abc Arquivos Brasileiros de Cardiologia Arq. Bras. Cardiol. 0066-782X 1678-4170 Sociedade Brasileira de Cardiologia - SBC São Paulo, SP, Brazil VMsR8t4fyLdfWJ8DgNHRCWp 00012 S0066-782X2006001900012 S0066-782X(06)08700612 10.1590/S0066-782X2006001900012 Artigos Originais O papel do acúmulo de colágeno no interstício miocárdico na sobrevida dos pacientes com cardiomiopatia dilatada idiopática e chagásica Nunes Vera Lopes Ramires Felix José Alvarez Pimentel Walace de Souza Fernandes Fábio Ianni Barbara Maria Mady Charles São Paulo São Paulo Universidade de São Paulo FM Hospital das Clínicas Brazil 12 2006 87 6 757 762 01 07 2005 23 06 2005 23 05 2005 This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

OBJETIVO: Avaliar a correlação entre um marcador estrutural do miocárdio e a sobrevida dos pacientes com cardiomiopatia dilatada. MÉTODOS: Mediante realização da biópsia endomiocárdica e exame ecocardiográfico foram estudados 9 indivíduos sem doença estrutural miocárdica (controle) e 45 pacientes com cardiomiopatia dilatada grave de etiologia idiopática (MCDI) e chagásica (MCDC). Foi analisada a correlação entre a quantidade de colágeno miocárdico intersticial (FVCI) e a sobrevida desses pacientes, se a FVCI diferia entre as etiologias, e se a fibrose interferia na função e geometria do miocárdio. RESULTADOS: Foi observado que a FVCI foi 15 vezes maior nos cardiomiopatas em relação ao grupo-controle, mas não diferiu em relação às MCDI e MCDC (*p < 0,001). Não houve correlação da FCVI com a sobrevida dos pacientes com cardiomiopatias (MCDI p = 0,249 e na MCDC p = 0,587) e apenas na MCDI a fração de ejeção do ventrículo esquerdo teve correlação com a FVCI. O diâmetro diastólico final do ventrículo esquerdo não se correlacionou com a FCVI nas duas etiologias. CONCLUSÃO: A fibrose miocárdica não diferiu entre as duas etiologias, não se correlacionou com o prognóstico das MCDC e MCDI e apenas na MCDI ela se correlacionou com a FEVE.

 Colágeno miocárdio prognóstico cardiomiopatia dilatada 18 01 2007

ARTIGO ORIGINAL

O papel do acúmulo de colágeno no interstício miocárdico na sobrevida dos pacientes com cardiomiopatia dilatada idiopática e chagásica

Vera Lopes Nunes; Felix José Alvarez Ramires; Walace de Souza Pimentel; Fábio Fernandes; Barbara Maria Ianni; Charles Mady

Instituto do Coração do Hospital das Clínicas – FMUSP, São Paulo, SP

Correspondência

RESUMO

OBJETIVO: Avaliar a correlação entre um marcador estrutural do miocárdio e a sobrevida dos pacientes com cardiomiopatia dilatada.

MÉTODOS: Mediante realização da biópsia endomiocárdica e exame ecocardiográfico foram estudados 9 indivíduos sem doença estrutural miocárdica (controle) e 45 pacientes com cardiomiopatia dilatada grave de etiologia idiopática (MCDI) e chagásica (MCDC). Foi analisada a correlação entre a quantidade de colágeno miocárdico intersticial (FVCI) e a sobrevida desses pacientes, se a FVCI diferia entre as etiologias, e se a fibrose interferia na função e geometria do miocárdio.

RESULTADOS: Foi observado que a FVCI foi 15 vezes maior nos cardiomiopatas em relação ao grupo-controle, mas não diferiu em relação às MCDI e MCDC (*p < 0,001). Não houve correlação da FCVI com a sobrevida dos pacientes com cardiomiopatias (MCDI p = 0,249 e na MCDC p = 0,587) e apenas na MCDI a fração de ejeção do ventrículo esquerdo teve correlação com a FVCI. O diâmetro diastólico final do ventrículo esquerdo não se correlacionou com a FCVI nas duas etiologias.

CONCLUSÃO: A fibrose miocárdica não diferiu entre as duas etiologias, não se correlacionou com o prognóstico das MCDC e MCDI e apenas na MCDI ela se correlacionou com a FEVE.

Palavras-chave: Colágeno, miocárdio, prognóstico, cardiomiopatia dilatada

A cardiomiopatia dilatada representa 87% das cardiomiopatias. A cardiomiopatia dilatada idiopática (MCDI) é aquela de origem indeterminada, excluindo-se causas secundárias. Nos Estados Unidos, sua incidência é de 5 a 8/100.000 habitantes na população geral, representando um quarto das cardiomiopatias dilatadas, com prevalência ajustada à idade de 36/100.000 na população geral, sobrevida em cinco anos de 25% a 65%, dependendo do estágio evolutivo, e mortalidade anual de dez mil casos1-4. A cardiomiopatia dilatada chagásica (MCDC) é considerada uma doença inflamatória secundária à infecção de um parasita, o Trypanosoma cruzi. Dados da Organização Mundial de Saúde revelam que cerca de 90 milhões de pessoas estão expostas ao risco de infecção pelo Trypanosoma cruzi, sendo a incidência em 1995 de 120 mil novos casos de infecção pelo parasita5.

