In acute pulmonary embolism the most frequent ECG finding is

The ECG is often normal but is useful in excluding other impoant differential diagnoses, such as acute myocardial infarction and pericarditis. The most common findings in PE include sinus tachycardia and anterior T-wave inversion but these are non-specific; larger emboli may cause right hea strain revealed by an S1Q3T3 pattern, ST-segment and T-wave changes, or the appearance of right bundle branch block. Aerial blood gases typically show a reduced PaO2 and a normal or low PaCO2, and an increased alveolar-aerial oxygen gradient, but may be normal in a significant minority. A metabolic acidosis may be seen in acute massive PE with cardiovascular collapse. An elevated D-dimer is of limited value, as it may be raised in a variety of other conditions, including myocardial infarction, pneumonia and sepsis. However, low levels, paicularly in the context of a low clinical risk, have a high negative predictive value and fuher investigation is usually unnecessary . The result of the D-dimer assay should be disregarded in high-risk patients, as fuher investigation is mandatory even when normal. The serum troponin I may be elevated, reflecting right hea strain. Ref Davidson edition23rd pg 620