Cost-Effectiveness of Cardiovascular Magnetic Resonance for Rejection Surveillance After Cardiac Transplantation in the Australian Health Care System.

BACKGROUND: Heart transplantation is an effective treatment for end-stage congestive heart failure, however, achieving the right balance of immunosuppression to maintain graft function while minimising adverse effects is challenging. Serial endomyocardial biopsies (EMBs) are currently the standard for rejection surveillance, despite being invasive. Replacing EMB-based surveillance with cardiac magnetic resonance (CMR)-based surveillance for acute cardiac allograft rejection has shown feasibility. This study aimed to assess the cost-effectiveness of CMR-based surveillance in the first year after heart transplantation. METHOD: A prospective clinical trial was conducted with 40 orthotopic heart transplant (OHT) recipients. Participants were randomly allocated into two surveillance groups: EMB-based, and CMR-based. The trial included economic evaluations, comparing the frequency and cost of surveillance modalities in relation to quality-adjusted life years (QALYs) within the first year post-transplantation. Sensitivity analysis encompassed modelled data from observed EMB and CMR arms, integrating two hypothetical models of expedited CMR-based surveillance. RESULTS: In the CMR cohort, 238 CMR scans and 15 EMBs were conducted, versus (vs) 235 EMBs in the EMB group. CMR surveillance yielded comparable rejection rates (CMR 74 vs EMB 94 events, p=0.10) and did not increase hospitalisation risk (CMR 32 vs EMB 46 events, p=0.031). It significantly reduced the necessity for invasive EMBs by 94%, lowered costs by an average of AUD$32,878.61, and enhanced cumulative QALY by 0.588 compared with EMB. Sensitivity analysis showed that increased surveillance with expedited CMR Models 1 and 2 were more cost-effective than EMB (all p<0.01), with CMR Model 1 achieving the greatest cost savings (AUD$34,091.12±AUD$23,271.86 less) and utility increase (+0.62±1.49 QALYs, p=0.011), signifying an optimal cost-utility ratio. Model 2 showed comparable utility to the base CMR model (p=0.900) while offering the benefit of heightened surveillance frequency during periods of elevated rejection risk. CONCLUSIONS: CMR-based rejection surveillance in orthotopic heart transplant recipients provides a cost-effective alternative to EMB-based surveillance. Furthermore, it reduces the need for invasive procedures, without increased risk of rejection or hospitalisation for patients, and can be incorporated economically for expedited surveillance. These findings have important implications for improving patient care and optimising resource allocation in post-transplant management.

Intra-cardiac motion detection catheter for the early identification of acute pericardial tamponade during invasive cardiac procedures.

Objectives: To develop and test an intra-cardiac catheter fitted with accelerometers to detect acute pericardial effusion prior to the onset of hemodynamic compromise. Background: Early detection of an evolving pericardial effusion is critical in ensuring timely treatment. We hypothesized that the reduction in movement of the lateral heart border present in developing pericardial effusions could be quantified by positioning an accelerometer in a lateral cardiac structure. Methods: A "motion detection" catheter was created by implanting a 3-axis accelerometer at the distal tip of a cardiac catheter. The pericardial space of 5 adult sheep was percutaneously accessed, and pericardial tamponade was created by infusion of normal saline. The motion detection catheter was positioned in the coronary sinus. Intracardiac echocardiography was used to confirm successful creation of pericardial effusion and hemodynamic parameters were collected. Results: Statistically significant reduction in acceleration from baseline was detected after infusion of only 40 ml of normal saline (p < 0.05, ANOVA). In comparison, clinically significant change in systolic blood pressure (defined as >10% drop in baseline systolic blood pressure) occurred after infusion of 80 ml of normal saline (107 ± 22 mmHg vs. 90 ± 12 mmHg p = 0.97, ANOVA), and statistically significant change was recorded only after infusion of 200 ml (107 ± 22 mmHg vs. 64 ± 5 mmHg, p < 0.05, ANOVA). Conclusions: An intra-cardiac motion detection catheter is highly sensitive in identifying acute cardiac tamponade prior to clinically and statistically significant changes in systolic blood pressure, allowing for early detection and treatment of this potentially life-threatening complication of all modern percutaneous cardiac interventions.

Metabolic Sequelae of Everolimus Treatment After Cardiac Transplant: A Hypothesis-Generating Study.

