Value of Quantitative Echocardiography in Aortic Regurgitation
Value of Quantitative Echocardiography in Aortic Regurgitation
Abstract & Commentary
By Michael H. Crawford, MD
Source: Detaint D, et al. Quantitative echocardiographic determinants of clinical outcome in asymptomatic patients with aortic regurgitation. J Am Coll Cardiol Img. 2008;1:1-11.
Certain asymptomatic patients with significant aortic regurgitation (AR) and preserved left ventricular (LV) function may be at high risk for mortality. Detaint and colleagues from the Mayo Clinic hypothesized that quantitation of the severity of AR by Doppler echo would predict outcomes in such patients. They enrolled 251 asymptomatic patients with isolated AR of at least mild severity by color flow Doppler inspection and an LV ejection fraction (EF) of 50% or more. They measured LV volumes by the 2-dimensional echo Simpson's rule method, normalized for body surface area. AR was quantitated by 3 methods, which were averaged to determine regurgitant volume (RV) and effective regurgitant orifice (ERO) area. AR was also graded by the color flow jet with in the parasternal long axis view. The patients were followed for an average of 8 years.
Results: Etiology of AR was largely degenerative, with some having bicuspid valve, dilated aortic annulus, rheumatic disease, and endocarditis. AR was mild in 18%, moderate in 43%, and severe in 37% at entry by quantitative echo Doppler. Jet width AR grade was mild in 18%, moderate in 74%, and severe in 8%. A majority of patients were on chronic vasodilator therapy. The five-year survival was 93% and 10-year was 78%. Valve replacement was done in 81 patients, mainly for symptoms or LV dysfunction. AR by color Doppler jet width was not related to survival. Quantitative measures of AR were associated with survival in a multivariable analysis as continuous variables or categorical variables (mild vs severe). End systolic volume index (ESVI) > 45 mL/m2 and surgery for AR was also predictive of outcomes. Severe AR patients who had surgery showed lower mortality rates after surgery, but moderate AR patients did not. Detaint et al concluded that quantitation of AR severity and ESVI predict clinical outcomes better than color flow jet width measures in asymptomatic patients with preserved LVEF. Patients graded as severe AR or with an ESVI > 45 mL/m2 should be considered for surgery.
Commentary
This is the lead article in the new journal JACC Imaging, and it highlights the importance of moving away from m-mode echo measures and color Doppler interpretations of the severity of AR for decision making. In this carefully done study, < 5% of the patients met LV m-mode EDD > 70mm criteria for surgery and < 2% met the LVESD > 55mm criteria, yet there was an observed 13% mortality over an average of 8 years. Also, 37% had severe AR by quantitative techniques, but severe AR was diagnosed by color flow Doppler in only 8% of the patients. Clearly, these older criteria for high-risk patients with severe AR are insensitive and should be abandoned.
The American Society of Echocardiography criteria for severe AR were employed in this study: RV > 60 mL beat and ERO > 30 mm2. These parameters are based upon Doppler measurement of aortic and mitral stroke volume to calculate regurgitant volume and proximal isovelocity surface area by color flow Doppler proximal convergence. These techniques are not as easy to perform as m-mode and color Doppler, but can be incorporated into the analysis of clinical echoes when necessary. Clearly, mild AR by inspection doesn't require this complexity of measurements, but moderate-to-severe AR does. In this study, RV and ERO were equally predictive, so one measure will suffice if the other is technically challenging. Every effort should be made to incorporate these measures into the capabilities of clinical echo labs.
Recommending surgery for asymptomatic patients is difficult, and a randomized trial will likely never be done. In this study, surgery lowered the predicted mortality significantly if severe AR or ESVI > 45mm/m2 was found. Patients meeting either of these criteria should be carefully followed and considered for surgery. If they meet both, a good case for surgery can be made. Patients with moderate AR or ESVI < 45mm/m2 did not seem to benefit from surgery. Of course, patients with symptoms or LVEF < 50% should still be considered for surgery because they are known to be at high risk.
Certain asymptomatic patients with significant aortic regurgitation (AR) and preserved left ventricular (LV) function may be at high risk for mortality.Subscribe Now for Access
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