"Análise temporal do acúmulo de sódio no miocárdio de cães avaliado in vivo por ressonância magnética durante oclusão e reperfusão coronária" / Time course of myocardial sodium accumulation in dogs evaluated by in vivo magnetic resonance imaging during coronary occlusion and reperfusion.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2002

RESUMO

Loss of membrane permeability caused by ischemia leads to cellular sodium accumulation and myocardial edema. This phenomenon has important implications to left ventricular structure and function in the first hours after myocardial infarction. We hypothesized that during this period of time, after prolonged coronary occlusion and complete reflow, the rate of myocardial sodium accumulation is governed by microvascular integrity. We used 3-dimensional 23 Na magnetic resonance imaging to monitor myocardial sodium content changes over time in an in vivo closed-chest canine model (n = 19) of myocardial infarction and reperfusion. Six animals had ventricular fibrillation during occlusion or immediately after coronary reperfusion, and did not finish the protocol. Myocardial infarction was not detected in four experiments, by any of utilized methods. In one experiment, we produced permanent coronary occlusion. The remaining eight animals constituted the reperfused myocardial infarction group. From those, infarcts with microvascular obstruction n = 4) defined by both radioactive microsphere and contrast-enhanced 1 H magnetic resonance imaging showed a slower rate of sodium accumulation as well as lower blood flow at 20 minutes and 6 hours after reperfusion. Conversely, the absence of microvascular obstruction (n = 4) was associated with faster rates of sodium accumulation and greater blood flow restoration. In addition, infarct size by 23 Na magnetic resonance imaging correlated best with infarct size by triphenyltetrazolium chloride and contrast-enhanced 1 H magnetic resonance imaging at 9 hours after reperfusion. We conclude that in reperfused myocardial infarction, sodium accumulation is dependent on microvascular integrity and is slower in regions of microvascular obstruction compared with those with patent microvasculature. Finally, 23 Na magnetic resonance imaging can be a useful tool for monitoring in vivo myocardial sodium content in acute myocardial infarction.

ASSUNTO(S)

coronary disease/diagnosis myocardial infarction/physiopathology myocardial ischemia/physiopathology sodium/analysis coronary circulation dogs sódio/análise circulação coronária coronariopatia/diagnóstico isquemia miocárdica/fisiopatologia time factors infarto do miocárdio/fisiopatologia reperfusão miocárdica fatores de tempo cães myocardial reperfusion magnetic resonance spectroscopy/diagnostic use ressonância magnética nuclear/uso diagnóstico

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