Peripheral Vascular Adaptation and Orthostatic Tolerance in Fontan Physiology

Abstract

Background-The Fontan circulation is critically dependent on elevated venous pressures to sustain effective venous return. We hypothesized that chronically increased systemic venous pressures lead to adaptive changes in regional and peripheral vessels to maintain cardiac output, especially when patients are upright. Methods and Results-Nine post-Fontan procedure patients (aged 13 to 24 years) and 6 age-and sex-matched controls were compared with techniques to measure circulatory responses (peripheral and compartmental blood flow, venous capacity, and microvascular filtration). Parameters studied included strain-gauge plethysmography measures of peripheral circulatory function, regional blood volume distribution by impedance plethysmography, and head-up tilt testing. Important differences between Fontan patients and controls were seen in several vascular compartments: (1) Calf capacitance was lower (median, 3.5 versus 5.5 mL/100 mL tissue; Pϭ0.005), and resting venous pressure was higher (13.0 versus 10.5 mm Hg; Pϭ0.004); (2) higher leg arterial resistance was observed (32.1 versus 22.2; Pϭ0.03); (3) microvascular filtration pressures and threshold for edema were elevated; and (4)

Hemodynamic performance of the Fontan circulation compared with a normal biventricular circulation: a computational model study

“…In view of the importance of arterial pressure maintenance, the role of reducing R sys in improving CO is likely to be limited in Fontan patients. This is supported by previous clinical findings that ACEI did not significantly increase CO or improve exercise capacity in postoperative Fontan patients (39,44). Nevertheless, it has been speculated that reducing R sys using ACEI might be beneficial for patients with severe ventricular systolic dysfunction (68).…”

“…Increased systemic vascular resistance (R sys ) has been frequently found in postoperative Fontan patients (39,43). This has naturally motivated the use of angiotensin-converting enzyme inhibitors (ACEI) to reduce systemic vascular resistance with an expectation to improve CO; however, the clinical benefits of the medication remain to be proven (68).…”

“…However, the predominant role of pulmonary vascular resistance might be challenged when the hemodynamic behaviors of the Fontan circulation are complicated by coexisting abnormalities in other cardiovascular properties. In fact, many patients with a Fontan circulation have been found to undergo chronic changes in peripheral vascular properties and progressive ventricular dysfunction after the operation (14,24,39,61), i.e., few Fontan patients can sustain normal cardiovascular function in their long-term prognosis. In this sense, a thorough investigation on the ways in which different cardiovascular abnormalities affect hemodynamic characteristics of the Fontan circulation may provide useful knowledge to help doctors identify the factors that dominate the pathological hemodynamic conditions of a specific patient and accordingly implement the most efficacious therapy.…”

Cerebral venous outflow resistance and interpretation of cervical plethysmography data with respect to the diagnosis of chronic cerebrospinal venous insufficiency

“…SGP is a noninvasive technique that measures variations in electrical resistance associated with changes in blood volume, recorded by the means of a sensor encircling any cylindrical segment of the body 2,3 .…”

Older Age at Completion of Fontan Procedure Is Associated with Improved Percentage of Predicted Maximum Oxygen Uptake

“…Although the Fontan surgical approach results in a stable physiology, there are attendant circulatory disadvantages, including elevated central venous pressures, 10 reduced ventricular filling, 11,12 and overall decreased cardiac output. 13 During exertion, these shortcomings are intensified.…”