MR gradient echo volumetric analysis of human cardiac casts: focus on the right ventricle

Tricuspid Regurgitation and Right Heart Failure: The Role of Imaging in Defining Pathophysiology, Presentation, and Novel Management Strategies

During the last few years, there has been a substantial shift in efforts to understand and manage secondary or functional tricuspid regurgitation (TR) given its prevalence, adverse prognostic impact, and symptom burden associated with progressive right heart failure. Understanding the pathophysiology of TR and right heart failure is crucial for determining the best treatment strategy and improving outcomes. In this article, we review the complex relationship between right heart structural and hemodynamic changes that drive the pathophysiology of secondary TR and discuss the role of multimodality imaging in the diagnosis, management, and determination of outcomes.

Tricuspid Regurgitation and Right Heart Failure: The Role of Imaging in Defining Pathophysiology, Presentation, and Novel Management Strategies

During the last few years, there has been a substantial shift in efforts to understand and manage secondary or functional tricuspid regurgitation (TR) given its prevalence, adverse prognostic impact, and symptom burden associated with progressive right heart failure. Understanding the pathophysiology of TR and right heart failure is crucial for determining the best treatment strategy and improving outcomes. In this article, we review the complex relationship between right heart structural and hemodynamic changes that drive the pathophysiology of secondary TR and discuss the role of multimodality imaging in the diagnosis, management, and determination of outcomes.

Assessment of the tricuspid valve using cardiovascular magnetic resonance

PURPOSE OF REVIEW

The rapid search for suitable tricuspid transcatheter devices has ignited renewed enthusiasm in accurate characterization of tricuspid valve disease. Cardiovascular magnetic resonance (CMR), traditionally used as the gold standard in assessment for right ventricular size and function, has recently seen its use expanded to assess both the structure and function of the tricuspid apparatus. This review will highlight the role of CMR in tricuspid valve disease and compare it with other commonly used imaging modalities.

RECENT FINDINGS

Dynamic anatomical assessment of the tricuspid apparatus, in combination with accurate leaflet identification, is possible with CMR. Tricuspid regurgitation volume and fraction are derived through an indirect volumetric method, and therefore, able to overcome many traditional hurdles involved with valve regurgitation quantitation. Adverse right heart prognostic factors in tricuspid valve disease, such as right heart volumes, function, and tissue characterization, are optimally assessed using CMR.

SUMMARY

Cardiovascular magnetic resonance is a powerful modality that should be harnessed in order to obtain a multifaceted assessment of tricuspid valve structure, function, and the effects of valve disease on right heart remodeling.

Right atrium and cryptogenic ischaemic stroke in the young: a case-control study

Background

Recent studies suggest left atrial (LA) dysfunction in cryptogenic stroke. We studied the dynamics of right atrium (RA) and right atrial appendage (RAA) in young adults with cryptogenic stroke. We hypothesised that bi-atrial dysfunction and blood stagnation might contribute to thrombosis formation in patients with patent foramen ovale (PFO), as deep venous thrombosis is detected only in the minority of patients.

Methods

Thirty patients (aged 18–49) with a first-ever cryptogenic stroke and 30 age-matched and sex-matched stroke-free controls underwent cardiac magnetic resonance (CMR) imaging. An approach to estimate the RAA volume was developed, using crista terminalis and pectinate muscles as anatomical landmarks. Atrial expansion indices were calculated as (maximal volume – minimal volume) ×100%/minimal volume. Total pulmonary to systemic blood flow ratio (Qp/Qs) was based on phase contrast CMR. Right-to-left shunt (RLS) was evaluated with transoesophageal echocardiography in 29 patients and transcranial Doppler in 30 controls, moderate-to-severe RLS considered as clinically significant.

Results

We found that RA and RAA volumes were similar between patients and controls. Also, RA expansion index was similar, but RAA (95.6%±21.6% vs 108.7%±25.8%, p=0.026) and LA (126.2%±28% vs 144.9%±36.3%, p=0.023) expansion indices were lower in patients compared with controls. Seven (24%) of 29 patients had an RLS compared with 1 (3%) of 30 controls (p=0.012). Among 59 study subjects, RLS was associated with lower RA (81.9%±15.9% vs 98.5%±29.5%, p=0.030), RAA (84.7%±18% vs 105.6%±24.1%, p=0.022), LA (109.8%±18.6% vs 140.1%±33.7%, p=0.017) and LAA (median 102.9% (IQR 65.6%–121.7%) vs 229.1% (151.8%–337.5%], p=0.002) expansion indices and lower Qp/Qs ratio (0.91±0.06 vs 0.98±0.07, p=0.027).

