EKGs in PE
                                ==========
þ Pulmonary Embolism Simulating Acute Coronary Syndrome 
 - Typical ECG findings 
  + S1Q3 or S1Q3T4 
  + RBBB or incomplete RBBB (often transient) 
  + Rightward axis 
  + T-wave inversions, especially in right precordial leads (V1-V3) +/- 
    inferior leads 
 - Marriott and others: 
  + combination of T-wave inversions in right precordial and inferior leads 
    is highly specific for acute pulmonary hyptertension, pulmonary 
    embolism 
 - May also (less commonly) cause 
  + ST-segment depression or elevation in right precordial leads 
  + ST-segment depression in leads I or II 
  + ST-segment elevation in lead III 
 - Important point: PE often causes ECG changes that resemble cardiac ischemia 
 - Don't just "rule out MI" when the EKG seems to show cardiac iscnemia
 - Recent study shows inferior + anterior T inversions 99% specific for PE
   [Kosuge, M., K. Kimura, et al. (2007). "Electrocardiographic 
   differentiation between acute pulmonary embolism and acute 
   coronary syndromes on the basis of negative T waves." Am J 
   Cardiol 99(6): 817-21.
   Negative T waves in precordial leads are often seen in 
   patients with acute coronary syndrome (ACS), but also occur in 
   those with acute pulmonary embolism (APE). However, little 
   attention has been given to differences in negative T waves 
   between patients with these 2 diseases. The present study 
   examines the value of electrocardiograms for discriminating 
   between 40 patients with APE and 87 patients with ACS who had 
   negative T waves in the precordial leads (V(1) to V(4)) on the 
   admission electrocardiogram. In 77 patients (89%) with ACS, 
   the culprit lesion was confirmed angiographically to be 
   located in the left anterior descending coronary artery. 
   Pulmonary P waves, S(1)S(2)S(3) pattern, S(1)Q(3)T(3) pattern, 
   low voltage, and clockwise rotation were specific for APE, but 
   sensitivities of these findings were very low. In patients 
   III, aVF, V(1), and V(2), but were less frequent in leads I, 
   and V(1) were observed in only 1% of patients with ACS 
   compared with 88% of patients with APE (p <0.001). The 
   sensitivity, specificity, positive predictive value, and 
   negative predictive value of this finding for the diagnosis of 
   APE were 88%, 99%, 97%, and 95%, respectively. In conclusion, 
   the presence of negative T waves in both leads III and V(1) 
   allows APE to be differentiated simply but accurately from ACS 
   in patients with negative T waves in the precordial leads.

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