- Email: [email protected]
Balloon Test Occlusion in the Setting of Vessel Sacrifice: Procedural Refinements and Adjunct Assessment Measures
Perspectives Commentary on: Enhanced, Rapid Occlusion of Carotid and Vertebral Arteries Using the AMPLATZER Vascular Plug II Device: The Duke Cerebrovascular Center Experience in 8 Patients with 22 AMPLATZER Vascular Plug II Devices by Mihlon et al. World Neurosurg 2013 http://dx.doi.org/10.1016/j.wneu.2013.07.084
William J. Mack, M.D. Assistant Professor of Neurological Surgery Department of Neurological Surgery University of Southern California Keck School of Medicine
Balloon Test Occlusion in the Setting of Vessel Sacrifice: Procedural Refinements and Adjunct Assessment Measures Vivek Mehta and William J. Mack
T
he ability to efficiently occlude the carotid artery with an endovascular approach represents a technical advancement in the treatment of select cerebrovascular and intracranial pathologies. The Amplatzer Vascular Plug II is an occlusion device that can decrease time and limit cost associated with these procedures. Clinical indications, patient selection criteria, and anatomic considerations are of significant importance in the planning of vessel sacrifice. Here we review the modern techniques of balloon test occlusion (BTO) with a focus on adjunct techniques to enhance the sensitivity and specificity of this test. After establishing vascular access for a BTO, it is widely accepted that activated clotting time should be maintained at roughly two to three times baseline with initial heparin bolus and infusion (5). This is particularly important when single lumen balloons without dedicated channels for distal saline or heparin administration are used in the internal carotid artery (ICA). As occlusive balloons impede anterograde flow through the target vessel, a risk of thrombus formation secondary to distal stagnation is of concern. Dual lumen balloons that allow for saline or heparin infusion while the balloon is inflated help address this issue. Once the balloon is inflated, direct and indirect assessment measures are used to ascertain the suitability of collateral flow and functional reserve. The first and most basic test is a clinical neurological examination every 2e5 minutes while the balloon is inflated. Any decline in speech, motor strength, sensation, level of consciousness, or cranial nerve function signifies a failed trial. In this situation, the balloon should be deflated immediately (5). Complete occlusion of the ICA for a minimum of 15e30 minutes is standard. A patient
Key words AMPLATZER - AVF - Embolization - Fistula - Internal carotid artery - Vertebral artery -
Abbreviations and Acronyms BTO: Balloon test occlusion CBF: Cerebral blood flow CT: Computerized tomography ICA: Internal carotid artery SPECT: Single-photon emission computed tomography
WORLD NEUROSURGERY - [-]: ---, MONTH 2013
who tolerates 30 minutes of occlusion without clinical or physiologic evidence of impaired perfusion is likely to tolerate permanent vessel sacrifice (5). The incidence of subsequent infarction after tolerating a BTO with clinical assessment ranges from 2%e13% (6). Relatively high false-positive rates have compelled many operators to use adjunct testing. Hypotensive challenge in the setting of BTO is purported to increase the test sensitivity by identifying patients with insufficient collateral supply. This test is performed by reducing systolic blood pressure by approximately 30% for 10e20 minutes and assessing for changes in neurological examination (8). It is believed that a subset of patients who exhibit no functional deficits in the setting of temporary vessel occlusion may decline clinically when blood pressure is decreased, diminishing further the patients’ functional reserve. Cerebral blood flow (CBF) has been evaluated in the setting of BTO. Before the refinement of objective CBF monitoring techniques, arterial stump pressure (intraluminal arterial pressure distal to the occlusion site) was used as an indirect assessment. However, stump pressure quantification is now considered less reliable than more sophisticated, direct measures of blood flow and functional reserve (4). The electroencephalogram is commonly used to detect changes related to diminished CBF. However, no large scale studies have been performed to assess its predictive efficacy as a stand-alone measure in the setting of temporary vessel occlusion (2). A variety of imaging techniques have been used to predict ischemic events after carotid sacrifice by detecting CBF or asymmetric
Department of Neurological Surgery, University of Southern California Keck School of Medicine, Los Angeles, California, USA To whom correspondence should be addressed: William J. Mack, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2013). http://dx.doi.org/10.1016/j.wneu.2013.08.036
www.WORLDNEUROSURGERY.org
1
PERSPECTIVES