Conclusions

This study suggests bi-atrial dysfunction in young adults with cryptogenic stroke, associated with moderate-to-severe RLS. Dysfunction of the atria and atrial appendages may be an additional mechanism for PFO-related stroke.

Trial registration number

NCT01934725.

Multimodality Imaging of the Tricuspid Valve and Right Heart Anatomy

The characterization of tricuspid valve and right-heart anatomy has been gaining significant interest in the setting of new percutaneous transcatheter interventions for tricuspid regurgitation. Multimodality cardiac imaging provides a wealth of information about the anatomy and function of the tricuspid valve apparatus, right ventricle, and right atrium, which is pivotal for diagnosis and prognosis and for planning of percutaneous interventions. The present review describes the role of echocardiography, cardiac magnetic resonance, and multidetector row cardiac computed tomography for right heart and tricuspid valve assessment.

Right Ventricular Analysis Using Real-time Three-dimensional Echocardiography for Preload Dependency

BACKGROUND

The importance of the right ventricle (RV) has been increasingly recognized, and accurate RV measurement has become necessary. However, assessment of the RV with two-dimensional (2D) echocardiography has several limitations. As the development of novel methods for RV measurement continues, we can expect more accordant values related to RV geometry.

METHODS

Fifty-eight subjects who were examined by transthoracic echocardiography (TTE) immediately before and after hemodialysis (HD) were enrolled. Real-time, full-volume, three-dimensional (3D) echocardiographic images were acquired and analyzed using dedicated software. Conventional RV parameters for RV size and function were measured for comparison with pre-HD and post-HD values by both 2D-TTE and 3D-TTE.

RESULTS

3D RV volumes and ejection fractions were significantly decreased after HD. The values of the 3D image-derived RV dimensions, tricuspid annular plane systolic excursion (TAPSE), fractional area change (FAC), and longitudinal strain were also affected by acute preload changes (TAPSE pre-HD: 22.4 ± 4.0 mm, post-HD: 19.0 ± 4.2 mm, p < 0.001; FAC pre-HD: 49.6% ± 5.9%, post-HD: 46.4% ± 5.5%, p < 0.001; septal longitudinal strain pre-HD: -20.1% ± 3.7%, post-HD: -16.8% ± 3.8%, p < 0.001). With the exception of FAC, most 2D RV parameters were well correlated with the 3D values.

CONCLUSIONS

Various parameters representing RV anatomy and function were acquired easily and more accurately from 3D echocardiographic images than from 2D images but were affected by acute preload changes. 3D TTE could be a new modality for assessing RV function and size, but each value from 3D TTE should be interpreted with caution while considering the loading condition of the patients.

Validation of 3D echocardiographic volume detection of left atrium by human cadaveric casts

BACKGROUND

Left atrial volume is a prognostic factor in cardiac pathologies. We aimed to validate left atrial volume detection with 3D and 2D echocardiography (3DE and 2DE) by human cadaveric casts. 3DE facilitates measurement of atrial volume without geometrical assumptions or dependence on imaging angle in contrast to 2DE methods.

METHODS

For method validation, six water-filled balloons were submerged in a 20-l water tank and their volumes were measured with 3DE. Seven human cadaveric left atrial casts were prepared of silicone and were transformed into ultrasound-permeable casts. Casts were imaged in the same setting, so that 3DE and 2DE of casts represented transthoracic apical view. Left ventricle analysis softwares GE 4D Auto LVQ and TomTec 4D LV-Function were used for 3DE volumetry.

RESULTS

Balloon volumes ranged 37 to 255 ml (mean 126 ml). 3DE resulted in an excellent volumetric agreement with balloon volumes, absolute bias was - 3.7 ml (95% CI -5.9 to - 1.4). Atrial cast volumes were 38 to 94 ml (mean 56.6 ml). 3DE and 2DE volumes were excellently correlated with cast volumes (r = 0.96 to 0.99). Biases were for GE 4D LVQ -0.7 ml (95% CI -6.1 to 4.6), TomTec 4D LV-Function 3.3 ml (- 1.9 to 8.5) and 2DE 2.9 ml (- 4.0 to 9.9). 3DE resulted in lower limits of agreement and showed no volume-related bias in contrast to area-length method.

CONCLUSIONS

We conclude that measurement of human cadaveric left atrial cast volumes by 3DE is in excellent agreement with true cast volumes.

The Accuracy of Left Ventricular and Left Atrial Volumetry Using 64-Slice Computed Tomography: In Vitro Validation Study With Human Cardiac Cadaveric Casts

OBJECTIVE

We aimed to validate the accuracy of imaging of left atrial and ventricular volumes using cardiac cadaveric silicone casts.

