Adrenergic nervous activity in patients after surgical correction of tetralogy of Fallot

Reduced Parasympathetic Activity in Patients With Different Types of Congenital Heart Disease and Associations to Exercise Capacity

PURPOSE

Current research indicates an imbalance in the autonomic nervous system (ANS) pathway activities in patients with congenital heart disease (CHD). The heart rate variability (HRV) is a measure to quantify activities of the parasympathetic and sympathetic branches. This study evaluated the parasympathetic activity by means of HRV in patients with CHD, regarding diagnostic subgroups and CHD severity, and the association to exercise capacity.

METHODS

From July 2016 to August 2018, a total of 222 patients with different types of CHD (28.4 ± 10.1 yr; 44% female) received breathing-controlled HRV measurement in the supine position. Based on 130 adjacent heartbeats, the root mean square of successive differences (RMSSD), a parasympathetic activity surrogate was estimated and log-transformed. Additionally, all patients underwent a cardiopulmonary exercise test. For comparison, a control group (CG) of 57 (29.0 ± 7.1 yr; 61% female) healthy volunteers was recruited.

RESULTS

Patients with CHD exhibited reduced parasympathetic activity in comparison to the CG (lnRMSSD CHD: 3.55 ± 0.57 ms vs CG: 3.93 ± 0.55 ms; P < .001), with the lowest parasympathetic activity in patients with Fontan circulation (3.07 ± 0.54 ms; P < .001). Complex CHD (3.40 ± 0.54 ms) had worse values compared with patients with simple (3.87 ± 0.55 ms; P < .001) and moderate severity (3.74 ± 0.54 ms; P < .001). Better parasympathetic activity in CHD patients was associated with increased exercise capacity (r = 0.322; P < .001).

CONCLUSIONS

Impaired parasympathetic activity suggests limited function of the ANS in patients with CHD. Further studies should focus on the association of exercise capacity and ANS to possibly improve parasympathetic activity and functional outcomes.

The severity of ventricular arrhythmia correlates with the extent of myocardial sympathetic denervation, but not with myocardial fibrosis extent in chronic Chagas cardiomyopathy : Chagas disease, denervation and arrhythmia

BACKGROUND

To investigate the correlation between the extent of myocardial sympathetic denervation and fibrosis and the presence of degrees of severity of ventricular arrhythmias in chronic Chagas cardiomyopathy (CCC).

METHODS

Forty-three CCC patients with left ventricular ejection fraction (LVEF) ≥ 35% were divided into three groups: SVT group-presenting Sustained Ventricular Tachycardia (SVT) (n = 15), NSVT group-exhibiting episodes of non-SVT (NSVT) on 24-h Holter monitoring (n = 11), and Control group-exhibiting neither SVT nor episodes of NSVT (n = 17). The patients underwent SPECT imaging for myocardial sympathetic innervation with 123Iodine-MIBG (MIBG) and myocardial perfusion with 99mTc-Sestamibi (MIBI) for the evaluation of regional myocardial fibrosis.

RESULTS

The summed rest perfusion scores were similar in the three groups. The summed difference score between MIBG and MPI images, which evaluated the extent of denervated but viable myocardium, was significantly higher in SVT group (20.0 ± 8.0) as compared with the control group (2.0 ± 5.0, P < .0001) and with the NSVT group (11.0 ± 8.0, P < .05).

CONCLUSIONS

The occurrence of ventricular arrhythmias of different degrees of severity correlates quantitatively with the extent of cardiac sympathetic denervation, but not with the extent of fibrosis, suggesting that myocardial sympathetic denervation plays a major role in triggering ventricular arrhythmia in CCC.

