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Flow measurements through aortocoronary and intraluminal coronary shunts
C Jaggy1, M Lachat, B Leskosek
1Clinic for Cardiovascular Surgery, University Hospital Zurich.
Insights
Coronary artery bypass grafting (CABG) on a beating heart can be optimized with shunts. Specific aortocoronary and intraluminal shunts provide adequate myocardial protection at appropriate pressure heads.
Area of Science:
- Cardiovascular Surgery
- Biomedical Engineering
- Medical Devices
Background:
- Coronary artery bypass grafting (CABG) on a beating heart requires adequate myocardial protection.
- Temporary shunts may offer the necessary minimal flow (40-60 ml/min) for myocardial protection during beating heart CABG.
Purpose of the Study:
- To investigate the flow characteristics of different shunts under varying pressure conditions.
- To determine the pressure head required for adequate flow through aortocoronary and intraluminal shunts.
Main Methods:
- Three aortocoronary shunts (2, 3, and 4 mm bulb sizes) and one intraluminal shunt (4 mm bulb size) were tested.
- Shunts were perfused with a glycerin solution at 37°C, with preload varied from 35-80 mmHg and afterload fixed at 12 mmHg.
- Regression analysis was used to correlate flow rate with pressure head.
Main Results:
- Flow rates varied significantly between shunt types and sizes.
- A preload of 70 mmHg was needed for the 3mm aortocoronary shunt, 50 mmHg for the 4mm aortocoronary shunt, and 45 mmHg for the intraluminal shunt to achieve 40 ml/min flow.
- All shunts demonstrated a statistically significant relationship between pressure head and flow (p < 0.0001).
Conclusions:
- The 3mm and 4mm aortocoronary shunts and the intraluminal shunt can provide adequate myocardial protection at sufficient pressure heads.
- The intraluminal shunt may not guarantee protection in severe proximal coronary stenosis, primarily offering a bloodless field.
- Shunt insertion is a cost-effective and straightforward method to enhance beating heart CABG procedures.
Aims:
Temporary insertion of shunts during coronary artery bypass grafting (CABG) on the beating heart may provide the minimal flow required for adequate myocardial protection (40 to 60 ml/min). We investigated the flow as a function of the pressure head over three aortocoronary shunts and one intraluminal coronary shunt.
Methods:
The aortocoronary shunts (VS-01590 with bulb size 2, 3 and 4 mm) and the intraluminal shunt (IVS-4030, bulb size 4 mm) were perfused with 47% glycerin solution at 37 degrees C. The preload was raised in 5 mmHg steps from 35 to 80 mmHg. The afterload was set at 12 mmHg. A regression analysis of the flow on the pressure head was performed.
Results:
For maximal preload the flow through the aortocoronary shunts was 15.9 +/- 1.3, 46.2 +/- 2.2 and 75.4 +/- 3.3 ml/min, for the intraluminal shunt it was 76.1 +/- 3.4 ml/min. To provide a flow of 40 ml/min a preload of 70, 50 and 45 mmHg was necessary for the 3 mm and 4 mm aortocoronary shunt and the intraluminal shunt respectively. For the aortocoronary and the intraluminal shunts the beta-coefficients were 0.27, 0.66, 1.13 and 1.02 ml/(min*mmHg) respectively with all p < 0.0001.
Conclusions:
For adequate pressure head the 3 mm and 4 mm aortocoronary shunt and the intraluminal shunt provide myocardial protection. In case of severe proximal coronary stenosis the intraluminal shunt will not guarantee myocardial protection and main benefit reduces to working in a bloodless field. The insertion of shunts is a cheap and simple method to optimize CABG on the beating heart.