Br. J. Surg. 1991, Vol. 78, September, 1130-1 133
D. C. Berridge, A. C. Perkins", M. Frier*, R. J. Lonsdale, K. C. Ballantyne, M. L. Wastie*, G. S. Makin and B. R . Hopkinson Departments of Vascular Surgery and *Medical Physics, University Hospital, Queen's Medical Centre, Nottingham. UK Correspondence to: Mr D. C. Berridge, Middlesbrough General Hospital, Ayresome Green Lane, Middlesbrough, Cleveland TS5 5A2, U K
Detection and characterization of arterial thromboses using a platelet-specif ic monoclonal antibody (P256 Fab') Arteriography does not reliably distinguish between acute and chronic arterial occlusions. Seventeen patients with acute lower limb ischaemia were investigated by arteriography and by imaging with a plateletspec$c monoclonal antibody (P256 Fab'); 20 M B q "'In-labelled P256 Fah' was administered intravenously and patients were imaged at intervals of hetween 20 min and 24 h. Thirteen patients were subsequently treated with intra-arterial thrombolysis. In six the images showed ,foci of increased uptake qf ' ' I In-labelled P256 Fab' and the corresponding arterial segment was recanalized. Patency to 30 days was maintained in ,four cases. Seven patients had negative scans, only four ofwhom achieved lysis, and two of these suflered early rethrombosis. The remaining four patients were excluded from thrombolysis by the arteriographic appearances. In-labelled P2.56 Fab' imaging can identij" sites of acute arterial thrombosis and may have clinical applications in the management of peripheral vascular disease. Further studies are required to test whether the technique has a role to play in patient selection f o r thrombolysis.
Peripheral arterial thrombolysis is being increasingly used in the treatment of acute and subacute lower limb ischaemia with favourable results' - 3 . Its use in the treatment of chronic arterial occlusion has been less encouraging4. Arteriography cannot distinguish between recent and chronic occlusion and at present this aspect of patient selection depends primarily on clinical history. Despite a policy of restricting lysis to patients with a history of less than 30 days, in a number of patients there is no radiological evidence of lysis. It seems likely that in these patients the arterial occlusion is chronic and the clinical history is unreliable. Platelet imaging using 'indium oxine-labelled platelets has been previously shown to be capable of demonstrating arterial, intracardiac' and venous thrombi6. It has also been of use in the investigation of platelet deposition on arterial prosthetic grafts'. However, this technique requires considerable time and technical skill for cell separation and labelling. A further problem is that, owing to incomplete cell separation, there is often a substantial contamination of the platelet plug with leucocytes which, when labelled, produces a relatively high background uptake. This high background uptake reduces image contrast and necessitates long imaging times to obtain satisfactory results. It is therefore not ideally suited to widespread use as a means of detecting acute arterial thrombosis. The present study was carried out using a recently developed immunoglobulin G I (IgG, ) mouse monoclonal antibody fragment specific for the glycoprotein IIb/IIIa receptor on platelets (P256 Fab')8. This agent was assessed for its ability to detect arterial thrombus quickly and reliably. In addition, the extent of uptake was compared with the subsequent success of thrombolytic therapy.
''
"'
studied. All gave informed consent to participate in the study, which was approved by the Hospital Ethical Committee and the Administration of Radioactive Substances Advisory Committee. One hundred micrograms of P256 Fab' (Amersham International plc. Amersham, U K ) was labelled with 20 MBq "'indium chloride (INSIP. Amersham International plc). Before injection, 5 ml venous blood was obtained for subsequent anti-mouse antibody studies. The serum was separated and stored at -4O'C until analysed. The P256 antibody preparation was given in a volume of 10ml by slow intravenous injection. A further venous blood sample was taken after 20 min to perform estimates of platelet-associated radioactivity. Images were recorded for 300 s per view, using a large field of view IGE 400AC ;.-camera fitted with a medium energy collimator (300 keV maximum) and dual energy windows centred on both photopeaks of '"In (173, 247 keV). Images were obtained after 20min, 4-5 h. and 24 h. Immediately after the last imaging period, the patients underwent arteriography and subsequent intra-arterial thrombolysis if this was still considered appropriate at this stage. The P256 images were not used in the selection of patients for treatment. The protocol for jntra-arterial thrombolysis has previously been reported'. The results of the imaging technique and its comparison with arteriography and the outcome of treatment were assessed at the end of the trial. A further venous sample was obtained from seven patients 3 weeks after the study to assess any anti-mouse antibody response. All samples were assayed using an immunoenzyme procedure (ETI-Hamak. Sorin Biomedica, Salvggia, Italy).
