It is a type of abnormal heart rhythm where your heart suddenly beats very fast — often over 150 beats per minute; this can lead to symptoms like chest pain, dizziness, shortness of breath, or fainting.
As PSVT episodes can occur without warning and may last from a few minutes to several hours (sometimes leading to frequent hospital visits), people with PSVT often feel anxious, which affects their daily activities.
Cardamyst works by blocking certain calcium channels in the heart, which slows down electrical signals in a key part of the heart (the atrioventricular node) and relaxes blood vessels. The medicine helps return the heart to a normal rhythm by interrupting abnormal electrical signals that cause rapid heartbeats in individuals with PSVT.
Why Was It Approved?
The FDA’s approval of Cardamyst was based on clinical studies that showed it was well tolerated, safe, and effective in treating people with PSVT and helped in restoring a normal heart rhythm faster than a placebo. The FDA’s approval was also based on a large clinical trial program that included safety data from more than 1,800 participants and over 2,000 PSVT episodes. Key evidence came from a phase 3 trial comparing Cardamyst with a placebo, in which 64% of patients who used the medicine versus 31% of those on the placebo returned to a normal heart rhythm within 30 minutes. Patients using Cardamyst were about twice as likely to return to a normal heart rhythm and did so more than three times faster than those on the placebo (median conversion time, 17 minutes versus 54 minutes). By one hour, 73% of patients treated with Cardamyst had converted to a normal rhythm. Cardamyst worked well even for people already taking other heart medicines such as beta-blockers or calcium channel blockers. The most common side effects reported in the trial were mild and temporary and included nasal discomfort, a stuffy or runny nose, throat irritation, and nosebleeds.
What Do I Need to Know?
You use Cardamyst at the first sign of a PSVT episode. Follow the instructions on how to use Cardamyst, and spray it once in each nostril for a full dose. If your symptoms don’t improve after 10 minutes, you can take a second dose the same way with a new Cardamyst device. Don’t take more than two doses in a 24-hour period. You should stay seated while using it and keep your head straight for 10 minutes as it may cause dizziness or fainting. In case you feel dizzy, lie down right away. You should not use Cardamyst if you have certain heart rhythm problems such as Wolff-Parkinson-White syndrome, Lown-Ganong-Levine syndrome, or an abnormal heart rhythm called pre-excitation (delta wave) on an ECG; moderate-to-severe heart failure; sick sinus syndrome without a permanent pacemaker; moderate or severe heart block; or an allergic reaction to Cardamyst or any of its ingredients. Tell your health care provider if you have a history of fainting or low blood pressure. Also let them know about all other medicines you take, including over-the-counter products, herbal remedies, vitamins, and health supplements.
