CIGNA HealthCare and Eastern Connecticut Health Network have reached an agreement that will allow thousands of patients to continue using Manchester and Rockville hospitals and affiliated doctors instead of having to find new ones. The agreement in principle, coming just three weeks before the old contract expires, resolves a dispute over reimbursement offered by CIGNA. The accord "will more appropriately reimburse ECHN for the healthcare services we provide to those covered by CIGNA," said Peter Karl, president and chief executive of ECHN.