METHODS

Left atrial (n = 14) and ventricular (n = 15) casts were imaged using 64-slice computed tomography (CT). Water displacement (WD) of cardiac casts was used as the gold standard for volume measurements.

RESULTS

Compared with WD, CT resulted in slightly higher left atrial and ventricular volumes (54 ± 25 vs 56 ± 26 mL [P = 0.003] and 57 ± 47 vs 66 ± 47 mL [P = 0.0001]). Variability between left atrial and ventricular volumes by CT and WD was low (coefficients of variation [CVs], 4% [intraclass correlation coefficient {ICC}, 0.99] and 12% [ICC, 0.97]). Intraobserver variability of CT was low for both the left atrium and the left ventricle (CVs, 1% [ICC, 1.00] and 4% [ICC, 1.00]).

CONCLUSIONS

Cardiac CT is both accurate and reproducible in assessment of left ventricular and atrial chamber volumes.

Alpha shape theory for 3D visualization and volumetric measurement of brain tumor progression using magnetic resonance images

Resection of brain tumors is a tricky task in surgery due to its direct influence on the patients' survival rate. Determining the tumor resection extent for its complete information via-à-vis volume and dimensions in pre- and post-operative Magnetic Resonance Images (MRI) requires accurate estimation and comparison. The active contour segmentation technique is used to segment brain tumors on pre-operative MR images using self-developed software. Tumor volume is acquired from its contours via alpha shape theory. The graphical user interface is developed for rendering, visualizing and estimating the volume of a brain tumor. Internet Brain Segmentation Repository dataset (IBSR) is employed to analyze and determine the repeatability and reproducibility of tumor volume. Accuracy of the method is validated by comparing the estimated volume using the proposed method with that of gold-standard. Segmentation by active contour technique is found to be capable of detecting the brain tumor boundaries. Furthermore, the volume description and visualization enable an interactive examination of tumor tissue and its surrounding. Admirable features of our results demonstrate that alpha shape theory in comparison to other existing standard methods is superior for precise volumetric measurement of tumor.

Assessment of left and right ventricular parameters in healthy Korean volunteers using cardiac magnetic resonance imaging: change in ventricular volume and function based on age, gender and body surface area

The clinical utility of cardiac magnetic resonance imaging (CMR) is growing and is being used predominantly as a means of measuring ventricular function. The normal reference range of ventricular function may vary based on age, sex and ethnicity. At present, most CMR reference values for healthy individuals have been reported from Western countries. The intent of this study was to investigate the normal CMR reference range for left ventricular (LV) and right ventricular (RV) parameters in healthy Koreans. Healthy volunteers between the ages of 20-70 years without any history of cardiovascular disease or associated risk factors were prospectively recruited to be a part of this study. A total of 124 patients were recruited for this study. Steady-state free precession pulse sequences were used to obtain the cine images for LV and RV volume analysis. All parameters were analyzed based on age and gender, and normalized to body surface area (BSA). LV volume, mass and cardiac output were significantly greater in males than in females. However, all of these parameters which are associated with BSA and gender differences disappeared when corrected for BSA. RV volume was less in females even after the data was normalized for BSA. LV and RV volumes normalized for BSA gradually decreased with greater age, whereas the ejection fraction increased with age, thus maintaining the stroke volume index and cardiac index. LV and RV volumes, mass and function values for a healthy population largely depend on BSA and should be evaluated after normalization by BSA. LV parameters show no difference based on gender, but RV volume is less in the female. Greater age is associated with less ventricular volume, suggesting the possibility of volume sensitivity in the elderly.

Quantitative analysis of right ventricular function in patients with pulmonary hypertension using three-dimensional echocardiography and a two-dimensional summation method compared to magnetic resonance imaging

