Enhanced External Counterpulsation in Patients With Fontan Circulation

The purpose of the proposed study is to determine the safety of enhanced external counterpulsation (EECP), a system for compressing the blood vessels in the legs in synchrony with an individual's cardiac rhythm, in clinically well, adult Fontan patients, to document the acute hemodynamic and myocardial effects of EECP on the Fontan circulation, and to demonstrate acute changes in endothelial function after one hour of the procedure.

The investigators plan to study the effects of enhanced external counterpulsation (EECP), on patients who have had Fontan surgery for treatment of complex congenital heart disease. Eligible patient volunteers will undergo a series of biophysical measurements at rest including echocardiographic assessment of ventricular function, pulmonary blood flow/cardiac output measurement using an inert gas rebreathing method (Innocor), and measurements of biomarkers of endothelial function (ET-1, NOx). Patients will then undergo 1 hour of treatment with EECP, during which additional echocardiographic assessment of ventricular function and pulmonary blood flow/cardiac output measurements will be performed at multiple levels of leg compression. Subjects will be assessed periodically for adverse effects and discomfort during the EECP treatment. At the completion of treatment, patients will be allowed 30 minutes to rest before undergoing one more echocardiographic assessment of ventricular function, pulmonary blood flow/cardiac output measurement, and measurements of biomarkers of endothelial function (ET-1, NOx). Measurements made during and after treatment will be compared to baseline measurements.

Measurement of cardiac output (pulmonary blood flow) in L/min using inert gas rebreathing method (Innocor CO device)

Immediately prior to starting EECP treatment, during each 20-minute phase of EECP treatment, and 30 minutes after EECP treatment

Global mid-ventricle circumferential strain (%) and global longitudinal strain (%) calculated from speckle-tracking echocardiography

Immediately prior to starting EECP treatment, during each 20-minute phase of EECP treatment, and 30 minutes after EECP treatment

Qualitative assessment of systolic function of dominant ventricle on 2-dimensional echocardiography, categorized as normal, low normal to mildly depressed, mildly depressed, mildly to moderately depressed, moderately depressed, moderately to severely depressed, severely depressed, or unable to determine.

Immediately prior to starting EECP treatment, during each 20-minute phase of EECP treatment, and 30 minutes after EECP treatment

Inclusion Criteria: Individuals with Fontan physiology being seen in the Boston Children's Hospital cardiology clinic for outpatient care. Exclusion Criteria: Current pregnancy Decompensated heart failure/pulmonary edema Severe aortic insufficiency Active tachyarrhythmias Frequent atrial or ventricular ectopy Symptomatic peripheral vascular disease Thrombophlebitis or history of deep vein thrombosis or stasis ulcer Aortic aneurysm Uncontrolled hypertension (systolic blood pressure >180 mmHg or diastolic blood pressure>110 mmHg) Systolic blood pressure <90 mmHg Active femoral site bleeding or hematoma