Guazzi M, Maltagliati A, Tamborini G, Celeste F, Pepi M, Muratori M, Berti M, Guazzi M D
Istituto di Cardiologia dell'Università degli Studi, Centro Cardiologico, IRCCS, Centro di Studio Ricerche Cardiovascolari del Consiglio Nazionale delle Ricerche, Milano, Italy.
J Am Coll Cardiol. 2000 Jul;36(1):185-93. doi: 10.1016/s0735-1097(00)00698-7.
We aimed to assess the differences in the adaptive response of patients with hypertrophic cardiomyopathy (HCM) compared with normal subjects, as well as any association with increased susceptibility to the test.
Diastolic function contributes importantly in the adaptation of the normal heart to head-up tilting. This mechanism may be disturbed by an impaired relaxation in HCM.
Twenty-one male patients with HCM (46 +/- 6 years old) and 22 healthy men (44 +/- 8 years) were studied using Doppler echocardiography after 1 and 10 min of head-up tilting at 20 degrees, 40 degrees and 60 degrees.
In control subjects, tilting was associated with 1) a predominance of diastolic pulmonary venous flow and early left ventricular (LV) filling (atrium functioning as an open conduit); 2) right ventricular (RV) shrinkage; and 3) no LV dimensional variations. In patients with HCM, tilting was associated with 1) a prevalence of systolic pulmonary venous flow (atrium functioning as a reservoir in which filling depends on atrial relaxation and compliance) and late diastolic transmitral flow (atrium working as a booster pump); 2) LV shrinkage; and 3) no RV dimension variations. These mechanisms did not prevent stroke volume (SV) from decreasing at 40 degrees and 60 degrees in both groups. Because of a lower increase in heart rate (HR), a reduction in cardiac output (CO) was greater in patients with HCM. The responses were similar after 1 and 10 min of tilting in control subjects, whereas in patients, blood pressure (BP), SV and LV dimension fell more after 10 min.
Adaptation of the normal heart to tilting is based on a ventricular interaction and LV diastolic properties; HCM relies on left atrial diastolic and systolic functions. An inadequate HR reaction to a fall in BP and SV in HCM (depressed reflexogenic activity) contributes to making CO more vulnerable by greater and more prolonged displacements.
我们旨在评估肥厚型心肌病（HCM）患者与正常受试者适应性反应的差异，以及与试验易感性增加的任何关联。
舒张功能在正常心脏适应头高位倾斜中起重要作用。肥厚型心肌病中舒张功能受损可能会干扰这一机制。
对21名男性肥厚型心肌病患者（46±6岁）和22名健康男性（44±8岁）在20度、40度和60度头高位倾斜1分钟和10分钟后使用多普勒超声心动图进行研究。
在对照组中，倾斜与以下情况相关：1）舒张期肺静脉血流和左心室（LV）早期充盈占优势（心房起开放管道作用）；2）右心室（RV）缩小；3）左心室尺寸无变化。在肥厚型心肌病患者中，倾斜与以下情况相关：1）收缩期肺静脉血流占优势（心房起储存库作用，其充盈取决于心房舒张和顺应性）和舒张晚期二尖瓣血流（心房起增压泵作用）；2）左心室缩小；3）右心室尺寸无变化。这些机制并未阻止两组在40度和60度时每搏输出量（SV）下降。由于心率（HR）升高幅度较小，肥厚型心肌病患者的心输出量（CO）下降幅度更大。对照组在倾斜1分钟和10分钟后的反应相似，而在患者中，10分钟后血压（BP）、每搏输出量和左心室尺寸下降更多。
正常心脏对倾斜的适应基于心室相互作用和左心室舒张特性；肥厚型心肌病依赖于左心房的舒张和收缩功能。肥厚型心肌病患者对血压和每搏输出量下降时心率反应不足（反射性活动降低），导致心输出量因更大、更持久的变化而更易受损。
