Funnel-tipped aortic cannula for reduction of atheroemboli.

BACKGROUND: Atheroemboli caused by aortic manipulation poses a risk for stroke in patients undergoing cardiopulmonary bypass (CPB) surgery. One potential cause is the high velocity jet from aortic perfusion cannulae. This study describes the flow patterns of a novel funnel-tip cannula designed to reduce emboli by decreasing fluid velocity and resultant shear force on the aortic wall. METHODS: A funnel-tip cannula was constructed and compared with standard straight-tip cannulae and the Dispersion (Research Medical Inc, Midvale, UT) and Sarns Soft Flow (Terumo Cardiovascular Systems Corp, Ann Arbor, MI) cannulae. Pressure drop measurements were collected at 1 to 6 L/minute flows. Velocity flow profiles were created using phase contrast magnetic resonance imaging. Absolute velocity was measured in a phantom aorta at 5 L/minute flow. Each cannula was further studied in a synthetic model of an atherosclerotic aorta to determine the mass of dislodged particulate matter generated at 2, 3, and 5 L/minute flows. RESULTS: The funnel-tip cannula demonstrated significantly lower values (p < 0.05) in pressure drop (55 mm Hg), exit velocity (309 cm/second, 167 cm/second for center axis and wall, respectively), and particulate dislodgement (0.15 +/- 0.05 g) than other tested cannulae. The Soft Flow cannula generated the next lowest pressure drop but exhibited twice the exit velocity and particulate dislodgement of the funnel-tip cannula. The Dispersion cannula did not demonstrate a reduction in velocity or particulate dislodgement compared with the standard straight-tip cannulae. CONCLUSIONS: The results of this study suggest that a low-angled funnel-tip cannula has favorable flow characteristics warranting further investigation. Design development may reduce the risk of atheroemboli generation during CPB surgery.

Percutaneous therapies for valvular heart disease.

Balloon valvuloplasty has been in clinical use for over 20 years, but the prospect of repairing and replacing cardiac valves via catheter-based techniques represents a truly recent development. This review introduces evolving technologies and their relevance to cardiovascular pathologists.

A stentless trileaflet valve from a sheet of decellularized porcine small intestinal submucosa.

PURPOSE: The purpose of this study was to investigate the function of a trileaflet pulmonary valve constructed from a sheet of porcine small intestinal submucosa. DESCRIPTION: In four sheep, the native pulmonary valve and a segment of the pulmonary trunk was excised and replaced with a trileaflet valve constructed from decellularized porcine small intestinal submucosa. The valve construct was created from a sheet of the xenograft material by a method of involuting flaps of tissue inside a cylinder of itself. The function of the valve was assessed by echocardiography, catheter pullback across the valve, and observation of an excised valve in a flow simulator. EVALUATION: The valve constructs exhibited low gradients and symmetrical leaflet movement with good mobility when tested under physiologic conditions in an acute sheep model. CONCLUSIONS: This method offers a means to create a functional trileaflet valve replacement from a sheet of tissue.

Optimization of vessel orientation for robotic coronary artery bypass grafting.

The availability of telemanipulation robots has not yet resulted in the emergence of a reliable endoscopic coronary bypass procedure. A major challenge in performing a closed-chest coronary operation is creating a high-quality anastomosis in a reasonable period of time. In this experimental study, the impact of distal vessel orientation on the speed and accuracy of anastomosis was quantifed. We found that vessel orientation and the relative angle of the surgical plane influence anastomosis speed, the trauma to the vessel, the accuracy of stitch placement, and the eventual achievement of hemostasis. Our results suggest that the speed and accuracy of a robotically performed anastomosis of a vessel graft to a coronary artery can be improved by making small changes in vessel orientation. Vessels should be positioned between the horizontal and diagonal orientation and inclined between the horizontal and +45 degrees . Because the 6-o'clock stitch is particularly challenging, surgeons may benefit from an orientation that moves the heel or the toe of the anastomosis away from this critical position.

Continuous addition of adenosine with a micropump system improves warm whole blood cardioplegia.

BACKGROUND: Micropump additive systems allow for continuous modification of cardioplegia composition during heart surgery. Although the use of such systems in warm heart surgery is theoretically desirable, the role of the systems has been clinically limited by coronary vasoreactivity with higher potassium concentration and unreliable mechanical arrest at lower potassium concentration. Adenosine, a potent coronary vasodilator and arresting agent, has the potential to reduce the potassium concentration required for arrest and to improve distribution of cardioplegia. However, clinical use of adenosine has been limited by a short half-life in blood and difficulty in titrating the dose. This study tested the hypothesis that continuous addition of adenosine with an in-line linear micropump system would facilitate whole blood hyperkalemic perfusion for cardiac surgery. METHODS: Canine hearts (n = 9) were randomized to 20 minutes of arrest with whole blood cardioplegia or cardioplegia with adenosine at either low (0.5 M) or high (8 M) concentration. Potassium was supplemented at an arresting dose (24 mEq/L) for 5 minutes and then at a maintenance dose (6 mEq/L) for an additional 15 minutes. Coronary flow was held constant (4 mL/kg per minute), and aortic root pressure was measured. Myocardial performance was assessed by measurement of the end-diastolic pressure to stroke volume relationship at constant afterload. Myocardial tissue perfusion was evaluated with colored microspheres. RESULTS: During the initial period of high-concentration potassium arrest, coronary resistance rose progressively regardless of adenosine addition. Coronary resistance remained elevated during the period of low potassium perfusion, except when high-concentration adenosine was added. With addition of 8 M adenosine, coronary resistance returned to baseline, and left ventricular endocardial perfusion was augmented. Electromechanical quiescence improved with adenosine perfusion and was complete with high-dose adenosine addition. Function was preserved in all hearts. CONCLUSION: Use of a modern micropump system allowed for continuous addition of adenosine and potassium to whole blood cardioplegia. Adenosine minimized potassium-induced coronary vasoconstriction and improved endocardial perfusion and mechanical quiescence. These findings supported addition of adenosine to the perfusate during warm whole blood cardioplegia.

Endoscopic multivessel coronary artery bypass grafting using automated device for proximal anastomosis.

BACKGROUND: The use of computer-enhanced telemanipulation robots in cardiothoracic surgery can reduce the need for open surgical access and enable closed-chest, endoscopic procedures, but these procedures hav e been limited to anterior target vessels. The feasibility of fully endoscopic multivessel, coronary artery bypass grafting (CABG) was examined. METHODS: Fully endoscopic, multivessel CABG solely through surgical ports was performed on 23 dogs weighing 75 to 85 pounds. A proximal anastomosis was made with the Symmetry bypass system aortic connector. The aorta was cross clamped, and cardioplegia solution was administered through the vein graft into the ascending aorta. RESULTS: Eighteen of 23 procedures yielded successful proximal anastomoses and 1 to 3 distal anastomoses. CONCLUSION: Endoscopic anastomosis to the ascending aorta is feasible with the Symmetry bypass connector. Antegrade cardioplegia and aortic root venting can then be easily accomplished. This approach simplifies closed chest cardioplegic arrest for mulitivessel CABG.