These are the Rebbe's letters to individuals about their own situations. Throughout, the Rebbe instructed people to consult an expert doctor and follow his guidance; anyone facing a medical question should do the same.
The Rebbe's guidance on high blood pressure:
Blood pressure depends largely on one's emotional state and mood, as the doctors themselves say, so avoiding agitation is a proven remedy. Distraction also lowers it considerably, and doctors will confirm that many people live long lives with higher-than-normal readings (IK 1904, 4382, 7052).
To reach that calm, study the Alter Rebbe's Iggeres HaKodesh (the fourth section of Tanya) carefully (IK 1904). Following the Baal Shem Tov's teaching to help the body with joy and gladness brings health (IK 4382).