1. The Clinical Problem
Of all surgical procedures, peripheral vascular surgery carries the highest mortality rate, because of the high incidence of underlying CAD (Figure 9b.1). Therefore, preoperative cardiac risk assessment and perioperative man- agement studies are frequently analyzed in patients undergoing peripheral vascular surgery.
In a landmark study by Hertzer et al.,1hemody- namically significant CAD was reported in 36%
of patients with abdominal aortic aneurysms and in 28% of patients with lower limb ischemia.
Importantly, in 94% of all cases, i.e., sympto- matic and asymptomatic vascular surgery patients, abnormalities were detected during coronary angiography. Results of perioperative management are then extrapolated from high- risk patients to the general surgical population.
Patients undergoing liver or renal transplanta- tion are other important groups and these will be discussed separately in Chapter 7b.
Peripheral vascular disease (PVD) is an increasing problem in Europe and in North America. For example, between 1980 and 1995 in the Netherlands, the number of patients admit- ted to hospital because of PVD has increased from 17 511 to 29 346. This is an increase of 36%
after correction for demographic factors.2 The high incidence of PVD was confirmed in a recent 1. The Clinical Problem . . . 209
2. Pathophysiology . . . 210 3. Perioperative Care . . . 211
3.1 Step One: Selection of Patients at
Risk . . . 211 3.2 Step Two: Additional Testing . . . 211 4. Comparison of MPS and
Echocardiography . . . 215 5. Conclusions . . . 216
Cardiovascular complications are the major cause of perioperative and late mortality and morbidity. The majority of these complications occur during the first week after surgery. Impor- tant causes for perioperative cardiac events such as myocardial infarction (MI) and death are myocardial ischemia, left ventricular (LV) dysfunction, and aortic valve stenosis. Coronary artery disease (CAD) may be asymptomatic because of reduced exercise capacity caused by noncardiac diseases such as stroke, arthritis, or claudication. To reduce perioperative cardiac mortality and morbidity, preoperative cardiac screening is of paramount importance in patients with risk factors or known CAD. This chapter discusses the role of noninvasive imaging tests in this setting with an emphasis on the assessment of risk before vascular non- cardiac surgery.
9
Prognostic Assessment by Noninvasive Imaging.
Part b. Risk Assessment Before Noncardiac Surgery by Noninvasive Imaging
Olaf Schouten, Miklos D. Kertai, and Don Poldermans
209
study from the United Kingdom; the study used ultrasound screening to show that between 1.5%
and 3% of men older than 60 years had an occult aortic aneurysm of between 40- and 59-mm diameter.3 Many of these patients require surgery with an associated 30-day operative mortality of 5%–6% and 5-year mortality of 45%, both of which arise principally from cardiac events.4This high perioperative mortal- ity was confirmed in a study by Krupski et al.5 who reported a similar cardiac event rate after infrainguinal procedures as after aortic opera- tions (9% versus 7%, respectively).
Although most physicians focus on perioper- ative management, patients should live long enough to enjoy the benefits of surgery. The 5- year mortality rate of patients with PVD ranges between 20% and 40% because of late cardiac events.6–8 Therefore, the preoperative cardiac evaluation and cardioprotective therapies, including lifestyle changes and medical therapy, should be continued after surgery. To optimize medical care, not only perioperatively but also the long-term postoperative care, it is mandatory that the treating physician evaluates the presence and extent of CAD as well as risk factors, such as hypertension and hypercholesterolemia that will determine long-term survival after surgery.
2. Pathophysiology
Cardiac events are mainly caused by myocardial ischemia. Myocardial ischemia may arise either from an increased myocardial oxygen demand or a reduced supply. In the perioperative period,
patients with suspected or known CAD are at a higher risk for an event during the operation because factors such as increased heart rate or elevated blood pressure resulting from surgical stress, pain, or the use of sympathomimetic drugs increase further myocardial oxygen demand. Decreased supply may be the result of hypotension, vasospasm, anemia, and hypoxia.
