My Heart Has Been Racing Out Of Control, Especially At

My heart has been racing out of control, especially at night when I lay down, for about 6 weeks. The insomnia that comes with it is debilitating. Nothing helps the insomnia, not even Ambien if I take it more than 2 night s in a row. Are heart palpitations a side of effect of Ambien. I have an appt. with a cardiologist tomorrow, but I am wondering if there is anything that can bring down my heart rate today! I feel horrible. Thank you.