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Decision to perform concomitant aortic valve replacement in patients undergoing coronary bypass surgery: current thinking
Cardiovascular Surgery
which also affect the accuracy of Doppler assessment of pressure drop. Doppler estimates AVG at the level of the valve whereas gradients obtained a few centimeters distal to the valve after pressure recovery has occurred are more meaningful for the circulation. Doppler gradients are liable to be incorrect in patients with high cardiac output and in those with small annuli and eccentric orifices. The latter two conditions occur frequently in older patients (⬎60years), especially if the stenosis is judged to be moderate. Asymptomatic AS in those undergoing CBS is seen most commonly in patients who are ⱖ60 years of age.
Focused Review
Decision to Perform Concomitant Aortic Valve Replacement in Patients Undergoing Coronary Bypass Surgery: Current Thinking Mahmoud Eslami, MD, Shahbudin H. Rahimtoola, MB, University of Southern California, Keck School of Medicine, Los Angeles, California
Peak Gradient Peak gradient by Doppler ultrasound measures velocity of blood flow in the earliest part of systolic ejection. In the normal heart, the dynamics of LV ejection are primarily inertial in character (not resistive) and the major phenomenon relating pressure and flow in the ascending aorta is that governing mass acceleration. If mass acceleration and thus, velocity of blood flow is increased, a systolic gradient in early systole can be documented in the normal heart, both in animals and in humans. Furthermore, these early systolic gradients can be markedly increased with inotropic stimulation in the normal heart both in experimental animals and in humans. Peak gradients calculated from Doppler recordings occur in early systole, which may thus not be related to valve stenosis or may be exaggerated by valve stenosis. Furthermore, in severe AS, the aortic valve opens slowly and is fully open in late systole, which is why on auscultation the aortic ejection systolic murmur peaks in late systole. However, Doppler peak gradient occurs earlier in systole, that is, at a time when the valve is not fully open and at a time which may not necessarily be associated with peak blood flow in AS. Therefore, it is better to measure mean AVG. In 636 patients studied by cardiac catheterization over a period of 10 years, no AVG (peak or mean) was found to be both sensitive and specific for severe AS. A mean gradient of ⬎50mm Hg or peak gradient of ⬎60 mm Hg were specific with 90% or more positive predictive value. However, it was not possible to find a lower limit with 90% negative predictive value. The authors emphasized the importance of measuring AVA with cardiac catheterization in all patients with suspicion of severe AS even when the mean AVG ⬍50 mm Hg (present in 50% of patients in their study) and/or the peak gradient was ⬍60mm Hg (present in 47% of patients in their study). At cardiac catheterization peak gradient is measured at time of peak aortic systolic pressure, that is, at a time when the valve is fully open.
As the population ages, an increasing number of individuals are diagnosed with coronary artery disease (CAD) who need to undergo coronary bypass surgery (CABG) and who have co-incidental asymptomatic calcific aortic stenosis (AS). Thus, the important clinical question, which is addressed in this article, is: which patients undergoing CBS who have asymptomatic AS should also have aortic valve replacement (AVR) at the time of initial CBS?
Assessment of Severity of Aortic Valve Stenosis Aortic Valve Gradient Aortic valve gradient (AVG) is related to flow across the aortic valve, that is, stroke volume (the gradient is a per beat, not per minute, function) and systolic ejection time, both of which are a function of heart rate, left ventricular (LV) preload, afterload and myocardial contractility. AVG is also dependent on distal obstruction represented by systemic vascular resistance and thus on the pressure in ascending aorta. Since all these parameters can change rapidly, AVGs may also change from one time to another, in minutes to months, regardless of the method of measurement. Doppler ultrasound can be used to measure AVG. However, one should keep in mind that AVG measured by Doppler has limitations. Feigenbaum has stated that “none of the echocardiographic techniques measures intravascular pressures directly.” The formula used for AVG is ⌬P ⫽ 4v2, which is the simplification of Bernoulli equation (Equation 1):
R (V) p22DV/DT DS ⁄ p(V22) Flow Viscous Convective ⫹ ⫹ P1 ⫺ P 2 ⫽ Acceleration Friction Acceleration 12
Several assumptions are made to calculate the valve gradient by Doppler ultrasound using the modified Bernoulli equation. These include: a) eliminating flow acceleration and viscous friction factors; b) ignoring the proximal velocity and c) ignoring energy losses, nonuniform velocity profiles, unsteady flow and omission of upstream velocity,
Aortic Valve Area The severity of aortic stenosis is best determined by measuring the aortic valve area (AVA). The criteria for grading the severity of AS is:
ACC CURRENT JOURNAL REVIEW Nov/Dec 2001 © 2001 by the American College of Cardiology Published by Elsevier Science Inc.
