TNNI3 and hydrops fetalis: To investigate the causal effect of circulating cTnI on both AMI and HF, we performed two-sample MR using 11 of 12 index variants from our meta-analysis as an instrument for cTnI [F-statistic = 44, r2 = 0.012 in the independent sample (N = 3424)], and summary-level data on AMI (5948 AMI cases, 355 246 controls from UK Biobank) and HF [47 309 cases and 930 014 controls from the Heart Failure Molecular Epidemiology for Therapeutic Targets (HERMES) Consortium].