Antitumor necrosis factor alpha (TNF-α) therapy for HF was not shown to improve HF and was even harmful.[10,11] Failure to improve peak aerobic exercise capacity in failing HF patients treated with anakinra.[12] The first and most obvious question raised by the neutral and/or negative clinical trials mentioned above is whether inflammation is associated with HF, or whether it is the cause of the disease.[6] These observational studies may suffer from unmeasured confounding, which makes it difficult to distinguish between cause and symptom, so they may not reflect true causal effects. Here, TNF is linked to hydrops fetalis.