The location of a perioperative MI is not always related to the location of the culprit coro- nary lesion. In a study by Dawood et al.,9evalu- ating the pathophysiology of perioperative fatal cardiac events, evidence of plaque rupture was identified in 55% of patients. After examining the location of severe lesions, the investigators found that preoperative prediction of the site of infarction based on the severity of the underly- ing CAD would have been unsuccessful in almost half of the cases. The unpredictable progression of an (in)significant coronary lesion reduces the predictive value for tests that aim to detect the culprit lesion, such as pharmacologic stress testing, and reinforces the importance of appro- priate medical therapy that reduces coronary plaque instability.
Other important causes of perioperative cardiac events are aortic valve stenosis and LV dysfunction. For proper identification of aortic valve stenosis, echocardiography is mandatory.
Long-term cardiac complications are more common in the presence of LV dysfunction.10 Aortic valve stenosis also is an increasing problem because 6% of the population older than 80 years of age have aortic valve stenosis and an increasing number of elderly are sched- uled for surgery.11The presence of aortic valve
0 1 2 3 4 5
Ambulatory Eye Surg Thoracic Abdominal Orthopedic Vascular
0.03%; No. 45 414 0.05%; No. 10 334
0.9%; No. 2348 1.1%; No. 9200
2.7%; No. 628
4.7%; No. 30 767
Incidence of perioperative cardiac death and MI (%)
Figure 9b.1. Risk of perioperative cardiac death and MI for different types of surgery based on a study of 108 593 patients oper- ated at Erasmus MC between 1991 and 2000 (MI, myocardial infarction; eye surg, eye surgery).
3.2 Step Two: Additional Testing
Additional testing should only be performed if the results will change perioperative manage- ment. Therefore, pharmacologic stress testing should be reserved for those patients in whom the detection of CAD will lead to a change in anesthetic or surgical management or to pre- operative coronary revascularization. Referral to angiography and subsequently to coronary revascularization should only be considered in a minority of patients. The CASS (Coronary Artery Surgery Study) registry showed that patients who underwent coronary revasculariza- tion before low-risk surgery were at the same risk of perioperative death or MI (2%) as those who were not revascularized.19 Although there are few (nonrandomized) studies to evaluate the protective effect of preoperative myocardial revascularization, most studies indicate that revascularization should be performed if it would have been indicated in any case (Table 9b.3 and Table 9b.4).20 This would include patients with unstable coronary syndromes or those with extensive coronary disease or ischemia. In addition, cardioprotective therapy such as beta-blockers and statins may reduce the need for additional testing, because the periop- erative cardiac event rate is further reduced and patients are unlikely to benefit from coronary revascularization (Figure 9b.3).
