Routine breath-hold gradient echo MRI-derived right ventricular mass, volumes and function: accuracy, reproducibility and coherence study

Assessment of right ventricle volumes and function by cardiac MRI: quantification of the regional and global interobserver variability

Reproducibility of the manual assessment of right ventricle volumes by short-axis cine-MRI remains low and is often attributed to the difficulty in separating the right atrium from the ventricle. This study was designed to evaluate the regional interobserver variability of the right ventricle volume assessment to identify segmentation zones with the highest interobserver variability. Short-axis views of 90 right ventricles (30 hypertrophic, 30 dilated, and 30 normal) were acquired with 2D steady-state free precession sequences at 1.5 T and were manually segmented by two observers. The two segmentations were compared and the variations were quantified with a variation score based on the Hausdorff distance between the two segmentations and the interobserver 95% limits of concordance of the global volumes. The right ventricles were semiautomatically split into four subregions: apex, mid-ventricle, tricuspid zone, and infundibulum. These four subregions represented 11%, 34%, 36%, and 19% of the volume but, respectively, yielded variation scores of 8%, 16%, 42%, and 34%. The infundibulum yielded the highest interobserver regional variability although its variation score remained comparable to the tricuspid zone due to its lower volume. These results emphasize the importance of standardizing the segmentation of the infundibulum and the tricuspid zone to improve reproducibility.

Modified INOvent for delivery of inhaled nitric oxide during cardiac MRI

BACKGROUND

The aim of this study was to assess the feasibility of delivering NO through a modified system to allow clearance of the magnetic field and thus compatibility with cardiac magnetic resonance (CMR). Nitric oxide (NO) is an inhalational, selective pulmonary vasodilator with a wide range of applications in a variety of disease states, including diseases that affect the right ventricle. Accurate assessment of dynamic changes in right ventricular function necessitates CMR; however, delivery of NO is only possible using equipment that is not magnetic resonance imaging (MRI) compatible (INOvent delivery system, Ohmeda, Inc., Madison, WI, USA).

METHODS

The INOvent delivery system was modified by using 35 ft. of standard oxygen tubing to allow NO delivery through an electrical conduit and into the MRI suite. The concentrations of oxygen (O(2)), nitrogen dioxide (a harmful byproduct, NO(2)) and NO were measured in triplicate using the built-in electrochemical analyzer on the INOvent. After confirmation of safety, the system was used to administer drug to a patient x, and dynamic MRI measurements were performed.

RESULTS

When the standard INOvent was set to administer 40 ppm of NO, the mean/standard deviation of gas delivered was as follows: NO: 42/0 ppm; NO(2): 0.3/0.1 ppm; and O(2): 93/0 ppm. In comparison, the gas delivery of the modified INOvent was follows: NO: 41/0 ppm; NO(2): 0.5/0 ppm; and O(2): 93.7/0.6 ppm. During administration to an index patient with severe pulmonic insufficiency (PI), a measurable reduction in PI was observed by CMR.

CONCLUSIONS

Nitric oxide can be administered through 35 ft. of standard oxygen tubing without significantly affecting dose delivery. This technique has potential application in patients with right-sided structural heart disease for determination of dynamic physiological changes.

Diagnostic accuracy and variability of three semi-quantitative methods for assessing right ventricular systolic function from cardiac MRI in patients with acquired heart disease

OBJECTIVES

To evaluate the diagnostic accuracy and variability of 3 semi-quantitative (SQt) methods for assessing right ventricular (RV) systolic function from cardiac MRI in patients with acquired heart disease: tricuspid annular plane systolic excursion (TAPSE), RV fractional-shortening (RVFS) and RV fractional area change (RVFAC).

METHODS

Sixty consecutive patients were enrolled. Reference RV ejection fraction (RVEF) was determined from short axis cine sequences. TAPSE, RVFS and RVFAC were measured on a 4-chamber cine sequence. All SQt analyses were performed twice by 3 observers with various degrees of training in cardiac MRI. Correlation with RVEF, intra- and inter-observer variability, and receiver operating characteristic (ROC) curve analysis were performed for each SQt method.

RESULTS

Correlation between RVFAC and RVEF was good for all observers and did not depend on previous cardiac MRI experience (R range = 0.716-0.741). Conversely, RVFS (R range = 0.534-0.720) and TAPSE (R range = 0.482-0.646) correlated less with RVEF and depended on previous experience. Intra- and inter-observer variability was much lower for RVFAC than for RVFS and TAPSE. ROC analysis demonstrated that RVFAC <41% could predict a RVEF <45% with 90% sensitivity and 94% specificity.

