Pulmonary embolism

Today we discussed PE in the setting of malignancy. Some points about this common and serious disease:

Clinical presentation:
Notoriously unreliable. May see any or none of

SOB, pleuritic C/P, hemoptysis, palpitations
Tachypnea, tachycardia, desaturation, hypotension

Other possible findings:
ABG- hypoxia, resp alkalosis
CXR- atelectasis, effusion, Westermarks's (proximal pulm art dist with distal oligemia), Hampton's hump (peripheral density from infarct). This CXR signs are rare; most commonly normal CXR
ECG- RV strain (STD V1-V2, RBBB, RAE, RVH, R axis dev), S1Q3T3- massive. Usually just sinus tach
Echo- RV stress (hypokinesis, TR, dilation)

Clinical exam is of insufficient Sn/Sp to make diagnosis; it gives a pretest probability.
Non-invasive investigations are also not Sn or Sp alone, although a -ve CTA may be sufficient to withhold anticoagulation

Approach is to
1) Determine pretest probability
2) Determine whether pt has adequate cardiopulmonary reserve (i.e. will another PE kill this pt?)
3) Perform noninvasive or invasive investigations.

Risk stratification:
Clinical findings of DVT- 3
No other more likely dx- 3
Immobilized over 3d or major surgery within 1 mo- 1.5
HR over 100- 1.5
Previous DVT/PE- 1.5
Active Ca- 1
Hemoptysis- 1

Greater than 6: High PTP (78% have PE)
2-6: Int (28% have PE)
Lower than 2: Low (3% have PE)

Management:

DVT and PE are treated the same way:
Initially: LMWH (unless renal impairment or need ability to reverse, in which case UFH infusion. Start warfarin; adjust to INR 2-3, then d/c warfarin

Long term:
With reversible/treatable cause for DVT/PE:
Treat underlying, anticoag for 3-6 mo then stop.

Idiopathic:
Anticoag for 6/12, then decide whether to continue based on:
bleeding risk, pregnancy plans, pt's preference.

Underlying unmodifiable reason:
Lifelong anticoag recommended

EBM points:

VTE in cancer

CLOT trial compared the efficacy and complications of the use of LMWH vs. warfarin in treatment of DVT/PE in cancer pts.
Intervention: Dalteparin 200u/kg SC OD x 5d, followed by coumadin for INR 2.5 or dalteparin alone, 200u/kg for 1 month and 150u/kg for 5 months.
Outcomes: recurrent DVT in 6 months, mortality, bleeding
Results: Recurrent DVT: 17% vs. 9% on LMWH (ARR 8%, NNT 13). Significant bleeding: 4% warf, 6% LMWH. Mortality in 6/12: 39% LMWH, 41% warfarin. Subgroup analysis showed decreased mortality on LMWH in pts presenting with VTE and metastatic ca.

Thrombolysis in PE

Only RCT evidence comes from 2002 NEJM paper comparing alteplase vs. placebo in patients with acute PE and RV dysfunction or pulmonary hypertension. Endpoint was mortality or "clinical deterioration requiring escalation of treatment"; this might include pressors/inotropes, CPR, surgery, intubation, or thrombolysis. There was no mortality difference, but the alteplase group had significantly lower "escalation of care". This is a criticized paper because some argue that it essentially gives the "escalation of care" outcome to 1 group to begin with (i.e. thrombolysis as both an intervention and an outcome is a bit strange).