Related Experiment Videos
Vertical displacement of the beating heart by the octopus tissue stabilizer: influence on coronary flow
P F Gründeman1, C Borst, J A van Herwaarden
1Department of Cardiology, Heart Lung Institute, Utrecht University Hospital, The Netherlands. exp.cardio@hli.azu.nl
Insights
During beating heart surgery, retracting the heart to access coronary arteries did not cause mechanical obstruction. Restoring blood flow after retraction suggests preload augmentation, not obstruction, impacts coronary flow.
Area of Science:
- Cardiovascular Surgery
- Cardiac Physiology
Background:
- Biventricular pump failure in beating heart coronary artery bypass graft (CABG) operations may stem from mechanical obstruction of coronary flow.
- Sternotomy for posterior circumflex branch access can lead to such issues.
Purpose of the Study:
- To investigate if anterior displacement of the beating heart during CABG surgery mechanically obstructs coronary blood flow.
- To determine the impact of heart retraction on coronary perfusion and cardiac output.
Main Methods:
- Regional coronary blood flow was measured in anesthetized, paced, beta-blocked pigs.
- The beating heart was fully retracted to simulate surgical conditions.
- Cardiac output, mean arterial pressure, and coronary blood flow in major coronary arteries were assessed.
Main Results:
- Heart displacement significantly decreased cardiac output (42%), mean arterial pressure (48%), and coronary blood flow in the left anterior descending (34%), right (25%), and circumflex (50%) coronary arteries.
- Relative circumflex coronary artery flow was notably lower than combined LAD and RCA flows.
- Trendelenburg positioning (head-down tilt) restored cardiac output, mean arterial pressure, and coronary blood flow.
Conclusions:
- Mechanical obstruction of coronary blood flow is unlikely during anterior heart displacement in beating heart surgery.
- The restoration of coronary flow with increased preload (Trendelenburg) indicates that preload, not mechanical obstruction, is the primary factor influencing coronary perfusion during retraction.
Background:
In beating heart coronary artery bypass graft operations, biventricular pump failure, as observed after exposure of the posterior circumflex branches by sternotomy, may originate from mechanical obstruction to coronary flow.
Methods:
Regional coronary blood flow was measured in 8 anesthetized, paced, beta-blocked pigs, and the beating heart was fully retracted.
Results:
Displacement decreased cardiac output from 4.8 +/- 1.1 L/min (mean +/- standard deviation) to 2.8 +/- 1.2 L/min (p < 0.001), a 42% +/- 6% decrease that resulted in a decrease in mean arterial pressure by 48% +/- 6% (mean +/- standard error of the mean; p < 0.001) and a reduction in coronary blood flow in the left anterior descending coronary artery, the right coronary artery, and the circumflex coronary artery by 34% +/- 6%, 25% +/- 8%, and 50% +/- 10%, respectively (all p < 0.05 versus baseline). Relative circumflex coronary artery flow was 20.1% +/- 8.3% lower than the combined relative value of left anterior descending coronary artery and right coronary artery flows (p = 0.046). Subsequent 20 degrees head-down tilt significantly increased ventricular preload pressures and restored cardiac output and mean arterial pressure as well as coronary blood flow.
Conclusions:
It is inferred that coronary blood flow was not mechanically obstructed during anterior displacement of the porcine beating heart, because augmentation of preloads by the maneuver of Trendelenburg restored coronary flow parallel to the recovery of cardiac output and mean arterial pressure while the heart remained retracted by 90 degrees.