As a result, an increasing number of toxicity cases caused by supplements are reported. In this report, we are describing a case of a life-threatening polymorphic ventricular tachycardia in a young female who had recently started taking an OTC fat burner containing raspberry ketones as an ingredient. During hospitalization, she experienced resistant PVT that responded only to a temporary transvenous pacemaker with overdrive pacing. The increasing rate of reported toxicity of fat-burning supplements warrants attention by FDA to impose more regulation and oversight for this industry. The patient was a 32-year-old obese female with no known past medical history who presented with fever and perianal pain for five days. She was found to have a perirectal abscess and underwent incision and drainage. A baseline laboratory work-up showed leukocytosis with a white blood cell count of 19.7 k/uL . Serum electrolytes, kidney function, and liver function were normal. The baseline electrocardiogram of the patient showed a heart rate of 83 with a QT of 393 and a borderline normal QTc of 462 . She was working with physical therapy on the floor when she became unresponsive and had a pulseless electrical activity arrest. Code blue was called with the return of spontaneous circulation achieved after one round of cardiopulmonary resuscitation , and the patient was transferred to the Intensive Care Unit . After transfer to the ICU, the patient had PVT requiring defibrillation shock . She briefly converted to sinus rhythm but the PVT recurred – over 2 hours she received 33 defibrillation shocks in addition to magnesium, calcium chloride, amiodarone, plastic pot black and lidocaine per Advanced Cardiac Life Support protocol.
Amiodarone and lidocaine drips were initiated but on-call Cardiology recommended the discontinuation of amiodarone. When Cardiology arrived at the bedside, an emergent transvenous pacemaker was placed with overdrive pacing, which successfully terminated the arrhythmia. The patient’s baseline EKG was normal. Post arrhythmia, no QTc prolongation or shortening was identified on multiple EKGs and telemetry monitoring did not show any sinus pauses. Electrolytes were within normal limits. The urine drug screen was negative. Post-arrest echocardiogram showed a left ventricular ejection fraction of 20% with global hypokinesis possibly secondary to myocardial stunning from multiple shocks. The patient did not undergo a coronary angiogram hence ischemia was unable to be fully excluded as a precipitating cause behind her PVT; however, she did not have any troponin elevation and there were no ST-T changes on repeat EKGs. Family history was not significant for premature coronary artery disease, arrhythmia, or sudden death. After extensive discussion with family members, it was revealed that the patient had recently started taking an OTC fat burner that contained high amounts of raspberry ketones. The patient was discharged on a life vest and followed up with Cardiology. She underwent an outpatient cardiac electrophysiological study which was unremarkable, and she had a repeat echocardiogram which showed normal cardiac function with normalization of her left ventricular ejection fraction. Due to her uncomplicated post-discharge course life vest was removed. PVT is a type of arrhythmia characterized by multiple foci in the ventricles resulting in QRS complexes that vary significantly in amplitude, duration, and morphology. Differential diagnosis of PVT includes cardiac ischemia, cardiomyopathies, electrolyte abnormalities, electrophysiologic abnormalities , and certain medications. A ventricular electrical storm also known as an arrhythmic storm is characterized by ≥ 3 episodes of sustained tachycardia or defibrillations within 24 hours.
In the acute setting, management of VT may require immediate cardioversion, defibrillation, or administration of antiarrhythmic drugs. Refractory ventricular electrical storm can be terminated with a transvenous pacemaker. Long-term management includes ablation or implantable cardioverter defibrillator implantation among whom a completely reversible cause is not identified. In our patient with a lack of major cardiac risk factors, the run of VT was possibly induced by a combination of the stress of infection and OTC dietary supplements containing high amounts of raspberry ketones. OTC dietary supplements often cause ingredients that can precipitate arrhythmias and sudden cardiac death. Dietary supplements for weight loss are becoming more and more popular due to the increasing prevalence of obesity. These supplements are not tightly regulated by the US FDA and oftentimes lack vigorous quality control and safety standards. In the past, many weight loss supplements were withdrawn from the market due to their safety concerns and adverse effects related to cardiovascular complications, risk of suicide, and depression. Fat burners are a type of dietary supplement which is thought to increase fat metabolism and energy consumption and hence facilitate weight loss. One such fat burner is raspberry ketone, which became popular for weight loss after it was mentioned on the Dr. Oz television show during the segment called “Raspberry ketone: Miracle fat-burner in a bottle” in February 2012. Raspberry ketones are structurally related to a stimulant compound called synephrine and are thought to possibly activate the β-adrenergic receptors. Animal studies suggest that raspberry ketones enable weight loss through various mechanisms, including norepinephrine-induced lipolysis. At least one case of coronary vasospasm has been associated with raspberry ketone intake. Investigations of raspberry ketone in quantitative structure-activity relationship models indicated potential cardiotoxic effects.