Increased arterial stiffness in children with congenital heart disease

Objective Central systolic blood pressure (SBP) is a measure of arterial stiffness and strongly associated with atherosclerosis and end-organ damage. It is a stronger predictor of cardiovascular events and all-cause mortality than peripheral SBP. In particular, for children with congenital heart disease, a higher central SBP might impose a greater threat of cardiac damage. The aim of the study was to analyse and compare central SBP in children with congenital heart disease and in healthy counterparts. Patients and methods Central SBP was measured using an oscillometric method in 417 children (38.9% girls, 13.0 ± 3.2 years) with various congenital heart diseases between July 2014 and February 2017. The test results were compared with a recent healthy reference cohort of 1466 children (49.5% girls, 12.9 ± 2.5 years). Results After correction for several covariates in a general linear model, central SBP of children with congenital heart disease was significantly increased (congenital heart disease: 102.1 ± 10.2 vs. healthy reference cohort: 100.4 ± 8.6, p < .001). The analysis of congenital heart disease subgroups revealed higher central SBP in children with left heart obstructions (mean difference: 3.6 mmHg, p < .001), transpositions of the great arteries after arterial switch (mean difference: 2.2 mmHg, p = .017) and univentricular hearts after total cavopulmonary connection (mean difference: 2.1 mmHg, p = .015) compared with the reference. Conclusion Children with congenital heart disease have significantly higher central SBP compared with healthy peers, predisposing them to premature heart failure. Screening and long-term observations of central SBP in children with congenital heart disease seems warranted in order to evaluate the need for treatment.

The potential role of iodine-123 metaiodobenzylguanidine imaging for identifying sustained ventricular tachycardia in patients with cardiomyopathy

Implantable cardioverter-defibrillators (ICDs) significantly reduce mortality in patients with depressed left ventricular ejection fraction (LVEF) and heart failure (HF). However, shortcomings of LVEF to accurately identify those at greatest risk of ventricular tachyarrhythmias have led to the pursuit of alternative means to refine qualification criteria for ICD implantation. It is well established that imaging the cardiac nervous system with¹²³I meta-iodobenzylguanidine (¹²³I-mIBG) provides incremental prognostic value in patients with HF beyond LVEF. Whether ¹²³I-mIBG will also play an important role for identifying and/or predicting sustained ventricular tachyarrhythmias in patients with cardiomyopathy and determining those who may benefit from ICD implantation is currently under investigation. Novel imaging approaches that pinpoint the site of ventricular arrhythmias and guide ventricular tachycardia ablation are presented.

QRS Complex Enlargement as a Predictor of Ventricular Arrhythmias in Patients Affected by Surgically Treated Tetralogy of Fallot: A Comprehensive Literature Review and Historical Overview

Tetralogy of Fallot (TOF) is a congenital heart disease frequently treated by surgical repair to relieve symptoms and improve survival. However, despite the performing of an optimal surgical repair, TOF patients are at times characterized by a poor long-term survival rate, likely due to cardiac causes such as ventricular arrhythmias, with subsequent sudden death. In the 80s it was irrefutably demonstrated that QRS prolongation ≥180 msec at basal electrocardiogram is a strong predictor for refining risk stratification for ventricular tachycardia in these patients. The aim of this research was to undertake a review of all studies conducted to assess the impact of QRS duration on the development of life-threatening ventricular arrhythmias in repaired TOF subjects.

Impaired carotid artery elastic function in patients with tetralogy of Fallot

Complex congenital heart diseases with abnormal formation of the aorticopulmonary septum are also associated with defective large artery elastogenesis. In the current study, we tested the hypothesis that carotid artery elastic function was impaired in patients with tetralogy of Fallot (ToF). The study included 45 Fallot-patients (male:female 27:18; age 21.0 ± 11.8 years) and 45 age- and gender-matched healthy control individuals. Carotid artery diameter, pulsatile distension, and intima-media thickness (IMT) were measured by echotracking device, and carotid blood pressure was determined using applanation tonometry. Carotid artery elasticity was characterized by compliance and distensibility coefficients, stiffness index β, and incremental elastic modulus. All carotid artery elastic parameters showed significant differences between groups. The compliance coefficient was 36%, and the distensibility coefficient was 33% smaller, whereas stiffness index β was 46% and incremental elastic modulus was 40% larger in Fallot-patients. Fallot-patients also had larger carotid artery IMT as compared to that of healthy individuals. Carotid artery is markedly stiffer in Fallot-patients suggesting that impaired elastogenesis is a component of the congenital abnormality. Increased large artery stiffness might contribute directly and indirectly (through impairment of baroreflex function) to the higher mortality found in ToF patients.