Magnetic resonance imaging (MRI) is considered the clinical reference standard for measuring the right ventricular (RV) volume and ejection fraction, although real-time 3-dimensional echocardiography (RT3DE) would be a preferred method owing to its convenience and availability for repetitive examinations. However, the feasibility, accuracy, and reproducibility of RT3DE have not been fully examined. The present study sought to validate the correlation of RT3DE with a 2-dimensional summation method compared to MRI for assessing the function of the right ventricle and to evaluate the RV function in patients with pulmonary hypertension (PH). Thirty patients with PH underwent both RT3DE and MRI. The right ventricle was reconstructed with RT3DE using a 2-dimensional summation method to analyze the MRI measurements. The RV end-diastolic volume, RV end-systolic volume, and RV ejection fraction were measured. Fifteen normal subjects underwent the same echocardiographic protocol for comparison. The RV end-diastolic volume index, RV end-systolic volume index, and RV ejection fraction measured using RT3DE correlated well with those measured using MRI (R = 0.96, p <0.001; R = 0.96, p <0.001; p = 0.93, and p <0.001, respectively). All inter- and intraobserver variability values for the RV end-diastolic volume, RV end-systolic volume, and RV ejection fraction were <17%. Both the RV end-diastolic volume index and the RV end-systolic volume index were significantly enlarged in those with PH compared to those in the normal subjects (RVEDVI 123 ± 42 ml/m² vs 74 ± 12 ml/m²; RVESVI 86 ± 33 ml/m² vs 26 ± 5 ml/m² in those with PH and the normal subjects, respectively, p <0.0001). In contrast, the RV ejection fraction was significantly reduced in the patients with PH compared to that in the normal subjects (30 ± 12% vs 65 ± 6%, respectively, p <0.01). Thus, RT3DE with a 2-dimensional summation method might provide comparable and feasible measurements of the RV volume in patients with PH compared to MRI.

Ventricular restraint therapy for heart failure: the right ventricle is different from the left ventricle

OBJECTIVE

Effects of ventricular restraint on the left ventricle are well documented, but effects on the right ventricle are not. We hypothesized that restraint affects the right and left ventricles differently.

METHODS

We studied acute effects of restraint on left and right ventricular mechanics in healthy sheep (n = 14) with our previously described technique of adjustable and measurable restraint. Transmural pressure, myocardial oxygen consumption indices, diastolic compliance, and end-systolic elastance were assessed at 4 restraint levels for both ventricles. We then studied long-term effects of restraint for 4 months in an ovine model of ischemic dilated cardiomyopathy (n = 6). Heart failure was induced by coronary artery ligation, and polypropylene mesh was wrapped around the heart to simulate clinical restraint therapy. All subjects were followed up with serial cardiac magnetic resonance imaging to assess left and right ventricular volumes and function.

RESULTS

Restraint decreased left ventricular transmural pressure (P < .03) and myocardial oxygen consumption indices (P < .05) but not left ventricular diastolic compliance (P = .52). Restraint had no effect on right ventricular transmural pressure (P = .82) or myocardial oxygen consumption indices (P = .72) but reduced right ventricular diastolic compliance (P < .01). In long-term studies, restraint led to reverse left ventricular remodeling with decreased left ventricular end-diastolic volume (P < .006) but did not affect right ventricular end-diastolic volume (P = .82).

CONCLUSIONS

Ventricular restraint affects the left and right ventricles differently. Benefits of restraint for right ventricular function are unclear. The left ventricle can tolerate more restraint than the right ventricle. With current devices, the right ventricle may limit overall therapeutic efficacy.

Effect of angiotensin receptor blockade on systemic right ventricular function and size: a small, randomized, placebo-controlled study

INTRODUCTION

The effects of angiotensin converting enzyme inhibitor on systemic right ventricular size and function are unknown.

METHODS

Prospective, double blind, randomized, placebo-controlled clinical trial of 1-year therapy with Ramipril in adult patients with DTGA status postatrial baffle procedure. Primary endpoints were change in systemic right ventricular ejection fraction (RVEF) and right ventricular size assessed by magnetic resonance imaging (MRI).

RESULTS

Seventeen patients were enrolled into the study. Mean age at study enrollment was 26.4+/-5.2 years. Mean baseline RVEF was 44+/-6.5%, mean RVEDV was 206.3+/-75.5 ml. Eight patients were randomized to the treatment group and 9 patients were randomized to the placebo group. RVEF did not improve in the Ramipril group from baseline to 1 year (43.8+/-7.1% vs. 40.9+/-13.3%, p=0.52) and remain unchanged in the placebo group (44.3+/-6.3 vs. 46.3+/-9.6%, p=0.42). RVEDV (184.5+/-56.4 ml vs. 179.6+/-66.4 ml, p=0.64) and RVESV (109.5+/-19.4 ml vs. 111.8+/-30.1, p=0.74) remained unchanged in the Ramipril group from baseline to 1 year as well as in the placebo group (228.1+/-89.2 ml vs. 204.5+/-50.4 ml, p=0.42 and 117.5+/-36.9 ml vs. 117.4+/-26.2 ml, p=0.99, respectively).

CONCLUSION

One-year treatment with Ramipril does not seem to affect right ventricular function or size in adult patients with systemic right ventricles after a Mustard or Senning procedure.

