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Ann Thorac Surg 1998;66:1236-1241
© 1998 The Society of Thoracic Surgeons

Original articles: cardiovascular

Minimally invasive mammary artery Doppler flow velocity evaluation in minimally invasive coronary operations

Antonio M. Calafiore, MDa, Sabina Gallina, MDa, Angela Iacò, MDa, Giovanni Teodori, MDa, Teresa Iovino, MDa, Gabriele Di Giammarco, MDa, Valerio Mazzei, MDa, Giuseppe Vitolla, MDa

a Department of Cardiac Surgery, University "G. D’Annunzio" of Chieti, Chieti, Italy

Accepted for publication April 8, 1998.

Address reprint requests to Dr Calafiore, Department of Cardiac Surgery, "G. D’Annunzio" University, "San Camillo de’ Lellis" Hospital, Via C. Forlanini 50, 66100 Chieti, Italy
e-mail: (calafiore{at}unich.it)


   Abstract
Top
 Abstract
Introduction
 Material and methods
 Results
 Comment
 References
 
Background. Left internal mammary artery Doppler flow velocity assessment during the Azoulay maneuver (patient’s legs are passively lifted up and actively maintained by the patient) can increase the information on the anastomosis quality after left internal mammary artery to left anterior descending coronary artery grafting after the left anterior, small thoracotomy operation.

Methods. One hundred patients had an early postoperative angiography and a Doppler flow velocity assessment at rest and during the Azoulay maneuver. Peak and mean systolic velocities, peak and mean diastolic velocities, and peak and mean diastolic to systolic velocity ratios were recorded in all patients.

Results. In 95 patients with no restrictive conduit or anastomosis, peak and mean diastolic to systolic velocity ratios increased during the Azoulay maneuver; all but 1 patient showed at least one ratio equal to or greater than 1. In 4 patients with restrictive conduit or anastomosis, peak and mean diastolic to systolic velocity ratios were always less than 1 during the Azoulay maneuver. In the patient with an occluded conduit these ratios were less than 0.6.

Conclusions. Peak and mean diastolic to systolic velocity ratios less than 1 during the Azoulay maneuver are suggestive of conduit or anastomosis malfunction. If we limit the angiographic controls to these patients, it is very likely that a pathologic anastomosis or conduit will not be missed.


   Introduction
Top
 Abstract
 Introduction
Material and methods
 Results
 Comment
 References
 
Left anterior descending (LAD) coronary artery revascularization using the left internal mammary artery (LIMA) through a left anterior small thoracotomy (LAST operation) has recently gained popularity [1–4] and is successfully used, in selected cases, for LAD grafting. Since the beginning of our experience [5] the LIMA was not harvested totally, but only for the length necessary to reach the LAD. Therefore the first portion of the LIMA is not far from the chest wall and is easily detectable with a Doppler flow velocity probe.

At rest, the Doppler probe can detect the increase of the diastolic flow velocity component when the LIMA is grafted to the LAD, a territory perfused mainly during diastole; however, this information is not complete. We know in fact that the LIMA and the LAD are connected, but we do not know whether during stress conditions the anastomosis is restrictive or not. Pharmacologic stress tests (using adenosine, dipyridamole, or dobutamine) need some organization, are not easily done, and cannot be repeated often. For this reason, one of us (S.G.) proposed to assess the LIMA Doppler flow velocity pattern during the Azoulay maneuver [6], which is easy to do and repeatable.

This study has two purposes. The first one is to evaluate the effectiveness of the Doppler flow velocity assessment at rest and during the Azoulay maneuver in a consecutive group of patients who had LIMA to LAD through a LAST on a beating heart and in whom a postoperative control angiography showed a widely patent graft (group A). A small series of patients with angiographically determined anastomotic or conduit malfunctions were considered as a control group (group B). The ungrafted LIMA flow velocity pattern was assessed in a group of volunteers to know the normal behavior in the ungrafted LIMA.

The second purpose is to find whether any information drawn from the Doppler flow velocity assessment can predict whether the anastomosis is both patent and not restrictive to limit the necessity of postoperative angiographies.


   Material and methods
Top
 Abstract
 Introduction
 Material and methods
Results
 Comment
 References
 
From January 1997 to August 1997, 100 of 116 patients who underwent the LAST operation in the same period had an LIMA Doppler flow evaluation at rest and during the Azoulay maneuver in the immediate postoperative period; all of them had angiography before being discharged from the hospital. The remaining 16 patients were excluded as they refused to have postoperative angiography; as both Doppler flow evaluation and clinical status were satisfying, we did not insist further. In Table 1 preoperative data are shown. Surgical technique was previously reported [5]. The quality of the anastomosis or of the conduit was graded according to Fitzgibbon and colleagues [7]: (1) grade A, excellent graft with unimpaired runoff; (2) grade B, stenosis reducing caliber of proximal or distal anastomoses or trunk to less than 50% of the grafted coronary artery. Overall graft B grade was determined by the lowest of the three specific site grades; and (3) grade O, occlusion.