BACKGROUND: Although modern immunosuppressants improve survival post-transplant, they are associated with long-term metabolic complications, such as post-transplant diabetes mellitus (PTDM). Calcineurin inhibitor-sparing regimens using everolimus attenuate some complications such as left ventricular hypertrophy. However, the metabolic effects of everolimus following transplant are less clear. METHODS: Post-hoc analysis to compare PTDM and other metabolic outcomes in participants of a randomised open-label clinical trial of low-dose everolimus and tacrolimus versus standard-dose tacrolimus in heart transplant recipients (RADTAC1 study). RESULTS: There were 39 participants in the trial; mean follow-up was 6.4±1.5 years. There was a high rate of pre-existing diabetes (26%) and newly diagnosed PTDM (36%) during follow-up. Half the patients who developed PTDM in the everolimus-tacrolimus group (n=4/8) ceased diabetes medications during follow-up, which was not observed in patients on standard tacrolimus (n=0/6). In the first 12 months there was a higher use of non-insulin treatment for diabetes in the everolimus-tacrolimus group compared to the standard tacrolimus group. CONCLUSIONS: This study suggests that treatment with everolimus may be associated with improved glycaemic control of PTDM relative to treatment with standard doses of calcineurin inhibitor. These findings should be further studied in prospective randomised trials.

Atrial cardiomyopathy: Current and future imaging methods for assessment of atrial structure and function.

Changes in atrial size and function have historically been considered a surrogate marker of ventricular dysfunction. However, it is now recognized that atrial cardiomyopathy (ACM) may also occur as a primary myocardial disorder. Emerging evidence that ACM is a major risk factor for atrial fibrillation, heart failure, and thromboembolic stroke, has highlighted the significance of this disorder and the need for better assessment of atrial metrics in clinical practice. Key barriers in this regard include a lack of standardized criteria or hierarchy for the diagnosis of ACM and lack of consensus for the most accurate phenotyping methods. In this article we review existing literature on ACM, with a focus on current and future non-invasive imaging methods for detecting abnormalities of atrial structure and function. We discuss the relative advantages and disadvantages of transthoracic echocardiography and cardiac magnetic resonance imaging for assessing a range of parameters, including atrial size and contractile function, strain, tissue characteristics, and epicardial adipose tissue. We will also present the potential application of novel imaging methods such as sphericity index and four- or five-dimensional flow.

Cardiovascular Magnetic Resonance for Rejection Surveillance After Cardiac Transplantation.

BACKGROUND: Endomyocardial biopsy (EMB) is the gold standard method for surveillance of acute cardiac allograft rejection (ACAR) despite its invasive nature. Cardiovascular magnetic resonance (CMR)-based myocardial tissue characterization allows detection of myocarditis. The feasibility of CMR-based surveillance for ACAR-induced myocarditis in the first year after heart transplantation is currently undescribed. METHODS: CMR-based multiparametric mapping was initially assessed in a prospective cross-sectional fashion to establish agreement between CMR- and EMB-based ACAR and to determine CMR cutoff values between rejection grades. A prospective randomized noninferiority pilot study was then undertaken in adult orthotopic heart transplant recipients who were randomized at 4 weeks after orthotopic heart transplantation to either CMR- or EMB-based rejection surveillance. Clinical end points were assessed at 52 weeks. RESULTS: Four hundred one CMR studies and 354 EMB procedures were performed in 106 participants. Forty heart transplant recipients were randomized. CMR-based multiparametric assessment was highly reproducible and reliable at detecting ACAR (area under the curve, 0.92; sensitivity, 93%; specificity, 92%; negative predictive value, 99%) with greater specificity and negative predictive value than either T1 or T2 parametric CMR mapping alone. High-grade rejection occurred in similar numbers of patients in each randomized group (CMR, n=7; EMB, n=8; P=0.74). Despite similarities in immunosuppression requirements, kidney function, and mortality between groups, the rates of hospitalization (9 of 20 [45%] versus 18 of 20 [90%]; odds ratio, 0.091; P=0.006) and infection (7 of 20 [35%] versus 14 of 20 [70%]; odds ratio, 0.192; P=0,019) were lower in the CMR group. On 15 occasions (6%), patients who were randomized to the CMR arm underwent EMB for clarification or logistic reasons, representing a 94% reduction in the requirement for EMB-based surveillance. CONCLUSIONS: A noninvasive CMR-based surveillance strategy for ACAR in the first year after orthotopic heart transplantation is feasible compared with EMB-based surveillance. REGISTRATION: HREC/13/SVH/66 and HREC/17/SVH/80. AUSTRALIAN NEW ZEALAND CLINICAL TRIALS REGISTRY: ACTRN12618000672257.