CONCLUSIONS

RVFAC appears to be more accurate and reproducible than RVFS and TAPSE for SQt assessment of RV function by cardiac MRI.

Repaired tetralogy of Fallot: the roles of cardiovascular magnetic resonance in evaluating pathophysiology and for pulmonary valve replacement decision support

Surgical management of tetralogy of Fallot (TOF) results in anatomic and functional abnormalities in the majority of patients. Although right ventricular volume load due to severe pulmonary regurgitation can be tolerated for many years, there is now evidence that the compensatory mechanisms of the right ventricular myocardium ultimately fail and that if the volume load is not eliminated or reduced by pulmonary valve replacement the dysfunction might be irreversible. Cardiovascular magnetic resonance (CMR) has evolved during the last 2 decades as the reference standard imaging modality to assess the anatomic and functional sequelae in patients with repaired TOF. This article reviews the pathophysiology of chronic right ventricular volume load after TOF repair and the risks and benefits of pulmonary valve replacement. The CMR techniques used to comprehensively evaluate the patient with repaired TOF are reviewed and the role of CMR in supporting clinical decisions regarding pulmonary valve replacement is discussed.

Accuracy of knowledge-based reconstruction for measurement of right ventricular volume and function in patients with tetralogy of Fallot

We tested the accuracy and reproducibility of knowledge-based reconstruction (KBR) for measuring right ventricular (RV) volume and function. KBR enables rapid assessment of the right ventricle from sparse user input by referencing a database. KBR generates a 3-dimensional surface to fit points that the user enters at anatomic landmarks. We measured the RV volume using KBR from magnetic resonance images in 20 patients with repaired tetralogy of Fallot at end-diastole and end-systole. We entered points in the long- and short-axis and/or oblique views. The true volume was computed by manually tracing the RV borders for 3-dimensional reconstruction using the piecewise smooth subdivision surface method. The reference database included 54 patients with tetralogy of Fallot patients. The KBR values agreed closely with the true values for the end-diastolic volume (r = 0.993), end-systolic volume (r = 0.992), and ejection fraction (EF; r = 0.930). KBR slightly overestimated the end-diastolic volume (4 +/- 10 ml, p = NS), end-systolic volume (1 +/- 9 ml, p = NS), and EF (4 +/- 3%, p = NS). No bias in the error was found by Bland-Altman analysis (p = NS for end-diastolic and end-systolic volume and EF). The KBR volumes had approached the true volumes (235 +/- 93 vs 243 +/- 93, p = 0.012, r = 0.978 for end-diastolic and end-systolic volumes combined) already after the first run and the entry of 19 +/- 3 points. In conclusion, KBR provided accurate measurement of the RV volume and EF with minimal user input. KBR is a clinically feasible alternative to full manual tracing of the heart borders from imaging data.

The role of 1.5T cardiac MRI in the diagnosis, prognosis and management of pulmonary arterial hypertension

Cardiovascular magnetic imaging is a noninvasive, three dimensional tomographic technique that allows for a detailed morphology of the cardiac chambers, the accurate quantification of right ventricle volumes, myocardial mass, and transvalvular flow. It can also determine whether right ventricular diastolic function is impaired through pulmonary hypertension. The aim of this article is to review the main kinetic, morphological and functional changes of the right ventricle that can occur in patients affected by pulmonary arterial hypertension (PAH) and to assess how the MRI findings can influence the prognosis, and guide the decision-making strategy. In those cases in which MRI shows a significant cardiac diastolic dysfunction, the prognosis is predictive of pharmacological treatment failure, and mortality. This leaves double lung-heart transplantation as the only therapeutic option. The coexistence of PAH and left ventricle impairment causes worse right ventricle function, leads to a poor prognosis, and may change the therapeutic strategies (for example, PAH associated with left ventricle dysfunction may require a double lung-heart transplant).

Measuring the heart in pulmonary arterial hypertension (PAH): implications for trial study size

PURPOSE

To calculate the sample size for a theoretical pulmonary arterial hypertension (PAH) randomized controlled trial (RCT) by using cardiovascular magnetic resonance (CMR) imaging to determine the repeatability of measures between two scans.

MATERIALS AND METHODS

Two same-day examinations from 10 PAH patients were analyzed manually and semiautomatically. Study size was calculated from the standard deviation (SD) of repeatability. Different approaches to right-ventricle (RV) mass were investigated, agreement between methods tested and interobserver reproducibility measured by Bland-Altman analysis to explore how the PAH heart might be best measured.

