Landmark Evolutions in Time and Indication for Cardiac Resynchronization Therapy: Results from a Multicenter Retrospective Registry

Background: Cardiac resynchronization therapy (CRT) has evolved into an established therapy for patients with chronic heart failure and a wide QRS complex. Data on long-term outcomes over time are scarce and the criteria for implantation remain a subject of investigation. Methods: An international, multicenter, retrospective registry includes 2275 patients who received CRT between 30 November 2000 and 31 December 2019, with a mean follow-up of 3.6 ± 2.7 years. Four time periods were defined, based on landmark trials and guidelines. The combined endpoint was a composite of all-cause mortality, heart transplantation, or left ventricular assist device implantation. Results: The composite endpoint occurred in 656 patients (29.2%). The mean annual implantation rate tripled from 31.5 ± 17.4/year in the first period to 107.4 ± 62.4/year in the last period. In the adjusted Cox regression analysis, the hazard ratio for the composite endpoint was not statistically different between time periods. When compared to sinus rhythm with left bundle branch block (LBBB), a non-LBBB conduction pattern (sinus rhythm: HR 1.51, 95% CI 1.12-2.03; atrial fibrillation: HR 2.08, 95% CI 1.30-3.33) and a QRS duration below 130 ms (HR 1.64, 95% CI 1.29-2.09) were associated with a higher hazard ratio. Conclusions: Despite innovations, an adjusted regression analysis revealed stable overall survival over time, which can at least partially be explained by a shift in patient characteristics.

Long-term outcome after upgrade to cardiac resynchronization therapy: A propensity score-matched analysis

AIM

Cardiac resynchronization therapy (CRT) is a cornerstone in the management of chronic heart failure in patients with a broad or paced QRS. However, data on long-term outcome after upgrade to CRT are scarce.

METHODS AND RESULTS

This international, multicentre retrospective registry included 2275 patients who underwent a de novo or upgrade CRT implantation with a mean follow-up of 3.6 ± 2.7 years. The primary composite endpoint included all-cause mortality, heart transplantation, or ventricular assist device implantation. The secondary endpoint was first heart failure admission. Multivariable Cox regression and propensity score matching (PSM) analyses were performed. Patients who underwent CRT upgrade (n = 605, 26.6%) were less likely female (19.7% vs. 28.8%, p < 0.001), more often had ischeemic cardiomyopathy (49.8% vs. 40.2%, p < 0.001), and had worse renal function (median estimated glomerular filtration rate 50.3 ml/min/1.73 m2 [35.8-69.5] vs. 59.9 ml/min/1.73 m2 [43.0-76.5], p < 0.001). The incidence rate of the composite endpoint was 10.8%/year after CRT upgrade versus 7.1%/year for de novo implantations (p < 0.001). PSM for the primary endpoint resulted in 488 pairs. After propensity score matching, upgrade to CRT was associated with a higher chance to reach the composite endpoint (multivariable hazard ratio [HR] 1.35, 95% confidence interval [CI] 1.08-1.70), for both upgrade from pacemaker (multivariable HR 1.33, 95% CI 1.03-1.70) and implantable cardioverter-defibrillator (ICD) (multivariable HR 1.40, 95% CI 1.01-1.95). PSM for the secondary endpoint resulted in 277 pairs. After PSM, upgrade to CRT was associated with a higher chance for heart failure admission (HR 1.74, 95% CI 1.26-2.41).

CONCLUSION

In this retrospective analysis, the outcome of patients who underwent upgrades to CRT differed significantly from patients who underwent de novo CRT implantation, particularly for upgrades from ICD. Importantly, this difference in outcome does not imply a causal relation between therapy and outcome but rather a difference between two different patient populations.

Mechanical Dyssynchrony Combined with Septal Scarring Reliably Identifies Responders to Cardiac Resynchronization Therapy

Background and aim: The presence of mechanical dyssynchrony on echocardiography is associated with reverse remodelling and decreased mortality after cardiac resynchronization therapy (CRT). Contrarily, myocardial scar reduces the effect of CRT. This study investigated how well a combined assessment of different markers of mechanical dyssynchrony and scarring identifies CRT responders. Methods: In a prospective multicentre study of 170 CRT recipients, septal flash (SF), apical rocking (ApRock), systolic stretch index (SSI), and lateral-to-septal (LW-S) work differences were assessed using echocardiography. Myocardial scarring was quantified using cardiac magnetic resonance imaging (CMR) or excluded based on a coronary angiogram and clinical history. The primary endpoint was a CRT response, defined as a ≥15% reduction in LV end-systolic volume 12 months after implantation. The secondary endpoint was time-to-death. Results: The combined assessment of mechanical dyssynchrony and septal scarring showed AUCs ranging between 0.81 (95%CI: 0.74-0.88) and 0.86 (95%CI: 0.79-0.91) for predicting a CRT response, without significant differences between the markers, but significantly higher than mechanical dyssynchrony alone. QRS morphology, QRS duration, and LV ejection fraction were not superior in their prediction. Predictive power was similar in the subgroups of patients with ischemic cardiomyopathy. The combined assessments significantly predicted all-cause mortality at 44 ± 13 months after CRT with a hazard ratio ranging from 0.28 (95%CI: 0.12-0.67) to 0.20 (95%CI: 0.08-0.49). Conclusions: The combined assessment of mechanical dyssynchrony and septal scarring identified CRT responders with high predictive power. Both visual and quantitative markers were highly feasible and demonstrated similar results. This work demonstrates the value of imaging LV mechanics and scarring in CRT candidates, which can already be achieved in a clinical routine.

Is it feasible to outsource the remote monitoring of implantable cardiac defibrillators in a large tertiary hospital?

AIM

To provide a detailed description of the workflow at our telecardiology centre and to analyse the workload of real-world remote monitoring with the aim to assess the feasibility to outsource this service.

METHODS

A retrospective analysis was conducted on the telecardiology service provided at the University Hospitals of Leuven by extracting patient demographic data, general time usage and detailed information about the type of remote contacts. 10,869 contacts in 948 patients have been included. A 2-week prospective study was conducted on the same service by documenting and monitoring every action performed by specialised nurses when analysing and solving remote monitoring transmissions. 337 contacts in 262 patients were collected during this period.

RESULTS

Both analyses indicated similar numbers of events and interventions. Unplanned transmissions were more challenging and required more interventions than planned transmissions. Relatively little time (retrospective median: 1.83 min; prospective median: 1.56 min, per event) was spent on incoming non-actionable 'normal' transmissions (retrospective: 46%; prospective: 40% of all events). Retrospectively 54% and prospectively 60% of transmissions showed abnormalities and were responsible for most of the time expended. Disease-related issues were the most frequent cause for these 'abnormal' alerts. Contacting patients and physicians were key interventions undertaken. Interaction initiated by patients mainly involved the installation process (42%) and bedside monitoring problems (32%).