Pluripotent stem cell-derived mesenchymal stromal cells improve cardiac function and vascularity after myocardial infarction.

BACKGROUND AIMS: Mesenchymal stromal cells (MSCs) have been shown to improve cardiac function after injury and are the subject of ongoing clinical trials. In this study, the authors tested the cardiac regenerative potential of an induced pluripotent stem cell-derived MSC (iPSC-MSC) population (Cymerus MSCs) in a rat model of myocardial ischemia-reperfusion (I/R). Furthermore, the authors compared this efficacy with bone marrow-derived MSCs (BM-MSCs), which are the predominant cell type in clinical trials. METHODS: Four days after myocardial I/R injury, rats were randomly assigned to (i) a Cymerus MSC group (n = 15), (ii) a BM-MSC group (n = 15) or (iii) a vehicle control group (n = 14). For cell-treated animals, a total of 5 × 106 cells were injected at three sites within the infarcted left ventricular (LV) wall. RESULTS: One month after cell transplantation, Cymerus MSCs improved LV function (assessed by echocardiography) compared with vehicle and BM-MSCs. Interestingly, Cymerus MSCs enhanced angiogenesis without sustained engraftment or significant impact on infarct scar size. Suggesting safety, Cymerus MSCs had no effect on inducible tachycardia or the ventricular scar heterogeneity that provides a substrate for cardiac re-entrant circuits. CONCLUSIONS: The authors here demonstrate that intra-myocardial administration of iPSC-MSCs (Cymerus MSCs) provide better therapeutic effects compared with conventional BM-MSCs in a rodent model of myocardial I/R. Because of its manufacturing scalability, iPSC-MSC therapy offers an exciting opportunity for an "off-the-shelf" stem cell therapy for cardiac repair.

Everolimus for the Prevention of Calcineurin-Inhibitor-Induced Left Ventricular Hypertrophy After Heart Transplantation (RADTAC Study).

OBJECTIVES: This study aimed to determine the safety and efficacy of combined low-dose everolimus and low-dose tacrolimus compared with standard-dose tacrolimus in attenuating left ventricular hypertrophy (LVH) after orthotopic heart transplantation (OHT). BACKGROUND: Calcineurin inhibitors (CNIs) such as tactrolimus are important in preventing cardiac allograft rejection and reducing mortality after OHT. However CNIs are causatively linked to the development of LVH, and are associated with nephrotoxicity and vasculopathy. CNI-sparing agents such as everolimus have been hypothesized to inhibit adverse effects of CNIs. METHODS: In this prospective, randomized, open-label study, OHT recipients were randomized at 12 weeks after OHT to a combination of low-dose everolimus and tacrolimus (the RADTAC group) or standard-dose tacrolimus (the TAC group), with both groups coadministered mycophenolate and prednisolone. The primary endpoint was LVH indexed as the change in left ventricular mass (ΔLVM) by cardiovascular magnetic resonance (CMR) imaging from 12 to 52 weeks. Secondary endpoints included CMR-based myocardial performance, T1 fibrosis mapping, blood pressure, and renal function. Safety endpoints included episodes of allograft rejection and infection. RESULTS: Forty stable OHT recipients were randomized. Recipients in the RADTAC group had significantly lower tacrolimus levels compared with the TAC group (6.5 ± 3.5 µg/l vs. 8.6 ± 2.8 µg/l; p = 0.02). The mean everolimus level in the RADTAC group was 4.2 ± 1.7 µg/l. A significant reduction in LVM was observed in the RADTAC group compared with an increase in LVM in the TAC group (ΔLVM = -13.0 ± 16.8 g vs. 2.1 ± 8.4 g; p < 0.001). Significant differences were also noted in secondary endpoints measuring function and fibrosis (Δ circumferential strain = -2.9 ± 2.8 vs. 2.1 ± 2.3; p < 0.001; ΔT1 mapping values = -32.7 ± 51.3 ms vs. 26.3 ± 90.4 ms; p = 0.003). No significant differences were observed in blood pressure (Δ mean arterial pressure = 4.2 ± 18.8 mm Hg vs. 2.8 ± 13.8 mm Hg; p = 0.77), renal function (Δ creatinine = 3.1 ± 19.9 µmol/l vs. 9 ± 21.8 µmol/l; p = 0.31), frequency of rejection episodes (p = 0.69), or frequency of infections (p = 0.67) between groups. CONCLUSIONS: The combination of low-dose everolimus and tacrolimus compared with standard-dose tacrolimus safely attenuates LVH in the first year after cardiac transplantation with an observed reduction in CMR-measured fibrosis and an improvement in myocardial strain.