Independentemente da etiologia, o acúmulo de colágeno no interstício e no espaço perivascular do miocárdio se faz presente. O colágeno miocárdico sabidamente desempenha importantes funções que afetam diretamente a morfologia, geometria e desempenho funcional do coração. Shirey e cols.6, estudando pacientes cardiomiopatas, demonstraram pela primeira vez que o aumento da fibrose miocárdica era encontrado em pacientes com maior mortalidade. Schwarz e cols.7 e Figulla e cols.8, por sua vez, considerando pacientes com cardiomiopatia dilatada, não demonstraram relação dos dados morfológicos, como hipertrofia dos cardiomiócitos e aumento da quantidade de colágeno intersticial, com informações prognósticas.

Marcadores clínicos, funcionais e bioquímicos do prognóstico das cardiomiopatias dilatadas e insuficiência cardíaca (IC) são bem definidos. Entretanto, um marcador histológico ainda não foi estabelecido. Faz-se, então, importante avaliar o papel do colágeno miocárdico intersticial como marcador prognóstico estrutural nas cardiomiopatias dilatadas. Dessa forma, nossa hipótese é de que a quantidade de colágeno miocárdico intersticial teria papel relevante, dependente ou não da função ventricular, na sobrevida dos pacientes com cardiomiopatia dilatada idiopática e de origem chagásica.

Nossos objetivos foram avaliar se há correlação entre a quantidade de colágeno miocárdico intersticial e a sobrevida dos pacientes com cardiomiopatia dilatada grave idiopática e chagásica; verificar se a quantidade de colágeno intersticial do miocárdio difere quanto à etiologia chagásica e idiopática; correlacionar a quantidade de colágeno miocárdico intersticial com a fração de ejeção (FEVE) e diâmetro diastólico (DDVE) do ventrículo esquerdo.

Métodos

Após a aprovação do Comitê de Ética da instituição (Resolução do Conselho Nacional de Saúde 196/96 de 10 de setembro de 1996), foram revistos, pelo registro de biópsia endomiocárdica e levantamento de prontuário hospitalar, os diagnósticos de pacientes que realizaram biópsia endomiocárdica no período de 1981 a 1998. Excluídos aqueles de seguimento de transplante cardíaco, foram totalizados 1.406 casos. Desses, foram selecionados aqueles com diagnóstico de cardiomiopatia dilatada de etiologia idiopática (n = 116) e chagásica (n = 126). Aplicados os critérios de inclusão e de exclusão, foram incluídos no estudo 19 pacientes com cardiomiopatia dilatada idiopática e 26 com cardiomiopatia chagásica.

Para o diagnóstico das cardiomiopatias foram seguidos os critérios da OMS/SIFC9. As cardiomiopatias dilatadas idiopáticas são aquelas de causa desconhecida, sendo excluídas as causas secundárias, como hipertensão arterial, doenças coronarianas, valvares, congênitas, miocardite, hipertensão pulmonar e dilatação de ventrículo direito isolado. A cardiomiopatia dilatada chagásica é definida como doença inflamatória do miocárdio associada à disfunção miocárdica, secundária à infecção pelo Trypanosoma cruzi diagnosticada por meio da sorologia positiva (imunofluorescência e reação de fixação do complemento). Informações sobre as mortes foram obtidas dos registros hospitalares, atestados de óbito, contato telefônico com familiares e pelo prontuário hospitalar.

Os critérios de inclusão foram: uso de fármacos inibidores da enzima de conversão da angiotensina, no mínimo quatro meses antes da realização da biópsia endomiocárdica e durante todo o seu seguimento; cinecoronariografia normal no grupo idiopático e naqueles com mais de dois fatores de risco para doença coronariana no grupo chagásico; sorologia para doença de Chagas (imunofluorescência e reação de fixação do complemento) positiva, ou negativa no grupo idiopático; laudo do ecocardiograma com até dois meses da realização da biópsia endomiocárdica, com FEVE menor ou igual a 0,40 pelo método Teichholz.

Os critérios de exclusão foram: cardiomiopatia isquêmica, afastada pela cinecoronariografia, hipertensão arterial sistêmica e outras doenças cardíacas que não as estudadas10,11; insuficiência renal, definida como nível de creatinina sérica > 2,0 mg/dl; pacientes submetidos a transplante cardíaco e/ou a cardiomioplastia; e pacientes que perderam seguimento ambulatorial.

O estudo teve início no momento da realização da biópsia endomiocárdica do paciente e término com o evento morte ou o seguimento do paciente até julho de 2003.

Para comparação dos resultados da quantidade de colágeno intersticial no miocárdio e dos dados ecocardiográficos de DDVE e FEVE foi constituído um grupo-controle de nove pacientes que tinham indicação cirúrgica de revascularização miocárdica em oito, e exérese de mixoma de átrio esquerdo em um paciente. Foram considerados critérios de exclusão: infarto do miocárdio prévio, disfunção ventricular, valvopatia primária e medida da pressão arterial maior ou igual a 140/90 mmHg aferida em mais de duas ocasiões.

Ecocardiograma - O exame de ecocardiograma com a utilização dos modos M (unidimensional), bidimensional e da técnica de Doppler foi realizado em todos os pacientes com até dois meses do procedimento da biópsia endomiocárdica. Esses exames foram realizados conforme as recomendações da Sociedade Americana de Ecocardiografia; a medida do DDVE (em milímetros) foi obtida no final da diástole e o cálculo de função ventricular foi avaliado pela FEVE, sendo obtido pelo método Teichholz.

