(i–l) Measurements of spark frequency, time to peak (TTP), duration, and spark-mediated leak in sham and HF cells at baseline and following treatment with AIP or PKA (sham: nsparks = 32, ncells = 42, nhearts = 3; HF: nsparks = 476, ncells = 65, nhearts = 5; HF + AIP: nsparks = 163, ncells = 63, nhearts = 5; HF + H89: nsparks = 196, ncells = 43, nhearts = 3). The gene discussed is AIP; the disease is hydrops fetalis.