Assessing left ventricular filling pressure with flow-directed (Swan-Ganz) catheters. Detection of sudden changes in patients with left ventricular dysfunction.

The accuracy with which pulmonary pressures reflect sudden changes in left ventricular (LV) pressures was studied in 15 patients without mitral disease. Mean pulmonary artery (PA), pulmonary artery end-diastolic (PAd), mean pulmonary capillary (PC), and pulmonary capillary "a" wave (PCa) pressures were compared with simultaneous LV diastolic pressures measured before (LV pre "a") and after atrial systole (LVEDP). Recordings were made at rest and after angiography. There were significant correlations (r greater than 0.75, P less than 0.01) between LV diastolic pressures and each of the pulmonary pressures. The LVEDP and PCa related most closely (r = 0.98). Differences of 5 mm Hg or more between LVEDP and either PAd or PC occurred in more than 50 percent of the observations and were due to large LV "a" waves. The PC, and to a lesser degree the PAd, were more closely related to LV pre "a" than to LVEDP. Changes (delta) in PCa after LV angiography approximated deltaLVEDP, whild deltaPAD and deltaPC reflected deltaLV pre "a" more closely than deltaLVEDP. In conclusion, PCa reflects the LV "a" wave and, thus, is the most accurate index for LVEDP and deltaLVEDP in patients with LV dysfunction. The PC reflects LV pre "a" (mean LV filling pressure) but is an unreliable index of LVEDP. The PC is more easily measured than PCa and, with proper interpretation, should remain the most useful measurement for patient monitoring.