Andrew J. Powell

Ventricular size and function assessed by cardiac MRI predict major adverse clinical outcomes late after tetralogy of Fallot repair

Background: Factors associated with impaired clinical status in a cross-sectional study of patients with repaired tetralogy of Fallot (TOF) have been reported previously. Objectives: To determine independent predictors of major adverse clinical outcomes late after TOF repair in the same cohort during follow-up evaluated by cardiac magnetic resonance (CMR). Methods: Clinical status at latest follow-up was ascertained in 88 patients (median time from TOF repair to baseline evaluation 20.7 years; median follow-up from baseline evaluation to most recent follow-up 4.2 years). Major adverse outcomes included (a) death; (b) sustained ventricular tachycardia; and (c) increase in NYHA class to grade III or IV. Results: 22 major adverse outcomes occurred in 18 patients (20.5%): death in 4, sustained ventricular tachycardia in 8, and increase in NYHA class in 10. Multivariate analysis identified right ventricular (RV) end-diastolic volume Z ⩾7 (odds ratio (OR) = 4.55, 95% confidence interval (CI) 1.10 to 18.8, p = 0.037) and left ventricular (LV) ejection fraction <55% (OR = 8.05, 95% CI 2.14 to 30.2, p = 0.002) as independent predictors of outcome with an area under the receiver operator characteristic curve of 0.850. LV ejection fraction could be replaced by RV ejection fraction <45% in the multivariate model. QRS duration ⩾180 ms also predicted major adverse events but correlated with RV size. Conclusions: In this cohort, severe RV dilatation and either LV or RV dysfunction assessed by CMR predicted major adverse clinical events. This information may guide risk stratification and therapeutic interventions.

Gadolinium-Enhanced 3-Dimensional Magnetic Resonance Angiography of Pulmonary Blood Supply in Patients With Complex Pulmonary Stenosis or Atresia Comparison With X-Ray Angiography

Background—In patients with complex pulmonary stenosis or atresia, a detailed delineation of all sources of pulmonary blood supply is necessary for planning surgical and transcatheter procedures and usually requires diagnostic cardiac catheterization. The goals of this study were to determine whether gadolinium-enhanced 3D magnetic resonance angiography (MRA) can provide a noninvasive alternative to diagnostic catheterization and to compare MRA and x-ray angiography measurements of pulmonary arteries and aortopulmonary collaterals (APCs). Methods and Results—Thirty-two patients with pulmonary stenosis or atresia (median age: 4.7 years, range: 1 day to 46.9 years) underwent both MRA and cardiac catheterization (median time: 1 month). Diagnoses included tetralogy of Fallot (TOF) with pulmonary atresia (n=13), TOF with pulmonary stenosis (n=4), post-Fontan palliation (n=5), and other complex congenital heart disease (n=10). Compared with catheterization and surgical observations, MRA had a 100% sensitivity and specificity for the diagnosis of main (n=10) and branch pulmonary artery (PA) stenosis or hypoplasia (n=38), as well as absent (n=5) or discontinuous (n=4) branch PAs. All 48 major APCs diagnosed by catheterization were correctly diagnosed by MRA. Three additional APCs were diagnosed by MRA but not by catheterization. The mean difference between MRA and catheterization measurements of 33 pulmonary vessel diameters was 0.5±1.5 mm, with a mean interobserver difference of 0.4±1.5 mm. Conclusions—Gadolinium-enhanced 3D MRA is a fast and accurate technique for delineation of all sources of pulmonary blood supply in patients with complex pulmonary stenosis and atresia and can be considered a noninvasive alternative to diagnostic catheterization with x-ray angiography.

Evaluation of Regional Differences in Right Ventricular Systolic Function by Acoustic Quantification Echocardiography and Cine Magnetic Resonance Imaging

