Disturbed left and right ventricular kinetic energy in patients with repaired tetralogy of Fallot: pathophysiological insights using 4D-flow MRI

Objectives

Indications for pulmonary valve replacement (PVR) in patients with pulmonary regurgitation (PR) after repaired tetralogy of Fallot (rToF) are debated. We aimed to compare right (RV) and left ventricular (LV) kinetic energy (KE) measured by 4D-flow magnetic resonance imaging (MRI) in patients to controls, to further understand the pathophysiological effects of PR.

Methods

Fifteen patients with rToF with PR > 20% and 14 controls underwent MRI. Ventricular volumes and KE were quantified from cine MRI and 4D-flow, respectively. Lagrangian coherent structures were used to discriminate KE in the PR. Restrictive RV physiology was defined as end-diastolic forward flow.

Results

LV systolic peak KE was lower in rToF, 2.8 ± 1.1 mJ, compared to healthy volunteers, 4.8 ± 1.1 mJ, p < 0.0001. RV diastolic peak KE was higher in rToF (7.7 ± 4.3 mJ vs 3.1 ± 1.3 mJ, p = 0.0001) and the difference most pronounced in patients with non-restrictive RV physiology. KE was primarily located in the PR volume at the time of diastolic peak KE, 64 ± 17%.

Conclusion

This is the first study showing disturbed KE in patients with rToF and PR, in both the RV and LV. The role of KE as a potential early marker of ventricular dysfunction to guide intervention needs to be addressed in future studies.

Key Points

? Kinetic energy (KE) reflects ventricular performance ? KE is a potential marker of ventricular dysfunction in Fallot patients ? KE is disturbed in both ventricles in patients with tetralogy of Fallot ? KE contributes to the understanding of the pathophysiology of pulmonary regurgitation ? Lagrangian coherent structures enable differentiation of ventricular inflows

     

Quantitative assessment of right ventricular function and pulmonary regurgitation in surgically repaired tetralogy of Fallot using 256-slice CT: comparison with 3-Tesla MRI

Objectives

To compare 256-slice cardiac computed tomography (CCT) with cardiac magnetic resonance (CMR) imaging to assess right ventricular (RV) function and pulmonary regurgitant fraction (PRF) in patients with repaired tetralogy of Fallot (TOF).

Methods

Thirty-three consecutive patients with repaired TOF underwent retrospective ECG-gated CCT and 3-Tesla CMR. RV and left ventricular (LV) end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV) and ejection fraction (EF) were measured using CCT and CMR. PRF-CCT (%) was defined as (RVSV???LVSV)/RVSV. PRF-CMR (%) was measured by the phase-contrast method. Repeated measurements were performed to determine intra- and interobserver variability.

Results

CCT measurements, including PRF, correlated highly with the CMR reference (r?=?0.71–0.96). CCT overestimated RVEDV (mean difference, 17.1?±?2.9 ml), RVESV (12.9?±?2.1 ml) and RVSV (4.2?±?2.0 ml), and underestimated RVEF (?2.6?±?1.0 %) and PRF (?9.1?±?2.0 %) compared with CMR. The limits of agreement between CCT and CMR were in a good range for all measurements. The variability in CCT measurements was lower than those in CMR. The estimated effective radiation dose was 7.6?±?2.6 mSv.

Conclusions

256-slice CCT can assess RV function and PRF with relatively low dose radiation exposure in patients with repaired TOF, but overestimates RV volume and underestimates PRF.

Key points

? 256-slice CT assessment of RV function is highly reproducible in repaired TOF. ? Pulmonary regurgitation can be evaluated by biventricular systolic volume difference. ? CT overestimates RV volume and underestimates pulmonary regurgitation, compared with MRI.     

