Hot phase episodes in arrhythmogenic cardiomyopathy: More than just a desmoplakin issue?

Arrhythmogenic cardiomyopathy (ACM) is a genetically determined myocardial disease characterized by myocyte loss, fibro-fatty replacement, and electrical instability. In a subset of patients, episodes of chest pain with troponin release and electrocardiographic abnormalities occur in the absence of ischemic causes. These events, commonly referred to as "hot phases" (HP), often mimic acute myocarditis and raise important diagnostic and prognostic considerations. Among ACM-related genes, desmoplakin (DSP) variants are most frequently associated with HP, although episodes have also been observed in carriers of genes not classically associated with this presentation. Evidence suggests that HP presentation may vary across genotypes and ACM phenotypes, with DSP carriers more often exhibiting left sided or biventricular involvement. Growing data indicate that inflammation, autoimmunity, and innate immune activation play a central role in HP expression and ACM pathobiology, supported by findings of myocardial inflammatory infiltrates, circulating anti-desmosomal and anti-intercalated disc autoantibodies, and activation of NLRP3-inflammasome pathways. These mechanisms may contribute to disease progression and arrhythmic vulnerability. Therapeutic strategies remain empirical, but recent observations suggest that immunosuppressive therapy may modulate arrhythmic and heart-failure outcomes in DSP carriers. This review summarizes current knowledge on the clinical, genetic and immunologic features of HP in ACM, and discusses how these findings may refine the diagnostic approach and clinical interpretation of myocarditis-like presentations.