Practical Implications of Myocardial Viability Studies / Implicações Práticas da Pesquisa de Viabilidade Miocárdica

Abstract Many non-invasive methods, such as imaging tests, have been developed aiming to add a contribution to existing studies in estimating patients' prognosis after myocardial injury. This prognosis is proportional to myocardial viability, which is evaluated in coronary artery disease and left ventricular dysfunction patients only. While myocardial viability represents the likelihood of a dysfunctional muscle (resulting from decreased oxygen supply for coronary artery obstruction), hibernation represents post-interventional functional recovery itself. This article proposes a review of pathophysiological basis of viability, diagnostic methods, prognosis and future perspectives of myocardial viability. An electronic bibliographic search for articles was performed in PubMed, Lilacs, Cochrane and Scielo databases, according to pre-established criteria. The studies showed the ability of many imaging techniques in detecting viable tissues in dysfunctional areas of left ventricle resulting from coronary artery injuries. These techniques can identify patients who may benefit from myocardial revascularization and indicate the most appropriate treatment.

Resumo Diversos métodos não invasivos, como novos exames de imagem, vem sendo aprimorados, a fim de somar esforços com os atuais em estimar o prognóstico de pacientes pós-injúria miocárdica. Este prognóstico é proporcional à viabilidade miocárdica, a qual tem sua avaliação reservada para pacientes portadores de doença arterial coronariana e insuficiência ventricular esquerda. Enquanto a viabilidade miocárdica se mostra como a capacidade de recuperação funcional do músculo com disfunção por redução de oxigênio fornecido por artérias coronárias obstruídas, a hibernação consiste na própria recuperação funcional após intervenções. Este artigo propõe uma revisão sobre as bases fisiopatológicas do processo de viabilidade, métodos diagnósticos disponíveis, prognóstico e perspectivas para o futuro acerca dessa condição. Realizou-se pesquisa de busca bibliográfica informatizada em bases eletrônicas de dados, como PubMed, Lilacs, Cochrane e Scielo, onde foram selecionados os estudos de acordo com critérios pré-determinados. Os estudos demonstram a capacidade de várias técnicas de imagem de identificar tecido viável em regiões disfuncionais do ventrículo esquerdo em decorrência de lesões em artérias coronárias. Estas técnicas podem identificar pacientes com potencial benefício da revascularização miocárdica e orientar o tratamento mais adequado.

Myocardial Viability on Cardiac Magnetic Resonance / Viabilidade Miocárdica pela Ressonância Magnética Cardíaca

Abstract The study of myocardial viability is of great importance in the orientation and management of patients requiring myocardial revascularization or angioplasty. The technique of delayed enhancement (DE) is accurate and has transformed the study of viability into an easy test, not only for the detection of fibrosis but also as a binary test detecting what is viable or not. On DE, fibrosis equal to or greater than 50% of the segmental area is considered as non-viable, whereas that below 50% is considered viable. During the same evaluation, cardiac magnetic resonance (CMR) may also use other techniques for functional and perfusion studies to obtain a global evaluation of ischemic heart disease. This study aims to highlight the current concepts and broadly emphasize the use of CMR as a method that over the last 20 years has become a reference in the detection of infarction and assessment of myocardial viability.

Resumo O estudo de viabilidade miocárdica é de grande importância para a orientação e manejo de pacientes que necessitam de cirurgia de revascularização miocárdica ou angioplastia. A técnica de realce tardio (RT) é precisa e transformou o estudo de viabilidade em um teste fácil, não só para a detecção de fibrose, mas também como um modelo binário para a detecção do que é ou não é viável. Uma fibrose identificada pelo RT é considerada como não viável quando igual ou maior do que 50% da área segmentar e como viável quando menor que 50%. A ressonância magnética cardíaca (RMC) também pode lançar mão de outras técnicas para estudo funcional e de perfusão para uma avaliação global da doença isquêmica do coração no mesmo exame. Este estudo tem como objetivo destacar os conceitos atuais e enfatizar amplamente o uso da RMC como um método que nos últimos 20 anos se tornou referência na detecção de infarto e avaliação de viabilidade miocárdica.