超声、MR对法洛四联症术后肺动脉瓣反流评估的比较

目的:比较超声心动图和心脏磁共振成像方法(CMR)评估TOF术后肺动脉瓣反流程度的价值。方法:随访9例TOF术后4~5年患儿,通过CMR测定肺动脉瓣反流分数(PRF),超声心动图测定肺动脉压力减半时间(PHT)、肺动脉瓣反流指数(PRi)以及反流束宽/肺动脉瓣环直径比值,用相关回归分析比较这些数值之间的相关性。结果:9例患儿PRF为28.8±5.5%(20.8-37.0%);PHT为60.2±14.1msec(44.6-90.5msec);PRi为0.7±0.13(0.54-0.93);反流束宽与肺动脉瓣直径比为53.3±10.5%(44.2-71.6%)。PRF与PHT负相关(r=-0.51,P=0.16),与PRi负相关(r=-0.69,P=0.04),与反流束宽/肺动脉瓣环直径比值正相关(r=0.71,P=0.03)。后两者P值有显著性意义。结论:TOF术后普遍存在肺动脉瓣反流。心脏磁共振成像和超声心动图可无创性评价肺动脉瓣反流程度,并且2种技术之间有较好的相关性。PRi是一个比较方便、准确的评估肺动脉瓣反流程度的指标。     

Left ventricular function and visual phase analysis with equilibrium radionuclide angiography in patients with biventricular device

Purpose Cardiac resynchronisation therapy (CRT) is a technique indicated in patients with moderate to severe heart failure and ventricular dyssynchrony. To evaluate left ventricular ejection fraction (LVEF) and synchronisation changes after CRT with a biventricular pacing implant, we used an equilibrium radionuclide angiography (ERNA). Methods Fifty patients were studied. An ERNA was made 72 h and 6 months after the implant. Two acquisitions were performed: with the CRT device connected and after disconnecting it. In the follow-up, responders were defined as those who had improved in accordance with various clinical variables. Quantitative changes in LVEF and visual changes in synchronisation (phase analysis) were studied comparing the two studies and also comparing the connected and disconnected modes. Results At 6 months, 30 patients were defined as responders. LVEF increased significantly at 6 months compared with the 72-h study only in responders. At 72 h, the number of patients showing a decrease in LVEF (p < 0.05) or a synchronisation worsening after disconnecting the device was higher in responders than in nonresponders. At 6 months, 57% of responders had no synchronisation changes between the connected and disconnected modes, suggesting a resynchronisation process. Conclusions ERNA permits the study of resynchronisation patients, showing a statistical LVEF improvement at 6 months. Moreover, visual phase analysis permits the study of the mechanism involved in the response, with an important number of responders with no changes between the two modes at 6 months. In the 72-h study, after disconnection of the device, LVEF and resynchronisation worsening can predict patient improvement at 6 months.     

Corrected tetralogy of Fallot: delayed enhancement in right ventricular outflow tract

PURPOSE: To evaluate retrospectively the presence of fibrosis and largest diameter of the right ventricular outflow tract (RVOT) by using delayed enhancement magnetic resonance (MR) imaging in patients who had undergone initial correction for tetralogy of Fallot. MATERIALS AND METHODS: MR imaging was performed in 24 consecutive patients (16 male, eight female; mean age, 25 years; age range, 13-47 years) with corrected tetralogy of Fallot. The study protocol was approved by the local ethics committee, and informed consent was not required. Fifteen minutes after injection of 0.2 mmol/kg gadopentetate dimeglumine, an inversion-recovery turbo field-echo sequence was applied for detection of delayed enhancement. Right ventricular volumes, ejection fraction, and anterior-posterior diameter of the RVOT were calculated. Mann-Whitney nonparametric testing was used to compare measurements of ventricular volume, function, and anterior-posterior diameter of the RVOT in the presence or absence of delayed enhancement. Correlation was tested with Pearson coefficient. RESULTS: Delayed enhancement was seen in 17 patients in the RVOT. During initial surgery, transannular patching was performed in 13 (76%) of 17 patients, RVOT patching in one (6%) of 17 patients, and the Brock procedure in two (12%) of 17 patients. In one patient, the type of initial RVOT repair was unknown. Patients with delayed enhancement in the RVOT, as compared with those without delayed enhancement in the RVOT, had increased RVOT diameter (32 mm +/- 7 [standard deviation] vs 22 mm +/- 3, P < .01), decreased right ventricular ejection fraction (43% +/- 6.3 vs 54% +/- 10, P < .001), and increased end-diastolic volume (175 mL/m2 +/- 42 vs 118 mL/m2 +/- 34, P < .01). The diameter of the RVOT correlated with increased right ventricular end-systolic volume (R = 0.86) and was inversely related to ejection fraction (R = -0.65). CONCLUSION: Delayed enhancement occurs frequently in patients after correction for tetralogy of Fallot. Delayed enhancement in the RVOT was associated with RVOT dilatation, which adversely affects right ventricular hemodynamics.     

