QJM vol. 97 no. 10 © Association of Physicians 2004; all rights reserved.
Correspondence |
Pulmonary embolism and thrombolysis
Sir,Loebinger and Bradley1 argue for the use of thrombolysis in the treatment of pulmonary embolism in the presence of respiratory failure without circulatory compromise. The authors advocate the use of thrombolysis in patients with severe hypoxia in the context of recent pulmonary embolism, without relying on investigations such as echocardiography to ascertain right ventricular impairment. Loebinger and Bradley also draw parallel comparisons to thrombolysis in myocardial infarction.
Tempting as it may be, the use of thrombolysis in treating pulmonary embolism is far from established. The authors fail to address ongoing operational problems inherent to the UK National Health Service in terms of human and financial resources, and the deficiency in emergency radiology service provision for the diagnosis of acute pulmonary embolism through means of thoracic computed tomography pulmonary angiography. These factors may explain why the mean time for thrombolysis in pulmonary embolism is of the order of days rather than hours, compared to that in myocardial infarction, as highlighted by the authors.
It is also difficult to gauge the exact reason for the patients developing respiratory failure without circulatory compromise, as the primary insult of pulmonary embolism is in the circulatory compartment. One would have intuitively deduced that in order for respiratory failure to occur, vascular compromise would have had to have been at such a significant degree at a proximal level as to affect gas exchange, given the number of alveoli and the collateral circulation present in the lungs. Respiratory failure without circulatory compromise in the context of pulmonary embolism is therefore a complex phenomenon, reflected by its rarity, with only four such cases observed in the authors’ institution over a one-year period. Finally, thrombolysis has been shown to be non-superior to placebo as co-therapy to intravenous heparin in terms of in-hospital mortality rates in acute sub-massive pulmonary embolism without haemodynamic instability,2 thus calling into question its therapeutic role in such patients.
Department of Respiratory Medicine Ipswich Hospital Ipswich
Department of Respiratory Medicine Aberdeen Royal Infirmary Aberdeen
Department of Respiratory Medicine Llandough Hospital Penarth
References
1. Loebinger MR, Bradley JC. Thrombolysis in pulmonary embolism: are we under-using it? Q J Med 2004; 97:361–4.
2. Konstantinides S, Geibel A, Heusel G, Heinrich F, Kasper W. Heparin plus alteplase compared with heparin alone in patients with submassive pulmonary embolism. N Engl J Med 2002; 347:1143–50.
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