Can thromboembolism be the result, rather than the inciting cause, of acute vascular events such as stroke, pulmonary embolism, mesenteric ischemia, and venous thrombosis?: a maladaptation of the prehistoric trauma response

Temporal Trends, Predictors, and Outcomes of Acute Ischemic Stroke in Acute Myocardial Infarction in the United States

Background

There are limited contemporary data prevalence and outcomes of acute ischemic stroke (AIS) complicating acute myocardial infarction (AMI).

Methods and Results

Adult (>18 years) AMI admissions using the National Inpatient Sample database (2000–2017) were evaluated for in‐hospital AIS. Outcomes of interest included in‐hospital mortality, hospitalization costs, length of stay, discharge disposition, and use of tracheostomy and percutaneous endoscopic gastrostomy. The discharge destination was used to classify survivors into good and poor outcomes. Of a total 11 622 528 AMI admissions, 183 896 (1.6%) had concomitant AIS. As compared with 2000, in 2017, AIS rates increased slightly among ST‐segment–elevation AMI (adjusted odds ratio, 1.10 [95% CI, 1.04–1.15]) and decreased in non–ST‐segment–elevation AMI (adjusted odds ratio, 0.47 [95% CI, 0.46–0.49]) admissions (P<0.001). Compared with those without, the AIS cohort was on average older, female, of non‐White race, with greater comorbidities, and higher rates of arrhythmias. The AMI‐AIS admissions received less frequent coronary angiography (46.9% versus 63.8%) and percutaneous coronary intervention (22.7% versus 41.8%) (P<0.001). The AIS cohort had higher in‐hospital mortality (16.4% versus 6.0%; adjusted odds ratio, 1.75 [95% CI, 1.72–1.78]; P<0.001), longer hospital length of stay, higher hospitalization costs, greater use of tracheostomy and percutaneous endoscopic gastrostomy, and less frequent discharges to home (all P<0.001). Among AMI‐AIS survivors (N=153 318), 57.3% had a poor functional outcome at discharge with relatively stable temporal trends.

Conclusions

AIS is associated with significantly higher in‐hospital mortality and poor functional outcomes in AMI admissions.

Transient global amnesia: Minor inconvenience or early warning sign?

Transient global amnesia (TGA) is a clinical diagnosis and is often a diagnosis of exclusion. However, despite the benign nature of this condition, it has been associated with underlying life-threatening medical conditions (e.g., myocardial infarction, dissecting aortic aneurysm, arrhythmias). Our case report highlights the importance of early recognition of those with cardiovascular risk factors who present with acute onset altered mental status to look for underlying medical comorbidities.

Risk stratification, perioperative and periprocedural management of the patient receiving anticoagulant therapy

As a result of the aging US population and the subsequent increase in the prevalence of coronary disease and atrial fibrillation, therapeutic use of anticoagulants has increased. Perioperative and periprocedural management of anticoagulated patients has become routine for anesthesiologists, who frequently mediate communication between the prescribing physician and the surgeon and assess the risks of both thromboembolic complications and hemorrhage. Data from randomized clinical trials on perioperative management of antithrombotic therapy are lacking. Therefore, clinical judgment is typically needed regarding decisions to continue, discontinue, bridge, or resume anticoagulation and regarding the time points when these events should occur in the perioperative period. In this review, we will discuss the most commonly used anticoagulants used in outpatient settings and discuss their management in the perioperative period. Special considerations for regional anesthesia and interventional pain procedures will also be reviewed.

