Discussion: Although not diagnostic of pulmonary embolism, initial TTE can help in identifying when pulmonary embolism may be the cause by detecting RV dilation (RVIDD/LVIDD ratio > 0.9) and assist with ruling out other causes, such as pericardial effusion or myocardial infarction. Once the diagnosis of pulmonary embolus is established, these patients can be risk-stratified according to the effects of elevated RV afterload: hypotensive patients and those with elevated cardiac biomarkers or echocardiographic indices of RV strain are at an increased risk, and thrombolysis is considered a class II indication. Patients with massive pulmonary embolism can have serial assessments of RV size. Typically, only patients in whom the diagnosis of acute PE has been confirmed should be considered for thrombolytic therapy because the adverse effects can be devastating. For each patient, the indications and potential benefits must be carefully weighed against the risk of adverse events, taking into consideration the patient's values and preferences.
The most important Echocardiographic findings in favor of pulmonary embolism are as follows:
· RV overload criteria: the presence of ≥1 of four signs: (i) right-sided cardiac thrombus; (ii) RV diastolic dimension (parasternal view) >30 mm or a RV/LV ratio >1; (iii) systolic flattening of the interventricular septum; and (iv) acceleration time <90 ms or tricuspid insufficiency pressure gradient >30 mmHg in absence of RV hypertrophy.
· The 60/60 sign is acceleration time of RV ejection <60 ms in the presence of tricuspid insufficiency pressure gradient ≤ 60 mmHg.
· The McConnell sign is normokinesia and/or hyperkinesia of the apical segment of the RV free wall despite hypokinesia and/or akinesia of the remaining parts of the RV free wall. Concomitant echocardiographic signs of pressure overload are required to prevent false diagnosis of acute PE in patients with RV free wall hypo/akinesis due to RV infarction.
Persistent hypotension or shock (i.e. a systolic blood pressure <90 mmHg or a decrease in the systolic blood pressure by ≥40 mmHg from baseline) due to acute PE is the only widely accepted indication for systemic thrombolysis. In most cases, systemic thrombolytic therapy should be considered only after acute PE has been confirmed because the adverse effects of this therapy can be severe.
Most clinicians and society guidelines accept that thrombolysis in acute PE with hypotension is likely beneficial and therefore is an accepted indication. Most societal guidelines also suggest catheter-directed thrombolysis as rescue therapy following failed systemic thrombolysis in centers with appropriate expertise.
American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest 2012; 141:e419S
Guidelines on the diagnosis and management of acute pulmonary embolism:
European Heart Journal (2008) 29, 2276–2315