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J Thorac Cardiovasc Surg 2008;136:1549-1557
© 2008 The American Association for Thoracic Surgery
Acquired Cardiovascular Disease |
a Division of Cardiovascular Diseases and Internal Medicine, Mayo Clinic, Rochester, Minn
b Section of Biostatistics, Mayo Clinic, Rochester, Minn
c Division of Cardiovascular Surgery, Mayo Clinic, Rochester, Minn
Received for publication March 21, 2008; revisions received June 10, 2008; accepted for publication July 22, 2008. * Address for reprints: Maurice Enriquez-Sarano, MD, Mayo Clinic, 200 First Street SW, Rochester, MN 55905. (Email: Sarano.maurice{at}mayo.edu).
| Abstract |
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Methods: We prospectively enrolled 287 patients with aortic regurgitation (age, 61 ± 17 years; 68% male) in whom we performed quantitative Doppler echocardiographic analysis and personal physicians conducted management.
Results: After diagnosis, 40 congestive heart failure episodes occurred under medical management (10-year, 23% ± 4%) causing high subsequent mortality (hazard ratio [HR], 2.8; 95% confidence interval [CI], 1.2–6.8; P = .02). Patients with traditional surgical markers (symptoms or ejection fraction <50%) were surprisingly followed 1.4 ± 3.3 years under medical management with frequent congestive heart failure (adjusted risk, 4.9; 95% CI, 2.1–11.0; P < .001) and excess postoperative mortality (HR, 3.0; 95% CI, 1.3–7.1; P = .01). Quantitative American Society of Echocardiography aortic regurgitation grading and left ventricular end-systolic volume index independently predicted congestive heart failure (quantitative American Society of Echocardiography severe aortic regurgitation: HR, 3.6; 95% CI, 1.3–13.0; P = .015; end-systolic volume index
45 mL/m2: HR, 2.1; 95% CI, 1.03–4.4; P = .04) or death–congestive heart failure with incremental predictive value (P < .001). Higher congestive heart failure rates occurred with quantitative American Society of Echocardiography severe aortic regurgitation (regurgitant volume of
60 mL/beat or orifice of
30 mm2) versus quantitative American Society of Echocardiography mild aortic regurgitation (10-year: 44% ± 10% vs 15% ± 7%, P < .001) and end-systolic volume index of 45 mL/m2 or greater versus less than 45 mL/m2 (33% ± 7% vs 9% ± 2%, P < .001). Traditional markers (symptoms and ejection fraction <50%) had lower sensitivity for congestive heart failure than quantitative echocardiography (all P < .001). Cardiac surgery for aortic regurgitation markedly reduced congestive heart failure in quantitative American Society of Echocardiography severe aortic regurgitation (HR, 0.23; 95% CI, 0.08–0.68; P = .008) without excess mortality (P = .10).
Conclusion: This prospective study of aortic regurgitation shows frequent congestive heart failure under conservative management. Traditional surgical markers (symptoms and ejection fraction <50%) predict subsequent congestive heart failure but are insensitive, and rescue operations are often delayed and associated with excess mortality. Quantitative echocardiography provides congestive heart failure predictors that are independent, incremental, and more sensitive than traditional markers. Cardiac surgery for aortic regurgitation markedly reduces congestive heart failure rates in high-risk patients with aortic regurgitation.
| Introduction |
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In clinical guidelines risk stratification in AR is essentially based on symptoms or reduced ventricular function.1,9
These traditional surgical markers play a central role because they are considered the strongest predictors of outcome.2
However, when surgical intervention is performed with these traditional markers, symptoms usually improve, but surgical series suggest that survival might remain suboptimal.10,11
These dubious outcomes warrant new risk-stratification tools to provide better outcomes.
