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Eur J Cardiothorac Surg 2000;17:505-508
© 2000 Elsevier Science NL

Intraoperative flow measurement in composite Y arterial grafts

^a Department of Cardiovascular Surgery, Villa Azzurra, Rapallo, Genova, Italy
^b Department of Cardiovascular Surgery, Università La Sapienza, Rome, Italy

Corresponding author. Vicolo Bravetta, 8, 00164 Rome, Italy. Tel.: +39-6-446-1989; fax: +39-6-6615-6267
e-mail: g.speziale{at}libero.it

	Abstract

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion Appendix A Conference discussion References

 
Objective: Total arterial myocardial revascularization may be achieved by using the ‘Y-graft’ techniques with different free arterial conduits anastomosed off the side of an in situ internal thoracic artery to reach distal coronary segments. This study was assessed to measure intraoperative graft flow, resistance and clinical outcomes. Methods: Seventy-six patients who underwent coronary artery bypass grafting during a time period of 27 months were enrolled in this prospective study. All patients received sequential grafting by using both internal thoracic arteries, inferior epigastric and right gastroepiploic artery joined as a composite Y graft. Intraoperative graft flow, resistance and derived variables were measured. Results: All patients except one showed good flow (ml/min and waveform) in either branch of composite graft. In one case, a low-flow situation through the graft was registered requiring surgical correction. Temporary occlusion of either branch did not significantly affect flow in the other side of the arterial Y. Mid-term follow-up (3 and 15 months) and angiographic studies showed a high graft patency rate. Conclusion: Composite arterial grafts provide excellent early and mid-term clinical results. Flow reserve of the left internal thoracic artery did not affect blood flow and resistance on either branch of the Y graft when temporary occlusion on the other side of the arterial Y was performed.

Key Words: Coronary bypass graft • Internal thoracic artery • Blood flow measurement • Composite coronary graft • Coronary flow reserve

	1. Introduction

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion Appendix A Conference discussion References

 
In the last few years, the superior results of coronary revascularization with the internal thoracic artery (ITA) have led to a significant development in techniques to extend arterial revascularization procedures [1–3]. The Y- and T-graft techniques have developed, with different free arterial conduits anastomosed off the side of an in situ ITA to reach distal coronary segments. The mid-term follow-up of patients operated on composite coronary artery bypass grafting (CABG) showed excellent graft patency rate [4,5]. The inferior epigastric artery (IEA), right gastroepiploic artery (RGEA) and radial artery (RA) were used to fashion an ‘arterial Y’ off the side of an in situ ITA graft. Recently, the use of both ITA grafts reduced the incidence of morbidity associated with harvesting other arterial conduits [6–9]. Since usually more than two anastomoses are required, Y-composite grafting uses a sequential grafting technique. However, the hypotheses that the flow reserve of pedicled ITA may not provide sufficient blood flow for extended left ventricular revascularization has so far not been investigated.

The aim of this study was to evaluate the results of composite graft construction with a left ITA and a segment of IEA or RGEA. Intraoperative flow measurements through the ‘Y-graft’ were used to determine the effect that pedicled ITA flow reserve and native coronary run-off have on the flow distribution through the distal anastomoses.

	2. Materials and methods

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion Appendix A Conference discussion References

 
2.1. Patients
Seventy-six patients (52 males, 24 females, mean age 67 years, range 44–76 years) with coronary artery disease were enrolled in a prospective study and underwent CABG during a time period of 27 months. The following exclusion criteria were used: (1) left ventricular dysfunction (ejection fraction <0.25); (2) patients with associated cardiac valve procedures; (3) peripheral vascular disease; (4) re-do procedures; (5) patients with left ventricular aneurysm.

2.2. Surgical technique
Surgery was performed through a standard median sternotomy. Left ITA, RGEA and left IEA were harvested using a skeletonized technique. Patients were heparinized (300 IU/kg), the conduits were injected with warm papaverine hydrochloride solution, and the Y anastomosis was performed with a continuous 8-0 polypropylene suture. Standard cannulation in the distal ascending aorta and in the right atrium with a double-stage venous cannula was used. Cardiopulmonary bypass (CPB) was carried out under normothermic conditions. Antegrade intermittent warm blood cardioplegia was used as a method of myocardial protection.