Assessment of right ventricular afterload in mitral valve diseases with radionuclide angiography

Right ventricular function at rest and during exercise was studied in 33 patients with mitral valve disease by equilibrium gated radionuclide angiography using 99mTc in vivo labeled red blood cells. Radionuclide measurements of right ventricular ejection fraction (RVEF) were correlated with mean pulmonary arterial pressure (mPAP). RVEF decreased significantly with exercise. There was no significant correlation between RVEF at rest and mPAP. However, mPAP showed significant negative correlation with RVEF during exercise and with the changes of RVEF from rest to exercise. It is concluded that RVEF during exercise in mitral valve disease is affected by right ventricular afterload, and the measurements of RVEF at rest and during exercise by equilibrium gated radionuclide angiography is useful to assess right ventricular afterload.     

Diastolic function in repaired tetralogy of Fallot at rest and during stress: assessment with MR imaging

PURPOSE: To prospectively assess, with magnetic resonance (MR) imaging, right ventricular (RV) diastolic function after repair of tetralogy of Fallot (TOF) at rest and during pharmacologic stress and to study relationship between main pulmonary artery end-diastolic forward flow (EDFF) (indicative of restrictive RV physiology) and clinical status. MATERIALS AND METHODS: Institutional medical ethics committee approval and patient or parent informed consent were obtained. Patients with TOF corrected through the transatrial-transpulmonary approach underwent MR imaging at rest and during dobutamine stress and maximal exercise testing. Two-dimensional (2D) cine volumetric data were acquired. Flow measurements were performed with a standard 2D flow-sensitized sequence. MR imaging flow curves for tricuspid and pulmonary valves were combined into RV time-volume change curves, from which indexes of RV filling were derived. Patient results were compared with published data in control subjects. Student t tests, Mann-Whitney U tests, analysis of covariance, and paired and one-sample t tests were used. RESULTS: Thirty-six patients (mean age at repair, 0.9 year +/- 0.5 [standard deviation]; median age at study inclusion, 17 years [range, 7-23 years]; 26 male and 10 female patients) were included. Abnormalities in RV filling included impaired relaxation (prolonged deceleration time, P = .002; smaller early filling fraction, P = .02) in the entire group compared with published data in healthy control subjects and signs of restriction to RV filling (smaller atrial filling fraction and higher early filling/atrial filling peak ratio, P < .05 for both) in patients with EDFF (n = 24) compared with patients without EDFF (n = 12). Stress response was abnormal in patients with EDFF, who developed impaired RV relaxation not appreciated at rest. Patients with EDFF had more severe pulmonary regurgitation (P < .05) and poorer exercise performance (P < .001). CONCLUSION: In patients with TOF corrected with currently widely accepted surgical strategies, pulmonary artery EDFF relates to worse clinical state at mid- to long-term follow-up. Dobutamine stress imaging may unmask abnormalities in RV diastolic filling not appreciated with rest imaging alone.     

