Non-invasive estimation of pulmonary capillary wedge pressure at rest and during exercise by electrocardiography, phonocardiography and Doppler echocardiography.

Non-invasive estimation of the mean pulmonary capillary wedge pressure was accomplished by simultaneous electrocardiographic, phonocardiographic and continuous wave Doppler echocardiographic recordings. The interval from the onset of the QRS complex to the Doppler determined mitral valve closure (Q-MC) and the interval from the phonocardiographic aortic component of the second heart sound to the Doppler determined mitral valve opening (A2-MO) were measured. The non-invasive registrations were carried out simultaneously with direct measurements of the wedge pressure. In an initial group of 22 patients, a significant correlation was observed between the intervals alone and the wedge pressure, r = 0.60, SEE = +/- 6.9 mmHg, p less than 0.01, for the Q-MC interval and r = -0.70, SEE = 6.2 mmHg, p less than 0.001 for the A2-MO interval. A closer correlation was observed between the ratio Q-MC/A2-MO and the measured wedge pressure, r = 0.93, SEE = +/- 3.1 mmHg, p less than 0.001. The linear regression equation, PCW = 19.5 (Q-MC/A2-MO) + 3.0 (mmHg), was applied prospectively to a second group of 23 patients. Again the relationship between estimated and measured wedge pressure was highly significant, r = 0.90, SEE = +/- 3.1 mmHg, p less than 0.001. Twenty-two patients were also studied during an exercise test, and acceptable non-invasive recordings were obtained in 19 of them. The change in estimated wedge pressure during activity related closely to the change in actual wedge pressure, r = 0.80, SEE = +/- 5.7 mmHg, p less than 0.001. A simplified equation suitable for routine clinical practice, PCW = 24 (Q-MC/A2-MO) (mmHg), yielded almost equally accurate estimates of the wedge pressure over a wide range of pressures. The simplicity and reasonable accuracy of Doppler-assisted estimation of the wedge pressure makes it useful in the evaluation and follow-up of patients with suspected cardiac disorders. The method may assist in evaluating the effects of diagnostic or therapeutic procedures, since it is sufficiently sensitive to detect acute directional changes in wedge pressure.