Impact of Phrenic Nerve Palsy on Late Fontan Circulation

Plication for diaphragm paralysis after paediatric cardiac surgery: a single-centre experience

OBJECTIVE

Diaphragm paralysis is a well-known complication following surgery for CHDs, which increases morbidity, mortality, and length of hospital stay as well as costs. Herein, we present our experience with diaphragm plication following paralysis of the phrenic nerve encountered after paediatric cardiac surgery.

METHODS

This study retrospectively reviewed the medical records of 23 diaphragm plications in 20 patients who underwent paediatric cardiac surgery between January 2012 and January 2022. The patients were carefully selected based on aetiology and a combination of clinical manifestation and chest imaging characteristics including chest X-ray, ultrasonography, and fluoroscopy.

RESULTS

Twenty-three successful plications were performed in 20 patients (15 males and 5 females) out of a total of 1938 operations performed in our centre. Mean age and body weight were 18.2 ± 17.1 months and 8.3 ± 3.7 kg, respectively. The period between the cardiac surgery and diaphragmatic plication was 18.7 ± 15.1 days. The highest incidence of diaphragm paralysis was encountered in systemic to pulmonary artery shunt patients with 7 out of 152 patients (4.6%). Any mortality was not encountered during a mean follow-up period of 4.3 ± 2.6 years.

CONCLUSIONS

Early results of plication of the diaphragm following phrenic nerve palsy in symptomatic patients who underwent paediatric cardiac surgery are encouraging. Evaluation of the diaphragmatic function should be a routine part of post-operative echocardiography. Diaphragm paralysis may be a consequence of dissection, contusion, stretching, and thermal injury both in terms of hypothermia and hyperthermia.

The Influence of Respiration on Blood Flow in the Fontan Circulation: Insights for Imaging-Based Clinical Evaluation of the Total Cavopulmonary Connection

Congenital heart disease is the most common birth defect and functionally univentricular heart defects represent the most severe end of this spectrum. The Fontan circulation provides an unique solution for single ventricle patients, by connecting both caval veins directly to the pulmonary arteries. As a result, the pulmonary circulation in Fontan palliated patients is characterized by a passive, low-energy circulation that depends on increased systemic venous pressure to drive blood toward the lungs. The absence of a subpulmonary ventricle led to the widely believed concept that respiration, by sucking blood to the pulmonary circulation during inspiration, is of great importance as a driving force for antegrade blood flow in Fontan patients. However, recent studies show that respiration influences pulsatility, but has a limited effect on net forward flow in the Fontan circulation. Importantly, since MRI examination is recommended every 2 years in Fontan patients, clinicians should be aware that most conventional MRI flow sequences do not capture the pulsatility of the blood flow as a result of the respiration. In this review, the unique flow dynamics influenced by the cardiac and respiratory cycle at multiple locations within the Fontan circulation is discussed. The impact of (not) incorporating respiration in different MRI flow sequences on the interpretation of clinical flow parameters will be covered. Finally, the influence of incorporating respiration in advanced computational fluid dynamic modeling will be outlined.