Kozakova Michaela, Fraser Alan G, Buralli Simona, Magagna Armando, Salvetti Antonio, Ferrannini Ele, Palombo Carlo
Department of Internal Medicine, University of Pisa School of Medicine, Italy.
Hypertension. 2005 Apr;45(4):619-24. doi: 10.1161/01.HYP.0000158838.34131.30. Epub 2005 Feb 21.
In many hypertensive patients, left ventricular pump function is normal at rest but abnormal during exercise. Myocardial dysfunction or altered left ventricular loading may be responsible for this finding. To verify the hypothesis of impaired myocardial functional reserve in the hypertensive heart, we assessed the response of stress-adjusted midwall shortening to graded, low-dose dobutamine infusion in hypertensive subjects with normal midwall shortening at rest. Sixty-five subjects (45 never treated hypertensive subjects and 20 normotensive volunteers comparable for age) received dobutamine at 1, 2, 3, 4, and 5 microg x kg(-1) x min(-1) for 5-minute steps; within this range of infusion rates, heart rate and systemic blood pressure were stable. Two-dimensional, M-mode, and Doppler echocardiography were performed at baseline and at the end of each step. In normotensive controls, midwall shortening increased from baseline during 2 microg x kg(-1) x min(-1) dobutamine by an average of 16+/-4.5% (P<0.01); a value of 2 standard deviations below this mean response was taken as the lower limit of normal. In the hypertensive subjects, 24 had a normal midwall shortening response to dobutamine at this dose (group I) and 21 had a subnormal response (group II). Whereas blood pressure and left ventricular mass were similar in group II and group I, the former had greater relative wall thickness (P<0.01) than the latter. beta-adrenergic stimulation by very-low-dose dobutamine unmasks subtle impairment of myocardial functional reserve in hypertensive subjects with normal myocardial performance at rest. This alteration seems to be related mainly to increase in left ventricular relative wall thickness.
在许多高血压患者中，左心室泵功能在静息时正常，但运动时异常。心肌功能障碍或左心室负荷改变可能是这一发现的原因。为了验证高血压心脏中心肌功能储备受损的假设，我们评估了静息时中壁缩短正常的高血压受试者在静脉输注不同剂量多巴酚丁胺时，压力校正的中壁缩短的反应。65名受试者（45名未经治疗的高血压患者和20名年龄匹配的血压正常志愿者）接受了多巴酚丁胺静脉输注，输注速率分别为1、2、3、4和5μg·kg-1·min-1，每个速率持续5分钟；在此输注速率范围内，心率和体循环血压保持稳定。在基线和每个输注阶段结束时进行二维、M型和多普勒超声心动图检查。在血压正常的对照组中，在输注2μg·kg-1·min-1多巴酚丁胺时，中壁缩短较基线平均增加16±4.5%（P<0.01）；低于该平均反应2个标准差的值被视为正常下限。在高血压受试者中，24名在该剂量下对多巴酚丁胺的中壁缩短反应正常（I组），21名反应低于正常（II组）。II组和I组的血压和左心室质量相似，但II组的相对室壁厚度大于I组（P<0.01）。极低剂量多巴酚丁胺的β肾上腺素能刺激揭示了静息时心肌功能正常的高血压受试者存在细微的心肌功能储备受损。这种改变似乎主要与左心室相对室壁厚度增加有关。