Functional investigation of bone implant viability using radiotracers in a new model of osteonecrosis

OBJECTIVES: Conventional imaging methods are excellent for the morphological characterization of the consequences of osteonecrosis; however, only specialized techniques have been considered useful for obtaining functional information. To explore the affinity of radiotracers for severely devascularized bone, a new mouse model of isolated femur implanted in a subcutaneous abdominal pocket was devised. To maintain animal mobility and longevity, the femur was harvested from syngeneic donors. Two technetium-99m-labeled tracers targeting angiogenesis and bone matrix were selected. METHODS: Medronic acid and a homodimer peptide conjugated with RGDfK were radiolabeled with technetium-99m, and biodistribution was evaluated in Swiss mice. The grafted and control femurs were evaluated after 15, 30 and 60 days, including computed tomography (CT) and histological analysis. RESULTS: Radiolabeling achieved high (>95%) radiochemical purity. The biodistribution confirmed good blood clearance 1 hour after administration. For 99mTc-hydrazinonicotinic acid (HYNIC)-E-[c(RGDfK)2, remarkable renal excretion was observed compared to 99mTc-methylene diphosphonate (MDP), but the latter, as expected, revealed higher bone uptake. The results obtained in the control femur were equal at all time points. In the implanted femur, 99mTc-HYNIC-E-[c(RGDfK)2 uptake was highest after 15 days, consistent with early angiogenesis. Regarding 99mTc-MDP in the implant, similar uptake was documented at all time points, consistent with sustained bone viability; however, the uptake was lower than that detected in the control femur, as confirmed by histology. CONCLUSIONS: 1) Graft viability was successfully diagnosed using radiotracers in severely ischemic bone at all time points. 2) Analogously, indirect information about angiogenesis could be gathered using 999mTc-HYNIC-E-[c(RGDfK)2. 3) These techniques appear promising and warrant further studies to determine their potential clinical applications.

Adipose-derived stem cells (ADSC) in the viability of a random pattern dorsal skin flap in rats

PURPOSE: To evaluate the viability of random pattern dorsal skin flaps in rats after injection of adipose-derived stem cells (ADSC). METHODS: Thirty five adult male Wistar EPM rats (weight 250-300 g) were distributed, at random, in two groups. I- Control (flap elevation with injection of saline solution) with fifteen animals and II- Experimental (flap elevation with injection of ADSC ) with fifteen animal. The ADSC were isolated from others five adult male rats. A dorsal skin flap measuring 10x4 cm was raised and a plastic barrier was placed between the flap and its bed in both groups and the injection (cells or saline solution) were perfomed immediately after the surgery. The percentage of flap necrosis was measured on the seventh postoperative day. RESULTS: The ADSC were able to replicate in our culture conditions. We also induced their adipogenic, osteogenic and chondrogenic differentiation to verify their mesenchymal stem cells potentiality in vitro. The results were statistically significant showing that the ADSC decreased the area of necrosis (p<0.05). CONCLUSIONS: The cells demonstrated adipogenic, osteogenic and chondrogenic differentiation potential in vitro. The administration of adipose-derived stem cells was effective to increase the viability of the random random pattern dorsal skin flaps in rats. .

Adipose-derived stem cells (ADSC) in the viability of random skin flap in rats

PURPOSE: To evaluate the effects of the adipose-derived stem cells (ADSC) in the viability of random skin flap in rats. METHODS: Thirty five adult male Wistar rats (weight 250-300 g) were used. ADSC were isolated from adult male rats (n=5). ADSC were separated, cultured and then analyzed. A dorsal skin flap measuring 10x4 cm was raised and a plastic barrier was placed between the flap and its bed. After the surgical procedure, the animals were randomized into two groups (n=15 each group), group control and group ADSC. In all groups the procedures were performed immediately after the surgery. The percentage of flap necrosis was measured on the seventh postoperative day. RESULTS: The ADSC were able to replicate in our culture conditions. We also induced their adipogenic, osteogenic and chondrogenic differentiation, verifying their mesenchymal stem cells potentiality in vitro. The results were statistically significant showing that the ADSC decreased the area of necrosis (p<0.05). CONCLUSION: The cells demonstrated adipogenic, osteogenic and chondrogenic differentiation potential in vitro. The administration of adipose-derived stem cells was effective to increase the viability of the random skin flaps in rats. .