perfusion. Of these, transcranial Doppler measurements are the least invasive. In a small study, venous phase angiography was reported to accurately predict tolerance of permanent ICA occlusion. The venous saturation of each cerebral hemisphere is compared after carotid occlusion. A failed test is defined by a lack of synchronous venous filling after 20e30 minutes of vessel occlusion (10). Single-photon emission computed tomography (SPECT), positron emission tomography, and xenon computerized tomography (CT) are advanced imaging modalities that can more precisely detect CBF, and have increased the predictive value of BTO. Each technique has its own advantages and disadvantages. SPECT imaging involves the evaluation of symmetric distribution of a radioisotope that is injected after the test occlusion. Advantages of this technique include its simplicity, measurement accuracy, and high sensitivity/specificity (7). In addition, the balloon catheter can be removed from the carotid artery before transporting the patient to the scanner. A particular disadvantage of SPECT is that bilateral symmetric reductions in CBF due to well-developed collateral circulation through the anterior or posterior communicating arteries could result in symmetric radiographic appearance despite an overall perfusion deficit, leading to a false-negative result. Transcranial near infrared spectroscopy can detect bilateral symmetrical decreases in CBF to identify false-negative SPECT studies (3). Similarly, positron emission tomography involves CBF measurement after injection of radionuclide tracers, but has been studied less extensively than SPECT imaging (1). Xenon CT provides reliable CBF assessment and is believed to improve the sensitivity and
REFERENCES 1. Brunberg JA, Frey KA, Horton JA, Deveikis JP, Ross DA, Koeppe RA: [15O]H2O positron emission tomography determination of cerebral blood flow during balloon test occlusion of the internal carotid artery. AJNR Am J Neuroradiol 15:725-732, 1994. 2. Herkes GK, Morgan M, Grinnell V, Sorby W, Wong J, Rowe D, Stroud J: EEG monitoring during angiographic balloon test carotid occlusion: experience in sixteen cases. Clin Exp Neurol 30:98-103, 1993. 3. Kaminogo M, Ochi M, Onizuka M, Takahata H, Shibata S: An additional monitoring of regional cerebral oxygen saturation to HMPAO SPECT study during balloon test occlusion. Stroke 30: 407-413, 1999. 4. Kurata A, Miyasaka Y, Tanaka C, Ohmomo T, Yada K, Kan S: Stump pressure as a guide to the safety of permanent occlusion of the internal
2
www.SCIENCEDIRECT.com
specificity of BTO. However, the technique requires the patient to undergo angiography in the CT scanner (9). Inhalation of xenon, which acts as a neurodepressant, limits the utility of a clinical neurological examination. Adjunct radiographic techniques allow for patient stratification according to CBF measurement. In conjunction with a real-time neurological examination, these modalities allow for increased testing sensitivity and a more comprehensive assessment of functional reserve. Mihlon et al. present a very nice case series describing their experience with the Aplatzer Vascular Plug II. Their article focuses on the technical aspects of vessel sacrifice and the utility of a new device. This is the first substantial case series using the device for a diverse group of vascular lesions in the head and neck. The investigators present background and rationale for the report and device use. The cases presented are both interesting and informative. They provide a picture of the device so that the reader understands the occlusion mechanism. One potential advantage of this device might be cost. As coils are expensive, the use of multiple bare platinum or fibered coils to occlude a carotid or vertebral artery harbors a high cost. As medicine moves in a direction that favors comparative cost effectiveness, this could be the most appealing reason for use of this device in these demanding patients. Vessel sacrifice will remain a mainstay in the treatment of some of the most challenging intracranial pathologies. As techniques evolve, the importance of proper patient selection and the utility of BTO will remain critical.
carotid artery. Acta Neurochirurgica 138:549-554, 1996. 5. Lazzaro H, Willing S: Balloon test occlusion of the internal carotid artery. Sem Interv Radiol 20:59-67, 2003. 6. Linskey ME, Jungreis CA, Yonas H, Hirsch WL Jr, Sekhar LN, Horton JA, Janosky JE: Stroke risk after abrupt internal carotid artery sacrifice: accuracy of preoperative assessment with balloon test occlusion and stable Xenon-enhanced CT. AJNR 5:829-843, 1994. 7. Ryu YH, Chung TS, Lee JD, Kim DI, Suh JH, Park CY, Lee WS, Lee KS: HMPAO SPECT to assess neurologic deficits during balloon test occlusion. J Nucl Med 37:551-554, 1996. 8. Standard SC, Ahuja A, Guterman LR, Chavis TD, Gibbons KJ, Barth AP, Hopkins LN: Balloon test occlusion of the internal carotid artery with hypotensive challenge. Am J Neuroradiol 16: 1453-1458, 1995.
9. Steed DL, Webster MW, DeVries EJ, Jungreis CA, Horton JA, Sehkar L, Yonas H: Clinical observations on the effect of carotid artery occlusion on cerebral blood flow mapped by xenon computed tomography and its correlation with carotid artery back pressure. J Vasc Surg 11:38-44, 1990. 10. van Rooij WJ, Sluzewski M, Metz NH, Nijssen PC, Wijnalda D, Rinkel GJ, Tulleken CA: Carotid balloon occlusion for large and giant aneurysms: evaluation of a new test occlusion protocol. Neurosurgery 47:116-123, 2000.
