This is a different type of angina - most of us probably have not experienced and Nitro does not relieve the pain in this type.
"Temporary Nerve Block Controls Heart Pain"
"Using local anesthetics to temporarily block nerve signals from the heart is a safe and effective treatment for chronic refractory angina, a painful condition resulting from inadequate blood flow to the heart, new research suggests. One injection provides about 3 weeks of relief."
http://www.nlm.nih.gov/medlineplus/news/fullstory_27150.html