An outcome analysis and long-term viability of cryopreserved cultured epidermal allografts: assessment of the conservation of transplantable human skin allografts

PURPOSE: To assess the viability of cultured epithelium and preserved by freezing for periods varying from one month to one year. METHODS: Samples of cultured epithelium were incubated in cryoprotectant medium (Group A), packed in aluminum envelopes and packed in polystyrene boxes. The boxes were subjected to a temperature of-70ºC. After freezing for a period of time ranging from one to 12 months, cultured epithelial samples were assessed for their viability by vital staining (Trypan blue) and metabolic analysis based on glucose consumption and lactate production. Samples of not frozen cultured epithelium (Group B) were also tested for viability and the results obtained were used as comparison parameter for the variation of viability. RESULTS: Statistical analysis between the group A and B indicate that the mean age of the donors (p=0.51) and the culture time (p=1.18) showed no statistical difference. In 30 days we obtained 37% of the original viability of cultured epithelium, 25% at six months and one year, less than 15%. This trend was confirmed statistically with a reduction of approximately 1.8% of the original viability epithelium cultured every 30 days of storage. In the analysis by lactate production, similar results were observed. In the analysis by the glucose consumption results were not significant. The viability indices show statistically significant difference between the group A and B (p<0.0001). CONCLUSIONS: Although cryopreserved cultured epithelium showed significant reduction of viability, all samples remained viable. It was also found that the viability of cryopreserved cultured epithelial decreased as a function of storage time.

Increasing the rate of drying reduces metabolic imbalance, lipid peroxidation and critical water content in radicles of garden pea (Pisum sativum L.)

Orthodox seeds become desiccation-sensitive as they undergo germination. As a result, germinating seeds serve as a model to study desiccation sensitivity in plant tissues. The effects of the rate of drying on the viability, respiratory metabolism and free radical processes were thus studied during dehydration and wet storage of radicles of Pisum sativum. For both drying regimes desiccation could be described by exponential and inverse modified functions. Viability, as assessed by germination capacity and tetrazolium staining, remained at 100% during rapid (< 24 h) desiccation. However, it declined sharply at c. 0.26 g g¹ dm following slow (c. 5 days) drying. Increasing the rate of dehydration thus lowered the critical water content for survival. Rapid desiccation was also associated with higher activities and levels of malate dehydrogenase and the oxidized form of nicotinamide adenine dinucleotide. It was also accompanied by lower hydroperoxide levels and membrane damage. In addition, the activitiy of glutathione reductase was greater during rapid drying. Ageing may have contributed to increased damage during slow dehydration, since viability declined even in wet storage after two weeks. The results presented are consistent with rapid desiccation reducing the accumulation of damage resulting from desiccation-induced aqueous-based deleterious reactions. In addition, they show that radicles are a useful model to study desiccation sensitivity in plant tissues.

Perfusão miocárdica dinâmica por tomografia computadorizada de dupla fonte de raio X / Dynamic myocardial perfusion imaging by dual-source computed tomography / Perfusión miocárdica dinámica por tomografía computarizada de doble fuente de rayos X

Relatamos caso de perfusão dinâmica e quantitativa pela tomografia computadorizada de múltiplos detectores de dupla fonte de Raio X em um paciente de 44 anos, com diagnóstico prévio de doença coronariana. A tomografia demonstrou quantitativamente déficit de perfusão miocárdica nos territórios irrigados por artérias com estenoses significativas confirmadas pela angiotomografia e pela cineangiocoronariografia. A tomografia computadorizada com dupla fonte de Raio X permitiu a avaliação dinâmica perfusional e anatômica, em um único estudo, durante o controle evolutivo desse paciente.

We report a dual-source computed tomography study of dynamic and quantitative myocardial perfusion in a 44-year-old patient with previous documented coronary artery disease. Quantitatively, the tomography showed myocardial perfusion deficit in the territories with significant coronary stenosis, confirmed by computed tomography angiography and conventional angiography. Dual-source computed tomography allowed dynamic perfusion and anatomic evaluation in a single study during the follow-up of this patient.

