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The prediction of cardiac risk in patients undergoing vascular surgery
Volume 7 Sumber 4 April 19xx
Ahtmts
the previous group, but in addition a 7 mm internal diameter shunt was connected bcnvcen a T-piece inserted into the aorta at the left subclavian artcry and immediately above the diaphragm. There were no significant left ventricular hcmodynamic advantages with shunting. Shunting significantly increased lumbar spinal cord blood flow (p = 0.0009), which correlated with the distal aortic mean pressure (r = 0.59, p = 0.008). However, lower thoracic spinal cord blood flow did not increase during shunting (p = 0.2) and did not correlate with the distal aortic pressure (r = 0.11, p = 0.64). The reason for thcsc findings was due to the vascular anatomy of the anterior spinal artery, which is as in humans smaller above (0.278 mm) than below (0.744 mm) the entry of the arteria radicularis magna. Resistance to blood flow, as calculated bv Poiscuille’s equation, was 5 1.7 times greater up the anterior spinal artery compared with down this artery. Paraplegia occurred in none of the control group animals, in four of five of the cross-clamped (nonshunted) animals. and in one of the seven shunted animals (p = 0.044). During thoracic aortic cross-clamping without distal perfusion, the lumbar spinal cord is the area most sensitive to ischemia. .A distal shunt increases lumbar spinal cord blood flow but does not oiler thoracic spinal cord blood How protection during prolonged thoracic aortic crossclamping as a result ofthc anatomv ofthe artcria radicularis magna and the anterior spinal artcry. D. Preston Univeni?
Platelet humans Stratton 722-7.
Flan&an,
of Illinois
IMD. Coilede of‘Medicim
deposition JR, Zicrler
at carotid
endarterectomy
RE, Kazmcrs
A. Stroke
sites in 1987;18:
This article summarizes the results of a study on 24 male patients who undcnvent carotid cndartcrectomv. Iridium-labclcd platelets were given intravenously mo;e than 30 minutes after completion of endartcrectomy, and imaging was done between 24 and 96 hours postoperativcly. Twelve patients had follow-up studies benvcen 2 weeks and 24 months after surgery. Six patients who had noncarotid surgery and 12 asymptomatic nonoperated patients served as control subjects. Platelet deposition was quantitated by comparison of nonopcrated and operated sites or by comparison of right and left carotid arteries in those patlcnts without carotid surgery. The patients with recent endartcrectomv had a mean deposition index of 1.7 + 0.5 compared w&h 1 .I 2 0.1 in normal subjects and 1.2 + 0.1 in surgical controls (both p < 0.05). Follow-up scans 2 weeks to 24 months after cndartercctomy documented a decreased mean dcposition index (1.0 c 0. l), suggesting reduced platelet deposition over time at the cndartercctomy site. The highest late mean deposition index was in a patient studied 1 month postoperatively. Deposition index in the patients who had
583
cndarterectomy \vas not :lecrcascd significantly by the USC of dextran (five patients; or perioperativc platclct inhibitory agents (16 patients). This study offers suggestive e\idencc in humans that increased platelet deposition occurs at the site of carotid endarterectomy. Follow-up studies suggested that platelet deposition rct&ns to normal after more than 1 month after cndartercctomy. This is a preliminary study whose results are provocative, but whose conclusions must remain speculative. The control group was not matched as to age of atherosclerotic risk factors and with the authors’ systems, it was impossible to differentiate platelet deposition within the carotid artery from periartcrial hcmatoma. Observations wcrc too few to comment on the efficacv of antithrombotic agents in preventing platclct deposition. The apparent inability of aspirin or dcxtran to influence the deposition index is of some concern. This is one of the first attempts to study the kinetics of platelet deposition after cndartercctomy in humans. It contains several \Aable obsenations and should provide an impetus for &turc study in this area. John J, Hicotta, ND. The Univeniq oj’l
Medical
Center