Stress-induced right ventricular ischemia in recurrent pulmonary outflow stenosis in repaired tetralogy of fallot

Radionuclide uptake by the right ventricle during myocardial perfusion imaging is minimal compared with the left ventricular myocardium and is not given much importance. However, right ventricular hypertrophy from pressure or volume overload may increase right ventricular radiotracer uptake and demonstrate reversible stress-induced perfusion abnormalities in the presence of normal coronary arteries. We report a case of right ventricular ischemia secondary to right ventricular hypertrophy from recurrent right ventricular outflow tract stenosis in a patient with repaired tetralogy of Fallot. Advances in the management of congenital heart disease have led to more patients surviving to adulthood. These patients subsequently present to cardiologists in adulthood with sequelae or complications arising from previous surgery undertaken during childhood.     

Quantitative assessment of cardiac mechanical synchrony using equilibrium radionuclide angiography

Background

Data on normal parameters of cardiac mechanical synchrony is limited, variable and obtained from small cohorts till date. In most studies, software used for such assessment has not been mentioned. The aim of study is to establish normal values of mechanical synchrony with equilibrium radionuclide angiography (ERNA) in a larger population using commercially available software.

Methods

We retrospectively analysed ERNA studies of 108 patients having low pretest likelihood of coronary artery disease, no known history of cardiac disease, normal electrocardiogram and whose ERNA studies were considered normal by experienced observers. In addition, ten patients diagnosed with dilated cardiomyopathy (DCM) and having LVEF ≤ 40% underwent ERNA. Fourier first harmonic analysis of phase images was used to quantify synchrony parameters using commercially available software (XT-ERNA). Intraventricular synchrony for each ventricle was measured as the standard deviation of the LV and RV mean phase angles (SD LVmPA and SD RVmPA, respectively). Interventricular synchrony was measured as LV-RVmPA. Absolute interventricular delay was calculated as absolute difference between LV and RVmPA (without considering ± sign). All variables were expressed in milliseconds (ms) and degree (°). Intra-observer and inter-observer variabilities were assessed. Cut-off values for parameters were calculated from the normal database, and validated against patient group.

Results

On phase analysis, LVmPA was observed to be 343 ± 48.5 milliseconds (174.7° ± 18.5°), SD LVmPA was 16.3 ± 5.4 milliseconds (8.2° ± 2.5°), RVmPA was 339 ± 50.4 milliseconds (171.8° ± 18.5°) and SD RVmPA was 37.3 ± 15.7 milliseconds (18.7° ± 7.2°). LV-RVmPA was observed to be 3.9 ± 21.7 milliseconds (2.9° ± 9.6°) and absolute interventricular delay was 16.3 ± 14.8 milliseconds (7.9° ± 6.1°). The cut-off values for the presence of dyssynchrony were estimated as SD LVmPA > 27.1 milliseconds (>13.2°), SD RVmPA > 68.7 milliseconds (>33.1°) and LV-RVmPA > 47.3 milliseconds (>22.1°). There was no statistically significant intra-observer or inter-observer variability. Using these cut offs, 9 patients with DCM showed the presence of left intraventricular dyssynchrony, 5 had right intraventricular dyssynchrony and 2 had interventricular dyssynchrony.

Conclusions

ERNA phase analysis offers an objective and reproducible tool to quantify cardiac mechanical synchrony using commercially available software and can be used in routine clinical practice to assess mechanical dyssynchrony.     

Right ventricular cineangiography in tetralogy of Fallot

Accurate delineation of the anatomy of the cardiac chambers and the pulmonary vessels is a neccessary component of the preoperative workup in Fallot's tetralogy. Selective right ventriculograms in shallow right anterior oblique and steep left anterior oblique views were used in the evaluation of 65 cases. Our observations indicate that these views display the anatomy of Fallot's tetralogy to a better advantage than do the conventional anteroposterior and lateral views.     

