Update on echocardiography in pulmonary embolism

Diagnosis

Several 2-D echocardiographic criteria have been published in pulmonary embolism. In significant pulmonary embolism (angiographic Miller index > 30%), echocardiography is able to detect a right ventricular dilatation, a right ventricular hypokinesia/dysfunction or a pulmonary hypertension (1,2). In a recent study, we have demonstrated that the right to left ventricular end-diastolic area ratio, measured in apical 4-chamber view is the best echocardiographic reflect of right ventricular obstruction (Figure 1) (3). An acute cor pulmonale is defined as a ratio higher than 0.6, associated with a paradoxic septal wall motion. Echocardiography may also detect free-floating right-heart thrombus in less than 10% of patients.
In spite of its limitations (especially visualisation of left pulmonary artery), transoesophageal echocardiography may be routinely used in the diagnosis of proximal pulmonary embolism (4) and is a powerful diagnostic tool which should be mostly recommended in a population of resting intensive care unit patients.

Echocardiography alone?

The usefulness of 2-D echocardiography for the management of critically ill patients has been clearly demonstrated. However, the main limitation of 2-D echo is its poor effectiveness in distal pulmonary embolism. The venous ultrasonography of the lower limbs allows for the exploration of the venous system to a great extent and for the detection of indirect signs of pulmonary embolism. The diagnostic value of an ultrasonographical combined strategy (echocardiography associated with venous ultrasonography) is high and this strategy seems to be reliable in pulmonary embolism (Table 1).

Help for treatment ?

The echocardiographic detection of free-floating right-heart thrombus may guide the treatment and this situation requires urgent treatment, such as thrombolysis or surgical embolectomy.
Recently, some authors have suggested that echocardiography may help in the choice of treatment. In fact, in hemodynamically stable patients, thrombolysis could be indicated when pulmonary embolism is associated with echocardiographic disturbances (5). However, the rate of mortality in this population of pulmonary embolism (echocardiographic disorders but stable hemodynamic setting) is low (2-5%). No difference in terms of mortality was observed in patients treated with heparin or with thrombolysis. The only difference is the necessity of treatment escalation in the group without thrombolysis.
It could be of interest to associate echocardiographic findings with biological parameters such as metabolic acidosis or troponin, for the best characterisation of patients necessitating thrombolysis (6,7). These data urge for large-scale trials to best-determine which patients really require thrombolysis, with a reduction of mortality.

Table 1. Usefulness of the combination of echo with venous ultrasonography in pulmonary embolism (PE)
Incidence of acute cor pulmonale (ACP) alone or with deep venous thrombosis (DVT)

Modified from Mansencal N. et al. Int J Cardiol in press

Figure 1: ROC curve analysis, allowing to compare several echocardiographic parameters in pulmonary embolism (RVEDA/LVEDA = right to left end-diastolic area ratio; RVEDD/LVEDD = right to left end-diastolic diameter ratio; SPAP = systolic pulmonary arterial pressure; RVEDD = right ventricular end-diastolic diameter). The best index of right ventricular obstruction was observed with the right to left end-diastolic area ratio. We also determined the best cut-off values of these different echocardiographic parameters (modified from Mansencal N et al. Am J Cardiol 2003 ; 92 : 116-9).

The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.