Metabolic heterogeneous zone assessed by 18 FDG-PET is predictive of postablation mortality in patients with ventricular tachycardia.

PURPOSE: We sought to study the predictive value of the metabolic heterogeneous zone (HZ) as determined by 18 Fluorodeoxyglucose (18 FDG) positron emission tomography (PET) viability studies in ventricular tachycardia (VT) patients. METHODS: PET studies utilizing 82 Rubidium (82 Rb) tracer for perfusion and 18 FDG tracer for viability were analyzed using PMOD (PMOD Technologies) and further analyzed using 684-segment plots. 18 FDG uptake was normalized to the area with maximal perfusion on the rest 82 Rb study. Metabolic scar, HZ, and healthy segments were defined with perfusion-normalized 18 FDG uptake between 0%-50%, 50%-70%, and >70%, respectively. RESULTS: Thirty-four VT patients (age, 63 ± 12 years) were evaluated with 18 FDG-PET viability study. Most (n = 31) patients underwent VT ablation. Patients were categorized to HZ < median versus HZ ≥ median based on a median HZ area size of 21.0 cm2 . HZ size was significantly larger in the deceased group than the alive group (35.2 cm2 vs. 18.1 cm2 , p = .01). Deaths were significantly higher in HZ ≥ 21 cm2 group than HZ < 21 cm2 group (58.8% vs. 11.8%, p = .005). Survival analysis showed significantly higher mortality in the HZ ≥ 21 cm2 group than the HZ < 21 cm2 group (HR = 4.1, 95% CI: 1.3-12.6, p = .016). In a multivariable analysis, HZ was found to be an independent predictor for all-cause mortality (HR = 1.07, 95% CI: 1.02-1.12, p = .01) CONCLUSIONS: Increased HZ size of myocardium was associated with increased mortality. Metabolic HZ quantification may be of value in risk stratification and management of ischemic and nonischemic patients with VT.

Comparison of Velocity-Based and Traditional Percentage-Based Loading Methods on Maximal Strength and Power Adaptations.

Dorrell, HF, Smith, MF, and Gee, TI. Comparison of velocity-based and traditional percentage-based loading methods on maximal strength and power adaptations. J Strength Cond Res 34(1): 46-53, 2020-This study explored the effects of velocity-based training (VBT) on maximal strength and jump height. Sixteen trained men (22.8 ± 4.5 years) completed a countermovement jump (CMJ) test and 1 repetition maximum (1RM) assessment on back squat, bench press, strict overhead press, and deadlift, before and after 6 weeks of resistance training. Participants were assigned to VBT or percentage-based training (PBT) groups. The VBT group's load was dictated through real-time velocity monitoring, as opposed to pretesting 1RM data (PBT). No significant differences were present between groups for pretesting data (p > 0.05). Training resulted in significant increases (p < 0.05) in maximal strength for back squat (VBT 9%, PBT 8%), bench press (VBT 8%, PBT 4%), strict overhead press (VBT 6%, PBT 6%), and deadlift (VBT 6%). Significant increases in CMJ were witnessed for the VBT group only (5%). A significant interaction effect was witnessed between training groups for bench press (p = 0.004) and CMJ (p = 0.018). Furthermore, for back squat (9%), bench press (6%), and strict overhead press (6%), a significant difference was present between the total volume lifted. The VBT intervention induced favorable adaptations in maximal strength and jump height in trained men when compared with a traditional PBT approach. Interestingly, the VBT group achieved these positive outcomes despite a significant reduction in total training volume compared with the PBT group. This has potentially positive implications for the management of fatigue during resistance training.

Validity and reliability of a linear positional transducer across commonly practised resistance training exercises.

