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Cardiografia de impedância na avaliação de disfunção diastólica do ventrículo esquerdo em doentes com hipertensão arterial
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RESUMO: A cardiografia de impedância é um exame complementar de diagnóstico de
fácil execução e não dependente do operador, já utilizado no estudo da hipertensão
arterial e na otimização da terapêutica anti-hipertensora, com boa relação
custo-eficácia. Trata-se de uma técnica que evoluiu muito nos últimos anos
tornando-se um meio atrativo e económico para mudar a nossa abordagem clínica
ao doente hipertenso. No entanto, faltam ensaios clínicos capazes de gerar
consenso quanto ao seu real valor e aplicabilidade na prática clínica, justificando
a sua utilização em larga escala.
A hipertensão arterial é responsável por elevada morbilidade e mortalidade.
A sua progressão para insuficiência cardíaca envolve o desenvolvimento de disfunção
diastólica, geralmente avaliada por ecocardiografia, um exame moroso,
tecnicamente exigente e que requer um operador experiente. Estas exigências,
têm limitado o seu uso no rastreio de disfunção diastólica e, consequentemente, a
nossa compreensão da sua evolução e resposta a terapêutica. Assim, propusemonos
a estudar o potencial da cardiografia de impedância para rastreio de disfunção
diastólica do ventrículo esquerdo comparando-a com o método atualmente utilizado
para esse efeito na prática clínica habitual – a ecocardiografia transtorácica.
Para cumprirmos o objetivo definido, estudámos uma população de 157 doentes
de ambulatório, recrutados de consultas de hipertensão arterial e risco
vascular de um centro hospitalar terciário, que foram submetidos sistematicamente
a ecocardiografia transtorácica e cardiografia de impedância em posição
supina e ortostática. Foram recrutados doentes com hipertensão avançada, sem
história ou evidência de outras comorbilidades cardiovasculares, nomeadamente sem insuficiência cardíaca, cardiopatia isquémica, valvulopatia, disritmia, entre
outras. Para além disso, estudámos a concordância entre os valores obtidos pelas
duas técnicas e determinámos as variáveis associadas a disfunção diastólica do
ventrículo esquerdo.
O presente estudo permitiu-nos chegar a várias conclusões:
A cardiografia de impedância na posição supina pode ser usada com precisão
para o rastreio de disfunção diastólica do ventrículo esquerdo em
doentes hipertensos recomendando-se, para tal, a utilização do parâmetro
rácio de tempo sistólico;
Os intervalos de tempo sistólico, débito cardíaco e índice cardíaco avaliados
por cardiografia de impedância na posição supina apresentam boa concordância
com o ecocardiograma transtorácico. Por outro lado, a comparação
entre o a cardiografia de impedância na posição ortostática e o ecocardiograma
realizado na posição supina apresentou dispersão dos resultados
obtidos, refletindo a variabilidade da resposta dos parâmetros hemodinâmicos
à alteração postural;
No que concerne os fatores associados ao desenvolvimento de disfunção
diastólica do ventrículo esquerdo, concluímos que a hipertensão nãocontrolada
ou de longa evolução, a hipertrofia excêntrica do ventrículo
esquerdo e o tabagismo foram fatores determinantes para a ocorrência de
disfunção diastólica do ventrículo esquerdo na nossa amostra de doentes;
a remodelagem concêntrica do ventrículo esquerdo mostrou-se protetora.
Tendo definido a cardiografia de impedância como exame útil no rastreio de
disfunção diastólica do ventrículo esquerdo, este exame pode emergir como uma
ferramenta útil na prática clínica, nomeadamente no acompanhamento de doentes
com hipertensão não-controlada ou resistente. Será importante, no futuro,
compreender a evolução da disfunção diastólica e demonstrar que a deteção precoce
de disfunção diastólica e tratamento das alterações hemodinâmicas poderá
ser benéfico na evolução da cardiopatia hipertensiva e, eventualmente, reduzir a
morbilidade e mortalidade associadas.
