Weiss P, Hoffmann A, Burckhardt D
Department of Internal Medicine, University Hospital, Basel, Switzerland.
Br Heart J. 1992 Jun;67(6):466-9. doi: 10.1136/hrt.67.6.466.
To compare the effect of exercise on pressure half time in patients with mechanical or bioprosthetic mitral valves. A relative pressure half time (pressure half time as a percentage of RR interval) was used in an attempt to correct for the shortening of the diastolic time interval caused by the increase in heart rate during exercise and thus to uncover the effects of valve design on pressure half time during exercise.
Twenty clinically stable (New York Heart Association grade I-II) patients with mechanical (n = 12) or bioprosthetic (n = 8) mitral valves (median age 51) years. The median time since valve replacement was 42 months.
Continuous wave Doppler echocardiography from the apical view at rest and during moderate supine bicycle exercise (50 W).
During exercise the mean (SD) heart rate increased from 79 (12) to 101 (12) beats per minute (95% confidence interval (95% CI) of difference, 15 to 29/min) and the peak pressure gradient from 11 (5) to 18 (6) mm Hg (95% CI of difference 5 to 9 mm Hg). The pressure half time decreased from 114 (30) to 78 (26) ms (95% CI of difference (30-42 ms). There was no difference between the valve types. The relative pressure half time remained unchanged in patients with mechanical valves during exercise (13 (4) rest and 13 (5)% exercise, respectively) and decreased in patients with bioprostheses (17 (3) and 12 (3)%, respectively (95% CI of difference 2 to 8%, p = 0.025).
In patients with mechanical mitral valves the decrease in the pressure half time during exercise is probably mostly the result of the shortening of the diastolic time interval with increasing heart rate whereas in patients with bioprosthetic valves an increase in functional valve area may contribute to the shortening of pressure half time during exercise.
比较运动对机械瓣或生物瓣二尖瓣置换患者压力减半时间的影响。采用相对压力减半时间（压力减半时间占RR间期的百分比），试图校正运动时心率增加导致的舒张期时间间隔缩短，从而揭示瓣膜设计对运动时压力减半时间的影响。
20例临床稳定（纽约心脏病协会心功能I-II级）的机械瓣（n = 12）或生物瓣（n = 8）二尖瓣置换患者（中位年龄51岁）。瓣膜置换后的中位时间为42个月。
在静息和中度仰卧位自行车运动（50 W）时，从心尖视图进行连续波多普勒超声心动图检查。
运动期间，平均（标准差）心率从每分钟79（12）次增加到101（12）次（差异的95%置信区间（95%CI）为15至29次/分钟），峰值压力梯度从11（5）mmHg增加到18（6）mmHg（差异的95%CI为5至9 mmHg）。压力减半时间从114（30）ms降至78（26）ms（差异的95%CI为30 - 42 ms）。瓣膜类型之间无差异。机械瓣患者运动期间相对压力减半时间保持不变（静息时分别为13（4）%，运动时为13（5）%），生物瓣患者相对压力减半时间降低（分别为17（3）%和12（3）%，差异的95%CI为2至8%，p = 0.025）。
在机械瓣二尖瓣置换患者中，运动时压力减半时间的缩短可能主要是由于心率增加导致舒张期时间间隔缩短，而在生物瓣二尖瓣置换患者中，功能性瓣膜面积的增加可能有助于运动时压力减半时间的缩短。
