The Prognostic Significance of Stroke Volume Index in Low Gradient Severe Aortic Stenosis - From the National Echo Database of Australia

Abstract

Introduction: Approximately 50% of patients with severe aortic stenosis (AS) in clinical practice present with ‘low-gradient’ haemodynamics. Stroke Volume Index (SVI) is a measure of left ventricular output, with ‘normal-flow’ considered as >35ml/m2. The association between SVI and prognosis in severe low-gradient AS (LGAS) in currently not well-understood.

Methods: We analysed the National Echo Database of Australia (NEDA) and identified 109,990 patients with sufficiently comprehensive echocardiographic data, linked to survival information. Of these, there were 1,699 with severe LGAS and preserved ejection fraction (EF) (≥50%) and 774 patients with severe LGAS and reduced EF. One- and three-year survival in each subgroup were assessed (during follow-up of 74 ± 43 months), according to SVI thresholds.

Results: In patients with preserved EF the mortality “threshold” was at SVI <30ml/m2; survival was worse for those with SVI <30ml/m2 relative to those with SVI >35ml/m2 (HR 1.80, 95% CI 1.32-2.47 and HR 1.38, 95% CI 1.12-1.70), while survival was similar between those with SVI 30-35ml/m2 and SVI >35ml/m2. In patients with reduced EF the mortality 'threshold' was 35ml/m2; survival was worse for both those with SVI <30ml/m2 and 30-35ml/m2 relative to those with SVI >35ml/m2 (HR 1.98, 95% CI 1.27-3.09 and HR 1.41, 95% CI 1.05-1.93 for SVI <30ml/m2 and HR 2.02, 95% CI 1.23-3.31 and HR 1.56, 95% CI 1.10-2.21 for SVI 30-35ml/m2).

Conclusion: The SVI prognostic threshold for short- to medium-term mortality in adults with severe LGAS is different for those with preserved LVEF (<30ml/m2) compared to those with reduced LVEF (<35ml/m2).

Note:

Funding Information: NEDA was originally established with funding support from Actelion Pharmaceuticals, Bayer Pharmaceuticals and GlaxoSmithKline. Both NEDA (#1055214) and Dr Stewart (#11358940) are supported by the National Health and Medical Research Council of Australia. NEDA has received grants from Edwards Lifesciences but they do not relate to the current manuscript.

Declaration of Interests: None to declare.

Ethics Approval Statement: This study was approved by the ethics committee at Sydney Local Health District.

Keywords: Aortic Stenosis, Low-Flow, Low-Gradient, Stroke Volume Index