Peripheral to central: Organ interactions in stroke pathophysiology

Stroke is associated with a high risk of disability and mortality, and with the exception of recombinant tissue-type plasminogen activator for acute stroke, most treatments have proven ineffective. Clinical translation of promising experimental therapeutics is limited by inadequate stroke models and a lack of understanding of the mechanisms underlying acute stroke and how they affect outcome. Bidirectional communication between the ischemic brain and peripheral immune system modulates stroke progression and tissue repair, while epidemiological studies have provided evidence of an association between organ dysfunction and stroke risk. This crosstalk can determine the fate of stroke patients and must be taken into consideration when investigating the pathophysiological mechanisms and therapeutic options for stroke. This review summarizes the current evidence for interactions between the brain and other organs in stroke pathophysiology in basic and clinic studies, and discusses the role of these interactions in the progression and outcome of stroke and how they can direct the development of more effective treatment strategies.

Neurologic complications of myocardial infarction

Cardiac disease, in particular coronary artery disease, is the leading cause of mortality in developed nations. Strokes can complicate cardiac disease - either as result of left ventricular dysfunction and associated thrombus formation or of therapy for the cardiac disease. Antiplatelet drugs and anticoagulants routinely used to treat cardiac disease increase the risk for hemorrhagic stroke.

Finding the origin of pulmonary emboli with a total-body magnetic resonance direct thrombus imaging technique

Pulmonary embolism is considered to originate from embolization of a deep-vein thrombosis, resulting in two manifestations of one disease: venous thrombosis. However, in up to 50% of patients with pulmonary embolism no deep-vein thrombosis is found with ultrasonography. An explanation for this low proportion is currently lacking. Other imaging modalities may increase the yield of detection of deep-vein thrombosis in the calf or in the abdominal region. Alternatively, not all pulmonary emboli may originate from deep-vein thromboses in the extremities. We searched for the origin of pulmonary emboli, by performing total-body magnetic resonance imaging-scans to visualize thrombi. Ninety-nine patients with a first pulmonary embolism confirmed by computed tomography underwent a magnetic resonance direct thrombus imaging-scan, a validated technique using endogenous contrast. Additionally, acquired and genetic risk factors were assessed. No thrombus was found in 55 patients, whereas a thrombus was identified in 44 patients. The commonest thrombus location was the lower leg; 12 patients had isolated calf vein thrombosis and five had isolated superficial vein thrombosis. A peripheral thrombus was found by magnetic resonance imaging in less than half of patients with pulmonary embolism. We propose several hypotheses to explain the absence of thrombi, such as a cardiac thrombus origin or embolization of the whole deep-vein thrombus. The possibility that pulmonary embolism arises de novo in the lungs, due to local inflammation-driven coagulation, needs to be considered.

The hegemony of empiricism: The opportunity for theoretical science in medicine

Partly spurred by the rapid emergence of discovery tools, empirical science founded on experimental validation now dominates academic funding, publishing, and recognition while forums for theoretical science have been marginalized. Although this hegemony of empiricism instills useful discipline to the scientific process, it also limits the pace of science to sensor innovation and renders the ontogeny of scientific knowledge path-dependent, concealing potential discontinuities in intellectual trajectories. Theoretical science, founded on intuition, inspiration, and abstraction, can complement empirical science by creating disruptive paradigms that facilitate detection of spurious results and frame new hypotheses. For example, framing the compendium of human diseases as varying manifestations of buffer dysfunctions - insufficient or maladaptive responses to stress - portends new insights into disease mechanisms and treatments. As a specific incarnation of this theory, the "trauma hypothesis" suggests that the coordinated regulation of inflammation, coagulation, vasoconstriction, and fluid retention that evolved as a prehistoric adaptation to predatory stress and environmental injury conspires in modern times to produce acute coronary syndromes, heart failure, renal dysfunction, stroke, and pulmonary embolism. The theory also exposes the paradigmatic flaw behind the half-century detour perfecting balloon-deployed endovascular interventions. As the basis of buffer acquisition shifts from genetic to cognitive, phenoptosis - the theory that adaptive programmed death of organisms yields opportunity to successors - is rendered maladaptive, as an extended lifespan permits more efficient trait acquisition compared with life-death recycling. While forestalling death is a largely unfruitful medical game of "whack-a-mole" today, the recognition that aging and death may be programmed adaptations suggests they may also be amenable to systemic reprogramming. Epitomizing this opportunity are tumor cells, which reprogram themselves to escape their apoptotic fate and assume indefinite persistence. The prevalence and resilience of these cancer cells, and their ability to withstand the protean assaults of toxins, poisons, radiation, and host defenses, presage the potential robustness of life when appropriately programmed. Paradoxical medicine and dynamic range management may represent initial strategies to reprogram the neuroendocrine stress axes to modulate lifespan at the organism level, and many other strategies are anticipated. The key to theoretical science is original insight, but the prevailing pressure to conform to medicine's educational and practice standards dis-incentivizes independent thinking. A scientific future is envisioned when the commoditization of experimental science will enable its outsourcing, liberating health scientists from the tyranny of empiricism to engage in a more balanced process of discovery infused with theoretical considerations.

