Clinical significance of acute neurohormonal response after levosimendan treatment.
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Biomedical subjects
George Louridas
Publications and source records attributed to George Louridas.
Parathyroid hormone-related protein is reduced in severe chronic heart failure.
In the cardiovascular system, parathyroid hormone-related peptide (PTHrP) is expressed in various cells such as cardiac vascular smooth muscle cells, coronary endothelial cells and cardiomyocytes and acts as an autocrine/paracrine substance. We compared PTHrP levels in 35 consecutive patients with severe CHF (33 male, mean age 66.2 +/- 8.9 years) with 26 normal controls (24 male, mean age 63.1 +/- 8.6 years). PTHrP levels were reduced in severe CHF patients (11.10 +/- 1.37 fmol/ml) compared with the controls (20.62 +/- 3.30 fmol/ml, p = 0.005). PTHrP values decreased as a function of New York Heart Association classification. These results suggest that PTHrP levels decrease in proportion to the severity of heart failure and could potentially be used to monitor progression of disease non-invasively.
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A computational model to predict aortic wall stresses in patients with systolic arterial hypertension.
Computational cardiovascular mechanics has allowed scientists to create complex 3D models for the simulation of cardiovascular problems. Mechanical stress plays a crucial role in the function of the cardiovascular system; stress analysis is a useful tool for the understanding of vascular pathophysiology. By using the spiral CT imaging and computational structural analysis, we present a noninvasive method of wall stress analysis in the normal aorta. The aortic segment was extended from the origin of the inferior mesenteric artery to the aortic bifurcation. The length of this segment was 12 cm, while the maximum transverse diameter was 2.075+/-0.129 cm. A 3D aortic model was constructed based on the CT scan images. The aorta was assumed to have a uniform wall thickness of 1.5mm. The generated unstructured grid, which was used for the structural analysis, consisted of 14,440 hexahedral elements. The wall material was assumed to be hyperelastic, homogeneous, isotropic and nearly incompressible (Poisson ratio=0.45). According to experimental studies, the Young modulus of aortic wall was set equal to 4.66 MPa. The shear stress induced by the blood flow was neglected. A finite-element static structural analysis was performed. Three different cases were examined applying constant intraluminal systolic blood pressures of 120, 180 and 240 mmHg, respectively. The von Mises stress distribution and the displacements of the aortic wall were calculated. Peak wall stress for the normal load case of 120 mmHg was 22.5 N/cm2, while the max displacement was 0.44 mm. The case with the intraluminal pressure of 180 mmHg resulted into peak wall stress of 32 N/cm2 with max displacement 0.59 mm, while for 240 mmHg was 40.6N/cm2, max displacement 0.72 mm. The rise in blood pressure caused all stresses to increase. The pattern of stress distribution and the orientation of the stress were similar for all test cases. A quantitative evaluation of the aortic wall stresses under systolic hypertension is presented. The calculated values of peak wall stress are far lower to those of failure strength of healthy aortic wall specimens estimated by ex vivo mechanical testing (121.0 N/cm2). Our values are consistent with prior stress values predicted by experimental studies. The described methodology offers a significant advancement in incorporating biomechanical principles in the clinical assessment of hypertensive patients with normal or aneurysmatic aortas and can be applied in a patient-specific basis in both conditions in order to detect the vulnerable high stressed regions and the resultant risk of aortic dissection or rupture. We hypothesize that this could assist in deciding the timing of surgical intervention, especially in high-risk patients with abdominal aortic aneurysms.
Aorta↗
Risk factors and prevalence of perioperative cognitive dysfunction in abdominal aneurysm patients.
BACKGROUND: Perioperative delirium is common in high-risk surgery and is associated with age, education, preoperative cognitive functioning, pre-existing medical conditions, and postoperative complications. We investigated these factors as well as lifestyle and demographic variables by using cognitive measures that were more sensitive than those used in previous studies. METHODS: Extensive medical and demographic data were collected on 102 patients between 41 and 88 years of age to identify comorbidities and lifestyle considerations preoperatively. Elective abdominal aortic aneurysm surgery was performed under combined general/epidural anesthesia with postoperative epidural analgesia. A battery of sensitive, cognitive measures was administered preoperatively, at the time of discharge from hospital, and 3 months postoperatively. Symptoms of delirium were assessed during the first 6 postoperative days using Diagnostic and Statistical Manual of Mental Disorders-4th Edition criteria. Intraoperative and postoperative data, including medications, vital signs, conduct of the surgery and anesthesia, complications, and details of pain control, were collected. RESULTS: Delirium occurred in 33% of the patients during the first 6 days after surgery. Longer duration of delirium was related to lower education, preoperative depression, and greater preoperative psychoactive medication use. Characteristics of the surgery and hospital stay were unrelated to the development of delirium. Patients who were diagnosed with delirium had lower cognitive scores during each of the three assessment periods, even when controlling for age and education. Logistic regression analysis indicated that the most powerful preoperative predictors of delirium were number of pack years smoked (P = .001), mental status scores (P = .003), and number of psychoactive medications (P = .005). CONCLUSION: A significant proportion of patients undergoing elective abdominal aortic aneurysm repair are susceptible to the development of delirium and are at risk for cognitive dysfunction after surgery. Our findings have implications for promoting long-term lifestyle changes, including smoking cessation and improved management of mental health as risk-reduction strategies.
