Loss of troponin-T labelling in endomyocardial biopsies of cardiac transplant patients is associated with increased rejection grading.

Acute cellular rejection after cardiac transplantation surgery is routinely monitored by pathological assessment of haematoxylin and eosin (H&E) histology of endomyocardial biopsies (EMB). Unfortunately, there is considerable variation in the diagnosis of rejection that has been attributed to the subjectivity involved in assessing the degree of (a) inflammatory infiltrate and (b) myocyte damage. In this work, we sought to investigate the potential of high contrast confocal microscopy for numerically assessing inflammatory infiltrate and myocyte damage in EMB histology. Confocal microscopy was used to capture images from EMB fluorescently labelled for nuclei (DAPI), f-actin (phalloidin), troponin-T (anti-body), and extracellular matrix and cell border (wheat germ agglutinin). Images from 28 biopsy procedures were captured. Standard pathological grading of H&E histology identified the following rejection gradings: 6 0R, 16 1R, 6 2R and no 3R. Confocal imaging was able to identify equivalent features of rejection provided by H&E histology but at higher contrast facilitating quantification. Lymphocytic infiltrate was calculated as the ratio of non-myocyte nuclei to total nuclei. This metric was found to be significantly higher in the biopsies from 2R patients compared to both 1R and 0R patients (P < .05). Myocyte damage was quantified as the loss of troponin-T labelling normalised to f-actin labelling. This metric of myocyte damage found significantly lower amounts of troponin-T in the biopsies from 2R patients compared to those with a 0R rejection grading (P < .05). Confocal imaging and simple image processing routines show potential for numerically assessing both inflammatory infiltrate and myocyte damage in endomyocardial biopsy.

Characteristics and Outcomes of Patients With Severe Aortic Stenosis Discussed by the Multidisciplinary "Heart Team" According to Treatment Allocation.

BACKGROUND: Transcatheter aortic valve implantation (TAVI) is an alternative and effective contemporary intervention to surgical aortic valve replacement (SAVR) for patients with severe aortic valve disease at increased surgical risk. Guidelines recommend a multidisciplinary "Heart Team" (MHT) review of patients considered for a TAVI procedure, but this has been little studied. We reviewed the characteristics, treatments and outcomes of such patients reviewed by the MHT at our centre. METHODS: Data on consecutive patients with severe aortic valve stenosis discussed by the Auckland City Hospital MHT from June 2011 to August 2016 were obtained from clinical records. Patient characteristics, treatment and outcomes were analysed using standard statistical methods. RESULTS: Over the 5-year period 243 patients (mean age 80.2 ± 8.0 years, 60% male) were presented at the MHT meeting. TAVI was recommended for 200, SAVR for 26 and medical therapy for 17 patients, with no significant difference in mean age (80.2 ± 8.3, 80.4 ± 6.1, 80.4 ± 7.3 years, respectively) or EuroSCORE II (6.5 ± 4.7%, 5.3 ± 3.6%, 6.7 ± 4.3%, respectively). Over time, there was an increase in the number of patients discussed and treated, with no change in their mean age, but the mean EuroSCORE II significantly decreased (TAVI p = 0.026, SAVR p = 0.004). Survival after TAVI and SAVR was similar to that of the age-matched general population, but superior to medical therapy p = 0.002 (93% (n = 162), 84% (n = 21) and 73% (n = 18) at one year and 85% (n = 149), 84% (n = 21) and 54% (n = 13) at 2 years, respectively). CONCLUSIONS: An increasing number of patients were discussed at the MHT meeting with the majority undergoing TAVI, with a similar age and EuroSCORE II to those allocated SAVR or medical therapy. Survival following TAVI and SAVR was superior to medical therapy and similar to the age-matched general population. These findings suggest that the MHT process is robust, consistent and appropriately allocating a limited treatment resource.

Natural history of a systemic right ventricle.

The natural history of a systemic right ventricle after an atrial switch procedure has yet to be fully characterised. We describe the case of the longest surviving patient at our institution who underwent a Mustard Baffle correction for dextro-transposition of great arteries in childhood. Over following decades he was reviewed regularly with deteriorating systemic right ventricle function. At around 50 years of age he developed worsening heart failure on maximal medical therapy. He was subsequently assessed for cardiac transplantation which he underwent successfully at the age of 55 years.

