of patrilineal descent. her children should she have had them and the following kings were also Vasa's, simply of matrilineal descent. Any children of Christina's would still be seen as a continuation of the Vasa lineage, since they would be the ones eligible to succeed her...Just as Karl X her cousin was also her most direct heir, simply in the female line. He had as much Vasa lineage in him as her. Just as all people are the product of two lineages.
It would be a hybrid line probably of the Hapsburg - Lorraine model, who were easily still seen as part of the Hapsburg dynasty to the end. The last king of Vasa lineage is of course Carl XIII, through a second successive female line....But still of Vasa lineage.