Results
Seventeen patients with a history of sudden development or deterioration of lower limb ischaemia within the preceding 30 days and who were considered suitable for thrombolysis on clinical grounds were
Of the 17 patients studied, 13 subsequently underwent peripheral arterial thrombolysis (four were excluded from thrombolysis because of the appearances at subsequent arteriography). In the group undergoing thrombolysis, there were six patients in whom positive P256 Fab' antibody images were obtained and seven in whom negative images were obtained. Positive uptake was visualized as localized regions of high uptake corresponding to an occluded arterial segment on arteriography (Figure I ) . This was seen as early as 5 h after injection with, in some cases, improved definition after 24 h.
1130
~-1323/91/09113&04
Patients and methods
0 1991 Butterworth-Heinemann Ltd
Imaging of arterial thromboses: D. C. Berridge et al.
Table 1 Details of scan result, treatment and outcome in 17 palienrs Patient no.
Duration of history (days)
Scan result
Undergoing thrombolysis Positive 1 14 Positive 2 14 Positive 3 I Positive 4 14 Positive 5 5 Positive 6 9 I 28 Negative 8 21 Negative 9 28 Negative 10 10 Negative 11 16 Negative Negative 12 3 13 21 Negative Excluded from thrombolysis 14 28 Positive Positive 15 4 16 17
Figure 1 a Image obtained after 5 h demonstrates discrete upiake foci in the proximal and distal left superficial femoral artery. b, c Subsequent arteriography confirms an occlusion in this artery, and suggests that the occlusion (thrombus) continues into the popliteal artery. d Thrombolysis readily Iyses the thrombus but only to the extent shown on the P256 Fab' image. Two major collaterals perfuse the lower limb and have remained patent after 3 months
Br. J. Surg., Vol. 78, No. 9, September 1991
2 14
Negative Negative
Initial lysis
Outcome
Yes Yes Yes Yes Yes Yes No Yes Yes Yes No Yes No
Rethrombosed Successful Successful Successful Successful Ret hrom bosed Failed Rethrombosed Successful Rethrombosed Failed Successful Failed
Treated with angioplasty Iliac aneurysms (aortobifemoral graft) Two ipsilateral occlusions Two ipsilateral occlusions
O n commencing thrombolysis in the six patients with positive images, there was rapid lysis of thrombus in the arterial segment corresponding to the site of high uptake. In four patients this resulted in restoration of arterial patency which was maintained at 30 days. In the remaining two patients severe arterial disease below the thrombosed segment was revealed. In neither case was this amenable to angioplasty or bypass and in both cases the lack of run-off resulted in early rethrombosis (Table 2 ). The results of thrombolysis in the seven patients with negative images were less good' In Only two patients was thrombobsis s ~ X e s s f uwith l arterial Patency maintained at 30 days. In three patients there was no significant thrombus lYSiS at all, and in the final two patients lysis occurred but was incomplete and rapid rethrombosis occurred.
1131
Imaging of arterial thromboses: D. C. Berridge et al.
Figure 2 a Image obtained afier 5 h reveals two,foci of increased uptake
in the lower right superficial femoral artery. b Pelvic views show increased uptake in the right and left common iliac arteries and right femoral arteries. Subsequent ultrasonography confirmed bilateral iliac aneurysms. Arterial reconstruction was performed and the emboli were extracted
Four patients were excluded from thrombolysis. Two had both iliac and superficial femoral artery occlusions on the same side, one of which was almost certainly chronic, and therefore it was felt that the likelihood of a successful outcome from thrombolysis was significantly reduced; surgical reconstruction was carried out instead. The other two patients were particularly interesting. In the first, bilateral regions of high
1132
Figure 3 a Image after 5 I7 den7orrstrati17g two h i g h l ~positire ~ foci separated by a less distinct,focus. b Subsequerit arteriographj rewals that these foci iiwe at sites of 90 and 75 per cent stenoses respec'tirelj.