Quantitative echocardiography codified by the American Society of Echocardiography (quantitative American Society of Echocardiography [QASE] grading)6
might play an important role in AR. For this purpose, we conducted a prospective study in patients with quantified AR and ventricular volumes using Doppler echocardiography. Pilot data from the asymptomatic segment of this study were encouraging by showing a link between these novel variables and the combined end point of cardiac events.12
However, clinically relevant issues are whether these quantitative echocardiographic variables specifically predict CHF occurrence and have an incremental role over symptoms and ejection fraction (EF) and whether these various types of predictors affect not only medical but also surgical outcome.13
Thus we hypothesized that CHF is frequent in AR treated medically and that quantitative echocardiography independently and incrementally (over symptoms and EF) predicts CHF and defines high-risk groups. We also hypothesized that surgical intervention for AR reduces the risk of CHF, with excellent survival in the quantitatively defined high-risk subsets.
| Materials and Methods |
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Clinical Evaluation and Management
Patients were evaluated and treated by their independent personal physicians who assessed symptoms, were informed of all results, and made all management decisions (without interference from investigators). Follow-up, collected after closure of enrollment and of all baseline data-collection procedures, was complete up to death or 2006 in 95% of patients and was less than 1 year in only 1.7% of patients. CHF ascertainment used Framingham criteria,15
and documentation of patients' clinical events was reviewed to assess these criteria. Symptoms alone were not sufficient for CHF diagnosis, and congestive manifestations were required. Comorbidity assessment used the Charlson index.16
Doppler Echocardiographic Analysis
Quantitation of AR
Comprehensive AR quantitation used 3 validated methods that were eventually averaged to calculate both regurgitant volume (RVol) and effective regurgitant orifice (ERO) area (85% of patients had 2 or 3 methods). These were quantitative Doppler scanning based on aortic and mitral stroke volume measurement,17,18
quantitative 2-dimensional echocardiography based on LV and mitral stroke volume,18,19
and a proximal isovelocity surface area method analyzing proximal flow convergence.20
QASE guidelines regarding AR grading6
define QASE severe AR as an RVol of 60 mL/beat or greater or an ERO area of 30 mm2 or greater, QASE mild AR as both an RVol of less than 30 mL/beat and an ERO area of less than 10 mm2, and QASE moderate AR as greater than mild criteria (RVol
30 mL/beat or ERO area
10 mm2) but not reaching QASE severe criteria. Color flow imaging jet width/LV outflow tract width ratio14
was also prospectively measured from parasternal long-axis views.6
LV assessment
LV end-diastolic and end-systolic volume indexes (ESVIs) and EF determined by using the Simpson disk method and LV mass were measured as recommended by the American Society of Echocardiography.19
LV diameters using M-mode echocardiography were measured as absolute values and normalized to body surface area.
Statistical Analysis
Data are presented as mean values ± standard deviations or percentages. Group comparisons used analysis of variance or the
2 test, as appropriate. The main outcome end point was CHF occurrence under medical management (censored at surgical intervention), and the entire follow-up after diagnosis was used to assess the effect of surgical intervention as a time-dependent variable. Survival after surgical intervention was also analyzed. A secondary end point was combined CHF or death event. Event rates (estimated ± standard error) with the Kaplan–Meier method were compared by using the log-rank test. Time to CHF (or CHF death) was analyzed by means of the Cox proportional hazard method, with calculation of risk ratio unadjusted and adjusted for age, sex, and comorbidity score. The main variables of interest in predicting CHF were baseline symptoms, EF, ESVI, and QASE AR grading.
| Results |
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Univariate baseline predictors of CHF under conservative management are listed in Table 1. Traditional surgical markers (symptoms and EF) were linked to CHF. Quantitative variables, ESVI (HR, 1.04; 95% CI, 1.02–1.05 [per milliliter per square meter]; P < .001), RVol (HR, 1.19; 95% CI, 1.10–1.29 [per 10 mL/beat]; P < .001), and ERO area (HR, 1.49; 95% CI, 1.25–1.72 [per 10 mm2]; P < .001) were also powerful univariate CHF predictors. Table 2 shows that AR quantitation predicted CHF (with or without adjustment) and that QASE severe versus QASE mild grading implied quadrupling of CHF risk. QASE moderate grading was not independently associated with CHF. Prediction of CHF by means of QASE grading was not affected by vasodilator therapy (P < .004). The other independent determinants of CHF adjusting for age, sex, and comorbidity were symptoms (P < .01) and LV dysfunction assessment based on either an EF of less than 50% (P < .001) or an ESVI of 45 mL/m2 or greater (P < .01).
