Declining Cardiopulmonary Exercise Capacity Is Not Associated with Worsening Systolic Systemic Ventricular Dysfunction in Adults with Transposition of Great Arteries after Atrial Switch Operation

Long-Term Outcomes After Atrial Switch Operation for Transposition of the Great Arteries

BACKGROUND

For patients with d-loop transposition of the great arteries (d-TGA) with a systemic right ventricle after an atrial switch operation, there is a need to identify risks for end-stage heart failure outcomes.

OBJECTIVES

The authors aimed to determine factors associated with survival in a large cohort of such individuals.

METHODS

This multicenter, retrospective cohort study included adults with d-TGA and prior atrial switch surgery seen at a congenital heart center. Clinical data from initial and most recent visits were obtained. The composite primary outcome was death, transplantation, or mechanical circulatory support (MCS).

RESULTS

From 1,168 patients (38% female, age at first visit 29 ± 7.2 years) during a median 9.2 years of follow-up, 91 (8.8% per 10 person-years) met the outcome (66 deaths, 19 transplantations, 6 MCS). Patients experiencing sudden/arrhythmic death were younger than those dying of other causes (32.6 ± 6.4 years vs 42.4 ± 6.8 years; P < 0.001). There was a long duration between sentinel clinical events and end-stage heart failure. Age, atrial arrhythmia, pacemaker, biventricular enlargement, systolic dysfunction, and tricuspid regurgitation were all associated with the primary outcome. Independent 5-year predictors of primary outcome were prior ventricular arrhythmia, heart failure admission, complex anatomy, QRS duration >120 ms, and severe right ventricle dysfunction based on echocardiography.

CONCLUSIONS

For most adults with d-TGA after atrial switch, progress to end-stage heart failure or death is slow. A simplified prediction score for 5-year adverse outcome is derived to help identify those at greatest risk.

Heart rate response during exercise predicts exercise tolerance in adults with transposition of the great arteries and atrial switch operation

BACKGROUND

To assess the relationship between heart rate response and exercise tolerance in adults with systemic right ventricle (sRV) after atrial switch repair for Transposition of the Great Artery (TGA) in addition to other physiological parameters.

METHODS

All patients with a sRV after atrial switch repair for TGA followed in our institution between June 2015 and April 2018 who underwent cardiopulmonary exercise testing (CPET) were analyzed. Cardiac imaging performed within a six-month time period of the CPET were also collected. Chronotropic incompetence was defined as the inability to achieve 80% of age-predicted maximal heart rate reserve (HRR) and <62% on a beta-blocker regimen. Patient characteristics were assessed according to tertiles of the percentage of predicted pVO2 (%ppVO2).

RESULTS

We studied 70 patients (mean of age 32.4 ± 7.6 years old, 51 males). Mean peak oxygen uptake was 21.5 ± 5.8 mL/kg/min, corresponding to a %ppVO2 of 57 ± 14.1% while mean VE/VCO2 slope was 37.1 ± 8.2. There was a trend toward more exaggerated hyperventilation in patient with lower pVO2. Mean age-adjusted HRR was 68.5 ± 19%. Chronotropic incompetence was observed in 65.7% and was correlated with %ppVO2 (r = 0.482; p < 0.001) as physical training evaluated with Ventilatory Anaerobic threshold (r = 0.571; p < 0.001), while no difference was found based on respiratory parameters. No echocardiographic or Magnetic Resonance Imaging parameters assessing sRV systolic function at rest were correlated with %ppVO2.

CONCLUSIONS

Exercise limitation is related to the inability to increase cardiac output during exercise and is notably due to the degree of chronotropic incompetence.

Myocardial Deformation in the Systemic Right Ventricle: Strain Imaging Improves Prediction of the Failing Heart

BACKGROUND

Predicting heart failure events in patients with a systemic right ventricle (sRV) due to transposition of the great arteries (TGA) is important for timely intensification of follow-up. This study assessed the value of strain compared with currently used parameters as predictor for heart failure-free survival in patients with sRV.

METHODS

In participants of a multicentre trial, speckle-tracking echocardiography (STE) was performed to assess global longitudinal strain (GLS), mechanical dispersion (MD), and postsystolic shortening (PSS). Cox regression was used to determine the association of STE parameters with the combined end point of progression of heart failure and death, compared with cardiovascular magnetic resonance (CMR) and computed tomography (CT) derived parameters.

RESULTS

Echocardiograms of 60 patients were analyzed (mean age 34 ± 11 years, 65% male, 35% congenitally corrected TGA). Mean GLS was -13.5 ± 2.9%, median MD was 49 (interquartile range [IQR] 30-76) ms, and 14 patients (23%) had PSS. During a median 8 (IQR 7-9) years, 15 patients (25%) met the end point. GLS, MD, and PSS were all associated with heart failure-free survival in univariable analysis. After correction for age, only GLS (optimal cutoff > -10.5%) and CMR/CT-derived sRV ejection fraction (optimal cutoff < 30%) remained associated with heart failure-free survival: hazard ratio (HR) 8.27, 95% confidence interval (CI) 2.50-27.41 (P < 0.001), and HR 4.34, 95% CI 1.48-12.74 (P = 0.007), respectively). Combining GLS and ejection fraction improved prediction, with patients with both GLS > -10.5% and sRV ejection fraction < 30% at highest risk (HR 19.69, 95% CI 4.90-79.13; P < 0.001).