Heart rate variability in children with exercise-induced idiopathic ventricular arrhythmias

Ventricular arrhythmias (VAs) are common pediatric rhythm disorders requiring comprehensive laboratory evaluation. Although usually idiopathic, implying a benign character and favorable prognosis, the initial clinical approach is still not established in all cases. Considering their prognostic significance, exercise-induced (precipitated or aggravated) VAs usually require additional diagnostics, treatment, and follow-up. A number of reports have presented experimental and clinical evidence that increased sympathetic activity can initiate, or at least facilitate, VAs. Recent data highlight the relationship between exercise-induced idiopathic VAs (IVAs) and the long-term risk of cardiovascular death. The aim of this study was to assess the utility of heart rate variability (HRV) analysis as a noninvasive method for estimating autonomic nervous activity in children with exercise induced IVAs. The study included 42 children with IVAs, who were divided into two groups: children with exercise induced (precipitated or aggravated) IVAs and children with exercised-suppressed IVAs. Time-domain HRV parameters were analyzed from 24-h ambulatory electrocardiography recordings, and the majority of children underwent an exercise stress test using the McMaster protocol. The results of this study showed no significant changes in parasympathetic index, i.e., the square root of the mean of the sum of the squares of the differences between adjacent NN intervals (the length between two successive heartbeats) between the groups examined. On the other hand, we observed diminished time-domain values for the standard deviation of all adjacent NN intervals, as well as diminished time-domain values for standard deviation of the averages of NN intervals in all 5-min segments in the group of children with exercise-induced IVAs, implicating increased sympathetic activity in such individuals. HRV analysis could be a helpful diagnostic method, giving useful information regarding cardiac autonomic control in some children with exercise-induced IVAs.

Autonomic heart rate control at rest and during unloading of the right ventricle in repaired tetralogy of Fallot in adolescents

Arrhythmias in patients with repaired tetralogy of Fallot (ToF) might be due in part to altered autonomic heart rate control caused by altered right ventricle hemodynamics. This study investigated autonomic heart rate control in adolescents with ToF at rest and during unloading of the right ventricle. A total of 17 patients with ToF and 56 healthy controls aged 12 to 18 years underwent orthostatic stress with lower body negative pressure of -20 mm Hg. Heart rate, blood pressure, and stroke volume were recorded noninvasively. Indices of heart rate variability were computed in time and frequency domains. All patients with ToF also underwent cardiac magnetic resonance imaging, demonstrating pulmonary regurgitation and right ventricular dilation. At rest, heart rate variability indices of vagal heart rate control were nonsignificantly lower in the patients with ToF compared with controls. During lower body negative pressure, heart rate increased more in controls than patients with ToF (p <or=0.001). Further, most heart rate variability indices decreased in controls, but increased in patients with ToF (p <or=0.01 or p <or=0.001 for all variables), suggesting vagal activation in the patients with ToF. In conclusion, adolescents after ToF repair have fairly normal heart rate control at rest despite altered right ventricular hemodynamics. During unloading of the right ventricle, however, vagal heart rate control increases in the patients with ToF and decreases in the controls.

