Echocardiographic comparison of 35 panic disorder patients to 35 normal control subjects found subclinical increases of cardiac left ventricular chamber size in eight panic patients (and one control subject), and of left ventricular mass (corrected for body surface area) in seven panic patients. There was a significantly greater variance of left heart chamber size and corrected mass in panic patients compared with control subjects, without significant group mean differences. Consistent with a previously reported association of panic anxiety and idiopathic dilated cardiomyopathy, this study suggests that some healthy panic patients may have subclinical myocardial changes.