Response to Letter Regarding Article, “Flow-Gradient Patterns in Severe Aortic Stenosis With Preserved Ejection Fraction: Clinical Characteristics and Predictors of Survival”
We thank Dr Abergel and colleagues for their interest in our study.1 We completely agree that the careful measurement of peak aortic valve velocity in multiple imaging windows is necessary for the accurate classification of severity, and may in part explain the lower prevalence of low-gradient severe aortic stenosis in our study in comparison with previous reports.
Regarding the impact of obesity on the accurate assessment of aortic stenosis, for patients at extreme ends of the body mass index (BMI), it is possible that the use of variables corrected for BMI or body surface area may be suboptimal. To address this concept, we examined patients in our study with obesity (defined as BMI≥30 kg/m2) and low (<35 mL/m2) versus normal (≥35 mL/m2) stroke volume index. Although BMI was higher in the obese low-flow (LF) group (38±7 versus 35±5 kg/m2, P=0.002), stroke volume and stroke volume indexed for height and BMI were all considerably lower in the obese LF group (74±13 versus 95±14 mL, P<0.0001; 19±2 versus 28±5 mL/m, P<0.0001; 2.00±0.42 versus 2.76±0.50 mL·kg–1·m–2, P<0.0001, respectively). Thus, BMI is not the only contributor to the LF classification.
Furthermore, if there was significant misclassification because of obesity, clinical outcomes should have been less different between the LF/low-gradient (LG) group and others. In contrast, the LF/high-gradient group may have been more affected by obesity as evidenced by the markedly higher BMI in this group (35.6±7.5 mL/m2) and the better outcomes in comparison with LF/LG. We agree with Dr Abergel that extremes of BMI, which involved few patients in our study, should be taken into account when assessing patients clinically. Although stroke volume index is the primary definition used for the LF classification, it is imperfect as a cut point; for this reason, we also consider valvuloarterial impedance and systemic arterial compliance to refine our assessment (5.18±0.95 versus 3.98±0.68 mm Hg·mL–1·m–2, P<0.0001; and 0.66±0.21 versus 0.85±0.27 mL·mm Hg–1·m–2, P<0.0001 in obese LF versus obese normal-flow groups, respectively).
We found that patients with the LF/LG pattern had reduced survival in comparison with other groups, and LF/LG had unique characteristics including a higher prevalence of atrial fibrillation and previous heart failure events. Conversely, patients with normal flow/LG pattern had a favorable survival with medical management. Aortic valve replacement was associated with significantly improved survival in patients with LF/LG in contrast to normal-flow/LG, where the effect of aortic valve replacement was neutral. These data support the use of the current flow-gradient classification system for patients with aortic stenosis.
Mackram F. Eleid, MD
Paul Sorajja, MD
Hector I. Michelena, MD
Joseph F. Malouf, MD
Chrisopher G. Scott, MS
Patricia A. Pellikka, MD
Division of Cardiovascular Diseases and Internal Medicine
Mayo Clinic College of Medicine
- © 2014 American Heart Association, Inc.