This study investigated the validity and reliability of the GymAware PowerTool (GPT). Thirteen resistance trained participants completed three visits, consisting of three repetitions of free-weight back squat, bench press, deadlift (80% one repetition maximum), and countermovement jump. Bar displacement, peak and mean velocity, peak and mean force, and jump height were calculated using the GPT, a three-dimensional motion capture system (Motion Analysis Corporation; 150 Hz), and a force plate (Kistler; 1500 Hz). Least products regression were used to compare agreeability between devices. A within-trial one-way ANOVA, typical error (TE; %), and smallest worthwhile change (SWC) were used to assess reliability. Regression analysis resulted in R2 values of >0.85 for all variables excluding deadlift mean velocity (R2 = 0.54-0.69). Significant differences were observed between visits 3-2 for bench press bar displacement (0.395 ± 0.055 m; 0.383 ± 0.053 m), and deadlift bar displacement (0.557 ± 0.034 m; 0.568 ± 0.034 m). No other significant differences were found. Low to moderate TE (0.6-8.8%) were found for all variables, with SWC ranging 1.7-7.4%. The data provides evidence that the GPT can be used to measure kinetic and kinematic outputs, however, care should be taken when monitoring deadlift performance.

The effect of time-of-flight and point spread function modeling on 82Rb myocardial perfusion imaging of obese patients.

BACKGROUND: The effect of time-of-flight (TOF) and point spread function (PSF) modeling in image reconstruction has not been well studied for cardiac PET. This study assesses their separate and combined influence on 82Rb myocardial perfusion imaging in obese patients. METHODS: Thirty-six obese patients underwent rest-stress 82Rb cardiac PET. Images were reconstructed with and without TOF and PSF modeling. Perfusion was quantitatively compared using the AHA 17-segment model for patients grouped by BMI, cross-sectional body area in the scanner field of view, gender, and left ventricular myocardial volume. Summed rest scores (SRS), summed stress scores (SSS), and summed difference scores (SDS) were compared. RESULTS: TOF improved polar map visual uniformity and increased septal wall perfusion by up to 10%. This increase was greater for larger patients, more evident for patients grouped by cross-sectional area than by BMI, and more prominent for females. PSF modeling increased perfusion by about 1.5% in all cardiac segments. TOF modeling generally decreased SRS and SSS with significant decreases between 2.4 and 3.0 (P < .05), which could affect risk stratification; SDS remained about the same. With PSF modeling, SRS, SSS, and SDS were largely unchanged. CONCLUSION: TOF and PSF modeling affect regional and global perfusion, SRS, and SSS. Clinicians should consider these effects and gender-dependent differences when interpreting 82Rb perfusion studies.

Status of cardiovascular PET radiation exposure and strategies for reduction: An Information Statement from the Cardiovascular PET Task Force.

Cardiovascular positron emission tomography (PET) imaging provides high-quality visual and quantitative myocardial perfusion and function images. In addition, cardiovascular PET can assess myocardial viability, myocardial inflammatory disorders such as cardiac sarcoid, and infections of implanted devices including pacemakers, ventricular assist devices, and prosthetic heart valves. As with all nuclear cardiology procedures, the benefits need to be considered in relation to the risks of exposure to radiation. When performed properly, these assessments can be obtained while simultaneously minimizing radiation exposure. The purpose of this information statement is to present current concepts to minimize patient and staff radiation exposure while ensuring high image quality.

Effects of Resistance Band Exercise on Vascular Activity and Fitness in Older Adults.

This study investigated the effects of a low to moderately intense resistance-band exercise intervention on cutaneous microvascular function in an older population. 18 sedentary healthy participants (age: 58±5) were assessed for their upper and lower-limb endothelial cutaneous vascular conductance using laser Doppler fluximetry with endothelial-dependent (80 µl acetylcholine chloride), and -independent vasodilation (80 µl sodium nitroprusside). In addition, participants underwent a range of functional assessments (cardiopulmonary fitness, strength, flexibility), and completed a perceived quality of life questionnaire. Participants were randomised into 2 groups: Exercise (EX) and Control (CON), and followed either an 8-week self-supervised home-based resistance-band intervention or maintained their habitual lifestyle. Following post-intervention assessment (n=16; EX=7, CON=9), EX improved acetylcholine-chloride-mediated endothelial-dependent vasodilation within the lower limb (cutaneous vascular conductance at 2 000 µCb; P<0.01), but without associated changes in the upper limb. Exercise, compared to CON, significantly affected sodium-nitroprusside-mediated independent vasodilation in the upper limb (P<0.01) at 2 000 µCb, but without associated changes in the lower limb. Of functional assessments, only lower limb strength and flexibility improved for EX (P<0.05). EX experienced positive changes within global measures of General Health, Bodily Pain and Energy/Fatigue (P<0.05). An 8-week home-based resistance-band exercise programme improves age-provoked microcirculatory endothelial vasodilation, but without concomitant changes in cardiopulmonary and anthropometric measures.

