Medical School Review Grape Seed Extract lowers blood pressure and heart rate significantly Scientists from School of Medicine in New Haven performed a systematic review of studies assessing the effects of Grape Seed Extract on blood pressure and other cardiovascular risk factors. Nine randomized controlled clinical trials met the inclusion criteria. Grape Seed Extract significantly lowered systolic blood pressure from about -2 to -5 mm Hg on average and lowered the heart rate by -1 to -4 beets per minute.