Exercise responses in functional single ventricle before and after Fontan operation

Coupling Pediatric Ventricle Assist Devices to the Fontan Circulation: Simulations with a Lumped-Parameter Model

In pediatric ventricular assist device (VAD) design, the process of matching device characteristics and dimensions to the relevant disease conditions poses a formidable challenge because the disease spectrum is more highly varied than for adult applications. One example arises with single-ventricle congenital defects, which demand palliative surgeries that create elevated systemic venous pressure and altered pulmonary hemodynamics. Substituting a mechanical pump as a right ventricle has long been proposed to eliminate the associated early and postoperative anomalies. A pulsatile lumped-parameter model of the single-ventricle circulation was developed to guide the preliminary design studies. Two special modules, the pump characteristics and the total cavopulmonary connection (TCPC) module, are introduced. The TCPC module incorporates the results of three-dimensional patient-specific computational fluid dynamics calculations, where the pressure drop in the TCPC anastomosis is calculated at the equal vascular lung resistance operating point for different cardiac outputs at a steady 60/40 inferior vena cava/superior vena cava flow split. Preliminary results obtained with the adult parameters are presented with no ventricle remodeling or combined larger-size single ventricle. A detailed literature review of single-ventricle function is provided. Coupling a continuous pump to the single-ventricle circulation brought both the pulmonary and systemic venous pressures back to manageable levels. Selected VADs provided an acceptable cardiac output trace of the single left ventricle, after initial transients. Remodeling of the systemic venous compliance plays a critical role in performance and is included in this study. Pulsatile operation mode with rotational speed regulation highlighted the importance of TCPC and pulmonary artery compliances. Four different pumps and three patient-specific anatomical TCPC pathologies were studied. Magnitudes of the equivalent TCPC resistances were found to be comparable to the vascular resistances of the normal baseline circulation, significantly affecting both the VAD design and hemodynamics.

Congenital heart disease and exercise

Though initially challenging, the process of determining appropriate levels of exercise for patients with congenital heart disease can be broken down into several practical steps: List 1: Summary of approach to CHD patients and exercise Get the records: Surgical reports, diagnostic test results, office visits, admissions [table: see text] Obtain family history: Family members with sudden death increase risk. Thorough physical exam: Special attention to auscultation of murmurs Appropriate diagnostic testing: Noninvasive testing is usually adequate. Review guidelines: 26th Bethesda Conference, 1994 [13] Make recommendation: Be specific about types of exercise allowed. Reassess at least annually: Patients' status may change over time [24]. The use of this algorithm and review of available guidelines, in combination with selected consultation with other specialists, should allow the sports physician to prescribe exercise for the majority of these patients confidently. Examples of several congenital defects of varying severity, and the appropriate exercise prescription, are listed in Table 1.

Exercise performance after the arterial switch operation for D-transposition of the great arteries

Early- and intermediate-term results of the arterial switch operation for D-transposition of the great arteries (D-TGA) are encouraging. However, questions remain about the long-term outcome for these patients, especially with regard to exercise performance. Preliminary studies have demonstrated normal endurance time on treadmills. However, data regarding aerobic capacity and cardiopulmonary function are lacking. We report the cardiopulmonary performance of 22 school-age patients with D-TGA who underwent the arterial switch operation. Outcome variables included maximal oxygen consumption (VO2), maximal cardiac index, and peak heart rate. Patient and procedure-related variables were assessed for their association with outcome variables using linear and logistic regression. The mean values of maximal VO2 (113 +/- 19% predicted) and maximal cardiac index (96 +/- 18% predicted) were within normal limits for the pediatric population. Although the mean peak heart rate for the entire group (184 +/- 14 beats/min) was within normal limits, there were 7 subjects (32%) with chronotropic impairment. Significant ST-segment depression was seen in 2 subjects (9%). In regression analysis, surgery subsequent to the arterial switch was associated with lower maximal cardiac index (p = 0.01). Other variables were not significantly associated with maximal VO2, maximal cardiac index, and peak heart rate. In particular, chronotropic impairment was not significantly associated with maximal VO2 or maximal cardiac index. These findings demonstrate that cardiopulmonary performance during exercise is excellent after the arterial switch operation. The finding of ST-segment depression in some subjects supports the role of formal exercise testing in those patients participating in vigorous athletic activities.

Role of exercise in the management of cardiovascular disease in children and youth

Most cardiovascular disease in children and youth is the result of congenital anomalies. Surgical techniques for repair of these defects have improved greatly since they were first developed, and a high percentage of patients become healthy, active adults. Less frequently, other types of cardiovascular disease may be acquired sometime after birth. In patients with either congenital or acquired heart disease, there is often some degree of exercise limitation. Appropriately, there is an increasing interest in the use of exercise testing and training in the clinical management of both congenital and acquired cardiovascular disease in children and youth. This review describes the exercise responses of patients with various forms of cardiovascular disease and discusses the use of exercise training to improve the well-being of these children and adolescents.