There is widespread consensus that additional noninvasive testing is required in patients with at least one cardiac risk factor (angina pectoris, previous MI, diabetes mellitus, congestive heart failure, cardiac arrhythmias, age >70 years) or a reduced exercise capacity undergoing high-risk surgical procedures. The ACC/AHA algorithm for preoperative risk assessment considers initially the urgency for surgery, its inherent cardiac risk (Table 9b.5), the patient’s risk factors, and exercise tolerance. Patients with only minor clinical predictors [advanced age, abnor- mal resting electrocardiogram (ECG), previous stroke, or hypertension] who require low- to moderate-risk surgery are at low risk and do not require further investigation. Patients with inter- mediate clinical predictors (mild angina, prior infarction, treated heart failure, or diabetes) or with minor predictors and reduced exercise tol- erance need further assessment before moder- ate- or high-risk surgery.20Patients with major predictors may be considered for cancellation of stenosis increases the incidence of perioperative
cardiac death or MI four-fold, and also has important consequences for the type of anesthe- sia, e.g., general versus locoregional.12
3. Perioperative Care
3.1 Step One: Selection of Patients at Risk
Risk stratification begins with a careful clinical history and knowledge of the surgical procedure to be performed. A number of methods of quan- tifying risk have been used, the most common being the Goldman cardiac operative risk index, the Detsky modified multifactorial risk index, and Eagle’s risk factors,13–15 and these allow stratification into low, intermediate, or high risk (Table 9b.1). These indices, although in general are helpful to identify high-risk individuals, tend to underestimate the risk at the lower end of the spectrum and have a suboptimal negative pre- dictive value. In response to this drawback, the American College of Cardiology (ACC)/
American Heart Association (AHA) have pro- posed a classification of clinical predictors into major, intermediate, and minor (Table 9b.2).16 More recently, Lee et al.17have reviewed the pre- dictive value of several clinical risk factors in patients scheduled for noncardiac surgery. Six factors, i.e., high-risk surgery, stroke, diabetes mellitus, renal failure, heart failure, and ischemic heart disease, were identified in a study popula- tion of 2893 patients and later validated in a pop- ulation of 1422 patients. The rate of major perioperative complications in the presence of 0, 1, 2, or 3 risk factors was 0.4%, 0.9%, 7%, and 11%, respectively, but a limitation of the findings for assessing patients undergoing vascular surgery was that only 110 of 2893 patients (3.8%) had abdominal aortic surgery.
The importance of common clinical cardiac risk factors was recently confirmed by Boersma et al.18In a study population of 108 593 patients, the combination of risk factors such as age, gender, type of surgery, and risk factors for CAD stratified patients into low, intermediate, and high risk for perioperative death (Figure 9b.2).
For a more refined classification, however, non- invasive testing is also required and this will be discussed below.
Table 9b.1.Commonly used indices of cardiac risk OriginalDetsky et al.Larsen et al. DefinitionNo.of pointsDefinitionNo.of pointDefinitionNo.of points Ischemic heart diseaseMI within 6mo10MI within 6mo10MI within 3mo1 MI> 6mo earlier5No MI within 3mo,but pervious MI, CCS class III angina10angina pectoris,or both CCS class IV angina20 Unstable angina with 6mo10 Congestive heart failureS3gallop or regular venous distention11Pulmonary edemaPersistent pulmonary congestion12 Within 1wk10No pulmonary congestion,but previous Ever5pulmonary edema8 Neither pulmonary congestion nor 4 pervious pulmonary edema,but previous heart failure Cardiac rhythmRhythm other than sinus or PACs on last7Rhythm other than sinus or sinus5– preoperative ECGplus PACs on last preoperative ECG >5 PVCs/min at any time before surgery7>5 PVCs/min at any time before5 surgery Valvular heart diseaseImportant aortic stenosis3Suspected critical aortic stenosis20– General medical statusPO2<60mmHg or PCO2>50mmHg,potassium 3Same as for original index5Serum creatinine >1.5mg/dL (130mmol/L)2 <3.0mmol/L or bicarbonate <20mmol/L;Diabetes mellitus BUN>50mg/dL (18mmol/L) or creatinine 3 >3.0mg/dL (260mmol/L);abnormal AST signs of chronic liver disease or patient bedridden from Non-cardiac causes Age>70yr5>70yr5– Type of surgeryIntraperitoneal,intrathoracic,or nortic operation3Emergency operation10Emergency operation3 Emergency operation4Aortic operation5 Other intraperitoneal or pleural operation3 MI,myocardial infarction;CCS,PAC,premature atrial contraction;PVC,premature ventricular contraction.