Relatamos un caso de perfusión dinámica y cuantitativa por la tomografía computarizada de múltiples detectores de doble fuente de Rayos X, en un paciente de 44 años, con diagnóstico previo de enfermedad coronaria. La tomografía demostró cuantitativamente, un déficit de perfusión miocárdica en los territorios irrigados por arterias con estenosis significativas confirmadas por la angiotomografía y por la cineangiocoronariografía. La tomografía computarizada con doble fuente de Rayos X, permitió la evaluación dinámica de la perfusión y de la anatomía en un único estudio y durante el control evolutivo de ese paciente.

Subtotal laparoscopic splenectomy in rats with preservation of the inferior pole / Esplenectomia subtotal laparoscópica com preservação do polo inferior em ratos

Purpose: To evaluate the feasibility and safety of subtotal splenectomy by laparoscopy with inferior pole preservation and to determine the viability of the splenic remnant. Methods: Twenty male Wistar rats weighing between 365 g and 474 g (mean 417.92 ± 36.15g SD) were operated and randomly assigned to two groups : Group 1 rats were killed on postoperative day 10 (n = 10), and Group 2 on the postoperative day 80 (n = 10). Both the inferior splenic pole and the superior part of the spleen, which was used as a control to measure inferior pole viability, were weighed and morphologically examined. Results: The technique was feasible in all cases. There were two postoperative deaths on immediate postoperative and one not well defined. The average weight percentage of the inferior pole, measured indirectly on the 10th day, was 53.67 percent ± 11.59 percent and on the 80th day was 62.69 percent ± 6.89 percent. The inferior pole was necrotic, with abscess formation in one case (5.9 percent) and appeared normal in all other cases. Microscopy showed features that were compatible with normality. Conclusions: Subtotal splenectomy with preservation of the inferior pole by laparoscopy was feasible and safety. The lower splenic pole was viable in 94.1 percent of animals.

Objetivo: Avaliar a exequibilidade e a segurança da esplenectomia subtotal com preservação do polo inferior do baço por videolaparoscopia, e a viabilidade do referido polo. Métodos: 20 ratos Wistar, machos, pesando entre 365g e 474g (MA 417,92 ± 36,15g) foram operados e distribuídos em dois grupos de acordo com a época da retirada do polo inferior para estudo: grupo 1 do 10º dia, (n= 10), grupo 2, do 80º dia (n=10). A porção superior do baço que serviu de controle da viabilidade do pólo inferior e esse remanescente, retirados no término do experimento, foram medidos, pesados e enviados para exame morfológico. Resultados: A técnica foi exeqüível em todos os casos. O peso médio percentual do polo inferior avaliado de forma indireta no 10º dia foi 53,67 por cento ± 11,59 por cento, e no 80º dia 62,69 por cento ± 6,89 por cento. Houve dois óbitos após a cirurgia, provavelmente por mal condução da anestesia e/ou do pneumoperitônio, e um tardiamente por causa desconhecida. O exame macro e microscópico do polo inferior nos 17 animais sobreviventes e no que faleceu tardiamente mostrou necrose em um caso (5,9 por cento). Conclusões: A esplenectomia subtotal com preservação do pólo inferior por videolaparoscopia em ratos foi exequível e segura. O polo inferior do baço mostrou-se viável em 94,1 por cento dos animais.

Hernioplastia experimental em coelhos por meio de cartilagem auricular bovina conservada em glutaraldeído / Rabbits experimental hernioplasty by means of bovine auricular cartilage preserved in glutaraldehyde

