- Email: [email protected]
Anti-thrombotic drugs following angioplasty
CORRESPONDENCE mal disease- we believe the pattern reflects the histology- but clear proof still eludes us Computerized systems for tissue characterization appear attractive but have so far had limited success. It would be of interest to know if Davies et al. (1991) took account of observer variation in the preparation of this study and how they took steps to mlmmlze ~ts ~mpact. A. C. L A M O N T
Consultant Paediatric Radiologist Leicester Royal Infirmary Leicester LE1 5 W W
References
Barlow, HB (1977). The efficiency of detecting changes in density of random dot patterns. Vision Research, 18, 637 650. Burgess, AE, Wagner, R F & Jennings, RJ (1981). Efficiency of human visual signal discrimination. Science, 214, 93-94. Davies, RJ, Saverymuttu, SH, Fallowfield, M & Joseph, AEA (1991). Paradoxical lack of ultrasound attenuation with gross fatty change in the liver. Clinical Radiology, 43, 393-396. Joseph, AEA, Dewbury, KC, McGuire, P G (1979). Ultrasound in the detection of chronic liver disease ("the bright liver"). British Journal of Radiology, 52, 184 188. Lamont, AC,.Graebe, AC, Pelmore, JM & Thompson, JR (1990). Ultrasound assessment of renal cortical brightness in infants: is naked eye evaluation reliable? Investigative Radiology, 25, 250 253.
43 7
Dipyridamole. The Dipyridamole was often stopped after about 3 months, but the Aspirin continued for life. Just recently this practice has been stopped by the vascular surgeons, needless to say without any prior discussion with the radiologists. I have therefore taken the step of prescribing the drugs myself for all my angioplasty patients. This raises the issue of who is responsible for the decision about drugs post-angioplasty - the radiologist or the surgeon? If the radiologists are to prescribe, they should do so with the full knowledge of the best current practice. I have searched the literature to no avail to see if current opinion has changed on this topic. Muller et al. (1990) have recently shown that Dipyridamole alone or combined with low dose Aspirin inhibits platelet aggregation in human whole blood. Their study was stimulated by the increased use of anti-thrombotics particularly following aorto-coronary vein grafts. Hess et al. (1985) showed that significantly more occlusions occurred in those patients not given antithrombotic drugs post-angioplasty than in those who were. The dose used in this study was 75 mg Dipyridamole and 330 mg Aspirin. Heiss et al. (1990) have recently confirmed that a dose of 330 mg Aspirin combined with 75 mg Dipyridamole has a statistically significant effect in preventing reocclusion post-angioplasty when compared with placebo or 100 mg Aspirin combined with 75 mg Dipyridamole. The questions of who should prescribe anti-thrombotics and in what dose should be excellent topics for investigation and probably Audit on a national basis. E. A. N O R T H
Department of Diagnostic Radiology St. Helier Hospital Carshalton Surrey
References
POSTSCRIPT SIR Thank you for accepting my letter to Clinical Radiology regarding brightness of echoes. You may wish to include the following as a postscript. Since my recent communication, a paper by Eggert et al. (1991) in which echogenicity was compared with densitometric readings, has come to my attention. Their results confirm that naked eye evaluation does not permit clear distinction between categories of echogenicity. A. C. L A M O N T
Heiss, HW, Just, H, Middleton, D & Deichsel, G (1990). Reocclusion prophylaxis with Dipyridamole combined with Acetylsalicylic Acid following PTA. Angiology, 41, 263 269. Hess, H, Mietaschk, A & Deichsel, G (I 985). Drug induced inhibition of platelet function delays progression of peripheral occlusive arterial disease. Lancet, l, 415 419. Muller, TH, Weisenberger, H, Brickl, R, Nehmiz, G & Eisert, WG (1990). Dipyridamole alone or combined with low dose acetylsalicylic acid inhibits platelet aggregation in human whole blood ex vivo. British Journal of Clinical Pharmacology, 30, 179 186.
Reference
Eggert, P, Debus, F, Kreller-Laugwitz, G & Oppermann, HC (1991). Densitometric measurement of renal echogenicity in infants and naked eye evaluation: a comparison. Pediatric Radiology, 21, 111113.