CMR在法洛四联症术后评估中的应用

心脏磁共振（CMR）是法洛四联症（TOF）术后评估的一站式影像诊断工具。随着四维血流CMR技术、CMR-特征追踪技术和纵向弛豫时间定量成像等新技术的发展和应用,CMR可以同时实现心肌运动、血流动力学及心肌组织定量评估,特别对于评价术后TOF（rTOF）早期的血流动力学改变,早期预判rTOF的功能异常,以及反映心肌纤维化与rTOF心律失常的关系是非常有价值的。就上述CMR新技术及其在TOF术后的应用进行综述。     

Range of ventricular dimensions and function by steady-state free precession cine MRI in repaired tetralogy of Fallot: right ventricular outflow tract patch vs. conduit repair

PURPOSE: To characterize the range of biventricular size and function evaluated by steady-state free precession (SSFP) cine magnetic resonance (MR) in a large cohort of patients with repaired tetralogy of Fallot (TOF), and to compare these measurements in those with a right ventricular outflow tract (RVOT) patch vs. a right ventricle-to-pulmonary artery (RV-PA) conduit. MATERIALS AND METHODS: Analysis of ventricular size and function in 300 consecutive examinations in patients with repaired TOF evaluated by SSFP cine MR. RESULTS: Of the 300 examinations performed in 256 patients, 69% had undergone repair with a RVOT patch and 31% with a RV-PA conduit. Compared to patients with RV-PA conduit, those with a RVOT patch had significantly more pulmonary regurgitation (PR) (38 +/- 17 vs. 23 +/- 16%, P < 0.0001), larger indexed RV end-diastolic volume (154 +/- 53 vs. 133 +/- 51 mL/m(2), P = 0.002), similar indexed end-systolic volume (80 +/- 39 vs. 74 +/- 46 mL/m(2), P = 0.31), higher ejection fraction (EF) (50 +/- 9 vs. 47 +/- 12%, P = 0.037), and lower mass-to-volume ratio (0.29 +/- 0.08 vs. 0.36 +/- 0.13, P < 0.0001). Pulmonary regurgitation fraction correlated positively with RV end-diastolic volume index in the RVOT patch group (r = 0.51, P < 0.0001) but not in the RV-PA conduit. CONCLUSION: This study provides the range and distribution of biventricular size and function, and PR measured by MRI in a large contemporary cohort of patients with repaired TOF, and demonstrates important variations in RV mechanics between patients repaired with a RVOT patch and those with an RV-PA conduit.     

First-pass radionuclide assessment of right and left ventricular performance in patients with cardiac and pulmonary disease

First-pass radionuclide angiocardiography allows noninvasive determination of right and left ventricular performance from a single study. Analysis is made from the high frequency components of the regional radionuclide time-activity curves. Both regional and global ventricular performance can be assessed at rest and during exercise. Sequential studies can be performed to evaluate therapeutic interventions. This technique has been applied in a broad spectrum of patients with cardiac and pulmonary disease and has been shown to have major clinical impact.     

Cardiac gated equilibrium radionuclide angiography and multiharmonic Fourier phase analysis: Optimal acquisition parameters in arrhythmogenic right ventricular cardiomyopathy