CONCLUSION

External data centres could deal with 40% of the transmissions, but the decline in workload would be negligible for the in-hospital remote monitoring team, because very little time is spent dealing with the many 'non-event' transmissions whereas most of the time is spent solving clinical problems. Providing sufficient resources and optimising communication protocols is necessary to aid in managing the workload of the remote monitoring team.

Implications for practiceContacting patients and physicians are key interventions for specialist nurses in remote monitoring centres.Detailed timing confirmed that most time was spent on relevant disease-related clinical problems.Despite dealing with ∼40% of transmissions, outsourcing to external data centres would decrease the workload only by 15-25%.Patient initiated contacts with questions concerning remote monitoring form a high burden and should be countered by scaling the service and creating communication protocols.

Sequential left ventricular electro-mechanical changes in left bundle branch pacing vs right ventricular pacing a two-center study

Background

Left bundle branch pacing (LBBP) has been proved to maintain electrical synchrony better than RVP during mid to long-term follow-up, but little is known about the left ventricular (LV) mechanical changes over time. This study investigates if LBBP causes less sequential electro-mechanical alterations in LV that develop over time, compared with both conventional (CRVP) and leadless (LRVP) RVP.

Methods

Sixty-five patients with pacing indication for bradycardia were prospectively enrolled: Twenty-two were treated with LBBP, 23 with CRVP and 20 with LRVP. QRS duration (QRSd) was measured at baseline and during follow-up. All patients underwent echocardiography at baseline, one week after implantation and at one-year follow-up. LV volumes, ejection fraction (EF) and global longitudinal strain (GLS) were measured. Septal flash (SF), apical rocking and septal longitudinal strain patterns were assessed visually by two experienced readers.

Results

All the patients presented with normal strain pattern and no signs of SF or apical rocking at baseline. 100% of CRVP and 95% of LRVP patients had stage1 or 2 septal deformation patterns at week 1, and the majority (72.3% CRVP and 83.3% LRVP) progressed to stage≥2 at 12 months. On the contrary, over 2/3 of LBBP patients preserved normal strain patterns at week 1, and less than 1/3 had stage-1 pattern, 2 out of whom progressed to stage-2 during follow-up (Figure 1). At week 1 and 12 months, all RVP patients had SF, and most of them also exhibited apical rocking (87%-94.4% in CRVP and 80%-94.4% in LRVP). However, much less septal flash and apical rocking was induced in LBBP patients at week 1 and last follow-up (27.3%-37.5% and 22.7%-25%, P&lt;0.001 vs RVP). Baseline QRSd were similar among three groups. At week 1, the paced QRSd increased least in LBBP compared to CRVP and LRVP and remained as such at 12 months. During one year follow-up, LVEF and LV GLS decreased more in CRVP group compared to LBBP (both P&lt;0.05) (Figure 2).

Conclusion

LBBP causes less sequential changes in LV deformation patterns, septal flash and apical rocking, compared to CRVP and LRVP. With this, LBBP appears to preserve LV function better than RVP. CRVP and LRVP did not differ in electro-mechanical changes or LV remodeling.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research Foundation Flanders (FWO) project grant

Reintroducing dyssynchrony significantly increases myocardial stiffness at mitral valve closure

Background

Cardiac shear wave elastography (SWE) allows for the non-invasive assessment of myocardial stiffness via the detection of shear waves. Shear waves are mechanical waves that travel through the heart after for example mitral valve closure (MVC). The propagation speed of these waves is directly dependent on myocardial stiffness, where a higher shear wave speed correlates with a higher stiffness. However, the effect of a left bundle branch block (LBBB) and a dyssynchronous contraction pattern on shear wave speed is currently unknown.

Purpose

To investigate the effect of a dyssynchronous contraction pattern caused by LBBB on shear wave speed.

Methods

We included 29 non-ischemic heart failure patients with an LBBB (68±15y; 52% males) and 9 age-matched healthy volunteers (68±4y; 55% males) as controls. All LBBB patients were implanted with a CRT device and dyssynchrony was reintroduced by turning biventricular (BiV) pacing off to allow native ventricular conduction. Echocardiographic images were taken during BiV pacing on and BiV pacing off, with a conventional ultrasound machine and an experimental high frame rate ultrasound scanner. Shear waves were visualized in M-modes of the septum, colour coded for tissue acceleration. The slope of the shear waves in the M-mode represents their propagation speed. Further, longitudinal strain at MVC and the time difference between onset of septal contraction and MVC were measured (negative time values indicate that MVC occurs before onset of septal contraction).

Results

There was no significant difference in shear wave speed between healthy controls and LBBB patients during BiV pacing on (4.5±1.1 m/s vs 4.9±1.2 m/s; p=0.365; Figure A). However, shear wave speed was significantly higher in LBBB patients during BiV pacing off compared to healthy controls (4.5±1.1 m/s vs 5.6±1.1 m/s; p=0.041; Figure A). Turning BiV pacing off lead to a significant increase in shear wave speed in LBBB patients (4.9±1.2 m/s vs 5.6±1.1 m/s; p=0.003; Figure A), indicating that the reintroduction of LBBB increases septal myocardial stiffness. MVC occurred significantly later after the onset of septal contraction during BiV pacing off (−9±57 ms vs 40±26 ms; p=0.001) and strain values at MVC were more negative (−0.3±0.6% vs −2.0±1.5%; p&lt;0.001). Therefore we hypothesize that during BiV pacing off, the septal wall was further into the contraction phase at the time of MVC, leading to an increased myocardial stiffness, and thus increased shear wave speed (Figure B). Our interpretation was further strengthened by a strong correlation between the change in shear wave speed and the change in septal longitudinal strain at MVC when BiV pacing is turned off (r=0.81; p&lt;0.001; Figure C).

Conclusion

Reintroducing dyssynchrony in LBBB patients significantly increases shear wave speed at MVC. Our results suggest that the earlier contraction of the septum during dyssynchrony is an explanation for the higher septal stiffness at MVC.

Funding Acknowledgement

Type of funding sources: None.

Cardiac shear wave elastography can detect the presence of a septal scar in patients with LBBB

Background

In patients with heart failure and a left bundle branch block (LBBB), cardiac resynchronization therapy (CRT) is an established treatment. However, the rate of non-response to this costly therapy remains high. So far, CRT has proven to be less effective in patients with a septal scar. Detection of a septal scar before CRT implantation could therefore help to improve response rate to CRT. The gold standard to detect septal scarring, LGE MRI, is quite costly and not suited or available for all patients. Cardiac shear wave elastography (SWE) may be an alternative. It allows for the non-invasive assessment of myocardial stiffness based on the detection of shear waves, after for example mitral valve closure (MVC). SWE has shown to be capable to detect myocardial scar, however this has never been demonstrated in the presence of LBBB.

Purpose

To determine whether SWE is able to detect the presence of a septal scar in patients with LBBB.