RESULTS

Repeatability was good for almost all manually-measured indices but poor for semiautomated measurement of RV mass and left-ventricle (LV) end-diastolic volume (EDV). Thus, for an RCT (power, 80%; significance level, 5%) analyzing "outcome" indices (RVEDV, LVEDV, RV ejection fraction, and RV mass; anticipated change: 10 mL, 10 mL, 3%, and 10 g, respectively) manually, 34 patients are required compared to 78 if analysis is semiautomated. RV mass was repeatable if the interventricular septum was divided between ventricles or if wholly apportioned to the LV. Limits of agreement between manual and semiautomated analyses were unsatisfactory for RV measures and interobserver reproducibility was worse for semiautomated than manual analysis.

CONCLUSION

Manual is more robust than semiautomated analysis and at present should be favored in RCTs in PAH as it leads to lower sample size requirements.

Combined assessment of myocardial perfusion and late gadolinium enhancement in patients after percutaneous coronary intervention or bypass grafts: a multicenter study of an integrated cardiovascular magnetic resonance protocol

OBJECTIVES

We sought to assess the accuracy of an integrated cardiac magnetic resonance (CMR) protocol for the diagnosis of relevant coronary artery or bypass graft stenosis in patients with suspected coronary artery disease (CAD) or with previously performed percutaneous coronary intervention (PCI) or coronary bypass graft surgery (CABG).

BACKGROUND

CMR is suitable for diagnosing inducible myocardial ischemia in patients with suspected CAD and has been proven to be a helpful diagnostic tool for decision of further treatment. However, little is known about its diagnostic accuracy in patients with known CAD who previously were treated by PCI or CABG.

METHODS

A total of 477 patients with suspected CAD, 236 with previous PCI, and 110 after CABG referred for coronary X-ray angiography (CXA) underwent an integrated CMR examination before CXA. Myocardial ischemia was assessed using first-pass perfusion after vasodilator stress with adenosine (140 microg/kg/min for 3 min) using gadolinium-based contrast agents (0.1 mmol/kg). Late gadolinium enhancement (LGE) was assessed 10 min after a second contrast bolus.

RESULTS

CXA demonstrated a relevant coronary vessel stenosis (> or =70% luminal reduction) in 313 (38%) patients using quantitative coronary analysis. The combination of CMR perfusion and LGE assessment for detecting a relevant coronary stenosis in patients with suspected CAD yielded sensitivity and specificity of 0.94 and 0.87, in PCI patients 0.91 and 0.90, and in CABG patients 0.79 and 0.77, respectively.

CONCLUSIONS

A combined CMR protocol for the assessment of myocardial perfusion and LGE is feasible for the detection of relevant coronary vessel stenosis even in patients who previously were treated by PCI or CAG in a routine clinical setting. However, diagnostic accuracy is reduced in patients with CABG. This could be due to different flow and perfusion kinetic. Further studies are needed to optimize the clinical protocols especially in post-surgical patients.

[Current indications for cardiac MR imaging]

MRI has acquired over the years a role in the evaluation of cardiovascular pathology especially with regards to its ability to assess right and left ventricular function and delayed postcontrast "viability" sequences. Current class I clinical indications include: viability for patients with ischemic cardiomyopathy and acute coronary syndrome, etiology and prognostic evaluation of non-ischemic cardiomyopathies including myocarditis and arrhytmogenic right ventricular cardiomyopathy, chronic pericarditis and cardiac masses, non-urgent aortic aneurysm and dissection, congenital cardiopathies: vascular malformations and follow-up after curative or palliative surgery. MRI provides a complete non operator dependent evaluation, and is particularly useful for follow-up since it may be repeated due to its absence of ionizing radiation

Interactive real-time mapping and catheter ablation of the cavotricuspid isthmus guided by magnetic resonance imaging in a porcine model

Aims

We investigated the feasibility of real-time magnetic resonance imaging (RTMRI) guided ablation of the cavotricuspid isthmus (CTI) by using a MRI-compatible ablation catheter.

Methods and results

Cavotricuspid isthmus ablation was performed in an interventional RTMRI suite by using a novel 7 French, steerable, non-ferromagnetic ablation catheter in a porcine in vivo model (n = 20). The catheter was introduced and navigated by RTMRI visualization only. Catheter position and movement during manipulation were continuously visualized during the entire intervention. Two porcine prematurely died due to VT/VF. Anatomical completion of the CTI ablation line could be achieved after a mean of 6.3±3 RF pulses (RF energy: 1807±1016.4 Ws/RF pulse, temperature: 55.9±5.9°C) in n = 18 animals. In 15 of 18 procedures (83.3%) a complete CTI block was proven by conventional mapping in the electrophysiological (EP) lab.