uptake were seen in the pelvis together with an additional focus of high uptake corresponding to the tibioperoneal trunk (Figure 2 ) . Ultrasonography revealed the presence of clinically occult bilateral iliac aneurysms and it seems likely that distal embolization from these was responsible for the distal occlusion. An aortobifemoral graft with ligation of the iliac aneurysms was performed with a successful outcome. The final patient had two areas of high uptake in the superficial femoral artery (Figure 3 ) ; arteriography revealed these to correspond to 75
Br. J. Surg.. Vol. 78, No. 9, September 1991
Imaging of arterial thromboses: D. C. Berridge et al.
and 90 per cent stenoses respectively. These were dilated by balloon angioplasty. Assay of the blood samples taken 20 min after injection showed approximately 80 per cent of the blood radioactivity to be associated with circulating platelets". Assay of the blood from seven patients taken 3 weeks after the study showed no evidence ofproduction of human anti-mouse antibody. A longer term follow-up is being undertaken to determine whether a later response occurs. No side-effects were noted in any of the patients.
Discussion Peripheral arterial thrombolysis is potentially of great benefit to patients with peripheral arterial thrombosis, many of whom are unsuitable for reconstructive surgery. It is, however, associated with a small but significant risk of death due principally to haemorrhagic stroke and other bleeding complications' I . Accurate patient selection is therefore important. The age of an arterial thrombus is a significant factor in determining whether peripheral arterial thrombolysis will be successful. Lesions of up to 30 days quite commonly undergo successful lysis. If older lesions are treated the success rate fails and the time taken to achieve lysis (and hence the complication rate) increases. Therefore the ability to differentiate between a truly chronic arterial occlusion and an acute or subacute arterial thrombus has important clinical implications. The previously described technique of imaging arterial thrombus using ' ' ' indium oxine-labelled platelets produces images of only moderate quality and is too slow and technically demanding to be used as a routine diagnostic tool before peripheral arterial thrombolysis. The technique described in this study appears to overcome these difficulties with high quality images being obtained as early as 4 h after a single intravenous injection. In this pilot study we have shown that imaging with I I 'In-labelled P256 Fab' identifies regions of high uptake that were in every case successfully lysed and therefore can be presumed to correspond to recent thrombus. Two problems were encountered which may limit future application of this technique. Firstly, despite successful lysis the arterial segment may still rethrombose because of inadequate run-off. Retrospective review of the P256 Fab' images and arteriograms of the two patients in which this occurred suggests that in future it may be possible to predict these cases. In both patients the region of high uptake on the P256 Fab' image was localized to the popliteal region but on arteriography there was no evidence of patent vessels distal to the knee on delayed films. It is possible that these appearances predict the presence of a localized thrombosis proximal to more chronic disease. Secondly, although the technique appears to be fairly specific for predicting thrombus lysis, it is clearly not sensitive since two of the seven patients with negative scans had successful lysis. An interesting finding in this study has been the positive P256 Fab' image obtained in a patient with arterial stenoses as opposed to arterial occlusion. This suggests that platelet deposition was occurring at the sites of these stenoses and raises the possibility that in this patient a stenosis was identified which may ultimately have occluded. We are currently undertaking
Br. J. Surg., Vol. 78, No. 9, September 1991
further studies in patients with arterial stenoses that on current criteria do not justify treatment, to explore whether this technique can identify a subgroup of patients with thrombogenic stenoses in whom acute arterial thrombosis is imminent. This study has demonstrated that in uivo platelet labelling using ' ' 'In-labelled P256 Fab' may be used to identify arterial thrombi. The technique is an advance on current platelet labelling techniques using ' ' 'indium oxine. The small numbers in this pilot study prevent any conclusions from being made on the ability of the technique to predict successful thrombolysis. However, we believe that the results are sufficiently encouraging to merit further study, and that in the future P256 Fab' imaging may be a useful investigative tool for assessing the age of arterial thrombi and hence the likely outcome of thrombolysis.
Acknowledgements We thank Amersham International plc, Amersham, UK, who kindly supplied the P256 Fab' antibody.
References 1. 2. 3. 4.
5. 6.
7.