TandemPET- A High Resolution, Small Animal, Virtual Pinhole-Based PET Scanner: Initial Design Study.

Mice are the perhaps the most common species of rodents used in biomedical research, but many of the current generation of small animal PET scanners are non-optimal for imaging these small rodents due to their relatively low resolution. Consequently, a number of researchers have investigated the development of high-resolution scanners to address this need. In this investigation, the design of a novel, high-resolution system based on the dual-detector, virtual-pinhole PET concept was explored via Monte Carlo simulations. Specifically, this system, called TandemPET, consists of a 5 cm × 5 cm high-resolution detector made-up of a 90 × 90 array of 0.5 mm × 0.5 mm × 10 mm (pitch= 0.55 mm) LYSO detector elements in coincidence with a lower resolution detector consisting of a 68 × 68 array of 1.5 mm × 1.5 mm × 10 mm LYSO detector elements (total size= 10.5 cm × 10.5 cm). Analyses indicated that TandemPET's optimal geometry is to position the high-resolution detector 3 cm from the center-of-rotation, with the lower resolution detector positioned 9 cm from center. Measurements using modified NEMA NU4-2008-based protocols revealed that the spatial resolution of the system is ~0.5 mm FWHM, after correction of positron range effects. Peak sensitivity is 2.1%, which is comparable to current small animal PET scanners. Images from a digital mouse brain phantom demonstrated the potential of the system for identifying important neurological structures.

Mediterranean diet- and exercise-induced improvement in age-dependent vascular activity.

The aging effect on microvascular integrity, marked by endothelial dysfunction and reduction in exercise tolerance, is a major cause of CVD (cardiovascular disease). Improved dietary habits, known to reduce morbidity and mortality, are also known to attenuate those aging effects. The present study investigated the effects of combined MD (Mediterranean diet) and exercise intervention on lower- and upper-limb cutaneous microvascular functions in an older healthy population. A total of 22 sedentary healthy participants (age, 55±4 years) underwent cardiopulmonary exercise tolerance test, and were assessed for their upper- and lower-limb vascular endothelial CVC (cutaneous vascular conductance) using LDF (laser Doppler fluximetry) with endothelium-dependent [ACh (acetylcholine chloride)] and -independent [SNP (sodium nitroprusside)] vasodilation. Participants were then randomized into two groups: MD and non-MD, and followed an 8-week intervention programme, which included discontinuous treadmill running based on each individual's exertion, twice per week. Exercise training improved CVC in both groups (e.g. 0.42±0.19 compared with 1.50±1.05 and 0.47±0.26 compared with 1.15±0.59 at 1000 µCb for MD and non-MD respectively; P<0.001). This was also combined by improvement in the exercise tolerance indicated by increased VT (ventilatory threshold) in both groups [12.2±2.8 compared with 14.8±2.8 ml·(kg of body weight)(-1)·min(-1) and 11.7±2.7 compared with 14.6±3.2 ml·(kg of body weight)(-1)·min(-1) for MD and non-MD groups respectively; P<0.05]. However, the MD group showed greater improvement in endothelium-dependent vasodilation than non-MD [ANCOVA (analyses of co-variance), P=0.02]. The results of the present study suggest that compliance with MD, combined with regular moderate exercise, improves age-provoked microcirculatory endothelial dysfunction and increases exercise tolerance, both responsible for reducing cardiovascular risk in this age group.

Recent advances in cardiac SPECT instrumentation and system design.

