REDUCTION OF LEFT-VENTRICULAR PRELOAD BY LOWER-BODY NEGATIVE-PRESSURE ALTERS DOPPLER TRANSMITRAL FILLING PATTERNS

The objective of this study was to evaluate the effect of alterations in preload induced by lower body negative pressure on Doppler transmitral filling patterns. Echocardiograms and Doppler recordings were performed in 18 normal young men (aged 23 to 32 years) during various levels of lower body negative pressure (0, -20 and -50mm Hg). Lower body negative pressure induced a reduction in diastolic velocity integral (from 12.17 ± 0.79 to 8.42 ± 0.71 cm, p = 0.0067) and consequently left ventricular diastolic diameter (from 5.11 ± 0.09 to 4.45 ± 0.1 cm, p < 0.0001). There was a significant reflex increase in heart rate from 59.9 ± 1.9 to 77.1 ± 2.4 beats/min (p < 0.0001), but blood pressure was unchanged. This reduction in preload altered Doppler transmitral filling patterns as follows: 1) peak early velocity (E) decreased from 59.2 ± 3.8 to 39.1 ± 1.7 cm/s (p < 0.0001); 2) atrial filling velocity (A) was unchanged (35.58 ± 1.5 to 33.52 ± 1.4 cm/s, p = 0.517); 3) E A ratio decreased from 1.7 ± 0.13 to 1.19 ± 0.08 (p = 0.0087); 4) mean acceleration (from 482 ± 37 to 390 ± 27 cm/s2, p = 0.03) and mean deceleration (from 327 ± 31 to 169 ± 21 cm/s2, p < 0.001) of the early filling wave were significantly reduced; and 5) peak acceleration (from 907 ± 42 to 829 ± 29 cm/s2) and peak deceleration (from 771 ± 94 to 547 ± 76 cm/s2) also decreased, but not significantly. The reduction in deceleration induced a prolongation of the pressure half-time (from 64.3 ± 3.0 to 86.9 ± 4.9 ms, p = 0.0017). Thus, a decrease in preload, as produced by lower body negative pressure, alters the transmitral Doppler flow pattern to one that has previously been associated with impaired diastolic relaxation. Alterations in preload must be considered when interpreting diastolic transmitral flow profiles obtained by Doppler echocardiography. © 1990.