BACKGROUND: Multiharmonic Fourier phase analysis of radionuclide angiography is a well-established method for the diagnosis of arrhythmogenic right ventricular cardiomyopathy. We sought to determine the optimal acquisition parameters: number of frames per cycle and number of counts per frame, with all other acquisition and processing parameters being fixed. METHODS AND RESULTS: Radionuclide angiography with list mode acquisition was performed in 10 normal subjects (pilot group) and 11 patients with arrhythmogenic right ventricular cardiomyopathy (validation group), allowing the reconstruction of electrocardiography-gated constant phase studies with different parameters: 16, 24, and 32 frames per cycle and 200, 400, 600, and 800 kcounts per frame. Three harmonics Fourier phase analysis was applied, and optimal acquisition parameters (defined as those providing best homogeneous phase distribution histogram in the pilot group) were defined as judged by the H3 right ventricular phase SD and delta 95%. These were 16 frames per cycle and 600 kcounts per frame. Then we verified in the validation group that these optimal acquisition parameters did not induce any significant relative loss of information compared with other acquisition parameters with more temporal resolution (24 and 32 frames per cycle) or more statistics (800 kcounts per frame). This result was realized by the calculation of normalized H3 right ventricular SD, right ventricular delta 95%, and (SD[left ventricle] - SD[right ventricle]). CONCLUSIONS: In practice, 16 frames per cycle and 600 kcounts per frame are optimal for multiharmonic Fourier phase analysis, with all other acquisition and processing variables being fixed as specified.     

Evaluation of ventricular diastolic function in normal children using equilibrium radionuclide angiography.

Twenty children, aged 10.3 +/- 4.5 (3.3 to 17.5) years, were studied by equilibrium radionuclide angiography to establish a normal range for diastolic parameters. Ejection fraction (EF), peak ejection rate (PER) and time to peak ejection rate (TPER), peak filling rate (PFR) and time to peak filling rate (TPFR) were obtained from ventricular time-activity curves and their first derivative curves, and PFR and TPFR were considered as the diastolic parameters. Normal ranges obtained were as follows: EF, 60 +/- 8%; PER, 3.73 +/- 0.70 EDV-1; TPER, 109 +/- 25 ms; PFR, 3.84 +/- 0.51 EDVs-1; TPFR, 136 +/- 21 ms. There were significant correlations between PER and EF (P less than 0.001), PFR and EF (P less than 0.05), while age and heart rate had no influence upon these variables. Such normal ranges will be useful for evaluation of systolic and diastolic function in children with heart disease.     

Thinning of ventricular septum in tetralogy of Fallot]

Cross sectional echocardiography was used to evaluate the thickness of the ventricular septum in tetralogy of Fallot (TOF). Forty-six patients with TOF and 20 patients with pseudo-truncus arteriosus underwent echocardiography during a five-year period beginning in 1984. Thicknesses of the right ventricular anterior wall (RVAWT), trabecular septum (IVST) and left ventricular posterior wall (LVPWT) were measured in end diastole on parasternal short axis view at the level of the tips of papillary muscles. The ratios of IVST to RVAWT and IVST to LVPWT were assessed. The ratio of IVST to RVAWT was 1.09 +/- 0.15 in the group aged less than 7 years (less than 7 y.o.) and 0.94 +/- 0.15 in the group aged of 7 years or more (greater than = 7 y.o.). The ratios of IVST to LVPWT were 1.10 +/- 0.14 (less than 7 y.o.) and 0.90 +/- 0.15 (greater than = 7 y.o.), respectively. Both ratios were significantly different (p less than 0.01) in the two age groups, and relative thinning of the septum was demonstrated in the older patients. It is speculated that thinning of the interventricular septum is caused by the lower systolic wall stress of the ventricular septum compared with that of the free walls, which is produced under equal systolic pressure of the two ventricles. It is suggested that this thinning is one of the factors that reduces left ventricular function after repair of TOF.     

Delayed contraction area responsible for sustained ventricular tachycardia in an arrhythmogenic right ventricular cardiomyopathy: Demonstration by fourier analysis of SPECT equilibrium radionuclide angiography

Conclusion  Phase imaging assessed with a 3-dimensional analysis is particularly interesting for its capacity to detect an area with early contraction corresponding to the site of VT with accuracy and to demonstrate 1 or several areas with delayed contraction because of the loss of contractile tissue by fatty or fibrofatty replacement, as has been suggested with magnetic resonance images. We believe that this 3-dimensional Fourier analysis of SPECT ERNA should be widely used in sinus rhythm and when possible, during episodes of VT before treatment by ablation techniques or surgery.