Biópsia endomiocárdica -Os pacientes foram submetidos a biópsia endomiocárdica do ventrículo direito, segundo as técnicas descritas por Mason12. Os fragmentos do grupo-controle foram obtidos durante a cirurgia cardíaca, aproximadamente nas mesmas regiões do septo interventricular em que a biópsia é obtida por via percutânea.

Morfometria do colágeno - A partir dos blocos de parafina, novos cortes de 5 µm foram montados em lâminas e coradas pelo picrosirius-red para detecção e quantificação do colágeno intersticial.

As frações dos volumes de colágeno intersticial (FVCI) foram quantificadas por videomorfometria, utilizando-se um sistema de análise de imagens (Quantimet 520 Image Analysis System-Cambridge Instruments, Cambridge, UK). A morfometria foi realizada por dois observadores que não tinham conhecimento do quadro clínico dos pacientes. Cada parâmetro representa o valor médio de todas as medidas obtidas de cada tecido da biópsia.

Análise estatística - A análise de sobrevida foi realizada pelo método de Kaplan-Meier e para comparação das curvas foi empregada o teste de log-rank. Foi calculado o coeficiente de correlação de Pearson (r), a análise de variância (ANOVA) e o teste Kruskal-Wallis (quando as variâncias não eram homogêneas) para comparações. O teste de Tukey-HSD foi empregado para as múltiplas comparações. Os resultados foram considerados estatisticamente significativos quando p < 0,05, e os valores foram expressos como média e desvio padrão.

Resultados

Aspectos demográficos - Foram estudados 19 pacientes com cardiomiopatia dilatada idiopática, 26 pacientes com cardiomiopatia dilatada chagásica e 9 pacientes constituíram o grupo-controle (tab.1). Observou-se predomínio de pacientes do sexo masculino nos 3 grupos. O grupo-controle foi constituído por indivíduos mais velhos, mas os pacientes cardiomiopatas tinham a média de idade semelhante. Não foi analisada a sobrevida dos pacientes do grupo controle, pois estes apresentavam doenças diferentes. A sobrevida dos pacientes cardiomiopatas foi maior no grupo idiopático, variando entre 5 e 2.281dias (761 ± 165), e nos chagásicos entre 6 e 2.166 dias (422 ± 109), porém sem significado estatístico (p = 0,145) (tab. 1).

Aspectos ecocardiográficos - Foram analisados os parâmetros de DDVE e da FEVE. Os valores das médias do DDVE encontrados nos grupos dos pacientes cardiomiopatas foram maiores do que aqueles do grupo-controle (p < 0,001), sendo maior nos pacientes com MCDI que o grupo com MCDC (p = 0,005) (tab. 2). Em relação aos valores da FEVE, estes foram menores nos grupos com cardiomiopatia do que o grupo-controle (p < 0,001) como mostra a tabela 2.

Análise de sobrevida - Em relação à etiologia das cardiomiopatias, não houve diferença estatisticamente significativa entre as taxas de sobrevida global em cinco anos nos pacientes com cardiomiopatia chagásica (3,8%) e os com cardiomiopatia idiopática (10,5%) (p = 0,131) (fig.1).

O DDVE foi avaliado através da sua mediana (73 mm). Não houve diferença estatisticamente significativa entre as taxas de sobrevida global em 5 anos nos pacientes portadores de MCDC com DDVE < 73 (5,3%) ou > 73 (0,0%) (p = 0,246), o mesmo em relação aos pacientes com MCDI com DDVE < 73 (0,0%) ou > 73 (16,7%) (p = 0,269).

Em relação à FEVE, não houve diferença estatisticamente significativa entre as taxas de sobrevida global em cinco anos nos pacientes com MCDC com FEVE < 0,30 (0,0%) ou > 0,30 (7,7%) (p = 0,391). Entretanto, no grupo com MCDI essa relação pôde ser observada com menor sobrevida nos pacientes com FEVE menor (FEVE < 0,30; 0,0%) ou > 0,30 (20,0%) (p = 0,031) (fig.2).

Morfometria do colágeno - Observou-se aumento da quantidade de colágeno miocárdio intersticial nos grupos constituídos por cardiomiopatas em relação ao grupo controle (p < 0,001), mas essa diferença não foi significativa entre as duas etiologias (p = 0,724) (figs.3 e 4).

Correlações com a FVCI - Avaliando a relação entre a FVCI e a taxa de sobrevida global em cinco anos dos pacientes com MCDI e MCDC, não houve diferença estatisticamente significativa. Analisamos essa dissociação em relação à mediana da FVCI < 5,53 (8,7%) ou > 5,53 (4,5%) (p = 0,749) (fig. 5). Quando separamos os pacientes com cardiomiopatia segundo as etiologias e correlacionamos a FVCI com a sobrevida, também não encontramos diferença estatisticamente significativa entre as taxas de sobrevida global em cinco anos nos pacientes com FVCI < 5,53 (0,0%) ou > 5,53 (7,7%) (p = 0,587) tanto no grupo chagásico (fig. 6) quanto no grupo idiopático com FVCI < 5,53 (20,0%) ou > 5,53 (0,0%) (p = 0,249) (fig. 7).

