Reversed Intercostal Arterial Flow in Coarctation of the Aorta Intraoperative Assessment with the Doppler Ultrasonic Velocity Detector Robert W. Barnes, M.D., Edward A. Rittenhouse, M.D., Chamnahn Kongtahwom, M.D., Donald B. Doty, M.D., Nicholas P. Rossi, M.D., and Johann L. Ehrenhaft, M.D. ABSTRACT The collateral circulation around a coarctation of the aorta was assessed in II patients during operative repair of the lesion. A sterile directional Doppler velocity detector probe was applied directly to the intercostal arteries and flow direction was determined. Prior to the repair, flow in the first two intercostals was normal in direction. Flow was reversed in direction (toward the aorta) in from two to six intercostal arteries arising distad to the coarctation. Following repair, flow was in the normal direction in all intercostal arteries. There was no correlation between the number of intercostals with reversed flow and either the pathological severity of the coarctation or the arm-ankle pressure ,gradient determined preoperatively. This study confirms the simplicity and utility of the Doppler ultrasonic velocity detector for intraoperative assessment of collateral circulation in coarctation of the aorta.
oarctation of the thoracic aorta is associated with the presence of collateral circulation which often develops early in infancy [4]. Although the anatomical distribution of such collaterals has been the subject of extensive study [2], there is little information concerning the dynamics of circulation around the coarctation. In the past that information was unavailable, partly due to lack of adequate instrumentation. The recent development of the Doppler ultrasonic velocity detector allows rapid and safe determination of directional blood flow velocity. Mozersky and associates [6] have pointed out the usefulness of that instrument in the operative assessment of blood flow velocity. The present study describes application of the directional Doppler ultrasonic velocity detector for the intraoperative assessment of collateral circulation in patients undergoing repair of coarctation of the aorta.
C
Materials and Methods CLINICAL MATERIAL
Eleven patients undergoing operative resection of coarctation of the aorta were selected for study. There were 7 male and 4 female patients with From the Peripheral Vascular Laboratories, Division of Thoracic and Cardiovascular Surgery, University of Iowa Hospitals and Veterans Administration Hospital, Iowa City, Iowa. Accepted for publication Aug. 27, 1974. Address reprint ,requests to Dr. Barnes, Director, Peripheral Vascular Laboratory, Surgical Service, Veterans Administration Hospital, Iowa City, Iowa 52240.
VoL. 19, NO.1, JANUARY, 1975
-
27
-------_._.~.~._~-~---------
BARNES ET AL.
FIG. 1. Technique of placement of the Doppler probe Oller an intercostal artery to determine directional flow velocity.
an average age of 11 years (range, 7 to 25 years). Diagnosis was established by clinical evaluation and confirmed by cardiac catheterization in all patients. Operation was performed through a left posterolateral thoracotomy with primary anastomosis performed after resection of the coarcted segment. INSTRUMENTATION
The directional Doppler probe* contains a piezoelectric crystal which emits a 10 megahertz beam of ultrasound that is transmitted into the tissues through an acoustical gel coupling medium. Sound reflected from moving blood cells of a vessel in the path of the beam is shifted in frequency by an amount proportional to the velocity of blood flow. The backscattered sound is received by a second crystal, and the frequency shift is detected and amplified by the instrument. Utilizing the phase-shift circuit described by McLeod [5J, the direction of blood flow velocity can be determined with the capacity to separately record forward and reverse flow velocities. STUDY METHOD
Preoperatively, the systolic pressure at rest was determined in the right arm and right ankle using the Doppler velocity detector. All patients were studied during the operative procedure. A sterile Doppler probe was applied to each intercostal artery above and below the coarctation using a sterile water-soluble acoustical gel (Fig. 1). The probe was held at 45 degrees to obtain the maximum flow velocity signal. All measurements were taken over the intercostal arteries close to their origin from the aorta. The analog *Parks Electronics Lahoratory. Beaverton, Ore.
28
THE ANNALS OF THORACIC SURGERY
97005.
Collateral Flow Assessment
In
Aortic Coarctation
FIG. 2. Intercostal arterial collateral flow dynamics in coarctation of the aorta. Normal flow in first (and occasionally second) intercostal artery is the result of its origin from the subclavian artery.
output of the directional Doppler velocity detector was recorded on a multichannel recorder. * Flow direction was determined in each intercostal artery before and after resection of the coarctation. The diameter of the lumen of the coarcted segment was measured immediately after resection with calibrated DeBakey vascular dilators. An attempt was made to correlate the number of intercostal arteries having reversed flow distad to the coarctation with the arm-ankle pressure gradient determined preoperatively and the luminal diameter of the coarctation.
