Out of the box -- there is no CQ integration. However - with CQ - you can build custom services.
Looks like Eloqua supports a Restful API.
http://topliners.eloqua.com/community/code_it/blog/2012/10/14/eloqua-rest-api--getting-started-with-...
You can create a custom AEM service using OSGi that uses these Restful APIs to communicate with Eloqua using Restful requests.
We have a community article that shows how to build a Restful OSGi service (that consumes a third-party service) within CQ:
http://helpx.adobe.com/experience-manager/using/restful-services.html
This article invokes a Google Restful web service as an example. In your use case - you can switch Google Restful service with Eloqua.