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2 increment = 17, P < .001).
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For the combined end point of death–CHF (the endpoint of CHF or death) under conservative management (68 events), traditional surgical indicators (symptoms or EF <50%; HR, 2.9; 95% CI, 1.3–5.8; P = .01), ESVI of 45 mL/m2 or greater (HR, 1.9; 95% CI, 1.1–3.4; P = .02), and QASE severe AR (HR, 3.1; 95% CI, 1.4–7.3; P = .004) were independent predictors. Addition of quantitative echocardiographic variables provided incremental power (model
2 increment = 21, P < .001).
Predictive Value of Quantitative Versus Traditional CHF Markers
Yearly CHF rates and numbers of events are displayed for traditional indicators (symptoms and EF <50%) in Figure 3
and for newer quantitative parameters (QASE grade and ESVI
45 mL/m2) in Figure 4
. Patients with baseline symptoms (Figure 3) had high CHF yearly rates (43.2 vs 2.5 per 100 patient-years, P < .001), contrasting with small number of CHF events predicted (n = 5, 12.5% of CHF events). In contrast, QASE grading (Figure 4) shows less impressive difference in CHF rates (6.7 vs 2.0 vs 1.0 per 100 patient-years for QASE severe versus moderate versus mild AR, P < .001), but most CHF events are detected by QASE severe AR grading (n = 22, 55% of CHF events). Thus symptoms showed higher specificity (P < .001), and QASE grading showed higher sensitivity (P < .001). Similarly, an EF of less than 50% was associated with high CHF rates (20.7 vs 2.7 per 100 patient-years, P < .001) but detected only 15% of CHF episodes (Figure 3), whereas an ESVI of 45 mL/m2 or greater was associated with a less striking difference in CHF rates (8.5 vs 1.6 per 100 patient-years, P < .001) but detected most CHF episodes (52.5%, Figure 4). Thus an EF of less than 50% had higher specificity (P < .001), and an ESVI of 45 mL/m2 or greater had a higher sensitivity (P < .001). Patients with both QASE severe AR and an ESVI of 45 mL/m2 or greater incurred frequent CHF (48% ± 10% at 5 years and 69% ± 13% at 10 years or 14.4% per 100 patient-years) close to that of patients with symptoms or low EF.
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Cardiac Surgery and Clinical Outcome
A total of 106 patients underwent cardiac surgery for AR during follow-up for symptoms in 56 patients, LV dysfunction in 16 patients, aortic dilatation in 14 patients, endocarditis in 4 patients, and physician/patient preference in 16 patients. After surgical intervention for AR, 24 deaths were noted, with a 5-year survival of 83% ± 4%. Adjusting for age, sex, and comorbidity, symptoms or an EF of less than 50% at diagnosis was associated with excess postoperative mortality (HR, 3.0; 95% CI, 1.3–7.1; P = .01). Five-year postoperative survival was 63% ± 10% with traditional surgical markers at diagnosis versus 89% ± 4% without (P < .001). Conversely, a preoperative ESVI of 45 mL/m2 or greater (P = .09) or QASE severe AR (P = .10) was not independently associated with excess postoperative mortality.