Recent advances in clinical cardiac SPECT instrumentation are reviewed from a systems perspective. New hardware technologies include pixelated scintillator and semiconductor detector elements; photodetectors such as position-sensitive photomultiplier tubes (PSPMT), avalanche photodiodes (APD) and silicon photomultipliers (SiPM); and novel cardiac collimation methods. There are new approaches for positioning detectors and controlling their motion during cardiac imaging. Software technology advances include iterative image reconstruction with modeling of Poisson statistics and depth-dependent collimator response. These new technologies enable faster acquisitions, the lowering of administered activity and radiation dose, and improved image resolution. Higher sensitivity collimators are a significant factor enabling faster acquisitions. Several clinical systems incorporating new technologies are discussed and different system designs can achieve similar performance. With detector elements such as APDs, SiPMs and semiconductors that are insensitive to magnetic fields, the potential for cardiac SPECT imagers that are MRI compatible opens up new frontiers in clinical cardiac research and patient care.

Effect of acute mild dehydration on cognitive-motor performance in golf.

Whether mild dehydration (-1 to 3% body mass change [ΔBM]) impairs neurophysiological function during sport-specific cognitive-motor performance has yet to be fully elucidated. To investigate this within a golfing context, 7 low-handicap players (age: 21 ± 1.1 years; mass: 76.1 ± 11.8 kg; stature: 1.77 ± 0.07 m; handicap: 3.0 ± 1.2) completed a golf-specific motor and cognitive performance task in a euhydrated condition (EC) and dehydrated condition (DC) (randomized counterbalanced design; 7-day interval). Dehydration was controlled using a previously effective 12-hour fluid restriction, monitored through ΔBM and urine color assessment (UCOL). Mild dehydration reduced the mean BM by 1.5 ± 0.5% (p = 0.01), with UCOL increasing from 2 (EC) to 4 (DC) (p = 0.02). Mild dehydration significantly impaired motor performance, expressed as shot distance (114.6 vs. 128.6 m; p < 0.001) and off-target accuracy (7.9 vs. 4.1 m; p = 0.001). Cognitive performance, expressed as the mean error in distance judgment to target increased from 4.1 ± 3.0 m (EC) to 8.8 ± 4.7 m (DC) (p < 0.001). The findings support those of previous research that indicates mild dehydration (-1 to 2% ΔBM) significantly impairs cognitive-motor task performance. This study is the first to show that mild dehydration can impair distance, accuracy, and distance judgment during golf performance.

Effect of Graded Targeted Temperature Management on Cerebral Glucose Spatiotemporal Characteristics after Cardiac Arrest.

Cardiac arrest (CA) is a fatal disease with high rates of neurological impairment. At present, targeted temperature management (TTM) is the only strategy with firm clinical evidence to prove its effectiveness. However, there is still controversy on the implementation of TTM, particularly on its depth, with a lack of elucidated underlying therapeutic mechanisms. Six Wistar rats were subjected to 8 min asphyxia-CA and randomly divided into TTM at 33oC(n=3) or 35° C groups (n=3). The spatiotemporal characteristics of cerebral glucose metabolism after CA were investigated by 18F-FDG microPET/CT. Myelin Basic Protein (MBP) immunofluorescence staining was used to assess acute injury and recovery of oligodendrocytes. Functional recovery was evaluated using the neurological deficit score (NDS). There was a significant improvement in functional recovery by NDS (p < 0.05) in the 33oC group compared with the 35° C group. Glucose metabolism of the 33° C group was higher than that of the 35oC group early after resuscitation (within 10 minutes). Immunofluorescence analysis showed that positive MBP signals in the cortex and hippocampus in the 33oC group were greater than in the 35oC group. In conclusion, compared to 35oC TTM, 33° C TTM changed the spatiotemporal characteristics of brain glucose metabolisms with improved neurological function, which may be through oligodendrocyte participation.

Motion-tracking technique in unrestrained small-animal single-photon emission computed tomography.

Medical researchers have used structural and functional imaging techniques to study various neurological phenomena. Humans are typically conscious for both structural and functional neuroimaging studies. The use of functional neuro-imaging techniques in mouse-based animal models is typically accomplished with restrained or anesthetized mice. A system was developed to perform functional imaging with single-photon emission computed tomography of awake mice to avoid the confounding influences of anesthesia or physical restraint. This review article provides an overview of the technique and how it is presently being used. The system is designed for brain imaging and uses infrared reflectors to track the head position as a function of time. The detected photons are acquired in list mode and are time-stamped. The position of the rotating gamma camera is also recorded as a function of time. These three sets of data are integrated together in an iterative image reconstruction program that performs motion compensation. The successful performance of the system is demonstrated in moving phantom and awake animal studies. The system and methodology has the potential of being a powerful tool in behavioral neuroimaging studies involving awake, unrestrained mice.