Platelet-derived growth factor-AB improves scar mechanics and vascularity after myocardial infarction.

Therapies that target scar formation after myocardial infarction (MI) could prevent ensuing heart failure or death from ventricular arrhythmias. We have previously shown that recombinant human platelet-derived growth factor-AB (rhPDGF-AB) improves cardiac function in a rodent model of MI. To progress clinical translation, we evaluated rhPDGF-AB treatment in a clinically relevant porcine model of myocardial ischemia-reperfusion. Thirty-six pigs were randomized to sham procedure or balloon occlusion of the proximal left anterior descending coronary artery with 7-day intravenous infusion of rhPDGF-AB or vehicle. One month after MI, rhPDGF-AB improved survival by 40% compared with vehicle, and cardiac magnetic resonance imaging showed left ventricular (LV) ejection fraction improved by 11.5%, driven by reduced LV end-systolic volumes. Pressure volume loop analyses revealed improved myocardial contractility and energetics after rhPDGF-AB treatment with minimal effect on ventricular compliance. rhPDGF-AB enhanced angiogenesis and increased scar anisotropy (high fiber alignment) without affecting overall scar size or stiffness. rhPDGF-AB reduced inducible ventricular tachycardia by decreasing heterogeneity of the ventricular scar that provides a substrate for reentrant circuits. In summary, we demonstrated that rhPDGF-AB promotes post-MI cardiac wound repair by altering the mechanics of the infarct scar, resulting in robust cardiac functional improvement, decreased ventricular arrhythmias, and improved survival. Our findings suggest a strong translational potential for rhPDGF-AB as an adjunct to current MI treatment and possibly to modulate scar in other organs.

Renal Artery Denervation in Resistant Hypertension: The Good, The Bad and The Future.

Early studies of renal artery denervation (RAD) demonstrated efficacy in treating resistant hypertension patients with significant reduction in office blood pressure (BP). This resulted in a growing enthusiasm in the field and a rapid evolution of technology with expanding procedural indications. However, the first randomised sham-controlled trial, Symplicity HTN-3, failed to demonstrate a significant difference in BP reduction between the RAD and the sham control arm, which subsequently led to a major reduction in the clinical application of this procedure. Additionally, the results generated further interest into understanding the mechanism and factors affecting procedural success and identifying the limitations within the field. Many lessons were learned from Symplicity HTN-3 trial, and with recent evidence emerging for RAD in hypertension treatment, the field continues to be refined.

Influence of Body Mass Index on Recurrence of Ventricular Arrhythmia, Mortality in Defibrillator Recipients With Ischaemic Cardiomyopathy.

BACKGROUND: Obesity is associated with increased risk of cardiovascular disease. There is little known, however, about the influence of body mass index (BMI) on spontaneously occurring ventricular arrhythmias in patients with ischaemic heart disease. We sought to examine the effect of BMI on the ventricular arrhythmia (VA) recurrence and mortality in defibrillator recipients with ischaemic cardiomyopathy. METHODS: Consecutive patients (n = 123) with ischaemic cardiomyopathy (left ventricular ejection fraction (LVEF) ≤ 40%) and a primary or secondary prevention defibrillator were included. Patients were classified according to their BMI as being normal (18.5-24.99, n = 54/ 43.9%), overweight (2 -29.99, n = 43/ 35%) or obese (>30, n = 26/20.3%). RESULTS: The primary combined endpoint of VA recurrence and mortality occurred in 36%, 5.4% and 11.5% of patients with normal, overweight and obese BMI (p = 0.001). When adjusting for risk factors such as ejection fraction, age and triple vessel disease, on multivariable analysis, normal BMI remained a significant predictor for the primary outcome (Hazard Ratio, Normal vs Overweight = 7.1, 95% CI 1.8-25, p = 0.002: Hazard Ratio, Normal vs Obese = 5.5, 95% CI 1.11-25, p = 0.033). There was a non-significant trend towards reduced survival in patients with normal weight in comparison to overweight and obese patients (p = 0.08). CONCLUSION: In defibrillator recipients with ischaemic cardiomyopathy, BMI appears to be a significant predictor for the combined primary outcome of spontaneously occurring ventricular arrhythmias and mortality. Normal BMI, compared to overweight and obese patients had worse outcomes, suggesting the presence of the obesity paradox in ventricular arrhythmogenesis late post infarction.