Methods

To investigate this, 39 CRT patients with a LBBB were included with ischemic (n=10; age: 73±6 y; 70% males) or non-ischemic (n=29; 68±14 y; 52% males) cardiomyopathy and 9 age-matched healthy volunteers (68±4 y; 55% males) served as controls. In order to obtain native ventricular conduction biventricular (BiV) pacing was turned off. All ischemic patients had septal scar only, proven by MRI or scintigraphy. For SWE, left ventricular parasternal long-axis views were acquired with an experimental high frame rate ultrasound scanner (frame rate: 932±32 fps). Shear waves were visualized in M-modes of the septum, colour coded for tissue acceleration. The slope of the shear waves in the M-mode represents their propagation speed (Figure 1A).

Results

Patients characteristics and echocardiographic parameters are shown in Table 1. Shear wave speed after MVC was significantly higher in LBBB patients with and without a septal scar compared to healthy controls (7.8±1.2 m/s vs 4.5±1.1 m/s; p&lt;0.001; 5.6±1.1 m/s vs 4.5±1.1 m/s; p=0.041; Figure 1B), indicating that the presence of LBBB increases myocardial stiffness. However, more importantly, shear wave speed was significantly higher in LBBB patients with a septal scar compared to LBBB patients without a septal scar (7.8±1.2 m/s vs 5.6±1.1 m/s; p&lt;0.001; Figure 1B). This implies that the presence of a septal scar increases shear wave speed even more than LBBB alone. A ROC-curve analysis further showed that SWE is capable of distinguishing scarred from non-scarred septum in LBBB patients (AUC: 0.92; p&lt;0.001; Figure 1C). A cut-off of 7.1 m/s could identify LBBB patients with a septal scar with a sensitivity of 80% and specificity of 93%.

Conclusion

Septal scarring results in a significant increase in myocardial stiffness, so that it reaches a clear pathological range. SWE seems therefore capable of detecting the presence of a septal scar in LBBB patients and could potentially be used as a novel approach for the assessment of septal scarring in CRT candidates.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research foundation Flanders (FWO)

Why does CRT work better in women?

Introduction

It has been recently postulated that cardiac resynchronization therapy (CRT) might have a higher efficacy in women, with a greater reverse cardiac remodeling in this population. The reasons for these differences are not yet completely understood. We aimed to detect sex differences in the degree of ventricular asynchrony (VA) and mitral regurgitation (MR) in patients undergoing CRT implantation.

Methods

We analyzed baseline characteristics of a prospective international clinical trial that compared CRT response rate in a HF population with a comparable distribution of men and women (BIOWOMEN). A total of 408 patients were analyzed. The degree of mitral regurgitation and intra and inter-ventricular asynchrony was assessed by independent echocardiographers in a core lab. Inter-ventricular asynchrony was defined as an interventricular mechanical delay greater than 40ms and intra-ventricular asynchrony as differences greater than 50ms among regional pre-ejection periods. Multivariable logistic regression was performed using commercial data analysis software.

Results

As expected, ventricular asynchrony was dependent on QRS duration and the presence of LBBB (p&lt;0.01). Baseline QRS duration was significantly shorter in women than men (155.85±19.0 in women vs 160.4±21.6, p=0.02). However, for a similar QRS duration, there were no differences in asynchrony parameters between the two groups (p=0.43; Figure 1). Female sex was associated with a significantly higher proportion of mitral regurgitation for a given QRS duration, which was independent of the etiology (p=0.05).

Conclusions

In our analysis, for a given QRS duration there was not a higher degree of asynchrony in women with HF. However, female sex was associated with a significantly higher proportion of mitral regurgitation for a given QRS duration irrespective of baseline HF etiology. Further investigations are needed to establish a possible link between these findings and better CRT outcomes in women.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): BIOTRONIK SE & Co. KG

Left bundle branch pacing preserves ventricular mechanical synchrony better than right ventricular pacing-a two-center study

Funding Acknowledgements

Type of funding sources: None.

Background

Left bundle branch pacing (LBBP) has emerged as a novel pacing method. We sought to evaluate left ventricular (LV) mechanical synchrony under permanent LBBP and compare it with conventional and leadless right ventricular pacing (CRVP, LRVP).

Methods

Sixty-four patients with pacing indication for bradycardia were prospectively enrolled. Twenty-two patients received LBBP in the basal ventricular septum. Twenty-three patients received CRVP and 19 LRVP. All patients underwent echocardiography before and after device implantation. Myocardial work was estimated by pressure-strain analysis. Regional work in the septum (SEP) and lateral wall (LW) was calculated as the average from the respective basal and mid-ventricular segments in the apical four-chamber and three-chamber view. The absolute difference between work in LW and SEP (LW-S-work difference) was used as a measure of asymmetry in workload.

Results

Baseline characteristics were similar among the three groups. The electrocardiogram during LBBP showed a right bundle branch block pattern; during CRVP and LRVP a left bundle branch block pattern. The paced QRS duration was 114.27±9.9 ms in the LBBP group, significantly shorter than that in the CRVP and LRVP groups (153.9±25.26 ms and 159.1±13.99ms, respectively, both p&lt;0.001). The SEP work decreased in all groups during ventricular pacing (all P&lt;0.05), while the LW work remained similar. The paced LW-S work difference and work difference change between pacing on and off were more significant in the CRVP (1012.9±566.0mmHg*%) and LRVP group (1066.1±472.6mmHg*%) than the LBBP group (260.5±239.8mmHg*%, both P&lt;0.001). In addition, LW-S work difference during ventricular pacing and work difference change between pacing and baseline were comparable in CRVP and LRVP group.

Conclusion

LBBP causes less LV dyssynchrony than CRVP and LRVP as it preserves a more physiologic conduction pattern. CRVP and LRVP did not differ in this respect. Further studies need to prove that LBBP has advantages over RVP with regards to preservation of LV synchrony and contractility.

Dyssynchrony significantly increases myocardial stiffness at mitral valve closure

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): FWO: Fonds Wetenschappelijk Onderzoek (fund for Scientific Research Flanders)

Background

Recently, shear wave elastography (SWE) has emerged as a promising, non-invasive technique to determine myocardial tissue stiffness. SWE is based on the detection of shear waves, for example induced by mitral valve closure (MVC), that propagate through the myocardium. The propagation speed of these shear waves is directly dependent on myocardial stiffness. However, the effect of a dyssynchronous contraction pattern – as it occurs in left bundle branch block (LBBB) – on shear wave speed is currently unknown.

Purpose

To investigate the effect of the dyssynchronous contraction pattern caused by LBBB on shear wave speed.

Methods

We included 25 non-ischemic heart failure patients with LBBB (age: 68 ± 15y; 52% males), all implanted with a CRT device. Dyssynchrony was reintroduced by turning biventricular (BiV) pacing off to allow native ventricular conduction. Echocardiographic images were taken during BiV pacing on and BiV pacing off, both with a conventional ultrasound machine and an experimental high frame rate ultrasound scanner (frame rate: 932 ± 32 fps). For SWE, left ventricular parasternal long-axis views were acquired. Shear waves were visualized in M-modes of the septum, colour coded for tissue acceleration. The slope of the shear waves in the M-mode represents their propagation speed. Speckle tracking of the four-chamber apical view was used to asses longitudinal strain of the mid-septal segment. To further investigate how dyssynchrony affects shear wave speed, the following time points were measured: onset of QRS, MVC and onset of septal contraction.