Performance of contemporary surgical risk scores for mitral valve surgery.

BACKGROUND: Risk stratification for mitral valve repair or replacement (MVR) is important in the decision-making for treating several mitral valve disease but is rarely studied. We compared the prognostic utility of EuroSCORE, EuroSCORE II, and Society of Thoracic Surgeons (STS) Score for MVR. METHODS: The three scores were retrospectively calculated for consecutive patients undergoing isolated MVR at Auckland City Hospital during 2005-2012 and their discrimination and calibration for mortality and morbidities assessed. RESULTS: There were 408 patients (mitral valve repair 48.1% and replacement 51.9%) followed-up for 6.0 ± 2.6 years. The operative mortality was 2.5%. Mean EuroSCORE, EuroSCORE II, and STS Score were 7.6%, 3.4%, and 3.5%. C-statistics were 0.844, 0.817, and 0.850 for operative mortality. Hosmer-Lemeshow test p values were 0.076, 0.541, and 0.306, and Brier scores 0.0246, 0.0035, and 0.0075, respectively, for operative mortality. The numerically highest c-statistic for predicting complications include EuroSCORE for return to the operating room (c = 0.673); EuroSCORE II for stroke (c = 0.669) and mediastinitis (c = 0.801); and STS for renal failure (c = 0.828), ventilation >24 hours (c = 0.789), and composite morbidity (c = 0.732). The individual STS complication models for MVR had a numerically higher c-statistic only for stroke (c = 0.737). CONCLUSIONS: All scores discriminated mortality and most morbidities after MVR, although EuroSCORE over-estimated operative mortality. The STS Score was the best overall predictor of mortality and morbidity in the MVR cohort.

Aortic Valve Replacement With or Without Concurrent Coronary Artery Bypass Grafting in Octogenarians: Eight-Year Cohort Study.

BACKGROUND: With the introduction of transcatheter aortic valve implantation (TAVI), there is increasing interest in evaluating outcomes of aortic valve replacement (AVR) with or without (+/-) concurrent coronary artery bypass grafting (CABG) particularly in high-risk patients. We reviewed the characteristics and outcomes of octogenarians undergoing isolated AVR and AVR+CABG. METHODS: All patients 80 years of age or older undergoing AVR+/-CABG at Auckland City Hospital during 2005-2012 were included, and their characteristics and outcomes analysed. RESULTS: There were 93 and 104 octogenarians respectively undergoing isolated AVR and AVR+CABG with mean follow-up of 4.4+/-2.2 years and 4.1+/-2.3 years. Significant differences in baseline and operative characteristics contributed to higher EuroSCORE II (5.9 vs 6.4%, P=0.016) and STS Score (4.9 vs 6.9%, P<0.001) for AVR+CABG patients. They also had a significantly higher rate of 30-day mortality (0.0% vs 6.7%, P=0.015) and prolonged ventilation>24hours (10.7% vs 23.1%, P<0.001), but not composite morbidity (P=0.248) or stroke (P=0.709). Long-term survival was similar at one, three and five years; 94.6%, 82.6% and 73.0% for AVR and 91.3%, 86.1% and 67.6% for AVR+CABG. Independent predictors of 30-day mortality included reduced creatinine clearance and history of myocardial infarction. CONCLUSION: AVR+CABG had significantly higher but acceptable 30-day mortality in octogenarians than AVR. We have identified prognostic factors important in the decision-making of treatment modality, where age alone should not preclude surgery.

Comparing Performance of Risk Scores for Combined Aortic Valve Replacement and Coronary Bypass Grafting Surgery.