84
1062-1458/01/$20.00 PII S1062-1458(01)00443-3
Aortic Stenosis
AVA (cm2)
AVA index (cm2/m2)
Mild Moderate Severe
⬎1.5 ⬎1.0 to 1.5 ⱕ1.0
⬎0.9 ⬎0.6 to 0.9 ⱕ0.6
Table 1. Operative Mortality Years
AVA can be calculated from data obtained by cardiac catheterization and by Doppler echocardiography. Both of these methods use pressure gradient across the aortic valve to calculate AVA. By cardiac catheterization the actual stroke volume is used in the calculation of AVA, thus, accounting for the variable of changes in flow affecting the gradient. Calculation of AVA by Doppler echocardiography requires measurement of the diameter of the left ventricular outflow tract. Difficulty in obtaining its accurate measurement is known to result in an erroneously low calculated AVA in a significant percent of patients.
6.
1972–97 1994–97
1,690 345 365 32,538
7.9 10.6 6.0 6.8
⬍80 years ⱖ80 years
In one study on the natural history of mild AS (AVA ⬎1.5 cm2), by 10 years 8% of patients had developed severe AS. Another study showed an event rate (which includes AVR plus mortality before and after AVR) of 15%. Thus it is likely that ⱕ12% of survivors who initially would not have AVR for mild AS will develop severe AS. Even if one assumes that the operative mortality of late AVR in these patients may be up to 15% (a high mortality in the current era), the total number of deaths from late AVR will be very small. Moreover, at the end of 5 and 10 years, only 5% and 9% respectively will need AVR. One would estimate that to reduce one death from late AVR by a policy of AVR for mild AS at the time of initial CABG in 100 patients, by 10 years the cumulative incidence of unnecessary AVR would be 91 and that of excess death would be 29 (Figure 1 and Table 3). The incidence of re-operation and mortality associated with re-operation are
Several factors have to be taken into account when considering prophylactic AVR for mild-to-moderate AS in patients undergoing CABG. These include:
5.
Cohn et al. Edward et al.
2.1 2.9 3.0 8.1
Mild Aortic Stenosis (AVA >1.5 cm2; >0.9 cm2/m2)
Mild-to-Moderate Aortic Stenosis
4.
1994–97
⬍80 years ⱖ80 years
7,026 8,213 60,161 4,306
Determining the need for prophylactic AVR in patients who initially have mild or moderate AS depends on two issues: 1) the patient outcomes previously outlined and 2) the proportion of patients with mild or moderate AS who will develop severe AS and their subsequent outcomes.
If AS is severe, prophylactic AVR should be performed at the time of CABG. This is a Class I recommendation in the ACC/AHA guidelines.
3.
CABG ⫹ AVR Alexander et al.
Operative Mortality (%)
dence of prosthesis-related complications is approximately 2-6% per year. This is an important consideration, which should always be remembered.
Severe Aortic Stenosis (AVA <1.0 cm2; <0.6 cm2/m2)
2.
1974–88 1974–79 1994–97
Number of Patients
AVR, aortic valve replacement; CABG, coronary bypass surgery. Reproduced with permission and additions from Rahimtoola SH: Heart 2001;85:337– 41.
