"has further heightened" is a perfectly acceptable and usable phrase in written English.
It is often used to describe an increase in intensity or attention. For example, "The announcement of a new potential vaccine has further heightened public interest in the issue."
The rise of the UK Independence Party, which campaigns for cuts to immigration, has further heightened interest in the issue at Westminster.
The emergence of the more virulent 027 strain of C. difficile has further heightened concerns.
The recent global financial crisis has further heightened their vulnerability and deepened poverty.
Transportation and environmental issues are strongly connected, and in recent years legislation at all levels of government has further heightened the links between these issues.
"The recent global financial crisis has further heightened their vulnerability and deepened poverty, as well as worsened economic inequity," he said.
Recent operations by the police and government security forces against Taliban militants have further heightened tensions.
Emerging research on the effects of raised cortisol levels have further heightened parental unease about this subject.
The recently formulated sustainable development goals and global climate agenda have further heightened the urgency for a more holistic and integrated conceptualization of transitioning towards a sustainable low-carbon economy.
Although corruption among the police is rife in China, the disdain has been further heightened by a series of widely publicized episodes involving the torture of detainees, suspects who mysteriously died in custody and innocent people jailed on trumped-up evidence.
Shrewsbury Town's defensive worries have been further heightened by the loss of centre-half Darren Jones for the rest of the season.
The precautions Mr. Giuliani had installed were then further heightened in the aftermath of Sept. 11.