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  		Table 1. Preoperative Data

 
The LIMA doppler flow velocity was evaluated using the ATL Apogee Cx 200 (Advanced Technology Laboratories, Bothell, WA) Doppler echocardiograph and a 7.5-MHz probe. The first intercostal space was used most frequently for the evaluation, and the second intercostal space was used less frequently. Left internal mammary artery flow velocities were assessed at rest and, with the probe still in place, during the Azoulay maneuver.

The Azoulay maneuver was designed many decades ago to improve the auscultation of the heart’s murmurs in valvular disease. It consists of two steps; first both legs of the patient are lifted up by an assistant, and second the patient is required to actively hold this position for a few seconds. Acute hypervolemia follows as blood from both legs is suddenly emptied into the upper body circulation. As a consequence the heart rate and cardiac output transiently increase [6]; this causes an increase of blood flow to both the muscular circulation (systolic phase of the LIMA flow pattern) and to the coronary circulation (diastolic phase of the LIMA flow pattern).

To evaluate the modification of hemodynamic parameters in 10 patients, heart rate, systolic and diastolic arterial pressure, and cardiac output were recorded at rest and during the Azoulay maneuver, performed 4 hours after intensive care unit admission. Every patient had direct cannulation of the radial artery and heart rate was continuously recorded. Cardiac output was obtained with the thermodilution technique through a Swan-Ganz catheter.

Peak systolic velocity, peak diastolic velocity, mean systolic velocity, and mean diastolic velocity were recorded, both at rest and during the Azoulay maneuver, as well as peak diastolic to systolic velocity ratios (PDSVR) and mean diastolic to systolic velocity ratios (MDSVR). Heart rate and systemic pressure were also recorded. Effects of the Azoulay maneuver lasted about 60 seconds. The values obtained were correlated with the angiographic findings.

Patients were then discharged and followed up at the outpatient clinic after 1, 2, 4, and 6 months. At that time, an LIMA Doppler flow evaluation was performed again. All the patients in group B were given another angiography at a mean interval of 185 ± 26 days from the first one. Every patient had a stress test without medical treatment, 1 and 6 months after the operation.

Results are expressed as mean ± standard deviation unless otherwise indicated. Statistical analysis comparing two groups was performed with unpaired two-tailed t testing. One-way analysis of variance was used to compare the groups at rest and during the Azoulay maneuver. A probability value less than 0.05 was considered significant.


   Results
Top
 Abstract
 Introduction
 Material and methods
 Results
Comment
 References
 
Table 2 reports hemodynamic changes during the Azoulay maneuver. All the variables showed an increase that was statistically significant. For practical reasons, only the first step (the passive one) was accomplished. Control angiographies were performed 2 ± 2 days (range, 1 to 7 days) after the operation. All conduits but one were patent (patency rate 99%). Distal anastomoses or conduits were considered grade A in 95 cases (group A). In 4 patients (group B) the angiographic results were defined as grade B, showing a pathologic aspect at LIMA level near the anastomosis (2 patients) or at the anastomosis (2 patients).


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  		Table 2. Hemodynamic Changes at Rest and During the Azoulay Maneuver in 10 Patients

 
Control group
In 12 volunteers, a Doppler flow velocity evaluation was performed at rest and during the Azoulay maneuver. These data are shown in Table 3. The heart rate increased from 76 ± 8 to 92 ± 6 beats/min (p < 0.0005), systolic arterial pressure rose from 117 ± 26 to 138 ± 31 mm Hg (p < 0.05), and diastolic arterial pressure rose from 71 ± 13 to 85 ± 22 mm Hg (p < 0.05). Systolic components of the flow velocity pattern, at rest and during the Azoulay maneuver, were significantly higher than diastolic, as a peak and as a mean. However, the increase of systolic velocities during the Azoulay maneuver was never statistically significant, whereas diastolic components showed a statistically significant increase, even if not relevant as absolute value. As a consequence, both PDSVR and MDSVR increased during the Azoulay maneuver, the latter value significantly. However, no peak or mean velocity ratios had, in this group, a value higher than 0.6. This pattern was also present in the patient in whom the conduit was occluded (Fig 1).


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  		Table 3. LIMA Doppler Flow Velocity Assessment (cm/sec) in the Control Group (n = 12)

 


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  		Fig 1. Doppler flow velocity evaluation in a patient with an occluded conduit, at rest (A) and during the Azoulay maneuver (B).