Avaliou-se a viabilidade do emprego da cartilagem auricular bovina conservada em glutaraldeído a 4 por cento na hernioplastia experimental, empregando-se seis coelhos adultos, machos, da raça Nova Zelândia. Para obtenção da hérnia incisional, removeu-se um segmento elíptico de 3cm de comprimento por 1cm de largura, no ponto central à primeira incisão, envolvendo fáscia e tecido muscular, na região da cicatriz umbilical. Dois animais de cada vez foram sacrificados aos 15, 30 e 45 dias após a cirurgia. Nos sacrificados aos 15 dias, observaram-se áreas focais de inflamação, caracterizadas por abscesso e fístula. À microscopia, observou-se área de inflamação e necrose próxima à periferia do implante. Nas amostras colhidas dos animais sacrificados aos 30 dias, não foram evidenciadas alterações clínicas relevantes. Desses, um animal apresentou à microscopia intensa proliferação fibroblástica, moderada neovascularização e células inflamatórias predominantemente mononucleares. Dos sacrificados aos 45 dias, em um ocorreu aderência de alça intestinal ao implante. É possível inferir que o material implantado apresentou satisfatória compatibilidade com o tecido receptor. Conclui-se que o implante de cartilagem auricular bovina conservada na hernioplastia experimental em coelhos apresentou evidências de boa integração tecidual e cicatrização, não havendo eliminação do material implantado.

The auricular cartilage preserved in 4 percent glutaraldehyde was used for experimental hernioplasty in six male, adult, New Zealand rabbits. To create an incision hernia, an elliptic tissue fragment three centimeter-long and one-centimeter wide was removed at a point centrally located from the first incision, embracing fascia and muscle tissue, from the area of umbilical scar. Animals were euthanized, two at a time, 15, 30, or 45 days after surgery. In the animals euthanized after 15 days focal areas of inflammation were observed, characterized by abscesses and fistulas. The histological section showed areas of inflammation and necrosis next to the periphery of the graft. In the animals euthanized after 30 days, there was no evidence of clinical alterations. Microscopic diagnosis of one of these animals showed intense fibroblastic proliferation, moderate neovascularization and inflammatory cells, predominantly mononuclear. One of the animals submitted to euthanasia at 45 days presented at necropsy adherence of bowel to the graft and impaired reconstitution of the parietal peritoneum. It is possible to infer that the grafted material presented satisfactory compatibility with the receptor tissue. Thus, it may be concluded that auricular bovine cartilage grafts preserved in 4 percent glutaraldehyde in experimental hernioplasty in rabbits presented evidence of good tissue integration and healing, with no elimination of the grafted material.

Myocardial viability assessment: comparison between resting two dimensional visual assessment of dobutamine stress echocardiography and strain rate imaging

Patients with ischemic left ventricular dysfunction are increasingly referred for the assessment of myocardial viability. The issue of identifying dysfunctional but viable myocardium has crucial clinical importance, since revascularization increases survival only in patients with viable myocardial tissue. The aim of this study was to compare resting two-dimensional visual assessment of myocardial viability with dobutamine stress echocardiography and strain rate imaging. In this cross-sectional study, thirty-two consecutive patients [age: 55.3 +/- 22.7, 4 females] with ischemic left ventricular dysfunction were referred for myocardial viability assessment. Viability was evaluated using resting two-dimensional echocardiograms, dobutamine stress echocardiography and strain rate imaging. Viability was defined by the absence of brightness and thinning [<6 mm thickness] in akinetic segments, improvement by at least one grade or a biphasic response during dobutamine stress echocardiography or an increase in the peak systolic strain rate [more than -0.23 1/s]. A total of 254 segments were studied. Seventy- nine segments by dobutamine stress echocardiography, 70 segments by two-dimensional visual assessment, and 63 segments by strain rate were classified as non-viable [P< 0.001]. There was an almost perfect agreement among these diagnostic methods. Two-dimensional visual assessment with measurement of wall thickness is simple and practical methods for viability assessment, with almost perfect agreement with dobutamine stress echocardiography and strain rate imaging

Evaluación histológica de la reparación tisular post palatectomía parcial equina / Histologic evaluation of tissue repair post-partial palectomy equine