Conclusion

Completely non-fluoroscopic ablation guided by RTMRI using a steerable and non-ferromagnetic catheter is a promising novel technology in interventional electrophysiology.

Obstructive sleep apnea and pulmonary hypertension

Obstructive sleep apnea (OSA) is associated with repetitive nocturnal arterial oxygen desaturation and hypercapnia, large intrathoracic negative pressure swings, and acute increases in pulmonary artery pressure. Rodents when exposed to brief, intermittent hypoxia for several hours per day to mimic OSA developed pulmonary vascular remodeling and sustained pulmonary hypertension and right ventricular hypertrophy within a few weeks. Until recently, however, it was unclear whether episodic nocturnal hypoxemia associated with OSA was sufficient to cause similar changes in humans. This controversy appears to have been resolved by several recent studies that have shown (a) pulmonary hypertension in 20% to 40% of patients with OSA in the absence of other known cardiopulmonary disorders and (b) reductions in pulmonary artery pressure in patients with OSA after nocturnal continuous positive airway pressure (CPAP) treatment. The pulmonary hypertension associated with OSA appears to be mild and may be due to a combination of precapillary and postcapillary factors including pulmonary arteriolar remodeling and hyperreactivity to hypoxia and left ventricular diastolic dysfunction and left atrial enlargement. Although measurable changes in the structure and function of the right ventricle have been reported in association with OSA, the clinical significance of these changes is uncertain. Right ventricular failure in OSA appears to be uncommon and is more likely if there is coexisting left-sided heart disease or chronic hypoxic respiratory disease.

[Quantification of right ventricular function by 2D speckle imaging and three dimensional echography. Comparison with MRI]

PURPOSE

The echocardiographic assessment of right ventricular (RV) function requires many different parameters. We studied and compared with magnetic resonance imaging (MRI) two markers of RV function derived from new imaging tools: 2D speckle imaging (2DSI) and three dimensional echography.

METHODS AND RESULTS

Thirty-two patients (19 with RV ejection fraction [RVEF]< or =45%) underwent both complete echocardiography--including standard parameters of RV function (fractional area change [FAC], Tei index, systolic velocity of tricuspid annulus by DTI), 3D full-volume acquisition on RV--and MRI for the evaluation of RV volumes and RVEF. 2DSI was applied to high frame rate cine loops centred on the RV free wall with measurement of peak systolic strain (%) in the basal, median and apical segments of this wall. Strain, especially in RV median and apical segments, is reduced in patients with RVEF less or equal to 45% (median strain: -16.39+/-5.27 vs. -24.74+/-8.00 [p=0.002]; apical strain -13.01+/-6.84 vs. 22.53+/-11.32 [p=0.03]) with a very good correlation with RVEF (r=-0.717, p=0.0001) but also with the usual echographic parameters of RV function, (FAC: r=0.019; Tei: r=0.01; peak systolic velocity: r=0.002). The 3D RVEF is also but poorly correlated with MRI RVEF, (r=0.447, p=0.017). Furthermore, 3D significantly underestimated RV volumes. By multivariate analysis, apical strain (p=0.004) and FAC (p=0.029) were predictive of a decreased RVEF.

CONCLUSION

Apical strain as measured from 2DSI seems a promising parameter in the estimation of RV function. 3D estimation of RVEF is more disappointing because of an important underestimation of RV volumes.

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

PURPOSE

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.

MATERIALS AND METHODS

CMR studies of 60 patients in three groups were studied: a normal RV group (N = 20) and two groups with RV dilation-atrial septal defect (ASD) (N = 20) and repaired tetralogy of Fallot (TOF) (N = 20). Two independent observers analyzed each study on two separate occasions. Inter- and intraobserver reproducibility of biventricular mass, volume, ejection fraction (EF), and stroke volume (SV) measurements were calculated.

RESULTS

High intraclass correlation coefficients (ICC) were found for interobserver (ICC = 0.94-0.99) and intraobserver (ICC = 0.96-0.99) comparisons of RV and left ventricular (LV) mass, volume, and SV measurements. RV and LV EF measurements were less reproducible (ICC = 0.79-0.87). RV mass measurements were significantly less correlated than the respective LV measurements. Small but statistically significant differences in correlation were noted in RV measurements across groups.

CONCLUSION

Except for RV mass, inter- and intraobserver reproducibility of RV size and function measurements is high and generally comparable to that in the LV in patients with both normal and dilated RV.

Segmentation of cardiac cine MR images of left and right ventricles: interactive semiautomated methods and manual contouring by two readers with different education and experience

PURPOSE

To test interactive semiautomated methods (ISAM) vs. manual contouring (MC) in segmenting cardiac cine MR images.