Results Intraoperative assessment of intercostal flow velocity was feasible in all patients. Flow in the first two intercostal arteries was normal in direction (away from the aorta) in each instance. These vessels were branches of the costocervical trunk arising from the left subclavian artery proximal to the coarctation. In those intercostals which arose from the aorta distad to the coarctation, flow was reversed (toward the aorta) in from two to six arteries (Figs. 2, 3). There was no correlation between the number of intercostals with reverse flow and the arm-ankle pressure gradient or luminal diameter of the coarctation (Figs. 4, 5).
Comment Extensive collateral circulation develops around a coarctation of the aorta with the dominant contribution emanating from the named branches "'Model 7754A, Hewlett Packard Co., Waltham Div., 175 Wyman St., Waltham, Mass.
02154.
VOL. 19, NO.1, JANUARY, 1975
29
BARNES ET AL.
Pre-repair
1st Intercostal
Post-repair
rVJ\
2nd Intercoslol
o-~
0-
5th
4th
Intercostal
Intercostal
0-
VvV 6th
1\ f\ O----Ji'i-J '-J "'"
5th
Intercostal
O-~
Intercostal
--Jl
0-
1-1 see-s
~
f--l sec-l
FIG. 3. Intraoperative directional flow velocity in intercostal arteries before and after resection of coarctation. Reversed flow (below zero base line) is noted in fifth intercostal artery before repair.
of the subclavian arteries [2]. The intercostal arteries are important anastomotic bridges because of their communication with the aorta below the coarctation and the internal mammary, musculophrenic, superior epigastric, anterior spinal, lateral thoracic, and descending branch of the transverse cervical arteries. Intercostal arteries thus become greatly enlarged and tortuous even to the point of causing rib erosion [3J. Although the importance of the intercostal arteries as collateral channels has long been recognized, little information exists concerning the dynamics of circulation through these vessels. Pattern of blood flow through the individual arteries at different levels has not been determined. An extensive collateral network can develop early in life around the aortic coarctation. Matthew and associates [4] demonstrated the presence of FIG. 4. Relationship between arm-ankle pressure gradient and number of intercostal arteries with reversed flow.
100 ~
ill ......
~r 80
ete Ole -'-
...c:::_
60
'q:C:::
.!
''b
40
:IE"
~~
•
20
2
3
4
5
Number of Intercostals with Reversed Flow
30
THE ANNALS OF THORACIC SURGERY
6
Collateral Flow Assessment tn Aortic Coarctation
FIG. 5. Relationship between luminal diameter of the coarctation and number of intercostal arteries with reoersed flow.
2 3 4 Number of Intercostols with Reversed Flow
5
6
collateral circulation within the first few weeks of life in infants with coarctation of the aorta. Although those authors found a correlation between hypertension and a good collateral circulation, many of their patients had well-developed collaterals in the absence of severe coarctation or hypertension. Such findings agree with the results of our study, in which the number of intercostals carrying blood in a reverse direction was not related to the diameter of the coarctation or to the pressure gradient across the lesion. This lack of correlation is not unexpected since the size of the intercostal arteries and the volume flow through these vessels may be quite variable in different patients. Furthermore, the relative contribution of various sources of collateral blood supply to the distal aorta may vary in different patients. The first two intercostal arteries are believed to contribute little to the collateral circulation around the coarctation. Edwards and associates [2] pointed out that the first two intercostals do not communicate with the aorta posteriorly but anastomose with the superior intercostal artery, which is usually a branch of the costocervical trunk or subclavian artery. Our studies provide hemodynamic evidence to substantiate that point in that flow was in the normal direction in these arteries in all patients. Very few attempts have been made to assess collateral flow in human coarctation of the aorta. Schenk, McDonald, and Andersen [7] applied the electromagnetic flowmeter to evaluate circulatory dynamics intraoperatively. Flow across the narrowed segment was measured at 45 to 52% of the estimated cardiac output. Following repair, flow decreased in 2 of their patients and increased in 1. Intercostal artery flow was measured at the highest left intercostal in 2 patients. Flow was toward the aorta in both (750 and 58 ml per minute, respectively) prior to repair. Following repair, flow could not be recorded in the intercostal artery in the 1 patient studied. Our study indicated that flow in intercostal arteries following repair of the coarctation became normal in direction in all vessels distad to the repair.