ABSTRACT: Impedance cardiography is an easy, non-operator dependent and cost-effective diagnostic test, already used in the study of arterial hypertension and antihypertensive therapy optimization. It’s a technique that has evolved in recent years, becoming an attractive and economical way to change our clinical approach to the hypertensive patient. However, there is a lack of clinical trials able to generate consensus on their real value and applicability in clinical practice, justifying its large-scale use. Hypertension is responsible for high morbidity and mortality. Its progression to heart failure involves the development of diastolic dysfunction, usually evaluated by echocardiography, a time-consuming and technically demanding examination, demanding an experienced operator. These requirements have limited its use in the screening of diastolic dysfunction and hence our understanding of diastolic dysfunction evolution and response to therapy. Thus, we proposed to study the impedance cardiography potential for left ventricular diastolic dysfunction screening, comparing it with the currently used method for this effect in routine clinical practice – the transthoracic echocardiography. To reach the defined objective, we studied a population of 157 outpatients recruited from arterial hypertension and vascular risk consultations of a tertiary hospital, who were systematically submitted to transthoracic echocardiography and impedance cardiography in the supine and orthostatic position. Patients with advanced hypertension without history or evidence of other cardiovascular comorbidities, including without heart failure, ischemic heart disease, valvulopathy, dysrhythmia, among others, were recruited. In addition, we studied the agreement between the values obtained by the two techniques and determined the variables associated with left ventricular diastolic dysfunction. The present study allowed us to reach several conclusions: Impedance cardiography in supine position can be used with precision for the screening of left ventricular diastolic dysfunction in hypertensive patients. We recommended the use of the parameter systolic time ratio; The systolic time intervals, cardiac output and cardiac index evaluated by impedance cardiography in the supine position show good agreement with transthoracic echocardiography. On the other hand, the comparison between the impedance cardiography in the orthostatic position and the supine echocardiography showed a dispersion of the results obtained, reflecting the variability of the hemodynamic parameters response to postural change; Regarding the factors associated with the development of left ventricular diastolic dysfunction, we concluded that uncontrolled or long-term hypertension, left ventricular eccentric hypertrophy and smoking were determining factors for the occurrence of left ventricular diastolic dysfunction in our sample; left ventricle concentric remodeling was a protective factor. Having defined impedance cardiography as an useful exam in left ventricular diastolic dysfunction screening, it may emerge in clinical practice, particularly in the follow-up of patients with uncontrolled or resistant hypertension. It will be important, in the future, to understand the evolution of diastolic dysfunction and to demonstrate that its early detection and treatment of hemodynamic changes may be beneficial in the evolution of hypertensive cardiopathy and possibly reduce the associated morbidity and mortality.
ABSTRACT: Impedance cardiography is an easy, non-operator dependent and cost-effective diagnostic test, already used in the study of arterial hypertension and antihypertensive therapy optimization. It’s a technique that has evolved in recent years, becoming an attractive and economical way to change our clinical approach to the hypertensive patient. However, there is a lack of clinical trials able to generate consensus on their real value and applicability in clinical practice, justifying its large-scale use. Hypertension is responsible for high morbidity and mortality. Its progression to heart failure involves the development of diastolic dysfunction, usually evaluated by echocardiography, a time-consuming and technically demanding examination, demanding an experienced operator. These requirements have limited its use in the screening of diastolic dysfunction and hence our understanding of diastolic dysfunction evolution and response to therapy. Thus, we proposed to study the impedance cardiography potential for left ventricular diastolic dysfunction screening, comparing it with the currently used method for this effect in routine clinical practice – the transthoracic echocardiography. To reach the defined objective, we studied a population of 157 outpatients recruited from arterial hypertension and vascular risk consultations of a tertiary hospital, who were systematically submitted to transthoracic echocardiography and impedance cardiography in the supine and orthostatic position. Patients with advanced hypertension without history or evidence of other cardiovascular comorbidities, including without heart failure, ischemic heart disease, valvulopathy, dysrhythmia, among others, were recruited. In addition, we studied the agreement between the values obtained by the two techniques and determined the variables associated with left ventricular diastolic dysfunction. The present study allowed us to reach several conclusions: Impedance cardiography in supine position can be used with precision for the screening of left ventricular diastolic dysfunction in hypertensive patients. We recommended the use of the parameter systolic time ratio; The systolic time intervals, cardiac output and cardiac index evaluated by impedance cardiography in the supine position show good agreement with transthoracic echocardiography. On the other hand, the comparison between the impedance cardiography in the orthostatic position and the supine echocardiography showed a dispersion of the results obtained, reflecting the variability of the hemodynamic parameters response to postural change; Regarding the factors associated with the development of left ventricular diastolic dysfunction, we concluded that uncontrolled or long-term hypertension, left ventricular eccentric hypertrophy and smoking were determining factors for the occurrence of left ventricular diastolic dysfunction in our sample; left ventricle concentric remodeling was a protective factor. Having defined impedance cardiography as an useful exam in left ventricular diastolic dysfunction screening, it may emerge in clinical practice, particularly in the follow-up of patients with uncontrolled or resistant hypertension. It will be important, in the future, to understand the evolution of diastolic dysfunction and to demonstrate that its early detection and treatment of hemodynamic changes may be beneficial in the evolution of hypertensive cardiopathy and possibly reduce the associated morbidity and mortality.
Descrição
Palavras-chave
Hipertensão Disfunção diastólica Cardiografia de impedância Bioimpedância torácica Hypertension Diastolic dysfunction Impedance cardiography Thoracic bioimpedance