Pulmonary Embolism

Defined

Pulmonary embolism (PE) is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream. Usually this is due to embolism from the deep veins of the legs, a process termed Venous Thromboembolism (VTE).

Signs and Symptoms

Classic presentation: Abrupt onset of pleuritic CP, SOB, dyspnea, tachypnea, tachycardia and hypoxia.

Though, this is rarely the case. Studies of patients who die unexpectedly of a PE reveal that they complained of nagging symptoms often for weeks before death related to a PE.

40% of these patients had been seen by a physician in the weeks prior to their death.

Diagnosis of PE

Diagnosis is based on Clinical Findings, D-Dimer, CT Pulmonary Angiography or V/Q Scan.

CTA vs. V/Q SCAN

The PIOPED I & II studies (2008) were 2 Prospective Investigations of Pulmonary Embolism Diagnoses that tested utility of V/Q scans (I) and CTAs (II).

Among patients with images of adequate quality, CTAs in the pulmonary arteries had a sensitivity of 83% and a specificity of 96%, with NPV of > 90% in 89% of the patients for the diagnosis of acute pulmonary embolism (PE) in patients with correlating Wells Criteria. This was in marked contrast to the results of the PIOPED I, in which the combination of V/Q Scans & Wells Criteria resulted in NPV > 90% in only 22% of patients.

The addition of venous-phase CT venography improved sensitivity to 90%, with a specificity of 95%.

By 2001, CTAs replaced V/Q scanning as the predominant imaging modality for PE diagnosis in the US.

CTA's limitations: High cost, relatively high radiation doses, and contraindications (eg, reduced renal function or iodine allergy).

CTA's advantages: Non-invasive, greater availability to patients, and the possibility of identifying other lung disorders from the differential diagnosis in case there is no PE.

V/Q Scan is used less often with more widespread availability of CTs, however, it may be useful in patients who have an allergy to contrast or in pregnancy due to lower radiation exposure than CT.

In the PIOPED I Study, the V/Q Scan received a Sensitivity of 77% in pts. with high Wells Score and 98% specificity of those with a low Wells Score.

Thus stating that CTA is non-inferior to V/Q scanning, and identifies more emboli (without necessarily improving the outcome) compared to V/Q scanning.

Treatment of PE

Treatment includes Resuscitation, Respiratory Support, IVF (Hemodynamic stability) and Anti-Coagulation with Heparin acutely and long-term Warfarin therapy.

Acute Treatment:
Unfractionated Heparin with Loading dose 80U/kg, followed by maintenance dose of 18U/kg/hr, (monitor with APTT)

Low Molecular Weight Heparin: Lovenox at 1mg/kg q12hrs. or Fragmin 200U/kg daily.

For long term Anticoagulation, pts. should start Warfarin 5mg QHS, generally started within the 1st 24hrs and bridged with UFH or LMWH and warfarin is titrated up until therapeutic (INR 2-3).

Duration of Long-term therapy is controversial, with some studies indicating 12mos, others indicating life-long therapy. Heparin or LMWH is continued for at least five days or until the prothrombin time is in the therapeutic range with INR between 2.0 to 3.0, while simultaneously titrating up Warfarin.

Embolectomy should be considered for patients whose presentation is severe enough to warrant thrombolysis, but in whom thrombolysis is either contraindicated or unsuccessful.

Pts. with contraindications to anticoagulation, fail anticoagulation, or develop complications of anticoagulation (e.g., severe bleeding) should have an inferior vena caval filter placed.

Mortality Rate

The diagnosis of PE is missed in approximately 400,000 patients in the US per year.

Approximately 10% of patients who develop pulmonary embolism die within the first hour.

30% die subsequently from recurrent embolism.

Anticoagulant treatment decreases the mortality rate to less than 5%.

In several studies, the 3-month mortality rate of pulmonary embolism ranged from 10.0-17.5%.

In a study of Medicare recipients with PE, men had a 13.7% mortality rate compared to 12.8% in women; the mortality rate was 16.1% in blacks, compared to 12.9% in whites. Some of the factors were short hospital length of stay and accessibility to medications after D/C.

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