Shimizu Wataru, Tanabe Yasuko, Aiba Takeshi, Inagaki Masashi, Kurita Takashi, Suyama Kazuhiro, Nagaya Noritoshi, Taguchi Atsushi, Aihara Naohiko, Sunagawa Kenji, Nakamura Kazufumi, Ohe Tohru, Towbin Jeffrey A, Priori Silvia G, Kamakura Shiro
Division of Cardiology, Department of Internal Medicine, National Cardiovascular Center, Suita, Osaka, Japan.
J Am Coll Cardiol. 2002 Jun 19;39(12):1984-91. doi: 10.1016/s0735-1097(02)01894-6.
This study compared the effects of beta-blockade on transmural and spatial dispersion of repolarization (TDR and SDR, respectively) between the LQT1 and LQT2 forms of congenital long QT syndrome (LQTS).
The LQT1 form is more sensitive to sympathetic stimulation and more responsive to beta-blockers than either the LQT2 or LQT3 forms.
Eighty-seven-lead, body-surface electrocardiograms (ECGs) were recorded before and after epinephrine infusion (0.1 microg/kg body weight per min) in the absence and presence of oral propranolol (0.5-2.0 mg/kg per day) in 11 LQT1 patients and 11 LQT2 patients. The Q-T(end) interval, the Q-T(peak) interval and the interval between T(peak) and T(end) (T(p-e)), representing TDR, were measured and averaged from 87-lead ECGs and corrected by Bazett's method (corrected Q-T(end) interval [cQT(e)], corrected Q-T(peak) interval [cQT(p)] and corrected interval between T(peak) and T(end) [cT(p-e)]). The dispersion of cQT(e) (cQT(e)-D) was obtained among 87 leads and was defined as the interval between the maximum and minimum values of cQT(e).
Propranolol in the absence of epinephrine significantly prolonged the mean cQT(p) value but not the mean cQT(e) value, thus decreasing the mean cT(p-e) value in both LQT1 and LQT2 patients; the differences with propranolol were significantly larger in LQT1 than in LQT2 (p < 0.05). The maximum cQT(e), minimum cQT(e) and cQT(e)-D were not changed with propranolol. Propranolol completely suppressed the influence of epinephrine in prolonging the mean cQT(e), maximum cQT(e) and minimum cQT(e) values, as well as increasing the mean cT(p-e) and cQT(e)-D values in both groups.
Beta-blockade under normal sympathetic tone produces a greater decrease in TDR in the LQT1 form than in the LQT2 form, explaining the superior effectiveness of beta-blockers in LQT1 versus LQT2. Beta-blockers also suppress the influence of sympathetic stimulation in increasing TDR and SDR equally in LQT1 and LQT2 syndrome.
本研究比较了β受体阻滞剂对先天性长QT综合征（LQTS）的LQT1型和LQT2型复极的跨壁离散度和空间离散度（分别为TDR和SDR）的影响。
LQT1型比LQT2型或LQT3型对交感神经刺激更敏感，对β受体阻滞剂反应更明显。
在11例LQT1患者和11例LQT2患者中，于肾上腺素输注（0.1微克/千克体重每分钟）前后，在无口服普萘洛尔（0.5 - 2.0毫克/千克每天）和有口服普萘洛尔的情况下记录87导联体表心电图（ECG）。从87导联ECG测量并平均代表TDR的Q-T（终末）间期、Q-T（峰）间期以及T（峰）与T（终末）之间的间期（T（p-e）），并用Bazett法校正（校正后的Q-T（终末）间期[cQT（e）]、校正后的Q-T（峰）间期[cQT（p）]以及校正后的T（峰）与T（终末）之间的间期[cT（p-e）]）。在87导联中获得cQT（e）的离散度（cQT（e）-D），定义为cQT（e）的最大值与最小值之间的间期。
在无肾上腺素时，普萘洛尔显著延长了LQT1和LQT2患者的平均cQT（p）值，但未延长平均cQT（e）值，从而降低了平均cT（p-e）值；LQT1患者中普萘洛尔的差异比LQT2患者显著更大（p < 0.05）。普萘洛尔未改变最大cQT（e）、最小cQT（e）和cQT（e）-D。普萘洛尔完全抑制了肾上腺素对延长平均cQT（e）、最大cQT（e）和最小cQT（e）值以及增加两组平均cT（p-e）和cQT（e）-D值的影响。
在正常交感神经张力下，β受体阻滞剂对LQT1型TDR的降低作用大于LQT2型，这解释了β受体阻滞剂在LQT1型中比在LQT2型中疗效更佳的原因。β受体阻滞剂还能抑制交感神经刺激对LQT1和LQT2综合征中TDR和SDR增加的影响。