Objetivo. Evaluar la reparación tisular posterior a la realización de técnicas de palatectomía parcial, como tratamiento de la palatitis en equinos. Materiales y métodos. Se utilizaron 12 caballos, divididos aleatoriamente en dos grupos, ambos con seis animales, a los del primer grupo se les practicó palatectomía parcial con suturación y a los del segundo grupo, se les realizó palatectomía parcial y luego cauterización. Los grupos fueron divididos en tres subgrupos de dos animales cada uno. A los primeros subgrupos, suturados y cauterizados, se les tomó biopsia el día 5; a los segundos subgrupos, el día 15 y a los terceros el día 30 posquirúrgico. Resultados. El día 5 posquirúrgico,en ambos grupos se observó la presencia de infiltrado celular inflamatorio de tipo mononuclear (macrófago), inicio del proceso de epitelización, proliferación fibroblástica y formación de nuevos vasos sanguíneos; notándose severa ulceración del epitelio con abundantes detritos celulares solo en los animales cauterizados. El día 15 posquirúrgico, en los animales suturados, se observó infiltrado celular mononuclear, proliferación epitelial y fibroblástica, y presencia de nuevos vasos sanguíneos. Las muestras de los animales cauterizados, presentaron además, ulceración epitelial, detrituscelulares y formación de tejido de granulación desorganizado. El día 30 posquirúrgico, los animalessuturados, no mostraron inflamación evidente, el epitelio se observó con características normalesaunque más grueso que el adyacente. En los animales cauterizados, no se observó infiltrado celularmononuclear, aunque continuaba la ulceración epitelial, igualmente existía, proliferación fibroblástica desorganizada y abundantes fibras colágenas. Conclusión. Es posible concluir que el proceso de reparación tisular se vio favorecido por la técnica de palatectomía parcial con suturación.

Objective. To evaluate the tissue repair posterior to realization of technical partial paladin, as treatment of palatitis in equine. Materials and methods. 12 horses were used, divided aleatorily intwo groups, both with six animals, to those of first group were practiced partial paladin with saturation and to those of the second group, partial paladin were practiced and then cauterization. The groups were divided in three subgroups of two animals each one. To the first ones sutured and cauterized, biopsy were taken the day 5; to the second ones the day 15 and at the third ones the day 30 postsurgeon. Results. The day 5 post surgeon, in both groups the presence of cellular infiltrate inflammatory was observed of mononuclear type, initiation of the epithelization process, fibroblasticproliferation and formation of new sanguine vessels; being noticed severe ulceration of the epithelium with abundant cellular detrituses in the cauterized animals. The day 15 post surgeon, in the sutured animals was observed infiltrated cellular mononuclear, epithelial proliferation and fibroblastic, and presence of new sanguine vessels. Samples of the cauterized animals also presented epithelial ulceration, cellular detritus and formation of disorganized granulation tissue. The day 30 post surgeon the sutured animals didn’t show evident inflammation, the epithelium was observed with normal characteristics although thicker that the adjacent one. In the cauterized animals, infiltrated cellular mononuclear was not observed, although the epithelial ulceration continued, equally existeddisorganized fibroblastic proliferation and abundant collagen fibers. Conclusion. It is possible to conclude that the process of tissue repair was favored by the technique of partial paladin with suturation.

Viabilidade miocárdica na lesão uniarterial: papel da ecocardiografia de estresse com dobutamina / Myocardial viability in a single-vessel disease: the role of a dobutamine stress echocardiography

OBJETIVO: Estudar um grupo de pacientes com lesão significativa em apenas uma artéria coronária e demonstrar se a ecocardiografia de estresse com dobutamina (EED) tem boa sensibilidade e especificidade na avaliação de viabilidade miocárdica nesse grupo de pacientes. MÉTODOS: Foram estudados 20 pacientes submetidos a angioplastia coronariana transluminal percutânea (ATC). Esse grupo foi avaliado 2 a 7 (3,65 ± 1,69) dias antes do procedimento, e 2 a 5 (4 ± 0,80) dias depois, realizando-se EED. Para a determinação de viabilidade miocárdica foi utilizado ecocardiograma bidimensional três meses após o procedimento. Doze pacientes foram submetidos a ATC de artéria descendente anterior (DA), 7 de artéria coronária direita (CD) e 1 de circunflexa (CX). Apenas um procedimento (CD) não obteve pleno êxito. RESULTADOS: Dos 340 segmentos estudados, 99 (29,18 por cento) demonstraram alterações contráteis, sendo 63 hipocinéticos (63,4 por cento), 28 acinéticos (28,28 por cento) e 8 discinéticos (8,08 por cento). Quanto aos segmentos envolvidos, obtivemos sensibilidade de 92,59 por cento, especificidade de 84,45 por cento, acurácia de 88,88 por cento para o exame EED. O único caso de ATC de CX demonstrou sensibilidade de 100 por cento; para DA, sensibilidade de 88,58 por cento, especificidade de 95 por cento e acurácia de 90,91 por cento. Para segmentos da CD, sensibilidade de 91,30 por cento, especificidade de 83,33 por cento e acurácia de 88,71 por cento. Todos os segmentos discinéticos eram inviáveis. Dos 63 hipocinéticos, a EED previu recuperação em 91,48 por cento. CONCLUSÃO: A EED é útil na avaliação de viabilidade miocárdica em pacientes com lesão significativa de apenas uma artéria.