Monomorphic ventricular tachycardia related to Wolff-Parkinson-White surgery

Monomorphic ventricular tachycardia (MVT) is well described in patients who have had a ventricular scar due to repair of congenital heart disease. A 54-year-old woman presented with MVT 20 years after WPW surgery for a left-sided accessory pathway. The circuit was mapped to an area at the base of the left ventricle consistent with the incision described in the operation report. Entrainment confirmed the re-entrant circuit. Successful radiofrequency ablation was performed in a zone of slowed conduction consistent with the circuit isthmus. Any iatrogenic ventricular scar may form the substrate for MVT and be treated with standard electrophysiology techniques.

Heart failure in the adult patient with congenital heart disease

BACKGROUND

Adult survival is now the rule for most congenital heart defects. However, despite surgical "repair," heart failure remains a common long-term complication of congenital heart disease. Heart failure specialists are seeing an increasing number of patients with congenital defects as the underlying etiology of their heart failure.

METHODS AND RESULTS

Familiarity with the anatomy, physiology, and long-term sequelae of surgical correction are essential for providing care to this complex group of patients.

CONCLUSION

This review discusses the diagnosis, pathophysiology, and management of the adult congenital heart patient with concomitant heart failure.

Autonomic profile and arrhythmic risk stratification after surgical repair of tetralogy of Fallot

BACKGROUND

Severe ventricular arrhythmias represent one of the main causes of mortality after repair of tetralogy of Fallot. Their appearance is primarily caused by the large ventricular scar created by surgical intervention. However, the role of autonomic activity as a modulating factor should be considered. The aim of our study was to evaluate this activity in a low-risk group of patients operated on for TOF and its correlation with the occurrence of sustained ventricular tachycardia.

METHODS AND RESULTS

The study group included 38 patients with a mean age of 31 +/- 10 years, selected out of 76 subjects operated on for total correction of tetralogy of Fallot. After a mean interval of 21.9 +/- 6 years from surgical procedure, they underwent electrocardiography, echocardiography, and time domain heart rate variability (HRV) analysis obtained by 24-hour Holter monitoring. Thirty-five healthy subjects comprised the control group for HRV analysis. During a mean follow-up of 6.2 +/- 3 years, 8 patients experienced episodes of sustained ventricular tachycardia. Among different HRV parameters, the standard deviation of all normal beat intervals showed a significant reduction in this group of patients (91.7 +/- 19 versus 133.4 +/- 46, P < .02). Echocardiographic examination demonstrated an increased left ventricular end diastolic volume (85.6 +/- 55 versus 61.3 +/- 13 mL/m(2), P < .05) and a reduced left ventricle ejection fraction (53.9 +/- 9 versus 61.0 +/- 6 %, P < .01) in arrhythmic patients. QRS duration was similar in patients with or without sustained ventricular tachycardia.

CONCLUSIONS

Patients after surgical correction of tetralogy of Fallot, considered to be at low risk, showed a significant incidence of severe ventricular arrhythmias. HRV analysis seems to be a useful method for identifying arrhythmic patients, and the standard deviation of all normal beat intervals appears to be the more helpful index.

Role of invasive and noninvasive testing in risk stratification of sudden cardiac death in children and young adults: an electrophysiologic perspective

Sudden cardiac death is a rare, but devastating, event in the young population. Arrhythmia is the mechanism of death in many cases. In addition to clinical history, noninvasive and invasive tests can be used to identify patients who are at risk. Although these tools are not perfect, they can prove valuable if used in proper clinical circumstances. An overview of these tests is presented.

Predicting late sudden death from ventricular arrhythmia in adults following surgical repair of tetralogy of Fallot

Tetralogy of Fallot was the first complex congenital cardiac defect to undergo open repair. The life expectancy and quality of life of those surviving surgery is now good, although late survival is compromised by the occurrence of sudden death. The emergence of successful methods for both the prevention of arrhythmias (including valve replacements and electrophysiological ablation) and the treatment of arrhythmias when they occur (including implantable defibrillators), has meant the identification of those at risk is of even greater importance. This paper reviews the predictive methods currently available to the practising physician caring for these increasingly common patients.