BACKGROUND: Aortic valve replacement (AVR) and/or coronary artery bypass grafting (CABG) make up the majority of cardiac surgery with increasing demand as the population ages. Accuracy of risk stratification is important, in predicting adverse outcomes and selecting modality of intervention, but has been rarely studied for the combined AVR+CABG operation. We compared the prognostic utility of EuroSCORE, EuroSCORE II and Society of Thoracic Surgeons' (STS) Score for AVR+CABG. METHODS: All patients (n=450) undergoing AVR+CABG at Auckland City Hospital during 2005-2012 with mean follow-up of 4.7+/-2.5 years were included. The three risk scores were calculated and their discrimination and calibration for mortality and morbidities assessed. RESULTS: Operative mortality was 6.4% (29), and mean scores were EuroSCORE 12.5+/-11.1%, EuroSCORE II 6.6+/-6.1% and STS Score 5.5+/-4.4%. C-statistics were 0.587, 0.669 and 0.699 respectively for operative mortality, Hosmer-Lemeshow test P-values were 0.064, 0.718 and 0.567, and Brier Score 0.716, 0.585 and 0.588. Independent predictors of operative mortality were history of myocardial infarction and impaired renal function. Society of Thoracic Surgeons' score also was the most accurate score for predicting mortality during follow-up (c=0.663), composite morbidity (c=0.627), stroke (c=0.642), prolonged ventilation>24hours (c=0.642), and return to theatre (c=0.612). CONCLUSION: The STS score has the best discriminative ability for mortality and the majority of complications after AVR+CABG, while its calibration was similar to EuroSCORE II and superior to EuroSCORE. It should therefore be used for risk stratification and when considering surgical versus percutaneous intervention in those with concurrent aortic valve and coronary artery disease.

T-tubule disease: Relationship between t-tubule organization and regional contractile performance in human dilated cardiomyopathy.

Evidence from animal models suggest that t-tubule changes may play an important role in the contractile deficit associated with heart failure. However samples are usually taken at random with no regard as to regional variability present in failing hearts which leads to uncertainty in the relationship between contractile performance and possible t-tubule derangement. Regional contraction in human hearts was measured by tagged cine MRI and model fitting. At transplant, failing hearts were biopsy sampled in identified regions and immunocytochemistry was used to label t-tubules and sarcomeric z-lines. Computer image analysis was used to assess 5 different unbiased measures of t-tubule structure/organization. In regions of failing hearts that showed good contractile performance, t-tubule organization was similar to that seen in normal hearts, with worsening structure correlating with the loss of regional contractile performance. Statistical analysis showed that t-tubule direction was most highly correlated with local contractile performance, followed by the amplitude of the sarcomeric peak in the Fourier transform of the t-tubule image. Other area based measures were less well correlated. We conclude that regional contractile performance in failing human hearts is strongly correlated with the local t-tubule organization. Cluster tree analysis with a functional definition of failing contraction strength allowed a pathological definition of 't-tubule disease'. The regional variability in contractile performance and cellular structure is a confounding issue for analysis of samples taken from failing human hearts, although this may be overcome with regional analysis by using tagged cMRI and biopsy mapping.

Next-generation endomyocardial biopsy: the potential of confocal and super-resolution microscopy.

Confocal laser scanning microscopy and super-resolution microscopy provide high-contrast and high-resolution fluorescent imaging, which has great potential to increase the diagnostic yield of endomyocardial biopsy (EMB). EMB is currently the gold standard for identification of cardiac allograft rejection, myocarditis, and infiltrative and storage diseases. However, standard analysis is dominated by low-contrast bright-field light and electron microscopy (EM); this lack of contrast makes quantification of pathological features difficult. For example, assessment of cardiac allograft rejection relies on subjective grading of H&E histology, which may lead to diagnostic variability between pathologists. This issue could be solved by utilising the high contrast provided by fluorescence methods such as confocal to quantitatively assess the degree of lymphocytic infiltrate. For infiltrative diseases such as amyloidosis, the nanometre resolution provided by EM can be diagnostic in identifying disease-causing fibrils. The recent advent of super-resolution imaging, particularly direct stochastic optical reconstruction microscopy (dSTORM), provides high-contrast imaging at resolution approaching that of EM. Moreover, dSTORM utilises conventional fluorescence dyes allowing for the same structures to be routinely imaged at the cellular scale and then at the nanoscale. The key benefit of these technologies is that the high contrast facilitates quantitative digital analysis and thereby provides a means to robustly assess critical pathological features. Ultimately, this technology has the ability to provide greater accuracy and precision to EMB assessment, which could result in better outcomes for patients.