A total number of 222 coronary grafts were performed (mean 2.9 grafts/patient); distal anastomoses were performed through a left ITA–IEA Y-graft (n=104), left ITA–right ITA (n=72), left ITA–RGEA (n=22) and 24 with segments of saphenous vein. The Y-graft construction was performed prior to cannulation for CPB. After constructing the Y graft using RGEA, IEA or right ITA anastomosed to the side of the left ITA, this latter was sutured to the left anterior descending (LAD) coronary artery, while the other branch of the Y was used to graft vessels in the circumflex and often in the right coronary territories. The IEA was used in obtuse marginal or diagonal branch with an expected high run-off. Vein grafts were applied as needed to vessels different from the ones grafted with the arterial conduits.

Diltiazem hydrochloride infusion, 4 mg/h beginning after the aortic cross-clamp was taken off, was given for the first 24 h to avoid spasm of the arterial conduits.

2.3. Study protocol
Intraoperative blood flow measurements were performed before and after completing the distal anastomoses using an ultrasound Doppler device based on the transit-time principle. Also, after prophylactic lidocaine was given (2 mg/kg i.v.), we measured the effect that temporary interruption of flow in one branch of the Y graft caused on blood flow in the other branch. Then, blood flow through the proximal ITA was again measured during interruption of either the distal ITA or the other graft using a soft rubber bull-dog clamp. During flow measurements, mean arterial blood pressure was maintained between 70 and 80 mmHg. The purpose of doing this was to evaluate the flow reserve of pedicled ITA and potential for creation of a steal phenomenon should one side of the Y graft be anastomosed to an high-runoff coronary bed.

The following variables were monitored: heart rate (beats/min), electrocardiogram (leads V5 and II), mean systemic arterial pressure (MAP, mmHg), mean graft systolic and diastolic flow (ml/min), pulsatility index (PI=[systolic flow-diastolic flow]/mean flow), diastolic graft backflow expressed as percent insufficiency (volume of backward flow/volume or forward flow), vascular resistance (R=MAP/mean volume flow[=mmHg/ml per min]).

2.4. Blood flow measurements
Flow measurements were achieved intraoperatively by using a transit-time Doppler flow probes (Cardiomed Flowmeter CM 4000 Medi-Stim, Oslo, Norway). The principle is based on the assumption that the time needed for an acoustic wave to pass through a flowing fluid is slightly longer when passing upstream rather than downstream.

Two ultrasound crystals are placed on one side of the instrument's probe, while a reflecting surface is placed on the other side. The probe is then applied around the blood vessel. When an ultrasonic burst is generated by the first crystal, it passes through the blood mass, is reflected and received by the second crystal, and the time (t₁) measured. The transmitter/receiver function is then reversed and the burst transit time (t₂) recorded again. This reversal function eliminates the need for information about the vessel diameter or ultrasonic burst angle of incidence with the blood flow. As the ultrasound crystals are wider than the vessel's lumen, the acoustic waves will cover every flow vector in the vessel, thus making the time difference

proportional to the true blood flow.

Although there are reports about the system's accuracy [10], we chose to validate this method by comparing instrument's readings with direct blood collection in a graduated cylinder.

2.5. Statistical analysis
Analysis of variance was used to compare values at the three measurement points (proximal and distal ITA, other graft). Data were recorded as a mean±standard deviation; a P-value of 0.05 was considered significant.

	3. Results

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion Appendix A Conference discussion References

 
There was no operative or hospital mortality. There were no intraoperative myocardial infarctions. Twenty-two patients, three of whom were on preoperative ß-blocking agents, required temporary inotropic support (dopamine, 3–5 /kg per min). All patients were weaned from ventilatory support within 24 h of surgery. In one patient a low-flow situation due to intramural hematoma was detected (mean flow=12 ml/min, elevated vascular resistance (>100 ), elevated PI (134), diastolic backflow >50%), requiring surgical reconstruction. Complications included one case of abdominal wall hematoma and one case of superficial sternal wound infection. The postoperative course was uneventful in all other cases. All patients were discharged on an antiplatelet agent.