Reduced LV ejection fraction Patients with reduced LV ejection fraction (LVEF) (ⱕ0.35) and low mean AVG may have severe AS and frequently also have underlying CAD. The diagnosis of severe AS in this group of patients may pose a difficult problem. Such patients require a complete physical examination, ECG, chest x-ray, echocardiographic/Doppler studies and thorough, careful hemodynamic evaluation and analysis of data at the time of cardiac catheterization. In a patient with borderline severe AS it is important to measure pressure (LV as well as ascending aorta) as well as cardiac output simultaneously.
1.
CABG Rahimtoola et al. Davis et al. Alexander et al.
Age
The operative mortality for AVR⫹CABG is two to three times that for isolated CABG (7-8% vs. 2.5-3%) (Table 1). The 10-year mortality of AVR⫹CABG is twice that for isolated CABG (60% vs. 30%) (Table 2). In patients who initially undergo isolated CABG the proportion of surviving patients who will actually develop severe AS by 5–10 years is small. Although the operative mortality for late AVR after initial CABG is higher, it is not prohibitive. At 10 years, approximately 16% of patients will need repeat revascularization for graft disease, graft occlusion and progression of coronary artery disease in those who initially had isolated CABG and also in those who initially had CABG⫹AVR. Of those initially undergoing CABG⫹AVR, the inci-
Table 2. 10-Year Mortality Years
Mean Age (years)
Number of Patients
10-year Mortality (%)
CABG Rahimtoola et al. Davis et al.
1974–88 1974–79
61 56
7,026 8,231 (15,239)
26 33 (30)
CABG ⫹ AVR Cohn et al. Peterseim et al.
1972–97 1994–97
69 63
365 347 (712)
55 65 (60)
Reproduced with permission from Rahimtoola SH: Heart 2001;85:337– 41.
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Figure 1. 10-year projected patient outcomes in 100 patients with severe coronary artery disease and mild AS undergoing CABG ⫹ AVR vs. initial CABG and later AVR if necessary. Upper curve shows the incidence of unnecessary AVR and the lower two curves the expected mortality. Reproduced from Rahimtoola SH: Heart 2001;85:337-341 by permission.
included in Figure 1 and Table 3. These estimates suggest that patients with mild AS at time of initial CABG should NOT have AVR at that time.
AS death and AVR in this study was 10% per year; however, one should note that many of these patients in fact initially had severe AS, that is AVA ⱕ1.0 cm2. Progression of AS is non-linear. Whether it is more rapid in older patients and in those with calcific AS is controversial because of conflicting data. This unpredictability in progression of the severity of AS makes it difficult to exactly determine the rate of progression. One would estimate that to reduce six deaths from late AVR by a policy of AVR for moderate AS at the time of initial CABG in 100 patients, by 10 years the cumulative incidence of unnecessary AVR would be 54 and that of excess deaths would be 24 (Figure 2; Table 3). The incidence of reoperation and mortality associated with re-operation (as-
Moderate Aortic Stenosis (AVA >1.0 to 1.5 cm2/ >0.6 to 0.9 cm2/m2) The natural history of moderate AS is not as well defined. One study provided information only on event-free survival, which was 100% at the end of 3 years and 35% at the end of 10 years, making the event-free survival at 5 years about 81%. The event-free survival in this study included AVR plus mortality before and after AVR; the need for late AVR was not given separately. In another study, moderate AS was classified as an AVA of 0.7-1.2 cm2. The incidence of Table 3. Results After 10 Years of a Policy of Initial CABG ⫹ AVR for Mild and Moderate Aortic Stenosis Severe CAD and Mild AS: 100 Patients To eliminate: Late AVR Death from late AVR* Results in: Unnecessary AVR Excess death
Table 4. Conclusions
Severe CAD and Moderate AS: 100 Patients
9 2
46 7
91 29
54 24
Conditions
AVR at Time of CABG
1. Severe AS 2. Mild AS 3. Moderate AS* Age ⬍60 years Age ⱖ60 years AVA⬎1.0–1.2 cm2 (⬎0.6–ⱕ0.7 cm2/m2) Bioprosthesis† AVA 1.3 cm2 (⬎0.7–⬍0.8 cm2/m2) AVAⱖ1.4–1.5 cm2 (ⱖ0.8–0.9 cm2/m2)
Yes No
†
* Based on 15% operative mortality, which is much higher than expected mortality. AS, aortic stenosis; CAD, coronary artery disease; CABG, coronary bypass surgery. Reproduced with permission from Rahimtoola SH: Heart 2001;85: 337– 41.