Pre-clinical myocardial metabolic alterations in chronic kidney disease.

UNLABELLED: The risk for cardiovascular events conferred by decreased renal function is curvilinear with exponentially greater increases in risk as estimated glomerular filtration rate (eGFR) declines. In 13 non-diabetic pre-dialysis chronic kidney disease (CKD) patients, we employed quantitative F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) as a means to measure myocardial metabolic changes. METHODS: Dynamic cardiac FDG PET images were acquired after 6 h fasting and glucose loading. Corrections for attenuation, scatter, randoms, dead time and decay were applied to the PET data and myocardial glucose utilization (MGU) was calculated using the Patlak method in conjunction with standardized myocardial regions of interest and an image-derived input function (left atrium). MGU was compared with eGFR based on a serum creatinine drawn within 2 weeks of the study date. RESULTS: MGU was relatively uniform between the myocardial sectors (coefficient of variation = 16.2 +/- 6.8%) within each patient. Between patients, whole myocardium MGU varied considerably with a range of 37.3-156.2 micromol/min/100 g and a mean of 68.9 +/- 38.3 mumol/min/ 100 g. eGFR ranged from 11-89 ml/min/1.73 m(2) with a mean of 42.8 +/- 26.9 ml/min/1.73 m(2). There was an inverse correlation between whole myocardium MGU and eGFR (Spearman's rho correlation = -0.615, p = 0.025). In multivariate analysis, the relationship between MGU and eGFR was sustained with adjustment for age, race and gender (adjusted beta = -1.56 +/- 0.48, p = 0.01). There was no correlation between cardiac workload and eGFR (p = NS). CONCLUSIONS: A significant inverse correlation between MGU and eGFR is supportive of the hypothesis that CKD is associated with myocardial metabolic changes, which could not be attributed to demographic factors or cardiac workload. Dynamic FDG PET could provide a sensitive, non-invasive, quantitative tool for investigating pre-clinical myocardial abnormalities in patients with CKD.

Effects of exercise, cognitive, and dual-task interventions on cognition in type 2 diabetes mellitus: A systematic review and meta-analysis.

INTRODUCTION: Previous evidence has shown significant effects of exercise, cognitive and dual-task training for improving cognition in healthy cohorts. The effects of these types of interventions in type 2 diabetes mellitus is unclear. The aim of this research was to systematically review evidence, and estimate the effect, of exercise, cognitive, and dual-task interventions on cognition in type 2 diabetes mellitus. METHOD: Electronic databases including PubMed, EMBASE, CINAHL, PsycINFO, SPORTDiscus, and MEDLINE were searched for ongoing and completed interventional trials investigating the effect of either an exercise, cognitive or dual-task intervention on cognition in type 2 diabetes mellitus. RESULTS: Nine trials met the inclusion criteria-one dual-task, two cognitive, and six exercise. Meta-analyses of exercise trials showed no significant effects of exercise on measures of executive function (Stroop task, SMD = -0.31, 95% CI -0.71-0.09, P = 0.13, trail making test part A SMD = 0.28, 95% CI -0.20-0.77 P = 0.25, trail making test part B SMD = -0.15, 95% CI -0.64-0.34 P = 0.54, digit symbol SMD = 0.09, 95% CI -0.39-0.57 P = 0.72), and memory (immediate memory SMD = 0.20, 95% CI -0.28-0.69, P = 0.41 and delayed memory SMD = -0.06, 95% CI -0.55-0.42, P = 0.80). A meta-analysis could not be conducted using cognitive or dual-task data, but individual trials did report a favourable effect of interventions on cognition. Risk of bias was considered moderate to high for the majority of included trials. CONCLUSIONS: Meta-analyses of exercise trials identified a small effect size (0.31), which whilst not significant warrants further investigation. Larger and more robust trials are needed that report evidence using appropriate reporting guidelines (e.g. CONSORT) to increase confidence in the validity of results. TRIAL REGISTRATION: Protocol was registered (CRD42017058526) on the International Prospective Register of Systematic Reviews (http://www.crd.york.ac.uk/PROSPERO).