Risius B, Groar RA, Geisibger MA e/ a/. Recombinant human tissue type plasminogen activator for thrombolysis in peripheral arteries and bypass grafts. Radiology 1986; 160: 183-8. McNamara TO, Fischer JA. Thrombolysis of peripheral arterial and graft occlusions: improved results using high dose urokinase. A m J Radio1 1985; 144: 769-75. Walker WJ, Giddings AEB. A protocol for safe treatment of acute lower limb ischaemia with intra-arterial streptokinase and surgery. Br J Surg 1988; 75: 1189-92. Van Breda A, Katzen BT. Radiological aspects of intra-arterial thrombolytic therapy. In: Comerota AJ, ed. Thrumholytic Therapy. Orlando: Grune and Stratton, 1988: 99-124. Davis HH, Siege1 BA, Joist J H et ul. Scintigraphic detection of atherosclerotic lesions and venous thrombi in man by indium-1 1 1-labelled autologous platelets. Lancet 1978; i : 1185-7. Seebold JE, Conrad G R , Kimball DA, Ponto JA, Bricker JA. Pitfalls in establishing the diagnosis of deep venous thrombophlebitis by indium-I 1 I platelet scintigraphy. J Nucl Med 1988; 29: 1169-80. Goldman M, Norcott HC, Hawker RJ, Hail C , Drole Z, McCollum CN. Femoro-popliteal bypass g r a h an isotope technique allowing in uivo comparison of thrombogenicity. Br J Surg 1982; 69: 380-2. Lavender JP, Stuttle AWJ, Peters AM, Harrison RC, Murphy GJ. Jmaging venous thrombi in the post-operative patient using indium-I 11 P256 Fab' monoclonal antibody. Nucl Med Commun 1989; 10: 375. Berridge DC, Gregson RHS, Hopkinson BR, Makin GS. Intra-arterial thrombolysis using recombinant tissue plasminogen activator (r-TPA): the optimal agent, at the optimal dose? Eur J Vusc Surg 1989; 3: 327-32. Frier M , Perkins A, Berridge DC el a/. Characterisation and clinical use of P256 Fab' platelet specific monoclonal antibody in the detection of arterial thrombosis. In: Schmidt HAE, Chambon J, eds. Nucleur Medicine Quantitative. Ana1ysi.s in Imaging and Func,/ion. Stuttgart: Schauttauer, 1990: 288-90. Berridge DC, Makin GS, Hopkinson BR. Local low-dose thrombolytic therapy: the risk of stroke or major haemorrhage. Br J Surq 1989; 76: 1230-33. -
8.
9.
10.
II.
Paper accepted 23 April 1991
1133
D. C. Berridge, A. C. Perkins", M. Frier*, R. J. Lonsdale, K. C. Ballantyne, M. L. Wastie*, G. S. Makin and B. R . Hopkinson Departments of Vascular Surgery and *Medical Physics, University Hospital, Queen's Medical Centre, Nottingham. UK Correspondence to: Mr D. C. Berridge, Middlesbrough General Hospital, Ayresome Green Lane, Middlesbrough, Cleveland TS5 5A2, U K
Detection and characterization of arterial thromboses using a platelet-specif ic monoclonal antibody (P256 Fab') Arteriography does not reliably distinguish between acute and chronic arterial occlusions. Seventeen patients with acute lower limb ischaemia were investigated by arteriography and by imaging with a plateletspec$c monoclonal antibody (P256 Fab'); 20 M B q "'In-labelled P256 Fah' was administered intravenously and patients were imaged at intervals of hetween 20 min and 24 h. Thirteen patients were subsequently treated with intra-arterial thrombolysis. In six the images showed ,foci of increased uptake qf ' ' I In-labelled P256 Fab' and the corresponding arterial segment was recanalized. Patency to 30 days was maintained in ,four cases. Seven patients had negative scans, only four ofwhom achieved lysis, and two of these suflered early rethrombosis. The remaining four patients were excluded from thrombolysis by the arteriographic appearances. In-labelled P2.56 Fab' imaging can identij" sites of acute arterial thrombosis and may have clinical applications in the management of peripheral vascular disease. Further studies are required to test whether the technique has a role to play in patient selection f o r thrombolysis.