Quando analisamos a FVCI com a FEVE não observamos correlação no grupo MCDC (r= 0,10 ; p= 0,61), mas houve correlação linear positiva nos pacientes com MCDI (r= 0,50; p= 0,02) (fig. 8). Não houve correlação entre a FVCI e o DDVE nas duas etiologias.

Discussão

Atualmente, as cardiomiopatias dilatadas não são consideradas apenas uma desordem da contratilidade miocárdica, mas sim uma seqüência complexa de eventos e mediadores que altera os componentes celulares e moleculares do miocárdio. Essas repostas, do ponto de vista histológico, são limitadas e caracterizadas por hipertrofia, degeneração, atrofia e necrose dos cardiomiócitos, perda das miofibrilas, infiltrado intersticial inflamatório e fibrose perivascular e intersticial. Na hipertrofia ventricular esquerda, não-fisiológica, há aumento progressivo, ilimitado e não-proporcional da quantidade de colágeno, mudando, assim, o rearranjo entre as células miocárdicas. Essa nova arquitetura miocárdica prejudica a produção da força de contração, levando à disfunção sistólica e ao aparecimento dos sintomas de IC13-19.

Apesar de os nossos resultados não definirem que a quantidade de colágeno miocárdico intersticial tem relação com a sobrevida dos pacientes estudados com cardiomiopatia dilatada (p= 0,749), mesmo após separarmos pelas etiologias chagásica (p= 0,587) e idiopática (p= 0,249), podemos observar que aqueles pacientes com cardiomiopatia dilatada com quantidade de colágeno miocárdio intersticial menor tinham sobrevida global em cinco anos de 8,7%, contra 4,5% encontrada naqueles com quantidade de colágeno miocárdico intersticial maior. Esses resultados corroboram os dados apresentados por Unverferth e cols.20 em pacientes com cardiomiopatia dilatada não-isquêmica, nos quais evidenciaram que a fibrose foi maior nos que não sobreviveram, mas sem importância prognóstica (p= 0,26). Quando comparamos as duas etiologias em relação à sobrevida, também não encontramos resultados significativos, mas observamos que a etiologia chagásica apresentou 3,8% de sobrevida em 5 anos e a etiologia idiopática, 10,5%. Talvez a persistência da atividade da miocardite, pela participação direta do parasita ou por mecanismos imunológicos, e também a distribuição difusa das lesões histológicas tenham alguma contribuição para a evolução mais desfavorável da etiologia chagásica.

A medida quantitativa do colágeno miocárdico intersticial, isoladamente, não expressa toda a complexidade do remodelamento miocárdico. Talvez, para conseguirmos demonstrar a relação do remodelamento com a sobrevida, devêssemos incluir na análise outras alterações que participam da arquitetura miocárdica, como o tipo de distribuição (difusa ou localizada) das fibras de colágeno pelo miocárdio, a sua relação com os cardiomiócitos e no alinhamento destes, a formação de agrupamentos de colágeno no miocárdio, funcionando como verdadeiros obstáculos na transmissão da força de contração gerada para toda a câmara cardíaca, a perda da integridade, propiciando uma contração dessincronizada do miocárdio, levando à diminuição da função sistólica16,21-23. Além desses fatores, o remodelamento miocárdico também representa mudanças celulares e moleculares, ocasionando hipertrofia e talvez hiperplasia, necrose e apoptose dos cardiomiócitos.

Em nosso estudo, os resultados da morfometria na quantificação do colágeno intersticial do miocárdio de pacientes com cardiomiopatia dilatada chagásica, não diferiram dos resultados obtidos no grupo idiopático, mas foram em média 15 vezes maiores que aqueles encontrados nos pacientes do grupo-controle.

A verificação se existe relação entre o aumento da quantidade de colágeno miocárdico intersticial e as alterações na função miocárdica é relevante. Mady e cols.24, em pacientes com cardiomiopatia dilatada chagásica, Weber e cols.15,16 e Jalil e cols.22, em modelos animais de hipertrofia do ventrículo esquerdo, relacionaram o aumento da quantidade de colágeno do miocárdio, geralmente superior a 20% do seu valor normal, com diminuição da eficácia em gerar forças pelo miocárdio. Por sua vez, Nakayama e cols.25 observaram que a fibrose miocárdica intersticial e a hipertrofia dos cardiomiócitos correlacionavam-se e estavam associados à deterioração da contratilidade miocárdica em pacientes com cardiomiopatia dilatada. Em nossa análise, quando avaliamos a quantidade de colágeno miocárdico intersticial com a FEVE de pacientes com a MCDC, não observamos correlação. Entretanto, quando analisamos essas duas variáveis em relação aos pacientes com MCDI, observamos uma significativa correlação. Esse fato pode estar relacionado com fatores próprios da fisiopatologia da função miocárdica, podendo apresentar maior importância na participação dos mediadores inflamatórios na MCDC, não sendo o acúmulo de colágeno a principal causa dessa disfunção. A FEVE não apresentou relação com a sobrevida global nos pacientes com cardiomiopatia dilatada chagásica, mas sim com a dos pacientes com a etiologia idiopática. Isso talvez tenha ocorrido pelo envolvimento de outros mecanismos fisiopatológicos na cardiomiopatia chagásica, como maior liberação de mediadores inflamatórios, persistência do parasita ampliando a resposta inflamatória local e ativação auto-imune, intensificando a piora da função miocárdica, além daquela ocasionada pelo acúmulo de colágeno. Unverferth e cols.20 observaram que, além da FEVE, o DDVE também é um fator importante no prognóstico das cardiomiopatias. Entretanto, o DDVE, que foi uma medida com valores significativamente diferentes entre os três grupos de pacientes estudados, quando avaliados com a quantidade de colágeno miocárdico intersticial, não apresentou correlação nas duas etiologias.

