Laske A, Jenni R, Maloigne M, Vassalli G, Bertel O, Turina M I
Clinic for Cardiac Surgery, Triemli Hospital Zürich, Switzerland.
Ann Thorac Surg. 1996 Jan;61(1):48-57. doi: 10.1016/0003-4975(95)00922-1.
Pressure gradients calculated from echo-cardiography after aortic valve replacement are commonly much higher than would be expected from in vitro measurements.
The mean, peak-to-peak, and maximal gradients across bileaflet aortic prostheses (St. Jude Medical) were measured invasively in 52 patients at high and low heart rate, cardiac index, and stroke volume. One week after operation the gradients were calculated from a standard transthoracic echocardiogram (delta p = 4v2(2)). In a second study 3 to 12 months later, gradients were calculated using the standard, simplified Bernoulli equation, and with the equation considering subvalvular flow velocities (delta p = 4(v2(2-)v1(2)). Invasive and echocardiographic measurements were matched and compared.
Invasively measured mean gradients for 21 to 29-mm valves ranged from 7.4 +/- 4.9 to 4.3 +/- 1.6 mm Hg at systolic flow rates from 11.3 +/- 0.7 to 16.2 +/- 1.8 L.min-1.m-2. Mean echocardiographic gradients were 15.1 +/- 4.5 to 7.5 +/- 2.2 mm Hg (p < 0.001) with the standard method, and 10.5 +/- 1.9 to 5.6 +/- 1.5 mm Hg when considering the subvalvular flow velocity (p < 0.001).
Mean gradients across bileaflet prostheses are generally low, even in small valves and with high systolic flow. The correlation of the invasive in vivo with in vitro gradients is good. Standard echocardiography overestimates gradients across bileaflet heart valves and high gradients are not due to valve dysfunction. Gradients obtained by echocardiography considering the subvalvular flow velocity correlate better to invasively measured and in vitro gradients.
主动脉瓣置换术后通过超声心动图计算的压力阶差通常比体外测量预期的要高得多。
对52例患者在高、低心率、心脏指数和每搏量情况下，经有创测量双叶主动脉瓣人工瓣膜（圣犹达医疗公司产品）的平均、峰-峰和最大压力阶差。术后1周，通过标准经胸超声心动图计算压力阶差（Δp = 4v2(2)）。在3至12个月后的第二项研究中，使用标准简化伯努利方程以及考虑瓣下流速的方程（Δp = 4(v2(2-)v1(2))）计算压力阶差。将有创测量值与超声心动图测量值进行匹配和比较。
对于21至29毫米的瓣膜，在收缩期流速为11.3±0.7至16.2±1.8升·分钟-1·米-2时，有创测量的平均压力阶差范围为7.4±4.9至4.3±1.6毫米汞柱。采用标准方法时，超声心动图平均压力阶差为15.1±4.5至7.5±2.2毫米汞柱（p<0.001），考虑瓣下流速时为10.5±1.9至5.6±1.5毫米汞柱（p<0.001）。
即使是小瓣膜且收缩期流速高时，双叶人工瓣膜的平均压力阶差通常也较低。体内有创测量值与体外压力阶差的相关性良好。标准超声心动图高估了双叶心脏瓣膜的压力阶差，高压力阶差并非由于瓣膜功能障碍。考虑瓣下流速的超声心动图获得的压力阶差与有创测量值及体外压力阶差的相关性更好。
