Left ventricular dimensions and mass measurement from 3D echocardiography: are we there yet?

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Health Research Council (HRC) of New Zealand and National Heart Foundation (NHF) of New Zealand

Introduction—Echocardiographic measures of left ventricular (LV) structure and size, including LV wall thickness and LV end-diastolic dimension (LVID), provide important information in the assessment of patients with heart disease. For example, LV mass is a predictor of outcome for patients with hypertension and LVID is a predictor of cardiac resynchronisation response in patients with heart failure. Advances in 3D echocardiography (3DE) have enabled full-volume acquisitions, which overcome geometric assumptions present in conventional 2D echocardiography (2DE), providing a more accurate representation of cardiac geometry. Although numerous validation studies have been performed for 3DE-derived LV volumes, comparisons of LV dimension by 3DE against established methods are limited.

Purpose—We sought to compare routine LV dimension measurements between 3DE and 2DE, with validation using cardiac magnetic resonance (CMR) imaging.

Methods—Transthoracic echocardiography (2D and 3D) and cine CMR imaging were performed in 62 prospectively recruited participants (47 healthy controls, 9 patients with LVH, 6 patients with aortic regurgitation), <1 h apart. 2DE LV dimension measurements (interventricular septum [IVS], posterior wall thickness [PWT], and LVID) were taken at end-diastole from the parasternal long axis, and mass was calculated using the linear method based on ASE/EACVI guidelines. For 3DE, 3D geometric models of the LV were constructed by interactively fitting surfaces to the endocardium and epicardium using previously validated software, from which corresponding LV dimension measurements and mass were extracted. Measurements were obtained from CMR by a similar 3D geometric modelling process.

Results—Differences (mean ± SD) in LV dimension measurements between the three modalities and intraclass correlation coefficients (ICC) are presented in Table I. When compared with CMR, 3DE exhibited higher agreement in terms of LVID and mass than 2DE, but lower agreement in wall thickness measurements. Statistically significant differences were found between 2DE and 3DE for PWT, LVID, and mass, as well as 2DE and CMR for LVID and mass (where P < 0.01 for a paired sample t­-test, marked with an asterisk). Meanwhile, there were no statistically significant differences between 3DE and CMR for IVS, PWT, LVID, or mass.

Conclusions—Our results demonstrate that 3DE is superior to 2DE in terms of LVID and mass quantification, exhibiting good agreement with CMR. 3DE exhibited moderate and poor agreement for IVS and PWT, respectively, with both 2DE and CMR, likely due to the lower spatial resolution of 3DE. Further advances in 3DE image quality and analysis tools are therefore needed to improve accuracy of wall thickness measurements. Since 2DE imaging plane and probe positioning can result in oblique measurement and underestimation of LVID, the assessment of LVID and mass by 3DE is likely to lead to more accurate diagnostic and prognostic outcomes. Abstract Table 1

Derivation of in vivo pressure-volume loops for post-heart transplant patients using real-time 3D echocardiography and left ventricular catheterisation

Background

Image-based methods that combine catheterisation with non-concurrent cardiac magnetic resonance (CMR) imaging data and echocardiography (echo) is gaining more interest than the conductance catheter method to derive pressure-volume loops (PVLs) due to improved accuracy and accessibility of LV volume quantification [1–3]. However, accurate temporal registration between LV pressure and volume is not well developed.

Purpose

We propose a framework for temporally registering invasive LV and aortic pressures (LVP and AOP) acquired during left heart catheterisation with real time 3D echocardiography (RT3DE) to generate in vivo PVLs in a group of heart transplant (HTx) recipients.

Methods

25 orthotopic HTx recipients (mean age: 54±8 years and 7 female) indicated for routine coronary assessment were recruited for invasive hemodynamic measurement and RT3DE imaging. A fluid-filled pigtail catheter was used to measure LVP and AOP with simultaneous electrocardiogram (ECG) over several (9–15) heartbeats. Within an hour of catheterisation, single-beat transthoracic RT3DE of the LV was performed from the apical window in a left lateral decubitus position. Imaging parameters were optimized for each patient to maximize the temporal resolution (between 15–41 imaging frames per cycle). We developed a piecewise linear temporal scaling method based on cardiac events (end-diastole (ED), end of isovolumic contraction (eIVC), end-systole (ES), end of isovolumic relaxation (eIVR), and diastasis (DS)) of RT3DE and haemodynamic measurement to resample the LVP at the RT3DE imaging frames between the cardiac events to construct PVLs (Fig. 1a). Geometric LV models were manually fitted at ED and ES, followed by automatic tracking across intermediary frames to estimate LV volume over the entire cardiac cycle (Fig. 1b). The temporally aligned pressure values were further averaged to find the beat-averaged LV PVL (Fig. 1c).

Results

Based on the number of cardiac cycles selected for haemodynamic analysis, multiple in vivo PVLs were constructed for each patient. A beat-averaged PVL was also computed for each patient (Fig.1d). With the exception of one case, the beat-averaged PVLs exhibited classically representative shape with distinct isovolumic contraction and isovolumic relaxation phases. The individual diastolic PVRs for all patients are shown in Fig.1e, with beat-to-beat variation observed in most patients. For some cases, the variation manifested as an offset in LVP, whereas changes in the diastolic PVR slope were observed in other cases.