Renal Artery Branch Denervation: Evaluation of Lesion Characteristics Using a Thermochromic Liquid Crystal Phantom Model.

BACKGROUND: Lately, combined main vessel and branch ablation has been recommended during radiofrequency (RF) renal artery denervation. Utilising a validated renal artery phantom model, we aimed (1) to determine thermal injury extent (lesion depth, width and circumferential coverage) and electrode-tissue interface temperature for branch renal artery ablation, and (2) to compare the extent of thermal injury for branch versus main vessel ablation using the same RF System. METHODS: We employed a gel based renal artery phantom model simulating variable vessel diameter and flow, which incorporated a temperature sensitive thermochromic-liquid-crystal (TLC) film for assessing RF ablation thermodynamics. Ablations in a branch renal artery model (n = 32) were performed using Symplicity Spyral (Medtronic, Minneapolis, MN, USA). Lesion dimensions defined by the 51 °C isotherm, circumferential injury coverage, and electrode-tissue interface temperature were measured for all ablations at 60 seconds. RESULTS: Lesion dimensions were 2.13 ± 0.13 mm and 4.13 ± 0.18 mm for depth and width, respectively, involving 23% of the vessel circumference. Maximum electrode-tissue interface temperature was 68.31 ± 2.29 °C. No significant difference in lesion depth between branch and main vessel ablations was found (Δ = 0.02 mm, p = 0.60). However, lesions were wider in the branch (Δ=0.49 mm, p < 0.001) with a larger circumferential coverage compared to main vessel (arc angle of 82.02±3.27° versus 54.90±4.36°, respectively). CONCLUSIONS: In the phantom model, branch ablations were of similar depth but had larger width and circumferential coverage compared to main vessel ablations. Concerning safety, no overheating at the electrode-tissue interface was observed.

Analysis of recombinant adeno-associated viral vector shedding in sheep following intracoronary delivery.

Differences between mouse and human hearts pose a significant limitation to the value of small animal models when predicting vector behavior following recombinant adeno-associated viral (rAAV) vector-mediated cardiac gene therapy. Hence, sheep have been adopted as a preclinical animal, as they better model the anatomy and cardiac physiological processes of humans. There is, however, no comprehensive data on the shedding profile of rAAV in sheep following intracoronary delivery, so as to understand biosafety risks in future preclinical and clinical applications. In this study, sheep received intracoronary delivery of rAAV serotypes 2/6 (2 × 1012 vg), 2/8, and 2/9 (1 × 1013 vg) at doses previously administered in preclinical and clinical trials. This was followed by assessment over 96 h to examine vector shedding in urine, feces, nasal mucus, and saliva samples. Vector genomes were detected via real-time quantitative PCR in urine and feces up to 48 and 72 h post vector delivery, respectively. Of these results, functional vector particles were only detected via a highly sensitive infectious replication assay in feces samples up to 48 h following vector delivery. We conclude that rAAV-mediated gene transfer into sheep hearts results in low-grade shedding of non-functional vector particles for all excreta samples, except in the case of feces, where functional vector particles are present up to 48 h following vector delivery. These results may be used to inform containment and decontamination guidelines for large animal dealings, and to understand the biosafety risks associated with future preclinical and clinical uses of rAAV.

Transvascular Pacing of Aorticorenal Ganglia Provides a Testable Procedural Endpoint for Renal Artery Denervation.