Intra-aortic balloon counterpulsation in contemporary practice - where are we?

The intra-aortic balloon pump (IABP) remains the most widely used form of mechanical circulatory support in current clinical practice. This article will review the current evidence to guide IABP use, focussing on large registry and prospective, randomised data, and seek to establish appropriate roles for the IABP in contemporary practice. Despite a paucity of clinical evidence, the IABP remains a useful clinical tool in selected settings, although its routine, up-front use in relatively unselected MI populations is not supported by data. Although current evidence no longer supports routine use in certain high-risk groups, further studies of appropriately selected high-risk patients may yet demonstrate benefit in patients with moderate-severe degrees of shock.

B-type natriuretic peptide forms within the heart, coronary sinus, and peripheral circulation in humans: evidence for degradation before secretion.

BACKGROUND: The B-type natriuretic peptides (BNP and N-terminal pro-BNP) are secreted by the heart and, in the case of BNP, serve to maintain circulatory homeostasis through renal and vascular actions and oppose many effects of the renin-angiotensin system. Recent evidence suggests that in patients with severe heart failure, circulating immunoreactive BNP is made up mainly of metabolites that may have reduced bioactivity. We hypothesized that BNP may be degraded before it even leaves the heart. METHODS: Peripheral venous plasma plus atrial and ventricular tissue, obtained from explanted hearts at the time of transplantation, were collected from 3 patients with end-stage heart failure. In a separate study, plasma was collected from the coronary sinus and femoral artery of 3 separate patients undergoing cardiac catheterization. Plasma C18 reverse-phase extracts were separated on reverse-phase HPLC, and the collected fractions were subjected to RIAs with highly specific antisera directed to the amino- and carboxy-terminal ends of BNP(1-32). RESULTS: ProBNP, BNP(1-32), and 2 major BNP metabolites were present in atrial and ventricular tissue, where BNP(1-32) represented 45% and 70% of total processed BNP, respectively. Neither BNP(1-32) nor the 2 metabolites were detected in peripheral venous plasma. Nor was BNP(1-32) detected in matching coronary sinus and femoral artery plasma from the 3 patients undergoing cardiac catheterization. CONCLUSIONS: BNP(1-32) is partly degraded within the hearts of patients with end-stage heart failure, and even in patients with relatively well-preserved left ventricular systolic function, only BNP metabolites enter the systemic circulation.

Closure of a broncho-pleural fistula using an atrial septal defect occluder.

Broncho-pleural fistulae (BPF) are recognised as a rare complication following pneumonectomy. We describe a patient, who after failing conservative treatment, underwent closure of a persistent fistula with an atrial septal defect (ASD) occluder. Additionally we review the literature regarding management of BPF and the emerging role of cardiac defect closure devices as a possible treatment option.

Outcome following heart transplantation in New Zealand Maori.

BACKGROUND: Disparities in health care access and outcomes between Maori (M) and Non-Maori (NM) New Zealanders have been reported but little is known about access to and outcomes following heart transplantation (HT). METHODS: A retrospective analysis was performed of M and NM who underwent HT in New Zealand. Demographic, clinical and outcome data were collected. RESULTS: Of 253 patients transplanted, 176 were European, 47 M (19%) and 30 of other ethnicities. M and NM groups were compared. Median age (both 46 years), gender (17% vs 21% female), waiting time (90 vs 76 days) and diagnosis (dilated cardiomyopathy - 62% vs 58%) were similar for both groups. M were heavier (81 vs 71 kg, p<0.0001) and more were blood group A (58% vs 39%). Five year survival was similar (79% vs 78%) but 10 year survival was significantly reduced in M (54% vs 67% p=0.02). CONCLUSION: The proportion of Maori who have undergone heart transplantation in New Zealand compares favourably with their proportion in the New Zealand population. The reasons for the adverse diverging outcomes after five years require further investigation.

Durable ventricular assist devices for patients with advanced heart failure: the New Zealand experience.