 
Patients with grade A anastomoses (group A, n = 95)
Doppler flow evaluation at rest and during the Azoulay maneuver is shown in Table 4. The heart rate increased from 75 ± 13 to 94 ± 14 beats/min (p < 0.0005), as well as systemic pressure (systolic 128 ± 33 versus 140 ± 38 mm Hg, p < 0.025; diastolic 78 ± 22 versus 87 ± 28 mm Hg, p < 0.025).


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  		Table 4. LIMA Doppler Flow Velocity Assessment (cm/sec) in Patients (n = 95) With Grade A Anastomosis

 
At rest, both peak and mean diastolic velocities were often, but not always, higher than corresponding systolic velocities. As a consequence, basal PDSVR and MDSVR were often, but not always, greater than 1. More specifically, PDSVR was equal to or greater than 1 in 76 of 95 patients and MDSVR in 83 of 95 patients.

During the Azoulay maneuver, both systolic and diastolic peak and mean velocities increased (Fig 2), but only the increase of the diastolic component reached statistical significance. Peak and mean diastolic velocities were statistically higher than the corresponding systolic velocities. Consequently, PDSVR and MDSVR increased further during the Azoulay maneuver (Table 4), often, but not always, reaching 1. As at rest, PDSVR was equal to or more than 1 in 88 of 95 patients and MDSVR in 94 of 95 patients. Only in a single instance were all the ratios (at rest and during the Azoulay maneuver) less than 1. In every patient in whom a basal ratio was equal to or more than 1, there was a further increase during the Azoulay maneuver.



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  		Fig 2. Doppler flow velocity evaluation in a patient with normal early angiographic control (A), at rest (B) and during the Azoulay maneuver (C). The diastolic velocities, greater than the systolic ones at rest, increase further during the Azoulay maneuver. Peak and mean diastolic to systolic velocity ratios are more than 1 in every patient.

 
During the follow-up, all patients in this group had a negative stress test without medical treatment, and the myocardial scintigraphy, when done, showed normal perfusion in the LAD territory.

When the Doppler flow velocity assessment showed at least one ratio equal to or more than 1, the test was defined as "positive": this happened in 94 of 95 patients in group A.

Patients with grade B anastomosis (group B, n = 4)
In this small group of patients the angiography showed anastomotic stenosis (in 2) or conduit anomalies (in 2). Doppler flow velocity evaluation at rest and during the Azoulay maneuver is shown in Table 5. Heart rate increased from 75 ± 7 to 89 ± 9 beats/min (p < 0.05), as well as systemic pressure (systolic 111 ± 23 versus 149 ± 28 mm Hg, p < 0.05; diastolic 75 ± 9 versus 89 ± 9 mm Hg, p < 0.05).


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  		Table 5. LIMA Doppler Flow Velocity Assessment (cm/s) in Patients Who had Anastomotic Stenosis or Conduit Malfunction (n = 4)a

 
At rest, both peak and mean diastolic velocities were lower than corresponding systolic velocities; however, the difference was not statistically significant. As a consequence, basal PDSVR and MDSVR were lower than 1.

During the Azoulay maneuver, the increase in diastolic velocities was poor, whereas a normal increase in systolic velocities was present, although, as in the basal values, it was not significant. These ratios did not change and remained less than 1 (Fig 3).



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  		Fig 3. Doppler flow velocity evaluation in a patient with severe left internal mammary artery kinking (A). Diastolic velocities, lower than the systolic ones at rest (B), do not increase during the Azoulay maneuver (C). Peak and mean diastolic to systolic velocity ratios are less than 1 in all patients.

 
When the Doppler flow velocity assessment showed no ratio equal to or greater than 1, the test was defined as "negative": this happened in all patients in group B (4 of 4).

As the patients in this group were asymptomatic, we waited for a further angiographic control. From 1 to 7 months after the operation all the patients had a negative stress test, and the Doppler flow velocity assessment, at rest and during the Azoulay maneuver, showed a normalization of the flow pattern (ie, the test became positive). Further angiograms, obtained in all patients, showed a reversal of the anastomotic or conduit malfunction stenosis (Fig 4). Consequently, the Doppler flow velocity assessment at rest and after the Azoulay maneuver reversed to the same pattern as in group A. The angiographic perfect patency rate rose to 99%.



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  		Fig 4. Same patient as in Figure 3 four months after the first angiography. The left internal mammary artery shape became normal (A). Doppler flow velocity evaluation at rest was similar to the one shown in Figure 3 (B); however, during the Azoulay maneuver (C), peak diastolic velocity increased from 0.14 to 0.28 m/sec and mean diastolic velocity increased from 0.10 to 0.21 m/sec.

 
If we compare the corresponding values of groups A and B, we don’t find a statistical difference in either the systolic or basal diastolic values. On the contrary, in group A, peak and mean diastolic velocities were significantly higher during the Azoulay maneuver (p < 0.0125 and p < 0.01, respectively), as well as all the diastolic to systolic ratios, both basal (p < 0.0025) and during the Azoulay maneuver (p < 0.0005).


