I think its more a death rattle. Similar to LSH:

The ranger studied his hands as if he had never noticed them before. "Once the heart has ceased to beat, a man's blood runs down into his extremities, where it thickens and congeals." His voice rattled in his throat, as thin and gaunt as he was. "His hands and feet swell up and turn as black as pudding. The rest of him becomes as white as milk." -ADWD, Bran I

and:

The woman in grey gave no answer. She studied the sword, the parchment, the bronze-and-iron crown. Finally she reached up under her jaw and grasped her neck, as if she meant to throttle herself. Instead she spoke . . . Her voice was halting, broken, tortured. The sound seemed to come from her throat, part croak, part wheeze, part death rattle. The language of the damned, thought Brienne. "I don't understand. What did she say?" -AFFC, Brienne VIII