Where Is the "Optimal" Fontan Hemodynamics?

Abstract

Fontan circulation is generally characterized by high central venous pressure, low cardiac output, and slightly low arterial oxygen saturation, and it is quite different from normal biventricular physiology. Therefore, when a patient with congenital heart disease is selected as a candidate for this type of circulation, the ultimate goals of therapy consist of 2 components. One is a smooth adjustment to the new circulation, and the other is long-term circulatory stabilization after adjustment. When either of these goals is not achieved, the patient is categorized as having "failed" Fontan circulation, and the prognosis is dismal. For the first goal of smooth adjustment, a lot of effort has been made to establish criteria for patient selection and intensive management immediately after the Fontan operation. For the second goal of long-term circulatory stabilization, there is limited evidence of successful strategies for long-term hemodynamic stabilization. Furthermore, there have been no data on optimal hemodynamics in Fontan circulation that could be used as a reference for patient management. Although small clinical trials and case reports are available, the results cannot be generalized to the majority of Fontan survivors. We recently reported the clinical and hemodynamic characteristics of early and late failing Fontan survivors and their association with all-cause mortality. This knowledge could provide insight into the complex Fontan pathophysiology and might help establish a management strategy for long-term hemodynamic stabilization.

Keywords: Cardiac output; Fontan procedure; Hemodynamics; Mortality; Vascular resistance.

Figure 1

Fontan hemodynamics without failure. In Fontan patients, the SV supports systemic circulation. High CVP is the driving pressure of the pulmonary circulation, and the MP and RP play significant roles in pulmonary circulation. Organ PP, or the pressure difference between CVP and AOP, is low due to high CVP and low systemic pressure from diminished cardiac preload. Rs (red jagged line) appropriately increases to maintain PP, while the Rp (blue jagged line) should remain low. AOP = aortic pressure; AVV = atrioventricular valve; CVP = central venous pressure; MP = muscle pump; PA = pulmonary artery; PP = perfusion pressure; RP = respiratory pump; Rp = pulmonary artery resistance; Rs = systemic artery resistance; S/IVC = superior vena cava/inferior vena cava; SV = systemic ventricle.

Figure 2

(A) Effect of CVP on all-cause mortality in early and late Fontan survivors. High CVP has a significant adverse impact on mortality in both groups of survivors. The right upper figures show that Fontan survivors with high CVP (≥14 mmHg) have a high mortality. (B) Effect of arterial blood SaO₂ on all-cause mortality in early and late Fontan survivors. Low SaO₂ has a significant adverse impact on mortality in both groups of survivors. (A) and (B) are modified from those in reference . The right lower figures show that Fontan survivors with low SaO₂ (≤93% in early survivors, ≤92% in late survivors) have high mortality. CVP = central venous pressure; SaO₂ = oxygen saturation.

Figure 3

(A) Effect of end-diastolic volume of the SV (EDVI, mL/m²) on all-cause mortality in early and late Fontan survivors. Large EDVI has a significant adverse impact on mortality only in early survivors (the cutoff value was 108 mL/m²) (upper middle). However, large EDVI has no significant adverse impact on mortality in late survivors when they were divided into 2 groups based on a median EDVI value of 74 mL/m² (upper right). (B) Effect of SV EF (%) on all-cause mortality in early and late Fontan survivors. Low EF has a significant adverse impact on mortality only in early survivors (cutoff value, 43%) (lower middle). However, low EF has no significant adverse impact on mortality in late survivors when late survivors were divided into 2 groups based on a median EF value of 53% (lower right). (A) and (B) are modified from those in reference . EDVI = end-diastolic systemic ventricular volume index; EF = ejection fraction; SaO₂ = oxygen saturation; SV = systemic ventricle.

Figure 4

Effect of CI (L/min/m²) on all-cause mortality in early and late Fontan survivors (A). Associations between CI and all-cause mortality are U-shaped in early and late survivors with no group differences. Although a low CI tends to adversely impact all-cause mortality (B) in early survivors, a high CI has a significantly adverse impact on mortality in late survivors (C). (A) is modified from reference . CI = cardiac index.

Figure 5

Effects of pulmonary (A) and systemic (B) arterial resistance on all-cause mortality in early and late Fontan survivors. Although no significant associations between these variables and all-cause mortality were identified, the associations are unique and U-shaped in the late survivors. For systemic artery resistance, low resistance tended to have an adverse impact on mortality (HR, 0.94; 95% CI, 0.87–1.00; p=0.060). 95% CI = 95% confidence interval; HR = hazard ratio.

Figure 6

Traditional failing Fontan hemodynamics (high CVP with low output) and possible therapeutic options. For systemic ventricular systolic dysfunction, conventional anti-HF strategies might be successful. In addition, pulmonary artery dilators could also be effective. For AVV impairment, surgical options should be considered. ACEI = angiotensin converting enzyme inhibitor; AOP = aortic pressure; ARB = angiotensin II receptor blocker; AVV = atrioventricular valve; AVVP/R = atrioventricular valvuloplasty or replacement; CRT = cardiac resynchronization therapy; CVP = central venous pressure; EM = coil embolization to collateral vessels; ETB = endothelin receptor blocker; HF = heart failure; HOT = home oxygen therapy; IVN = catheter intervention; LAP: functional left atrial pressure; MP = muscle pump; NO = nitric oxide; PDE5I = phosphodiesterase 5 inhibitor; PGI2 = prostaglandin I2; PTA = percutaneous transluminal angioplasty; RP = respiratory pump; Rp = pulmonary artery resistance; Rs = systemic artery resistance; S/IVC = superior vena cava/inferior vena cava.

Figure 7

Newly recognized failing Fontan hemodynamics (high CVP with high output) and possible therapeutic options. For this failing Fontan hemodynamic phenotype, traditional therapeutic approaches might be questionable and can even be harmful. Inappropriately low Rs requires vasoconstrictors, such as alpha 1 receptor agonists (midodrine). For coexistent hypoxia, oxygen inhalation might be effective. ACEI/ARBs = angiotensin converting enzyme inhibitors or angiotensin receptor blockers; AVV = atrioventricular valve; CRT = cardiac resynchronization therapy; CVP = central venous pressure; EM = coil embolization to collateral vessels; ETB = endothelin receptor blocker; HOT = home oxygen therapy; MP = muscle pump; NO = nitric oxide; PA = pulmonary artery; PDE5I = phosphodiesterase 5 inhibitor; PGI2 = prostaglandin I2; PP = perfusion pressure; PTA = percutaneous transluminal angioplasty; RP = respiratory pump; Rs = systemic artery resistance; S/IVC = superior vena cava/inferior vena cava.