Heart failure remains one of medicine's most stubborn unsolved problems — not because we can't open blocked arteries, but because the roughly one billion cardiomyocytes lost in a major heart attack simply don't grow back. Every intervention that restores blood flow leaves behind a scar, not muscle. Understanding how close regenerative science is to changing that calculus matters enormously for the roughly 64 million people living with heart failure worldwide.
This narrative review in Medicine International synthesizes the current state of myocardial repair strategies across several overlapping frontiers. Early cell therapies using mesenchymal stromal cells and bone marrow-derived mononuclear cells produced only modest improvements in left ventricular ejection fraction in clinical trials — gains now attributed largely to anti-inflammatory paracrine signaling rather than genuine muscle replacement. Cardiac progenitor cell platforms and allogeneic delivery approaches improved procedural safety profiles but generated inconsistent efficacy data. The more structurally ambitious approaches — induced pluripotent stem cell (iPSC)-derived cardiomyocytes and engineered cardiac patches combining cells with biocompatible scaffolds — show encouraging safety signals in early human studies, but unresolved challenges around arrhythmogenic risk, immune rejection, manufacturing scalability, and long-term graft durability remain substantial obstacles. Gene and RNA therapeutics and extracellular vesicle-based strategies represent parallel molecular tracks with distinct mechanistic rationales.
This review arrives at an honest inflection point for the field. The optimism of the early 2000s around bone marrow cells has been largely tempered by replication failures, forcing a productive pivot toward iPSC-derived and bioengineered constructs with stronger biological rationale. The arrhythmia liability of engrafted cardiomyocytes — documented in primate models — is arguably the field's most consequential unsettled safety question, and no clinical strategy has fully resolved it. As a narrative review rather than a meta-analysis, the article synthesizes rather than quantifies, which limits statistical precision. Still, it provides a useful road map for where the field stands: perfusion can be restored reliably, but true remuscularization remains aspirational. The next decade of trials will determine whether the structural repair approaches reach clinical viability.