Pulmonary embolism after brain hemorrhage in a hypertensive patient: the therapeutic dilemma

Massive pulmonary embolism is a life-threatening condition to be treated with anticoagulants or even thrombolytic agents in selected cases. However, these drugs are controindicated after a recent hemorrhagic episode. We report the case of a 46-year-old patient with uncontrolled systemic hypertension who was affected by severe spontaneous cerebral hemorrhage and left hemiparesis. After some days of rehabilitation care he developed sudden dyspnea, tachycardia and hypotension secondary to bilateral pulmonary embolism. Owing to controindication to the use of thrombolytic agents, anticoagulant therapy with high-dose intravenous unfractionated heparin followed by oral warfarin was begun, with a successful and uncomplicated outcome. The therapeutic approach to similar not uncommon cases is debated and some hypotheses are made about the aetiology of pulmonary embolism in these patients.

Negative pressure ventilation via diaphragmatic pacing: a potential gateway for treating systemic dysfunctions

Programmed diaphragmatic pacing using implanted neuromodulators represents an emerging method for providing pulmonary support using negative pressure ventilation. The implantable, rechargeable, programmable and miniaturized nature of diaphragmatic pacers may obviate many of the management issues associated with noninvasive positive pressure ventilation devices. Closed loop systems may facilitate the implementation of diaphragmatic pacing for the treatment of many indications. They may allow for wider adoption of ventilatory support in central sleep apnea and improve quality of life in diseases of chronic hypoventilation, such as amyotrophic lateral sclerosis. In addition, it might alleviate subclinical hypoventilation--a condition that may affect a significant proportion of the aging population. Diaphragmatic pacing could also reduce sympathetic bias, which may contribute to a wide range of diseases associated with autonomic dysfunction.

Environmental discontinuity hypothesis: Buffer dysfunctions as a source of human disease

Adaptive physiologic buffers enable organisms to respond to environmental variation with appropriate plasticity. Modern humans have substantially remodeled their environment such that many interactions with the environment have become relatively discontinuous functions compared to the past. Examples include sunlight, temperature, and altitude. We propose that environmental discontinuity represents a Darwinian maladaptation and may promote disease by inducing buffer dysfunctions. Skin pigmentation is an adaptive, dynamic buffer that normalizes sunlight exposure to balance the potential harm of damaging rays with the importance of sunlight in driving systemic biologic functions such as melatonin and vitamin D. Due to lifestyle characteristics such as indoor-outdoor living, well-intended sun-avoidance campaigns, and inhomogeneous use of apparel and sunblock techniques, modern humans increasingly experience sunlight variation as a discontinuous function. The resulting skin pigmentation buffer dysfunction may promote diseases associated with over- or under-exposure to sunlight, the most striking example being melanoma. In addition to promoting discontinuity of sunlight exposure, sun-avoidance campaigns may undermine sun-dependent biologic pathways such as melatonin and vitamin D that appear to protect against cancer. These issues may partly explain the rise in melanoma rates despite the implementation of sun-avoidance campaigns. Also discussed is the potential role that discontinuous temperature variation associated with modern lifestyles plays in diseases such as viral infection, heart failure, and acute coronary syndromes. Acute discontinuous changes in pressure and oxygen levels related to air travel may contribute to autonomic dysfunction, venous thromboembolism, and viral infections. Therapeutic implications are discussed.