Results

Acutely switching BiV pacing on and off did not significantly affect left ventricular ejection fraction, nor end-diastolic or end-systolic volumes (all p &gt; 0.05). Shear wave speed was significantly higher during BiV pacing off compared to BiV pacing on (5.6 ± 1.2 m/s vs 4.9 ± 1.3 m/s; p = 0.003; figure A). Furthermore, the onset of septal contraction was significantly earlier during BiV off (11 ± 15 ms vs 105 ± 57 ms; p &lt; 0.0001). As a result, during BiV pacing off, the septal wall was further into the contraction phase at the time of MVC, leading to an increased myocardial stiffness, and thus increased shear wave speed (figure B). Our interpretation that increased shear wave speed could be attributed to an earlier onset of contraction of the septum was further strengthened by a strong correlation between the change in shear wave speed and the change in septal longitudinal strain at MVC when BiV pacing is turned off (r = 0.83; p &lt; 0.001; figure C).

Conclusion

A dyssynchronous contraction caused by LBBB significantly increases shear wave propagation speed at MVC. This could be attributed to the early-systolic contraction of the septum during dyssynchrony. These results indicate that changes in contraction pattern caused by LBBB significantly influence myocardial stiffness at MVC. Abstract Figure.

Can cardiac shear wave elastography detect the presence of septal scar in patients with left bundle branch block?

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): FWO: Fonds Wetenschappelijk Onderzoek (fund for scientific research Flanders)

Background

Cardiac resynchronization therapy (CRT) is an established treatment for heart failure patients with left bundle branch block (LBBB). Regardless, CRT has proven to be less effective in patients with ischemic cardiomyopathy, in particular when the septum is affected. The detection of septal scar prior to CRT implantation could therefore help to improve response rate. However, magnetic resonance imaging (MRI), the gold standard to assess myocardial scar, cannot be used in every patient due to already implanted devices or impaired renal function. Cardiac shear wave elastography (SWE) allows for the non-invasive assessment of myocardial stiffness via the detection of shear waves, for example induced by mitral valve closure (MVC), that travel through the myocardium. Shear wave speed is directly related to tissue stiffness. Recently, SWE has shown to be capable to detect myocardial scar, however this has never been demonstrated in the presence of LBBB.

Purpose

To evaluate whether SWE is able to detect the presence of septal scar in patients with LBBB.

Methods

We included 34 heart failure patients with LBBB (age: 69 ± 13 y; 56% males) and with ischemic (n = 9) or non-ischemic (n = 25) cardiomyopathy and 9 age-matched healthy volunteers (age: 68 ± 4 y; 66% males) as controls. In order to obtain native ventricular conduction biventricular (BiV) pacing was turned off. All ischemic patients had septal scar only, proven by MRI or scintigraphy. For SWE, left ventricular parasternal long-axis views were acquired with an experimental high frame rate ultrasound scanner (frame rate: 932 ± 32 fps). Shear waves were visualized in M-modes of the septum, colour coded for tissue acceleration. The slope of the shear waves in the M-mode represents their propagation speed (Figure A).

Results

Patient characteristics including echocardiographic parameters are shown in Table 1. Shear wave speed after MVC was significantly higher in patients with LBBB with or without septal scar compared to healthy controls (7.9 ± 1.2 m/s vs 4.5 ± 1.1 m/s; p = 0.044; 5.6 ± 1.2 m/s vs 4.5 ± 1.1 m/s: p &lt; 0.001; figure B). This implies that the presence of LBBB alone increases myocardial stiffness. Most importantly, however, shear wave speed was significantly higher in LBBB patients with a septal scar compared to LBBB patients without a septal scar (7.9 ± 1.2 m/s vs 5.6 ± 1.2 m/s; p &lt; 0.001; figure B), indicating that the presence of scar increases myocardial stiffness even more than LBBB alone.

Conclusions

LBBB causes a mild but significant increase in shear wave propagation speed in non-ischemic patients compared to controls. The presence of septal scarring leads to an additional and more significant increase. This indicates that SWE is capable of detecting stiffer scarred myocardium even in the presence of LBBB. Therefore, SWE could potentially be used as a novel method to detect septal scarring in LBBB patients before CRT implantation. Abstract Figure.  Abstract Figure.

Cardiac shear wave elastography can distinguish healthy and scarred myocardium in patients with conduction delays

Background

Cardiac resynchronization therapy (CRT) is an established therapy for patients suffering from heart failure and left bundle branch block (LBBB) conduction delays. Despite its proven beneficial effects, CRT is associated with a high percentage of non-response. Since CRT has shown to be less effective in patients with ischemic cardiomyopathy, determining the presence of myocardial scar before implantation could help to improve the response-rate. However, the gold standard to assess myocardial scar, magnetic resonance imaging (MRI), cannot be used in every patient, due to already implanted devices and/or reduced renal function. Recently introduced shear wave elastography (SWE) allows the non-invasive assessment of myocardial stiffness. Natural shear waves are excited by mitral valve closure (MVC) and travel through the heart with a speed directly related to tissue stiffness. SWE has previously been proven to be able to detect myocardial scar, however this has never been shown in the presence LBBB.

Purpose

The aim of this study was to evaluate the capability of SWE as a novel method to determine myocardial scar in patients with conduction delays.

Methods

We included 24 heart failure patients (age: 68±10; 50% males) with ischemic (n=8) and non-ischemic (n=16) cardiomyopathy. The CRT device was set to AAI mode in order to obtain native ventricular conduction. For patients with ischemic cardiomyopathy, the presence and location of scar was determined by MRI or scintigraphy. All ischemic patients had septal scar only. For SWE, left ventricular parasternal long-axis views were acquired with an experimental high frame rate ultrasound scanner (average frame rate: ±1200 Hz). Shear waves were visualized in M-modes of the septum, colour coded for tissue acceleration. The slope of the shear waves in the M-mode represents their propagation speed (Figure A).

Results

There was no significant difference between the ischemic and non-ischemic patients in QRS width after CRT (149±31 ms vs 144±26 ms), systolic blood pressure blood pressure (135±11 mmHg vs 135±23 mmHg), diastolic blood pressure (74±9 mmHg vs 70±11 mmHg) and heart rate (58±4 bpm vs 63±9 bpm) (all p&gt;0.05). Ejection fraction (33±8% vs 45±10%), end-diastolic volume (196±34 ml vs 129±64 ml) and global longitudinal strain (−9.8±3.1% vs −14.1±4.1%) differed significantly between the groups (all p&lt;0.05). Shear wave speed after MVC was significantly higher in patients with septal scar compared to non-ischemic patients (8.2±1.9 m/s vs 5.5±1.2 m/s; p&lt;0.01) (Figure B).