VOL.
19, NO.1, JANUARY, 1975
31
BARNES ET AL. Determination of intercostal flow with the electromagnetic flowmeter is difficult due to the fragility of the vessels and the necessity for dissection and placement of a periarterial probe. In contrast, directional flow velocity can be determined by placement of a Doppler probe directly over the artery without danger of injury. Benchimol, Baldi, and Desser [1] applied the detector to the scapular and intercostal area in 1 patient with coarctation of the aorta. Although their instrument could not detect flow direction, they did note an increased flow during diastole. However, our study indicates that intercostal arterial flow is primarily unidirectional in the intercostal arteries carrying reversed flow prior to operation, as is true of collateral vessels around an obstruction in arteriosclerotic peripheral vascular disease. The Doppler flow velocity probe can be gas-sterilized and made readily available in the operating room [6]. The directional Doppler velocity detector has the capability of determining flow direction, which is particularly applicable in conditions in which flow might be reversed. This study demonstrates the ease with which the directional Doppler detector can be applied to the study of patients with coarctation of the aorta. This instrument may prove to be a useful modality to further evaluate the preoperative, intraoperative, and postoperative hemodynamics of collateral circulation in patients with coarctation of the aorta.
References
J., and Desser, K. B. Measurement of phasic scapular and intercostal collateral arterial blood velocity in coarctation of the aorta. Chest 63: 1015, 1973. Edwards, J. E., Clagett, O. T., Russell, L. D., and Christiansen, N. A. The collateral circulation in coarctation of the aorta. Mayo Clin Proc 23:333, 1948. Gooding, C. A., Glickman, M. G., and Suydam, M. J. Fate of rib notching after correction of aortic coarctation. Am ] Roentgenol Radium Ther Nucl Med 106:21, 1969. Matthew, R., Simon, G., and Joseph, M. Collateral circulation in coarctation of aorta in infancy and childhood. Arch Dis Child 47:960, 1972. McLeod, F. D., Jr. A Directional Doppler Flowmeter. In B. Jacobson (Ed), Digest of the Seventh International Conference on Medical and Biological Engineering) Stockholm, Aug. 14-19, 1967. Stockholm: Royal Academy of Engineering Sciences, 1967. P 213. Mozersky, D. j., Sumner, D. S.. Barnes, R. W., and Strandness, D. E. Intraoperative use of a sterile ultrasonic flow probe. Surg Gynecol Obstet 136:279,1973. Schenk, W. G., McDonald, K. E., and Andersen, M. N. Blood flow measurements in human coarctation. .1 T'horac Cardiovasc Surg 50:26, 1965.
1. Benchimol, A., Baldi,
2. 3. 4. 5.
6. 7.
32
THE ANNALS OF THORACIC SURGERY
oarctation of the thoracic aorta is associated with the presence of collateral circulation which often develops early in infancy [4]. Although the anatomical distribution of such collaterals has been the subject of extensive study [2], there is little information concerning the dynamics of circulation around the coarctation. In the past that information was unavailable, partly due to lack of adequate instrumentation. The recent development of the Doppler ultrasonic velocity detector allows rapid and safe determination of directional blood flow velocity. Mozersky and associates [6] have pointed out the usefulness of that instrument in the operative assessment of blood flow velocity. The present study describes application of the directional Doppler ultrasonic velocity detector for the intraoperative assessment of collateral circulation in patients undergoing repair of coarctation of the aorta.
C
Materials and Methods CLINICAL MATERIAL
Eleven patients undergoing operative resection of coarctation of the aorta were selected for study. There were 7 male and 4 female patients with From the Peripheral Vascular Laboratories, Division of Thoracic and Cardiovascular Surgery, University of Iowa Hospitals and Veterans Administration Hospital, Iowa City, Iowa. Accepted for publication Aug. 27, 1974. Address reprint ,requests to Dr. Barnes, Director, Peripheral Vascular Laboratory, Surgical Service, Veterans Administration Hospital, Iowa City, Iowa 52240.
VoL. 19, NO.1, JANUARY, 1975
-
27
-------_._.~.~._~-~---------
BARNES ET AL.