The link between carotid artery disease and ischemic stroke may be partially attributable to autonomic dysfunction and failure of cerebrovascular autoregulation triggered by Darwinian maladaptation of the carotid baroreceptors and chemoreceptors

Carotid artery stenosis is generally thought to induce stroke by either compromising cerebral perfusion or inciting embolic phenomena. Carotid baroreceptors and chemoreceptors are vital adaptations for cerebrovascular autoregulation that can behave mal-adaptively in the setting of modern diseases such as atherosclerosis. We hypothesize that acute cerebrovascular events may be partially attributable to autonomic dysfunction and cerebrovascular autoregulatory failure secondary to carotid sensor maladaptations. Specifically, we propose that atherosclerotic disease at the carotid bifurcation can interfere with baroreceptor and chemoreceptor function by buffering against accurate detection of physical and chemical parameters. Misperceptions of hypoxia and hypotension can trigger sympathetic bias and autonomic dysfunction which perturb cerebrovascular autoregulation and vasomotor tone, thereby compromising cerebral perfusion. The preferential association of strokes with morning arousal, stress, acute physical activity, winter months, illness, and older age may relate to this phenomenon. Sympathetic bias promotes inflammation and coagulation, a link likely forged during prehistoric evolution when trauma represented a more significant factor in natural selection. In the setting of carotid sensor dysfunction, the resulting inflammation and coagulation can promote acute cardiovascular events. The ensuing cerebral ischemia can induce further derangement of cerebrovascular autoregulation and upregulate adrenergia, inflammation, and coagulation in a feed-forward manner. Inflammation and coagulation can also exacerbate carotid sensor dysfunction by iteratively worsening atherosclerosis. Angioplasty, stenting, and endarterectomy may inadvertently cause acute and chronic carotid sensor dysfunction through manipulation, material interposition, and balloon-induced baroreceptor injury. Acute strokes during these procedures may result from carotid sensor dysfunction rather than embolization. Carotid body and sinus electro-modulation and non-balloon atherectomy represent new methods to prevent or treat cerebrovascular events. Pharmacologic modulation of autonomic balance, such as adrenergic blockade, long presumed contraindicated due to risk of cerebral hypoperfusion, may counter-intuitively offer benefit during acute strokes. Novel diagnostic paradigms may include functional analysis of carotid sensors as well as measurement of the anatomic thickness of calcified and non-calcified plaque near the carotid body. Carotid sensor dysfunction may be a source of systemic sympathetic bias and autonomic dysfunction observed during aging and, by association, many of the ailments associated with senescence. Modulation of carotid sensors may yield pervasive health benefits beyond those found by treating cerebrovascular disease.

Peripheral arterial disease: a manifestation of evolutionary dislocation and feed-forward dysfunction

Peripheral arterial disease in the legs represents a subset of atherosclerosis that manifests a particularly sinister profile. A predominance of sympathetic activity in the periphery favors the development of neurogenic atherosclerosis. Atherosclerosis may then produce flow derangements and decreased physical activity that serves to escalate sympathetic bias in a vicious cycle. Restoration of normal flow in peripheral arterial disease may not only produce local benefit due to improved perfusion, but also represent a gateway to correcting many systemic conditions that may at first glance appear unrelated but share a common etiology of autonomic dysfunction, such as gout, acute coronary syndromes, stroke, sleep apnea, arrhythmias, depression, erectile dysfunction, inflammation, hypercoagulability, sleep disorders, bowel dysfunction, renal failure, and aging.

Osteoarthritis: an example of phenoptosis through autonomic dysfunction?