Assim, o remodelamento cardíaco é um mecanismo complexo que participa, isoladamente ou não, da progressão das cardiomiopatias dilatadas e da insuficiência cardíaca. A avaliação isolada da quantidade de colágeno miocárdico intersticial é uma parte desse conjunto, devendo outras variáveis ser avaliadas posteriormente. De modo isolado, o acúmulo de colágeno no interstício miocárdico dos pacientes com cardiomiopatia dilatada idiopática e chagásica não sugere correlação com a sobrevida desse grupo.

Potencial Conflito de Interesses

Declaro não haver conflitos de interesses pertinentes.

Felix José Alvarez Ramires

Rua Manoel da Nóbrega, 518/112

04001-002 – São Paulo, SP

E-mail:

felixjose@cardiol.br

Artigo recebido em 23/05/05; revisado recebido em 23/06/05; aceito em 01/07/05.

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Quantitative morphologic findings of the myocardium in idiopathic dilated cardiomyopathy Am J Cardiol 1983 501 6 51 Schwarz F Mall G Zebe H Blickle J Derks H Manthey J 15. Weber KT, Jalil JE, Janicki JS, Pick R. Myocardial collagen remodeling in pressure overload hypertrophy. Am J Hypertens 1989; 2: 931-40. Myocardial collagen remodeling in pressure overload hypertrophy Am J Hypertens 1989 931 40 2 Weber KT Jalil JE Janicki JS Pick R 16. Weber KT, Brilla CG. Pathological hypertrophy and cardiac interstitium. Circulation 1991; 83: 849-65. Pathological hypertrophy and cardiac interstitium Circulation 1991 849 65 83 Weber KT Brilla CG 17. Jalil JE, Janicki JS, Pick R, Abrahams C, Weber KT. Fibrosis-induced reduction of rndomyocardium in the rat after isoproterenol treatment. Circ Res 1989; 65: 258-64. Fibrosis-induced reduction of rndomyocardium in the rat after isoproterenol treatment Circ Res 1989 258 64 65 Jalil JE Janicki JS Pick R Abrahams C Weber KT 18. 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Functional and histopathologic correlation in patients with dilated cardiomyopathy: an integrated evaluation by multivariate analysis J Am Coll Cardiol 1987 186 92 10 Nakayama Y Shimizu G Hirota Y Original Articles The role of storage of interstitial myocardial collagen on the overlife rate of patients with idiopathic and chagasic dilated cardiomyopathy

OBJECTIVE: To find out whether there is a correlation between a myocardial structural marker and the overlife rate of patients with dilated cardiomyopathy. METHODS: Using endomyocardial biopsy and 2D-echocardiogram, we studied nine patients with no changes in myocardial structure (control) and 45 patients with severe dilated cardiomyopathy of idiopathic etiology (IDCM) and of Chagasic etiology (CDCM). We analyzed the correlation between the quantity of interstitial myocardial collagen (ICVF) and the overlife rates of these patients. We also evaluated the difference in ICVF between these groups and whether fibrosis interfered on the geometry and function of the myocardium. RESULTS: We observed that ICVF was 15 times higher in cardiomyopathy patients than in the control group, but there was no difference in ICVF between CDCM and IDCM (*p < 0.001) patients. There was no correlation between ICVF and the overlife rate in cardiomyopathy patients (IDCM p = 0.249, and CDCM p = 0.587). We observed a significant correlation between ICVF and left ventricular ejection fraction (LVEF) only for IDCM. There was no correlation between ICVF and left ventricular diastolic diameter in either etiology. CONCLUSION: There was no difference in myocardial fibrosis between patients with CDCM or IDCM, and there was no correlation between fibrosis and the prognosis either for IDCM or CDCM. There was a correlation between myocardial fibrosis and LVEF only for IDCM.

 Collagen myocardium prognosis dilated cardiomyopathy

ORIGINAL ARTICLE

The role of storage of interstitial myocardial collagen on the overlife rate of patients with idiopathic and Chagasic dilated cardiomyopathy

Vera Lopes Nunes; Felix José Alvarez Ramires; Walace de Souza Pimentel; Fábio Fernandes; Barbara Maria Ianni; Charles Mady

Instituto do Coração do Hospital das Clínicas – FMUSP, São Paulo, SP, Brazil

Mailing Address

ABSTRACT

OBJECTIVE: To find out whether there is a correlation between a myocardial structural marker and the overlife rate of patients with dilated cardiomyopathy.

METHODS: Using endomyocardial biopsy and 2D-echocardiogram, we studied nine patients with no changes in myocardial structure (control) and 45 patients with severe dilated cardiomyopathy of idiopathic etiology (IDCM) and of Chagasic etiology (CDCM). We analyzed the correlation between the quantity of interstitial myocardial collagen (ICVF) and the overlife rates of these patients. We also evaluated the difference in ICVF between these groups and whether fibrosis interfered on the geometry and function of the myocardium.

