See Online Data Supplement 11 for additional information on beta blockers, including risk factors for shock. 4.1.2.4. Calcium Channel Blockers: Recommendations Class I 1. In patients with NSTE-ACS, continuing or frequent- ly recurring ischemia, and a contraindication to beta blockers, a nondihydropyridine calcium channel blocker (CCB) (eg, verapamil or diltiazem) should be given as initial therapy in the absence of clinically significant LV dysfunction, increased risk for cardio- genic shock, PR interval greater than 0.24 second, or second- or third-degree atrioventricular block with- out a cardiac pacemaker.248 250 (Level of Evidence: B) 2. Oral nondihydropyridine calcium antagonists are recommended in patients with NSTE-ACS who have recurrent ischemia in the absence of contra- indications, after appropriate use of beta blockers and nitrates. (Level of Evidence: C) 3. CCBs are recommended for ischemic symptoms when beta blockers are not successful, are contrain- dicated, or cause unacceptable side effects. (Level of Evidence: C) 4. Long-acting CCBs and nitrates are recommended in patients with coronary artery spasm. (Level of Evi- dence: C) Class III: Harm 1. Immediate-release nifedipine should not be adminis- tered to patients with NSTE-ACS in the absence of (Level of Evidence: B) CCBs include dihydropyridines and nondihydropyridines. The dihydropyridines (nifedipine and amlodipine) produce the most marked peripheral vasodilation and have little direct effect on contractility, atrioventricular conduction, and heart rate. The nondihydropyridines (diltiazem and verapamil) have significant negative inotropic actions and negative chronotropic and drom- otropic effects. All CCBs cause similar coronary vasodilation and are preferred in vasospastic angina.253 They also alleviate ischemia due to obstructive CAD by decreasing heart rate and BP. 