What is the clinical evidence from this study?

Study design: Cross-Sectional. Population: Fontan circulation (n=34). Intervention: Non-invasive pressure-volume loop estimation (CMR and brachial pressure) vs. Healthy controls. Primary outcome: Ventricular mechanical efficiency (%) (p=<0.0001).

What does this research mean for the field?

Non-invasive pressure-volume loop analysis reveals that patients with Fontan circulation have significantly lower ventricular mechanical efficiency compared to healthy controls, despite having similar energy per ejected volume. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.NEUTRAL.

June 6, 2022Open Access

Non-invasive quantification of pressure–volume loops in patients with Fontan circulation

Q: What are the key findings of this study?

Non-invasive pressure-volume loop analysis revealed that patients with Fontan circulation had significantly lower ventricular mechanical efficiency (56% vs 75%) compared to healthy controls.

Q: What does this research mean for the field?

Non-invasive pressure-volume loop analysis reveals that patients with Fontan circulation have significantly lower ventricular mechanical efficiency compared to healthy controls, despite having similar energy per ejected volume. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.NEUTRAL.

Key Result

Non-invasive pressure-volume loop analysis revealed that patients with Fontan circulation had significantly lower ventricular mechanical efficiency (56% vs 75%) compared to healthy controls.

Study Design

Type

Cross-Sectional (n=34)

Multicenter

Structured PICO

Does non-invasive quantification of pressure-volume loops using cardiac magnetic resonance and brachial pressure identify differences in hemodynamic parameters between patients with Fontan circulation and healthy controls?

Population

17 patients with Fontan circulation (median age 12 years, IQR 6-15, 13 male) and 17 healthy controls (median age 14 years, IQR 13-22, 12 male) with normal ECG and blood pressure, no cardiovascular medication, and no medical history of cardiovascular or other systemic disease.

Intervention

Non-invasive estimation of pressure-volume (PV) loops using cardiac magnetic resonance (CMR) and brachial pressure from cuff sphygmomanometry.

Comparator

Healthy volunteers matched for comparison.

Outcome

Hemodynamic parameters derived from non-invasive PV loops, including stroke work, ventricular mechanical efficiency, external power, potential energy, contractility (Ees), arterial elastance (Ea), Ea/Ees ratio, and energy per ejected volume.surrogate

Non-invasive PV loop quantification using CMR and brachial pressure reveals that Fontan patients have suboptimal ventricular-arterial coupling and decreased ventricular efficiency, but similar energy per ejected volume compared to healthy controls.

Main Result

Absolute Event Rate: 56% vs 75%

p-value: p=<0.0001

Limitations

Requires unobstructed communication between the systemic ventricle and the brachial artery
Approximates V0 (volume at pressure 0 mmHg) to be zero
Relies on an estimation of the ventricular end-diastolic pressure
No invasive measurements were performed for direct validation in Fontan patients
Small sample size
A minority of the Fontan patients were under general anesthesia which might influence the results

Abstract

BACKGROUND: Pressure-volume (PV) loops provide comprehensive information of cardiac function, but commonly implies an invasive procedure under general anesthesia. A novel technique has made it possible to non-invasively estimate PV loops with cardiac magnetic resonance (CMR) and brachial pressure which would enable good volume estimation of often anatomically complex ventricles without the need of anesthesia in most cases. In this study we aimed to compare how hemodynamic parameters derived from PV loops in patients with Fontan circulation differ to controls. METHODS: Patients with Fontan circulation (n = 17, median age 12 years, IQR 6-15) and healthy controls (n = 17, 14 years, IQR 13-22) were examined with CMR. Short axis balanced steady-state free-precession cine images covering the entire heart were acquired. PV loops were derived from left ventricular volumes in all timeframes and brachial blood pressure from cuff sphygmomanometry. RESULTS: Fontan patients had lower stroke work, ventricular mechanical efficiency and external power compared to controls. Fontan patients with dominant right ventricle had higher potential energy indexed to body surface area but lower contractility (Ees) compared to controls. Fontan patients had higher arterial elastance (Ea) and Ea/Ees ratio than controls. Contractility showed no correlation with ejection fraction (EF) in Fontan patients irrespective of ventricular morphology. No difference was seen in energy per ejected volume between Fontan patients and controls. CONCLUSIONS: This non-invasive PV-loop method could be used in future studies to show the potential prognostic value of these measures and if changes in ventricular function over time can be detected earlier by this method compared to changes in ventricular volumes and EF. In contrast to patients with acquired heart failure, Fontan patients had similar energy per ejected volume as controls which suggests similar ventricular oxygen consumption to deliver the same volume in Fontan patients as in controls.

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