The prediction of cardiac risk in patients undergoing vascular surgeq IMorisc Al’, McDowell DE, Savrin RA, et al. Am J Med Sci 1987;293:150-8. The purpose of this study was to dctcrminc the value of clinical risk factors, thallium exercise testing, and radionuclidc ventricular ejection fraction to predict cardiac risk among 96 patients with peripheral vascular disease. On the basis of an initial interview, resting electrocardiogram, and examination by a cardiologist, 12 patients were thought to be at such high risk that they were treated nonoperativcly and constituted a hz@-~& group. An additional seven patients were suitable operative risks but R:ere treated conservatively. The remaining 77 patients underwent various peripheral vascular operations, including 46 procedures on the abdominal aorta. Thallium stress testing nas pcrfbrmcd on 75 surgical patients and all of those in the high-risk group. Radionuclide ventriculography was carried out on 67 surgical patients and 10 high-risk patients. Coronary angiography was performed on 31 surgical patients and all but one in the high-risk group. A Goldman risk factor index was calculated for all patients. Postoperatively, patients wcrc evaluated for the following cardiac end points: myocardial infarction, congestive heart failure, cardiogenic shock, unstable angina, and significant atria1 or ventricular dysrrhvthmia. Univariant analvsis was used to compare the predictive value of risk factors hnd the results of noninvasive tests for the occurrence of postoperative cardiac complications. There were I 1 postoperative cardiac events including six myocardial infarctions, two of which lvere fatal. Thallium stress testing was the most sensitive noninvasive test
584
Abstracts
in predicting complications; 9 of 11 patients with postoperative cardiac events had an abnormal thallium stress test (p < 0.005). Radionuclide ejection fractions tcndcd to be lower in the high-risk than the surgical group but the difference was not statistically significant. The incidence ofcomplications for both groups was higher than prediaed by the Goldman risk factor index. Of those patients who underwent coronary angiography, the high-risk group tended to have hemodynamically significant stenosis of a greater number of vessels than the surgical patients. ‘4 prcvious myocardial infarction was the strongest single determinant of cardiac risk (p = 0.025). The combination of a previous myocardial infarction and a positive thallium study had a sensitivity of 100% for predicting cardiac complications. Conversely, there wcrc no complications among patients without a previous myocardial infarction and a negative stress test. The authors concede that the primary weakness of this
BOUND VOLUMES
complicated study was the prelimmary exclusion of 12 pa. tients on the basis of initial clinical screening. Consequently, their results cannot be used as a basis for recommending preoperative screening for all peripheral vascular patients. Nc\:ertheless, the data do agree with other evidcncc showing that a previous myocardial infarction is an important risk factor for a postoperative cardiac event. Because of the low incidence of cardiac complications among patients without a previous myocardial infarction the authors imply that such patients may bc considered for operation without additional evaluation. Noninvasivc study and consideration for coronary angiography should be reserved for patients with a previous myocardial infarction. Bruce S. Cutler, MD. University of dkmdmsetts
AVAILABLE
Medtial
Center
TO SUBSCRIBERS
Bound volumes of the JCXRSAL OF VAX:UI.AR SURGERY for 1988 are available to subscribers only. They may be purchased from the publisher at a cost of S46.00 (560.00 intcrnational) for Vol. 7 (January to June) and Vol. 8 (July to Dcccmber). Price includes shipping charges. Each bound volume contains a subject and author index, and all advertising is rcmo\:ed. Copies are shipped within 60 davs at‘tcr publication of the last issue in the volume. The binding is durable buckram with the jo&nal name, volume number, and year stamped in gold on the spine. Payment must accompany all orders. Contact Circulation Fulfillmcntl The C. V. IMosby Company, 11830 Westline Industrial Drive, St. Louis, hI0 63 146, USA. In the United States call toll free: (800)325-4177, ext. 351. In Missouri call collect: (314)872-8370, ext. 351. Subscriptions must be in force to quali$. Bound volumes are not available in place of a regular JOLXSAL subscription.