Clinical application of PET/CT fusion imaging for three-dimensional myocardial scar and left ventricular anatomy during ventricular tachycardia ablation.

Integration of 3D PET with Voltage Map for VT Ablation. Background: Image integration has the potential to display three-dimensional (3D) scar anatomy and facilitate substrate characterization for ventricular tachycardia (VT) ablation. However, the current generation of clinical mapping systems cannot display 3D left ventricle (LV) anatomy with embedded 3D scar reconstructions or allow display of border zone and high-resolution anatomic scar features. Objective: This study reports the first clinical experience with a mapping system allowing an integrated display of 3D LV anatomy with detailed 2D/3D scar and border zone reconstruction. Methods: Ten patients scheduled for VT ablation underwent contrast-enhanced computed tomography (CT) and Rubidium-82 perfusion/F-18 Fluorodeoxyglucose metabolic Positron Emission Tomography (PET) imaging to reconstruct 3D LV and scar anatomy. LV and scar models were co-registered using a 3D mapping system and analyzed with a 17-segment model. Metabolic thresholding was used to reconstruct the 3D border zone. Real-time display of CT images was performed during ablation. Results: Co-registration (error 4.3 +/- 0.7 mm) allowed simultaneous visualization of 3D LV anatomy and embedded scar and guided additional voltage mapping. Segments containing homogenous or partial scar correlated in 94.4% and 85.7% between voltage maps and 3D PET scar reconstructions, respectively. Voltage-defined scar and normal myocardium had relative FDG uptakes of 40 +/- 13% and 89 +/- 30% (P < 0.05). The 3D border zone correlated best with a 46% metabolic threshold. Real-time display of registered high-resolution CT images allowed the simultaneous characterization of scar-related anatomic changes. Conclusion: Integration of PET/CT reconstruction allows simultaneous 3D display of myocardial scar and border zone embedded into the LV anatomy as well as the display of detailed scar anatomy. Multimodality imaging may enable a new image-guided approach to substrate-guided VT ablation.

Effect of plyometric training on swimming block start performance in adolescents.

This study aimed to identify the effect of plyometric training (PT), when added to habitual training (HT) regimes, on swim start performance. After the completion of a baseline competitive swim start, 22 adolescent swimmers were randomly assigned to either a PT (n = 11, age: 13.1 +/- 1.4 yr, mass: 50.6 +/- 12.3 kg, stature: 162.9 +/- 11.9 cm) or an HT group (n = 11, age: 12.6 +/- 1.9 yr, mass: 43.3 +/- 11.6 kg, stature: 157.6 +/- 11.9 cm). Over an 8-week preseason period, the HT group continued with their normal training program, whereas the PT group added 2 additional 1-hour plyometric-specific sessions, incorporating prescribed exercises relating to the swimming block start (SBS). After completion of the training intervention, post-training swim start performance was reassessed. For both baseline and post-trials, swim performance was recorded using videography (50 Hz Canon MVX460) in the sagital plane of motion. Through the use of Silicon Coach Pro analysis package, data revealed significantly greater change between baseline and post-trials for PT when compared with the HT group for swim performance time to 5.5 m (-0.59 s vs. -0.21 s; p < 0.01) and velocity of take-off to contact (0.19 ms vs. -0.07 ms; p < 0.01). Considering the practical importance of a successful swim start to overall performance outcome, the current study has found that inclusion of suitable and safely implemented PT to adolescent performers, in addition to HT routines, can have a positive impact on swim start performance.

Effectiveness of Whey Protein Hydrolysate and Milk-Based Formulated Drinks on Recovery of Strength and Power Following Acute Resistance Exercise.