Citation: World Neurosurg. (2013). http://dx.doi.org/10.1016/j.wneu.2013.08.036 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2013 Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2013.08.036
William J. Mack, M.D. Assistant Professor of Neurological Surgery Department of Neurological Surgery University of Southern California Keck School of Medicine
Balloon Test Occlusion in the Setting of Vessel Sacrifice: Procedural Refinements and Adjunct Assessment Measures Vivek Mehta and William J. Mack
T
he ability to efficiently occlude the carotid artery with an endovascular approach represents a technical advancement in the treatment of select cerebrovascular and intracranial pathologies. The Amplatzer Vascular Plug II is an occlusion device that can decrease time and limit cost associated with these procedures. Clinical indications, patient selection criteria, and anatomic considerations are of significant importance in the planning of vessel sacrifice. Here we review the modern techniques of balloon test occlusion (BTO) with a focus on adjunct techniques to enhance the sensitivity and specificity of this test. After establishing vascular access for a BTO, it is widely accepted that activated clotting time should be maintained at roughly two to three times baseline with initial heparin bolus and infusion (5). This is particularly important when single lumen balloons without dedicated channels for distal saline or heparin administration are used in the internal carotid artery (ICA). As occlusive balloons impede anterograde flow through the target vessel, a risk of thrombus formation secondary to distal stagnation is of concern. Dual lumen balloons that allow for saline or heparin infusion while the balloon is inflated help address this issue. Once the balloon is inflated, direct and indirect assessment measures are used to ascertain the suitability of collateral flow and functional reserve. The first and most basic test is a clinical neurological examination every 2e5 minutes while the balloon is inflated. Any decline in speech, motor strength, sensation, level of consciousness, or cranial nerve function signifies a failed trial. In this situation, the balloon should be deflated immediately (5). Complete occlusion of the ICA for a minimum of 15e30 minutes is standard. A patient
Key words AMPLATZER - AVF - Embolization - Fistula - Internal carotid artery - Vertebral artery -
Abbreviations and Acronyms BTO: Balloon test occlusion CBF: Cerebral blood flow CT: Computerized tomography ICA: Internal carotid artery SPECT: Single-photon emission computed tomography
WORLD NEUROSURGERY - [-]: ---, MONTH 2013
who tolerates 30 minutes of occlusion without clinical or physiologic evidence of impaired perfusion is likely to tolerate permanent vessel sacrifice (5). The incidence of subsequent infarction after tolerating a BTO with clinical assessment ranges from 2%e13% (6). Relatively high false-positive rates have compelled many operators to use adjunct testing. Hypotensive challenge in the setting of BTO is purported to increase the test sensitivity by identifying patients with insufficient collateral supply. This test is performed by reducing systolic blood pressure by approximately 30% for 10e20 minutes and assessing for changes in neurological examination (8). It is believed that a subset of patients who exhibit no functional deficits in the setting of temporary vessel occlusion may decline clinically when blood pressure is decreased, diminishing further the patients’ functional reserve. Cerebral blood flow (CBF) has been evaluated in the setting of BTO. Before the refinement of objective CBF monitoring techniques, arterial stump pressure (intraluminal arterial pressure distal to the occlusion site) was used as an indirect assessment. However, stump pressure quantification is now considered less reliable than more sophisticated, direct measures of blood flow and functional reserve (4). The electroencephalogram is commonly used to detect changes related to diminished CBF. However, no large scale studies have been performed to assess its predictive efficacy as a stand-alone measure in the setting of temporary vessel occlusion (2). A variety of imaging techniques have been used to predict ischemic events after carotid sacrifice by detecting CBF or asymmetric
Department of Neurological Surgery, University of Southern California Keck School of Medicine, Los Angeles, California, USA To whom correspondence should be addressed: William J. Mack, M.D. [E-mail: [email protected]] Citation: World Neurosurg. (2013). http://dx.doi.org/10.1016/j.wneu.2013.08.036
www.WORLDNEUROSURGERY.org
1
PERSPECTIVES