Ahtmts
the previous group, but in addition a 7 mm internal diameter shunt was connected bcnvcen a T-piece inserted into the aorta at the left subclavian artcry and immediately above the diaphragm. There were no significant left ventricular hcmodynamic advantages with shunting. Shunting significantly increased lumbar spinal cord blood flow (p = 0.0009), which correlated with the distal aortic mean pressure (r = 0.59, p = 0.008). However, lower thoracic spinal cord blood flow did not increase during shunting (p = 0.2) and did not correlate with the distal aortic pressure (r = 0.11, p = 0.64). The reason for thcsc findings was due to the vascular anatomy of the anterior spinal artery, which is as in humans smaller above (0.278 mm) than below (0.744 mm) the entry of the arteria radicularis magna. Resistance to blood flow, as calculated bv Poiscuille’s equation, was 5 1.7 times greater up the anterior spinal artery compared with down this artery. Paraplegia occurred in none of the control group animals, in four of five of the cross-clamped (nonshunted) animals. and in one of the seven shunted animals (p = 0.044). During thoracic aortic cross-clamping without distal perfusion, the lumbar spinal cord is the area most sensitive to ischemia. .A distal shunt increases lumbar spinal cord blood flow but does not oiler thoracic spinal cord blood How protection during prolonged thoracic aortic crossclamping as a result ofthc anatomv ofthe artcria radicularis magna and the anterior spinal artcry. D. Preston Univeni?
Platelet humans Stratton 722-7.
Flan&an,
of Illinois
IMD. Coilede of‘Medicim
deposition JR, Zicrler
at carotid
endarterectomy
RE, Kazmcrs
A. Stroke
sites in 1987;18:
This article summarizes the results of a study on 24 male patients who undcnvent carotid cndartcrectomv. Iridium-labclcd platelets were given intravenously mo;e than 30 minutes after completion of endartcrectomy, and imaging was done between 24 and 96 hours postoperativcly. Twelve patients had follow-up studies benvcen 2 weeks and 24 months after surgery. Six patients who had noncarotid surgery and 12 asymptomatic nonoperated patients served as control subjects. Platelet deposition was quantitated by comparison of nonopcrated and operated sites or by comparison of right and left carotid arteries in those patlcnts without carotid surgery. The patients with recent endartcrectomv had a mean deposition index of 1.7 + 0.5 compared w&h 1 .I 2 0.1 in normal subjects and 1.2 + 0.1 in surgical controls (both p < 0.05). Follow-up scans 2 weeks to 24 months after cndartercctomy documented a decreased mean dcposition index (1.0 c 0. l), suggesting reduced platelet deposition over time at the cndartercctomy site. The highest late mean deposition index was in a patient studied 1 month postoperatively. Deposition index in the patients who had
583
cndarterectomy \vas not :lecrcascd significantly by the USC of dextran (five patients; or perioperativc platclct inhibitory agents (16 patients). This study offers suggestive e\idencc in humans that increased platelet deposition occurs at the site of carotid endarterectomy. Follow-up studies suggested that platelet deposition rct&ns to normal after more than 1 month after cndartercctomy. This is a preliminary study whose results are provocative, but whose conclusions must remain speculative. The control group was not matched as to age of atherosclerotic risk factors and with the authors’ systems, it was impossible to differentiate platelet deposition within the carotid artery from periartcrial hcmatoma. Observations wcrc too few to comment on the efficacv of antithrombotic agents in preventing platclct deposition. The apparent inability of aspirin or dcxtran to influence the deposition index is of some concern. This is one of the first attempts to study the kinetics of platelet deposition after cndartercctomy in humans. It contains several \Aable obsenations and should provide an impetus for &turc study in this area. John J, Hicotta, ND. The Univeniq oj’l
Medical
Center