Intensive resistance exercise can result in exercise-induced-muscle-damage, which commonly leads to reductions in acute muscle function. Post-exercise ingestion of carbohydrate-protein mixtures intends to attenuate these effects. This study aimed to compare the effectiveness of whey protein hydrolysate and milk-based formulated drinks on recovery of muscle function following resistance exercise. Thirty resistance-trained males were randomly assigned to either whey hydrolysate and dextrose drink (WH), milk-based drink (MB) or flavored-dextrose (CHO), and performed baseline assessments of perceived-muscle-soreness, the countermovement jump, the seated-medicine-ball throw and isokinetic assessment of the knee extensors and flexors maximal strength. Subsequently, participants performed resistance exercise consisting of various multi-joint barbell exercises. Following resistance exercise participants then consumed either WH (533 Kcal, 32.6 g Protein, 98.3 g Carbohydrate, 1.1 g Fat), MB (532 Kcal, 32.8 g Protein, 98.4 g Carbohydrate, 0.6 g Fat) or CHO (531 Kcal, 0 g Protein, 132.7 g Carbohydrate, 0 g Fat). All assessments were repeated 24 and 48 h post-resistance exercise. Muscle soreness was markedly increased at 24 h and 48 h in all groups (p < 0.001). However, for dynamic power measures (countermovement jump, seated-medicine-ball throw), CHO experienced a decrease for the countermovement jump only at 48 h, whereas WH and MB experienced significant decreases across the countermovement jump and the seated-medicine-ball throw (p < 0.05). All groups experienced significant decreases in isokinetic-extension torque at both 24 h and 48 h; however, flexion torque was decreased for CHO only at these time points (p < 0.05). Consumption of WH or MB did not enhance recovery of dynamic power-producing ability or soreness compared to CHO. Based on within-group effects WH and MB ingestion had seemingly marginal to small positive effects on recovery of isokinetic strength, however, there were no between-group differences for these variables.

Ventricular Tachycardia (VT) Substrate Characteristics: Insights from Multimodality Structural and Functional Imaging of the VT Substrate Using Cardiac MRI Scar, 123I-Metaiodobenzylguanidine SPECT Innervation, and Bipolar Voltage.

Postischemic adaptation results in characteristic myocardial structural and functional changes in the ventricular tachycardia (VT) substrate. The aim of this study was to compare myocardial structural and functional adaptations (late gadolinium enhancement/abnormal innervation) with detailed VT mapping data to identify regional heterogeneities in postischemic changes. Methods: Fifteen patients with ischemic cardiomyopathy and drug-refractory VT underwent late gadolinium enhancement cardiac MRI (CMR), 123I-metaiodobenzylguanidine SPECT, and high-resolution bipolar voltage mapping to assess fibrosis (>3 SDs), abnormal innervation (<50% tracer uptake), and low-voltage area (<1.5 mV), respectively. Three-dimensional reconstructed CMR/123I-metaiodobenzylguanidine models were coregistered for further comparison. Results: Postischemic structural and functional adaptations in all 3 categories were similar in size (reported as median [quartile 1-quartile 3]: CMR scar, 46.1 cm2 [33.1-86.9 cm2]; abnormal innervation, 47.8 cm2 [40.5-68.1 cm2]; and low-voltage area, 29.5 cm2 [24.5-102.6 cm2]; P > 0.05). However, any single modality underestimated the total VT substrate area defined as abnormal in at least 1 of the 3 modalities (76.0 cm2 [57.9-143.2 cm2]; P < 0.001). Within the total VT substrate area, regions abnormal in all 3 modalities were most common (25.2%). However, significant parts of the VT substrate had undergone heterogeneous adaptation (abnormal in <3 modalities); the most common categories were "abnormal innervation only" (18.2%), "CMR scar plus abnormal innervation only" (14.9%), and "CMR scar only" (14.6%). All 14 VT channel/exit sites (0.88 ± 0.74 mV) were localized to myocardium demonstrating CMR scar and abnormal innervation. This specific tissue category accounted for 68.3% of the CMR scar and 31.2% of the total abnormal postischemic VT substrate area. Conclusion: Structural and functional imaging demonstrated regional heterogeneities in the postischemic VT substrate not appreciated by any single modality alone. The coexistence of abnormal innervation and CMR scar may identify a particularly "proarrhythmic" adaptation and may represent a potential novel target for VT ablation.