Role of Doppler echocardiography for cardiac output assessment in Fontan patients

Hemodynamic Effects of Altering Tidal Volume During Positive Pressure Ventilation in the Fontan Circulation: A Randomized Crossover Trial

BACKGROUND

Primary determinants of pulmonary blood flow in the Fontan circulation are low transpulmonary gradient and pulmonary vascular resistance (PVR). Changes in intrathoracic pressure during intermittent positive pressure ventilation can influence the transpulmonary gradient, PVR, pulmonary blood flow, and cardiac output. The aim of this study was to evaluate the effect of low (5 mL/kg) versus high (10 mL/kg) tidal volume (VT) ventilation on Fontan circulation hemodynamics.

METHOD

Postoperative patients with a Fontan circulation were enrolled in this single-center, randomized crossover trial. Patients, randomized to group 1 or 2, underwent a ventilation study sequence (baseline ventilation [7 mL/kg], then high VT [10 mL/kg] or low VT [5 mL/kg], then washout ventilation [7 mL/kg], followed by low [5 mL/kg] or high VT [10 mL/kg]) in the operating room at the end of the cardiac surgical procedure. Respiratory, hemodynamic, and transesophageal (TEE) measurements were recorded after 5 min in each ventilation condition. The primary aim of this study was to evaluate the effect of low VT ventilation (5 mL/kg) versus high VT ventilation (10 mL/kg) on transpulmonary gradient (Fontan pressure minus left atrial pressure). The secondary aim was to compare TEE measurements of pulmonary blood flow, stroke volume, and Fontan flow between low and high VT ventilation. We also compared standard hemodynamic and ventilation parameters for all ventilation conditions. Analysis was of paired data, calculating the between-treatment difference within participants across ventilation conditions.

RESULTS

Eleven patients were included in the final data analysis with a median [IQR] age of 5 [4, 11] years and weight of 16.3 [13.8, 31.6] kg. The mean (±SD) peak inspiratory pressure during low and high VT ventilation was 15.3 (±2.9) cmH2O and 22.2 (±3.7) cmH2O, respectively (difference -6.9, 95% CI -7.8, -5.9, p < 0.001). The mean airway pressure during low and high VT ventilation was 7.3 ± 0.8 and 8.7 ± 0.9 (difference -1.5, 95% CI -2.1, -0.8, p = 0.001) with a mean inspiratory time of 0.62 (±0.22) s and 1.21 (±0.55) s (difference -0.59, 95% CI -0.84, -0.34, p < 0.001), respectively. During low VT ventilation, the mean Fontan pressure was 13.3 (±1.8) mmHg compared to 12.3 (±2.5) mmHg for high VT ventilation (difference 0.8, 95% CI -0.5, 2.1, p = 0.18). The mean transpulmonary gradient was 7.0 ± 1.3 mmHg compared to 6.8 ± 1.2 mmHg during low and high VT ventilation, respectively (difference 0.2, 95% CI -0.2, 0.6, p = 0.21). We found no significant differences between low and high VT ventilation in TEE measures of pulmonary blood flow, stroke volume, and Fontan flow.

CONCLUSIONS

This randomized, crossover pilot trial of Fontan patients showed that a low VT ventilation (5 mL/kg) resulted in significantly lower peak and mean airway pressure compared with a high VT ventilation (10 mL/kg). However, there were no significant changes in transpulmonary gradient, mean Fontan pressure, or TEE parameters of stroke volume, pulmonary blood flow, or Fontan flow.

CLINICAL TRIALS REGISTRATION NUMBER

NCT04633343.

PRINCIPAL INVESTIGATOR

Manchula Navaratnam.

DATE OF REGISTRATION

November 11, 2020. Clinical Trials Registration Registry URL: https://clinicaltrials.gov/study/NCT04633343?term=Fontan%20ventilation&rank=3.

PRIOR PRESENTATIONS

Congenital Cardiac Anesthesia Society Annual Meeting Top Oral Abstract Presentation.

PRESENTER

Alexander R Schmidt, March 30th, 2023.

Feasibility, reproducibility and accuracy of electrical velocimetry for cardiac output assessment in congenital heart disease

BACKGROUND

Noninvasive cardiac output assessment is important for prognostication in patients with heart failure. Electrical velocimetry (EV), an impedance cardiography technique, can be used for noninvasive cardiac output assessment. The purpose of this study was to determine the feasibility, reproducibility and accuracy of cardiac output assessment by EV in adults with congenital heart disease (CHD).

METHODS

Cross-sectional study of CHD patients that had simultaneous cardiac output assessment by Fick and EV (using Cardiotronic monitor, Osypka Medical). We divided the cohort into: Group 1 patients (n = 54) had hemodynamic assessment at rest only, while Group 2 patients (n = 7) had assessment both at rest and peak exercise.

RESULTS

EV cardiac output assessment was feasible in 100% of the patients. There was good correlation between Fick-derived and EV-derived cardiac index (r = 0.89, p < 0.001) in Group 1. Among 26 patients in Group 1 that underwent cardiac output assessment pre- and post-intervention, there was no difference in the strength of correlation of Fick and EV cardiac output pre- and post-intervention (p-interaction 0.244) indicating good reproducibility of the technique. There was also modest correlation between Fick-derived and EV-derived cardiac index at rest (r = 0.68, p = 0.032), and peak exercise (r = 0.62, p = 0.055), in Group 2.

CONCLUSION

In this study, we demonstrated the feasibility and accuracy of EV cardiac output assessment in adults with CHD. We also demonstrated, for the first time, that EV cardiac output assessment was reproducible under different loading conditions, and that EV can be used for the assessment of cardiac output augmentation at peak exercise.