Peripheral arterial thrombolysis is being increasingly used in the treatment of acute and subacute lower limb ischaemia with favourable results' - 3 . Its use in the treatment of chronic arterial occlusion has been less encouraging4. Arteriography cannot distinguish between recent and chronic occlusion and at present this aspect of patient selection depends primarily on clinical history. Despite a policy of restricting lysis to patients with a history of less than 30 days, in a number of patients there is no radiological evidence of lysis. It seems likely that in these patients the arterial occlusion is chronic and the clinical history is unreliable. Platelet imaging using 'indium oxine-labelled platelets has been previously shown to be capable of demonstrating arterial, intracardiac' and venous thrombi6. It has also been of use in the investigation of platelet deposition on arterial prosthetic grafts'. However, this technique requires considerable time and technical skill for cell separation and labelling. A further problem is that, owing to incomplete cell separation, there is often a substantial contamination of the platelet plug with leucocytes which, when labelled, produces a relatively high background uptake. This high background uptake reduces image contrast and necessitates long imaging times to obtain satisfactory results. It is therefore not ideally suited to widespread use as a means of detecting acute arterial thrombosis. The present study was carried out using a recently developed immunoglobulin G I (IgG, ) mouse monoclonal antibody fragment specific for the glycoprotein IIb/IIIa receptor on platelets (P256 Fab')8. This agent was assessed for its ability to detect arterial thrombus quickly and reliably. In addition, the extent of uptake was compared with the subsequent success of thrombolytic therapy.
''
"'
studied. All gave informed consent to participate in the study, which was approved by the Hospital Ethical Committee and the Administration of Radioactive Substances Advisory Committee. One hundred micrograms of P256 Fab' (Amersham International plc. Amersham, U K ) was labelled with 20 MBq "'indium chloride (INSIP. Amersham International plc). Before injection, 5 ml venous blood was obtained for subsequent anti-mouse antibody studies. The serum was separated and stored at -4O'C until analysed. The P256 antibody preparation was given in a volume of 10ml by slow intravenous injection. A further venous blood sample was taken after 20 min to perform estimates of platelet-associated radioactivity. Images were recorded for 300 s per view, using a large field of view IGE 400AC ;.-camera fitted with a medium energy collimator (300 keV maximum) and dual energy windows centred on both photopeaks of '"In (173, 247 keV). Images were obtained after 20min, 4-5 h. and 24 h. Immediately after the last imaging period, the patients underwent arteriography and subsequent intra-arterial thrombolysis if this was still considered appropriate at this stage. The P256 images were not used in the selection of patients for treatment. The protocol for jntra-arterial thrombolysis has previously been reported'. The results of the imaging technique and its comparison with arteriography and the outcome of treatment were assessed at the end of the trial. A further venous sample was obtained from seven patients 3 weeks after the study to assess any anti-mouse antibody response. All samples were assayed using an immunoenzyme procedure (ETI-Hamak. Sorin Biomedica, Salvggia, Italy).
Results
Seventeen patients with a history of sudden development or deterioration of lower limb ischaemia within the preceding 30 days and who were considered suitable for thrombolysis on clinical grounds were
Of the 17 patients studied, 13 subsequently underwent peripheral arterial thrombolysis (four were excluded from thrombolysis because of the appearances at subsequent arteriography). In the group undergoing thrombolysis, there were six patients in whom positive P256 Fab' antibody images were obtained and seven in whom negative images were obtained. Positive uptake was visualized as localized regions of high uptake corresponding to an occluded arterial segment on arteriography (Figure I ) . This was seen as early as 5 h after injection with, in some cases, improved definition after 24 h.
1130
~-1323/91/09113&04
Patients and methods
0 1991 Butterworth-Heinemann Ltd
Imaging of arterial thromboses: D. C. Berridge et al.
Table 1 Details of scan result, treatment and outcome in 17 palienrs Patient no.
Duration of history (days)
Scan result
Undergoing thrombolysis Positive 1 14 Positive 2 14 Positive 3 I Positive 4 14 Positive 5 5 Positive 6 9 I 28 Negative 8 21 Negative 9 28 Negative 10 10 Negative 11 16 Negative Negative 12 3 13 21 Negative Excluded from thrombolysis 14 28 Positive Positive 15 4 16 17
Figure 1 a Image obtained after 5 h demonstrates discrete upiake foci in the proximal and distal left superficial femoral artery. b, c Subsequent arteriography confirms an occlusion in this artery, and suggests that the occlusion (thrombus) continues into the popliteal artery. d Thrombolysis readily Iyses the thrombus but only to the extent shown on the P256 Fab' image. Two major collaterals perfuse the lower limb and have remained patent after 3 months
Br. J. Surg., Vol. 78, No. 9, September 1991
2 14
Negative Negative
Initial lysis
Outcome
Yes Yes Yes Yes Yes Yes No Yes Yes Yes No Yes No
Rethrombosed Successful Successful Successful Successful Ret hrom bosed Failed Rethrombosed Successful Rethrombosed Failed Successful Failed
Treated with angioplasty Iliac aneurysms (aortobifemoral graft) Two ipsilateral occlusions Two ipsilateral occlusions
O n commencing thrombolysis in the six patients with positive images, there was rapid lysis of thrombus in the arterial segment corresponding to the site of high uptake. In four patients this resulted in restoration of arterial patency which was maintained at 30 days. In the remaining two patients severe arterial disease below the thrombosed segment was revealed. In neither case was this amenable to angioplasty or bypass and in both cases the lack of run-off resulted in early rethrombosis (Table 2 ). The results of thrombolysis in the seven patients with negative images were less good' In Only two patients was thrombobsis s ~ X e s s f uwith l arterial Patency maintained at 30 days. In three patients there was no significant thrombus lYSiS at all, and in the final two patients lysis occurred but was incomplete and rapid rethrombosis occurred.