FIG. 1. Technique of placement of the Doppler probe Oller an intercostal artery to determine directional flow velocity.
an average age of 11 years (range, 7 to 25 years). Diagnosis was established by clinical evaluation and confirmed by cardiac catheterization in all patients. Operation was performed through a left posterolateral thoracotomy with primary anastomosis performed after resection of the coarcted segment. INSTRUMENTATION
The directional Doppler probe* contains a piezoelectric crystal which emits a 10 megahertz beam of ultrasound that is transmitted into the tissues through an acoustical gel coupling medium. Sound reflected from moving blood cells of a vessel in the path of the beam is shifted in frequency by an amount proportional to the velocity of blood flow. The backscattered sound is received by a second crystal, and the frequency shift is detected and amplified by the instrument. Utilizing the phase-shift circuit described by McLeod [5J, the direction of blood flow velocity can be determined with the capacity to separately record forward and reverse flow velocities. STUDY METHOD
Preoperatively, the systolic pressure at rest was determined in the right arm and right ankle using the Doppler velocity detector. All patients were studied during the operative procedure. A sterile Doppler probe was applied to each intercostal artery above and below the coarctation using a sterile water-soluble acoustical gel (Fig. 1). The probe was held at 45 degrees to obtain the maximum flow velocity signal. All measurements were taken over the intercostal arteries close to their origin from the aorta. The analog *Parks Electronics Lahoratory. Beaverton, Ore.
28
THE ANNALS OF THORACIC SURGERY
97005.
Collateral Flow Assessment
In
Aortic Coarctation
FIG. 2. Intercostal arterial collateral flow dynamics in coarctation of the aorta. Normal flow in first (and occasionally second) intercostal artery is the result of its origin from the subclavian artery.
output of the directional Doppler velocity detector was recorded on a multichannel recorder. * Flow direction was determined in each intercostal artery before and after resection of the coarctation. The diameter of the lumen of the coarcted segment was measured immediately after resection with calibrated DeBakey vascular dilators. An attempt was made to correlate the number of intercostal arteries having reversed flow distad to the coarctation with the arm-ankle pressure gradient determined preoperatively and the luminal diameter of the coarctation.
Results Intraoperative assessment of intercostal flow velocity was feasible in all patients. Flow in the first two intercostal arteries was normal in direction (away from the aorta) in each instance. These vessels were branches of the costocervical trunk arising from the left subclavian artery proximal to the coarctation. In those intercostals which arose from the aorta distad to the coarctation, flow was reversed (toward the aorta) in from two to six arteries (Figs. 2, 3). There was no correlation between the number of intercostals with reverse flow and the arm-ankle pressure gradient or luminal diameter of the coarctation (Figs. 4, 5).
Comment Extensive collateral circulation develops around a coarctation of the aorta with the dominant contribution emanating from the named branches "'Model 7754A, Hewlett Packard Co., Waltham Div., 175 Wyman St., Waltham, Mass.
02154.
VOL. 19, NO.1, JANUARY, 1975
29
BARNES ET AL.
Pre-repair
1st Intercostal
Post-repair
rVJ\
2nd Intercoslol
o-~
0-
5th
4th
Intercostal
Intercostal
0-
VvV 6th
1\ f\ O----Ji'i-J '-J "'"
5th
Intercostal
O-~
Intercostal
--Jl
0-
1-1 see-s
~
f--l sec-l
FIG. 3. Intraoperative directional flow velocity in intercostal arteries before and after resection of coarctation. Reversed flow (below zero base line) is noted in fifth intercostal artery before repair.
of the subclavian arteries [2]. The intercostal arteries are important anastomotic bridges because of their communication with the aorta below the coarctation and the internal mammary, musculophrenic, superior epigastric, anterior spinal, lateral thoracic, and descending branch of the transverse cervical arteries. Intercostal arteries thus become greatly enlarged and tortuous even to the point of causing rib erosion [3J. Although the importance of the intercostal arteries as collateral channels has long been recognized, little information exists concerning the dynamics of circulation through these vessels. Pattern of blood flow through the individual arteries at different levels has not been determined. An extensive collateral network can develop early in life around the aortic coarctation. Matthew and associates [4] demonstrated the presence of FIG. 4. Relationship between arm-ankle pressure gradient and number of intercostal arteries with reversed flow.
100 ~
ill ......
~r 80
ete Ole -'-
...c:::_
60
'q:C:::
.!
''b
40
:IE"
~~
•
20
2
3
4
5
Number of Intercostals with Reversed Flow
30
THE ANNALS OF THORACIC SURGERY
6
Collateral Flow Assessment tn Aortic Coarctation
FIG. 5. Relationship between luminal diameter of the coarctation and number of intercostal arteries with reoersed flow.