No Yes Uncertain No
Patient to receive a bioprosthetic valve. In patients with severe CAD, LVEF #0.35 and low mean AVG, care should be taken to ensure severe AS is not being missed. * More prospective studies are needed on outcomes in patients with AS diagnosed by calculation of AVA.
ACC CURRENT JOURNAL REVIEW Nov/Dec 2001
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Figure 2. 10-year projected patient outcomes in 100 patients with severe coronary artery disease and moderate AS undergoing CABG ⫹ AVR vs. initial CABG and alter AVR if necessary. Upper curve shows the incidence of unnecessary AVR and the lower two curves the expected mortality. Reproduced with permission from Rahimtoola SH: Heart 2001;85:337-341.
Bonow RO, Carabello B, et al. ACC/AHA guidelines for the management of patients with valvular heart disease. J Am Coll Cardiol 1998;32:1486 – 8. Beauchesne LM, Chan KL, et al. Temporal variations in effective orifice area during ejection: relationship to hemodynamic severity in patients with valvular aortic stenosis [abstract]. J Am Coll Cardiol 2000;535A. Edwards FH, Peterson ED, et al. Prediction of operative mortality after valve replacement surgery. J Am Coll Cardiol 2001;37: 885–92. Hammermeister KE, Sethi GK et al. Outcomes 15 years after valve replacement with a mechanical versus a bioprosthetic valve; final report of the VA randomized trial. J am Coll Cardiol 2000;36:1152– 8. Turina J, Hess O, et al. Spontaneous course of aortic valve disease. Eur Heart J. 1987;8:471– 83. Horstkotte D, Loogen F, et al. The natural history of aortic valve disease. Eur Heart J 1988;9(suppl E):57– 64. Kennedy KD, Nishimura RA, et al. Natural history of moderate aortic stenosis. J Am Coll Cardiol 1991;17:313–9.
sumed to be 15% which is too high) are included in Figure 2 and Table 3. Therefore, a uniform policy of initial CABG for severe CAD plus AVR in all patients with moderate AS cannot be supported at this time. However, there may be a subgroup of patients with moderate AS who may benefit from a policy of CABG ⫹ AVR at the time of initial surgery. These are older patients (ⱖ60 – 65 years) with calcific AS whose AVA ranges between ⬎1.0 cm2 to 1.2 cm2 (see Table 4 for details) because the possibility remains that the rate of progression of AS in this subgroup may be much higher. Therefore, until more data are available on the rate of progression of AS based on determination of AVAs, it is not unreasonable to consider CABG ⫹ AVR in this subgroup of patients provided that they can receive a bioprosthetic valve and thus, would not need anticoagulant therapy. Suggested Reading Rahimtoola SH. “Prophylactic” valve replacement for mild aortic valve disease at time of surgery for other cardiovascular disease?. J Am Coll Cardiol 1999;33:2009 –15. Rahimtoola SH. Should patients with asymptomatic mild or moderate aortic stenosis undergoing coronary artery bypass surgery also have valve replacement for their aortic stenosis? Heart 2001;85:337– 41.
Address correspondence and reprint requests to Shahbudin H. Rahimtoola, MD, Distinguished Professor, University of Southern California, 2025 Zonal Avenue, Los Angeles, CA 90033.