CONCLUSIONS

The predictive value of GLS was similar to that of CMR/CT-derived ejection fraction. The combination of GLS and ejection fraction identified patients at highest risk of heart failure and death. Easily available STE parameters can be used to guide follow-up intensity and can be integrated into future risk prediction scores.

Myocardial fibrosis and its relation to adverse outcome in transposition of the great arteries with a systemic right ventricle

BACKGROUND

Myocardial dysfunction has been implicated in gradual heart failure in transposition of the great arteries (TGA) with a systemic right ventricle (RV). Fibrosis can be assessed using the extracellular volume fraction (ECV). Our aim was to measure ECV and determine its associations with clinical findings and outcomes.

METHODS

We prospectively measured ECV in systemic RV subjects (either D-loop after atrial switch or L-loop) and healthy controls. T₁ measurements for a single mid-ventricular short-axis plane before and 3, 7, and 15 min after gadolinium contrast were used to quantify systemic ventricular ECV. Individuals with elevated ECV were compared to those without.

RESULTS

In 53 TGA subjects (age 34.6 ± 10.3 years, 41% female) the mean ECV for the systemic RV (28.7 ± 4.4%) was significantly higher than the left ventricle in 22 controls (26.1 ± 2.8%, P = 0.0104). Those with an elevated ECV (n = 15, 28.3%) had a higher b-type natriuretic peptide (BNP) (P < 0.011) and a longer 6-min walk distance (P = 0.021), but did not differ by age, arrhythmia history, ventricular volume, function, or circulating collagen byproducts. At follow-up (median 4.4 years), those experiencing major cardiovascular endpoints (new arrhythmia, arrhythmia device, heart failure hospitalization, listing for transplantation, mechanical support, or cardiovascular death, n = 14) had a higher ECV. ECV, age, and BNP were independent predictors of cardiac events in Cox-proportional hazard models.

CONCLUSIONS

Myocardial fibrosis is common in the systemic RV and associated with a higher BNP. Elevated CMR-derived ECV was associated with adverse clinical outcome. The findings suggest a role of diffuse myocardial fibrosis in clinical deterioration of the systemic RV.

Right ventricular systolic dysfunction at rest is not related to decreased exercise capacity in patients with a systemic right ventricle

BACKGROUND

To evaluate the relationship between right ventricular (RV) systolic dysfunction at rest and reduced exercise capacity in patients with a systemic RV (sRV).

METHODS

All patients with congenitally corrected transposition of the great arteries (ccTGA) or complete TGA after atrial switch (TGA-Mustard/Senning) followed in our institution between July 2011 and September 2017 who underwent cardiac imaging within a six-month time period of cardiopulmonary exercise testing (CPET) were analyzed. We assessed sRV systolic function with TAPSE and fractional area change on echocardiogram and, if possible, with ejection fraction, global longitudinal and circumferential strain on cardiac magnetic resonance (CMR) imaging.

RESULTS

We studied 105 patients with an sRV (median age 34 [IQR 28-42] years, 29% ccTGA and 71% TGA-Mustard/Senning) of which 39% had either a pacemaker (n = 17), Eisenmenger physiology (n = 6), severe systemic atrioventricular valve regurgitation (n = 14), or peak exercise arterial oxygen saturation < 92% (n = 17). Most patients were asymptomatic or mildly symptomatic (NYHA class I/II/III in 71/23/6%). Sixty-four percent had evidence of moderate or severe sRV dysfunction on cardiac imaging. Mean peak oxygen uptake (pVO2) was 24.1 ± 7.4 mL/kg/min, corresponding to a percentage of predicted pVO2 (%ppVO2) of 69 ± 17%. No parameter of sRV systolic function as evaluated on echocardiography (n = 105) or CMR (n = 46) was correlated with the %ppVO2, even after adjusting for associated cardiac defects or pacemakers.

CONCLUSIONS

In adults with an sRV, there is no relation between echocardiographic or CMR-derived sRV systolic function parameters at rest and peak oxygen uptake. Exercise imaging may be superior to evaluate whether sRV contractility limits exercise capacity.

Risk for sleep-disordered breathing in adults after atrial switch repairs for d-looped transposition of the great arteries

Although sleep-disordered breathing has been extensively studied in patients with left-ventricular dysfunction, little is known of its prevalence in adults with congenital heart disease. Patients with d-looped transposition of the great arteries (d-TGA) who have undergone atrial switch procedures often develop progressive heart failure. The objective of this study was to determine the prevalence of patients at risk for sleep-disordered breathing in adults with d-TGA and atrial switch procedures compared with a control population. Thirty-two patients with d-TGA (66 % males, median age 31) were compared with 32 healthy controls. Baseline demographics and clinical characteristics were documented. The snoring, tiredness during daytime, observed apnea, and high blood pressure (STOP) questionnaire was used to identify subjects at risk for obstructive sleep apnea (OSA). There was no difference in baseline demographics between subjects and controls. For the STOP questionnaire, 14 subjects with d-TGA had scores predictive of OSA compared with three in the control group (44 vs. 9 %, p = 0.0038). There was no difference in functional status between d-TGA patients with or without OSA. There is a greater prevalence of risk for sleep disordered breathing in adults with d-TGA compared with controls. Further prospective investigation with sleep studies will be valuable to confirm these findings.