CONDENSED ABSTRACT

17 Adult patients (mean age of 26.4 +/- 5.2 years) with systemic right ventricles were blindly randomized to 1-year treatment with Ramipril placebo. Systemic right ventricular function (RVEF) and size (RVEDV) were assessed by magnetic resonance imaging at baseline and 1 year. RVEF failed to improve in the Ramipril group (43.8+/-7.1% vs. 40.9+/-13.3%, p=0.52) and remain unchanged in the placebo group (44.3+/-6.3 vs. 46.3+/-9.6%, p=0.42). RVEDV remained unchanged in the study group (184.5+/-56.4 ml vs. 179.6+/-66.4 ml, p=0.64 as well as in the placebo group (228.1 +/- 89.2 ml vs. 204.5 +/- 50.4 ml, p = 0.42). One-year treatment with Ramipril does not improve right ventricular function or attenuate remodeling in adult patients with systemic right ventricles.

Right ventricular parameters: prospect for routine assessment by equilibrium radionuclide angiographic SPECT

While left ventricular (LV) function is assessed routinely for heart disease, right ventricular (RV) assessment has attracted relatively little attention due to technical difficulties, even though RV function plays an important role in determining prognosis. This issue of the Communications includes a report that a SPECT ERNA algorithm applied to data for patients with tetralogy of Fallot exhibited RV dysfunction compared to normal subjects, as reported previously using different ERNA SPECT algorithms. That ERNA SPECT methods appear to produce results that are expected of patient group who should exhibit RV abnormalities presents the prospect that such algorithms also could be used to evaluate whether patients undergoing chemotherapy with anthracyclines and other cardiotoxic chemotherapeutic agents become at risk of developing RV, as well as, LV dysfunction. SPECT ERNA may well become the standard test for monitoring RV and LV components of heart disease in managing patients undergoing chemotherapy.

Predicting outcome of pulmonary valve replacement in adult tetralogy of Fallot patients

BACKGROUND

Predicting changes in right ventricular (RV) size and function after pulmonary valve replacement (PVR) is important for timely reintervention in adult tetralogy of Fallot patients.

METHODS

We analyzed the influence of pulmonary regurgitation severity and RV size and function before PVR on the outcome of RV size and function after PVR in 27 adult Fallot patients who had cardiac magnetic resonance imaging before and after PVR. RV dimensions were indexed for body surface area.

RESULTS

Pulmonary regurgitation (48% +/- 11% of RV stroke volume) was not related to RV dimensions and function before PVR. Moreover, severity of pulmonary regurgitation did not influence changes in RV dimensions after PVR. The indexed RV end-systolic volume before PVR (mean, 98 mL/m2; range, 52 to 235 mL/m2) best predicted the indexed RV end-systolic volume after PVR (mean, 59 mL/m2; range, 24 to 132 mL/m2, r = 0.78, p < 0.001) and the indexed RV end-diastolic volume after PVR (mean, 107 mL/m2; range, 70 to 170 mL/m2, r = 0.73, p < 0.001). Baseline RV ejection fraction corrected for valvular insufficiencies and shunting (21% +/- 7%) best predicted the RV ejection fraction after PVR (43% +/- 10%, r = 0.77, p < 0.001).

CONCLUSIONS

Timing of PVR should be based on indexed RV end-systolic volume and corrected RV ejection fraction rather than on severity of pulmonary regurgitation.

Right ventricular dysfunction assessed by cardiovascular magnetic resonance imaging predicts poor prognosis late after myocardial infarction

OBJECTIVES

We sought to determine whether right ventricular (RV) function late after myocardial infarction (MI) impacts long-term prognosis.

BACKGROUND

Right ventricular failure predicts early mortality in patients with acute MI. The prognostic impact of RV function late after MI is not well defined. Accordingly, we determined whether RV dysfunction late after MI influences survival beyond traditional risk predictors, including patient age, left ventricular ejection fraction (LVEF), and infarct size.

METHODS

We studied 147 consecutive patients >30 days after MI (mean age of infarct 6.7 +/- 8.2 years) who were referred for contrast-enhanced cardiovascular magnetic resonance imaging. We assessed hazard ratios for death by RV ejection fraction (RVEF). The association of RVEF with mortality adjusted to traditional risk predictors was examined by using multivariable Cox proportional hazards regression models.

RESULTS

A total of 26 deaths occurred during a median follow-up of 17 months (range 6 to 53 months). By univariable analysis, RVEF <40% was strongly associated with mortality (unadjusted hazard ratio 4.02; p = 0.0007). By multivariable analysis that adjusted for patient age, left ventricular (LV) infarct size, and LVEF, RVEF <40% remained a significant independent predictor of mortality (adjusted hazard ratio 2.86; p = 0.03).