Table 9b.2. Clinical predictors of increased perioperative cardiac risk (ACC/AHA guidelines 2002)
Major
Unstable coronary syndromes Decompensated CHF Severe valvular disease
Significant arrhythmias (high-grade AV block, symptomatic ventricular arrhythmias, SVT with uncontrolled ventr. rate
Intermediate Mild angina pectoris Prior MI
Compensated or prior CHF Diabetes mellitus Minor
Advanced age Abnormal ECG Rhythm other than sinus Low functional capacity History of stroke Uncontrolled HTN
ACC, American College of Cardiology; AHA, American Heart Association; CHF, Chronic heart failure; AV, atrio-ventricular; SVT, sustained ventricular tochycardia; HTN, hypertension.
Age (yr)
£40 41 - 50 51 - 60 61 - 70 71 - 80
>80
0 5 10 15 20 25 Gender
Female male
0 1 Type of surgery
Breast; Dental; Eye;
Gyneacology; Urologic Endocine; Orthopedic;
Plastic / Reconstructive Abdomined; Ear, Nose, Throat; Pulmonary Neuro; Renal transplant;
Vascular
0 20 25 30
Procedure Laparoscopic Non-laparoscopic Elective Acute
0 5 0 15
2 2 5 5 10 Clinical risk factors
Coronary artery disease Renal failure Diabetes mellitus Hypertension Heart failure
61 - 100
51 - 60
41 - 50
31 - 40
0 - 30
87 per 1,205
221 per 8,768
7.2%
2.5%
0.8%
195 per 23,157
57 per 27,509
13 per 47,954 0.2%
0.03%
0 2.5 5.0 7.5
CVD mortality (%) +
+
+
+
+
Resting ECG
The resting ECG is abnormal in case of atrial fbrilation/flurter, left ventricular hypertrophy, PVC,pacemaker, Qwave, or ST-depression, and normal otherwise
N A
N A
N A
N A
N A
0 2.5 5.0 7.5 10.0
CVD mortality (%) 2.1% (2 per 97)
1.3% (22 per 1,725) 3.4% (56 per 1,626)
0.5% (34 per 6,493) 1.8% (52 per 2,848)
0.1% (7 per 6,762) 0.5% (8 per 1,537)
0.07% (4 per 5,588) 0.06% (1 per 1,553)
9.2% (21 per 228)
Figure 9b.2. Risk score developed by Boersma et al.18in which ECG and stress echocardiography can be incorporated. Points for risk factors in the left boxes are added and subsequently the risk on cardiovascular mortality can be quantified with or without further differentiation by ECG. CVD, cardiovascular disease; PVC, premature ventricular contraction.
Table 9b.3. Indications for coronary angiography Class I
Evidence for high risk or adverse outcomes based on noninvasive test results
Angina unresponsive to medical treatment Unstable angina
Nondiagnostic noninvasive tests in patients with high clinical risk of CHD who are undergoing high-risk surgery
Class IIa
Moderate to large ischemic areas but with preserved LVF Nondiagnostic noninvasive tests in patients with intermediate clinical risk of CHD who are undergoing high-risk surgery
Urgent noncardiac surgery in patients recovering from an acute MI CHD: Coronan heart disease; ACC/AHA guidelines* see text, page 211.
the operation and risk-factor modification or for coronary angiography.
Myocardial perfusion scintigraphy (MPS) can provide useful information about cardiac risk in patients requiring noncardiac surgery.
Numerous studies21–47 have been performed in this setting and, in a meta-analysis of 3718 patients undergoing vascular and other surgery, the positive predictive value of inducible
ischemia for perioperative death or infarction was 12.9% compared with a negative predic- tive value of 98.6%, a risk ratio of 9.1 (Table 9b.6).
Several studies of dobutamine stress echocardiography (DSE) for preoperative risk stratification50–56have also been performed showing comparable positive and negative predictive values with MPS.
Table 9b.4. Risk of procedure Is the noncardiac operation necessary?
If yes, medical therapy or revascularize?
