Some patients have no chest pain but present solely with dyspnea or with arm, shoulder, back, jaw, neck, epigastric, or ear discomfort.107 109 Features not characteristic of myocardial ischemia include: Pleuritic pain (sharp or knifelike pain provoked by res- piration or cough); Primary or sole location of discomfort in the middle or lower abdomen; Pain localized by the tip of 1 finger, particularly at the LV apex or costochondral junction; Pain reproduced with movement or palpation of the chest wall or arms; Brief episodes of pain lasting a few seconds or less; Pain that is of maximal intensity at onset; and Pain that radiates into the lower extremities. Evaluation should include the clinician s impression of whether the pain represents a high, intermediate, or low likeli- hood of acute ischemia. Although typical characteristics increase the probability of CAD, atypical features do not exclude ACS. In the Multicenter Chest Pain Study, acute ischemia was diagnosed in 22% of patients who presented to the ED with sharp or stabbing pain and in 13% of those with pleuritic pain.110 Seven percent of patients whose pain was reproduced with palpation had ACS. The ACI- TIPI (Acute Cardiac Ischemia Time-Insensitive Predictive Instrument) project found that older age, male sex, chest or left arm pain, and chest pain or pressure were the most important findings, and each increased the likelihood of ACS.111,112 The relief of chest pain with nitroglycerin is not predic- tive of ACS. One study reported that sublingual nitroglycerin relieved symptoms in 35% of patients with documented ACS compared with 41% of patients without ACS.113 The relief of chest pain by gastrointestinal cocktails (eg, mixtures of liq- uid antacids, and/or viscous lidocaine, and/or anticholinergic agents) does not predict the absence of ACS.114 3.3.2.2. 