Viability of a random pattern dorsal skin flap, in diabetic rats

OBJETIVO: Avaliar a viabilidade do retalho cutâneo randômico dorsal em ratos experimentalmente induzidos ao diabetes mellitus. MÉTODOS: Foram utilizados 30 ratos Wistar, adultos, machos, distribuídos em 2 grupos: I controle submetidos somente ao retalho cutâneo e II experimental submetidos ao retalho cutâneo após 10 dias da indução do diabetes mellitus com aloxano. RESULTADOS: O grupo controle teve 36,39% e o grupo experimental 52,06% de média de área de necrose. CONCLUSÃO: A viabilidade do retalho cutâneo randômico dorsal foi menor no rato diabético do que no rato normal.

Assessment of Tissue Viability Using Diffusion- and Perfusion-Weighted MRI in Hyperacute Stroke

OBJECTIVE: The aim of this study was to investigate the relationship between the diffusion and perfusion parameters in hyperacute infarction, and we wanted to determine the viability threshold for the ischemic penumbra using diffusion- and perfusion-weighted imaging (DWI and PWI, respectively). MATERIALS AND METHODS: Both DWI and PWI were performed within six hours from the onset of symptoms for 12 patients who had suffered from acute stroke. Three regions of interest (ROIs) were identified: ROI 1 was the initial lesion on DWI; ROI 2 was the DWI/PWI mismatch area (the penumbra) that progressed onward to the infarct; and ROI 3 was the mismatch area that recovered to normal on the follow-up scans. The ratios of apparent diffusion coefficient (ADC), the relative cerebral blood volume (rCBV), and the time to peak (TTP) were calculated as the lesions' ROIs divided by the contralateral mirror ROIs, and these values were then correlated with each other. The viability threshold was determined by using the receiver operating characteristic (ROC) curves. RESULTS: For all three ROIs, the ADC ratios had significant linear correlation with the TTP ratios (p < 0.001), but not with the rCBV ratios (p = 0.280). There was no significant difference for the ADC and rCBV ratios within the ROIs. The mean TTP ratio/TTP delay between the penumbras' two ROIs showed a significant statistical difference (p < 0.001). The cutoff value between ROI 2 and ROI 3, as the viability threshold, was a TTP ratio of 1.29 (with a sensitivity and specificity of 86% and 73%, respectively) and a TTP delay of 7.8 sec (with a sensitivity and specificity of 84% and 72%, respectively). CONCLUSION: Determining the viability thresholds for the TTP ratio/delay on the PWI may be helpful for selecting those patients who would benefit from the various therapeutic interventions that can be used during the acute phase of ischemic stroke.