RESULTS: We observed that ICVF was 15 times higher in cardiomyopathy patients than in the control group, but there was no difference in ICVF between CDCM and IDCM (*p < 0.001) patients. There was no correlation between ICVF and the overlife rate in cardiomyopathy patients (IDCM p = 0.249, and CDCM p = 0.587). We observed a significant correlation between ICVF and left ventricular ejection fraction (LVEF) only for IDCM. There was no correlation between ICVF and left ventricular diastolic diameter in either etiology.

CONCLUSION: There was no difference in myocardial fibrosis between patients with CDCM or IDCM, and there was no correlation between fibrosis and the prognosis either for IDCM or CDCM. There was a correlation between myocardial fibrosis and LVEF only for IDCM.

Key words: Collagen, myocardium, prognosis, dilated cardiomyopathy.

Dilated cardiomyopathy represents 87% of cardiomyopathies. Idiopathic dilated cardiomyopathy (IDCM) has an indeterminate origin, once secondary causes are ruled out. In the United States, its incidence is estimated at 5 to 8/100,000 inhabitants in the population in general, which represents one fourth of dilated cardiomyopathies, with a prevalence adjusted for age of 36/100,000 of the population in general, a 5-year overlife rate of 25% to 65%, depending on the stage of the disease, and annual mortality of 10,000 cases1-4. Chagasic dilated cardiomyopathy (CDCM) is considered an inflammatory disease secondary to infection by a parasite, Trypanosoma cruzi. Data of the World Health Organization show that approximately ninety million people are exposed to the risk of infection by Trypanosoma cruzi, in that the incidence of such infection in 1995 was of 120,000 new cases5.

Irrespective of the etiology, there is accumulation of collagen in the interstitium and in the perivascular space of the myocardium. Myocardial collagen is known to perform important functions which directly affect the heart's morphology, geometry and functional performance. Shirey et al6, when studying cardiomyopathy patients, demonstrated for the first time that an increase in myocardial fibrosis was found in patients with the highest mortality. Schwarz et al7 and Figulla et al8, in turn, studied patients with dilated cardiomyopathy, and did not demonstrate a relation between morphological data, such as hypertrophy of cardiomyocytes and increase in the quantity of interstitial collagen, and prognosis information.

Clinical, functional and biochemical markers of prognosis in dilated cardiomyopathies and heart failure (HF) are well defined. However, a histological marker has not been established yet. It is therefore important to assess the role of interstitial myocardial collagen as a structural prognostic marker in dilated cardiomyopathies. Therefore, our hypothesis is that the quantity of interstitial myocardial collagen plays a relevant role, whether or not it depends on the ventricular function, in the overlife of patients with idiopathic and Chagasic dilated cardiomyopathy.

Our objectives were to assess if there is a correlation between the quantity of interstitial myocardial collagen and the overlife rate of patients with severe idiopathic and Chagasic dilated cardiomyopathy; to verify if the quantity of myocardial interstitial collagen differs in cardiomyopathies of Chagasic and idiopathic etiologies; to correlate the quantity of interstitial myocardial collagen with the left ventricle ejection fraction (LVEF) and the diastolic diameter of the left ventricle (LVDD).

Methods

After the approval of the Institution's Ethics Committee (Resolution of the National Council of Health 196/96 of September 10 1996), the diagnosis of patients who underwent endomyocardial biopsy between 1981 and 1998 were reviewed, based on the records of myocardial biopsies and on the hospital's records. Upon exclusion of those who came for follow-up of heart transplants, a total of 1,406 cases were found. Of these, we selected the cases with a diagnosis of idiopathic (n = 116) and Chagasic (n = 126) dilated cardiomyopathy. After the application of inclusion and exclusion criteria, 19 patients with idiopathic dilated cardiomyopathy and 26 with Chagasic dilated cardiomyopathy were included in the study.

The diagnosis of cardiomyopathies followed the criteria established by the World Health Organization/International Society and Federation of Cardiology9. Idiopathic dilated cardiomyopathies are those of unknown cause, after the exclusion of secondary causes such as arterial hypertension; coronary, valve and congenital diseases; myocarditis; pulmonary hypertension, and enlargement restricted to the right ventricle.Chagasic dilated cardiomyopathy is defined as an inflammatory disease of the myocardium associated with myocardial dysfunction, secondary to the infection by Trypanosoma cruzi diagnosed by means of positive serology (immunofluorescence and complement fixation reaction). Information on the deaths were obtained in the hospital records, death certificates, telephone calls to family members and patients' hospital records.

The inclusion criteria were: the use of angiotensin conversion enzyme inhibitors at least four months before the endomyocardial biopsy and during follow-up; normal kineto coronary angiography in the idiopathic group and in those with more than two risk factors for coronary disease in the Chagasic group; positive serology for Chagas' disease (immunofluorescence and complement fixation reaction) or negative serology in the idiophatic group; echocardiogram report issued within two months of the endomyocardial biopsy, with LVEF lower or equal to 0.40 by the Teichholz method.

The exclusion criteria were: ischemic cardiomiopathy, ruled out by a kineto coronary angiography; systemic arterial hypertension and other heart diseases other than the ones studied10,11; renal failure, defined as serum creatinine levels > 2.0 mg/dl; patients who had undergone heart transplant and/or cardiomyoplasty; and patients without outpatient follow up.

The study began with the performance of the endomyocardial biopsy and ended with the patient's death or follow up of patient until July 2003.

