Background: The role of pericardium in left ventricular (LV) twist has not been directly investigated. We sought to determine the role of pericardium in maintenance of LV twist function in an animal experiment, before and after pericardial opening.
Methods: 13 mongrel dogs were initially operated on, but two dogs were excluded from the final analyses owing to poor speckle tracking. Intraoperative echocardiography for conventional and speckle tracking measurements was performed at baseline with intact pericardium, and after pericardial opening. Using the speckle tracking technique, LV twist and strains were obtained before and after pericardial opening in 11 animals and additionally after pericardial repair in five animals.
Results: LV twist was significantly decreased after pericardial opening (10.1 degrees (5.1 degrees ) to 7.4 degrees (6.4 degrees ), p=0.001). LV twist and untwist rate were also decreased (115.0 degrees (99.6 degrees )/s to 66.7 degrees (42.5 degrees )/s for twist rate, -127.6 degrees (74.3 degrees )/s to -84.2 degrees (734 degrees )/s for untwist rate, p=0.015 and 0.009, respectively). LV stroke volume and ejection fraction were similar irrespective of pericardial opening, but radial strain measured at the mid ventricular level was significantly increased (31.7% (17.4%) to 32.3% (24.0%), p=0.02) after pericardial opening without changes in circumferential and longitudinal strains. LV twist degree was restored after pericardial repair.
Conclusion: The pericardium is an important structure for maintaining LV twist. Given no significant impact of the presence or absence of pericardium on LV systolic performance, an increase in LV radial strain serves as a compensatory mechanism to preserve LV systolic function despite a decrease in LV twist in the absence of pericardium.