SEVERE REACTION TO ORAL I O H E X O L SIR We read with interest the recent case report by Glover and Thomas (1991) of a severe reaction to oral iohexol, but were dismayed to see that the study had been termed a 'follow through' examination. Gastrointestinal radiologists have been trying to educate clinical colleagues against requesting the 'follow through'. When performed in combination with a conventional double contrast meal it gives a low diagnostic yield; in reality the two examinations are not compatible. We have trained our radiologists to use the term 'small bowel study' to indicate a dedicated procedure. The term 'follow through' examination should have been removed from the radiologist's vocabulary years ago. A. G R U N D Y J. D O W
Department of Diagnostic Radiology St George's Hospital Blackshaw Road London SW17 OQT
INJURY TO THE M A J O R AIRWAYS
S i n - T h e article by Spencer et al. (1991) admirably succeeded in clarifying the radiological clues to early diagnosis of injury to the major airways. I would like to point out, however, that the sign of hyoid bone elevation (Polansky et al., 1984) has been entirely omitted from their paper. This consists of elevation of the hyoid bone above a line projected along the top of the body of the third cervical vertebra, provided the patient's mouth is closed and that he is not swallowing at the time of the radiograph (Tobias et al., 1989). While it is clear that two of the three patients with laryngeal injuries reported by Spencer et al. (1991) had obvious disruption of the airway on the lateral cervical radiograph, such disruption is not necessarily obvious. Indeed the paper does not comment on the third case and it seems likely that the sign of hyoid elevation would be crucial in this case. A glance at Fig. 3 of the paper in fact demonstrates that the sign of hyoid elevation was present in the case illustrated, even though the sign is not mentioned in their paper. Elevation of ~ e hyoid bone may draw attention pre-operatively to the possibility of either a cricotracheal separation or a tracheal transection. M. E. TOBIAS
Brenthurst Clinic PO Box 370 Johannesburg 2000 South Africa
Reference
References
Glover, JR & Thomas, BU (1991). Severe adverse reaction to oral iohexol. Clinical Radiology, 44, 137 138.
Polansky, A, Resnick, D, Sofferman, R A & Davidson, TM (1984). Hyoid bone elevation: a sign of tracheal transection. Radiology, 150, 117-120. Spencer, IA, Rogers, CE & Westaby, S (1991). Clinico-radiological correlates in rupture of the major airways. Clinical Radiology, 43, 371 376. Tobias, ME, Sacks, AD, Carter, G & McIntosh, WA (1989). Cricotracheal separation in blunt neck injury the sign of hyoid bone elevation. South African Journal of Surgery, 27, 189-191.
A N T I - T H R O M B O T I C DRUGS F O L L O W I N G A N G I O P L A S T Y
S m - Over the last 10 years it has been an unwritten policy for all angioplasty patients in our hospital to be prescribed Aspirin and
Consultant Paediatric Radiologist Leicester Royal Infirmary Leicester LE1 5 W W
References
Barlow, HB (1977). The efficiency of detecting changes in density of random dot patterns. Vision Research, 18, 637 650. Burgess, AE, Wagner, R F & Jennings, RJ (1981). Efficiency of human visual signal discrimination. Science, 214, 93-94. Davies, RJ, Saverymuttu, SH, Fallowfield, M & Joseph, AEA (1991). Paradoxical lack of ultrasound attenuation with gross fatty change in the liver. Clinical Radiology, 43, 393-396. Joseph, AEA, Dewbury, KC, McGuire, P G (1979). Ultrasound in the detection of chronic liver disease ("the bright liver"). British Journal of Radiology, 52, 184 188. Lamont, AC,.Graebe, AC, Pelmore, JM & Thompson, JR (1990). Ultrasound assessment of renal cortical brightness in infants: is naked eye evaluation reliable? Investigative Radiology, 25, 250 253.