CONCLUSIONS

Right ventricular ejection fraction quantified late after MI is an important predictor of prognosis adjusted for patient age, LV infarct size, and LVEF. Accordingly, evaluation of RVEF using cardiovascular magnetic resonance imaging can improve risk-stratification and potentially refine patient management after MI.

CMR of Ventricular Function

Cardiovascular magnetic resonance (CMR) is the reference standard for the assessment of ventricular dimensions, function, and mass in terms of accuracy and reproducibility. It has been thoroughly validated both ex vivo and against other imaging techniques. Measurements are highly accurate and no geometrical assumptions need to be made about the ventricle. A routine ventricular dataset of images can be acquired in less than 5 minutes and analyzed in about the same time. The field is rapidly advancing with increasing automation and simplification in both image acquisition and analysis. Using parallel and real time imaging techniques, good quality data can be obtained even in patients who are unable to hold their breath. While providing useful information in all patients with suspected heart failure, CMR should particularly be considered in those with poor echo windows, where it can also be combined with myocardial stress. Tagging techniques can provide highly detailed information about myocardial torsion and strain for individual myocardial segments. In a research environment, the very high degree of interscan reproducibility can dramatically reduce the number of patients needed to perform clinical trials.

Modified RV short axis series--a new method for cardiac MRI measurement of right ventricular volumes

PURPOSE

The current standard image orientation employed in the MRI assessment of right ventricular volumes uses a series of short axis cine acquisitions located with respect to a horizontal long axis view with the first slice placed across the atrio-ventricular valve plane at end diastole. Inherent inaccuracies are encountered with the use of this image orientation due to difficulty in defining the tricuspid valve and the border between atrium and ventricle on the resultant images. Our experience indicates that because the tricuspid valve is usually not in-plane in the slice the atrio-ventricular margin is difficult to distinguish. This leads to inaccuracies in measurements at the base of the RV and miscalculation of the RV volume. The purpose of this study was to assess an alternative method of image orientation aimed at increasing the accuracy of RV volume measurements using current commercially available CMRI sequences. This technique, the modified RV short axis series, is oriented to the outflow tract of the right ventricle.

METHOD

We undertook a prospective study of 50 post cardiac transplant patients. A series of LV short axis multi-slice cine acquisition FIESTA images was acquired using the current standard technique. From this data set, LV and RV stroke volumes were derived on an Advantage Windows workstation using planimetry of the endocardial and epicardial borders in end systole and end diastole. Our new technique involved obtaining a set of multi-slice cine acquisition FIESTA images in a plane perpendicular to a line from the centre of the pulmonary valve to the apex of the RV. Planimetry of the RV was then performed and a stroke volume calculated using the same method of analysis. RV stroke volumes obtained from both techniques were compared with LV stroke volumes. Three operators independently derived RV data sets.

RESULTS

On the images acquired with the new technique, the tricuspid valve was easier to define leading to more accurate and reproducible planimetry of ventricular borders. RV stroke volumes calculated from the new method showed better agreement with LV stroke volumes than with the current method. These results were consistent across the three operators.

CONCLUSIONS

This new method improves visualisation of the tricuspid valve and makes analysis easier and less prone to operator error than the current standard technique for MRI assessment of RV volumes.

Cardiovascular magnetic resonance in the quantitative assessment of left ventricular mass, volumes and contractile function

Cardiovascular magnetic resonance is a well validated, highly accurate and reproducible technique for the assessment of ventricular volumes, function and mass. State of the art cardiovascular magnetic resonance practice is capable of a ventricular assessment that includes not only systolic but also diastolic function. Thus, it provides an insight into the complex changes in ventricular morphology, physiology and function in cardiovascular disease. This has produced great interest not only in its clinical utilization but also as an important research tool. As refinement of the technique continues to incorporate hardware and software developments, the technique becomes quicker, more accurate and easier to analyse. Here, we review recent developments and current practice.

Optimal timing for pulmonary valve replacement in adults after tetralogy of Fallot repair

The timing of pulmonary valve replacement in adult patients with repaired tetralogy of Fallot remains controversial. A magnetic resonance imaging study in 17 adult patients with repaired tetralogy of Fallot reveals a statistically significant decrease in right ventricular (RV) volume (RV end-diastolic volume 163 +/- 34 to 107 +/- 26 ml/m2, p <0.001; RV end-systolic volume 109 +/- 27 to 69 +/- 22 ml/m2, p <0.001) at a mean follow-up of 21 months after pulmonary valve replacement; whereas RV systolic function remained unchanged (mean RV ejection fraction 32 +/- 7% to 34 +/- 10%, p = 0.12). In no patients with a RV end-diastolic volume >170 ml/m2 or a RV end-systolic volume >85 ml/m2 before pulmonary valve replacement were RV volumes "normalized" after surgery.