OBJECTIVES: This study sought to develop a method to assess renal sympathetic nerve function through localization and pacing of aorticorenal ganglia (ARG). BACKGROUND: Transcatheter renal denervation procedures often fail to produce complete renal denervation because of the lack of a physiological procedural endpoint. METHODS: High-frequency pacing was performed in the inferior vena cava and aorta in sheep (n = 19) to identify ARG pace-capture sites. Group A (n = 5) underwent injection at the ARG pace-capture site for histological verification, group B (n = 6) underwent unilateral irrigated radiofrequency ablation of ARG pace-capture sites and assessment of renal innervation at 1 week post-procedure; and group C (n = 8) underwent ARG pacing before and 2 to 3 weeks after unilateral microwave renal denervation. RESULTS: ARG pace-capture responses were observed at paired discrete sites above the ipsilateral renal artery eliciting a change in mean arterial blood pressure of 22.2 (interquartile range [IQR]: 15.5 to 34.3 mm Hg; p < 0.001) with concurrent ipsilateral renal arterial vasoconstriction, change in main renal artery diameter of -0.42 mm (IQR: -0.64 to -0.24 mm; p < 0.0001), and without consistent contralateral renal vasoconstriction. Sympathetic ganglionic tissue was observed at ARG pace-capture sites, and ganglion ablation led to significant ipsilateral renal denervation. Circumferential renal denervation resulted in immediate and sustained abolition of ARP pacing-induced renal vasoconstriction and significant ipsilateral renal denervation. CONCLUSIONS: Transvascular ARG pace-capture is feasible and recognized by concurrent hypertensive and ipsilateral renal arterial vasoconstrictive responses. Abolition of ARG pacing-induced vasoconstriction may indicate successful renal sympathetic denervation and serve as a physiological procedural endpoint to guide transcatheter renal denervation.

Transcatheter microwave ablation can deliver deep and circumferential perivascular nerve injury without significant arterial injury to provide effective renal denervation.

BACKGROUND: Clinical studies of transcatheter radiofrequency renal denervation for treating hypertension have been hampered by the lack of consistent denervation efficacy. We aimed to demonstrate the short-term efficacy and safety of transcatheter microwave renal denervation. METHODS: A novel 7F microwave system was validated in a sheep model of unilateral renal denervation. Up to two microwave ablations were delivered to each artery with maximum power at 100-110 W for 480 s. RESULTS: Catheter deployment and ablation was successful in all 19 targeted vessel segments, and ablation produced substantial circumferential perivascular injury; median ablation lesion area greater than 395 [interquartile range (IQR) 251-437] mm, depth 17.1 (IQR 15.8-18.4) mm, length 16 (IQR 12-20) mm, without collateral visceral injury. Limiting power to 100 W minimized arterial injury, while maintaining a deep circumferential perivascular ablation. Microwave denervation reduced median functional sympathetic nerve surface area at the renal hilum on antityrosine hydroxylase staining by 100% (IQR 87-100%, P = 0.0039), and median renal cortical norepinephrine content by 83% (IQR 76-92%, P = 0.0078), compared to the paired control kidney at 2-3 weeks postprocedure. CONCLUSION: Transcatheter microwave ablation can produce deep circumferential perivascular ablations over a long segment of the renal artery without significant arterial or collateral visceral injury to provide effective renal denervation.

Comparison of two different radiofrequency ablation systems for renal artery denervation: Evaluation of short-term and long-term follow up.

OBJECTIVES: To assess the clinical efficacy of renal artery denervation (RAD) in our center and to compare the efficacy of two different radiofrequency (RF) systems. BACKGROUND: Several systems are available for RF renal denervation. Whether there is a difference in clinical efficacy among various systems remains unknown. METHODS: Renal artery denervation was performed on 43 patients with resistant hypertension using either the single electrode Symplicity Flex (n = 20) or the multi-electrode EnligHTN system (n = 23). Median post-procedural follow-up was 32.93 months. The primary outcome was post-procedural change in office blood pressure (BP) within 1 year (short-term follow-up). Secondary outcomes were change in office BP between 1 and 4 years (long-term follow-up) and the difference in office BP reduction between the two systems at each follow-up period. RESULTS: For the total cohort, mean baseline office BP (systolic/diastolic) was 174/94 mmHg. At follow-up, mean changes in office BP from baseline were -19.70/-11.86 mmHg (P < 0.001) and -21.90/-13.94 mmHg (P < 0.001) for short-term and long-term follow-up, respectively. The differences in office BP reduction between Symplicity and EnligHTN groups were 8.96/1.23 mmHg (P = 0.42 for systolic BP, P = 0.83 for diastolic BP) and 9.56/7.68 mmHg (P = 0.14 for systolic BP, P = 0.07 for diastolic BP) for short-term and long-term follow-up, respectively. CONCLUSIONS: In our cohort, there was a clinically significant office BP reduction after RAD, which persisted up to 4 years. No significant difference in office BP reduction between the two systems was found.

