Cause:Embolic clots to pulmonary arteries via systemic venous return
Pathophys:Thrombophlebitis causes thrombus, which breaks free and migrates to the lungs; many pts have many small emboli chronically rather than one big one. Rarely are calves the source; most from thigh and pelvic veins; no si or sx of DVT in 50%
Very common; probably incidence correlates best with thoroughness of postmortem exam
Associated with: estrogen-containing birth control pills, esp 2nd-generation types (<50 µgm estrogen + norgestrel, levonorgestrel, or norgestrienone), or worse 3rd-generation types (desogestrel, gestodene, or norgestionate); pregnancy (Nejm 1996;335:108); and postmenopausal replacement rx; occult cancers, 15% of cancer patients will have within 2 yr (Ann IM 1982;96:556); DVT and its genetic precipitants (Deep Venous Thrombophlebitis); surgery, esp of legs; cramped air travel (Nejm 2001;345:779), end of trip incid = 1.5/million for trips >3100 mi, 4.8/million if >6200 mi
Rare upper extremity DVT, esp after central iv line and in athletes w repetitive arm abduction, “Paget-Schroetter syndrome” (Nejm 2002;347:1876); can even lead to fatal PE
Sx:Sudden or chronic dyspnea; pleuritic chest pain w infarct; hemoptysis; fever; syncope with large emboli
Si:All uncommon; elevated JVP; high diaphragm on one side by percussion; basilar atelectasis; pleural effusion; wheezing (Nejm 1968;278:999); P2 > A2; cyanosis
Table 16.5a Revised Geneva Score for Suspected Pulmonary Embolism (Ann IM 2006;144:165)
| Variable | Points |
|---|
| Heart rate 95 beats/min or more | 5 |
| Pain on lower-limb deep venous palpation and unilateral edema | 4 |
| Heart rate of 75 to 94 beats/min | 3 |
| Previous deep venous thrombosis or pulmonary embolism | 3 |
| Unilateral lower limb pain | 3 |
| Surgery or fracture within 1 month | 2 |
| Active malignant condition | 2 |
| Hemoptysis | 2 |
| Age older than 65 years | 1 |
Table 16.5b Probability of PE Based on Revised Geneva Score (Ann IM 2006;144:165)
| Low | Intermediate | High |
|---|
| Score | 0-3 | 4-10 | >10 |
| Prevalence of PE | 8% | 28% | 74% |
(Nejm 1992;326:1240)
Resolves over 10-30 d (Nejm 1969;280:1194); 80% overall survival; 60% without rx, 90% with rx; 75% of deaths occur in 1st 2 h; DVT clinically resolves in 1/3 after 3 d of heparin rx
Fatalities <2% in yr following dx if rx’d × 3-6 mo (Jama 1998;279:458)
Chronic pulmonary hypertension in 4% (Nejm 2004;350:2257)
r/o air embolism (Nejm 2000;342:476)
Lab: (McMaster’s Univ rv-Ann IM 1991;114:300)
ABGs:if pO2 over 80 mm Hg no PE, but 10% false negative; if over 90 mm Hg exclude PE, 0% false negative
Hem:Fibrin split products/D-dimer over 500 ngm/cc by ELISA methods, 96% sens, 68% specif (Jama 2006;295:172, 199, 213; Ann IM 2006;144:812; 2004;140:589); combined w ABG criteria above, if D-dimer negative and pO2>80 on RA, no false negs for PE (Thorax 1998;53:830)
Noninv:EKG may show S1Q3T3, very specific but only w massive emboli (Am J Emerg Med 1997;15:310); anterior T-wave inversions (68% sens) (Chest 1998;113:850); or 
3 of the following (70% sens) (Am J Cardiol 1994;73:298): RBBB or pRBBB, S in I and aVL 15 mm, poor R progression, Q in III and F not II, RAD >90°, voltage <5 mm in limb leads, T inversions in II + F or V1-V4
Xray:
All doable even in pregnancy (Nejm 1996;335:108)
Chest shows infiltrates, effusions, high diaphragm, lucency from segmental hypoperfusion
V/Q scan to look for multiple mismatched defects (87% sens, 97% specif), but even if all defects are matched, odds of pulmonary embolus still are substantial (case—Nejm 1995;332:321; Ann IM 1983;98:891), ie, 40% (PIOPED—Jama 1990;263:2753)
Spiral (helical) multislice CT alone (Nejm 2006;354:2317; 2005;352:1760; Jama 2005;293:2012) 83% sens, 95% specif (Nejm 2006;354:2317, 2383), or w neg w leg ultrasounds enough to r/o w <2% false neg rate. But 30% higher CT result compared to V/Q without any better prediction of subsequent PEs makes false positives more likely w CT (Jama 2007;298:2743, 2788)
To find DVT, B-mode duplex ultrasound (Ann IM 1989;111:297); ultrasound positive in only 1/3 of documented pulmonary emboli cases (Ann IM 1997;126:775)
Rx:
Prevent w warfarin or sc unfractionated q 12 h or qd low-molec wgt heparin (Anticoagulants)
Screen for reversible causes w factor V (Leiden), homocysteine, and lupus anticoagulant (which requires more intense anticoagulation)
Heparin (Anticoagulants), low-molecular weight rather than unfractionated (ACP J Club 2005;142:71) for at least 5 d if start warfarin on day 1 (Nejm 1990;322:1260). Used long term in pregnancy keeping PTT 1.5 × control at 6 h
Warfarin to an INR of 2-3 (Anticoagulants) × 6 (Nejm 1995;332:166) to 12 mos; 12% will recur whenever anticoag stopped (Ann IM 2003;139:1)
Thrombolysis rarely if severe, w thrombolytics if refractory hypotension
Surgical IVC plication, or Greenfield filter rarely; embolectomy (50% survival) rarely needed