43 7
Dipyridamole. The Dipyridamole was often stopped after about 3 months, but the Aspirin continued for life. Just recently this practice has been stopped by the vascular surgeons, needless to say without any prior discussion with the radiologists. I have therefore taken the step of prescribing the drugs myself for all my angioplasty patients. This raises the issue of who is responsible for the decision about drugs post-angioplasty - the radiologist or the surgeon? If the radiologists are to prescribe, they should do so with the full knowledge of the best current practice. I have searched the literature to no avail to see if current opinion has changed on this topic. Muller et al. (1990) have recently shown that Dipyridamole alone or combined with low dose Aspirin inhibits platelet aggregation in human whole blood. Their study was stimulated by the increased use of anti-thrombotics particularly following aorto-coronary vein grafts. Hess et al. (1985) showed that significantly more occlusions occurred in those patients not given antithrombotic drugs post-angioplasty than in those who were. The dose used in this study was 75 mg Dipyridamole and 330 mg Aspirin. Heiss et al. (1990) have recently confirmed that a dose of 330 mg Aspirin combined with 75 mg Dipyridamole has a statistically significant effect in preventing reocclusion post-angioplasty when compared with placebo or 100 mg Aspirin combined with 75 mg Dipyridamole. The questions of who should prescribe anti-thrombotics and in what dose should be excellent topics for investigation and probably Audit on a national basis. E. A. N O R T H
Department of Diagnostic Radiology St. Helier Hospital Carshalton Surrey
References
POSTSCRIPT SIR Thank you for accepting my letter to Clinical Radiology regarding brightness of echoes. You may wish to include the following as a postscript. Since my recent communication, a paper by Eggert et al. (1991) in which echogenicity was compared with densitometric readings, has come to my attention. Their results confirm that naked eye evaluation does not permit clear distinction between categories of echogenicity. A. C. L A M O N T
Heiss, HW, Just, H, Middleton, D & Deichsel, G (1990). Reocclusion prophylaxis with Dipyridamole combined with Acetylsalicylic Acid following PTA. Angiology, 41, 263 269. Hess, H, Mietaschk, A & Deichsel, G (I 985). Drug induced inhibition of platelet function delays progression of peripheral occlusive arterial disease. Lancet, l, 415 419. Muller, TH, Weisenberger, H, Brickl, R, Nehmiz, G & Eisert, WG (1990). Dipyridamole alone or combined with low dose acetylsalicylic acid inhibits platelet aggregation in human whole blood ex vivo. British Journal of Clinical Pharmacology, 30, 179 186.
Reference
Eggert, P, Debus, F, Kreller-Laugwitz, G & Oppermann, HC (1991). Densitometric measurement of renal echogenicity in infants and naked eye evaluation: a comparison. Pediatric Radiology, 21, 111113.
SEVERE REACTION TO ORAL I O H E X O L SIR We read with interest the recent case report by Glover and Thomas (1991) of a severe reaction to oral iohexol, but were dismayed to see that the study had been termed a 'follow through' examination. Gastrointestinal radiologists have been trying to educate clinical colleagues against requesting the 'follow through'. When performed in combination with a conventional double contrast meal it gives a low diagnostic yield; in reality the two examinations are not compatible. We have trained our radiologists to use the term 'small bowel study' to indicate a dedicated procedure. The term 'follow through' examination should have been removed from the radiologist's vocabulary years ago. A. G R U N D Y J. D O W
Department of Diagnostic Radiology St George's Hospital Blackshaw Road London SW17 OQT
INJURY TO THE M A J O R AIRWAYS
S i n - T h e article by Spencer et al. (1991) admirably succeeded in clarifying the radiological clues to early diagnosis of injury to the major airways. I would like to point out, however, that the sign of hyoid bone elevation (Polansky et al., 1984) has been entirely omitted from their paper. This consists of elevation of the hyoid bone above a line projected along the top of the body of the third cervical vertebra, provided the patient's mouth is closed and that he is not swallowing at the time of the radiograph (Tobias et al., 1989). While it is clear that two of the three patients with laryngeal injuries reported by Spencer et al. (1991) had obvious disruption of the airway on the lateral cervical radiograph, such disruption is not necessarily obvious. Indeed the paper does not comment on the third case and it seems likely that the sign of hyoid elevation would be crucial in this case. A glance at Fig. 3 of the paper in fact demonstrates that the sign of hyoid elevation was present in the case illustrated, even though the sign is not mentioned in their paper. Elevation of ~ e hyoid bone may draw attention pre-operatively to the possibility of either a cricotracheal separation or a tracheal transection. M. E. TOBIAS
Brenthurst Clinic PO Box 370 Johannesburg 2000 South Africa
Reference
References
Glover, JR & Thomas, BU (1991). Severe adverse reaction to oral iohexol. Clinical Radiology, 44, 137 138.
Polansky, A, Resnick, D, Sofferman, R A & Davidson, TM (1984). Hyoid bone elevation: a sign of tracheal transection. Radiology, 150, 117-120. Spencer, IA, Rogers, CE & Westaby, S (1991). Clinico-radiological correlates in rupture of the major airways. Clinical Radiology, 43, 371 376. Tobias, ME, Sacks, AD, Carter, G & McIntosh, WA (1989). Cricotracheal separation in blunt neck injury the sign of hyoid bone elevation. South African Journal of Surgery, 27, 189-191.
A N T I - T H R O M B O T I C DRUGS F O L L O W I N G A N G I O P L A S T Y
S m - Over the last 10 years it has been an unwritten policy for all angioplasty patients in our hospital to be prescribed Aspirin and