The present study demonstrates that 2 months after replacement of aortic valve for AS, TAVI induces a faster recovery of LV geometry and greater reduction of estimated LV filling pressure in comparison with traditional AVR and that the reduced LV filling pressure is strongly due to changes of the same LV geometry only in TAVI group.
Because of pressure overload, LV structural changes developing in patients with AS are characterized by LV concentric remodeling and concentric LVH. These changes are associated with myocardial interstitial fibrosis, producing LV diastolic abnormalities and left atrial remodeling  while systolic chamber dysfunction has a later onset [2–5]. After the substitution of aortic valve, clinical improvement is expected and improved diastolic stiffness and relaxation are observed in late follow-up .
Recent studies have demonstrated that TAVI can determine an early regression of LVH and a significant improvement of LV diastolic properties [25–28]. In these studies the immediate reduction of transvalvular pressure gradient was associated with significant reduction of LV mass , improvement of diastolic filling pattern [25, 26, 28], reduction of LV filling pressure [27, 28] and decrease in left atrial size  while a clear improvement of systolic LV chamber function was observed only after 3 months .
To the best of our knowledge, the present study is the first to document that recovery of LV geometry and improvement of LV filling pressure are both more evident 2 months after TAVI than after traditional AVR at the same time. EF improvement was not significantly different between TAVI and AVR group confirming previous results . However, the reduction of both relative wall thickness and E/e’ ratio was more pronounced after TAVI than after AVR while LVMi was significantly reduced only after TAVI. These findings were further reinforced by the observation that the percent reductions of relative wall thickness and E/e’ ratio were substantially greater after TAVI than after AVR.
It is noteworthy that no relation was detected between the percent reduction of transvalvular pressure gradient or Zva and the percent decrease of relative wall thickness or LV filling pressure in TAVI as well as in AVR group. Accordingly, the substantial difference in the recovery of LV geometry after TAVI could not be due to the pure reduction of loading conditions, but should be ascribed to own factors related to the respective surgical procedure. A transient peri-operative LV dysfunction is well recognized after traditional AVR, this effect being related to cardiopulmonary by-pass . This transient functional deterioration is further confirmed by elevated BNP and troponin I serum levels occurring early after AVR [42, 43]. In the TAVI procedure, the consequences of cardiopulmonary by-pass are avoided and LV remodeling can occur likely due to less neuro-hormonal stimulus sustaining initial persistence of LVH.
The main finding of the present study is in fact the relation between the percent reduction of relative wall thickness and the estimated LV filling pressure (by E/e’ ratio), found only in the TAVI group. This relation remained significant even after adjusting for age and percent reduction of Zva, an index of LV global load which accounts for the effects of both AS and systemic arterial compliance, is one of the main determinant of exercise capacity  and is prognostically validated . In post-cardiac surgery of patients with overall preserved systolic LV chamber function, the degree of E/e’ ratio had been shown to be significantly associated with BNP levels, a finding which indicates left atrial pressure as a major determinant in BNP release in this clinical setting . The results of the present study highlight therefore how the early recovery of LV geometry occurring after TAVI could be as fast as a beneficial effect on the reduction of LV filling pressure and may well explain the evidence of better short and long-term prognosis of patients with AS undergoing TAVI [18–22]. Elevated LV filling pressure is the key determinant of cardiac symptoms and prognosis in patients with chronic heart failure and coronary artery disease, independent on the values of EF [46, 47]. One-year antihypertensive therapy resulting in relative wall thickness reduction has been previously found to be associated with significant improvement of LV diastolic filling parameters related to active relaxation and passive chamber stiffness, independent of BP reduction, in hypertensive patients with LVH of the LIFE study . Our results extends these relations to patients with AS undergoing TAVI in a time period which is substantially shorter to that needed by anti-hypertensive drugs to achieve the same effect in arterial systemic hypertension.
Limitations of the study
The main limitation of the study is the short duration of the follow-up period of TAVI and traditional AVR patients. While the choice of 2-months period post-implantation can be judged to be useful in order to highlight the rapid effectiveness of TAVI in improving both LV structure and diastolic function, it should also important to verify whether this improvement could be sustained at longer follow-up. Further studies will be need to analyze this aspect.
In conclusion, our study demonstrates that TAVI could induce a faster recovery of LV geometry than after traditional AVR and the shift from LV concentric remodeling/hypertrophy could be responsible in its turn of a better reduction of LV filling pressure, irrespective of changes in LV afterload.