Right Ventricular Contractility Reserve Following Repair of Tetralogy of Fallot

Evaluation of Right Ventricular Contractility Reserve Function During Dobutamine Stress in Patients Following Surgical Repair of Tetralogy of Fallot

Background: Residual pulmonary regurgitation following repair of tetralogy of Fallot, in particular the use of a transannular patch, has been shown to correlate with the development of right ventricular dysfunction. Optimal timing of pulmonary valve replacement, therefore, is important to preserve right ventricular function. Several recent studies suggested that a threshold of right ventricular end-diastolic volume for intervention, in order to preserve the likelihood of adequate reverse remodeling, is in the region of 150 to 200 ml/m2 body surface area. However, there is evidence that right ventricular function does not always recover following pulmonary valve replacement even if the end-diastolic volume is below this cut-off.

In addition, previous studies suggested that early dysfunction may be present before symptoms occur. However, early dysfunction is difficult to assess.

Methods: Analysis of right ventricular function by pressure-volume loops has been extensively evaluated in experimental studies and is generally considered the optimal way to quantify right ventricular function.

By recording a family of pressure-volume loops during reduction of preload, achieved by temporary balloon occlusion of the inferior caval vein, the contractility can be calculated by the slope of the endsystolic pressure-volume relation (elastance). Changes of contractility following dobutamine infusion could be noted by changes of elastance. The increase of the slope during dobutamine demonstrates the contractility reserve of the right ventricle.

Purpose: To evaluate the right ventricular contractility reserve to determine early ventricular dysfunction after repair of tetralogy of Fallot.

Inclusion Criteria:

1. Corrected tetralogy of Fallot or other surgery with involvement of the pulmonary valve, chronic pulmonary regurgitation, dilated right ventricle
2. Patient's age > 4 years
3. Routine cardiac catheterization clinically indicated for deciding therapeutic treatment
4. Informed assent/consent of patients/parent.

Exclusion Criteria:

1. Pregnancy/breast feeding, women of child-bearing age without contraception.
2. Present participation, and/or participation in a clinical study during the last 4 weeks.
3. Illnesses or malfunctions, which exclude a participation in this study after decision of the investigating physician.
4. Other medical, psychological or social circumstances which complicate a regular participation in the study, and/or increase the risk for the patients themselves.