MATERIALS AND METHODS

Short-axis images of 10 consecutive patients (1.5-81.5 years of age) were evaluated by a trained radiologist (R1) and a low-trained engineer (R2). Each of them performed four independent reading sessions: two using ISAM and two using MC. Left ventricle (LV) myocardial mass (LVMM), LV ejection fraction (LVEF), and right ventricle (RV) ejection fraction (RVEF) were obtained. Bland-Altman analysis and Wilcoxon test were used.

RESULTS

The bias +/- 2 standard deviations (SD) of ISAM vs. MC for LVMM (g) was -5.7 +/- 13.4 (R1) and -5.5 +/- 26.3 (R2); for LVEF (%) it was -1.4 +/- 13.0 and -2.9 +/- and 6.8; for RVEF (%) it was 2.6 +/- 17.0 and 1.0 +/- 16.7. Considering both readers/methods, intraobserver bias +/- 2 SD ranged from 0.3 +/- 25.3 to -6.8 +/- 23.0, from 0.2 +/- 8.0 to -4.4 +/- 15.8, and from -0.0 +/- 26.4 to -4.6 +/- 27.8, respectively. Interobserver bias +/- 2 SD was -25.9 +/- 46.0 (ISAM) and 26.1 +/- 36.4 (MC), -1.4 +/- 8.6 (ISAM) and 0.1 +/- 17.9 (MC), and 0.7 +/- 23.3 and 2.3 +/- 29.8, respectively. Larger SDs were systematically found for RVEF vs. LVEF. Segmentation times: five minutes for LV with ISAM (both readers); for LV with MC, six (R1) vs. nine minutes (R2) (P < 0.001); five to six minutes for RV (both methods /readers). R2 significantly reduced LV segmentation times from nine (MC) to five minutes (ISAM) (P < 0.001).

CONCLUSION

A highly reproducible LV segmentation was performed in a short time by R1. The advantage of ISAM vs. MC for LV segmentation was a time saving only for R2. For RVEF, a lower reproducibility was observed for both methods and readers.

Evaluating the systemic right ventricle by CMR: the importance of consistent and reproducible delineation of the cavity

BACKGROUND

The method used to delineate the boundary of the right ventricle (RV), relative to the trabeculations and papillary muscles in cardiovascular magnetic resonance (CMR) ventricular volume analysis, may matter more when these structures are hypertrophied than in individuals with normal cardiovascular anatomy. This study aimed to compare two methods of cavity delineation in patients with systemic RV.

METHODS

Twenty-nine patients (mean age 34.7 +/- 12.4 years) with a systemic RV (12 with congenitally corrected transposition of the great arteries (ccTGA) and 17 with atrially switched (TGA) underwent CMR. We compared measurements of systemic RV volumes and function using two analysis protocols. The RV trabeculations and papillary muscles were either included in the calculated blood volume, the boundary drawn immediately within the apparently compacted myocardial layer, or they were manually outlined and excluded. RV stroke volume (SV) calculated using each method was compared with corresponding left ventricular (LV) SV. Additionally, we compared the differences in analysis time, and in intra- and inter-observer variability between the two methods. Paired samples t-test was used to test for differences in volumes, function and analysis time between the two methods. Differences in intra- and inter-observer reproducibility were tested using an extension of the Bland-Altman method.

RESULTS

The inclusion of trabeculations and papillary muscles in the ventricular volume resulted in higher values for systemic RV end diastolic volume (mean difference 28.7 +/- 10.6 ml, p < 0.001) and for end systolic volume (mean difference 31.0 +/- 11.5 ml, p < 0.001). Values for ejection fraction were significantly lower (mean difference -7.4 +/- 3.9%, p < 0.001) if structures were included. LV SV did not differ significantly from RV SV for both analysis methods (p = NS). Including structures resulted in shorter analysis time (p < 0.001), and showed better inter-observer reproducibility for ejection fraction (p < 0.01).

CONCLUSION

The choice of method for systemic RV cavity delineation significantly affected volume measurements, given the CMR acquisition and analysis systems used. We recommend delineation outside the trabeculations for routine clinical measurements of systemic RV volumes as this approach took less time and gave more reproducible measurements.

Accuracy of guideline recommendations for two-dimensional quantification of the right ventricle by echocardiography

BACKGROUND

The accuracy of the guidelines of the American Society of Echocardiography (ASE) for the two-dimensional (2D) quantitative assessment of right ventricular (RV) size and function has not been evaluated against MRI-derived RV volumes in patients with congenital heart disease and RV volume overload.