Viability and enzymatic activity of cryopreserved porcine heart valve

Fibroblast viability of a natural tissue valve for replacing a defective heart valve through allograft or xenograft has been suggested to affect its clinical durability. In this study, the cell viability and enzymatic activity of porcine heart valve leaflets were examined in regard to concerning to the preservation process [variable warm ischemic time (WIT), cold ischemic time (CIT), and cryopreservation]. Porcine heart enblocs were obtained and valve dissection was performed after 2, 12, 24, or 36 hours, in respective groups A, B, C, and D, as WIT. Each group was stored for 24 hours as CIT and cryopreserved. Leaflets were dissected from a valved conduit after each process, and cell viability and enzymatic activity in the leaflet were investigated using trypan blue staining and API ZYM kits. WIT extension significantly decreased fibroblast viability (p < 0.05, 92.25 +/- 2.7% at 2 hours, 84.9 +/- 6.7% at 12 hours, 57.0 +/- 10.2% at 24 hours, 55.9 +/- 7.9% at 36 hours), while CIT for 24 hours was also influenced significantly (p < 0.05), whereas cryopreservation demonstrated no effect on cellular viability. In enzyme activity observation, several enzymes related to lipid or nucleotide degradation (esterase, esterase lipase, particularly phosphatase, phosphohydrolase) were remarkably changed following the valve-fabrication process. After 24 hours CIT, these enzymatic activities in groups B, C and D significantly increased, but the activities decreased after cryopreservation. Particularly, both the viability and enzymatic activity showed remarkable changes after CIT in group B (WIT = 12 hours). These results suggest that WIT is more important than CIT in maintaining viability of the valve, and that completing all the cryopreservation process within 12 hours after acquisition is recommended.

Empleo del Captopril en la determinación de la viabilidad miocárdica en una ventriculografía nuclear / Captopril usage in determining myocardial viability on a nuclear ventriculography

Con el propósito de diagnosticar la viabilidad miocárdica en pacientes infartados con pobre función ventricular, empleamos el efecto vasodilatador del captopril en una ventriculografía nuclear. Se estudiaron 14 casos con una fracción de eyección del ventrículo izquierdo en reposo menor del 50 por ciento. A todos se les realizó una ventriculografía nuclear (pre y pos 25 mg de captopril, v.o.) y una gammagrafía de perfusión miocárdica con talio-201 y reinyección. La fracción de eyección aumentó de 38 ñ 10 por ciento a 42 ñ 12 por ciento (p < 0,01) con el captopril. La presión arterial sistólica disminuyó de 132 ñ 24 mm de Hg a 126 ñ 27 mm de Hg (p < 0,05). La presión arteiral distólica, y la frecuencia cardíaca y los volúmenes ventriculares no se modificaron significativamente poscaptopril. En 11 de los 14 pacientes hubo concordancia en el diagnóstico de viabilidad obtenido por ventriculografía y gammagrafía. Se concluye que la ventriculografía nuclear con captopril puede ser un método alternativo útil y económico para el diagnóstico de la viabilidad miocárdica en enfermos infartados con pobre función contráctil

Evaluación de la viacilidad miocárdica: importancia clínica y métodos de evaluación

En la última década, la evaluación por técnicas de medicina nuclear y ecocardiografía de la presencia y extensión del miocardio viable pero disfuncional se ha vuelto un punto importante del análisis clínico en los pacientes con enfermedad coronaria y disfunción ventricular izquierda. La disminución de la función ventricular izquierda no es siempre un proceso irreversible relacionado con infartos previos, debido a que ésta puede mejorar considerablemente después de procedimientos de revascularización coronaria, tales como angioplastia coronaria o cirugía de puentes coronarios. El análisis no invasivo de la viabilidad miocárdica aporta información pronóstica que asiste en una mejor selección de los pacientes con disfunción ventricular izquierda y que se pueden beneficiar más de procedimeintos de revascularización coronaria que de manejo médico o de trasplante cardíaco. Los mecanismos celulares responsables para una respuesta inotrópica positiva a la estimulación adrenérgica (reserva contráctil) pueden requerir un mayor grado de integridad funcional del miocito que aquellas responsables para la captación de fluorodeoxiglucosa, talio o sestamibi (integridad de la membrana celular), Las técnicas por medicina nuclear evalúan la viabilidad estructural, mientras que la ecocardiografía con dobutamina define la viabilidad sobre la base de la recuperación funcional. El análisis de la viabilidad miocárdica debe ser multidisciplinario y debe tener en cuenta los resultados de la angiografía coronaria, los estudios de viabilidad miocárdica por medicina nuclear y los de reserva contráctil por ecocardiografía o imagen de resonancia magnética