Long-term changes in coronary physiology after aortic valve replacement

Background: The detrimental effects of long-standing severe aortic stenosis (AS) often include left ventricular hypertrophy (LVH) and exhaustion of coronary flow reserve (CFR), the reversibility of which is unclear after valve replacement.

Aims: Our aims were to 1) investigate whether CFR in the left anterior descending artery (LAD) would improve following valve replacement, and if the change was related to changes in hyperaemic coronary flow (Q_LAD) and minimal microvascular resistance (R_μ,LAD); and 2) investigate the relationship between changes in CFR and changes in left ventricular mass (LVM) and stroke work (LV_SW).

Methods: We measured intracoronary bolus thermodilution-derived CFR, and continuous thermodilution-derived Q_LAD and R_μ,LAD before and 6 months after aortic valve replacement. Cardiac magnetic resonance imaging was used to quantify left ventricular anatomy and function for the calculation of LVM and LV_SW. 

Results: Thirty-four patients were included (17 patients had transcatheter aortic valve implantation; 14 had surgical valve replacement with a bioprosthesis and 3 with a mechanical prosthesis) who underwent invasive assessment in the LAD. CFR increased from 2.5 (interquartile range [IQR] 1.5-3.3) at baseline to 3.1 (IQR 2.2-5.1) at follow-up (p=0.005), despite no significant change in Q_LAD (230±106 mL/min to 250±101 mL/min; p=0.26) or R_μ,LAD (347 [IQR 247-463] to 287 [IQR 230-456]; p=0.20). When indexed for LVM, Q_LAD was 39% (IQR 8-98%) higher at follow-up compared with baseline (p<0.001). The improvement in CFR was correlated with ΔLV_SW, r= −0.39; p=0.047.  

Conclusions: CFR in the LAD increased significantly at follow-up although global hyperaemic flow and minimal microvascular resistance remained unchanged. Thus, a decrease in resting flow was the cause of CFR improvement. CFR improvement was associated with reduction in LV_SW.