ACC CURRENT JOURNAL REVIEW Nov/Dec 2001
87
which also affect the accuracy of Doppler assessment of pressure drop. Doppler estimates AVG at the level of the valve whereas gradients obtained a few centimeters distal to the valve after pressure recovery has occurred are more meaningful for the circulation. Doppler gradients are liable to be incorrect in patients with high cardiac output and in those with small annuli and eccentric orifices. The latter two conditions occur frequently in older patients (⬎60years), especially if the stenosis is judged to be moderate. Asymptomatic AS in those undergoing CBS is seen most commonly in patients who are ⱖ60 years of age.
Focused Review
Decision to Perform Concomitant Aortic Valve Replacement in Patients Undergoing Coronary Bypass Surgery: Current Thinking Mahmoud Eslami, MD, Shahbudin H. Rahimtoola, MB, University of Southern California, Keck School of Medicine, Los Angeles, California
Peak Gradient Peak gradient by Doppler ultrasound measures velocity of blood flow in the earliest part of systolic ejection. In the normal heart, the dynamics of LV ejection are primarily inertial in character (not resistive) and the major phenomenon relating pressure and flow in the ascending aorta is that governing mass acceleration. If mass acceleration and thus, velocity of blood flow is increased, a systolic gradient in early systole can be documented in the normal heart, both in animals and in humans. Furthermore, these early systolic gradients can be markedly increased with inotropic stimulation in the normal heart both in experimental animals and in humans. Peak gradients calculated from Doppler recordings occur in early systole, which may thus not be related to valve stenosis or may be exaggerated by valve stenosis. Furthermore, in severe AS, the aortic valve opens slowly and is fully open in late systole, which is why on auscultation the aortic ejection systolic murmur peaks in late systole. However, Doppler peak gradient occurs earlier in systole, that is, at a time when the valve is not fully open and at a time which may not necessarily be associated with peak blood flow in AS. Therefore, it is better to measure mean AVG. In 636 patients studied by cardiac catheterization over a period of 10 years, no AVG (peak or mean) was found to be both sensitive and specific for severe AS. A mean gradient of ⬎50mm Hg or peak gradient of ⬎60 mm Hg were specific with 90% or more positive predictive value. However, it was not possible to find a lower limit with 90% negative predictive value. The authors emphasized the importance of measuring AVA with cardiac catheterization in all patients with suspicion of severe AS even when the mean AVG ⬍50 mm Hg (present in 50% of patients in their study) and/or the peak gradient was ⬍60mm Hg (present in 47% of patients in their study). At cardiac catheterization peak gradient is measured at time of peak aortic systolic pressure, that is, at a time when the valve is fully open.
As the population ages, an increasing number of individuals are diagnosed with coronary artery disease (CAD) who need to undergo coronary bypass surgery (CABG) and who have co-incidental asymptomatic calcific aortic stenosis (AS). Thus, the important clinical question, which is addressed in this article, is: which patients undergoing CBS who have asymptomatic AS should also have aortic valve replacement (AVR) at the time of initial CBS?
Assessment of Severity of Aortic Valve Stenosis Aortic Valve Gradient Aortic valve gradient (AVG) is related to flow across the aortic valve, that is, stroke volume (the gradient is a per beat, not per minute, function) and systolic ejection time, both of which are a function of heart rate, left ventricular (LV) preload, afterload and myocardial contractility. AVG is also dependent on distal obstruction represented by systemic vascular resistance and thus on the pressure in ascending aorta. Since all these parameters can change rapidly, AVGs may also change from one time to another, in minutes to months, regardless of the method of measurement. Doppler ultrasound can be used to measure AVG. However, one should keep in mind that AVG measured by Doppler has limitations. Feigenbaum has stated that “none of the echocardiographic techniques measures intravascular pressures directly.” The formula used for AVG is ⌬P ⫽ 4v2, which is the simplification of Bernoulli equation (Equation 1):
R (V) p22DV/DT DS ⁄ p(V22) Flow Viscous Convective ⫹ ⫹ P1 ⫺ P 2 ⫽ Acceleration Friction Acceleration 12
Several assumptions are made to calculate the valve gradient by Doppler ultrasound using the modified Bernoulli equation. These include: a) eliminating flow acceleration and viscous friction factors; b) ignoring the proximal velocity and c) ignoring energy losses, nonuniform velocity profiles, unsteady flow and omission of upstream velocity,
Aortic Valve Area The severity of aortic stenosis is best determined by measuring the aortic valve area (AVA). The criteria for grading the severity of AS is:
ACC CURRENT JOURNAL REVIEW Nov/Dec 2001 © 2001 by the American College of Cardiology Published by Elsevier Science Inc.