During 710 patient-years after surgical intervention, 6 episodes of CHF occurred so that surgical intervention as a time-dependant variable (accounting for time to operation) decreased CHF risk for patients with QASE severe AR (linearized yearly rate of CHF = 6.7%, decreasing to 0.9%; HR, 0.23; 95% CI, 0.08–0.68; P = .008). Conversely, in patients with QASE moderate AR, there was no detectable CHF difference (P = .84). Adjusting for age, sex, symptoms, comorbidity, LV function, and QASE AR grading, surgical intervention for AR markedly reduced CHF (adjusted HR, 0.14; 95% CI, 0.05–0.41; P = .0003).
| Discussion |
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45 mL/m2) have distinctive clinical value as independent CHF predictors under medical management. Patients with QASE severe AR (RVol
60 mL/beat or ERO
30 mm2) incur CHF 3 to 6 times more frequently than with QASE mild AR, and QASE grading superseded traditional markers of severe AR (color jet assessment and LV diameters). Patients with ESVIs of 45 mL/m2 or greater incur doubling of CHF risk. Importantly, symptoms and EF of less than 50% are specific, with very high rates of subsequent CHF (>20 per 100 patient-years), but lack sensitivity. Conversely, QASE grading and an ESVI of 45 mL/m2 or greater are associated with less striking CHF rates (6-9 per 100 patient-years) but are more sensitive. In these high-risk quantitatively defined subsets, cardiac surgery markedly reduces CHF risk without excess postoperative mortality. Thus rescue operations in patients with traditional surgical markers (symptoms and EF <50%) should be emphasized but are not sufficient in view of the mediocre postoperative outcome of these patients. In contrast, quantitative echocardiographic indices allow restorative indications of surgical intervention for AR, which reduces CHF risk without excess mortality.
Rationale of the Study
In patients with isolated AR, CHF development has been insufficiently studied. Rates of CHF complicating AR are rarely mentioned,2
and most often composite end points were the main measures of outcome.3,4,22
Thus rates and predictors and effect on outcome of CHF are unclear.2-5
These differences might result from patient selection but also from differences in AR severity that might not have been uncovered by using the crude noninvasive AR assessment available at the time.2-5
Most importantly, AR management is essentially guided by traditional surgical markers (symptoms or low EF),1
and a strategy of symptom-guided management was emphasized as safe and most appropriate for patients with isolated AR.23
However, other studies raised concerns regarding outcome with this strategy, even after surgical correction.8,10
Thus doubts remain on the respective value of traditional surgical markers (symptoms or low EF) and emerging quantitative measures. Quantitative echocardiography6,19
measures absolute AR degree (RVol or ERO) and LV volumes and in our experience is useful in asymptomatic patients12
in contrast to the rudimentary methods previously available,1,9
but its predictive and management values, relative to symptoms and EF, are undefined.
CHF and AR
In this prospective study we observed that CHF occurs relatively frequently overall (5.2 per 100 patient-years)2
but with considerable differences between subsets of patients. Patients with QASE mild AR rarely incur CHF, whereas other subsets incur much higher rates. We found that baseline symptoms, LV characteristics, and quantified severity of AR independently predict CHF. Symptoms and an EF of less than 50% are known to influence outcome and are listed in current guidelines.1,9
However, the link to outcome is not sufficient, and it is essential to analyze sensitivity and specificity of CHF prediction in clinical practice. CHF in AR has been linked to reduced EF,24
and indeed, we also observe that an EF of less than 50% predicts high CHF rates. Reduced EF also predicts lower survival with medical management2
and is considered a strong indication of surgical intervention.1,9
Similarly, baseline symptoms, which are known to affect survival,2
are associated in our study with high CHF rates, despite improvement with medical treatment. However, outcome with these traditional surgical markers raises several concerns. First, despite existing guidelines,1,9
in routine clinical practice surgical intervention for patients with these traditional surgical markers is often delayed, leading to frequent CHF and excess mortality. Second, in agreement with previous surgical series,10,11,25
excess mortality follows operations performed for symptoms or reduced EF, which represent late indicators of rescue operations rather than restorative operations conducive to favorable postoperative outcomes.13
Third, symptoms and low EF are insufficient23
because they are insensitive and detect only a small minority of the CHF events to come. Therefore in view of the excess mortality after CHF and of the reduction of CHF risk by AR surgery, our data unquestionably show that additional predictors of outcome are needed to more sensitively predict CHF events and poor outcome.
