Vivek Muthurangu

Percutaneous Pulmonary Valve Implantation in Humans Results in 59 Consecutive Patients

Background—Right ventricular outflow tract (RVOT) reconstruction with valved conduits in infancy and childhood leads to reintervention for pulmonary regurgitation and stenosis in later life. Methods and Results—Patients with pulmonary regurgitation with or without stenosis after repair of congenital heart disease had percutaneous pulmonary valve implantation (PPVI). Mortality, hemodynamic improvement, freedom from explantation, and subjective and objective changes in exercise tolerance were end points. PPVI was performed successfully in 58 patients, 32 male, with a median age of 16 years and median weight of 56 kg. The majority had a variant of tetralogy of Fallot (n=36), or transposition of the great arteries, ventricular septal defect with pulmonary stenosis (n=8). The right ventricular (RV) pressure (64.4±17.2 to 50.4±14 mm Hg, P<0.001), RVOT gradient (33±24.6 to 19.5±15.3, P<0.001), and pulmonary regurgitation (PR) (grade 2 of greater before, none greater than grade 2 after, P<0.001) decreased significantly after PPVI. MRI showed significant reduction in PR fraction (21±13% versus 3±4%, P<0.001) and in RV end-diastolic volume (EDV) (94±28 versus 82±24 mL · beat−1 · m−2, P<0.001) and a significant increase in left ventricular EDV (64±12 versus 71±13 mL · beat−1 · m−2, P=0.005) and effective RV stroke volume (37±7 versus 42±9 mL · beat−1 · m−2, P=0.006) in 28 patients (age 19±8 years). A further 16 subjects, on metabolic exercise testing, showed significant improvement in &OV0312;o2max (26±7 versus 29±6 mL · kg−1 · min−1, P<0.001). There was no mortality. Conclusions—PPVI is feasible at low risk, with quantifiable improvement in MRI-defined ventricular parameters and pulmonary regurgitation, and results in subjective and objective improvement in exercise capacity.

Percutaneous pulmonary valve implantation impact of evolving technology and learning curve on clinical outcome

Background— Percutaneous pulmonary valve implantation was introduced in the year 2000 as a nonsurgical treatment for patients with right ventricular outflow tract dysfunction. Methods and Results— Between September 2000 and February 2007, 155 patients with stenosis and/or regurgitation underwent percutaneous pulmonary valve implantation. This led to significant reduction in right ventricular systolic pressure (from 63±18 to 45±13 mm Hg, P<0.001) and right ventricular outflow tract gradient (from 37±20 to 17±10 mm Hg, P<0.001). Follow-up ranged from 0 to 83.7 months (median 28.4 months). Freedom from reoperation was 93% (±2%), 86% (±3%), 84% (±4%), and 70% (±13%) at 10, 30, 50, and 70 months, respectively. Freedom from transcatheter reintervention was 95% (±2%), 87% (±3%), 73% (±6%), and 73% (±6%) at 10, 30, 50, and 70 months, respectively. Survival at 83 months was 96.9%. On time-dependent analysis, the first series of 50 patients (log-rank test P<0.001) and patients with a residual gradient >25 mm Hg (log-rank test P=0.01) were associated with a higher risk of reoperations. Conclusions— Percutaneous pulmonary valve implantation resulted in the ability to avoid surgical right ventricular outflow tract revision in the majority of cases. This procedure might reduce the number of operations needed over the total lifetime of patients with right ventricle–to–pulmonary artery conduits.

Evaluation of Techniques for the Quantification of Myocardial Scar of Differing Etiology Using Cardiac Magnetic Resonance