perfusion. Of these, transcranial Doppler measurements are the least invasive. In a small study, venous phase angiography was reported to accurately predict tolerance of permanent ICA occlusion. The venous saturation of each cerebral hemisphere is compared after carotid occlusion. A failed test is defined by a lack of synchronous venous filling after 20e30 minutes of vessel occlusion (10). Single-photon emission computed tomography (SPECT), positron emission tomography, and xenon computerized tomography (CT) are advanced imaging modalities that can more precisely detect CBF, and have increased the predictive value of BTO. Each technique has its own advantages and disadvantages. SPECT imaging involves the evaluation of symmetric distribution of a radioisotope that is injected after the test occlusion. Advantages of this technique include its simplicity, measurement accuracy, and high sensitivity/specificity (7). In addition, the balloon catheter can be removed from the carotid artery before transporting the patient to the scanner. A particular disadvantage of SPECT is that bilateral symmetric reductions in CBF due to well-developed collateral circulation through the anterior or posterior communicating arteries could result in symmetric radiographic appearance despite an overall perfusion deficit, leading to a false-negative result. Transcranial near infrared spectroscopy can detect bilateral symmetrical decreases in CBF to identify false-negative SPECT studies (3). Similarly, positron emission tomography involves CBF measurement after injection of radionuclide tracers, but has been studied less extensively than SPECT imaging (1). Xenon CT provides reliable CBF assessment and is believed to improve the sensitivity and
REFERENCES 1. Brunberg JA, Frey KA, Horton JA, Deveikis JP, Ross DA, Koeppe RA: [15O]H2O positron emission tomography determination of cerebral blood flow during balloon test occlusion of the internal carotid artery. AJNR Am J Neuroradiol 15:725-732, 1994. 2. Herkes GK, Morgan M, Grinnell V, Sorby W, Wong J, Rowe D, Stroud J: EEG monitoring during angiographic balloon test carotid occlusion: experience in sixteen cases. Clin Exp Neurol 30:98-103, 1993. 3. Kaminogo M, Ochi M, Onizuka M, Takahata H, Shibata S: An additional monitoring of regional cerebral oxygen saturation to HMPAO SPECT study during balloon test occlusion. Stroke 30: 407-413, 1999. 4. Kurata A, Miyasaka Y, Tanaka C, Ohmomo T, Yada K, Kan S: Stump pressure as a guide to the safety of permanent occlusion of the internal
2
www.SCIENCEDIRECT.com
specificity of BTO. However, the technique requires the patient to undergo angiography in the CT scanner (9). Inhalation of xenon, which acts as a neurodepressant, limits the utility of a clinical neurological examination. Adjunct radiographic techniques allow for patient stratification according to CBF measurement. In conjunction with a real-time neurological examination, these modalities allow for increased testing sensitivity and a more comprehensive assessment of functional reserve. Mihlon et al. present a very nice case series describing their experience with the Aplatzer Vascular Plug II. Their article focuses on the technical aspects of vessel sacrifice and the utility of a new device. This is the first substantial case series using the device for a diverse group of vascular lesions in the head and neck. The investigators present background and rationale for the report and device use. The cases presented are both interesting and informative. They provide a picture of the device so that the reader understands the occlusion mechanism. One potential advantage of this device might be cost. As coils are expensive, the use of multiple bare platinum or fibered coils to occlude a carotid or vertebral artery harbors a high cost. As medicine moves in a direction that favors comparative cost effectiveness, this could be the most appealing reason for use of this device in these demanding patients. Vessel sacrifice will remain a mainstay in the treatment of some of the most challenging intracranial pathologies. As techniques evolve, the importance of proper patient selection and the utility of BTO will remain critical.
carotid artery. Acta Neurochirurgica 138:549-554, 1996. 5. Lazzaro H, Willing S: Balloon test occlusion of the internal carotid artery. Sem Interv Radiol 20:59-67, 2003. 6. Linskey ME, Jungreis CA, Yonas H, Hirsch WL Jr, Sekhar LN, Horton JA, Janosky JE: Stroke risk after abrupt internal carotid artery sacrifice: accuracy of preoperative assessment with balloon test occlusion and stable Xenon-enhanced CT. AJNR 5:829-843, 1994. 7. Ryu YH, Chung TS, Lee JD, Kim DI, Suh JH, Park CY, Lee WS, Lee KS: HMPAO SPECT to assess neurologic deficits during balloon test occlusion. J Nucl Med 37:551-554, 1996. 8. Standard SC, Ahuja A, Guterman LR, Chavis TD, Gibbons KJ, Barth AP, Hopkins LN: Balloon test occlusion of the internal carotid artery with hypotensive challenge. Am J Neuroradiol 16: 1453-1458, 1995.
9. Steed DL, Webster MW, DeVries EJ, Jungreis CA, Horton JA, Sehkar L, Yonas H: Clinical observations on the effect of carotid artery occlusion on cerebral blood flow mapped by xenon computed tomography and its correlation with carotid artery back pressure. J Vasc Surg 11:38-44, 1990. 10. van Rooij WJ, Sluzewski M, Metz NH, Nijssen PC, Wijnalda D, Rinkel GJ, Tulleken CA: Carotid balloon occlusion for large and giant aneurysms: evaluation of a new test occlusion protocol. Neurosurgery 47:116-123, 2000.
Citation: World Neurosurg. (2013). http://dx.doi.org/10.1016/j.wneu.2013.08.036 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2013 Elsevier Inc. All rights reserved.
WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2013.08.036