St. John's Wort & Kava Kava for PMS

I have been advised by my gynaecologist to take St. John's Wort or KavaKava for PMS symptoms. I have had problems with rapid heart beats and palpitations in the past. Do either of these herbs affect the heart beat? What is the recommended dosage of each for PMS?

St. John's Wort or Kava Kava might be recommended for promoting sleep, calming nerves, lifting mood and relieving cramps in PMS. Neither are contraindicated in heart disease. They work on the nervous system to achieve calming effects. If your palpitations are due to anxiety, these preparations may help to calm them. Because of its longer use and known effects in western herbal medicine, I would recommend St. John's Wort.
Dosages will vary according to the preparation. I recommend asking at a health food store for suggestions on a reliable brand, and following the recommended dosage on the bottle. Kava Kava dosage is 2 - 4 grams of powder or one half to one teaspoon of liquid extract, three times daily. St. John's Wort dosage is 2 to 4 grams of dried herb, 2 to 4 ml of tincture or 20 to 60 drops of liquid extract, three times daily.