Model dependence of gated blood pool SPECT ventricular function measurements

BACKGROUND

Calculation differences between various gated blood pool (GBP) single photon emission computed tomography (SPECT) (GBPS) algorithms may arise as a result of different modeling assumptions. Little information has been available thus far regarding differences for right ventricular (RV) function calculations, for which GBPS may be uniquely well suited.

METHODS AND RESULTS

Measurements of QBS (Cedars-Sinai Medical Center, Los Angeles, Calif) and BP-SPECT (Columbia University, New York, NY) algorithms were evaluated. QBS and BP-SPECT left ventricular (LV) ejection fraction (EF) correlated strongly with conventional planar-GBP LVEF for 422 patients (r = 0.81 vs r = 0.83). QBS correlated significantly more strongly with BP-SPECT for LVEF than for RVEF (r = 0.80 vs r = 0.41). Both algorithms demonstrated significant gender differences for 31 normal subjects. BP-SPECT normal LVEF (67% +/- 9%) was significantly closer to values in the magnetic resonance imaging (MRI) literature (68% +/- 5%) than QBS (58% +/- 9%), but both algorithms underestimated normal RVEF (52% +/- 7% and 50% +/- 9%) compared with the MRI literature (64% +/- 9%). For 21 patients, QBS correlated similarly to MRI as BP-SPECT for LVEF (r = 0.80 vs r = 0.85) but RVEF correlation was significantly weaker (r = 0.47 vs r = 0.81). For 16 dynamic phantom simulations, QBS LVEF correlated similarly to BP-SPECT (r = 0.81 vs r = 0.91) but QBS RVEF correlation was significantly weaker (r = 0.62 vs r = 0.82). Volumes were lower by QBS than BP-SPECT for all data types.

CONCLUSIONS

Both algorithms produced LV parameters that correlated strongly with all forms of image data, but all QBS RV relationships were significantly different from BP-SPECT RV relationships. Differences between the two algorithms were attributed to differences in their underlying ventricular modeling assumptions.

Right ventricular volume measurement by conductance catheter

Continuous ventricular volume measurement by the conductance method assumes a homogeneous electrical field dispersed throughout and contained within the ventricle. Because of dense trabeculation and complex geometry, right ventricular (RV) volume description by this method may be seriously compromised. This study sought to determine the accuracy and limitations of RV volume measurement by conductance, with magnetic resonance (MR) imaging (MRI) used as a reference, in the porcine RV. Anesthetized pigs (n = 5, 45-55 kg) were placed in a 1.5-T magnet, and ECG-gated transverse MR images (5-mm slices) were acquired during the complete cardiac cycle. RV cavity volumes were subsequently determined by Simpson's technique. Animals were then instrumented with an RV conductance catheter and an ultrasonic pulmonary artery flow probe. Conductance catheter signals were recorded using single- and dual-field (SF and DF) excitation, and the saline-dilution technique was used to correct volumes for parallel conductance. The gain factor (alpha) was calculated as the ratio of conductance- to MRI-derived stroke volume (alpha SV). Variation of alpha during the cardiac cycle was computed by comparing RV conductance volumes with 1) MRI volumes at isochronal time points within the cardiac cycle [alpha(t)] and 2) the pulmonary flow integral during ejection. After calibration, the conductance-MRI volume relation was modeled linearly with good correlation [r = 0.96 (SF) and r = 0.94 (DF)], close to the line of identity. Individual conductance-MRI plots displayed a slight curvilinear relation that was concave toward the MRI axis. Consistent with this finding, alpha(t) varied significantly during the cardiac cycle (0.49 and 0.39 by SF for end systole and end diastole, respectively, P = 0.011). DF excitation resulted in improved volume measurement [alpha SV = 0.41 (SF) and 0.96 (DF)], with less variation in alpha(t) (1.0 and 0.92 by DF for end systole and end diastole, respectively, P = 0.66). These results indicate that, with calibration, the conductance method can measure absolute RV volume under steady-state conditions. However, the curvilinearity and alpha(t) variation would indicate the potential for nonlinearity when RV volumes are varied over a wider range.