AIMS: The prevalence of heart failure in New Zealand is increasing. A small number of select patients with predicted poor short-term survival are candidates for advanced heart failure therapies such as transplantation and durable mechanical circulatory support (MCS). The aim of our study was to introduce left ventricular assist devices (LVADs) to the wider clinicians and highlight their role in managing patients with advanced heart failure in New Zealand. METHOD: A retrospective audit of all ventricular assist device (VAD) recipients from January 2005 to December 2022 was conducted. Data were collated using electronic medical and paper records. The primary outcome was survival to transplantation or successful explant of VAD. RESULTS: Thirty-nine patients received VADs; 32 were male and seven female. Mean age was 45 years (range 10-64 years). Most recipients were NZ European (25), six were Maori, four were Pacific peoples and four were of other ethnicities. The majority of LVADs were implanted for those with dilated cardiomyopathy (67%). At the time of data collection, 24 (62%) had survived to heart transplantation, seven (18%) died while on VAD support, five from right ventricular failure and two from strokes, one patient had their VAD explanted due to recovery and seven (18%) VAD recipients continue on support awaiting transplant. CONCLUSION: This audit has provided an opportunity to inform New Zealand clinicians of our durable MCS programme and the expanding role of VAD support in patients with advanced heart failure. The programme will need to continue to audit and report its practice in order to provide equitable allocation of this very limited resource to a growing population in need.

Impaired calcium handling mechanisms in atrial trabeculae of diabetic patients.

The aim of this study was to investigate cardiomyocyte Ca2+ handling and contractile function in freshly excised human atrial tissue from diabetic and non-diabetic patients undergoing routine surgery. Multicellular trabeculae (283 ± 20 µm in diameter) were dissected from the endocardial surface of freshly obtained right atrial appendage samples from consenting surgical patients. Trabeculae were mounted in a force transducer at optimal length, electrically stimulated to contract, and loaded with fura-2/AM for intracellular Ca2+ measurements. The response to stimulation frequencies encompassing the physiological range was recorded at 37°C. Myofilament Ca2+ sensitivity was assessed from phase plots and high potassium contractures of force against [Ca2+ ]i . Trabeculae from diabetic patients (n = 12) had increased diastolic (resting) [Ca2+ ]i (p = 0.03) and reduced Ca2+ transient amplitude (p = 0.04) when compared to non-diabetic patients (n = 11), with no difference in the Ca2+ transient time course. Diastolic stress was increased (p = 0.008) in trabeculae from diabetic patients, and peak developed stress decreased (p ≤ 0.001), which were not accounted for by reduction in the cardiomyocyte, or contractile protein, content of trabeculae. Trabeculae from diabetic patients also displayed diminished myofilament Ca2+ sensitivity (p = 0.018) compared to non-diabetic patients. Our data provides evidence of impaired calcium handling during excitation-contraction coupling with resulting contractile dysfunction in atrial tissue from patients with type 2 diabetes in comparison to the non-diabetic. This highlights the importance of targeting cardiomyocyte Ca2+ homeostasis in developing more effective treatment options for diabetic heart disease in the future.

Correcting bias in cardiac geometries derived from multimodal images using spatiotemporal mapping.

Cardiovascular imaging studies provide a multitude of structural and functional data to better understand disease mechanisms. While pooling data across studies enables more powerful and broader applications, performing quantitative comparisons across datasets with varying acquisition or analysis methods is problematic due to inherent measurement biases specific to each protocol. We show how dynamic time warping and partial least squares regression can be applied to effectively map between left ventricular geometries derived from different imaging modalities and analysis protocols to account for such differences. To demonstrate this method, paired real-time 3D echocardiography (3DE) and cardiac magnetic resonance (CMR) sequences from 138 subjects were used to construct a mapping function between the two modalities to correct for biases in left ventricular clinical cardiac indices, as well as regional shape. Leave-one-out cross-validation revealed a significant reduction in mean bias, narrower limits of agreement, and higher intraclass correlation coefficients for all functional indices between CMR and 3DE geometries after spatiotemporal mapping. Meanwhile, average root mean squared errors between surface coordinates of 3DE and CMR geometries across the cardiac cycle decreased from 7 ± 1 to 4 ± 1 mm for the total study population. Our generalised method for mapping between time-varying cardiac geometries obtained using different acquisition and analysis protocols enables the pooling of data between modalities and the potential for smaller studies to leverage large population databases for quantitative comparisons.