METHODS

Three groups of patients were studied: a normal RV group (Group I, n = 31), a repaired tetralogy of Fallot group (Group II, n = 33), and an unrepaired atrial septal defect and/or partially anomalous pulmonary venous connection group (Group III, n = 23). Recommended 2D linear and cross-sectional area measurements were made on clinical echocardiographic and MRI studies performed less than 6 months apart.

RESULTS

Most 2D RV parameters were smaller by echocardiography versus MRI. There was weak correlation between 2D RV measurements by echocardiography and MRI-derived RV volumes (Group I: r = 0.15-0.54, Group II: r = 0.33-0.61, Group III: r = 0.32-0.85), and only modest improvement when the same 2D measurements were performed by MRI (Group I: r = 0.37-0.61, Group II: r = 0.44-0.69, Group III: r = 0.28-0.74). The difference between 2D RV measurements by echocardiography and MRI-derived RV volumes was more pronounced in the RV volume overload groups.

CONCLUSIONS

The correlation between currently recommended 2D RV measurements by echocardiography and MRI-derived RV volumes was weak, and improved only modestly when MRI was used to make the same 2D measurements. Moreover, 2D echocardiographic assessment of the RV appears to be less accurate in patients with congenital heart disease and a dilated RV.

Intra-observer and interobserver reproducibility of right ventricle volumes, function and mass by cardiac magnetic resonance

OBJECTIVES

Cardiac magnetic resonance (CMR) allows quick and non-invasive evaluation both of right ventricle (RV) volume and function, which are important in many heart diseases. We have evaluated CMR intra- and interobserver reproducibility in different conditions of RV dimension and function.

METHODS

We have analysed CMR exams of 45 subjects, randomly selected from our database according to RV end-diastolic volume (EDV; 15-subject groups with EDV < 25th, 25-75th and > 75th percentiles of a normal control population). Selected subjects were of both sexes (male/female 33/12) and of variable age (8-83 years) and body surface (0.9-2.3 m). RV end-diastolic and end-systolic volumes (ESV), ejection fraction (EF) and mass were blindly evaluated by two operators. Bland-Altman bias and coefficient of variability (CoV) were used to assess intra- and interobserver reproducibility.

RESULTS

A wide range of EDV (range = 46-239 ml), ESV (20-129 ml) and EF (6-64%) was observed. The intra-observer bias was -5 ml for EDV, -2 ml for ESV, -1% for EF and 5 g for mass, with a CoV of 7-12%. The interobserver bias was 5 ml for EDV, 2 ml for ESV, 2% for EF and 6 g for mass, with a CoV of 8-13%. Analysis by tertiles showed EF assessment variability to be higher in the lower tertiles at intra-observer (P < 0.036) and, above all, at interobserver (P < 0.000) analysis. Mass assessment variability was higher in the upper tertile (P < 0.004) at intra-observer analysis.

CONCLUSIONS

Intra- and interobserver reproducibility of RV parameters assessed by CMR are adequate in a wide range of RV dimensions and function. However, caution is required with respect to the significance of small changes of EF and mass in the case of poor function and hypertrophy of the RV, respectively.

Role and effectiveness of cardiovascular magnetic resonance in the diagnosis, preoperative evaluation and follow-up of patients with congenital heart diseases

The substantial advances in the medical and surgical treatment of congenital heart diseases have dramatically improved patients' life expectancy, as well as increased the number of those needing lifelong monitoring to identify complications and residual defects. Magnetic resonance imaging (MRI) is an ideal imaging modality for the follow-up of these young patients owing to its noninvasiveness, high reproducibility and morphological and functional accuracy. This paper describes the most appropriate MRI techniques and sequences for the study of cardiovascular heart diseases on the basis of an analysis of MRI studies carried out between January 2003 and June 2006 on 274 patients affected by all of the main congenital cardiovascular malformations, as well as a review of the literature. The advantages of MRI with respect to other imaging techniques, the problems encountered and the main clinical applications and indications of MRI, with special reference to the most common disease entities, are then discussed to define the role, the utility and the future perspectives of this imaging technique in the study of congenital heart diseases.