Quantitative spectral assessment of intracardiac electrogram characteristics associated with post infarct fibrosis and ventricular tachycardia.

BACKGROUND: Post-myocardial infarction (MI) remodeling contributes to increased electrophysiological and structural heterogeneity and arrhythmogenesis. Utilising the post-infarct ovine model our aim was to determine unipolar electrogram frequency characteristics consequent to this remodeling and the development of Ventricular Tachycardia (VT). METHODS AND RESULTS: Mapping studies were performed on 14 sheep at >1 month post-MI induction. Sheep were divided into VT inducible (n = 7) and non-inducible (n = 7) groups. Multielectrode needles (n = 20) were deployed within and surrounding ventricular scar for electrophysiological assessment of electrogram amplitude and width. Spectral analysis of electrograms was undertaken using wavelet and fast fourier transformations (WFFT) to calculate root mean square (RMS) power intervals spanning 0-300Hz in 20Hz intervals. Quantitative assessment between electrophysiological and histological parameters including collagen density, and structural organization of the myocardium was performed. Increasing myocardial scar density resulted in attenuation of electrogram amplitude and RMS values. (all p<0.01). Between groups there were no differences in electrogram amplitude (p = 0.37), however WFFT analysis revealed significantly higher RMS values in the VT group (p<0.05) in association with high frequency fractional components of the electrogram. As scar density increased, greater between-group differences in RMS were observed spanning this high frequency (200-280Hz) spectrum and which were proportionally dependent on the degree of structural disorganisation of the myocardium (p<0.001) and number of extrastimuli required to induce VT (p<0.05). CONCLUSION: High frequency unipolar electrogram spectral characteristics were quantitatively co-influenced by the presence of fibrosis and degree of myocardial structural dissorganisation and were associated with the propensity for development of VT.

Influence of BMI on inducible ventricular tachycardia and mortality in patients with myocardial infarction and left ventricular dysfunction: The obesity paradox.

BACKGROUND: There is little known about the influence of obesity on ventricular electrical remodelling after myocardial infarction. The aim of our study was to assess the relationship between body mass index (BMI) and the primary outcome of inducible-VT and the secondary outcome of all-cause mortality in consecutive patients who presented with ST elevation myocardial infarction (STEMI) and LV-dysfunction (LVEF ≤ 40%). METHODS AND RESULTS: Consecutive patients (n = 380) with STEMI and LV-dysfunction (LVEF ≤ 40%) underwent electrophysiological (EP) studies for risk-stratification. Inducible-VT ≥200 ms cycle-length (CL) with one to four extra-stimuli (ES) was considered abnormal. Patients were classified according their body mass index (BMI) to be normal (18.5-24.9), overweight (25-29.9) or obese (>30). The primary outcome of inducible-VT occurred in 42.7%, 21.5% and 21% of normal weight, overweight and obese patients respectively (p < 0.001). When adjusting for ejection-fraction, hypertension and triple-vessel-disease, normal BMI remained a significant predictor for inducible-VT. All-cause mortality was higher in patients with normal weight (12.8%) when compared to overweight (3.2%) and obese (3.8%) patients (p = 0.002) and was mainly driven by increased cardiac-death (6.8%, 1.9% and 1.9% in normal, overweight and obese patients respectively, p = 0.05). After adjusting for age, EF, and hypertension, normal BMI remained a significant predictor of mortality. CONCLUSION: In patients presenting with STEMI and LV-dysfunction, BMI appears to be a significant predictor of inducible-VT and all-cause mortality, with worse outcomes for those with normal weight, when compared to overweight or obese individuals. These findings are consistent with the obesity-paradox.

Human Connexin40 Mutations Slow Conduction and Increase Propensity for Atrial Fibrillation.