In order to compare the results on the quantity of myocardial interstitial collagen with LVDD and LVEF echocardiographic data, we formed a control-group with 9 patients of which 8 had an indication for surgical revascularization of the myocardium and one for excision of a myxoma in the left atrium. The following exclusion criteria were applied: previous myocardial infarction, ventricular dysfunction, primary valvulopathy and arterial pressure measurement higher or equal to 140/90 mmHg measured in more than two instances.

Echocardiogram - An echocardiogram with the M (unidimensional) and bidimensional modes and with the Doppler technique was performed in all patients within two months after the endomyocardial biopsy. These tests were performed according to the recommendations of the American Society of Echocardiography; the LVDD measure (in millimeters) was obtained at the end of diastole and the calculation of the ventricular function was evaluated by the LVEF, obtained with the Teichholz method.

Endomyocardial biopsy - Patients were submitted to endomyocardial biopsy of the right ventricle according to the techniques described by Mason12. The fragments of the control group were obtained during the heart surgery approximately in the same regions of the inter-ventricular septum from which fragments are obtained via percutaneous biopsy.

Collagen morphometry - From the paraffin blocks, new 5 µm sections were placed on blades and stained with picrosirius-red to detect and quantify interstitial collagen. The interstitial collagen volumetric fractions (ICVF) were quantified by videomorphometry, using an image analysis system (Quantimet 520 Image Analysis System-Cambridge Instruments, Cambridge, UK). The morphometry was performed by two observers who were not aware of the clinical picture of the patients. Each parameter represents the mean value of all the measurements obtained in the biopsy of each tissue.

Statistical analysis - The analysis of overlife rates was performed using the Kaplan-Meier method. The curves were compared using the log-rank test. We calculated Pearson's correlation coefficient (r), and performed the analysis of variance (ANOVA) and the Kruskal-Wallis test (when the variances were not homogeneous) for comparisons. The Tukey-HSD test was employed for multiple comparisons. The results were considered statistically significant when p < 0.05, and the values were expressed in terms of mean and standard deviation.

Results

Demographic aspects - We studied 19 patients with idiopathic dilated cardiomyopathy, 26 patients with Chagasic dilated cardiomyopathy; the other 9 patients formed the control group (tab.I). We observed a prevalence of male patients in the three groups. The control group comprised older individuals, while cardiomyopathy patients had on average the same age. The overlife of control group patients was not analyzed, since these patients presented different conditions. The overlife of cardiomyopathy patients was higher in the idiopathic group and ranged from 5 to 2,281days (761 ± 165), while the Chagasic patients had an overlife rate between 6 and 2,166 days (422 ± 109), but with no statistical significance (p = 0.145) (tab.1).

Echocardiographic aspects - The LVDD and LVEF parameters were analyzed. The LVDD mean values found in cardiomyopathy patients were higher than those of the control group (p < 0.001), in that the mean value was higher in IDCM patients than in CDCM (p = 0.005) patients (tab.2). As for LVEF values, they were lower in the groups of cardiomyopathy patients than in the control group (p < 0.001) as shown in table 2.

Overlife analysis - As regards the etiology of cardiomyopathies, there was no statistically significant difference between the 5-year global survival rates in patients with Chagasic cardiomyopathy (3.8%) and in those with idiopathic cardiomyopathy (10.5%) (p = 0.131) (fig.1).

The LVDD was assessed through its median (73 mm). There was no statistically significant difference in the 5-year global overlife rates in CDCM patients with LVDD < 73 (5.3%) or > 73 (0.0%) (p = 0.246), and the same stands for IDCM patients with LVDD < 73 (0.0%) or > 73 (16.7%) (p = 0.269).

As regards LVEF, there was no statistically significant difference between the 5-year global overlife rates for CDCM patients with LVEF < 0.30 (0.0%) or > 0.30 (7.7%) (p = 0.391). However, in the IDCM group, this relation showed a lower overlife rate for patients with lower LVEF (LVEF < 0.30; 0.0%) or > 0.30 (20.0%) (p = 0.031) (fig.2).

Morphometry of collagen - We observed an increase in the quantity of interstitial myocardial collagen in the groups of cardiomyopathy patients as compared to the control group (p < 0.001), but this difference was not significant at comparison of the two etiologies (p = 0.724) (figs.3 and 4).

Correlations with ICVF - When we analyzed the relation between ICVF and the 5-year global overlife rate of patients with IDCM and CDCM, there was no statistically significant difference. We analyzed this dissociation as regards the ICVF median < 5.53 (8.7%) or > 5.53 (4.5%) (p = 0.749) (fig.5). When we separated patients according to the etiology of their cardiomyopathies and correlated ICVF with the overlife rate, we found no statistically significant difference in the 5-year global overlife rates for patients with ICVF < 5.53 (0.0%) or > 5.53 (7.7%) (p = 0.587) for both the Chagasic group (fig.6) and the idiopathic group with ICVF < 5.53 (20.0%) or > 5.53 (0.0%) (p = 0.249) (fig.7).

When we analyzed ICVF and LVEF we didn't observe a correlation in the CDCM group (r = 0.10 ; p = 0.61), but there was a positive linear correlation in IDCM patients (r = 0.50; p = 0.02) (fig.8). There was no correlation between ICVF and LVDD in either etiology.

