Roentgen Evaluation of Pulmonary Arterial Pressure in Mitral Stenosis

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Abstract
Quantitation of pulmonary hypertension in mitral stenosis is of clinical importance not only for determination of the severity of the mitral block but also for prediction of the reduction in pressure to be expected after valvulotomy. The demonstration of resting obstructive pulmonary hypertension, therefore, has become established as a major indication for surgical treatment in this form of rheumatic heart disease. If a main purpose of cardiac catheterization in mitral stenosis is the mensuration of pulmonary arterial pressure, then an accurate roentgenologic method for prediction of that pressure would be of significant clinical value. It is the purpose of this paper to review attempts made in the past to relate roentgen findings to pulmonary arterial pressure and to report the value of newly devised multi-parameter formulas for that purpose. Prior Investigation Presence of Kerley's B-Lines: Twenty-seven years ago Kerley (11) stated, with respect to the chest roentgenogram in mitral stenosis, that after “a severe attack of passive hyperaemia … the shadows of the perivascular lymphatics persist as fine sharp lines, most marked at the bases and near the hila.” “Kerley's lines” consist of A-lines, or radiating perihilar lines, and B-lines, or peripheral basal lines. This observation remained relatively unnoticed for many years. Conditions which result in thickening of the subpleural intralobular septa or dilatation of their lymphatic vessels may produce B-lines. Septal thickening may occur in pneumoconiosis, lymphangitic carcinomatosis, hemosiderosis, sarcoidosis, reticulosis, and hilar lymphatic block (Grainger, 9). Pulmonary venous hypertension of any etiology may produce B-lines. Their occasional presence during left ventricular failure (Short, 18) and chronic passive congestion (Fleischner and Reiner, 7) has been noted. B-lines are rarely if ever seen in uncomplicated pulmonary arterial hypertension (Bruwer et al., 4; Levin, 12). The development of B-lines in mitral stenosis is presumptive evidence of pulmonary venous hypertension. Attempts to “calibrate” B-lines in terms of coexistent pressures within the pulmonary circulation have shown that the presence or absence of these lines correlates somewhat more closely with the level of pulmonary “capillary” pressure than with mean or diastolic pulmonary arterial pressures (Grainger, 9). There is a range of pulmonary “capillary” pressures above which B-lines are usually seen and below which they rarely appear; this is approximately 20 to 30 mm. Hg (Bruwer et al., 4; Carmichael et al., 5; Fleming and Simon, 8; Grishman et al., 10; Whitaker and Lodge, 19). Rossall and Gunning (14), who measured mean left atrial and pulmonary arterial pressures by transbronchial puncture in 100 patients with mitral stenosis, found that B-lines were never present when the mean left atrial pressure was below 10 mm. Hg. If the mean left atrial pressure was in excess of 24 mm. Hg, B-lines were invariably present.

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