OBJECTIVES The aim of this study was to compare the reproducibility of 7 late gadolinium enhancement (LGE) quantification techniques across 3 conditions in which LGE is known to be important: acute myocardial infarction (AMI), chronic myocardial infarction (CMI), and hypertrophic cardiomyopathy (HCM). BACKGROUND LGE by cardiac magnetic resonance is the gold-standard technique for assessing myocardial scar. No consensus exists on the best method for its quantification, and research in this area is scant. Techniques include manual quantification, thresholding by 2, 3, 4, 5, or 6 SDs above remote myocardium, and the full width at half maximum (FWHM) technique. To date, LGE has been linked to outcome in 3 conditions: AMI, CMI, and HCM. METHODS Sixty patients with 3 LGE etiologies (AMI, n = 20; CMI, n = 20; HCM, n = 20) were scanned for LGE. LGE volume was quantified using the 7 techniques. Mean LGE volume, interobserver and intraobserver reproducibility, and impact on sample size were assessed. RESULTS LGE volume varied significantly with the quantification method used. There was no statistically significant difference between LGE volume by the FWHM, manual, and 6-SD or 5-SD techniques. The 2-SD technique generated LGE volumes up to 2 times higher than the FWHM, 6-SD, and manual techniques. The reproducibility of all techniques was worse in HCM than AMI or CMI. The FWHM technique was the most reproducible in all 3 conditions compared with any other method (p < 0.001). Use of the FWHM technique for LGE quantification in paired analysis would lead to at least a 60% reduction in required sample size compared with any other method. CONCLUSIONS Regardless of the disease under study, the FWHM technique for LGE quantification gives LGE volume mean results similar to manual quantification and is statistically the most reproducible, reducing required sample sizes by up to one-half.

Novel Method of Quantifying Pulmonary Vascular Resistance by Use of Simultaneous Invasive Pressure Monitoring and Phase-Contrast Magnetic Resonance Flow

Background—Pulmonary vascular resistance (PVR) quantification is important in the treatment of children with pulmonary hypertension. The Fick principle, used to quantify pulmonary artery flow, may be a flawed technique. We describe a novel method of PVR quantification by the use of magnetic resonance (MR) flow data and invasive pressure measurements. Methods and Results—In 24 patients with either suspected pulmonary hypertension or congenital heart disease requiring preoperative assessment, PVR was calculated by the use of simultaneously acquired MR flow and invasive pressure measurements (condition 1). In 19 of the 24 patients, PVR was also calculated at 20 ppm nitric oxide +30% (condition 2) and at 20 ppm nitric oxide +100% oxygen (condition 3), with the use of the MR method. This method proved safe and feasible in all patients. In 15 of 19 patients, PVR calculated by Fick flow was compared with the MR method. At condition 1, Bland-Altman analysis revealed a bias of 2.3% (MR > Fick) and limits of agreement of 50.2% to −45.5%. At condition 2, there was poorer agreement (bias was 28%, and the limits of agreement were 151.3% to 95.2%). At condition 3, there was very poor agreement (bias was 54.2%, and the limits of agreement were 174.4% to −66.0%). Conclusions—We have demonstrated the feasibility of using simultaneous invasive pressure measurements and MR flow data to measure PVR in humans.

Whole-heart cine MRI using real-time respiratory self-gating

Two‐dimensional (2D) breath‐hold cine MRI is used to assess cardiac anatomy and function. However, this technique requires cooperation from the patient, and in some cases the scan planning is complicated. Isotropic nonangulated three‐dimensional (3D) cardiac MR can overcome some of these problems because it requires minimal planning and can be reformatted in any plane. However, current methods, even those that use undersampling techniques, involve breath‐holding for periods that are too long for many patients. Free‐breathing respiratory gating sequences represent a possible solution for realizing 3D cine imaging. A real‐time respiratory self‐gating technique for whole‐heart cine MRI is presented. The technique enables assessment of cardiac anatomy and function with minimum planning or patient cooperation. Nonangulated isotropic 3D data were acquired from five healthy volunteers and then reformatted into 2D clinical views. The respiratory self‐gating technique is shown to improve image quality in free‐breathing scanning. In addition, ventricular volumetric data obtained using the 3D approach were comparable to those acquired with the conventional multislice 2D approach. Magn Reson Med 57:606–613, 2007.