Right ventricular morphology on catheter angiography: variations and its implications for the diagnosis of arrhythmogenic right ventricular cardiomyopathy.

BACKGROUND: Catheter angiography is one modality used to diagnose right ventricular (RV) structural abnormalities in suspected arrythmogenic right ventricular dysplasia or cardiomyopathy (ARVC) patients. The appearance of the normal RV on angiography is poorly defined. This study aimed to assess RV morphology in a control group to define the range of normal appearances. METHODS: RV angiography was performed in 46 subjects (mean age 59 years; 70% male) undergoing coronary angiography for suspected coronary artery disease. Qualitative assessment for RV dilatation, regional wall motion abnormalities (RWMAs), pattern of trabeculae, and presence of micro-aneurysms was performed. Right ventricular outflow tract (RVOT) diameter was measured. RESULTS: Regional or global RV dilatation was considered to be present in 17 patients, RWMA in 13, an abnormal trabecular pattern in 10, and microaneurysms noted in two. The RVOT diameter ranged from 1.78 to 3.51 cm in right anterior oblique view and 2.33 to 4.38 cm in left anterior oblique view. CONCLUSION: The apparent prevalence of abnormal RV morphology in individuals who have no known RV pathology implies that detection of such is not necessarily of diagnostic significance in suspected ARVC. Significant inter-observer variation limits the usefulness of qualitative assessment; quantitative assessment is preferred therefore.

MITEA: A dataset for machine learning segmentation of the left ventricle in 3D echocardiography using subject-specific labels from cardiac magnetic resonance imaging.

Segmentation of the left ventricle (LV) in echocardiography is an important task for the quantification of volume and mass in heart disease. Continuing advances in echocardiography have extended imaging capabilities into the 3D domain, subsequently overcoming the geometric assumptions associated with conventional 2D acquisitions. Nevertheless, the analysis of 3D echocardiography (3DE) poses several challenges associated with limited spatial resolution, poor contrast-to-noise ratio, complex noise characteristics, and image anisotropy. To develop automated methods for 3DE analysis, a sufficiently large, labeled dataset is typically required. However, ground truth segmentations have historically been difficult to obtain due to the high inter-observer variability associated with manual analysis. We address this lack of expert consensus by registering labels derived from higher-resolution subject-specific cardiac magnetic resonance (CMR) images, producing 536 annotated 3DE images from 143 human subjects (10 of which were excluded). This heterogeneous population consists of healthy controls and patients with cardiac disease, across a range of demographics. To demonstrate the utility of such a dataset, a state-of-the-art, self-configuring deep learning network for semantic segmentation was employed for automated 3DE analysis. Using the proposed dataset for training, the network produced measurement biases of -9 ± 16 ml, -1 ± 10 ml, -2 ± 5 %, and 5 ± 23 g, for end-diastolic volume, end-systolic volume, ejection fraction, and mass, respectively, outperforming an expert human observer in terms of accuracy as well as scan-rescan reproducibility. As part of the Cardiac Atlas Project, we present here a large, publicly available 3DE dataset with ground truth labels that leverage the higher resolution and contrast of CMR, to provide a new benchmark for automated 3DE analysis. Such an approach not only reduces the effect of observer-specific bias present in manual 3DE annotations, but also enables the development of analysis techniques which exhibit better agreement with CMR compared to conventional methods. This represents an important step for enabling more efficient and accurate diagnostic and prognostic information to be obtained from echocardiography.

Mapping system for coregistration of cardiac MRI and ex vivo tissue sampling.

