This review draws on lessons from the Multicenter Intervention in Myocarditis and Acute Cardiomyopathy (IMAC)-2 trial. The review is titled The Natural History of Acute Dilated Cardiomyopathy. However, while the cases discussed here demonstrated acute clinical manifestations in their initial presentations, the diseases they represent may have been months or years in development, as acknowledged by the discussion at the end. And while the term “idiopathic” DCM was used to describe the patient population (patients with stress CM, systemic diseases known to produce CM, suspected ischemic etiology and tachycardia mediated DCM were excluded) specific causes are suspected in a significant number, the most common category being genetic. Viral myocarditis, once a wastebasket term for this syndrome, accounts for only around 10%.
The prognosis for this syndrome seems to be improving in the era of neurohumeral antagonists. From the review:
Mean initial LVEF was 24% ± 8% and increased to 40% ± 12% during treatment with ACE-I/ARB (82%), and a beta-blocker (94%). Transplantation-free survival at 1, 2, and 4 years was 94%, 92%, and 86%, respectively. This survival rate was substantially higher than the prior era.
The role of myocardial biopsy is diminishing and is now restricted to special situations:
Finally, endomyocardial biopsy is occasionally indicated in patients with ADCM. Current practice guidelines suggests that it is useful for patients with new onset cardiomyopathy in whom allergic/eosinophilic myocarditis, cardiac sarcoidosis, or giant cell myocarditis are suspected (17). The low diagnostic yield has led to a decline in its use (less than 10%) combined with the lack of proven efficacious therapy for lymphocytic myocarditis has led to substantial decrease in the use of this invasive technique. Biopsy can be useful for detecting treatable systemic diseases known to affect the myocardium such as sarcoid or eosinophilia..