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I read with great interest the case report by Langlebenet al 1 of a woman with coexisting mitral stenosis and primary pulmonary hypertension (PPH) or plexogenic pulmonary arteriopathy who succumbed to operation for relief of her mitral stenosis. The failure of the patient's pulmonary hypertension to decrease postoperatively led to her fatal outcome because the coexisting primary pulmonary hypertension was not recognised preoperatively.
I would like to call attention to the fact that the diagnosis should have been suspected preoperatively because her pulmonary artery wedge pressure was only modestly raised (16 mm Hg; normal = 12) and her pulmonary vascular resistance was extremely high (1823 dynes s cm–5; normal = 67 (30)). In the presence of severe mitral stenosis the pulmonary artery wedge pressure, which reflects the left atria1 pressure, is usually substantially increased whereas the pulmonary vascular resistance is usually normal or mildly raised in the presence of “reactive” as well as “passive” pulmonary hypertension. On the other hand, in primary pulmonary hypertension the pulmonary artery wedge pressure is usually normal and the calculated pulmonary vascular resistance is extremely high.
Case reports like that of Langleben et al 1 illustrate the importance of careful analysis of the haemodynamic data obtained at cardiac catheterisation “in order to identify plexogenic pulmonary arteriopathy (or primary pulmonary hypertension) obscured by or masquerading as other disorders” such as mitral stenosis.
authors' reply Dr Cheng's analysis of the patient we presented is somewhat superficial from several aspects. Firstly, by current convention and by definition, a mean pulmonary capillary wedge pressure of more than 15 mm Hg is not consistent with the diagnosis of primary pulmonary hypertension. With that finding one must begin to suspect other diagnoses. The detection of severe mitral valvular disease on an echocardiogram also precludes a diagnosis of primary pulmonary hypertension. Secondly, we agree that most patients with mitral stenosis have greatly increased wedge pressures making the diagnosis obvious and easy. However, there is a subset of patients with severe mitral stenosis who present with a “markedly reduced cardiac output and a low transvalvular pressure gradient”1-1—that is, a relatively low wedge pressure. Thus, the absence of a very high wedge pressure does not preclude the diagnosis of mitral stenosis, particularly when the cardiac output is low. Casual dismissal of a relatively low wedge pressure could lead to a failure to detect mitral stenosis. Thirdly, Dr Cheng's statement that the pulmonary vascular resistance is “usually normal or mildly raised” may refer to mild mitral stenosis, but it has been recognised for 50 years that pulmonary vascular resistance can rise disproportionately to the left atrial pressure in humans.1-2 Moreover, it has been recognised that extreme elevations in pulmonary vascular resistance can occur in mitral stenosis in at least 10% of patients in many series.1-3 1-4This probably reflects a genetic variation within the population as we discuss in our case report. In addition, the literature describes cases of extreme elevation of pulmonary vascular resistance in mitral stenosis, even in the presence of a “low” wedge pressure.1-5 Our patient fits this profile.
Thus, this case was much more complex than Dr Cheng implies. Had we ignored the echocardiographic data and initially assumed, as he does, that she obviously had primary pulmonary hypertension, then administration of currently accepted therapy for that disease—that is, vasodilators—would probably have killed her by producing pulmonary oedema from an inability of the lung to drain through a stenosed mitral valve. That potential outcome suggests that, while careful analysis of haemodynamic data obtained at cardiac catheterisation is, of course, essential, a superficial perusal of the subtleties of pulmonary vascular disease is equally dangerous.
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