Adenosine stress first pass perfusion for the detection of coronary artery disease in patients with aortic stenosis: a feasibility study

PURPOSE

Detection of coronary artery disease (CAD) with magnetic resonance imaging (MRI) using adenosine stress first pass perfusion in patients with aortic stenosis in comparison with invasive angiography. Twenty-three consecutive patients (15 male, mean age 68 +/- 12 years) with relevant aortic stenosis (aortic valve area 0.90 +/- 0.41 cm(2)) were examined by MRI (1.5 T, Philips Intera CV). Contrast-enhanced first pass perfusion was performed with adenosine stress (140 microg/kg/min) and under rest conditions. The results were compared with invasive coronary angiography with regard to the presence of a relevant coronary artery stenosis (>70%). Three of 23 patients (13%) had contraindications for adenosine administration (one patient with atrioventricular block, two patients with mild claustrophobia). In the remaining 20 patients, adenosine stress perfusion could be performed without any complications. CAD was correctly detected in eight patients and correctly ruled out in 10 of 12 patients. False-positive results were seen in two patients with severe myocardial hypertrophy. Sensitivity, specificity, positive predictive value, and negative predictive value were 100%, 80%, 83%, and 100%, respectively. Adenosine stress perfusion can be performed without complications even in patients with high grade aortic stenosis. MRI is helpful to detect and rule out significant CAD in these patients. Severe myocardial hypertrophy may lead to false-positive results. Our initial results indicate that due to a high negative predictive value pre-operative invasive coronary angiography might probably be waived in patients without perfusion defects in stress MRI.

Use of noninvasive tools in primary pulmonary hypertension to assess the correlation of right ventricular function with functional capacity and to predict outcome

Most patients with Primary Pulmonary Hypertension (PPH) have severe exertional limitation which ultimately leads to right heart failure and death. The purpose of the study was to assess the correlation between right ventricular (RV) systolic and diastolic noninvasive variables and exercise tolerance, as well as the predictors of adverse outcome in treated patients.

METHODS

We prospectively studied 29 patients, 17 with PPH and 12 with PPH due to collagen disease. RV parameters were assessed by echocardiography and Radionuclide ventriculography. Pulmonary function and clinical profile were assessed by 6 min walk test and NYHA class. The patients were followed-up during 2 years for cardiac death and cardiac deterioration.

RESULTS

Mean age was 51 +/- 15 years, 22 (78%) women. NYHA class1 in 2 pts, class 2 in 17, class 3 in 8 and class 4 in 2 pts. Pulmonary function (DLCO) was low in 25 (86%) pts, mean 22 +/- 48%. Six minutes walk distance was 358 +/- 132 m, RVEF was 34 +/- 11% (range 16-51%). Among RV variables, RVEF, RA area and TR were independently correlated to 6 min walk. Within follow up of 2 years, there were 10 patients with adverse outcome (4 deaths and 6 deteriorated to NYHA class 3 and 4). Among all clinical and noninvasive variables, RVEF only was correlated to adverse outcome.

CONCLUSION

The noninvasive tests of RVEF, RA size and TR were closely correlated to exercise tolerance. However, among the various clinical, functional and RV variables, RVEF was the only variable correlated with adverse outcome in pts with PPH.

Magnetic resonance imaging is the diagnostic tool of choice in the preoperative evaluation of patients with partial anomalous pulmonary venous return

BACKGROUND

Diagnosis of partial anomalous pulmonary venous return is usually suspected by echocardiography and often confirmed by cardiac catheterization. Magnetic resonance imaging is a powerful non-invasive diagnostic tool that can give accurate insight on systemic and pulmonary veins, cardiac anatomy and physiopathology.

AIM

To test the diagnostic accuracy of magnetic resonance in patient with suspected partial anomalous pulmonary venous return.

CASE PRESENTATION

Twenty consecutive patients (10 male, mean age: 27+/-20 years) with suspected partial anomalous pulmonary venous return underwent a magnetic resonance study comprehensive of Gadolinium-enhanced three-dimensional magnetic resonance angiography and phase-velocity-contrast in order to evaluate pulmonary and systemic venous anatomy and QP/QS. In 14 of them a cardiac catheterization was also performed. Anatomy findings and QP/QS result of both exams were compared. Sixteen patients underwent surgical correction. In the other four patients with QP/QS<1.5, surgical correction was not indicated according to the literature (1). Among patients who had both magnetic resonance and cardiac catheterization (14 patients) anatomical findings were concordant in 12 of them. In all operated patients, surgical findings were concordant with MRI report. There was a good correlation between magnetic resonance and cardiac catheterization QP/QS evaluation (mean value 2.23 and 2.4, respectively).

CONCLUSION

In patients with suspected anomalous pulmonary venous return, magnetic resonance provides a comprehensive evaluation of pulmonary venous return and the amount of shunt, overcoming most of the limitations of echocardiography. Therefore magnetic resonance is a powerful diagnostic tool for indicating therapeutic management and surgical strategies for this group of patients, and can be considered a non-invasive alternative to cardiac catheterization.