BACKGROUND Accurate quantitative evaluation of right ventricular (RV) function has been limited by its complex structural geometry. Although embryological and anatomic observations suggest that the RV is composed of 2 distinct components, the RV sinus and infundibulum, most studies on RV dimensions and function viewed it as a single chamber. This study was designed to determine the volumes, relative contribution to global systolic function, and temporal course of contraction and relaxation of the RV sinus and infundibulum. METHODS AND RESULTS Thirty-one individuals without heart disease (aged 1 month to 17 years, 16 boys and 15 girls) participated in this study. Instantaneous area over time, its derivatives, and the temporal course of contraction and relaxation were studied by acoustic quantification echocardiography and phonocardiography in 20 individuals. Global and regional RV volumes and ejection fraction were determined by cine MRI in 11 individuals. The RV sinus made up 81+/-6% of the combined RV end-diastolic volume and 87+/-4% of the combined stroke volume. The infundibulum accounted for the remaining 19+/-6% and 13+/-4%, respectively (P<0.0001). Compared with the infundibulum, the extent of RV sinus fiber shortening was significantly greater: for ejection fraction (56+/-11% versus 38+/-13%, P<0.001), fractional area change (42+/-14% versus 28+/-9%, P<0.0001), and dA/dt (27+/-17% versus 13+/-6%, P<0.0001). Analysis of temporal course of contraction and relaxation (expressed as percentage of the cardiac cycle to adjust for differences in heart rate) showed that the infundibulum follows the RV sinus: onset of contraction 53%+/-14 versus 19+/-11% of systole, time to peak systole 115+/-16% versus 97+/-19% (P< or =0.01), indicating a peristalsis-like pattern of contraction and relaxation. CONCLUSIONS The results of this study demonstrate significant regional differences between the sinus and infundibulum components of the RV with regard to contribution to stroke volume, extent of fiber shortening, and sequence of mechanical activation. These data from normal individuals can be used in future research on RV function in pathological conditions.

Effects of Regional Dysfunction and Late Gadolinium Enhancement on Global Right Ventricular Function and Exercise Capacity in Patients With Repaired Tetralogy of Fallot

Background— The underlying mechanisms that contribute to global right ventricular (RV) dysfunction in patients with repaired tetralogy of Fallot are incompletely understood. We therefore sought to quantify regional RV abnormalities and to determine the relationship of these to global RV function and exercise capacity. Methods and Results— Clinical and cardiac magnetic resonance data from 62 consecutive patients with repaired tetralogy of Fallot were analyzed (median age at follow-up 23 years [limits 9 to 67 years]). Using cardiac magnetic resonance data, 3D RV endocardial surface models were reconstructed from segmented contours, and a correspondence between end diastole and end systole was computed with a novel algorithm. Regional RV abnormalities were quantified and expressed as segmental ejection fraction, spatial extent of dyskinetic area, displacement of dyskinetic area, and score of extent of late gadolinium enhancement. Regional abnormalities of function and hyperenhancement were greatest in the RV outflow tract (RVOT). These regional RVOT abnormalities correlated with global RV ejection fraction: RVOT ejection fraction r=0.64, P<0.0001; RVOT dyskinetic area r=−0.51, P<0.0001; RVOT displacement of dyskinetic area r=−0.49, P<0.0001; and RVOT late gadolinium enhancement score r=−0.33, P=0.01. Peak oxygen consumption during exercise correlated best with RVOT ejection fraction (r=0.56, P=0.0002) compared with the remainder of the RV (r=0.35, P=0.03). The only cardiac magnetic resonance variable independently predictive of aerobic capacity was RVOT ejection fraction (P=0.02). Conclusion— A greater extent of regional abnormalities in the RVOT adversely affects global RV function and exercise capacity after tetralogy of Fallot repair. These regional measures may have important implications for patient management, including RVOT reconstruction, at the time of pulmonary valve replacement.

Reproducibility of MRI measurements of right ventricular size and function in patients with normal and dilated ventricles

To determine the inter‐ and intraobserver reproducibility of cardiac magnetic resonance (CMR)‐derived measurements of right ventricular (RV) mass, volume, and function in patients with normal and dilated ventricles.

Phase-Velocity Cine Magnetic Resonance Imaging Measurement of Pulsatile Blood Flow in Children and Young Adults: In Vitro and In Vivo Validation

