Coronary flow before and after surgical versus device closure of atrial septal defect

Review findings included diminished coronary flow reserve after surgery in children with congenital heart disease and inflammation

AIM

The aim of this review was to develop a deeper knowledge of the physiology of coronary blood flow and coronary flow reserve in young patients with congenital heart disease and inflammatory diseases.

METHODS

We searched for papers published in English on coronary blood flow and coronary flow reserve using the PubMed and Google search databases. This identified 42 papers extending back to 1976 and a book from 2008 (Davis et al. Microcirculation. Boston, MA: Elsevier, 2008: 161-284).

RESULTS

Our review showed that the implications of coronary blood flow and coronary flow reserve in paediatric patients with congenital heart disease and inflammatory diseases are still not fully understood. However, a key finding was that coronary flow reserve was diminished in patients with congenital heart disease and inflammation after surgery, with or without a cardiopulmonary bypass. Other findings discussed by this review relate to volume and pressure overload in acyanotic congenital heart disease, reduced myocardial perfusion and cyanotic congenital heart disease.

CONCLUSION

We still have much to discover about paediatric patients with congenital heart disease and inflammatory diseases. Understanding the pathophysiology of coronary blood flow could help the postoperative treatment of such patients.

Blood Versus Crystalloid Cardioplegia in Pediatric Cardiac Surgery: A Systematic Review and Meta-analysis

The benefit of blood cardioplegia (BCP) compared to crystalloid cardioplegia (CCP) is still debatable. Our aim was to systematically review and synthesize all available evidence on the use of BCP and CCP to assess if any modality provides superior outcomes in pediatric cardiac surgery. A systematic literature search of the PubMed and Cochrane databases was performed with respect to the PRISMA statement (end-of-search date: January 30th, 2017). We extracted data on study design, demographics, cardioplegia regimens, and perioperative outcomes as well as relevant biochemical markers, namely cardiac troponin I (cTnI), lactate, and ATP levels at baseline, after reperfusion and postoperatively at 1, 4, 12, and 24 h as applicable. Data were appropriately pooled using random and mixed effects models. Our systematic review includes 56 studies reporting on a total of 7711 pediatric patients. A meta-analysis of the 10 eligible studies directly comparing BCP (n = 416) to CCP (n = 281) was also performed. There was no significant difference between the two groups with regard to cTnI and Lac at any measured time point, ATP levels after reperfusion, length of intensive care unit stay (WMD: -0.08, 95% CI -1.52 to 1.36), length of hospital stay (WMD: 0.13, 95% CI -0.85 to 1.12), and 30-day mortality (OR 1.11, 95% CI 0.43-2.88). Only cTnI levels at 4 h postoperatively were significantly lower with BCP (WMD: -1.62, 95% CI -2.07 to -1.18). Based on the available data, neither cardioplegia modality seems to be superior in terms of clinical outcomes, ischemia severity, and overall functional recovery.

Systemic Dosing of Thymosin Beta 4 before and after Ischemia Does Not Attenuate Global Myocardial Ischemia-Reperfusion Injury in Pigs

The use of cardiopulmonary bypass (CPB) and aortic cross-clamping causes myocardial ischemia-reperfusion injury (I-RI) and can lead to reduced postoperative cardiac function. We investigated whether this injury could be attenuated by thymosin beta 4 (TB4), a peptide which has showed cardioprotective effects. Pigs received either TB4 or vehicle and underwent CPB and aortic cross-clamping for 60 min with cold intermittent blood-cardioplegia and were then followed for 30 h. Myocardial function and blood flow was studied by cardiac magnetic resonance and PET imaging. Tissue and plasma samples were analyzed to determine the amount of cardiomyocyte necrosis and apoptosis as well as pharmacokinetics of the peptide. In vitro studies were performed to assess its influence on blood coagulation and vasomotor tone. Serum levels of the peptide were increased after administration compared to control samples. TB4 did not decrease the amount of cell death. Cardiac function and global myocardial blood flow was similar between the study groups. At high doses a vasoconstrictor effect on mesentery arteries and a vasodilator effect on coronary arteries was observed and blood clot firmness was reduced when tested in the presence of an antiplatelet agent. Despite promising results in previous trials the cardioprotective effect of TB4 was not demonstrated in this model for global myocardial I-RI.

Cardioplegia Dose Effect on Immediate Postoperative Alterations in Coronary Artery Flow Velocities After Congenital Cardiac Surgery

Abnormalities in coronary artery (CA) flow detected by echocardiography are increasingly used to guide clinical decisions in patient management. Increased CA flow has been seen postoperatively in congenital cardiac surgery. This study sought to determine immediate postoperative changes in left anterior descending (LAD) CA flow velocities, and to investigate possible factors associated with these changes. CA flow in the proximal LAD was sampled with pulsed-wave Doppler during trans-esophageal echocardiography imaging in the immediate preoperative and postoperative studies in 46 subjects. The peak velocity, velocity time integral (VTI), VTI corrected for heart rate (VTIc), and VTI rate pressure product (VTIrpp) were determined. The percent change in each measure between the preoperative and postoperative study was calculated and compared to age, body surface area (BSA), cardiopulmonary bypass time, cross-clamp time, and number of cardioplegia (CP) doses. The pH, oxygen saturation, temperature, and hemoglobin concentration (Hb) were compared for those with and without increased flow characteristics. There was an overall increase in LAD flow parameters in subjects who underwent congenital cardiac surgery. There was a significant and positive correlation of percent change in VTI, VTIc, and VTIrrp with number of CP doses and lower Hb. We propose that this phenomenon is likely of multifactorial origin, involving autoregulatory mechanism disturbance. The imaging and measurement of LAD flow velocities are feasible, reliable, and is positively correlated with number of CP doses. Interpretation of postoperative LAD flow velocities should be made in the context of intraoperative events since heart rate, blood pressure, and Hb concentration also influence CA flow parameters.