Revascularize only if otherwise indicated No studies to demonstrate prognostic benefit of PCI
No studies of staged or simultaneous revascularization if peripheral or carotid vascular surgery
Preoperative coronary angioplasty
No randomized clinical trials documenting decreased incidence of perioperative cardiac events
No prospective studies to determine optimal period of delay Medical therapy
Beta-blockade for hypertension, angina, or tachyarrhythmia Peri-operative nitrates reduce ischemia but no effect on postoperative
events
Preoperative intensive care for heart failure Anesthetic considerations (hypotension) Management of pain, fluid balance, coagulation PCI, percutaneous coronary intervention.
ACC/AHA algorithm
Table 9b.5. Risk of procedure
High> 5% Emergency surgery, especially in elderly Aortic/major vascular
Peripheral vascular Prolonged surgery 5 h Intermediate 1%–5% Carotid endarterectomy
Head and neck Intraperitoneal/intrathoracic Orthopedic
Prostate
Low < 1% Endoscopic procedures Superficial procedure Cataract Breast
ACC/AHA guideline for perioperative cardiovascular evaluation
Days after Surgery 0
0 10 20 30 40
7 14 21 28
Bisoprolol P<0.001
Standard care
Percentage of Patients
No. AT Risk Standard care Bisoprolol
53 59
38 58
37 57
37 57
35 57
Figure 9b.3. The effect of bisoprolol on perioperative mortality and MI in high-risk patients undergoing vascular surgery. There was a 10-fold increase in event rate in the standard group.
tive image analysis (severity of the abnormalities assessed by segmental analysis) and for any amount of ischemia, the presence of comorbid- ity (e.g., prior CAD, diabetes mellitus, atrial fibrillation) increases further the risk for a hard event. In addition, fixed defects or impaired ven- tricular function (Tables 9b.7 & 9b.8) were found
4. Comparison of MPS and Echocardiography
Unfortunately, there has been no direct compar- ison of these techniques in perioperative risk assessment. The meta-analysis of Shaw et al.57 compares dipyridamole perfusion imaging and DSE, although not in the same patients.
Both tests had comparable predictive accuracy although the summed odds ratios for cardiac death and MI were greater for DSE than for dipyridamole perfusion imaging. However, the confidence intervals for the echocardiography figures were large because of the smaller number of patients. The results of this analysis show that reversible perfusion defects or inducible wall motion abnormalities [Table 9b.7 and Figure 9b.4 (see color section)] predict adverse out- comes during the perioperative period. The prognostic power increases with semiquantita-
Table 9b.6. MPS for preoperative assessment of cardiac risk
Inducible MI/death,
Year Author n ischemia, n (%) n (%) PPV NPV
Vascular surgery
1985 Boucher 48 16 (33) 3 (6) 19% (3/16) 100% (32/32)
1987 Cutler 116 54 (47) 11 (10) 20% (11/54) 100% (60/60)
1988 Fletcher 67 15 (22) 3 (4) 20% (3/15) 100% (56/56)
1988 Sachs 46 14 (31) 2 (4) 14% (2/14) 100% (24/24)
1989 Eagle 200 82 (41) 15 (8) 16% (13/82) 98% (61/62)
1990 McEnroe 95 34 (36) 7 (7) 9% (3/34) 96% (44/46)
1990 Younis 111 40 (36) 8 (7) 15% (6/40) 100% (51/51)
1991 Mangano 60 22 (37) 3 (5) 5% (1/22) 95% (19/20)
1991 Strawn 68 n/a 4 (6) n/a 100% (21/21)
1991 Watters 26 15 (58) 3 (12) 20% (3/15) 100% (11/11)
1992 Hendel 327 167 (51) 28 (9) 14% (23/167) 99% (97/98)
1992 Lette 355 161 (45) 30 (8) 17% (28/161) 99% (160/162)
1992 Madsen 65 45 (69) 5 (8) 11% (5/45) 100% (20/20)
1993 Brown 231 77 (33) 12 (5) 13% (10/77) 99% (120/121)
1993 Kresowik 170 67 (39) 5 (3) 4% (3/67) 98% (64/65)
1994 Baron 457 160 (35) 22 (5) 4% (7/160) 96% (195/203)
