兔心脏压力超负荷左心室肥大的电学和形态学改变

Electrical and morphological changes of cardiac pressure over-load left ventricular hypertrophy in rabbits

目的观察兔心脏压力超负荷左心室肥大(LVH)发展过程中心电图(ECG)的电学改变能否早于超声心动图(UCG)的形态学改变,进一步探讨ECG在高血压性LVH早期诊断中的意义。方法日本大耳白兔40只,随机分成实验组25只和对照组15只。实验组采用肾上腹主动脉次全结扎法建立心脏压力超负荷LVH模型,对照组除不行腹主动脉缩窄外,其余处理同实验组。两组兔均于术前及术后2、4、6、8周测量血压,描记同步12导联ECG并测量各导联R波和QRS波的振幅、心电轴、QRS波时限和QTc间期;同时做超声心动图,测量室间隔及左心室下后壁厚度、左心室收缩和舒张末期内径以及心功能等参数。术前及术后8周拍摄X线胸片,测量心胸比值。之后处死动物,取左心室测量其质量指数,并进行病理检查。结果实验组兔术后血压逐渐上升,X线下心胸比值增加,左心室质量指数增大,病理所见心肌细胞肥大,部分变性或坏死。超声所见:左心室下壁、后壁及室间隔厚度术后即逐渐增大,E/A逐渐降低,4周后与对照组相比差异有统计学意义(P<0.05);左心室收缩和舒张末期内径术后4周始逐渐增大,6周后与对照组相比差异有统计学意义(P<0.05);左心室射血分数逐渐降低,术后8周与对照组相比差异有统计学意义(P<0.05)。ECG表现:心电图Ⅱ、Ⅲ、aVF及胸前各导联术后R波及QRS波振幅逐渐增高,术后2周开始与对照组相比差异均有统计学意义(P<0.05);QRS波时限和QTc术后呈逐渐递增趋势,4周后与对照组相比差异有统计学意义(P<0.05)。对照组兔上述各指标术前、术后差异无统计学意义。结论在兔压力超负荷LVH发展过程中,ECG电学改变早于UCG反映的结构改变,ECG对高血压性LVH具有一定的早期诊断价值。

Objective To observe whether the changes of electrocardiogram （ECG） is earlier than the morphological changes of ultrasonic cardiogram （UCG） during the development of cardiac pressure over-load left ventricular hypertrophy （LVH） in rabbits, so as to discuss the value of ECG in the early diagnosis of hypertensive LVH. Methods Forty male Japanese rabbits were randomly divided into experimental group （n=25） and control group （n=15）. Rabbits in the experimental group were used to establish cardiac pressure over-load LVH model by subtotal ligation of suprarenal abdominal aorta. The control group received the same treatment as that in the experimental group except for the coarctation of abdominal aorta. Before operation and the 2nd, 4th, 6th, and 8th week after operation, 12-lead ECG were recorded to measure R-wave and QRS complex wave amplitude, heart electric axis, QRS duration and QTc period; UCG was performed to detect the thickness of left ventricular inferior wall （LVIW）, posterior wall （LVPW） and interventricular septum （IVS）, left ventricular end diastolic diameter （LVDd）, left ventricular end systolic diameter （LVDs）, E/A ratio and left ventricular ejection fraction （LVEF）. Before operation and the 8th week after operation, chest X-ray examination was performed to detect cardiothoracic ratio. Then all the rabbits were sacrificed. Left ventricular mass indices （LVMI） were measured and cardiac pathological examination was performed. Results The blood pressure of rabbits increased gradually after operation in the experimental group, the cardiothoracic ratio and LVMI aggrandized, and the cardiomyocytes hypertrophy, denaturalization or necrosis were observed under microscope in the experimental group. The thickness of LVIW, LVPW and IVS of rabbits in the experimental group increased gradually, and the E/A ratio decreased gradually, showing significant difference when compared to those of the control group at the 4th week （P〈0.05）. LVDd and LVDs of rabbits in the experimental group increased from the 4th week, and were significantly larger than that of the control group after the 6th week （P〈0.05）. LVEF of rabbits in the experimental group decreased gradually, showing significant difference when compared with the control group at the 8th week （P〈0.05）. R-wave and QRS complex wave amplitudes in Ⅱ, Ⅲ, aVF and chest leads in ECG of the experimental group increased gradually, and became significantly higher than those of the control group at the 2th week （P〈0.05）. QRS duration and QTc increased gradually after operation, showing significant difference compared to that of the control group at the 4th week （P〈0.05）. The above mentioned indices had no significant change before or after operation in control group （P〉0.05）. Conclusion During the development of cardiac pressure over-load LVH of rabbits, the electrical changes of ECG are earlier than the morphologic changes of UCG, which indicates that ECG may has a value for early diagnosis of the hypertensive LVH.