To improve safety and limit adverse effects, dietary supplements need to be more closely regulated. All ingredients in the supplement should be listed on the bottle with their exact amount and associated side effects. Public awareness, strict regulation policies by the government, along with visible clearly stated disclaimers from the manufacturers should be encouraged. Increasing temperatures and temperature variability associated with a changing climate have become a major concern for many wine grape growing regions due to their effect on grape and wine composition. As is true for other crops, adequate sun exposure is vital because grapevines need sunlight for photosynthesis, growth, and development, and absorbed radiation by the berries is crucial for the biochemical and physiological processes that determine grape berry quality. Regrettably, excess sunlight and elevated temperatures are negatively affecting grape productivity in many growing regions. In California, minimum and maximum annual temperatures have increased from 1985 to 2011 by 2.34◦C and 1.77◦C, respectively, and in the summers by 3.88◦C and 3.31◦C, respectively. In Oakville, CA, Mart´ınez-Luscher et al. ¨ reported that elevated temperatures for grape clusters resulted in unbalanced wines with higher pH and lower levels of anthocyanins. Other research in Murrumbidgee, Australia reported that temperatures exceeding 40◦C result in delaying ripening and causing berry sunburn. Thus, strategies to minimize harmful berry temperatures are needed to sustain production in warm climates. It is challenging to manage the grapevine canopy to reduce the effect of excess temperature because of the complex interactions between plant architecture and the environment. Traditionally, it has been recommended to time canopy management to maintain sun-exposure for young fruits, but also to allow some shading of mature grape clusters to prevent excess sun exposure. Although increasing the shade in vineyards palliates the effect of elevated temperature, trade-offs need to be evaluated as well. For instance, shaded clusters can cause delay in fruit ripening, reduce wine quality, and increase disease prevalence due to pathogens such as bunch rot and powdery mildew. The negative effects of elevated temperature on grape berries could likely be mitigated in many cases if the complex interactions between canopy architecture and microclimate were better understood and predicted at the berry level. Developing and evaluating proposed mitigation strategies experimentally based on field trials is costly and time-consuming, plastic growers pots which can limit their breadth and generalizability. Crop models can have the potential to extrapolate the results of a limited set of experiments through systematic variation of relevant variables, however, there are currently no models available that can represent varying grapevine architectures and their effect on spatial and temporal fluctuations in grape berry temperature. Through three different studies, this dissertation aims to 1) investigate the impact of the heterogeneous and anisotropic vegetation structure characteristic of grapevines on light interception, 2) develop a 3D model to simulate grape berry temperature in response to varying vineyard architecture and topography, and 3) identify strategies that have the potential to mitigate unfavorable temperatures in grape berries. Chapter 2 evaluates widely used assumptions when modeling solar radiation interception in plant canopies. The solar radiation intercepted by plant canopies is a fundamental driver of biophysical processes on Earth, and thus, quantifying such interception is a critical part of understanding and predicting a wide range of processes occurring at the land-atmosphere interface. The study showed that using a 1D model to simulate light interception for discontinuous canopies resulted in overestimation of light interception by up to 115% for the cases considered.
These results highlighted the need to use a 3D radiation model to account for complex canopies because these models can represent the vertical and horizontal variability in the canopy and its effect on light interception accurately. Chapter 3 develops a 3D model that can accurately resolve spatial and temporal heterogeneity in berry temperature. The spatially-explicit nature of the model allows for robust representation of varying canopy architectures and their effect on berry temperature. The high model complexity is afforded by performing calculations in parallel on the computer’s graphic processing unit . This ability to resolve the geometry of the vineyard is critical in this particular study because it means the model is robust to changes in row spacing, trellis system, row height, etc. To generate data for validation of the 3D grape berry temperature model, field and laboratory experiments were conducted. Validation results demonstrated that by accurately representing the 3D vine structure, the model was able to closely replicate measured spatial and temporal fluctuations in berry temperature. Chapter 4 aims to explore whether elevated berry temperature can be mitigated by designing and managing vineyards in a way that effectively creates a favorable microclimate for berry development. Identifying strategies that have the potential to reduce elevated temperatures in a warming climate is of great interest to grape growers. However, given the extremely large number of interacting variables that determine berry temperature it is not feasible to independently vary all of these parameters in field experiments. Thus, to study the interactions between these variables that might yield favorable results, Chapter 4 expands the model developed and validated in Chapter 3 by incorporating the effects of shade cloth on berry temperature. The model was used to ultimately predict the efficacy of potential mitigation strategies for high berry temperature. The results of this study provided new insights into the effect of fruit zone shading to control berry temperature for the establishment of new vineyards and targeting the management of existing vineyards.Light interception in plant canopies is most commonly estimated using a simple one dimensional turbid medium model . Inherent in this class of models are assumptions that vegetation is uniformly distributed in space and in many cases that vegetation orientation is uniformly distributed . It is known that these assumptions are violated in a wide range of canopies, as real canopies commonly have heterogeneity at multiple scales and almost always have highly anisotropic leaf angle distributions. However, it is not quantitatively known under what conditions these assumptions become problematic given the difficulty of robustly evaluating model results for a range of canopy architectures. In this study, assumptions of vegetation homogeneity and isotropy were evaluated under clear sky conditions for a range of virtually-generated crop canopies with the aid of a detailed three-dimensional, leaf-resolving radiation model. Results showed that Beer’s law consistently over predicted light interception for all canopy configurations. For canopies where the plant spacing was comparable to the plant height, Beer’s law performed poorly, and over predicted daily intercepted sunlight by up to 115%. For vegetation with a highly anisotropic leaf inclination distribution but a relatively isotropic leaf azimuth distribution, the assumption of canopy isotropy resulted in relatively small errors. However, if leaf elevation and azimuth were both highly anisotropic, the assumption of canopy isotropy could introduce significant errors depending on the orientation of the azimuthal anisotropy with respect to the sun’s path.Solar radiation is a primary driver of most plant biophysical processes, including energy transfer, turbulent transport, evapotranspiration, photosynthesis, and phenology. Fluxes of absorbed radiation in plant canopies have strong gradients in the vertical direction, and potentially in horizontal directions in the case of heterogeneous canopies. Capturing these high gradients through direct measurement is often challenging, and therefore models are frequently used to predict absorbed radiative flux distributions.