84
1062-1458/01/$20.00 PII S1062-1458(01)00443-3
Aortic Stenosis
AVA (cm2)
AVA index (cm2/m2)
Mild Moderate Severe
⬎1.5 ⬎1.0 to 1.5 ⱕ1.0
⬎0.9 ⬎0.6 to 0.9 ⱕ0.6
Table 1. Operative Mortality Years
AVA can be calculated from data obtained by cardiac catheterization and by Doppler echocardiography. Both of these methods use pressure gradient across the aortic valve to calculate AVA. By cardiac catheterization the actual stroke volume is used in the calculation of AVA, thus, accounting for the variable of changes in flow affecting the gradient. Calculation of AVA by Doppler echocardiography requires measurement of the diameter of the left ventricular outflow tract. Difficulty in obtaining its accurate measurement is known to result in an erroneously low calculated AVA in a significant percent of patients.
6.
1972–97 1994–97
1,690 345 365 32,538
7.9 10.6 6.0 6.8
⬍80 years ⱖ80 years
In one study on the natural history of mild AS (AVA ⬎1.5 cm2), by 10 years 8% of patients had developed severe AS. Another study showed an event rate (which includes AVR plus mortality before and after AVR) of 15%. Thus it is likely that ⱕ12% of survivors who initially would not have AVR for mild AS will develop severe AS. Even if one assumes that the operative mortality of late AVR in these patients may be up to 15% (a high mortality in the current era), the total number of deaths from late AVR will be very small. Moreover, at the end of 5 and 10 years, only 5% and 9% respectively will need AVR. One would estimate that to reduce one death from late AVR by a policy of AVR for mild AS at the time of initial CABG in 100 patients, by 10 years the cumulative incidence of unnecessary AVR would be 91 and that of excess death would be 29 (Figure 1 and Table 3). The incidence of re-operation and mortality associated with re-operation are
Several factors have to be taken into account when considering prophylactic AVR for mild-to-moderate AS in patients undergoing CABG. These include:
5.
Cohn et al. Edward et al.
2.1 2.9 3.0 8.1
Mild Aortic Stenosis (AVA >1.5 cm2; >0.9 cm2/m2)
Mild-to-Moderate Aortic Stenosis
4.
1994–97
⬍80 years ⱖ80 years
7,026 8,213 60,161 4,306
Determining the need for prophylactic AVR in patients who initially have mild or moderate AS depends on two issues: 1) the patient outcomes previously outlined and 2) the proportion of patients with mild or moderate AS who will develop severe AS and their subsequent outcomes.
If AS is severe, prophylactic AVR should be performed at the time of CABG. This is a Class I recommendation in the ACC/AHA guidelines.
3.
CABG ⫹ AVR Alexander et al.
Operative Mortality (%)
dence of prosthesis-related complications is approximately 2-6% per year. This is an important consideration, which should always be remembered.
Severe Aortic Stenosis (AVA <1.0 cm2; <0.6 cm2/m2)
2.
1974–88 1974–79 1994–97
Number of Patients
AVR, aortic valve replacement; CABG, coronary bypass surgery. Reproduced with permission and additions from Rahimtoola SH: Heart 2001;85:337– 41.
