An ECG may show signs of right heart strain or acute cor pulmonale in cases of large PEs – the classic signs are a large S wave in lead I, a large Q wave in lead III, and an inverted T wave in lead III (S1Q3T3), which occurs in 12–50% of people with the diagnosis, yet also occurs in 12% without the diagnosis.This is occasionally present (occurring in up to 20% of people), but may also occur in other acute lung conditions, and, therefore, has limited diagnostic value. The most commonly seen signs in the ECG are sinus tachycardia, right axis deviation, and right bundle branch block. Sinus tachycardia, however, is still only found in 8–69% of people with PE.ECG findings associated with pulmonary emboli may suggest worse prognosis since the six findings identified with RV strain on ECG (heart rate > 100 beats per minute, S1Q3T3, inverted T waves in leads V1-V4, ST elevation in aVR, complete right bundle branch block, and atrial fibrillation) are associated with increased risk of circulatory shock and death.Cases with inverted T in leads V1-3 are suspected with PE or inferior myocardial infarction. PE cases show inverted T waves in leads II and aVF, but inferior myocardial infarction cases do not show inverted T waves in II and aVF. Echocardiography
In massive and submassive PE, dysfunction of the right side of the heart may be seen on echocardiography, an indication that the pulmonary artery is severely obstructed and the right ventricle, a low-pressure pump, is unable to match the pressure.
For many years, vitamin K antagonists (warfarin or less commonly acenocoumarol or phenprocoumon) have been the cornerstone. As vitamin K antagonists do not act immediately, initial treatment is with rapidly acting injectable anticoagulants: unfractionated heparin (UFH), low molecular weight heparin (LMWH), or fondaparinux, while oral vitamin K antagonists are initiated and titrated (usually as part of inpatient hospital care) to the international normalized ratio, a test that determines the dose. In terms of injectable treatments, LMWH may reduce bleeding among people with pulmonary embolism as compared to UFH. According to the same review, LMWH reduced the incidence of recurrent thrombotic complications and reduced thrombus size when compared to heparin. There was no difference in overall mortality between participants treated with LMWH and those treated with unfractionated heparin. Vitamin K antagonists require frequent dose adjustment and monitoring of the international normalized ratio (INR). In PE, INRs between 2.0 and 3.0 are generally considered ideal. If another episode of PE occurs under warfarin treatment, the INR window may be increased to e.g. 2.5–3.5 (unless there are contraindications) or anticoagulation may be changed to a different anticoagulant e.g. LMWH.In recent years, many anticoagulants have been introduced that offer similar to warfarin but without a need for titration to the INR. Known as the directly acting oral anticoagulants, these treatments are now preferred over vitamin K antagonists by American professional guidelines. Two of these (rivaroxaban and apixaban) do not require initial heparin or fondaparinux treatment, whereas dabigatran and edoxaban do.