The prediction of cardiac risk in patients undergoing vascular surgeq IMorisc Al’, McDowell DE, Savrin RA, et al. Am J Med Sci 1987;293:150-8. The purpose of this study was to dctcrminc the value of clinical risk factors, thallium exercise testing, and radionuclidc ventricular ejection fraction to predict cardiac risk among 96 patients with peripheral vascular disease. On the basis of an initial interview, resting electrocardiogram, and examination by a cardiologist, 12 patients were thought to be at such high risk that they were treated nonoperativcly and constituted a hz@-~& group. An additional seven patients were suitable operative risks but R:ere treated conservatively. The remaining 77 patients underwent various peripheral vascular operations, including 46 procedures on the abdominal aorta. Thallium stress testing nas pcrfbrmcd on 75 surgical patients and all of those in the high-risk group. Radionuclide ventriculography was carried out on 67 surgical patients and 10 high-risk patients. Coronary angiography was performed on 31 surgical patients and all but one in the high-risk group. A Goldman risk factor index was calculated for all patients. Postoperatively, patients wcrc evaluated for the following cardiac end points: myocardial infarction, congestive heart failure, cardiogenic shock, unstable angina, and significant atria1 or ventricular dysrrhvthmia. Univariant analvsis was used to compare the predictive value of risk factors hnd the results of noninvasive tests for the occurrence of postoperative cardiac complications. There were I 1 postoperative cardiac events including six myocardial infarctions, two of which lvere fatal. Thallium stress testing was the most sensitive noninvasive test
584
Abstracts
in predicting complications; 9 of 11 patients with postoperative cardiac events had an abnormal thallium stress test (p < 0.005). Radionuclide ejection fractions tcndcd to be lower in the high-risk than the surgical group but the difference was not statistically significant. The incidence ofcomplications for both groups was higher than prediaed by the Goldman risk factor index. Of those patients who underwent coronary angiography, the high-risk group tended to have hemodynamically significant stenosis of a greater number of vessels than the surgical patients. ‘4 prcvious myocardial infarction was the strongest single determinant of cardiac risk (p = 0.025). The combination of a previous myocardial infarction and a positive thallium study had a sensitivity of 100% for predicting cardiac complications. Conversely, there wcrc no complications among patients without a previous myocardial infarction and a negative stress test. The authors concede that the primary weakness of this
BOUND VOLUMES
complicated study was the prelimmary exclusion of 12 pa. tients on the basis of initial clinical screening. Consequently, their results cannot be used as a basis for recommending preoperative screening for all peripheral vascular patients. Nc\:ertheless, the data do agree with other evidcncc showing that a previous myocardial infarction is an important risk factor for a postoperative cardiac event. Because of the low incidence of cardiac complications among patients without a previous myocardial infarction the authors imply that such patients may bc considered for operation without additional evaluation. Noninvasivc study and consideration for coronary angiography should be reserved for patients with a previous myocardial infarction. Bruce S. Cutler, MD. University of dkmdmsetts
AVAILABLE
Medtial
Center
TO SUBSCRIBERS
Bound volumes of the JCXRSAL OF VAX:UI.AR SURGERY for 1988 are available to subscribers only. They may be purchased from the publisher at a cost of S46.00 (560.00 intcrnational) for Vol. 7 (January to June) and Vol. 8 (July to Dcccmber). Price includes shipping charges. Each bound volume contains a subject and author index, and all advertising is rcmo\:ed. Copies are shipped within 60 davs at‘tcr publication of the last issue in the volume. The binding is durable buckram with the jo&nal name, volume number, and year stamped in gold on the spine. Payment must accompany all orders. Contact Circulation Fulfillmcntl The C. V. IMosby Company, 11830 Westline Industrial Drive, St. Louis, hI0 63 146, USA. In the United States call toll free: (800)325-4177, ext. 351. In Missouri call collect: (314)872-8370, ext. 351. Subscriptions must be in force to quali$. Bound volumes are not available in place of a regular JOLXSAL subscription.