Reduced LV ejection fraction Patients with reduced LV ejection fraction (LVEF) (ⱕ0.35) and low mean AVG may have severe AS and frequently also have underlying CAD. The diagnosis of severe AS in this group of patients may pose a difficult problem. Such patients require a complete physical examination, ECG, chest x-ray, echocardiographic/Doppler studies and thorough, careful hemodynamic evaluation and analysis of data at the time of cardiac catheterization. In a patient with borderline severe AS it is important to measure pressure (LV as well as ascending aorta) as well as cardiac output simultaneously.
1.
CABG Rahimtoola et al. Davis et al. Alexander et al.
Age
The operative mortality for AVR⫹CABG is two to three times that for isolated CABG (7-8% vs. 2.5-3%) (Table 1). The 10-year mortality of AVR⫹CABG is twice that for isolated CABG (60% vs. 30%) (Table 2). In patients who initially undergo isolated CABG the proportion of surviving patients who will actually develop severe AS by 5–10 years is small. Although the operative mortality for late AVR after initial CABG is higher, it is not prohibitive. At 10 years, approximately 16% of patients will need repeat revascularization for graft disease, graft occlusion and progression of coronary artery disease in those who initially had isolated CABG and also in those who initially had CABG⫹AVR. Of those initially undergoing CABG⫹AVR, the inci-
Table 2. 10-Year Mortality Years
Mean Age (years)
Number of Patients
10-year Mortality (%)
CABG Rahimtoola et al. Davis et al.
1974–88 1974–79
61 56
7,026 8,231 (15,239)
26 33 (30)
CABG ⫹ AVR Cohn et al. Peterseim et al.
1972–97 1994–97
69 63
365 347 (712)
55 65 (60)
Reproduced with permission from Rahimtoola SH: Heart 2001;85:337– 41.
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85
Figure 1. 10-year projected patient outcomes in 100 patients with severe coronary artery disease and mild AS undergoing CABG ⫹ AVR vs. initial CABG and later AVR if necessary. Upper curve shows the incidence of unnecessary AVR and the lower two curves the expected mortality. Reproduced from Rahimtoola SH: Heart 2001;85:337-341 by permission.
included in Figure 1 and Table 3. These estimates suggest that patients with mild AS at time of initial CABG should NOT have AVR at that time.
AS death and AVR in this study was 10% per year; however, one should note that many of these patients in fact initially had severe AS, that is AVA ⱕ1.0 cm2. Progression of AS is non-linear. Whether it is more rapid in older patients and in those with calcific AS is controversial because of conflicting data. This unpredictability in progression of the severity of AS makes it difficult to exactly determine the rate of progression. One would estimate that to reduce six deaths from late AVR by a policy of AVR for moderate AS at the time of initial CABG in 100 patients, by 10 years the cumulative incidence of unnecessary AVR would be 54 and that of excess deaths would be 24 (Figure 2; Table 3). The incidence of reoperation and mortality associated with re-operation (as-
Moderate Aortic Stenosis (AVA >1.0 to 1.5 cm2/ >0.6 to 0.9 cm2/m2) The natural history of moderate AS is not as well defined. One study provided information only on event-free survival, which was 100% at the end of 3 years and 35% at the end of 10 years, making the event-free survival at 5 years about 81%. The event-free survival in this study included AVR plus mortality before and after AVR; the need for late AVR was not given separately. In another study, moderate AS was classified as an AVA of 0.7-1.2 cm2. The incidence of Table 3. Results After 10 Years of a Policy of Initial CABG ⫹ AVR for Mild and Moderate Aortic Stenosis Severe CAD and Mild AS: 100 Patients To eliminate: Late AVR Death from late AVR* Results in: Unnecessary AVR Excess death
Table 4. Conclusions
Severe CAD and Moderate AS: 100 Patients
9 2
46 7
91 29
54 24
Conditions
AVR at Time of CABG
1. Severe AS 2. Mild AS 3. Moderate AS* Age ⬍60 years Age ⱖ60 years AVA⬎1.0–1.2 cm2 (⬎0.6–ⱕ0.7 cm2/m2) Bioprosthesis† AVA 1.3 cm2 (⬎0.7–⬍0.8 cm2/m2) AVAⱖ1.4–1.5 cm2 (ⱖ0.8–0.9 cm2/m2)
Yes No
†
* Based on 15% operative mortality, which is much higher than expected mortality. AS, aortic stenosis; CAD, coronary artery disease; CABG, coronary bypass surgery. Reproduced with permission from Rahimtoola SH: Heart 2001;85: 337– 41.