Abstract. Quantification of blood flow in vessels provides valuable information that aids management decisions in a variety of cardiac conditions. Current flow measurement techniques are often limited by accuracy, time resolution, convenience, or anatomic localization. This study examined the accuracy of a commercially available phase-velocity cine magnetic resonance imaging (PVC MRI) technique to quantify flow rate in a pulsatile flow phantom. In addition, the equivalence of PVC MRI measurements of pulmonary and systemic flow was evaluated in children and adults without any pathologic shunt. Using a pulsatile flow phantom, volume flow rates measured by PVC MRI were compared to those by a transit-time ultrasound flowmeter over a range of flow rates (1.25–3.5 L/min, 13 trials). Close agreement was found between these techniques (y= 1.02x− 0.02, r= 0.99, Bland–Altman bias =−0.045 L/min, 95% limits of agreement =−0.19–0.10 L/min). Twenty subjects (median age 12.8 years, range 0.7–49 years) with no pathologic shunt underwent PVC MRI measurement of blood flow in the main pulmonary artery (Qp) and the ascending aorta (Qs). Data processing time for each location was 20 minutes. The Qp/Qs ratio closely approximated unity (mean = 0.99, SD = 0.10, range 0.85–1.19). Interobserver agreement was excellent (Bland–Altman bias = 0.09 L/min, 95% limits of agreement = 0.15–0.33 L/min). PVC MRI is an accurate technique to quantify pulsatile blood flow at a specific location. It can be used to noninvasively calculate Qp and Qs under normal flow conditions.

Contemporary predictors of death and sustained ventricular tachycardia in patients with repaired tetralogy of Fallot enrolled in the INDICATOR cohort

Objective Patients with repaired tetralogy of Fallot (TOF) experience increased rates of mortality and morbidity in adulthood. This study was designed to identify risk factors for death and ventricular tachycardia (VT) in a large contemporary cohort of patients with repaired TOF. Methods Subjects with repaired TOF from four large congenital heart centres in the USA, Canada and Europe were enrolled. Clinical, ECG, exercise, cardiac magnetic resonance (CMR) and outcome data were analysed. Results Of the 873 patients (median age 24.4 years), 32 (3.7%) reached the primary outcome (28 deaths, 4 sustained VT; median age at outcome 38 years; median time from CMR to outcome 1.9 years). Cox proportional-hazards regression identified RV mass-to-volume ratio ≥0.3 g/mL (HR, 5.04; 95% CI 2.3 to 11.0; p<0.001), LV EF z score<−2.0 (HR, 3.34; 95% CI 1.59 to 7.01; p=0.001), and history of atrial tachyarrhythmia (HR, 3.65; 95% CI 1.75 to 7.62; p=0.001) as outcome predictors. RV dysfunction was predictive of the outcome similar to LV dysfunction. In subgroup analysis of 315 subjects with echocardiographic assessment of RV systolic pressure, higher pressure (HR 1.39; 95% CI 1.19 to 1.62; p<0.001) was associated with death and sustained VT independent of RV hypertrophy and LV dysfunction. Conclusions RV hypertrophy, ventricular dysfunction and atrial tachyarrhythmias are predictive of death and sustained VT in adults with repaired TOF. These findings may inform risk stratification and the design of future therapeutic trials.

Gadolinium-enhanced three-dimensional magnetic resonance angiography of pulmonary and systemic venous anomalies

OBJECTIVE The goal of this study was to evaluate the diagnostic value of gadolinium (Gd)-enhanced three-dimensional (3D) magnetic resonance angiography (MRA) in patients with congenital and acquired anomalies of the pulmonary and systemic veins. BACKGROUND Gadolinium-enhanced 3D MRA is a fast magnetic resonance imaging technique that has shown great promise in the evaluation of large and medium-sized arteries. However, its application to venous anomalies has not been studied in detail. METHODS The study retrospectively analyzed all patients who underwent Gd-enhanced 3D MRA examination from January 1998 through January 2001, were diagnosed with anomalies of the pulmonary or systemic veins and had additional diagnostic data available for comparison with the MRA findings. RESULTS Sixty-one patients (age 1 day to 60 years) were included. Image acquisition was completed in 29 +/- 6.9 s. Pulmonary venous anomalies were found in 37 patients, systemic venous anomalies in 17 patients and both pulmonary and systemic venous anomalies in 7 patients. Compared with available diagnostic information by other modalities, all known or suspected venous anomalies were imaged by 3D MRA. In three patients, catheterization did not detect anomalies of the pulmonary veins that were subsequently diagnosed by MRA. The 3D MRA diagnoses were followed by 10 interventional catheterization procedures and 15 operations. In 74% of patients, 3D MRA either diagnosed previously unsuspected venous anomalies (28%) or added new clinically important information (46%). The mechanism of pulmonary vein compression in eight patients was determined by MRA but not by other imaging modalities. Using a five-level grading system for MRA image quality (1 = nondiagnostic; 5 = excellent), the average grade was 4.6 +/- 0.6, with a 0.28 +/- 0.6 mean grade difference between two independent observers. CONCLUSIONS Gadolinium-enhanced 3D MRA is capable of rapidly and accurately diagnosing a wide spectrum of pulmonary and systemic venous anomalies and is a useful noninvasive alternative to diagnostic catheterization.