Conclusion

In the presence of scar, we found markedly elevated shear wave propagation speed compared to non-ischemic patients. These results indicate that SWE is able to identify scarred myocardium even in patients with LBBB. We therefore believe that SWE could be a novel easy and non-invasive method to evaluate septal myocardial scarring in patients before CRT implantation.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): FWO - Research Foundation Flanders

Heart failure related to adult congenital heart disease: prevalence, outcome and risk factors

Aims

Information on the prevalence, outcome and factors associated with heart failure in patients with adult congenital heart disease (CHD) (ACHD‐HF) is lacking. We aimed at assessing the prevalence and outcome of ACHD‐HF, the variables associated with ACHD‐HF, and the differences between major anatomical/pathophysiological ACHD subgroups.

Methods and results

We included 3905 patients (age 35.4 ± 13.2 years) under active follow‐up in our institution (last visit >2010). Outcome of ACHD‐HF cases was compared with sex‐ and age‐matched cases. Univariable and multivariable binary logistic regression with ACHD‐HF diagnosis as a dependent variable was performed. Overall prevalence of ACHD‐HF was 6.4% (mean age 49.5 ± 16.7 years), but was higher in patients with cyanotic CHD (41%), Fontan circulation (30%), and a systemic right ventricle (25%). All‐cause mortality was higher in ACHD‐HF cases when compared with controls (mortality rate ratio 4.67 (2.36–9.27); P = 0.0001). In multivariable logistic regression analysis, age at latest follow‐up [per 10 years; odds ratio (OR) 1.52; 95% confidence interval (CI) 1.31–1.77], infective endocarditis (OR 4.11; 95%CI 1.80–9.38), history of atrial arrhythmia (OR 3.52; 95%CI 2.17–5.74), pacemaker implantation (OR 2.66; 95% CI 1.50–4.72), end‐organ dysfunction (OR 2.41; 95% CI 1.03–5.63), New York Heart Association class (OR 9.28; 95% CI 6.04–14.25), heart rate (per 10 bpm; OR 1.27; 95% CI 1.08–1.50), ventricular dysfunction (OR 3.62; 95% CI 2.54–5.17), and pulmonary hypertension severity (OR 1.66; 95% CI 1.21–2.30) were independently related to the presence of ACHD‐HF. Some variables (age, atrial arrhythmia, pacemaker, New York Heart Association, and ventricular dysfunction) were related to ACHD‐HF in all anatomical/physiological subgroups, whereas others were not.

Conclusions

ACHD‐HF is prevalent especially in complex CHD and is associated with poor prognosis. Our data provide insight in the factors related to ACHD‐HF including differences between specific anatomical and physiological subgroups.

Transcriptome analysis of two structurally related flavonoids; Apigenin and Chrysin revealed hypocholesterolemic and ketogenic effects in mouse embryonic fibroblasts

There is no known single therapeutic drug for treating hypercholesterolemia that comes with negligible systemic side effects. In the current study, using next generation RNA sequencing approach in mouse embryonic fibroblasts we discovered that two structurally related flavonoid compounds. Apigenin and Chrysin exhibited moderate blocking ability of multiple transcripts that regulate rate limiting enzymes in the cholesterol biosynthesis pathway. The observed decrease in cholesterol biosynthesis pathway correlated well with an increase in transcripts involved in generation and trafficking of ketone bodies as evident by the upregulation of Bdh1 and Slc16a6 transcripts. The hypocholesterolemic potential of Apigenin and Chrysin at higher concentrations along with their ability to generate ketogenic substrate especially during embryonic stage is useful or detrimental for embryonic health is not clear and still debatable. Our study will serve as a steppingstone to further the investigation in whole animal studies and also in translating this knowledge to human studies.

Re-implantation after extraction of a cardiac implantable electronic device

Background: With increasing cardiovascular implantable electronic device (CIED) implantations, growing number of extractions of leads and devices are noted, mainly for complications such as infection and lead dysfunction. The optimal timing for re-implantation remains uncertain. We  investigated the time to eventual re-implantation of CIEDs in the University Hospitals Leuven, Belgium.Methods: All consecutive patients, referred for extraction between January 2005 and December 2016, were analysed for the timing of eventual re-implantation.Results: Two-hundred and forty-three patients were included. Mean follow-up was 77 ± 37 months. Global re-implantation rate was 89.3%: 100% for lead dysfunctions versus 80.7% following infections. Median time to re-implantation (TTR) was 0 [0-111] days and 8.5 [0-3025] days, respectively (p < .001). Globally 0 [0-3025] days. Re-implantation was performed in 83.2% of pacemaker patients, compared to 95.8% of defibrillator patients (p < .001). Median TTR was 4 [0-3025] days and 0 [0-345] days, respectively (p < .001). In AV-block related pacemaker indications, 90% were re-implanted, compared to 78% for symptomatic indications (p = .09). Median TTR was 2 [0-3025] and 6 [0-2047] days, respectively (p = .02). Re-implantation was performed in 96.7% of defibrillator patients with a secondary prevention indication, compared to 94.7% with primary prevention indication (p = .59). Median TTR was 0 [0-164] and 0 [0-345] days, respectively (p = .472).Conclusions: Ten percent of CIEDs is not re-implanted after extraction. CIEDs are re-implanted more often and earlier after extraction for lead dysfunction than after extraction for infectious reasons. Pacemakers are re-implanted less and later than defibrillators. Re-implantation is performed faster in stronger clinical CIED indications.

Imaging predictors of response to cardiac resynchronization therapy: left ventricular work asymmetry by echocardiography and septal viability by cardiac magnetic resonance

AIMS

Left ventricular (LV) failure in left bundle branch block is caused by loss of septal function and compensatory hyperfunction of the LV lateral wall (LW) which stimulates adverse remodelling. This study investigates if septal and LW function measured as myocardial work, alone and combined with assessment of septal viability, identifies responders to cardiac resynchronization therapy (CRT).

METHODS AND RESULTS

In a prospective multicentre study of 200 CRT recipients, myocardial work was measured by pressure-strain analysis and viability by cardiac magnetic resonance (CMR) imaging (n = 125). CRT response was defined as ≥15% reduction in LV end-systolic volume after 6 months. Before CRT, septal work was markedly lower than LW work (P < 0.0001), and the difference was largest in CRT responders (P < 0.001). Work difference between septum and LW predicted CRT response with area under the curve (AUC) 0.77 (95% CI: 0.70-0.84) and was feasible in 98% of patients. In patients undergoing CMR, combining work difference and septal viability significantly increased AUC to 0.88 (95% CI: 0.81-0.95). This was superior to the predictive power of QRS morphology, QRS duration and the echocardiographic parameters septal flash, apical rocking, and systolic stretch index. Accuracy was similar for the subgroup of patients with QRS 120-150 ms as for the entire study group. Both work difference alone and work difference combined with septal viability predicted long-term survival without heart transplantation with hazard ratio 0.36 (95% CI: 0.18-0.74) and 0.21 (95% CI: 0.072-0.61), respectively.