PURPOSE: To design a method suitable for obtaining tissue samples from regions of different function as ascertained by magnetic resonance imaging (MRI). MATERIALS AND METHODS: In vivo MRI was used to create azimuthal projections of the heart from dilated cardiomyopathy transplant patients with the cardiac valves in the center and four concentric rings representing the septum and free wall. Tagged MRI could identify regions of different contractile strength that were then transferred onto the map projection. The resulting tissue sampling map was used to guide dissection of tissue samples from the explanted heart for analysis by electron microscopy (EM) as well as provide samples for subsequent mRNA analysis. Accuracy of the sampling was determined in a sheep heart using 17 fiduciary markers glued to the epicardial surface. RESULTS: Tagged MRI identified areas of "normal" (%S(c) -11), "poor" (%S(c) -4) and "failed" contraction (%S(c) +3). The mapping method we developed enabled straightforward sampling of these regions after surgical excision. EM showed good tissue preservation while the test of accuracy using the fiduciary markers showed a sampling accuracy of 0.3 ± 3.7 mm. This was similar to the resolution of tagged MRI images themselves. CONCLUSION: The methods we have developed can accurately guide tissue sampling for ex vivo tissue analysis.

Systematic Comparison of Left Ventricular Geometry Between 3D-Echocardiography and Cardiac Magnetic Resonance Imaging.

Aims: Left ventricular (LV) volumes estimated using three-dimensional echocardiography (3D-echo) have been reported to be smaller than those measured using cardiac magnetic resonance (CMR) imaging, but the underlying causes are not well-understood. We investigated differences in regional LV anatomy derived from these modalities and related subsequent findings to image characteristics. Methods and Results: Seventy participants (18 patients and 52 healthy participants) were imaged with 3D-echo and CMR (<1 h apart). Three-dimensional left ventricular models were constructed at end-diastole (ED) and end-systole (ES) from both modalities using previously validated software, enabling the fusion of CMR with 3D-echo by rigid registration. Regional differences were evaluated as mean surface distances for each of the 17 American Heart Association segments, and by comparing contours superimposed on images from each modality. In comparison to CMR-derived models, 3D-echo models underestimated LV end-diastolic volume (EDV) by -16 ± 22, -1 ± 25, and -18 ± 24 ml across three independent analysis methods. Average surface distance errors were largest in the basal-anterolateral segment (11-15 mm) and smallest in the mid-inferoseptal segment (6 mm). Larger errors were associated with signal dropout in anterior regions and the appearance of trabeculae at the lateral wall. Conclusions: Fusion of CMR and 3D-echo provides insight into the causes of volume underestimation by 3D-echo. Systematic signal dropout and differences in appearances of trabeculae lead to discrepancies in the delineation of LV geometry at anterior and lateral regions. A better understanding of error sources across modalities may improve correlation of clinical indices between 3D-echo and CMR.

Nanoscale Organisation of Ryanodine Receptors and Junctophilin-2 in the Failing Human Heart.

The disrupted organisation of the ryanodine receptors (RyR) and junctophilin (JPH) is thought to underpin the transverse tubule (t-tubule) remodelling in a failing heart. Here, we assessed the nanoscale organisation of these two key proteins in the failing human heart. Recently, an advanced feature of the t-tubule remodelling identified large flattened t-tubules called t-sheets, that were several microns wide. Previously, we reported that in the failing heart, the dilated t-tubules up to ~1 µm wide had increased collagen, and we hypothesised that the t-sheets would also be associated with collagen deposits. Direct stochastic optical reconstruction microscopy (dSTORM), confocal microscopy, and western blotting were used to evaluate the cellular distribution of excitation-contraction structures in the cardiac myocytes from patients with idiopathic dilated cardiomyopathy (IDCM) compared to myocytes from the non-failing (NF) human heart. The dSTORM imaging of RyR and JPH found no difference in the colocalisation between IDCM and NF myocytes, but there was a higher colocalisation at the t-tubule and sarcolemma compared to the corbular regions. Western blots revealed no change in the JPH expression but did identify a ~50% downregulation of RyR (p = 0.02). The dSTORM imaging revealed a trend for the smaller t-tubular RyR clusters (~24%) and reduced the t-tubular RyR cluster density (~35%) that resulted in a 50% reduction of t-tubular RyR tetramers in the IDCM myocytes (p < 0.01). Confocal microscopy identified the t-sheets in all the IDCM hearts examined and found that they are associated with the reticular collagen fibres within the lumen. However, the size and density of the RyR clusters were similar in the myocyte regions associated with t-sheets and t-tubules. T-tubule remodelling is associated with a reduced RyR expression that may contribute to the reduced excitation-contraction coupling in the failing human heart.