologia , Animais , Dilatação Patológica , Modelos Animais de Doenças , Ventrículos do Coração/patologia , Insuficiência da Valva Mitral/diagnóstico por imagem , Músculos Papilares/patologia , Ovinos , UltrassonografiaRESUMO
BACKGROUND: Acute posterior myocardial infarction that produces immediate mitral regurgitation alters the mitral annulus and its spatial relationship with both papillary muscles. The precise deformations that cause valve insufficiency are not understood and impair efforts to repair the valve. METHODS AND RESULTS: In six Dorsett hybrid sheep, sonomicrometry transducers were placed around the mitral annulus (6) and at the tips and bases of both papillary muscles (4). Two weeks later, three branches of the circumflex coronary artery were occluded to infarct approximately 32% of the posterior left ventricle. This infarction produced acute 2 to 3+ mitral regurgitation in all animals, as determined by color flow Doppler velocity mapping. Before and after infarction, distance measurements between sonomicrometry transducers were used to produce the three-dimensional coordinates of each transducer every 5 ms. After infarction, the area of the annulus increased only 9.2+/-6.3% at end systole (ES). In addition, the normal shortening of the posterior papillary muscle was obliterated to allow its tip to move 1.4+/-0.6 mm closer to the centroid of the annulus at ES. After infarction, the anterior papillary muscle continued to shorten normally, but at ES, its tip and base were 0.9+/-0.7 mm and 1.3+/-0.7 mm farther from the centroid, respectively. CONCLUSIONS: These deformations tend to produce a relative prolapse of leaflet tissue attached to the posterior papillary muscle and restriction of leaflet tissue attached to the anterior papillary muscle. This papillary muscle discoordination with minimal annular dilatation distorts leaflet coaptation sufficiently to produce severe mitral regurgitation.