1994 Bry 237 110 (46) 17 (7) 11% (12/110) 100% (97/97)
1995 Koutelou 106 47 (44) 3 (3) 6% (3/47) 100% (49/49)
1995 Marshall 117 55 (47) 12 (10) 16% (9/55) 97% (33/34)
1997 Van Damme 142 48 (34) 3 (2) n/a n/a
Nonvascular surgery
1990 Camp 40 9 (23) 6 (15) 67% (6/9) 100% (23/23)
1991 Iqbal 31 11 (41) 3 (11) 27% (3/11) 100% (20/20)
1992 Coley 100 36 (36) 4 (4) 8% (3/36) 98% (63/64)
1992 Shaw 60 28 (47) 6 (10) 21% (6/28) 100% (19/19)
1993 Takase 53 15 (28) 6 (11) 27% (4/15) 100% (32/32)
1994 Younis 161 50 (31) 15 (9) 18% (9/50) 98% (87/89)
1996 Stratmann 229 67 (29) 10 (4) 6% (4/67) 99% (91/92)
Weighted average 3718 246 (7) 12.1% 98.6%
(186/1397) (1549/1571) NPV, negative predictive value; PPV, positive predictive value.
Table 9b.7. Prognostic indicators in MPI Reversible perfusion defects
Extent Depth Transient LV dilation Fixed defects Increased lung uptake LVEF (gated SPECT)
MPI, myocardial perfusion imaging; LVEF, left ventricular ejection fraction.
Table 9b.8. Further investigation Resting LV function
Predicator of perioperative CHF, but not MI or ischemia and long-term mortality
High risk if LVEF <35%
Recommended for symptomatic CHF, prior CHF, or dyspnea of unknown origin
LV, left ventricular; LVEF, left ventricular ejection fraction; CHF, chronic heart failure.
to be predictors of long-term events with an accuracy similar to that of the inducible abnor- malities for the perioperative period.
5. Conclusions
1. Preoperative cardiac evaluation of patients undergoing surgery offers the possibility of reducing cardiac risk by treating myocardial
ischemia, hypertension, and hyperlipidemia.
This will reduce perioperative risk and improve long-term outcome.
2. Patients without predictors of cardiac events are at low risk even if undergoing inter- mediate- or high-risk surgery. Patients with one or more predictors (e.g., angina pectoris class I or II, previous MI, diabetes mellitus, compen- sated or prior congestive heart failure, important cardiac arrhythmias) who are undergoing low- or intermediate-risk surgery do not benefit from additional investigation (unless their functional capacity is poor), because the risk of periopera- tive events is low. However, both groups will benefit from beta-blockade.
3. Noninvasive imaging should further assess the perioperative risk in patients with multiple predictors undergoing high-risk surgery. MPS and dobutamine echocardiography have compa- rable accuracy and the choice of test should be that in which the center has the most experience.
Figure 9b.4. Abnormal DSE. A Rest echocardiography. B Low-dose stress echocardiography, i.e., 10mg/kg.C Peak stress echocardiography,i.e.,40 mg/kg.D Echocardiography at recovery. The white arrow indicates the abnormality. At rest
and also at a low dose, the contraction is normal whereas the wall is dyskinetic (moving outside instead of contracting) at peak stress.
Accurate assessment of the ischemic burden is helpful to predict perioperative risk but simulta- neous assessment of the LV function, by means of ECG gated SPECT in the case of MPS, could be helpful in the long-term evaluation of the cardiac risk.
4. Patients with mild to moderate inducible ischemia should be managed as they would be in the absence of peripheral vascular surgery, and they should receive beta-blockers before, during, and after surgery. In patients with extensive inducible ischemia, the cardioprotective effect of beta-blockers is probably insufficient and refer- ral to coronary angiography should be consid- ered.
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