The excess risk of shock was highest in the first 2 days of hospitalization, especially in patients with evidence of hemo- dynamic instability or borderline hemodynamics at presenta- tion. In a subset analysis of patients with hypertension (SBP >140 mmHg), there were no statistically significant differ- ences between the -blocker and placebo arms with respect to the composite primary end point, death or cardiogenic shock alone, although there was a trend in favor of the -blocker. This important study demonstrated that early intravenous -blocker therapy should be used selectively and restricted to patients with significant hypertension or tachycardia (ie, caused by atrial arrhythmias), those with ongoing ischemia, and those at low risk for hemodynamic compromise. CurrentACC/AHA guidelines for STEMI and UA/NSTEMI recommend that oral -blockade should be started within the first 24 hours, once it is established that the patient is stable and there are no contraindications.190,195 The choice of a -blocker is based on pharmacokinetic and side-effect criteria and phy- sician familiarity, but in general, short-acting cardioselective -selective) -blockers without intrinsic sympathomimetic activity such as metoprolol or bisoprolol are preferable. Carvedilol, which also blocks 2 adrenergic receptors, has more potent BP-lowering effects than 1 -selective agents and therefore may be a good choice for patients with ACS and severe hypertension. However, it should be avoided in patients with obstructive airways disease because of the effects of 2 antagonism on airway resistance. Contraindications to the use of -blockers in ACS include marked first-degree heart block (ECG PR interval >0.24 second), second- or third-degree heart block, severe bronchospastic lung disease, decompen- sated HF, and hypotension. Several meta-analyses concluded that cardioselective -blockers do not produce clinically sig- nificant adverse respiratory effects in patients with chronic obstructive pulmonary disease, suggesting that -blockers should not be withheld from these patients.196,197 5.3.3. 