Follow-up was by clinical examination and exercise stress test (Bruce protocol) at 3 months and by telephone interview at 12 months postoperatively. Thirty-two patients underwent angiographic study after 12 months, showing a patency of anastomoses in all cases. There were no cases of recurrent angina. No patients showed inducible ischemia in the anterior, septal or lateral wall of the left ventricle. Six asymptomatic patients showed borderline electrocardiographic changes in the posterior and inferior wall during exercise stress test.

The ITA has a free flow in the range of 134–192 ml/min (mean value 166 ml/min) and will adjust itself to the demands of the arterial bed it is supplying. Nominal flow values of the ITA–LAD graft after CABG is approximately 45±8 ml/min and it will therefore have capacity to supply another territory as well as sufficient flow reserve for higher demands. The occlusion of the other branch of the Y graft did not significantly affect antegrade ITA flow directly to the LAD coronary artery determined by intraoperative blood flow measurements and vice versa. Coronary flow remains mainly diastolic with a minimal or limited systolic myocardial supply.

Table 1 summarizes the blood flow measurements taken in the arterial grafts. When the distal ITA was occluded, blood flow in the other branch did not increase and the same happened to the distal ITA when the other conduit was occluded.

	4. Discussion

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion Appendix A Conference discussion References

Since the composite arterial Y graft may be considered an ‘extended’ ITA to a LAD graft, we decided to perform this approach routinely. However, a main challenge could be related to the hypoperfusion phenomenon due to occlusion and/or failure of the proximal ITA.

In this series the left ITA free flow increased 58 ml/min when the Y graft was performed. The free potential mean flow through the proximal ITA was 166 ml/min. After release of aortic cross-clamping a reduction of flow on pedicled ITA occurred; thus vascular resistances of composite graft may be lower than those of single conduits. Therefore, vascular resistance and flow occurring by the native coronary circulation produces a significant reduction of proximal ITA flow.

Our results demonstrated that:

1. Proximal ITA has the potential to provide sufficient blood flow to revascularize the anterior and lateral wall of the left ventricle, avoiding the hypoperfusion phenomenon, both in basal conditions and after a 3-month adjustment period also during an exercise stress test
   
2. The composite Y arterial graft provides good early and mid-term results
   
3. The ITA–LAD graft has a mean flow of 45±8 ml/min
   
4. Transit-time flow measurement is an easy and efficient method to evaluate the graft flow and quality of the anastomoses
   

	Footnotes

 
Presented at the 13th Annual Meeting of the European Association for Cardio-thoracic Surgery, Glasgow, Scotland, UK, September 5–8, 1999.

	Appendix A Conference discussion

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion Appendix A Conference discussion References

 
Dr A. Royse (Victoria, Australia): I think what your data shows is what we have always intuitively suspected. The flow of the conduit is primarily dependent on the resistance of the vascular bed to which it is going and the degree of competitive flow from the native coronary circulation that may or may not be occurring. Your measurements were done after the release of the aortic cross-clamp, so there was an element of competitive flow. I would be very interested in the future if you were to examine your same data set and tell us more about the degree of coronary stenosis affecting these vessels that you grafted.

Dr Speziale: This is the backgound of this study, because we use the epigastric artery since the histological patterns of the epigastric are similar to those of the internal thoracic artery. Probably in the perioperative period, we have some stress-like surgical trauma or harvesting technique, or cardioplegia, and anything else. We studied these patients at 12-month follow-up, we have not presented the results in this study because it represents a small group of follow-up patients; however, we have studied some patients with the echo Doppler at 12-month follow-up, and we find that the flow through the ITA is higher than the perioperative period. Probably endothelial factors such as nitric oxide and the adjustment period allow an increase of flow through the vessel. So the runoff is not so easy to calculate in the perioperative period in the patient.

Dr P. Sergeant (Leuven, Belgium): Dr Speziale, part of your inferences are built on exercise testing. Did you use a standardized format of exercise testing concerning heart rate, work load and peak work load? Did you try other forms of viability or ischemic analysis or visualization techniques?

