Successful treatment of coronary artery vasospasm in Sur2–/– mice with nifedipine. (a) Representative continuous ECG recordings obtained during subcutaneous infusion of a sham-infusate (saline or DMSO) versus nifedipine at 3 mg/kg/d. Tracings depict heart rate, with sharp downward deflections representing deceleration in the heart rate or episodic bradycardia. Graphic summary of quantitative decrease of (b) ST segment elevation events per 24-hour period, and (c) heart block episodes per 24-hour period (n = 5 each). White bars represent sham-infusate group. Black bars represent nifedipine group. *,**P < 0.0001 by two-tailed, unpaired Student t test.