CONCLUSION

Assessment of myocardial work and septal viability identified CRT responders with high accuracy.

160 Echocardiographic assessment of CRT candidates. Does additional scar evaluation by MRI improve prediction of response?

Background

Myocardial scar presence and extent, has a considerable influence on response to cardiac resynchronization therapy (CRT). Apical rocking (ApRock) and septal flash (SF) are associated with favourable outcome after CRT. Little is known however to which extent visual assessment of mechanical dyssynchrony by ApRock, SF and scar predicts CRT response. We therefore investigated, if additional scar assessment by cardiac magnetic resonance imaging (MRI) adds to the predictive value of the visual evaluation of echocardiographic images in CRT candidates.

Methods

A total of 201 unselected patients referred for CRT, who fulfil the contemporary guidelines for CRT implantation, were enrolled in this prospective multicentre study. Two experienced observers visually assessed echocardiographic images before CRT implantation, focussing on the presence of ApRock, SF and location and extent of scar segments of the left ventricle (LV), resulting in a CRT response prediction (i.e. Integrative Prediction). A third observer provided a consensus reading in case of disagreement. All observers were blinded to all patient information other than the ischaemic aetiology of heart failure. Independent from that, segmental myocardial scar burden was objectified by late gadolinium enhancement (LGE) cardiac MRI (LGE &gt; 50%). CRT response was defined as ≥15% reduction in LV end-systolic volume on echocardiography, one year after device implantation.

Results

Overall, 69 (34%) patients had an ischaemic aetiology of heart failure. Before CRT, ApRock and SF were present in 129 (64%) and 136 (68%) patients, respectively. ApRock and SF alone predicted CRT response with an area under the curve (AUC) of 0.85 (95% CI: 0.79-0.91) and 0.84 (95% CI: 0.77-0.91) (Figure A), while the echocardiographic Integrative Prediction had an AUC of 0.90 (95% CI: 0.84-0.95), with a sensitivity of 93% and a specificity of 87% for the prediction of CRT response (Figure B) (p &lt; 0.05 vs. ApRock and SF alone). When combining information on ApRock, SF and the number of scarred segments on MRI in a statistical model, the AUC was comparable to the echocardiographic Integrative Prediction [0.90 (95% CI: 0.84-0.96)] as was sensitivity and specificity (91% and 83%, respectively, p = N.S. vs. Integrative Prediction) (Figure C).

Conclusions

An integrative visual assessment of LV function has an excellent predictive value for CRT response. Our data show, that the echocardiographic estimation of scar burden is sufficiently accurate and cannot be further improved by an additional MRI scar assessment.

Abstract 160 Figure.

Increased Cardiac Uptake of Ketone Bodies and Free Fatty Acids in Human Heart Failure and Hypertrophic Left Ventricular Remodeling

BACKGROUND

Deranged energy metabolism contributes to the pathophysiology of heart failure (HF). Recent studies showed diminished free fatty acid (FFA) oxidation in experimental HF models with a shift towards oxidation of ketone bodies. However, conflicting clinical data on FFA metabolism and limited knowledge on ketone body metabolism in human HF mandate additional metabolic profiling studies. We, therefore, investigated cardiac uptake of FFAs and ketone bodies (β-hydroxybutyrate and acetoacetate) in patients with HF with reduced ejection fraction (HFrEF) or with aortic stenosis (AS)-induced left ventricular hypertrophy. We hypothesized that FFA oxidation is impaired in HFrEF and in AS and results in decreased concentrations of free carnitine, the necessary carrier for mitochondrial entry of activated FFAs, and in accumulation of metabolic intermediates.

METHODS AND RESULTS

We collected arterial and coronary sinus blood samples in patients with HFrEF (n=15), in AS patients with preserved systolic function (n=15), and in control patients (n=15). Plasma concentration gradients across the heart show significantly greater uptake of ketone bodies in patients with HFrEF than in controls. Patients with AS show significantly increased uptake of β-hydroxybutyrate and FFAs. Free carnitine concentration and concentration gradients of intermediates of FFA oxidation were comparable between groups.

CONCLUSIONS

In conclusion, our results show significantly increased cardiac uptake of ketone bodies in patients with stable HFrEF and AS and increased uptake of FFAs in AS compared with control patients. The lack of myocardial release of acyl-carnitine species or change in free carnitine uptake suggests no impairment of FFA oxidation.

Monocentric experience of leadless pacing with focus on challenging cases for conventional pacemaker

AIM

Leadless cardiac pacemaker has been developed to reduce complications related to cardiac pacing and is considered as an alternative to conventional pacemaker although safety and efficacy data in clinical practice are limited. The purpose of this study was to investigate the safety and efficacy profile of Micra Transcatheter Pacing System (TPS) used in daily clinical activity with a focus on challenging cases for conventional pacing.

METHODS

A total of 66 patients (46 men, 79.1 ± 9.7 years) having a Class I or II indication for ventricular pacing underwent a Micra TPS implant procedure. All patients were enrolled in a prospective registry. Follow-up visits were scheduled at discharge and after 1, 3, 6 and 12 months.

RESULTS

Primary indication for pacing was third degree atrioventricular block (30.3%), sinus node dysfunction (21.2%) or permanent atrial fibrillation with bradycardia (45.5%). The device was successfully implanted in 65 patients (98.5%). During follow-up of 10.4 ± 6.1 months (range 1-23 months), electrical measurements remained stable. Mean pacing capture threshold, pacing impedance and R-wave sensing were respectively 0.57 ± 0.32 V, 580 ± 103 Ohms, 10.62 ± 4.36 mV at the last follow-up. One major (loss of function) and three minor adverse events occurred. Pericardial effusion, dislodgement, device related infection or pacemaker syndrome were not observed. Micra TPS implantation was straightforward for patients with congenital or acquired cardiac and/or vascular abnormalities, previous tricuspid surgery and after heart transplantation.

CONCLUSION

Our experience confirms that implantation of Micra is safe and efficient in a real world population including patients who present a challenging condition for conventional pacing.

Impairment of adipose tissue development by hypoxia is not mediated by plasminogen activator inhibitor-1

Hypoxia in rodents and humans is associated with a reduction of body fat on the one hand, and with enhanced expression of plasminogen activator inhibitor-1 (PAI-1), the main inhibitor of the fibrinolytic system, on the other hand. It was the objective of this study to investigate whether impairment of adipose tissue development by hypoxia may be mediated by PAI-1. Five week old male wild-type (WT) C57Bl/6 mice were fed a standard (SFD) or high fat (HFD) diet and kept under normoxic or hypoxic (10% O2) conditions. In addition, PAI-1 deficient mice and WT littermates were kept on HFD under normoxia or hypoxia. In vitro, the effect of hypoxia (2% O2) was investigated on differentiation of 3T3-L1 cells into adipocytes. Hypoxia induced a significant reduction of weight gain in WT mice on either SFD or HFD, accompanied by lower weights of subcutaneous (SC) and gonadal (GON) fat. Under hypoxic conditions, adipocytes in the adipose tissues were significantly smaller, whereas blood vessel size and density were larger. Serum PAI-1 levels were enhanced in hypoxic mice on SFD but not on HFD, and overall did not correlate with the observed changes in adipose tissue composition. Furthermore, the effects of hypoxia on adipose tissue in mice on HFD were not affected by deficiency of PAI-1. The inhibiting effect of hypoxia on in vitro preadipocyte differentiation was not mediated by PAI-1 activity. In conclusion, impairment of in vivo adipose tissue development and in vitro differentiation of preadipocytes by hypoxia is not mediated by PAI-1.