Early Versus Late Functional Outcome After Successful Percutaneous Pulmonary Valve Implantation Are the Acute Effects of Altered Right Ventricular Loading All We Can Expect

OBJECTIVES The purpose of this study was to assess the potential of late positive functional remodeling after percutaneous pulmonary valve implantation (PPVI) in right ventricular outflow tract dysfunction. BACKGROUND PPVI has been shown to impact acutely on biventricular function and exercise performance, but the potential for further late functional remodeling remains unknown. METHODS Sixty-five patients with sustained hemodynamic effects of PPVI at 1 year were included. Patients were divided into 2 subgroups based on pre-procedural predominant pulmonary stenosis (PS) (n = 35) or predominant pulmonary regurgitation (PR) (n = 30). Data from magnetic resonance imaging and cardiopulmonary exercise testing were compared at 3 time points: before PPVI, within 1 month (early) and at 12 months (late) after PPVI. RESULTS There was a significant decrease in right ventricle end-diastolic volume early after PPVI in both subgroups of patients. Right ventricle ejection fraction improved early only in the PS group (51 ± 11% vs. 58 ± 11% and 51 ± 12% vs. 50 ± 11%, p < 0.001 for PS, p = 0.13 for PR). Late after intervention, there were no further changes in magnetic resonance parameters in either group (right ventricle ejection fraction, 58 ± 11% in the PS group and 52 ± 11% in the PR group, p = 1.00 and p = 0.13, respectively). In the PS group at cardiopulmonary exercise testing, there was a significant improvement in peak oxygen uptake early (24 ± 8 ml/kg/min vs. 27 ± 9 ml/kg/min, p = 0.008), with no further significant change late (27 ± 9 ml/kg/min, p = 1.00). In the PR group, no significant changes in peak oxygen uptake from early to late could be demonstrated (25 ± 8 ml/kg/min vs. 25 ± 8 ml/kg/min vs. 26 ± 9 ml/kg/min, p = 0.48). CONCLUSIONS In patients with a sustained hemodynamic result 1 year after PPVI, a prolonged phase of maintained cardiac function is observed. However, there is no evidence for further positive functional remodeling beyond the acute effects of PPVI.

Improvement in left ventricular filling properties after relief of right ventricle to pulmonary artery conduit obstruction: contribution of septal motion and interventricular mechanical delay.

AIMS To investigate the impact of relief of right ventricle (RV) to pulmonary artery (PA) conduit obstruction on septal motion and ventricular interaction and its functional implications for left ventricular (LV) filling properties. METHODS AND RESULTS In 20 consecutive patients with congenital heart disease and RV to PA conduit obstruction, the following were prospectively assessed before and after percutaneous pulmonary valve implantation (PPVI): the septal curvature and LV volumes throughout the cardiac cycle by magnetic resonance imaging; RV to LV mechanical delay by 2D-echocardiographic strain imaging; and objective exercise capacity. Percutaneous pulmonary valve implantation led to a reduction in RV to LV mechanical delay (127.9 +/- 50.9 vs. 37.7 +/- 35.6 ms; P < 0.001) and less LV septal bowing in early LV diastole (septal curvature: -0.11 +/- 0.11 vs. 0.07 +/- 0.13 cm(-1); P < 0.001). Early LV diastolic filling (first one-third of diastole) increased significantly (17.5 +/- 9.4 to 30.4 +/- 9.4 mL/m(2); P < 0.001). The increase in early LV diastolic filling correlated with the reduction in RV to LV mechanical delay (r = -0.68; P = 0.001) and change in septal curvature (r = 0.71; P < 0.001). In addition, the improvement in peak oxygen uptake (56.0 +/- 16.0 vs. 64.1 +/- 13.7% of predicted; P < 0.001) was associated with the increase in early LV diastolic filling (r = 0.69; P = 0.001). CONCLUSION Relief of RV to PA conduit obstruction significantly improves early LV filling properties. This is attributed to more favourable septal motion and reduction in interventricular mechanical delay.