1131
Imaging of arterial thromboses: D. C. Berridge et al.
Figure 2 a Image obtained afier 5 h reveals two,foci of increased uptake
in the lower right superficial femoral artery. b Pelvic views show increased uptake in the right and left common iliac arteries and right femoral arteries. Subsequent ultrasonography confirmed bilateral iliac aneurysms. Arterial reconstruction was performed and the emboli were extracted
Four patients were excluded from thrombolysis. Two had both iliac and superficial femoral artery occlusions on the same side, one of which was almost certainly chronic, and therefore it was felt that the likelihood of a successful outcome from thrombolysis was significantly reduced; surgical reconstruction was carried out instead. The other two patients were particularly interesting. In the first, bilateral regions of high
1132
Figure 3 a Image after 5 I7 den7orrstrati17g two h i g h l ~positire ~ foci separated by a less distinct,focus. b Subsequerit arteriographj rewals that these foci iiwe at sites of 90 and 75 per cent stenoses respec'tirelj.
uptake were seen in the pelvis together with an additional focus of high uptake corresponding to the tibioperoneal trunk (Figure 2 ) . Ultrasonography revealed the presence of clinically occult bilateral iliac aneurysms and it seems likely that distal embolization from these was responsible for the distal occlusion. An aortobifemoral graft with ligation of the iliac aneurysms was performed with a successful outcome. The final patient had two areas of high uptake in the superficial femoral artery (Figure 3 ) ; arteriography revealed these to correspond to 75
Br. J. Surg.. Vol. 78, No. 9, September 1991
Imaging of arterial thromboses: D. C. Berridge et al.
and 90 per cent stenoses respectively. These were dilated by balloon angioplasty. Assay of the blood samples taken 20 min after injection showed approximately 80 per cent of the blood radioactivity to be associated with circulating platelets". Assay of the blood from seven patients taken 3 weeks after the study showed no evidence ofproduction of human anti-mouse antibody. A longer term follow-up is being undertaken to determine whether a later response occurs. No side-effects were noted in any of the patients.
Discussion Peripheral arterial thrombolysis is potentially of great benefit to patients with peripheral arterial thrombosis, many of whom are unsuitable for reconstructive surgery. It is, however, associated with a small but significant risk of death due principally to haemorrhagic stroke and other bleeding complications' I . Accurate patient selection is therefore important. The age of an arterial thrombus is a significant factor in determining whether peripheral arterial thrombolysis will be successful. Lesions of up to 30 days quite commonly undergo successful lysis. If older lesions are treated the success rate fails and the time taken to achieve lysis (and hence the complication rate) increases. Therefore the ability to differentiate between a truly chronic arterial occlusion and an acute or subacute arterial thrombus has important clinical implications. The previously described technique of imaging arterial thrombus using ' ' ' indium oxine-labelled platelets produces images of only moderate quality and is too slow and technically demanding to be used as a routine diagnostic tool before peripheral arterial thrombolysis. The technique described in this study appears to overcome these difficulties with high quality images being obtained as early as 4 h after a single intravenous injection. In this pilot study we have shown that imaging with I I 'In-labelled P256 Fab' identifies regions of high uptake that were in every case successfully lysed and therefore can be presumed to correspond to recent thrombus. Two problems were encountered which may limit future application of this technique. Firstly, despite successful lysis the arterial segment may still rethrombose because of inadequate run-off. Retrospective review of the P256 Fab' images and arteriograms of the two patients in which this occurred suggests that in future it may be possible