Effect of Heart Rate and Use of Beta Blockers on Mortality After Heart Transplantation

Heart transplantation (HT) recipients may have tachycardia secondary to cardiac denervation. As higher heart rate predicts worse outcomes in cardiovascular disease, we hypothesized that tachycardia and nonuse of β blockers are associated with increased mortality after HT. All patients who underwent HT at our institution from 1987 to 2010 were included. The association of heart rate 3 months after HT and β-blocker use during follow-up to mortality was assessed using Kaplan-Meier and multivariate Cox proportional hazards regression analyses adjusting for clinically relevant baseline variables. From 1987 to 2010, there were 493 HT. After excluding 29 who died within 3 months and 3 with follow-up <3 months, 461 HT recipients (50 ± 2 years; 20% women) were included. Over a follow-up of 12 ± 7 years, selected important univariate predictors of post-HT mortality were older age, male gender, higher body mass index, ischemic cardiomyopathy, longer post-HT intensive care unit stay, and hospitalization and at 3 months, increased mean pulmonary artery pressure, right atrial pressure and pulmonary capillary occlusion pressure, higher heart rate, and nonuse of β blockers during follow-up. In multivariate analysis, older ager, longer hospitalization, higher mean pulmonary artery pressure, higher heart rate at 3 months (hazard ratio 1.02 per beat, 95% confidence interval 1.008 to 1.035, p = 0.02) and nonuse of β blockers (hazard ratio 1.43, 95% confidence interval 1.002 to 2.031, p <0.05) were associated with mortality. In conclusion, in a large single-center cohort of HT recipients, higher heart rate and nonuse of β blockers were independently associated with higher mortality.

Changes in Implantation Patterns and Therapy Rates of Implantable Cardioverter Defibrillators over Time in Ischemic and Dilated Cardiomyopathy Patients

BACKGROUND

Clinical guidelines on implantable cardioverter defibrillator (ICD) therapy changed significantly in the last decades with potential inherent effects on therapy efficacy. We aimed to study therapy rates in time and the association between therapies and mortality.

METHODS

All patients receiving an ICD, primary and secondary prevention, were included in a single-center retrospective registry. Information on first appropriate and inappropriate therapies was documented. Dates of implant were divided in P1: 1996-2001, P2: 2002-2008, and P3: 2009-2014.

RESULTS

A total of 727 patients, 84.9% male-66.4% ischemic cardiomyopathy (ICM)-56% primary prevention-mean follow-up 5.2 ± 4.1 years, were included. There was a shift from secondary to primary prevention indications, from ischemic to non-ICM, and from single chamber to cardiac resynchronization therapy defibrillator devices. The annual 1- and 3-year appropriate shock (AS) rate declined from 29.4% and 15.1% in P1, over 13.3% and 9.2% in P2 to 7.8% and 5.7% in P3 (log-rank P < 0.001), while inappropriate shock (IAS) rates remained unchanged (log-rank P = 0.635). After multivariate regression analysis a higher age at implant, lower left ventricular ejection fraction, history of stroke, diabetes mellitus, intake of loop diuretics or digitalis, higher creatinine, and longer QTc were independent predictors of mortality.

CONCLUSION

These changes in clinical practice with a shift to primary prevention and rise in non-ICM implants caused a significant decrease in AS incidence, while IAS remained stable. Receiving AS or IAS was not an independent predictor of mortality in our real-life cohort.

How to choose between a pacemaker or defibrillator for resynchronization therapy?

OBJECTIVE

The choice between a resynchronization pacemaker (CRT-P) or defibrillator (CRT-D) is still a matter of debate. We hypothesised that when selecting patients based on co-morbidities and age as proposed by the ESC-guidelines, there would be no long-term survival benefit of CRT-D compared to CRT-P.

METHODS

We performed a retrospective analysis of patients who received a CRT device at the University Hospitals Leuven between 2001 and 2007. For the analysis of the association between predictors and outcome, uni- and multivariate Cox regression analyses were performed. We present data from three multivariate models.

RESULTS

A total of 144 CRT devices were implanted (CRT-D n=98, CRT-P n=46). Patients who received a CRT-P were older and had a higher prevalence of co-morbidities. Patients who received a CRT-D had a significant lower mortality. When applying incremental multivariate analysis using 1st variables with a P < 0.05 in univariate analysis, 2nd variables with a P < 0.10 and 3rd adding on top all the baseline variables that were significantly different between the two groups, the significance of a possible survival benefit for CRT-D over CRT-P disappeared: risk model 1, hazard ratio 2.21 (P = 0.008), risk model 2, HR 1.81 (P = 0.069), and risk model 3, HR 1.85 (P = 0.091). The use of amiodarone and the presence of COPD or renal insufficiency remained associated with a significant, higher mortality risk, while the use of beta blockers was protective in all three models.

CONCLUSION

The choice of a CRT-D seemed a predictor of improved survival in simple but not in more complex multivariable analyses. The fact that the survival benefit strongly depended on the number of co-variables suggests that it is at most marginal.

On the role of placental growth factor in murine adipogenesis

The potential role of placental growth factor (PlGF) in early stages of adipogenesis was investigated in vivo using a murine model of obesity, as well as in vitro using cultured preadipocytes. PlGF-deficient (PlGF-/-) and wild-type (WT) mice, kept on high fat diet (HFD) for 3 weeks, had comparable body weight and weight of subcutaneous (SC) and gonadal (GON) adipose tissues. Blood vessel size and blood vessel density, normalized to adipocyte number, were not significantly different in SC and GON adipose tissues of both genotypes. Differentiation of embryonic fibroblasts derived from WT or PlGF-/- mice into mature adipocytes was comparable. Furthermore, addition of recombinant PlGF, of the PlGF neutralizing MAb PL5D11D4 or of the anti-Flk-1 MAb DC101 to cultured 3T3-F442A preadipocytes did not significantly affect their differentiation into mature adipocytes. Ex vivo blood vessel outgrowth following seeding of adipose tissue-derived microvessel fragments in 3D-collagen gels was not affected by PlGF deficiency. Thus, in murine model systems, PlGF does not seem to play an important role in early adipogenesis.

