Thanks for your question on HCM. Both tests are different. Thallium stress test is non invasive test and it detects viability of myocardium, in simple words it gives you idea about your heart muscle weather live or dead. It will not give any idea about coronaries and the percentage of blockage. Angiography is invasive procedure (day care) which gives you clear cut idea about coronaries and its blockage. It will also tell you about collateral circulation formed or not. So in my opinion if your mother s stress test is positive go for angiography. It is invasive procedure but will give you all the answers about you mother s cardiac status.