Shoshin beriberi, a uncommon cause of hemodynamic instability (or cardiac shock) and acute heart failure may go undiagnosed in Western countries where prevalence is low. This severe heart condition due to thiamine deficiency is rapidly fatal unless specific therapy is given. The most frequent cause in France is chronic alcoholism. There are no specific signs on the electrocardiogram in a patient with acute heart failure due to shoshin beriberi. The chest x-ray simply shows signs of pulmonary edema and heart enlargement. The echocardiography may be normal although hypokinesia and/or dilatation of the left ventricle (due to thiamine deficiency) are sometimes noted. Diagnosis is suspected in patients with chronic alcoholism who develop acute global heart failure with lactic acidosis. Right catheterism confirms low cardiac output resulting from arteriovenous shunts. Blood tests (red cell transacetolase activity, measurement of effect of pyrophosphatase, plasma and intraerythrocyte thiamine) confirm the diagnosis a posteriori. Clinical improvement is rapid after intravenous infusion of vitamin B1. The danger of fulminant beriberi heart failure in undernourished alcoholic patients emphasizes the need for regular prescription of vitamin B1.