Survival by Stroke Volume Index in Severe Aortic Stenosis
Survival by Stroke Volume Index in Severe Aortic Stenosis
Objective Low-gradient (LG) severe aortic stenosis (AS) and preserved EF with reduced stroke volume are associated with an adverse prognosis, but the relationship of stroke volume index (SVI) with mortality among a range of values is unknown. We investigated the prognostic impact of SVI in this population.
Methods We examined 405 consecutive patients with preserved EF (≥50%) and severe AS (valve area <1.0 cm) with LG (<40 mm Hg) using echocardiography. Patients were stratified into quartiles based on SVI distribution (group 1: <38 mL/m (n=90), group 2: 38–43 mL/m (n=105), group 3: 43–48 mL/m (n=104) and group 4: >48 mL/m (n=106)).
Results Groups 1 and 2 had poorer survival with medical management compared with 3 and 4 (3-year estimate 46% and 67% vs. 78% and 73%, respectively, p=0.002) although aortic valve replacement referral rate was similar (53%–62%, p=0.57). An inverse relationship was observed between SVI and mortality (HR 1.28 (1.11 to 1.46) per every 5 mL/m decrease in SVI). After multivariable analysis, SVI was the strongest predictor of mortality (HR 0.92 (0.89 to 0.95), p<0.0001). Using different SVI cutpoints, SVI <35 was associated with highest mortality (HR 2.36 (1.49 to 3.73), p<0.001), followed by SVI <38 (HR 2.09 (1.39 to 3.16), p<0.001) and by SVI <43 (HR 2.05 (1.38 to 3.05), p<0.001). Survival with SVI ≥43 was similar to age and sex-matched controls (3-year estimate 84%, p=0.24); survival for SVI <43 was significantly worse (3-year estimate 63%, p<0.001).
Conclusions Lower SVI is incrementally associated with mortality in LG severe AS with preserved EF. These findings have implications for classification of AS severity, identification of high-risk groups and subsequent management.
Low flow, low-gradient (LG) severe aortic stenosis (AS) with preserved EF is a recently described syndrome associated with reduced survival. The mechanism of low stroke volume (SV) has been attributed to reduced systemic arterial compliance (SAC), smaller LV cavity size due to concentric remodelling, restrictive physiology resulting in impaired LV filling and diminished LV systolic function despite preserved EF. In order to improve AS assessment and determine the optimal treatment strategy, a new flow-gradient classification has been proposed incorporating the mean aortic valve gradient along with normal vs. reduced stroke volume index (SVI). Studies have arbitrarily used a cutpoint of SVI <35 mL/m to define the low flow group; however, other cutpoints have not been investigated, and whether SVI has a graded relationship for predicting outcome in this group of patients is unknown. We have recently investigated the prevalence of flow-gradient patterns in severe AS with preserved EF at our own institution and found that SVI <35 mL/m is strongly predictive of poor outcome in patients with LG severe AS and preserved EF. We hypothesised that lower SVI may have a graded association with mortality and that such knowledge may improve risk prediction in this population. Accordingly, we investigated the prognostic impact of SVI among a range of values in a population of patients with LG severe AS with preserved EF.
Abstract and Introduction
Abstract
Objective Low-gradient (LG) severe aortic stenosis (AS) and preserved EF with reduced stroke volume are associated with an adverse prognosis, but the relationship of stroke volume index (SVI) with mortality among a range of values is unknown. We investigated the prognostic impact of SVI in this population.
Methods We examined 405 consecutive patients with preserved EF (≥50%) and severe AS (valve area <1.0 cm) with LG (<40 mm Hg) using echocardiography. Patients were stratified into quartiles based on SVI distribution (group 1: <38 mL/m (n=90), group 2: 38–43 mL/m (n=105), group 3: 43–48 mL/m (n=104) and group 4: >48 mL/m (n=106)).
Results Groups 1 and 2 had poorer survival with medical management compared with 3 and 4 (3-year estimate 46% and 67% vs. 78% and 73%, respectively, p=0.002) although aortic valve replacement referral rate was similar (53%–62%, p=0.57). An inverse relationship was observed between SVI and mortality (HR 1.28 (1.11 to 1.46) per every 5 mL/m decrease in SVI). After multivariable analysis, SVI was the strongest predictor of mortality (HR 0.92 (0.89 to 0.95), p<0.0001). Using different SVI cutpoints, SVI <35 was associated with highest mortality (HR 2.36 (1.49 to 3.73), p<0.001), followed by SVI <38 (HR 2.09 (1.39 to 3.16), p<0.001) and by SVI <43 (HR 2.05 (1.38 to 3.05), p<0.001). Survival with SVI ≥43 was similar to age and sex-matched controls (3-year estimate 84%, p=0.24); survival for SVI <43 was significantly worse (3-year estimate 63%, p<0.001).
Conclusions Lower SVI is incrementally associated with mortality in LG severe AS with preserved EF. These findings have implications for classification of AS severity, identification of high-risk groups and subsequent management.
Introduction
Low flow, low-gradient (LG) severe aortic stenosis (AS) with preserved EF is a recently described syndrome associated with reduced survival. The mechanism of low stroke volume (SV) has been attributed to reduced systemic arterial compliance (SAC), smaller LV cavity size due to concentric remodelling, restrictive physiology resulting in impaired LV filling and diminished LV systolic function despite preserved EF. In order to improve AS assessment and determine the optimal treatment strategy, a new flow-gradient classification has been proposed incorporating the mean aortic valve gradient along with normal vs. reduced stroke volume index (SVI). Studies have arbitrarily used a cutpoint of SVI <35 mL/m to define the low flow group; however, other cutpoints have not been investigated, and whether SVI has a graded relationship for predicting outcome in this group of patients is unknown. We have recently investigated the prevalence of flow-gradient patterns in severe AS with preserved EF at our own institution and found that SVI <35 mL/m is strongly predictive of poor outcome in patients with LG severe AS and preserved EF. We hypothesised that lower SVI may have a graded association with mortality and that such knowledge may improve risk prediction in this population. Accordingly, we investigated the prognostic impact of SVI among a range of values in a population of patients with LG severe AS with preserved EF.
