Surgically corrected univentricular hearts. Anatomical, haemodynamic and functional status at a long-term follow-up

The Fontan operation and its modifications are applied to a large spectrum of congenital heart defectswith univentricular physiology. The Fontan circulation is characterised by a reduced, non-pulsatilepulmonary blood flow and the elevated central venous pressure is the main driving force for thepulmonary blood flow. This has important consequences for the cardiorespiratory response toexercise.The development of pulmonary arteriovenous malformations is a major cause of progressivecyanosis after surgery.Aims: To investigate the prevalence of pulmonary arteriovenous malformations in patients withdifferent forms of cavopulmonary anastomosis, to evaluate the role of hepatic venous blood in theirdevelopment and to compare the sensitivity of contrast echocardiography with that of pulmonaryangiography in detecting the shunts. To study to what extent a long-standing situation of reducedpulmonary blood flow has had effects on the lung function and exercise capacity and to study thecardiac output regulation and pulmonary gas exchange at rest and during exercise.Material and Methods: We studied 20 of the surviving Fontan patients operated between 1980-1991in Göteborg. The median age at investigation was 17.5 years and the median follow-up time was11.5 years. All patients underwent cardiac catheterisation, pulmonary angiography and bubble contrastechocardiography. They also performed lung function tests. Fifteen patient were subjected to cardiacoutput determination, measurements of intraarterial blood pressure and pulmonary gas exchange.Results: Nine (45%) of the 20 patients, had positive contrast echocardiography. In only two cases wasthere angiographic evidence of pulmonary arteriovenous malformations (10%). All patients had thepulmonary arteriovenous malformations in the lung with no or minimal hepatic venous blood flow.The lung volumes, maximal expiratory flows and diffusion capacity were significantly lower thanexpected. The median maximal oxygen uptake was 25 ml/kg/min. Cardiac output was lower thanexpected at all exercise levels. The patients compensated for the reduced cardiac output with anincreased arteriovenous oxygen difference. Patients with known moderate or severe right-to-left shuntshad lower PaO2 and SaO2 values and higher PA-aO2 values both at rest and during maximal exercise,compared to those with mild or no shunts.Summary: Bubble contrast echocardiography is much more sensitive in detecting pulmonaryarteriovenous malformations than pulmonary angiography. Lack of hepatic venous blood flow to thepulmonary circulation is probably the most important factor for the development of the shunts. Thepatients had small lung volumes, markedly reduced exercise capacity and low maximal heart rate. Thecause of the reduced exercise is multifactorial. Abnormal exercise performance is characterised byincreased O2-extraction and a depressed stroke volume. Preload to the systemic ventricle in a Fontancirculation is determined by the pulmonary blood flow. A reduced pulmonary blood flow leeds toreduced filling of the systemic ventricle. A reduced preload is therefore of great importance to explainthe reduced stroke volume. An impaired chronotropic function was also present and influenced theexercise capacity but was not the main factor

Sinus node dysfunction in patients with Fontan circulation : could heart rate variability be a predictor for pacemaker implantation?

Sinus node dysfunction (SND) causes significant morbidity in patients after Fontan surgery. Heart rate variability (HRV) reflects the autonomic regulation of the heart, and changes in HRV have been associated with SND in adults. We aimed to study whether changes in HRV could be detected in 24-h electrocardiographic (ECG) recordings in Fontan patients with SND. We compared HRV results from two patient groups; patients with Fontan circulation who later required a pacemaker due to severe SND (n = 12) and patients with Fontan circulation and SND, without indication for pacemaker treatment (n = 11), with two control groups; patients with Fontan circulation without SND (n = 90) and healthy controls (n = 66). The Poincare plot index SD2 (representing changes in heart rate over 24-h) and the very low-frequency (VLF) HRV component were significantly higher in both SND groups, both compared with healthy controls and patients with Fontan circulation without SND. In SND patients with pacemakers, SD2 and VLF were slightly reduced compared to SND patients without pacemaker (p = 0.06). In conclusion, in Fontan patients with SND the HRV is significantly higher compared to healthy controls and Fontan patients without SND. However, in patients with severe SND requiring pacemaker, SD2 and VLF tended to be lower than in patients with SND without pacemaker, which could indicate a reduced diurnal HRV in addition to the severe bradycardia. This is a small study, but our results indicate that HRV analysis might be a useful method in the follow-up of Fontan patients regarding development of SND

Changes in Heart Rate and Heart Rate Variability During Surgical Stages to Completed Fontan Circulation

Arrhythmia is related to heart rate variability (HRV), which reflects the autonomic nervous regulation of the heart. We hypothesized that autonomic nervous ganglia, located at the junction of the superior vena cava’s entrance to the heart, may be affected during the bidirectional Glenn procedure (BDG), resulting in reduced HRV. We aimed to investigate changes in heart rate and HRV in a cohort of children with univentricular heart defects, undergoing stepwise surgery towards total cavopulmonary connection (TCPC), and compare these results with healthy controls. Twenty four hours Holter-ECG recordings were obtained before BDG (n = 47), after BDG (n = 47), and after total cavopulmonary connection (TCPC) (n = 45) in patients and in 38 healthy controls. HRV was analyzed by spectral and Poincaré methods. Age-related z scores were calculated and compared using linear mixed effects modeling. Total HRV was significantly lower in patients before BDG when compared to healthy controls. The mean heart rate was significantly reduced in patients after BDG compared to before BDG. Compared to healthy controls, patients operated with BDG had significantly reduced heart rate and reduced total HRV. Patients with TCPC showed reduced heart rate and HRV compared with healthy controls. In patients after TCPC, total HRV was decreased compared to before TCPC. Heart rate was reduced after BDG procedure, and further reductions of HRV were seen post-TCPC. Our results indicate that autonomic regulation of cardiac rhythm is affected both after BDG and again after TCPC. This may be reflected as, and contribute to, postoperative arrhythmic events.Originally included in thesis in manuscript form with title: "Changes in heart rate variability during surgical stages to completed Fontan circulation"</p

Pacemaker treatment after Fontan surgery—A Swedish national study

Objective: Fontan surgery is performed in children with univentricular heart defects. Previous data regarding permanent pacemaker implantation frequency and indications in Fontan patients are limited and conflicting. We examined the prevalence of and risk factors for pacemaker treatment in a consecutive national cohort of patients after Fontan surgery in Sweden. Methods: We retrospectively reviewed all Swedish patients who underwent Fontan surgery from 1982 to 2017 (n = 599). Results: After a mean follow-up of 12.2 years, 13% (78/599) of the patients with Fontan circulation had received pacemakers. Patients operated with the extracardiac conduit (EC) type of total cavopulmonary connection had a significantly lower prevalence of pacemaker implantation (6%) than patients with lateral tunnel (LT; 17%). Mortality did not differ between patients with (8%) and without pacemaker (5%). The most common pacemaker indication was sinus node dysfunction (SND) (64%). Pacemaker implantation due to SND was less common among patients with EC. Pacemaker implantation was significantly more common in patients with mitral atresia (MA; 44%), double outlet right ventricle (DORV; 24%) and double inlet left ventricle (DILV; 20%). In contrast, patients with pulmonary atresia with intact ventricular septum and hypoplastic left heart syndrome were significantly less likely to receive a pacemaker (3% and 6%, respectively). Conclusions: Thirteen percent of Fontan patients received a permanent pacemaker, most frequently due to SND. EC was associated with a significantly lower prevalence of pacemaker than LT. Permanent pacemaker was more common in patients with MA, DORV, and DILV