Time course of right ventricular remodeling in rats with experimental myocardial infarction

Right ventricular (RV) weight increases dependent on time after myocardial infarction (MI) and on MI size. The sequential changes in RV volume and hemodynamics and their relations to left ventricular (LV) remodeling after MI are unknown. We therefore examined the time course of RV remodeling in rats with LV MI. MI was produced by left coronary artery ligation. Four, eight, and sixteen weeks later, LV and RV hemodynamic measurements were performed and pressure-volume curves were obtained. For serial measurement of RV volumes and performance, cine-MRI was performed 2 and 8 wk after MI. The ratios of beta-myosin heavy chain (MHC) to alpha-MHC and skeletal to cardiac alpha-actin were determined for the RV and LV after large MI or sham operation. RV weight increased in rats with MI, as did RV volume. RV pressure-volume curves were shifted toward larger volumes 16 wk after large MI. RV systolic pressure increased gradually over time; however, the gain in RV weight was always in excess of RV systolic pressure. The ratios of skeletal to cardiac alpha-actin and beta-MHC to alpha-MHC were increased after MI in both ventricles in a similar fashion. Because RV wall stress was not increased after infarction, mechanical factors may not conclusively explain hypertrophy, which maintained balanced loading conditions for the RV even after large LV infarction.

Evaluation of methods for MR imaging of human right ventricular heart volumes and mass

PURPOSE

To assess the utility of two different imaging directions in the evaluation of human right ventricular (RV) heart volumes and mass with MR imaging; to compare breath-hold vs. non-breath-hold imaging in volume analysis; and to compare turbo inversion recovery imaging (TIR) with gradient echo imaging in RV mass measurement.

MATERIAL AND METHODS

We examined 12 healthy volunteers (age 27-59 years). Breath-hold gradient echo MR imaging was performed in two imaging planes: 1) perpendicular to the RV inflow tract (RVIT view), and 2) in the transaxial view (TA view). The imaging was repeated in the TA view while the subjects were breathing freely. To analyze RV mass using TIR images, the RV was again imaged at end-diastole using the two views. The RV end-diastolic cavity (RVEDV) and muscle volume as well as end-systolic cavity volume (RVESV) were determined with the method of discs. All measurements were done blindly twice to assess repeatability of image analysis. To assess reproducibility of the measurements, 6 of the subjects were imaged twice at an interval of 5-9 weeks.

RESULTS

RVEDV averaged 133.2 ml, RVESV 61.5 ml and the RVmass 46.2 g in the RVIT view and 119.9 ml, 56.9 ml and 38.3 g in the TA view, respectively. The volumes obtained with breath-holding were slightly but not significantly smaller than the volumes obtained during normal breathing. There were no marked differences in the RV muscle mass obtained with gradient echo imaging compared to TIR imaging in either views. Repeatability of volume analysis was better in TA than RVIT view: the mean differences were 0.7 +/- 4.0 ml and - 5.4 +/- 14.0 ml in end-diastole and 1.6 +/- 3.1 ml and - 1.5 +/- 13.9 ml in end-systole, respectively. Repeatability of mass analysis was good in both TIR and cine images in the RVIT view but slightly better in TIR images: - 0.5 +/ -2.4 g compared to 0.8 +/- 2.9 g in cine images. Reproducibility of imaging was good, mean differences for RVEDV and RVESV were -1.0 +/- 4.8 ml and -0.8 +/- 2.8 ml, respectively. Mean difference for RVmass was -0.9 +/- 2.6 g.

CONCLUSION

The present study suggests that gradient echo MR imaging is well applicable to RV volume and mass measurements. The best imaging plane for volumetric analysis seems to be the TA plane and there was no significant difference between breath-hold and conventional imaging. To assess RV mass, we recommend RVIT view; the TIR sequence quickly produced images of better quality compared to gradient echo images but no significant difference between masses was found and repeatability of analysis was equally good with both methods.

Quantification of global and regional ventricular function in cardiac magnetic resonance imaging

One of the strong assets of cardiac magnetic resonance (CMR) is its ability to assess myocardial anatomy, structure, function, flow, and perfusion within a single examination. Quantification of global and regional function from magnetic resonance imaging (MRI) studies was shown to be accurate and reproducible in experimental and clinical research studies. With the advent of high-performance MRI scanners and newly developed pulse sequences, image acquisition times have been reduced considerably in recent years. However, the clinical use of CMR remains limited for various reasons. Among these limitations is that the amount of images obtained in a typical cardiac examination is so large that visual and especially quantitative image analysis is tedious and time consuming. There is an urgent need for optimized dedicated software tools featuring highly automated contour detection and optimized display capabilities to present the quantitative results to the physician in an orderly fashion, thus facilitating clinical decision making. This article focuses on the state of the art in CMR postprocessing techniques for quantitative assessment of global and regional function.