Discussion

Low flow, low gradient aortic stenosis (LFLGAS) is associated with a higher risk of a cardiac event and heart failure, increasing the rate of all-cause mortality, cardiovascular- and valvular-related death27. Aortic valve replacement (AVR) is effective in either classical or paradoxical LFLGAS 28. AVR has shown to be able to reduce the rate of adverse events and improve left ventricle ejection fraction (LVEF), enhancing long-term survival when compared to non-aortic valve replacement (noAVR) approaches. However, in patients with concomitant coronary artery disease (CAD and reduced contractile reserve (CR), the preoperative risk is too high to opt for AVR 29,30. In these cases, medical management is the recommended alternative approach, despite its reduced long-term survival rates 31. The aim of techniques alternative to AVR is to treat patients who are inoperable because of concomitant life-threatening comorbidities and the reduced life expectancy32. The therapy has more palliative purposes, and it is per se related to complications such as stroke, aortic regurgitation, myocardial infarction 33, restenosis, and deterioration of the aortic valve (AV) 34,35.
The main finding of your meta-analysis is the superiority of AVR over noAVR in enhancing survival in patients with LFLGAS. Our result is consistent with studies reporting improved outcomes following AVR rather than noAVR 36. AVR bears an elevated preoperative risk, but its benefits still outweigh the disadvantages when compared to noAVR. This is attributable to the fact that in high-risk patients with low life expectancy, medication with or without valvuloplasty represents a mere palliative cure not aimed at achieving therapeutic responses. NoAVR approach is mainly oriented towards the management of the cardiovascular risk factors, which include controlling hypertension and volume status. Furthermore, the low survival rate in the noAVR group could be the result of the increased risk of restenosis after valvuloplasty, which leads to deterioration of the valve already after one year37,38. Indeed, if, on the one hand, valvuloplasty reduces the transvalvular pressure gradient and improves symptoms, on the other hand, the post-valvuloplasty AVA does not exceed 1.0 cm2 33,39. Moreover, our result could have been influenced by the employment of the TAVR technique in some of the patients included in our analysis, as TAVR has better survival rates than SAVR as well as better LVEF recovery3,40,41.
The second finding of our meta-analysis was the increased survival at follow up in patients with reduced LVEF compared to those with preserved LVEF in the AVR group. Despite this could be initially counterintuitive, it is critical to acknowledge that it has been widely proved that LV dysfunction is present even with preserved LVEF. Indeed, studies employing speckle-tracking echocardiography have shown that in patients with LFLGAS and normal LVEF, LV systolic longitudinal dysfunction manifests as a result of the increased afterload 12. Additionally, in patients with a low LVEF undergoing coronary artery bypass grafting (CABG) concomitantly to AVR, long-term survival appears to be enhanced. CABG makes the myocardium in certain areas viable, increasing LV function, and exerting a protective effect35,42 leading to an improvement in LVEF that was reduced consequently to CAD.
Being the majority of the patients in our meta-analysis operated on AVR+CABG, we believe that the simultaneous CABG procedure might have been beneficial for patients with low LVEF 2.
Furthermore, we found that LVEF does not impact survival in the noAVR group. We believe that these results are attributable to the fact that conservative management has palliative purposes, thus not improving cardiac function but only dealing with symptoms 31. This is because both classical and paradoxical LFLGAS can induce heart failure via different mechanisms. Patients with classical LFLGAS have low survival rates as the cardiac function is severely compromised by the small LV cavity size due to LV hypertrophy, severe myocardial fibrosis, and the restrictive pattern of LV filling 2. On the other hand, some studies suggest that conservative management is not particularly useful in increasing survival in the case of paradoxical LFLGAS as a result of the advanced stage of myocardial fibrosis, the systolic and diastolic dysfunction and the reduced stroke volume index 2. Moreover, patients with paradoxical aortic stenosis mostly have diffused atherosclerosis and increased stiffness of arterial walls, which decreases arterial compliance2. In this situation, medical management is only useful in treating resulting hypertension rather than affecting the aortic valve 3.