Establishing a clinical cardiac MRI service

After several years of research development cardiovascular MRI has evolved into a widely accepted clinical tool. It offers important diagnostic and prognostic information for a variety of clinical indications, which include ischaemic heart disease, cardiomyopathies, valvular dysfunction and congenital heart disorders. It is a safe non-invasive technique that employs a variety of imaging sequences optimized for temporal or spatial resolution, tissue-specific contrast, flow quantification or angiography. Cardiac MRI offers specific advantages over conventional imaging techniques for a significant number of patients. The demand for cardiac MRI studies from cardiothoracic surgeons, cardiologists and other referrers is likely to continue to rise with pressure for more widespread local service provision. Setting up a cardiac MRI service requires careful consideration regarding funding issues and how it will be integrated with existing service provision. The purchase of cardiac phased array coils, monitoring equipment and software upgrades must also be considered, as well as the training needs of those involved. The choice of appropriate imaging protocols will be guided by operator experience, clinical indication and equipment capability, and is likely to evolve as the service develops. Post-processing and offline analysis form a significant part of the time taken to report studies and an efficient method of providing quantitative reports is an important requirement. Collaboration between radiologists and cardiologists is needed to develop a successful service and multi-disciplinary meetings are key component of this. This review will explore these issues from our perspective of a new clinical cardiac MRI service operating over its first year in a teaching hospital imaging department.

Cardiac three-dimensional magnetic resonance imaging and fluoroscopy merging: a new approach for electroanatomic mapping to assist catheter ablation

BACKGROUND

Modern nonfluoroscopic mapping systems construct 3D electroanatomic maps by tracking intracardiac catheters. They require specialized catheters and/or dedicated hardware. We developed a new method for electroanatomic mapping by merging detailed 3D models of the endocardial cavities with fluoroscopic images without the need for specialized hardware. This developmental work focused on the right atrium because of the difficulties in visualizing its anatomic landmarks in 3D with current approaches.

METHODS AND RESULTS

Cardiac MRI images were acquired in 39 patients referred for radiofrequency catheter ablation using balanced steady state free-precession sequences. We optimized acquisition and developed software for construction of detailed 3D models, after contouring of endocardial cavities with cross-checking of different imaging planes. 3D models were then merged with biplane fluoroscopic images by methods for image calibration and registration implemented in a custom software application. The feasibility and accuracy of this merging process were determined in heart-cast experiments and electroanatomic mapping in patients. Right atrial dimensions and relevant anatomic landmarks could be identified and measured in all 3D models. Cephalocaudal, posteroanterior, and lateroseptal diameters were, respectively, 65+/-11, 54+/-11, and 57+/-9 mm; posterior isthmus length was 26+/-6 mm; Eustachian valve height was 5+/-5 mm; and coronary sinus ostium height and width were 16+/-3 and 12+/-3 mm, respectively (n=39). The average alignment error was 0.2+/-0.3 mm in heart casts (n=40) and 1.9 to 2.5 mm in patient experiments (n=9), ie, acceptable for clinical use. In 11 patients, reliable catheter positioning and projection of activation times resulted in 3D electroanatomic maps with an unprecedented level of anatomic detail, which assisted ablation.

CONCLUSIONS

This new approach allows activation visualization in a highly detailed 3D anatomic environment without the need for a specialized nonfluoroscopic mapping system.

Effect of electrical stimulus parameters on the development and propagation of action potentials in short excitable fibres

Intracellular action potentials (IAPs) produced by short fibres in response to their electrical stimulation were analysed. IAPs were calculated on the basis of the Hodgkin-Huxley (1952) model by the method described by Joyner et al. (1978). Principal differences were found in processes of activation of short (semilength L less than 5 lambda) and long fibres under near-threshold stimulation. The shorter the fibre, the lower was the threshold value (Ithr). Dependence of the latency on the stimulus strength (Ist) was substantially non-linear and was affected by the fibre length. Both fibre length and stimulus strength influenced the IAP amplitude, the instantaneous propagation velocity (IPV) and the site of the first origin of the IAP (and, consequently, excitability of the short fibre membrane). With L less than or equal to 2 lambda and Ithr less than or equal to Ist less than or equal to 1.1Ithr, IPV could reach either very high values (so that all the fibre membrane fired practically simultaneously) or even negative values. The latter corresponded to the first origin of the propagated IAP, not at the site of stimulation but at the fibre termination or at a midpoint. The characters of all the above dependencies were unchanged irrespective of the manner of approaching threshold (variation of stimulus duration or its strength). Reasons for differences in processes of activation of short and long fibres are discussed in terms of electrical load and latency. Applications of the results to explain an increased jitter, velocity recovery function and velocity-diameter relationship are also discussed.