Phenoptosis, the programmed death of organisms akin to cellular apoptosis, constitutes a type of Darwinian selection that enhances inclusive fitness. It provides a means by which senescent and pre-senescent members can self-terminate if they have incurred sufficient cumulative stress such that their continued survival detracts from inclusive fitness. Sepsis, vascular disease, menopause, cancer, and aging all represent examples of phenoptosis at work. We previously proposed that feed-forward autonomic dysfunction fundamentally drives phenoptosis in all its guises. Accordingly, we now postulate that osteoarthritis defines a type of biomechanical phenoptosis, mediated by feed-forward autonomic dysfunction, and manifested through joint destruction associated with fitness disadvantages. Biomechanical capability plays a significant role in evolutionary fitness, and sustained joint insults such as immobility or undue biomechanical stress may serve as proxies for inferior fitness. By both hindering an individual's ability to compete for energy and increasing that individual's vulnerability to predation, feed-forward joint destruction may facilitate adaptive phenoptosis among impaired or senile members. Empirical data suggests that contrary to common belief, heavy joint use does not necessarily cause osteoarthritis, whereas immobility and neuropathy can predispose to the condition. From a Darwinian perspective, another process mediated by sympathetic activity, the alarm cry of attacked prey, simultaneously promotes the escape of kin while attracting predators and scavengers. By effectively enabling the martyrdom of biomechanically-challenged individuals, osteoarthritis may serve to optimize system energy efficiency in a similar fashion. This framework may generalize to other situations where regenerative capacity dissipates in conjunction with maturation, typically leading to fibrosis. By allowing environmental pressure to sort the phenotypes, imperfect repair mechanisms may accelerate adaptation and optimize long-term inclusive fitness for all individuals. As the basis of competition shifts from biomechanical to cognitive skills, and as novel triggers for physical stress emerge, osteoarthritis may now represent a modern maladaptation.

Ischemic Stroke Following Multiple Traumas in a Child: A Case Report

Stroke is an uncommon disorder in children but an increasingly recognized cause of disability. Acute stroke may be attributable to trauma, but this topic is seldom discussed. In limited reports, most ischemic strokes following trauma were detected after a considerable delay. Early recognition of stroke following trauma might reduce secondary neurologic complications. We report a case of posterior cerebral artery area infarct following multiple traumas in a child. A comprehensive etiologic survey was undertaken and discussed. Although the definite pathogenesis is still unclear, adequate, individualized, and uncomplicated management can significantly affect the outcome.

Opening the floodgates: benign prostatic hyperplasia may represent another disease in the compendium of ailments caused by the global sympathetic bias that emerges with aging

We have previously posited that the global sympathetic bias that emerges with aging may constitute the common etiologic thread that links a myriad of ailments associated with aging. Recent data suggests that benign prostatic hyperplasia (BPH) and associated lower urinary tract symptoms (LUTS) may also be caused by sympathetic bias as an independent etiology from androgen dysfunction. The association of BPH with heart disease, independent of other variables, supports the view that both entities represent downstream manifestations of global sympathetic bias. The risk for development of BPH increases with caffeine intake and decreases with alcohol consumption, factors which wield opposing effects on autonomic balance. Heavy smoking, which induces chronic sympathetic bias, also increases the risk of BPH, a link also previously attributed to hormonal alterations. Sympathetic dysfunction appears to have a mitogenic effect on the prostate. The high prevalence of prostate cancer, a condition detected in the autopsy of many elderly men, may arise from this activity combined with a Th2 shift induced by sympathetic bias, leading to decreased cancer surveillance by the immune system. Exercise may improve BPH by restoring autonomic balance and normalizing the sympathovagal ratio. The benefits of alpha-adrenergic blockers on BPH, generally felt to achieve symptomatic relief afforded by bladder wall and sphincter remodeling, may independently exert a direct effect on prostate growth and enlargement. Sympathetic bias may play a role in adaptive enlargement of other organs such as the salivary glands, heart, liver, spleen, and skeletal muscles in response to stress. We envision novel pharmacologic and device-based neuromodulation therapies for BPH and related urologic dysfunctions based on these principles.