Prolongation of RV-PA conduit life span by percutaneous stent implantation : intermediate-term results

BACKGROUND Right ventricle-to-pulmonary artery (RV-PA) homografts and bioprosthetic conduits are commonly used to palliate various types of complex congenital heart disease. These conduits frequently develop progressive obstruction and require surgical replacement. This report reviews our experience implanting balloon-expandable stents to relieve conduit obstruction and delay reoperation. METHODS AND RESULTS A retrospective review identified 44 patients who underwent placement of 48 stents in obstructed RV-PA conduits. Median patient age was 6.9 years (range, 7 months to 30 years), and median follow-up time was 14.2 months (range, 0 to 48 months). Stent implantation initially decreased the RV-PA pressure gradient from 61.0 +/- 16.9 to 29.7 +/- 11.9 mm Hg (P < or = .001) and the right ventricular-to-systemic arterial pressure ratio from 0.92 +/- 0.17 to 0.63 +/- 0.20 (P < or = .001). The diameter of the stenotic region expanded from 9.3 +/- 3.5 to 12.3 +/- 3.3 mm in the anteroposterior view (P < or = .001) and from 6.6 +/- 2.9 to 10.9 +/- 2.5 mm in the lateral view (P < or = .001). During the follow-up period, 2 patients had their stents redilated, 7 had additional conduit stents deployed, and 14 underwent surgical replacement of their conduits. Actuarial freedom from conduit reoperation was 65% at 30 months postprocedure. Seven patients were found to have fractured stents on follow-up, suggesting an important role for external compressive forces in conduit failure. Recatheterization in 16 patients a median of 11.8 months (3 to 48 months) postprocedure demonstrated hemodynamic evidence of recurrent obstruction despite sustained enlargement at the previously stented sites. Complications included stent displacement (n = 1), bacterial endocarditis (n = 1), and false aneurysm formation (n = 1). One patient died awaiting conduit replacement surgery. CONCLUSIONS Stent implantation in obstructed RV-PA conduits results in significant immediate hemodynamic and angiographic improvement. In a subgroup of patients, the procedure prolongs conduit life span by several years and increases the interval between conduit reoperations. Recurrent obstruction is caused by external compression and progressive stenosis outside the stented region.

Cardiovascular outcomes after the arterial switch operation for D-transposition of the great arteries.

Background— Data regarding long-term outcomes after the arterial switch operation for D-transposition of the great arteries are scarce. Methods and Results— A single-institution retrospective cohort study was conducted to assess cardiovascular outcomes after an arterial switch operation between 1983 and 1999. Patients without follow-up visits within 3 years were contacted and secondary sources of information obtained. Overall, 400 patients, 154 (38.3%) with a ventricular septal defect, 238 (59.5%) with an intact septum, and 9 (2.3%) with a Taussig-Bing anomaly, were followed for a median of 18.7 years. In perioperative survivors, overall and arrhythmia-free survival rates at 25 years were 96.7±1.8% and 96.6±0.1%, respectively. Late mortality was predominantly a result of sudden deaths and myocardial infarction. At 25 years, 75.5±2.5% remained free from surgical or catheter-based reintervention. Freedom from an adverse cardiovascular event was 92.9±1.9% at 25 years. Independent predictors were a single right coronary artery (hazard ratio, 4.58; 95% confidence interval, 1.32-15.90), P=0.0166) and postoperative heart failure (hazard ratio, 6.93; 95% confidence interval, 1.57-30.62; P=0.0107). At last follow-up, the left ventricular ejection fraction was 60.3±8.9%, 97.3% had class I symptoms, and 5.2% obstructive coronary artery disease. Peak oxygen uptake was 35.1±7.6 mL/kg/min (86.1±15.1% predicted), with a chronotropic index <80% in 34.2%. At least moderate neoaortic and pulmonary regurgitation were present in 3.4% and 6.6%, respectively, and more than mild neoaortic and pulmonary stenosis in 3.2% and 10.3%. Conclusions— Long-term and arrhythmia-free survival is excellent after arterial switch operation. Although sequelae include chronotropic incompetence and neoaortic, pulmonary, and coronary artery complications, most patients maintain normal systolic function and exercise capacity.