**8. Computed tomography pulmonary angiography (CTPA)**

Over the last several decades, CTPA has become the first-line imaging modality for the assessment of PE. When compared with V/Q scanning in a randomized, single-blinded noninferiority clinical trial involving 1417 patients, CTPA was found to be non-inferior to V/Q scanning (Anderson 2007). CTPA is readily available and offers a high level of sensitivity and specificity for acute PE (Huisman 2013). PIOPED II found CTPA to be 83% sensitive and 96% specific for PE (Stein 2006). The newer generation multi-detector CTPA sensitivity is over 95% for segmental, lobar and centrally located PE (Huisman 2013) and is an extremely useful test to exclude PE (van Beek 2001). As with all other imaging modalities for pulmonary thromboembolism, CTPA should be used as part of an integrated approach in the evaluation of PE (Rathbun 2000, Van Strijen 2005) utilizing risk assessment tools to determine the appropriateness of proceeding to CTPA as this test does expose patients to radiation (Remy-Jardin 2007) and IV contrast.

**10. Pulmonary angiography**

invasive attempts at diagnosis are inconclusive.

**11. Cardiac magnetic resonance imaging**

this imaging strategy prior to its routine use.

reported, 12% (Stein 1975) to 28% (Cutforth 1958).

**12.1. Electrocardiography**

Pulmonary angiography is an invasive test that requires catheter placement in the pulmonary artery and directed IV contrast infusion to detect intraluminal vascular filling defects that might be caused by PE. This test requires performance and interpretation expertise and carries a risk of intracardiac catheter placement, radiation, and contrast exposure. In 1992, Stein et al (Stein 1992) reported 0.5% mortality, 1% nonfatal complications and 5% minor complications associated with this test in the 1,111 patients who underwent angiography in PIOPED. In most centers, pulmonary angiography has been replaced by CTPA as the standard for the diagnosis of PE (Hogg 2006). Currently, pulmonary angiography is only employed when other less

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Cardiac magnetic resonant imaging (MRI) is not a widely utilized tool in the evaluation of patients with PE. Magnetic resonance angiography (MRA) is often limited by motion artifact with resultant suboptimal resolution (Tapson 1997). When MRA was evaluated prospectively in 118 patients with dyspnea, MRA was positive in only 77% of patients with confirmed pulmonary embolism by conventional pulmonary angiography. Furthermore, in that study, MRA was positive in 100% of lobar PE, 84% of segmental PE and 40% of subsegmental PE (Oudkerk 2002). MRA may have promise in the future but requires further optimization of

**12. Assessment of right ventricle and pulmonary vasculature derangements**

Electrocardiography (ECG) is an easily obtainable initial study in the evaluation of dyspnea and chest pain. It is often helpful in evaluating for acute coronary syndrome. Unfortunately, ECG has limited diagnostic value for acute PE (Rodger 2000). However, in the setting of known pulmonary thromboembolism, ECG is oftentimes abnormal and may be of some benefit in risk stratification. In 1997, Ferrari et al (Ferrari 1997) reported the results of 80 consecutive ECGs in hospitalized patients with documented pulmonary embolism. T-wave inversion in the precordial leads was shown to be the most common abnormality (68%) and correlated with PE severity. Anterior T wave inversions had a sensitivity of 90% and specificity of 81% for massive PE. The classic finding of acute RV failure with S1Q3 T3 was seen in 50% of ECGs in the setting of confirmed acute PE (Ferrari 1997) which is more frequent than previously