Conclusion

Temporal alignment scheme based on cardiac events allowed accurate derivation of patient-specific in vivo PVLs from catheterization and RT3DE measurements. Application to heart transplant recipients revealed beat-to-beat variation of haemodynamic state. Further analysis of the diastolic PVRs will allow quantification of chamber stiffness for HTx recipients.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Health Research Council of New Zealand Patient-specific PVLs

Renal denervation in male rats with heart failure improves ventricular sympathetic nerve innervation and function

Heart failure is characterized by the loss of sympathetic innervation to the ventricles, contributing to impaired cardiac function and arrhythmogenesis. We hypothesized that renal denervation (RDx) would reverse this loss. Male Wistar rats underwent myocardial infarction (MI) or sham surgery and progressed into heart failure for 4 wk before receiving bilateral RDx or sham RDx. After additional 3 wk, left ventricular (LV) function was assessed, and ventricular sympathetic nerve fiber density was determined via histology. Post-MI heart failure rats displayed significant reductions in ventricular sympathetic innervation and tissue norepinephrine content (nerve fiber density in the LV of MI+sham RDx hearts was 0.31 ± 0.05% vs. 1.00 ± 0.10% in sham MI+sham RDx group, P < 0.05), and RDx significantly increased ventricular sympathetic innervation (0.76 ± 0.14%, P < 0.05) and tissue norepinephrine content. MI was associated with an increase in fibrosis of the noninfarcted ventricular myocardium, which was attenuated by RDx. RDx improved LV ejection fraction and end-systolic and -diastolic areas when compared with pre-RDx levels. This is the first study to show an interaction between renal nerve activity and cardiac sympathetic nerve innervation in heart failure. Our findings show denervating the renal nerves improves cardiac sympathetic innervation and function in the post-MI failing heart.

Ankle arthrodesis. A comparison of an arthroscopic and an open method of treatment

An arthroscopic technique and an open technique with malleolar ostectomy for ankle arthrodesis is described and compared. Internal fixation with compression across the tibiotalar joint was utilized for both methods using either 6.5-mm or 7.0-mm cannulated screws. The indications, advantages, results, and complications of these two fusion techniques in 33 patients are reported. Arthroscopic arthrodesis was performed in 17 patients, using open arthrotomy and malleolar ostectomy in 16. The mean time to arthrodesis for patients having the procedure arthroscopically was 8.7 weeks (range, six to 14 weeks), compared to 14.5 weeks in the open arthrotomy group (range, eight to 26 weeks; p less than 0.004). Despite differences in patient selection for each of the two groups, it was concluded that disabling ankle arthritis for certain patients may be more appropriately managed with arthroscopic arthrodesis than by arthrotomy and malleolar ostectomy, utilizing similar methods of internal fixation.

Complications associated with limb salvage for extremity sarcomas and their management

A retrospective clinical review of 100 consecutive patients with extremity sarcomas managed by limb salvage operations was performed to evaluate local tumor control and morbidity. The mean follow-up period was 45.1 months. Overall survival was 86%. There were local recurrences in 3% of patients, and 26 complications in 22 patients. Wound necrosis was the most frequent complication. Failure of allogeneic bone graft operations occurred in 25 patients. Most of the complications were salvageable without loss of limb. Limb salvage is an acceptable surgical treatment of extremity sarcomas based on adequate local control and minimal morbidity.

The use of large allografts for tumor reconstruction and salvage of the failed total hip arthroplasty

Large bone defects have become a more common orthopedic problem in recent year. This is due to the increased enthusiasm for limb salvage surgery as a technique to manage patients with primary bone tumors and for patients who have had multiple joint arthroplasties with subsequent bone loss. One technique that has proven successful for this difficult problem is the use of fresh frozen allografts to reconstruct these skeletal defects. From January 1981 until January 1987, 60 large fragment fresh frozen allografts were used for skeletal reconstruction. These grafts were divided into three basic groups: intercalary, 15; osteoarticular, 16; and allograft-prosthetic composite, 29. The diagnoses included 43 bone tumors, 16 failed total hip arthroplasties, and one traumatic bone loss. The average patient age was 39.7 years and had an average follow-up period of 24 months. The average length of allograft was 12.4 cm. Using the Enneking Functional Evaluation System, the final functional analysis revealed excellent or good results in 86% of the patients and fair or poor results in 14% of the patients. Roentgenological union at the allograft-host bone junction was achieved in 90% of the patients in a mean time of 5.8 months after surgery. An additional three patients obtained union after autogeneic bone grafting. At the time of follow-up evaluation, 92.3% of the patients were free of tumor; they had no local recurrences. The use of fresh frozen allografts represents an acceptable alternative for the reconstruction of large skeletal defects. One can expect good or excellent function for the majority of patients. The best functional results were obtained with the intercalary allografts and the allograft-prosthetic composites.