2 3 4 Number of Intercostols with Reversed Flow
5
6
collateral circulation within the first few weeks of life in infants with coarctation of the aorta. Although those authors found a correlation between hypertension and a good collateral circulation, many of their patients had well-developed collaterals in the absence of severe coarctation or hypertension. Such findings agree with the results of our study, in which the number of intercostals carrying blood in a reverse direction was not related to the diameter of the coarctation or to the pressure gradient across the lesion. This lack of correlation is not unexpected since the size of the intercostal arteries and the volume flow through these vessels may be quite variable in different patients. Furthermore, the relative contribution of various sources of collateral blood supply to the distal aorta may vary in different patients. The first two intercostal arteries are believed to contribute little to the collateral circulation around the coarctation. Edwards and associates [2] pointed out that the first two intercostals do not communicate with the aorta posteriorly but anastomose with the superior intercostal artery, which is usually a branch of the costocervical trunk or subclavian artery. Our studies provide hemodynamic evidence to substantiate that point in that flow was in the normal direction in these arteries in all patients. Very few attempts have been made to assess collateral flow in human coarctation of the aorta. Schenk, McDonald, and Andersen [7] applied the electromagnetic flowmeter to evaluate circulatory dynamics intraoperatively. Flow across the narrowed segment was measured at 45 to 52% of the estimated cardiac output. Following repair, flow decreased in 2 of their patients and increased in 1. Intercostal artery flow was measured at the highest left intercostal in 2 patients. Flow was toward the aorta in both (750 and 58 ml per minute, respectively) prior to repair. Following repair, flow could not be recorded in the intercostal artery in the 1 patient studied. Our study indicated that flow in intercostal arteries following repair of the coarctation became normal in direction in all vessels distad to the repair.
VOL.
19, NO.1, JANUARY, 1975
31
BARNES ET AL. Determination of intercostal flow with the electromagnetic flowmeter is difficult due to the fragility of the vessels and the necessity for dissection and placement of a periarterial probe. In contrast, directional flow velocity can be determined by placement of a Doppler probe directly over the artery without danger of injury. Benchimol, Baldi, and Desser [1] applied the detector to the scapular and intercostal area in 1 patient with coarctation of the aorta. Although their instrument could not detect flow direction, they did note an increased flow during diastole. However, our study indicates that intercostal arterial flow is primarily unidirectional in the intercostal arteries carrying reversed flow prior to operation, as is true of collateral vessels around an obstruction in arteriosclerotic peripheral vascular disease. The Doppler flow velocity probe can be gas-sterilized and made readily available in the operating room [6]. The directional Doppler velocity detector has the capability of determining flow direction, which is particularly applicable in conditions in which flow might be reversed. This study demonstrates the ease with which the directional Doppler detector can be applied to the study of patients with coarctation of the aorta. This instrument may prove to be a useful modality to further evaluate the preoperative, intraoperative, and postoperative hemodynamics of collateral circulation in patients with coarctation of the aorta.
References
J., and Desser, K. B. Measurement of phasic scapular and intercostal collateral arterial blood velocity in coarctation of the aorta. Chest 63: 1015, 1973. Edwards, J. E., Clagett, O. T., Russell, L. D., and Christiansen, N. A. The collateral circulation in coarctation of the aorta. Mayo Clin Proc 23:333, 1948. Gooding, C. A., Glickman, M. G., and Suydam, M. J. Fate of rib notching after correction of aortic coarctation. Am ] Roentgenol Radium Ther Nucl Med 106:21, 1969. Matthew, R., Simon, G., and Joseph, M. Collateral circulation in coarctation of aorta in infancy and childhood. Arch Dis Child 47:960, 1972. McLeod, F. D., Jr. A Directional Doppler Flowmeter. In B. Jacobson (Ed), Digest of the Seventh International Conference on Medical and Biological Engineering) Stockholm, Aug. 14-19, 1967. Stockholm: Royal Academy of Engineering Sciences, 1967. P 213. Mozersky, D. j., Sumner, D. S.. Barnes, R. W., and Strandness, D. E. Intraoperative use of a sterile ultrasonic flow probe. Surg Gynecol Obstet 136:279,1973. Schenk, W. G., McDonald, K. E., and Andersen, M. N. Blood flow measurements in human coarctation. .1 T'horac Cardiovasc Surg 50:26, 1965.
1. Benchimol, A., Baldi,
2. 3. 4. 5.
6. 7.
32
THE ANNALS OF THORACIC SURGERY
