Black Adam, Ewert Dan, Mulligan Lawrence J
Medtronic, Inc., Mounds View, MN 55112, USA.
Annu Int Conf IEEE Eng Med Biol Soc. 2009;2009:2904-6. doi: 10.1109/IEMBS.2009.5334445.
Intracellular regulation of myocardial Ca2+ has long been of interest to physiologists. The force-interval relationship provides a phenomenological approach that permits insight into aspects of calcium regulation. The response to an extrasystole is a potentiation in contractile force and the recovery in contractile force is described by the recirculation fraction (RF). The RF provides a gross estimation of calcium uptake by sarcoplasmic reticulum (SR), leading to myocardial relaxation. The current study focused on the relationship of right (RV) and left ventricular (LV) RF in canines under several contractile states. Anesthetized canines (n = 5) were catheterized for RV and LV pressure measurements. dP/dt(max) for the RV and LV was calculated for three baseline beats, one extrasystole and the first five postextrasystolic beats. The relationship between the LV dP/dt(max) and RV dP/dt(max) for all of the mentioned beats was then examined. Contractility was increased with calcium chloride and extrasystoles were delivered. Once cardiac function returned to a baseline level, contractility was reduced by increasing the concentration of isoflurane and the evaluation repeated. All ventricular contractions were controlled by RA pacing to maintain intrinsic conduction. A strong linear relationship between RV and LV dP/dt(max) (r = 0.94 +/- .06) existed for most canine's contractile states. These results build on findings in isolated hearts and demonstrate that biventricular response to extrasystoles and subsequent contractile recovery is both linear and correlated, suggesting that intracellular calcium regulation in a given heart across contractile state is static.
心肌细胞内钙离子的调节长期以来一直是生理学家感兴趣的课题。力-间期关系提供了一种现象学方法，有助于深入了解钙调节的各个方面。对期外收缩的反应是收缩力增强，收缩力的恢复用再循环分数（RF）来描述。RF提供了对肌浆网（SR）钙摄取的大致估计，从而导致心肌舒张。当前的研究聚焦于犬在几种收缩状态下右心室（RV）和左心室（LV）RF的关系。对5只麻醉犬进行插管以测量RV和LV压力。计算RV和LV的三个基线搏动、一个期外收缩以及期外收缩后的前五个搏动的dP/dt（最大值）。然后检查所有上述搏动的LV dP/dt（最大值）和RV dP/dt（最大值）之间的关系。通过氯化钙增加收缩力并施加期外收缩。一旦心功能恢复到基线水平，通过增加异氟烷浓度降低收缩力并重复评估。所有心室收缩均由右心房起搏控制以维持固有传导。在大多数犬的收缩状态下，RV和LV dP/dt（最大值）之间存在很强的线性关系（r = 0.94±0.06）。这些结果基于在离体心脏中的发现，表明双心室对期外收缩和随后收缩恢复的反应是线性且相关的，这表明给定心脏在不同收缩状态下的细胞内钙调节是稳定的。