to predict these cases. In both patients the region of high uptake on the P256 Fab' image was localized to the popliteal region but on arteriography there was no evidence of patent vessels distal to the knee on delayed films. It is possible that these appearances predict the presence of a localized thrombosis proximal to more chronic disease. Secondly, although the technique appears to be fairly specific for predicting thrombus lysis, it is clearly not sensitive since two of the seven patients with negative scans had successful lysis. An interesting finding in this study has been the positive P256 Fab' image obtained in a patient with arterial stenoses as opposed to arterial occlusion. This suggests that platelet deposition was occurring at the sites of these stenoses and raises the possibility that in this patient a stenosis was identified which may ultimately have occluded. We are currently undertaking
Br. J. Surg., Vol. 78, No. 9, September 1991
further studies in patients with arterial stenoses that on current criteria do not justify treatment, to explore whether this technique can identify a subgroup of patients with thrombogenic stenoses in whom acute arterial thrombosis is imminent. This study has demonstrated that in uivo platelet labelling using ' ' 'In-labelled P256 Fab' may be used to identify arterial thrombi. The technique is an advance on current platelet labelling techniques using ' ' 'indium oxine. The small numbers in this pilot study prevent any conclusions from being made on the ability of the technique to predict successful thrombolysis. However, we believe that the results are sufficiently encouraging to merit further study, and that in the future P256 Fab' imaging may be a useful investigative tool for assessing the age of arterial thrombi and hence the likely outcome of thrombolysis.
Acknowledgements We thank Amersham International plc, Amersham, UK, who kindly supplied the P256 Fab' antibody.
References 1. 2. 3. 4.
5. 6.
7.
Risius B, Groar RA, Geisibger MA e/ a/. Recombinant human tissue type plasminogen activator for thrombolysis in peripheral arteries and bypass grafts. Radiology 1986; 160: 183-8. McNamara TO, Fischer JA. Thrombolysis of peripheral arterial and graft occlusions: improved results using high dose urokinase. A m J Radio1 1985; 144: 769-75. Walker WJ, Giddings AEB. A protocol for safe treatment of acute lower limb ischaemia with intra-arterial streptokinase and surgery. Br J Surg 1988; 75: 1189-92. Van Breda A, Katzen BT. Radiological aspects of intra-arterial thrombolytic therapy. In: Comerota AJ, ed. Thrumholytic Therapy. Orlando: Grune and Stratton, 1988: 99-124. Davis HH, Siege1 BA, Joist J H et ul. Scintigraphic detection of atherosclerotic lesions and venous thrombi in man by indium-1 1 1-labelled autologous platelets. Lancet 1978; i : 1185-7. Seebold JE, Conrad G R , Kimball DA, Ponto JA, Bricker JA. Pitfalls in establishing the diagnosis of deep venous thrombophlebitis by indium-I 1 I platelet scintigraphy. J Nucl Med 1988; 29: 1169-80. Goldman M, Norcott HC, Hawker RJ, Hail C , Drole Z, McCollum CN. Femoro-popliteal bypass g r a h an isotope technique allowing in uivo comparison of thrombogenicity. Br J Surg 1982; 69: 380-2. Lavender JP, Stuttle AWJ, Peters AM, Harrison RC, Murphy GJ. Jmaging venous thrombi in the post-operative patient using indium-I 11 P256 Fab' monoclonal antibody. Nucl Med Commun 1989; 10: 375. Berridge DC, Gregson RHS, Hopkinson BR, Makin GS. Intra-arterial thrombolysis using recombinant tissue plasminogen activator (r-TPA): the optimal agent, at the optimal dose? Eur J Vusc Surg 1989; 3: 327-32. Frier M , Perkins A, Berridge DC el a/. Characterisation and clinical use of P256 Fab' platelet specific monoclonal antibody in the detection of arterial thrombosis. In: Schmidt HAE, Chambon J, eds. Nucleur Medicine Quantitative. Ana1ysi.s in Imaging and Func,/ion. Stuttgart: Schauttauer, 1990: 288-90. Berridge DC, Makin GS, Hopkinson BR. Local low-dose thrombolytic therapy: the risk of stroke or major haemorrhage. Br J Surq 1989; 76: 1230-33. -
8.
9.
10.
II.
Paper accepted 23 April 1991
1133