Discussion

At present, dilated cardiomyopathies are not considered just a myocardial contractility disorder, but a complex sequence of events and mediators which changes the myocardium's cellular and molecular components. These answers, from the histological point of view, are limited and characterized by hypertrophy, degeneration, atrophy and necrosis of cardiomyocytes, loss of myofibrils, inflammatory interstitial infiltrate and interstitial and perivascular fibrosis. In non-physiological hypertrophy of the left ventricle, there is a progressive, unlimited and disproportionate increase in the quantity of collagen, which changes the rearrangement of myocardial cells. This new architecture of the myocardium affects the production of the contraction force and leads to systolic dysfunction and to the onset of HF symptoms13-19.

Although our results do not define that the quantity of interstitial myocardial collagen is related to the overlife of the patients with dilated cardiomyopathy studied (p = 0.749), even after they were separated according to the Chagasic etiology (p = 0.587) and idiopathic etiology (p = 0.249), we observe that those patients with dilated cardiomyopathy with the smallest quantity of interstitial myocardial collagen had a 5-year global overlife rate of 8.7%, as compared to 4.5% for patients with the greatest quantity of interstitial myocardial collagen. These results corroborate the data presented by Unverferth et al20, for patients with non-ischemic dilated cardiomyopathy, in which they observed that those who didn't survive had the greatest amount of fibrosis, although without prognostic importance (p = 0.26). When the two etiologies are compared as regards the overlife rates, the results are also not significant, but we observed that the Chagasic etiology presented a 5-year overlife rate of 3.8%, while the idiopathic etiology presented a overlife rate of 10.5%. Perhaps the persistence of the activity of myocarditis, whether due to the direct participation of the parasite or due to immunological mechanisms, in addition to the diffused distribution of histological lesions have somehow contributed to the more adverse progression of Chagasic patients.

The quantitative measure of interstitial myocardial collagen taken in isolation fails to express all the complexity of myocardial remodeling. Perhaps, in order to demonstrate the relationship between remodeling and overlife, we should include other changes in the analysis, changes which play a role in the architecture of the myocardium, such as the type of distribution of collagen fibers (diffused or localized) in the myocardium, its relation with the cardiomyocytes and with their alignment, the formation of collagen clusters in the myocardium, which work as true obstacles in the transmission of the contraction force generated for the whole cardiac chamber, the loss of integrity, thus leading to a de-synchronized contraction of the myocardium, leading to a decrease in the systolic function16,21-23. In addition to these factors, the remodeling of the myocardium also causes changes in cells and molecules, causing hypertrophy and perhaps hyperplasia, necrosis and apoptosis of cardiomyocytes.

In our study, the results of morphometry in the quantification of myocardial interstitial collagen in patients with Chagasic dilated cardiomyopathy were not different from the results obtained in the idiopathic group, but were, on average, fifteen times higher than those found in the control group patients.

Verifying whether there is a relationship between the increase in the quantity of interstitial myocardial collagen and the changes in the myocardium function is relevant. Mady et al24, in patients with Chagasic dilated cardiomyopathy; Weber et al15,16 and Jalil et al22, in animal models of left ventricle hypertrophy, related the increase in the quantity of collagen in the myocardium, usually in excess of 20% of its normal value, with a decrease in the myocardium's efficacy in generating force. Nakayama et al25, in turn, observed that interstitial myocardial fibrosis and cardiomyocyte hypertrophy correlated, and were associated with the decrease in myocardium contractility in patients with dilated cardiomyopathy. In our analysis, when we correlated the quantity of interstitial myocardial collagen for CDCM patients with LVEF, we did not observe a correlation. However, when we correlated these two variables for IDCM patients, we observed a significant correlation. This fact could be related to factors which are typical of the physiopathology of the myocardial function, and may have greater relevance in the role of inflammatory mediators in CDCM, since the accumulation of collagen is not the major cause of this dysfunction. LVEF presented no relation with the global overlife of patients with Chagasic dilated cardiomyopathy, but presented a relation with the global overlife of idiopathic cardiopathy patients. This may have happened because of the involvement of other physiopathological mechanisms in Chagasic cardiomyopathy, such as the greater release of inflammatory mediators, the persistence of the parasite, which increases the local inflammatory response and the activation of autoimmune mechanisms, thus further worsening the myocardium function, in addition to the worsening caused by the accumulation of collagen. Unverferth et al20 observed that, in addition to the LVEF, the LVDD is also an important factor in the prognosis of cardiomyopathies. Therefore, LVDD, a measure with significantly different values for the three groups of patients studied when the quantities of interstitial myocardial collagen are compared, we found no correlation in the two etiologies.

Therefore, cardiac remodeling is a complex mechanism that plays a role, whether in isolation or not, in the progression of dilated cardiomyopathies and heart failure. The isolated assessment of the quantity of interstitial myocardial collagen is a part of this set, and other variables should be further assessed. Taken in isolation, the accumulation of collagen in the interstitium of the myocardium of patients with idiopathic and Chagasic dilated cardiomyopathy does not suggest any correlation with the survival of this group.

Potential Conflict of Interest

No potential conflict of interest relevant to this article was reported.

References

Felix José Alvarez Ramires

Rua Manoel da Nóbrega, 518/112

04001-002 – São Paulo, SP, Brazil

E-mail:

felixjose@cardiol.br

Manuscript received May 23, 2005; revised manuscript received June 23, 2005; accepted July 01, 2005.