Impaired adipose tissue development in mice with inactivation of placental growth factor function

Placental growth factor (PlGF)-deficient (PlGF-/-) and wild-type mice were kept on a standard-fat or high-fat diet for 15 weeks. With the standard-fat diet, the body weights of PlGF-/- and wild-type mice were comparable, whereas the combined weight of subcutaneous and gonadal adipose tissues was lower in PlGF-/- mice (P = 0.02). With the high-fat diet, PlGF-/- mice had a lower body weight (P < 0.05) and less total subcutaneous plus gonadal adipose tissue (P < 0.0001). Blood vessel size was lower in gonadal adipose tissue of PlGF-/- mice with both the standard-fat and high-fat diet (P < 0.05). Blood vessel density, normalized to adipocyte number, was significantly lower in subcutaneous adipose tissue of PlGF-/- mice fed the high-fat diet (P < 0.01). De novo adipose tissue development in nude mice injected with 3T3-F442A preadipocytes was reduced (P < 0.005) by administration of a PlGF-neutralizing antibody. Bone marrow transplantation from wild-type or PlGF-/- mice to wild-type or PlGF-/- recipient mice revealed significantly lower blood vessel density in PlGF-/- recipient mice without an effect on adipose tissue growth. Thus, in murine models of diet-induced obesity, inactivation of PlGF impairs adipose tissue development, at least in part as a result of reduced angiogenesis.

Overexpression of tissue inhibitor of matrix metalloproteinases-1 (TIMP-1) in mice does not affect adipogenesis or adipose tissue development

In order to evaluate a potential functional role of tissue inhibitor of matrix metalloproteinases-1 (TIMP-1) in development of obesity, we studied the effect of overexpression of human TIMP-1 (hTIMP-1) in C57Bl/6J mice in vivo and in 3T3-F442A preadipocytes in vitro. Stable long-term overexpression of hTIMP-1 in mice was achieved by adenoviral gene transfer, yielding plasma levels exceeding 250 ng/ml at eight weeks after injection. Mice overexpressing hTIMP-1 and kept on a high fat diet for 14 weeks had body weights, adipose tissue weights, and adipocyte diameters that were somewhat, but not significantly, lower than those of control mice. Similar observations were made after overexpression of hTIMP-1 in mice with lipectomy of the subcutaneous adipose tissue, kept on a high fat diet for 20 weeks. In both in vivo models, blood vessels in the adipose tissues were significantly smaller after hTIMP-1 gene transfer than in control mice. Overexpression of hTIMP-1 in 3T3-F442A preadipocytes had no effect on their subsequent differentiation into mature adipocytes. Thus, overexpression of hTIMP-1 in mice had no significant effect on ongoing adipogenesis or adipose tissue development, although the blood vessel size in adipose tissues was reduced.

Expression of aggrecan(ases) during murine preadipocyte differentiation and adipose tissue development

The expression and potential functional role of aggrecan in adipogenesis and adipose tissue development was investigated in murine models of obesity. Aggrecan, as well as the two aggrecanases ADAMTS-4 and ADAMTS-5 (A Disintegrin And Metalloproteinase with Thrombospondin motif) mRNAs, are expressed in subcutaneous (SC) and gonadal (GON) adipose tissues of mice. Their presence was confirmed by western blotting using adipose tissue extracts. In mice with nutritionally induced obesity (high fat diet) as well as in lean controls, aggrecan mRNA expression was downregulated whereas ADAMTS-4 and ADAMTS-5 were upregulated with time. In mice with genetically determined obesity (ob/ob), ADAMTS-5 mRNA was upregulated in both SC and GON adipose tissues, as compared to wild-type (WT) mice (p<0.001). Enhanced aggrecanase expression levels in these tissues were associated with significantly elevated levels of G1-NITEGE, a degradation product of aggrecan. Thus, aggrecan levels were high at the early stages of adipose tissue development in mice, whereas its production decreased and its degradation increased during development of obesity. A functional role of aggrecan in promoting early stages of adipogenesis is supported by the findings that it stimulated the in vitro differentiation of 3T3-F442A preadipocytes and the de novo in vivo accumulation of fat in Matrigel plaques injected into WT mice. Proteoglycans in the extracellular matrix of adipose tissue, such as aggrecan, may contribute to the regulation of lipid uptake and obesity in mice.

Impairment of adipose tissue development by hypoxia is not mediated by plasminogen activator inhibitor-1

Hypoxia in rodents and humans is associated with a reduction of body fat on the one hand, and with enhanced expression of plasminogen activator inhibitor-1 (PAI-1), the main inhibitor of the fibrinolytic system, on the other hand. It was the objective of this study to investigate whether impairment of adipose tissue development by hypoxia may be mediated by PAI-1. Five week old male wild-type (WT) C57Bl/6 mice were fed a standard (SFD) or high fat (HFD) diet and kept under normoxic or hypoxic (10% O(2)) conditions. In addition, PAI-1 deficient mice and WT littermates were kept on HFD under normoxia or hypoxia. In vitro, the effect of hypoxia (2% O(2)) was investigated on differentiation of 3T3-L1 cells into adipocytes. Hypoxia induced a significant reduction of weight gain in WT mice on either SFD or HFD, accompanied by lower weights of subcutaneous (SC) and gonadal (GON) fat. Under hypoxic conditions, adipocytes in the adipose tissues were significantly smaller, whereas blood vessel size and density were larger. Serum PAI-1 levels were enhanced in hypoxic mice on SFD but not on HFD, and overall did not correlate with the observed changes in adipose tissue composition. Furthermore, the effects of hypoxia on adipose tissue in mice on HFD were not affected by deficiency of PAI-1. The inhibiting effect of hypoxia on in vitro preadipocyte differentiation was not mediated by PAI-1 activity. In conclusion, impairment of in vivo adipose tissue development and in vitro differentiation of preadipocytes by hypoxia is not mediated by PAI-1.

Modulation of angiogenesis during adipose tissue development in murine models of obesity

Development of vasculature and mRNA expression of 17 pro- or antiangiogenic factors were studied during adipose tissue development in nutritionally induced or genetically determined murine obesity models. Subcutaneous (SC) and gonadal (GON) fat pads were harvested from male C57Bl/6 mice kept on standard chow [standard fat diet (SFD)] or on high-fat diet for 0-15 wk and from male ob/ob mice kept on SFD. Ob/ob mice and C57Bl/6 mice on high-fat diet had significantly larger SC and GON fat pads, accompanied by significantly higher blood content, increased total blood vessel volume, and higher number of proliferating cells. mRNA and protein levels of angiopoietin (Ang)-1 were down-regulated, whereas those of thrombospondin-1 were up-regulated in developing adipose tissue in both obesity models. Ang-1 mRNA levels correlated negatively with adipose tissue weight in the early phase of nutritionally induced obesity as well as in genetically determined obesity. Placental growth factor and Ang-2 expression were increased in SC adipose tissue of ob/ob mice, and thrombospondin-2 was increased in both their SC and GON fat pads. mRNA levels of vascular endothelial growth factor (VEGF)-A isoforms VEGF-B, VEGF-C, VEGF receptor-1, -2, and -3, and neuropilin-1 were not markedly modulated by obesity. This modulation of angiogenic factors during development of adipose tissue supports their important functional role in obesity.