No Yes Uncertain No
Patient to receive a bioprosthetic valve. In patients with severe CAD, LVEF #0.35 and low mean AVG, care should be taken to ensure severe AS is not being missed. * More prospective studies are needed on outcomes in patients with AS diagnosed by calculation of AVA.
ACC CURRENT JOURNAL REVIEW Nov/Dec 2001
86
Figure 2. 10-year projected patient outcomes in 100 patients with severe coronary artery disease and moderate AS undergoing CABG ⫹ AVR vs. initial CABG and alter AVR if necessary. Upper curve shows the incidence of unnecessary AVR and the lower two curves the expected mortality. Reproduced with permission from Rahimtoola SH: Heart 2001;85:337-341.
Bonow RO, Carabello B, et al. ACC/AHA guidelines for the management of patients with valvular heart disease. J Am Coll Cardiol 1998;32:1486 – 8. Beauchesne LM, Chan KL, et al. Temporal variations in effective orifice area during ejection: relationship to hemodynamic severity in patients with valvular aortic stenosis [abstract]. J Am Coll Cardiol 2000;535A. Edwards FH, Peterson ED, et al. Prediction of operative mortality after valve replacement surgery. J Am Coll Cardiol 2001;37: 885–92. Hammermeister KE, Sethi GK et al. Outcomes 15 years after valve replacement with a mechanical versus a bioprosthetic valve; final report of the VA randomized trial. J am Coll Cardiol 2000;36:1152– 8. Turina J, Hess O, et al. Spontaneous course of aortic valve disease. Eur Heart J. 1987;8:471– 83. Horstkotte D, Loogen F, et al. The natural history of aortic valve disease. Eur Heart J 1988;9(suppl E):57– 64. Kennedy KD, Nishimura RA, et al. Natural history of moderate aortic stenosis. J Am Coll Cardiol 1991;17:313–9.
sumed to be 15% which is too high) are included in Figure 2 and Table 3. Therefore, a uniform policy of initial CABG for severe CAD plus AVR in all patients with moderate AS cannot be supported at this time. However, there may be a subgroup of patients with moderate AS who may benefit from a policy of CABG ⫹ AVR at the time of initial surgery. These are older patients (ⱖ60 – 65 years) with calcific AS whose AVA ranges between ⬎1.0 cm2 to 1.2 cm2 (see Table 4 for details) because the possibility remains that the rate of progression of AS in this subgroup may be much higher. Therefore, until more data are available on the rate of progression of AS based on determination of AVAs, it is not unreasonable to consider CABG ⫹ AVR in this subgroup of patients provided that they can receive a bioprosthetic valve and thus, would not need anticoagulant therapy. Suggested Reading Rahimtoola SH. “Prophylactic” valve replacement for mild aortic valve disease at time of surgery for other cardiovascular disease?. J Am Coll Cardiol 1999;33:2009 –15. Rahimtoola SH. Should patients with asymptomatic mild or moderate aortic stenosis undergoing coronary artery bypass surgery also have valve replacement for their aortic stenosis? Heart 2001;85:337– 41.
Address correspondence and reprint requests to Shahbudin H. Rahimtoola, MD, Distinguished Professor, University of Southern California, 2025 Zonal Avenue, Los Angeles, CA 90033.
ACC CURRENT JOURNAL REVIEW Nov/Dec 2001
87