1. Using New High-Resolution 4D Echocardiography
An Image Based Evaluation of Dynamic Heart Function Following Different Cardiopulmonary Bypass Techniques,
Using New High-Resolution 4D Echocardiography
Priyanka Vachhani; Rohini Deb; Shahryar Ashraf; Kaavya Mandi; Kevin Truong; Lydia Tam; Vivian Chen; Jiahui Zhang;
Cole Streiff, BA; Meihua Zhu, MD, PhD; Stephen Langley, MD; Muhammad Ashraf, MD; David J Sahn, MD, FAHA
Oregon Health & Science University, Portland, OR, USA
ABSTRACT
Background: In this study, we evaluated the impact of different cardiopulmonary bypass methods on dynamic heart function.
Methods: We studied 12 open-chest piglets (3-5kg). Body temperature, oxygen saturation, blood gases and vital signs were continually monitored. Baseline 4D full volume image loops were acquired from the heart surface with a 4Z1c matrix transducer on a Siemens SC 2000 ultrasound system at frame rate > 30 VPS. Five piglets were subjected to cross-circulation cardiopulmonary bypass for 2 hours using an adult matched donor. Seven piglets were subjected to conventional bypass for the same duration, 3 with matched blood at body temperature (normothermic) and 4 with matched hypothermic blood. After 2 hours of bypass, normal circulation was restored, 4D images acquired after stabilization and images were analyzed offline using VMM motion analysis software from Siemens.
Results: In piglets with cross-circulation, average peak apical and basal rotation was slightly increased ( °) and average peak strain (both circumferential and longitudinal) values were diminished in all segments ( %, p=0.039). Piglets with normothermic cardiopulmonary bypass showed similar mechanical changes in LV strain and rotation (p=0.017). Piglets with hypothermic bypass, however, showed a greater increase in LV rotation ( °) and greater depression of strain values ( %).
Conclusion: New 4D echo is feasible to monitor dynamic heart function after cardiopulmonary bypass.
BACKGROUND
Myocardial dysfunction is a known complication of open-heart surgery and is believed to result from stunning of the inter-ventricular septum. It is believed to be caused by myocardial ischemia and/or inflammatory response, and has been linked to duration of surgical procedure and adequacy of myocardial protection during surgery. Despite recent advances in myocardial protection and surgical techniques, septal dysfunction is not an infrequent finding and sometimes requires highly invasive monitoring in the postoperative period.
The main aim of this study was to compare different methods of cardiopulmonary bypass for superior myocardial protection during surgery and to minimize the cardiac dysfunction in postoperative period. Recent developments in cardiac imaging have made it possible to quantify mechanical indices of heart function non-invasively. We also sought to test the usefulness of high-resolution strain imaging to monitor dynamic heart function in the postoperative period
METHODS
We studied 12 open-chest piglets (3-5kg). Body temperature, oxygen saturation, blood gases and vital signs were continually monitored. Baseline 4D full volume image loops were acquired from the heart surface with a 4Z1c matrix transducer on a Siemens SC 2000 ultrasound system at frame rate > 30 VPS.
Five piglets were subjected to cross-circulation cardiopulmonary bypass for 2 hours using an adult matched donor. Seven piglets were subjected to conventional bypass for the same duration, 3 with matched blood at body temperature (normothermic) and 4 with matched hypothermic blood. After 2 hours of bypass, normal circulation was restored, 4D images acquired after stabilization and images were analyzed offline.
Images were analyzed by tracing the motion of the left ventricle and using VMM motion analysis software from Siemens to look for any quantifiable changes in strain or rotation. We specifically looked for changes in the left ventricle to see if there are any mechanical alteration in either longitudinal or circumferential strain as well as if there were any changes in rotation.
A paired t-test was used to determine statistical significance.
RESULTS
Mean base rotation for baseline cross-circulation vs. post was ± vs ± The p-value was , indicating good correlation. Mean apex rotation and mean mid circumferential strain for normothermic  vs. hypothermic was ± vs ± and ± vs ± respectively.  The p value for this statistic was and indicated good correlation.
In piglets with cross-circulation, average peak apical and basal rotation was slightly increased ( °) and average peak strain (both circumferential and longitudinal) values were diminished in all segments ( %, p=0.039). Piglets with normothermic bypass showed similar mechanical changes in LV strain and rotation (p=0.017). Piglets with hypothermic bypass, however, showed a greater increase in LV rotation ( °) and greater depression of strain values ( %).
CONCLUSIONS
Despite improved surgical techniques and myocardial protection during open heart surgery, myocardial stunning causing septal dysfunction is not infrequent. Speckle tracking based evaluation of LV twist on high resolution dynamic ultrasound images has shown a direct relationship with cardiac output in this study and may provide tools to evaluate and monitor cardiac function post operatively.
There is statistically significant evidence showing that piglets exposed to hypothermic bypass demonstrated less depression of LV rotation and strain values as compared to those subjected to normothermic cardiac bypass.
Segmental dysfunction as indicated by depression of segmental strain and rotation was more prominent in interventricular septum in the normothermic group, which showed time to peak contraction increased
Basal rotation in piglets slightly increased for both normothermic and hypothermic cases. Average peak strain values were diminished across all segments.
The new 4D echo tested in this study is feasible to monitor dynamic heart function after cardiopulmonary bypass.
DISCLOSURES
No relationships to disclose:
Priyanka Vachhani
Rohini Deb
Shahryar Ashraf
Kaavya Mandi
Kevin Truong
Lydia Tam
Vivian Chen
Jiahui Zhang
Cole Streiff
Meihua Zhu
Stephen Langley
Muhammad Ashraf
David J Sahn