A paradigm for viewing biologic systems as scale-free networks based on energy efficiency: Implications for present therapies and the future of evolution

A network constitutes an abstract description of the relationships among entities, respectively termed links and nodes. If a power law describes the probability distribution of the number of links per node, the network is said to be scale-free. Scale-free networks feature link clustering around certain hubs based on preferential attachments that emerge due either to merit or legacy. Biologic systems ranging from sub-atomic to ecosystems represent scale-free networks in which energy efficiency forms the basis of preferential attachments. This paradigm engenders a novel scale-free network theory of evolution based on energy efficiency. As environmental flux induces fitness dislocations and compels a new meritocracy, new merit-based hubs emerge, previously merit-based hubs become legacy hubs, and network recalibration occurs to achieve system optimization. To date, Darwinian evolution, characterized by innovation sampling, variation, and selection through filtered termination, has enabled biologic progress through optimization of energy efficiency. However, as humans remodel their environment, increasing the level of unanticipated fitness dislocations and inducing evolutionary stress, the tendency of networks to exhibit inertia and retain legacy hubs engender maladaptations. Many modern diseases may fundamentally derive from these evolutionary displacements. Death itself may constitute a programmed adaptation, terminating individuals who represent legacy hubs and recalibrating the network. As memes replace genes as the basis of innovation, death itself has become a legacy hub. Post-Darwinian evolution may favor indefinite persistence to optimize energy efficiency. We describe strategies to reprogram or decommission legacy hubs that participate in human disease and death.

Contrast nephropathy may be partly mediated by autonomic dysfunction: renal failure considered as a modern maladaptation of the prehistoric trauma response

The mechanism behind iodinated radiocontrast nephropathy remains elusive. Direct oxidative damage is the prevailing hypothesis, but the apparent protective effect of iodine against oxidation contradicts this view. We propose that autonomic dysfunction participates in the pathogenesis of radiocontrast nephropathy and may account for other contrast-associated reactions previously attributed to allergy. Iodine, through its effects on thyroid function and chemoreceptor response to metabolic acidosis, may induce hyperadrenergia and consequently diminish renovascular flow and urine output. The renal response to adrenergia likely served an adaptive function during prehistoric evolution when trauma was a dominant source of hypovolemia and adrenergia, but the response may behave maladaptively today as evolutionarily nai ve triggers for adrenergia have emerged. Autonomic dysfunction can further impair renal function by deranging renovascular autoregulation and inducing oxidative reperfusion injury as a secondary phenomenon. Many other causes of acute renal failure such as drug toxicity, surgery, hospitalization, and diabetes may operate through hyperadrenergia, impaired renovascular autoregulation, and oxidative reperfusion injury. Dialysis, a volume reduction therapy for renal failure, can counterintuitively worsen renal dysfunction by exacerbating adrenergia, which may explain its association with accelerated atherosclerosis, inflammation, and cancer. Other examples of vicious cycles that perpetuate renal dysfunction may include renal artery stenosis, carotid stenosis, and atherosclerosis as well as the cardio-renal, hepato-renal, and pulmonary-renal syndromes. The benefits of hydration and bicarbonate in protecting renal function may operate in part through baroreceptor- and chemoreceptor-mediated reduction of sympathovagal ratio, respectively. New treatment paradigms for renal failure including pharmacologic and electro-mechanical therapies are envisioned based on autonomic remodeling, reduced sympathovagal ratio, and neuromodulation of pathways typically associated with trauma such as renin, angiotensin, vasopressin, and aldosterone.

