Usefulness of Head-Up Tilt in Patients With Heart Disease

Circulatory responses to 60° head-up tilt were studied in 12 normal subjects and 53 cardiac patients with ischemic heart disease or idiopathic cardiomyopathy.In normal subjects, 60° head-up tilt caused obvious increase in heart rate and diastolic pressure, a slight decrease in systolic pressure and marked decrease in cardiac output.The circulatory changes occurring during application of the tilt were less pronounced in cardiac patients than in the normal subjects. Moreover, in contrast to the situation in normal subjects, cardiac output was increased in cardiac patients who had a cardiac index of less than 2.2l/min/m2 and in whom left ventricular end-diastolic pressure at rest was greater than 16mm Hg. The increase in cardiac output during the period of tilt was negatively correlated with cardiac output at rest and was positively correlated with left ventricular end-diastolic pressure at rest.Although there are various contributory factors in explaining the altered circulatory responses observed during head-up tilting in cardiac patients with low cardiac output, we suppose that reduction of preload may be playing an important role.