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Hazy appearance of the lung fields is due to pulonary edema due to acute left ventricular failure. Overall it appears like an underpenetrated film. The X-ray taken after treatment shows clearance of pulmonary edema (below). When the cardiac size is normal, the possibilities to be thought of are acute left ventricular failure in acute myocardial infarction when the heart has not had enough time to get enlarged and in acute fulminant myocarditis.