Dr Speziale: Yes, we are considering myocardial scintigraphy for evaluating the possibility of inducible ischemia, and we are now studying patients with more than three vessels with a Y- or T-graft anastomosis. Exercise stress test is standardized with the Bruce procedure.

	References

Top Abstract 1. Introduction 2. Materials and methods 3. Results 4. Discussion Appendix A Conference discussion References

 

1. Loop F.D., Lytle B.W., Cosgrove D.M., Stewart R.W., Goormastic M., Williams G.W., Golding L.A., Gill C.C., Taylor P.C., Sheldon W.C. Influence of the internal mammary artery graft on 10 years survival and other cardiac events. N Engl J Med 1986;314:1-6.[Abstract]
2. Pick A.W., Orszulak T.A., Anderson B.J., Shaff H.V. Single versus bilateral internal mammary artery grafts: 10 years outcome analysis. Ann Thorac Surg 1997;64:599-605.[Abstract/Free Full Text]
3. Calafiore A., Di Gianmarco G., Luciani N., Maddestra N., Di Nardo E., Angelini R. Composite arterial conduits for a wider arterial myocardial revascularization. Ann Thorac Surg 1994;58:185-190.[Abstract]
4. Weinschelbaum E., Gabe E., Macchia A., Smimmo R., Suarez L. Total myocardial revascularization with arterial conduits. J Thorac Cardiovasc Surg 1997;114:911-916.[Abstract/Free Full Text]
5. Tector A., Kress D.C., Schmahl T.M., Amundsen S.T-g.r. raft: a new method of coronary arterial revascularization. J Cardiovasc Surg 1994;35:19-23.[Medline]
6. Suma H., Wanibuchi Y., Terada Y., Fukuda S., Takayama T., Furuta S. The right gastroepiploic artery graft. Clinical and angiographic midterm results in 200 patients. J Thorac Cardiovasc Surg 1993;105:615-623.[Abstract]
7. Perrault L.P., Carrier M., Hebert W., Cartier R., Leclerc Y., Pelletier C. Early experience with the inferior epigastric artery in coronary artery bypass grafting. J Thorac Cardiovasc Surg 1993;106:928-930.[Abstract]
8. Acar C., Jebara V.A., Portoghese M., Beyssen B., Pagny J.Y., Grare P., Chachques J.C., Fabiani J.N., Deloche A., Guermonprez J.L. Revival of the radial artery for coronary artery bypass grafting. Ann Thorac Surg 1992;54:652-660.[Abstract]
9. Calafiore A.M., Di Giammarco G., Teodori G., D'Annunzio E., Vitolla G., Fino C., Maddestra N. Radial artery and inferior epigastric artery in composite grafts: improved midterm angiographic results. Ann Thorac Surg 1995;60:517-524.[Abstract/Free Full Text]
10. Matre K., Birkeland S., Hessevik I., Segadal L. Comparison of transit time and Doppler ultrasound methods for measurements of flow in aortocoronary bypass graft during cardiac surgery. Thorac Cardiovasc Surg 1994;42(3):170-174.[Medline]
11. van Son J.A.M., Smedts F., Vincent J.G., van Lier H.J.J., Kubat K. Comparative anatomic study of various arterial conduits for myocardial revascularization. J Thorac Cardiovasc Surg 1990;99:703-707.[Abstract]
12. Schwartz D.S., Factor S.M., Shwartz J.D., Petrosian E., Blitz A., McLoughlin D., Tellis V., Frame R., Brodman R.F. Histological evaluation of the inferior epigastric artery in patient with known atherosclerosis. Eur J Cardio-thorac Surg 1992;6:438-441.[Abstract]
13. Buche M., Dion R. Current status of the inferior epigastric artery. Semin Thorac Cardiovasc Surg 1996;8:10-14.[Medline]
14. Kawasuji M., Tedoriya T., Takemura H., Sakakibara N., Taki J., Watanabe Y. Flow of arterial grafts for coronary artery bypass grafting. Ann Thorac Surg 1993;56:957-962.[Abstract]

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