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Efectos electrofisiológicos del estiramiento miocárdico y determinantes mecánicos de las arritmias activadas por el
Circulation
|September 1, 1992
Resumen
El estiramiento ventricular rápido, no gradual, desencadena arritmias al causar despolarización de la membrana. Este estudio destaca la velocidad del estiramiento como clave para inducir excitaciones ventriculares prematuras (EVP), lo que podría explicar la ectopia en condiciones como el prolapso de la válvula mitral.
Área de la Ciencia:
- Fisiología cardiovascular fisiología cardiovascular.
- Electrofisiología Cardíaca Electrofisiología cardíaca.
- La arritmogénesis es la arritmogénesis.
Sus antecedentes:
- Se conoce la retroalimentación mecanoeléctrica del miocardio, pero los mecanismos de inducción de la arritmia por estiramiento ventricular no están claros.
- El potencial aritmogénico del estiramiento miocárdico crónico versus agudo sigue siendo objeto de debate.
- Los efectos electrofisiológicos celulares del estiramiento miocárdico requieren una evaluación adicional.
Objetivo del estudio:
- Para investigar los efectos electrofisiológicos y aritmogénicos del estiramiento lento versus rápido de la pared ventricular.
- Determinar el papel de la velocidad y amplitud de estiramiento en la inducción de excitaciones ventriculares prematuras (EVP).
Principales métodos:
- Utilizó un modelo aislado de corazón de conejo perfundido por Langendorff con cambios de volumen ventricular izquierdo (LV) controlados por computadora.
- Evalúa la electrofisiología celular y las PVE utilizando grabaciones de potencial de acción monofásico (MAP) en varios sitios y ECG conducidos por volumen.
- Aplicó rampas de volumen graduales y pulsos de volumen rápidos con amplitudes y velocidades de ascenso variables.
Principales resultados:
- La carga LV gradual disminuyó la amplitud MAP; los pulsos rápidos causaron despolarizaciones transitorias.
- El estiramiento rápido desencadenó regularmente PVEs (45-100%), mientras que el estiramiento gradual rara vez lo hizo (11%).
- La probabilidad de EVP aumentó con la amplitud y la velocidad de estiramiento, particularmente en amplitudes más bajas; las EVP se originaron principalmente en el LV posterolateral.
Conclusiones:
- El estiramiento ventricular rápido provoca más fácilmente PVEs que el estiramiento gradual, a pesar de la despolarización de la membrana similar.
- Las regiones miocárdicas con mayor cumplimiento pueden actuar como focos de arritmias activadas por estiramiento.
- Los hallazgos apoyan los canales activados por estiramiento y explican la ectopia ventricular en condiciones de carga ventricular diferencial.
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