Adventitial dysfunction: an evolutionary model for understanding atherosclerosis

Endothelial and smooth muscle dysfunctions are widely implicated in the pathogenesis of atherosclerosis. Modern mechanical and pharmacologic treatments aim to remodel abnormalities of the vessel intima and media. We hypothesize that adventitial dysfunction comprises the dominant source of atherosclerosis by originating many endothelial and smooth muscle abnormalities. The autonomic nervous system innervates the adventitia, and autonomic dysfunction induces many end-organ dysfunctions including inflammation and thrombosis. The link between diabetes and atherosclerosis may operate through adventitial autonomic neuropathy. Smoking may promote atherosclerosis by inducing adventitial autonomic dysfunction related to nicotine-mediated compensatory upregulation of sympathetic bias independent of endothelial injury induced by purported tobacco toxins. While hypertension is thought to cause atherosclerosis, the two conditions may instead represent independent consequences of autonomic dysfunction. The link between aging and atherosclerosis may operate through adventitial dysfunction induced by autonomic dysregulations. Exercise may ameliorate atherosclerosis by restoring adventitial autonomic function, thereby normalizing adventitial regulation of medial and intimal biology. Feed-forward adventitial vascular baroreceptor and chemoreceptor dysregulation may further exacerbate atherosclerosis as intimal plaque interferes with these sensors. Since penetrating external physical injury likely represented a dominant selective force during evolution, the adventitia may be preferentially equipped with sensors and response systems for vessel trauma. The convergent response of adrenergia, inflammation, and coagulation, which is adaptive for physical trauma, may be maladaptive today when different stressors trigger the cascade. Endoluminal therapies including atherectomy, angioplasty, and stent deployment involve balloon expansion that traumatizes all layers of the vessel wall. These interventions may paradoxically reinitiate the cascade of atherogenesis that begins with adventitial dysfunction and leads to restenosis. Methods to reduce adventitial trauma, a maladaptive trigger of adventitial dysfunction, may reduce the risk of restenosis. We envision novel mechanical and biopharmaceutical solutions that target the adventitia to prevent or treat atherosclerosis including novel drug delivery strategies, exo-stents that wrap vessels, and neuromodulation of vessels.

The smoking gun: many conditions associated with tobacco exposure may be attributable to paradoxical compensatory autonomic responses to nicotine

Tobacco exposure is implicated in many illnesses such as cardiovascular disease and cancer, but the mechanisms underlying these associations are poorly understood. The mechanisms by which tobacco induces pro-sympathetic and pro-inflammatory changes also remain elusive. Some studies have attributed these changes to the direct effects of nicotine, but such findings run counter to the pro-vagal, anti-inflammatory nature of the nicotinic pathway. We hypothesize that the illnesses associated with smoking may be partly attributable to autonomic dysfunction, sympathetic bias, and T helper (Th)2 inflammation induced by a paradoxical compensatory response to intermittent nicotinic exposure. The confusion of interpreting the adrenergia and inflammation associated with nicotine as a primary response instead of a secondary compensation may be explained by the unusually rapid absorption, action, and serum elimination of nicotine. Given the fast action and clearance of nicotine, even heavy smokers spend large portions of the day and the entire night in nicotine withdrawal, at which time rebound sympathetic bias may manifest as a result of desensitization of nicotinic receptors. This may help reconcile why the features observed in smokers such as tachycardia, hypertension, inflammation, insomnia, and anxiety, which are perhaps mistakenly attributed to the direct action of nicotine, are identical to those seen during acute nicotine withdrawal after smoking cessation. On the other hand, delayed responses to cessation of smoking such as weight gain and increased heart rate variability are compatible with reduced sympathovagal ratio and resensitization of nicotinic receptors. Sympathetic bias and the associated Th2 inflammation underlie many systemic diseases. Tobacco-related cancers may be partly attributable to immunomodulatory properties of chronic nicotine exposure by dampening Th1 immunity and enabling tumoral evasion of immune surveillance. Other conditions associated with tobacco exposure may also operate through similar autonomic and immune dysfunctions. Therapeutic implications are discussed.