Quantification of left ventricular trabeculae using fractal analysis

BackgroundLeft ventricular noncompaction (LVNC) is a myocardial disorder characterized by excessive left ventricular (LV) trabeculae. Current methods for quantification of LV trabeculae have limitations. The aim of this study is to describe a novel technique for quantifying LV trabeculation using cardiovascular magnetic resonance (CMR) and fractal geometry. Observing that trabeculae appear complex and irregular, we hypothesize that measuring the fractal dimension (FD) of the endocardial border provides a quantitative parameter that can be used to distinguish normal from abnormal trabecular patterns.MethodsFractal analysis is a method of quantifying complex geometric patterns in biological structures. The resulting FD is a unitless measure index of how completely the object fills space. FD increases with increased structural complexity. LV FD was measured using a box-counting method on CMR short-axis cine stacks. Three groups were studied: LVNC (defined by Jenni criteria), n=30(age 41±13; men, 16); healthy whites, n=75(age, 46±16; men, 36); healthy blacks, n=30(age, 40±11; men, 15).ResultsIn healthy volunteers FD varied in a characteristic pattern from base to apex along the LV. This pattern was altered in LVNC where apical FD were abnormally elevated. In healthy volunteers, blacks had higher FD than whites in the apical third of the LV (maximal apical FD: 1.253±0.005 vs. 1.235±0.004, p<0.01) (mean±s.e.m.). Comparing LVNC with healthy volunteers, maximal apical FD was higher in LVNC (1.392±0.010, p<0.00001). The fractal method was more accurate and reproducible (ICC, 0.97 and 0.96 for intra and inter-observer readings) than two other CMR criteria for LVNC (Petersen and Jacquier).ConclusionsFD is higher in LVNC patients compared to healthy volunteers and is higher in healthy blacks than in whites. Fractal analysis provides a quantitative measure of trabeculation and has high reproducibility and accuracy for LVNC diagnosis when compared to current CMR criteria.

Cardiac Magnetic Resonance Imaging After Stage I Norwood Operation for Hypoplastic Left Heart Syndrome

Background— After the Norwood operation, a patient’s suitability for proceeding to a bidirectional cavopulmonary connection (BCPC) is assessed by a combination of echocardiography and diagnostic cardiac catheterization. In this study, we describe the results of 37 patients who underwent cardiovascular magnetic resonance (MR) assessment before BCPC. Methods and Results— Cardiovascular MR and echocardiography were performed in 37 infants with hypoplastic left heart syndrome before BCPC, and the findings were compared with surgical findings. MR assessment of ventricular function and valvar regurgitation were compared with echocardiography. MR exhibited high sensitivity and specificity for identification of neoaortic (sensitivity 86%, specificity 97%) and left pulmonary artery (sensitivity 100%, specificity 94%) obstruction. Echocardiography exhibited poor sensitivity for identification of vascular stenosis. The mean right ventricular ejection fraction calculated from the MR data was 50±10%. There was general agreement between MR and echocardiographic measures of ventricular function, although patients with good function on echocardiography demonstrated a wide range of ejection fractions. There was good agreement between MR and echocardiography for identification of valvar regurgitation. Conclusions— Cardiovascular MR can be used to define ventricular and valvar function and vascular anatomy in infants with hypoplastic left heart syndrome after the Norwood operation. We have shown how this information can be used to plan the BCPC and identify any revisions or additional valvar surgery.

Prognostic Significance of Cardiac Magnetic Resonance Imaging in Children with Pulmonary Hypertension

Background— There are very few validated prognostic markers in pediatric pulmonary hypertension. Cardiac MRI is a useful, noninvasive method for determining prognosis in adults. The present study is the first to assess its prognostic value in children. Methods and Results— A total of 100 children with pulmonary hypertension (median, 10.4 years; range, 0.5–17.6 years) were evaluated (idiopathic, n=60; repaired congenital heart disease, n=22; miscellaneous, n=18). In all patients, ventricular volumes and great vessel flow were measured. Volumetric data were obtained using retrospectively gated cine imaging (n=37) or real-time imaging (n=63), depending on the patient’s ability to hold his or her breath. During a median follow-up of 1.9 years, 11 patients died and 3 received lung transplantation. Of the cardiac MR parameters measured, right ventricular ejection fraction and left ventricular stroke volume index were most strongly predictive of survival on univariate analysis (2.6- and 2.5-fold increase in mortality for every 1-SD decrease, respectively; P<0.05). These results were reflected in good separation of tertile-based Kaplan-Meier survival curves for these variables. Conclusions— Cardiac MR measures correlate with clinical status and prognosis in children with pulmonary hypertension. Cardiac MR is feasible and may be useful in clinical decision making in pediatric pulmonary hypertension.