Coronary flow dynamics in children after repair of Tetralogy of Fallot

OBJECTIVES

To assess the possible effect of a stiff right ventricle on the coronary flow (CF) in patients with post-operative Tetralogy of Fallot (TOF).

BACKGROUND

Right ventricular restrictive physiology i.e. forward flow during atrial contraction (RVRP), is characteristic to many patients with post-operative TOF.

METHODS

A total of 34 patients with TOF anatomically corrected through transatrial repair were included. Coronary flow parameters were registered with transthoracic Doppler echocardiography from posterior descending (PDCA) and left anterior descending (LAD) coronary arteries in the same patient in 24/34 (71%) patients. Twenty age-matched healthy children were used as controls. Cardiac magnetic resonance (CMR) imaging was used to detect myocardial fibrosis, RV volume, and RVRP.

RESULTS

The mean age at investigation was 10.2 ± 2.8 years. RV end diastolic and end systolic volumes indexed for BSA were larger in patients with RVRP (p=0.002 and 0.008 respectively). Peak flow velocity in diastole and flow velocity time integral was increased in patients compared to controls. They were increased in the LAD in patients with fibrosis of RV (n=11) compared to patients without fibrosis (n=9) (p=0.01 and 0.047 respectively). LAD coronary flow was especially increased in patients with RVRP (n=9) as compared with those without (n=11), (p=0.006).

CONCLUSIONS

Patients at mid-term followup after correction of TOF show increase of coronary flow. This increase is more pronounced in patients with fibrosis and RVRP of the RV.

Early changes in myocardial repolarization and coronary perfusion after cardiopulmonary bypass surgery for ASD repair in children

Background

In adults, impaired myocardial repolarization and increased risk of arrhythmia are known consequences of open heart surgery. Little is known, however, about post-operative consequences of cardiopulmonary bypass surgery in children. The aim of this study was to assess ventricular repolarization and coronary perfusion after bypass surgery for atrial septal defect (ASD) repair in children.

Methods

Twelve patients with ASD were assessed one day before and 5–6 days after ASD repair. Myocardial repolarization (corrected QT interval, QTc, QT dispersion, QTd, and PQ interval) was determined on 12-lead electrocardiograms. Coronary flow in proximal left anterior descending artery (peak flow velocity in diastole, PFVd) was assessed by transthoracic Doppler echocardiography.

Results

Ten of the 12 (83%) children had normal myocardial repolarization before and after surgery. After surgery, QTc increased 1-9% in 5 (42%) patients, decreased 2-11% in 5 (42%) patients and did not change in 2 (16%) patients. Post-op QTc positively correlated with bypass time (R=0.686, p=0.014) and changes in PFVd (R=0.741, p=0.006). After surgery, QTd increased 33-67% in 4 (33%) patients, decreased 25-50% in 6 patients (50%) and did not change in 2 (16%) patients. After surgery, PQ interval increased 5-30% in 4 (33%) patients, decreased 4-29% in 6 (50%) patients and did not change in 1 (8%) patient. Post-op PQ positively correlated with bypass time (R=0.636, p=0.027). As previously reported, PFVd significantly increased after surgery (p<0.001).

Conclusions

Changes in QTc, PQ and PFVd are common in young children undergoing surgery for ASD repair. Post-op QTc significantly correlates with bypass time, suggesting prolonged cardiopulmonary bypass may impair ventricular repolarization. Post-op QTc significantly correlates with PFVd changes, suggesting increased coronary flow may also impair ventricular repolarization. The clinical significance and reversibility of these alternations require further investigations.

Pathophysiology of coronary blood flow in congenital heart disease

OBJECTIVES

The aim was to investigate the effects of volume and pressure overload and increased coronary perfusion pressure on coronary flow (CF) in congenital heart disease (CHD) patients.

BACKGROUND

The effects of CHD on CF are poorly mapped.

METHODS

A total of 65 patients with acyanotic CHD and 49 age-matched healthy controls were examined by transthoracic Doppler echocardiography. Posterior descending artery flow was measured in patients with pulmonary valve stenosis (PS) and atrial septal defects (ASDs) i.e. in lesions with right ventricular pressure or volume overload, and left anterior descending artery flow in patients with coarctation of the aorta (CoA) and ventricular septal defect (VSD), in lesions with left ventricular pressure or volume overload. The CF data in each patient group were expressed as the percent of the median for healthy controls from the same age group.

RESULTS

The CF values were in VSD 172%, ASD 185%, PS 233%, and CoA 773% patients. In CoA patients body surface area (r=0.90, p<0.0001), systolic blood pressure (r=0.72, p<0.0001), diastolic blood pressure (r=0.77, p<0.0001), systolic wall tension (r=-0.77, p=0.004), and signs of inflammation (log CRP, r=-0.75, p=0.007) correlated with CF.

CONCLUSIONS

The increase in CF and velocity was most significant in patients with CoA. In newborns, increased coronary perfusion pressure seems to be the most important factor for increased CF, even if the pressure is not assumed to cause a significant increase in flow over the auto-regulatory range of 70-130mmHg. We also showed that inflammation decreases CF.