The paradox of surgical management of patients with low-flow, low-gradient aortic stenosis

Abstract

See related article on pages 1558-66.In this issue of the Journal, Parikh and colleagues 1 elegantly analyze the institutional outcomes of aortic valve replacement (AVR) at the Cleveland Clinic to illustrate the potential impact of low-flow, low-gradient aortic stenosis (LFLGAS) on 5-year post-AVR mortality. Despite quite acceptable initial operative outcomes, a fifth of their 875 consecutive patients who underwent surgical AVR for severe stenosis during a 2-year period were dead at 5 years. Preoperative left ventricular stroke volume index (LVSVI) was used to identify both LFLGAS with low ejection fraction (EF) and paradoxic LFLGAS with an EF of 50% or greater. It was determined that either variant of LFLGAS independently predicted early mortality.The natural history of LFLGAS with low EF and paradoxic LFLGAS has long been linked to mortality, yet its diagnosis and management remain challenging. [2][3][4] Parikh and colleagues 1 laudably applied rigorous echocardiographic standards and measured the LVSVI for additional clarity in their diagnosis of LFLGAS, consistent with current guidelines. 2 The standards used in this study, however, may not necessarily be reproducible in all centers for the reliable diagnosis of LFLGAS. The echocardiographic assessment of valve area by the continuity equation involves an estimation of flow on the basis of an assumption of left ventricular outflow tract circularity. Variability of outflow tract anatomy and Doppler angle placement may commonly impair precise echocardiographic assessment of flow and of calculated valve area. 3,4 In the setting of LFLGAS and low EF, adjunctive catheterization or dobutamine testing is often used to differentiate true valve severity from a state of low output and only moderate aortic stenosis. 5 Furthermore, the diagnosis of paradoxic LFLGAS may be confounded by multiple factors, such as impaired diastolic filling, compromised longitudinal systolic function, atrial fibrillation, obesity, heart failure, and the presence of significant mitral or tricuspid valve regurgitation or stenosis. 3,6 In response, some have advocated the use of cardiac magnetic resonance imaging as a more precise diagnostic tool that may simultaneously detect potential outcome-influencing myocardial fibrosis. 4,7 Nevertheless, when accurately diagnosed, LFLGAS is a known marker of reduced survival. [2][3][4][5][6][7] Parikh and colleagues 1 clearly demonstrate that LVSVI and the subtype of aortic stenosis have an influence on 5-year mortality after AVR. They note that for paradoxic LFLGAS the hazard ratio was 1.48 (95% confidence interval [CI] of 1.15-1.88), whereas LFLGAS with low EF had a hazard ratio of 2.03 (95% CI of 1.41-2.93). It is of comparative interest that their univariable hazard ratios associated with preoperative dialysis and reoperative cardiac surgery were 3.97 (95% CI of 2.12-7.43) and 2.07 (95% CI of 1.48-2.92), respectively. In a recent similar analysis of 1154 patients undergoing AVR, Clavel and associates 8 also found that LVSVI was an important preoperat...

Outcome of isolated aortic valve replacement in patients with classic and paradoxical low-flow, low-gradient aortic stenosis

“…The intrinsic myocardial dysfunction, although not translated in LVEF impairment, may explain the greater mortality compared with the NFHG AS. 10,11,[16][17][18][19][20][21][22][23] These patients have a better prognosis if treated surgically, although they have a greater operative risk, given their intrinsic myocardial dysfunction and the increasing risk of having mismatch due to their small ventricular cavity resulting from severe hypertrophy. 1,2 Discrepancies among previous studies on PLFLG AS highlight the importance of the correct diagnosis of this entity, because any minimal measurement error on the diagnostic echocardiography could label wrongly a different entity of AS with a complete different prognosis and outcome after AVR (ie, moderate AS with underestimated SV and AVA or severe AS with underestimated gradient).…”

“…20 There is a role for multidetector computed tomography and quantification of valve calcification when the echocardiography is not conclusive. 17,[20][21][22][23] Current American College of Cardiology/American Heart Association guidelines recommend AVR for symptomatic CLFLG AS (Class IIa, Level B) whereas the European Society of Cardiology/European Association for Cardio-Thoracic Surgery recommend AVR (Class IIa, Level C) in patients with LV contractile reserve. For the PLFLG AS, the Current American College of Cardiology/ American Heart Association and ESC/European Association for Cardio-Thoracic Surgery guidelines recommend AVR for symptomatic patients (Class IIa, Level C) only if the clinical, anatomic and hemodynamic data support the valve stenosis as the most likely cause of the symptoms.…”