Predicted versus observed outcomes in the ALT-FLOW early feasibility study

Whether hemodynamic and symptomatic benefits of the APTURE left atrial-to-coronary sinus shunt translate into clinical outcome benefit in heart failure with left ventricular ejection fraction >40% remains unknown.

In this post hoc analysis of ALT-FLOW EFS patients undergoing APTURE implantation, Meta-Analysis Global Group in Chronic Heart Failure (MAGGIC) score-predicted 1-year all-cause mortality was compared with observed mortality by Kaplan-Meier analysis of adjudicated events. Heart failure hospitalization (HFH) rates were compared for the 12 months before vs after implantation. Additional analyses included stratification by baseline sodium-glucose cotransporter 2 inhibitor (SGLT2i) use and N-terminal pro-B-type natriuretic peptide (NT-proBNP), recurrent HFH cumulative hazard estimation (Nelson-Aalen), and H2FPEF score calculation.

Among 95 patients (mean age 70.9 ± 8.5 years; 50% women; 93% New York Heart Association Class III; 85.9% with H2FPEF score >3), MAGGIC-predicted 1-year mortality was 13.0%. Observed 1-year survival was significantly higher than predicted (94.7% vs 87.0%; P=0.04), consistent across SGLT2i subgroups (log-rank P=0.59). The proportion of patients with HFH declined from 37.9% pre implantation to 9.6% post implantation (P<0.0001), with event rates falling from 0.61 to 0.21 per patient-year (P<0.001) and a 1-year cumulative hazard of recurrent HFH of 0.19 (95% confidence interval, 0.12-0.31). HFHs were evenly distributed across NT-proBNP strata.

In ALT-FLOW EFS, observed 1-year mortality was lower than MAGGIC-predicted mortality, and post implantation HFH rates were lower than pre implantation rates. These hypothesis-generating findings will require confirmation in the randomized, sham-controlled ALT-FLOW II trial.