There is some concern people with high blood pressure practicing poses that are inverted as in downward facing dog. There are some conflicting responses. It is important to check with your doctor if you have any questions. It is also important as always to listen to your body while you complete inverted poses. Modifications can be made such as slowly coming out of a forward bend to allow for your body to adjust to the change.
Some websites for further research:
http://www.yogajournal.com/practice/594 Well written.
I enjoy yoga as it brings peace to my life. Teaching yoga has brought joy to my life and given me a chance to encourage others in learning yoga.