BACKGROUND: Patch clamping studies using non-cardiomyocytes revealed that the human connexin40 mutations P88S, G38D, and A96S are associated with reduced gap junction conductances compared to wild type connexin40 (wtCx40). Their effects within myocytes however are unclear. We aimed to characterise P88S, G38D, and A96S after expression in rat hearts and primary cardiomyocyte cultures. METHODS: Adult Sprague-Dawley rat atria were transduced with a lentivector containing a transgene encoding wtCx40, P88S, G38D, A96S, or eGFP (n=6 per transgene). Electrophysiology studies (EPS) were performed just prior to and 7 days after surgery. Left atria were assessed for connexin expression, mRNA levels, inflammation and fibrosis. Primary cardiomyocyte cultures were also transduced with the abovementioned vectors (n=6 per transgene) and monolayer conduction velocities (CV) and protein expression were assessed at 96hours. RESULTS: At day 7 EPS, P wave and induced atrial fibrillation (AF) durations were significantly longer in the mutant groups when compared to wtCx40 controls (p<0.05). There were no significant differences in inflammation, fibrosis, or heart to body weight ratios. Monolayer CV's were reduced in the A96S group compared to the wtCx40 group. While similar to wtCx40 controls, P88S velocities were reduced compared to eGFP controls. G38D monolayers possessed spontaneous fibrillatory activity and could not be paced. Immunofluorescence revealed that P88S and G38D reduced native connexin43 myocyte coupling while A96S appeared to co-localise with connexin43 in gap junctions. Connexin43 mRNA levels were similar between groups. CONCLUSIONS: The A96S, G38D, and P88S Cx40 mutations slow conduction and increased the propensity for inducible AF.

Influence of Intramyocardial Adipose Tissue on the Accuracy of Endocardial Contact Mapping of the Chronic Myocardial Infarction Substrate.

BACKGROUND: Recent studies have demonstrated that intramyocardial adipose tissue (IMAT) may contribute to ventricular electrophysiological remodeling in patients with chronic myocardial infarction. Using an ovine model of myocardial infarction, we aimed to determine the influence of IMAT on scar tissue identification during endocardial contact mapping and optimal voltage-based mapping criteria for defining IMAT dense regions. METHOD AND RESULTS: In 7 sheep, left ventricular endocardial and transmural mapping was performed 84 weeks (15-111 weeks) post-myocardial infarction. Spearman rank correlation coefficient was used to assess the relationship between endocardial contact electrogram amplitude and histological composition of myocardium. Receiver operator characteristic curves were used to derive optimal electrogram thresholds for IMAT delineation during endocardial mapping and to describe the use of endocardial mapping for delineation of IMAT dense regions within scar. Endocardial electrogram amplitude correlated significantly with IMAT (unipolar r=-0.48±0.12, P<0.001; bipolar r=-0.45±0.22, P=0.04) but not collagen (unipolar r=-0.36±0.24, P=0.13; bipolar r=-0.43±0.31, P=0.16). IMAT dense regions of myocardium reliably identified using endocardial mapping with thresholds of <3.7 and <0.6 mV, respectively, for unipolar, bipolar, and combined modalities (single modality area under the curve=0.80, P<0.001; combined modality area under the curve=0.84, P<0.001). Unipolar mapping using optimal thresholding remained significantly reliable (area under the curve=0.76, P<0.001) during mapping of IMAT, confined to putative scar border zones (bipolar amplitude, 0.5-1.5 mV). CONCLUSIONS: These novel findings enhance our understanding of the confounding influence of IMAT on endocardial scar mapping. Combined bipolar and unipolar voltage mapping using optimal thresholds may be useful for delineating IMAT dense regions of myocardium, in postinfarct cardiomyopathy.

Comparison of new-generation renal artery denervation systems: assessing lesion size and thermodynamics using a thermochromic liquid crystal phantom model.

AIMS: The aim of this study was to evaluate and compare lesion dimensions and thermodynamics of the new-generation multi-electrode Symplicity Spyral and the new-generation multi-electrode EnligHTN renal artery denervation systems, using a thermochromic liquid crystal phantom model. METHODS AND RESULTS: A previously described renal artery phantom model was used as a platform for radiofrequency ablation. A total of 32 radiofrequency ablations were performed using the multi-electrode Symplicity Spyral (n=16) and the new-generation EnligHTN systems (n=16). Both systems were used as clinically recommended by their respective manufacturer. Lesion borders were defined by the 51°C isotherm. Lesion size (depth and width) was measured and compared between the two systems. Mean lesion depth was 2.15±0.02 mm for the Symplicity Spyral and 2.32±0.02 mm for the new-generation EnligHTN (p-value <0.001). Mean lesion width was 3.64±0.08 mm and 3.59±0.05 mm (p-value=0.61) for the Symplicity Spyral and the new-generation EnligHTN, respectively. CONCLUSIONS: The new-generation EnligHTN system produced lesions of greater depth compared to the Symplicity Spyral under the same experimental conditions. Lesion width was similar between both systems. Achieving greater lesion depth by use of the new-generation EnligHTN may result in better efficacy of renal artery denervation.