Heart Attacks More Likely to Occur in Cold Weather By EMMA ROSS    MUNICH, Germany (AP) -- People with high blood pressure seem to be more vulnerable to heart attacks when the temperature drops, new research shows.    The findings, presented Monday at a conference of the European Society of Cardiology, are not surprising because cold weather makes the blood vessels constrict, making it harder for blood to move through, but the study is the first to document that variations in the weather increase the occurrence of heart attacks in people with high blood pressure...