Model-Based Comparison of the Normal and Fontan Circulatory Systems-Part III.

Background: For patients with the Fontan circulatory arrangement, angiotensin-converting enzyme inhibition, guanylate cyclase activation, phosphodiesterase 5 inhibition, and endothelin receptor antagonism have so far resulted in little or no improvement in [Formula: see text] or peak cardiac index (CI), suggesting that our understanding of the factors that most impact the exercise hemodynamics is incomplete.

Methods: To facilitate comparisons with clinical reports of the exercise performance of preadolescent Fontan patients, we rescaled our previously reported computational models of a two-year-old normal child and similarly aged Fontan patient, extended our Fontan model to capture the nonlinear relationship between flow and resistance quantified from previous computational fluid dynamic analyses of the total cavopulmonary connection (TCPC), and added respiration as well as skeletal muscle contraction.

Results: (1) Without respiration, the computational model for both the normal and the Fontan cannot attain the values for CI at peak exercise reported in the clinical literature, (2) because flow through the TCPC is much greater during inspiration than during expiration, the effect on the CI of the dynamic (flow-related) TCPC resistance is much more dramatic during exercise than it is in breath-hold mode at rest, and (3) coupling breathing with skeletal muscle contraction leads to the highest augmentation of cardiac output, that is, the skeletal muscle pump is most effective when the intrathoracic pressure is at a minimum-at peak inspiration.

Model-Based Comparison of the Normal and Fontan Circulatory Systems-Part II: Major Differences in Performance Characteristics.

Background: In the absence of an accessible chronic animal model of the Fontan circulation, computational modeling can provide insights into this unique circulatory arrangement, especially how differently it behaves from the normal mammalian circulation. Many groups have focused on refining a single element of the entire Fontan circulation-the total cavopulmonary connection (TCPC). Yet, only modest improvements in transplant-free survival have resulted.

Model-Based Comparison of the Normal and Fontan Circulatory Systems: Part I: Development of a General Purpose, Interactive Cardiovascular Model.

Background: Every year, approximately 1,000 Fontan operations are performed in the United States. Transplant-free, 30-year survival is only 50%. Although some performance characteristics may be universal among Fontan survivors, others may be patient specific and tunable; in either case, a quantitatively rigorous understanding of the Fontan circulatory arrangement would facilitate improvements in patient surveillance and management.

Insights after 40 years of the fontan operation.

Fontan's visionary operation and its modifications over the ensuing decades have re-established nonturbulent flow and substantially reduced cyanosis for patients with severe hypoplasia of one ventricle. However, a long list of largely unexpected sequelae has emerged over the last 40 years. Although it is not difficult to understand how care providers could become discouraged, a number of myths have arisen, which we will attempt to dispel with real-world counterexamples as well as with lessons learned from other disciplines: evolutionary, developmental, and computational biology.

A computational model of cardiovascular physiology and heart sound generation.

A computational model of the cardiovascular system is described which provides a framework for implementing and testing quantitative physiological models of heart sound generation. The lumped-parameter cardiovascular model can be solved for the hemodynamic variables on which the heart sound generation process is built. Parameters of the cardiovascular model can be adjusted to represent various normal and pathological conditions, and the acoustic consequences of those adjustments can be explored.

The impact of computer-assisted auscultation on physician referrals of asymptomatic patients with heart murmurs.

Background: As many as 50-70% of asymptomatic children referred for specialist evaluation or echocardiography because of a murmur have no heart disease.

Hypothesis: Computer-assisted auscultation (CAA) can improve the sensitivity and specificity of referrals for evaluation of heart murmurs.

Methods: Seven board-certified primary care physicians were evaluated both without and with use of a computer-based decision-support system using 100 prerecorded patient heart sounds (55 innocent murmurs, 30 pathological murmurs, 15 without murmur).

Computer-aided auscultation of the heart: from anatomy and physiology to diagnostic decision support.

There is a clear and present need for computer-aided auscultation of the heart which arises from the highly informative nature of heart sounds, the inherent difficulty of auscultation and increasing pressure in healthcare for rapid, accurate, objective, documented and cost-effective patient evaluation and diagnostic decision making. There are advanced signal processing technologies that hold promise for developing computer-aided auscultation solutions that are intuitive, efficient, informative and accurate. Computer-aided auscultation offers an objective, quantitative and cost-effective tool for acquiring and analyzing heart sounds, providing archival records that support the patient evaluation and referral decision as well as serial comparisons for patient monitoring.

Computer-assisted detection of systolic murmurs associated with hypertrophic cardiomyopathy: a pilot study.

A pilot study was conducted to ascertain the level of agreement between auscultatory findings derived from heart sound recordings by a cardiologist and the results of a computer-based heart sound analysis algorithm. Heart sound recordings were obtained from volunteer subjects previously diagnosed with hypertrophic cardiomyopathy. Twenty-second recordings were obtained at each of 4 standard auscultatory locations on the precordium in 2 postures: standing and reclining.