Our results verify the hypotheses that quantitative echocardiography provides objective indices (quantitative AR grading and ESVI) that can alleviate the CHF burden in patients with AR. These measures independently predict CHF incrementally to symptoms and EF and with higher sensitivity. In high-risk patients examined by using quantitative measures, surgical intervention for AR is not associated with excess mortality (as it is for symptoms and low EF) and reduces the risk of CHF.
Although qualitative AR degree predicts CHF, it is superseded by quantitative grading, emphasizing the importance of the quantitative approach.6
Our prospective data show that QASE severe AR is the most sensitive CHF predictor, filling a demand unmet by other outcome predictors.13
Low CHF rates with QASE mild AR probably represent the background population CHF rate, which is inconsistently associated with low EF.26
In contrast to this background rate, QASE severe AR multiplies CHF risk between 3 and 6 times. LV volume measurements provide another important independent CHF predictor. End-systolic LV characteristics predict outcome under medical management2,4
and after surgical intervention.27
Importantly, ESVI supersedes LV diameters (even adjusted for body surface area) and is more sensitive than EF; that is, the measures currently in clinical guidelines1,2,27
and an ESVI of 45 mL/m2 or greater apply equally to men and women by normalizing to body size.21
Thus this prospective study contrasts value and complementarity of traditional surgical markers (symptoms and EF), specific and associated high CHF rates, and novel quantitative echocardiographic measures (QASE grading and ESVI), both sensitive and incremental. Because these markers carry different implications for postoperative outcome, they emphasize different clinical implications.
Clinical Implications
Patients with traditional surgical markers (symptoms or EF <50%) are at high and immediate risk of CHF or death, irrespective of apparent improvements with medical treatment, but disappointingly, surgical intervention is often delayed. Thus our study emphasizes the need for speedy rescue operations for patients with these ominous characteristics. In view of excess postoperative mortality in these patients, rescue operations should not be the preferred timing of surgical correction of AR.
Quantitative echocardiographic variables allow restorative surgical intervention without excess postoperative mortality and with CHF risk reduction. Quantitative AR grading predicts CHF independently of all other clinical characteristics incrementally to traditional surgical markers and supersedes qualitative AR grading. Hence quantitative AR assessment should be encouraged and generalized.6
Patients with both QASE severe AR and an ESVI of 45 mL/m2 or greater incur a progressive but high risk,12
particularly of CHF. These characteristics represent the optimal target for consideration of surgical correction of AR with low postoperative mortality and marked CHF reduction and thus with the potential to provide true restorative surgical intervention.
Subsets with isolated QASE severe AR or an ESVI of 45 mL/m2 or greater (but not both) or those with QASE moderate AR are at moderate CHF risk but might progress and should be monitored closely. Vasodilators for preventing AR progression are disputed,28,29
and there is no defined process to stabilize AR or LV function in such patients.
Limitation of the Study
The occurrence of CHF is complex and implies multiple pathways, and a causal link between AR and CHF is difficult to prove. Coronary artery disease and atrial fibrillation can contribute to CHF,30,31
but in the current study they were not independently predictive. Our scope was not to address all possible CHF contributors but to focus on AR-specific CHF prediction.26
The link between AR and CHF is supported by strong association of CHF rates with AR degree and by considerable CHF risk reduction after surgical intervention for AR.
Inclusion of baseline symptoms or an EF of less than 50% might be disputed in that guidelines recommend surgical intervention in such patients. However, our study shows that in clinical practice physicians inconsistently refer such patients to surgical intervention, with delays causing CHF events and death. Thus it is essential to emphasize the need for speedy rescue operations in such patients. The new observation that symptoms and EF are specific but insensitive in predicting CHF in comparison with objective measurements, such as QASE grading and ESVI, could only be revealed by means of inclusion, irrespective of symptoms or EF, of all patients prospectively examined.
| Conclusion |
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| Footnotes |
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| References |
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