Clinical significance of energy loss index in patients with low-gradient severe aortic stenosis and preserved ejection fraction

Abstract

Aims: We hypothesized that among patients with low-gradient severe aortic stenosis (AS) and preserved left ventricular ejection fraction (LVEF), reclassification of AS severity as moderate by pressure recovery adjusted indexed aortic valve area (AVAi) = energy loss index (ELI), may identify a subgroup of patients with a better outcome.

Methods and results: Three hundred and seventy-nine patients with low-gradient AS (defined by AVAi ≤ 0.6 cm2/m2 and mean aortic pressure gradient < 40 mmHg) and preserved LVEF ≥50% were studied. Reclassification as moderate AS by ELI was defined as AVAi ≤0.6 cm2/m2 but with an ELI >0.6 cm2/m2. Cardiac events [cardiac mortality and/or need for aortic valve replacement (AVR)] during follow-up were studied. One hundred and forty-eight patients (39%) were reclassified as moderate AS by ELI. Reclassification as moderate AS was independently associated with decreased body surface area, normal flow status, decreased left ventricular mass index, and left atrial volume index (all P < 0.05). After adjustment for variables of prognostic interest, reclassification as moderate AS by ELI was associated with a considerable reduction of risk of cardiac events {adjusted hazard ratio (HR) 0.49 [95% confidence interval (CI) 0.33-0.72]; P < 0.001}, need for AVR [adjusted HR 0.52 (95% CI 0.34-0.81); P = 0.004], and cardiac mortality [adjusted HR 0.46 (95% CI 0.22-0.98); P = 0.044].

Conclusion: In patients with low-gradient severe AS and preserved LVEF, calculation of ELI permits to reclassify almost 40% of patients as having moderate AS. These reclassified patients have a considerable reduction of the risk of cardiac events during follow-up. Calculation of ELI is useful for decision-making in patients with low-gradient severe AS and preserved ejection fraction.

Keywords: aortic stenosis; echocardiography; energy loss index; low gradient; outcome; pressure recovery.