Can chronic use of anti-inflammatory agents paradoxically promote chronic inflammation through compensatory host response?

A higher relative risk of thrombotic cardiovascular complications has recently emerged in studies evaluating the use of non-steroidal anti-inflammatory drugs (NSAIDs) such as rofecoxib, celecoxib, and naproxen. Direct pro-thrombotic effects of selective cyclooxygenase-2 inhibition were originally speculated to be the potential mechanism behind these results, but this proposal fails to explain the pro-thrombotic effects of non-selective NSAIDs. We hypothesize that the paradoxical pro-inflammatory, pro-thrombotic effects associated with chronic use of anti-inflammatory agents are attributable to compensatory host response rather than direct effects of the drugs. Chronic pharmacologic inhibition of inflammation may induce physiologic dependence, and cessation of therapy has been shown to produce rebound effects in aspirin, statins, and other immunomodulatory agents. By down-regulating inflammatory pathways in a pulsatile fashion, chronic use of NSAIDs may promote compensatory up-regulation of these same pathways and shift the host baseline equilibrium towards an inflammatory state. The host may be susceptible to inflammation between intermittent doses and after withdrawal of therapy. Inflammation is a promoter of adrenergia and thrombosis, and the constellation of these effects may predispose to excess risk of acute cardiovascular events.

Integrating the theories of Darwin and Bernoulli: Maladaptive baroreceptor network dysfunction may explain the pathogenesis of aortic aneurysms

Current treatment options for aortic aneurysms are suboptimal and their pathogenic mechanisms remain unclear. We propose the existence of a coordinated multi-node baroreceptor network that measures pressures at all vascular bifurcations and enables system-wide hemodynamic coordination and vasomotor regulation, in accordance with the principle of Bernoulli. While the presence of baroreceptors at bifurcations remains unknown, behavior at the level of systems predicts their existence, possibly as glomus cell derivatives. We propose that pressure misregistration among sensor nodes at different vascular bifurcations can precipitate feed-forward dysfunctions that promote thrombosis, inflammation, and vasomotor dysregulation resulting in aneurysm formation. One example of this phenomenon is aortic aneurysm, which is currently attributed to focal anatomic defects. As plaque builds in the infrarenal aorta, the increased blood velocity through this segment can widen the difference between pressures sensed at the iliac and the renal artery bifurcations. Due to the Bernoulli effect, this change creates an incorrect impression of reduced dynamic pressure at the kidneys. The erroneous perception of hypovolemia can induce a pernicious cycle of maladaptive adrenergia and associated coagulation and thrombosis, particularly in the infrarenal aortic segment as the body attempts to normalize renal perfusion. Atherosclerosis can further exacerbate baroreceptor dysfunction by interfering with sensor biology in feed-forward fashion. Hypertension may be a consequence as well as a source of atherosclerosis and aneurysm. The described system may have evolved when trauma-related hypovolemia was a far more prevalent driver of natural selection but may be rendered maladaptive in the setting of modern stressors. Failure to address these factors may explain the suboptimal long-term outcomes with current surgical and endovascular treatments for aneurysms. Implications for other potential sensor networks including chemoreceptors and lymphoid tissues at bifurcating biologic branch-points such as vessels, airways, nerves, lymphatics, and ducts are discussed. Our framework may also provide a new basis for understanding thoracic aneurysm, renovascular dysfunctions, coronary artery disease, carotid artery disease, pulmonary embolism, portal hypertension, venous thrombosis, biliary disease, pancreatic disease, and neurologic disease. Novel treatment paradigms based on drugs or interconnected networks of devices that modulate sensors are envisioned. Improving the interface between sensors and their substrate information by techniques such as minimally traumatic atherectomy or thrombectomy may also restore appropriate sensor function. Lessons learned from bifurcation sensors and their potential maladaptations may generalize to other types of branching systems including botany, civil engineering, and Pitot tube aeronautics.