   Comment
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
References
 
Left internal mammary artery to LAD anastomosis via a LAST operation is a recently introduced surgical technique for LAD revascularization [1–5]. Quality control of the anastomosis is a crucial aspect of this operation, especially for the surgical teams that start with this procedure. Ideally, in the beginning every patient should have a postoperative angiography to check every technical aspect, but we are aware that this is not possible. We investigated the possibility of using the Doppler flow velocity evaluation to check the quality of the anastomosis [5]. However, flow velocity assessment at rest gives incomplete information, as the increase of a diastolic flow does not avoid the possibility of an anastomotic malfunction. Pharmacologic stress tests, using adenosine, dipyridamole, or dobutamine, are not easy to do or repeat. For these reasons we chose to apply the LIMA flow assessment during the Azoulay maneuver [6].

The acute hypervolemia, and consequently the increase of cardiac output and heart rate, causes a sudden increase in the flow velocities, and the amount of the increase gives a perfect idea of the functional aspect of the anastomosis. At rest patients with normal anastomotic or conduit anatomy have both peak and mean diastolic velocities higher than the systolic ones, as well as the corresponding ratios. During the Azoulay maneuver, both peak and mean velocities increase, but the diastolic increase is higher than the systolic one, and the corresponding ratios usually are 1 or greater.

To predict the quality of the anastomosis, comparing postoperative angiographies and Doppler flow velocity evaluation, at rest and during the Azoulay maneuver, we suggest the following guidelines.

  1. If a patient has a basal PDSVR or MDSVR equal to or more than 1, the anastomosis is nonrestrictive (grade A); this happened in every patient who showed this pattern.
  2. If a patient with both basal ratios less than 1 shows, during the Azoulay maneuver, an increase of PDSVR or MDSVR to 1 or more, the anastomosis is not restrictive (grade A); this happened in every patient who showed this pattern.
  3. If all a patient’s ratios are less than 1, but at least one is more than 0.60, the anastomosis is restrictive (grade B), but not occluded. In the 5 patients who showed this pattern, only in a single instance was the anastomosis not restrictive (grade A).
  4. If every ratio is not greater than 0.60, the anastomosis or the conduit can be occluded. In the single patient who showed this pattern, the conduit was occluded at the angiography.

If control angiographies are performed only in patients with a negative Doppler test, it is very likely that no patient with conduit or anastomosis malfunction will be missed, even if in 16.7% of the cases (1 of 6 in our experience) a patient with a normal anatomy will be studied. On the other hand, we will avoid angiographies of patients with nonrestrictive anastomosis. The postoperative stress test, if negative, will confirm the quality of the revascularization.

In conclusion, the Doppler flow velocity evaluation at rest and after the Azoulay maneuver is a reliable technique to follow up patients who undergo the LAST operation. The necessity of postoperative angiographies will be reduced, costs will be contained, and the patient’s comfort will increase.


   References
Top
 Abstract
 Introduction
 Material and methods
 Results
 Comment
 References
 

  1. Benetti F.J., Ballester C. Use of thoracoscope and a minimal thoracotomy, in mammary-coronary by-pass to left anterior descending artery, without extracorporeal circulation: Experience 2 cases. J Cardiovasc Surg 1995;10:529-536.
  2. Acuff T.E., Landreneau R.J., Griffith B.P., Mack M.J. Minimally invasive coronary artery bypass grafting. Ann Thorac Surg 1996;61:135-137.[Abstract/Free Full Text]
  3. Robinson M.C., Gross D.R., Zeman W., Stedje-Larsen E. Minimally invasive coronary artery bypass grafting: A new method using an anterior mediastinotomy. J Card Surg 1995;10:529-536.[Medline]
  4. Subramanian V., Stelzer P. Clinical experience with minimally invasive coronary artery bypass grafting (CABG). Eur J Thorac Cardiovasc Surg 1996;10:1058-1063.
  5. Calafiore A.M., Di Giammarco G., Teodori G., et al. Left anterior descending coronary artery grafting via left anterior small thoracotomy without cardiopulmonary bypass. Ann Thorac Surg 1996;61:1658-1665.[Abstract/Free Full Text]
  6. Calafiore A.M., Teodori G., Di Giammarco G., et al. Minimally invasive coronary artery bypass grafting on a beating heart. Ann Thorac Surg 1997;63:S72-S75.
  7. Fitzgibbon G.M., Kafka H.P., Leach A.J. Coronary bypass graft fate and patient outcome: angiographic follow-up of 5,065 grafts related to survival and reoperation in 1,388 patients during 25 years. J Am Coll Cardiol 1996;28:616-626.[Abstract]



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