Adult↗
The Citizen Health System (CHS): a modular medical contact center providing quality telemedicine services.
In the context of the Citizen Health System (CHS) project, a modular Medical Contact Center (MCC) was developed, which can be used in the monitoring, treatment, and management of chronically ill patients at home, such as diabetic or congestive heart failure patients. The virtue of the CHS contact center is that, using any type of communication and telematics technology, it is able to provide timely and preventive prompting to the patients, thus, achieving better disease management. In this paper, we present the structure of the CHS system, describing the modules that enable its flexible and extensible architecture. It is shown, through specific examples, how quality of healthcare delivery can be increased by using such a system.
Database Management Systems↗
Inappropriate detection and therapy from an implantable cardioverter defibrillator due to atrial undersensing.
We present a case of inappropriate detection and therapy in a patient with an implantable cardioverter defibrillator. The device interpreted a supraventricular tachycardia as ventricular tachycardia due to unsensed P waves as a result of a relatively high level of atrial sensitivity setting. Subsequently, inappropriate therapy was delivered. The problem was resolved by decreasing the atrial sensitivity value.
Defibrillators, Implantable↗
Acute left main occlusion during percutaneous coronary intervention associated with heparin induced thrombocytopenia with thrombosis syndrome.
A 76-year-old male was admitted with Braunwald IIIB unstable angina and treated with intravenous heparin. Coronary angiography 20 days later revealed a severe stenosis in the left circumflex artery. During coronary angioplasty thrombus developed in the circumflex artery, extended in the left main and lead to its occlusion. Normal left coronary artery patency and flow were achieved after intracoronary and intravenous administration of abciximab, and multiple stenting. Platelet-count decrease and an ELISA assay documented the presence of heparin-induced thrombocytopenia with thrombosis syndrome (HITTS). HITTS should be suspected after acute thrombus formation during coronary angioplasty.
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Rotational ablation of an unexpandable sirolimus-eluting stent.
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Management of carotid artery stenosis. Update for family physicians.
OBJECTIVE: To clarify the definition of carotid artery diseases, the appropriateness of screening for disease, investigation and management of patients presenting with transient ischemic attacks, and management of asymptomatic carotid bruits. SOURCES OF INFORMATION MEDLINE: was searched using the terms carotid endarterectomy, carotid disease, and carotid stenosis. Most studies offer level II or III evidence. Consensus statements and guidelines from various neurovascular societies were also consulted. MAIN MESSAGE: Patients with symptoms of hemispheric transient ischemic attacks associated with >70% stenosis of the internal carotid artery are at highest risk of major stroke or death. Risk is greatest within 48 hours of symptom onset; patients should have urgent evaluation by a vascular surgeon for consideration of carotid endarterectomy (CEA). Patients with 50% to 69% stenosis might benefit from urgent surgical intervention depending on clinical features and associated comorbidity. Patients with <50% stenosis do not benefit from surgery. Asymptomatic patients with >60% stenosis should be considered for elective CEA. CONCLUSION: Symptomatic carotid artery syndromes need urgent carotid duplex evaluation to determine the need for urgent surgery. Those with the greatest degree of stenosis derive the greatest benefit from timely CEA.
Algorithms↗
Variable ventilation improves perioperative lung function in patients undergoing abdominal aortic aneurysmectomy.
BACKGROUND: Optimizing perioperative mechanical ventilation remains a significant clinical challenge. Experimental models indicate that "noisy" or variable ventilation (VV)--return of physiologic variability to respiratory rate and tidal volume--improves lung function compared with monotonous control mode ventilation (CV). VV was compared with CV in patients undergoing abdominal aortic aneurysmectomy, a patient group known to be at risk of deteriorating lung function perioperatively. METHODS: After baseline measurements under general anesthesia (CV with a tidal volume of 10 ml/kg and a respiratory rate of 10 breaths/min), patients were randomized to continue CV or switch to VV (computer control of the ventilator at the same minute ventilation but with 376 combinations of respiratory rate and tidal volume). Lung function was measured hourly for the next 6 h during surgery and recovery. RESULTS: Forty-one patients for aneurysmectomy were studied. The characteristics of the patients in the two groups were similar. Repeated-measures analysis of variance (group x time interaction) revealed greater arterial oxygen partial pressure (P = 0.011), lower arterial carbon dioxide partial pressure (P = 0.012), lower dead space ventilation (P = 0.011), increased compliance (P = 0.049), and lower mean peak inspiratory pressure (P = 0.013) with VV. CONCLUSIONS: The VV mode of ventilation significantly improved lung function over CV in patients undergoing abdominal aortic aneurysmectomy.
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Inappropriate ICD therapy due to electrical interference: external alternating current leakage.
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Can P wave wavelet analysis predict atrial fibrillation after coronary artery bypass grafting?
The purpose of this study was the evaluation of Morlet wavelet analysis of the P wave as a means of predicting the development of atrial fibrillation (AF) in patients who undergo coronary artery bypass grafting (CABG). The P wave was analyzed using the Morlet wavelet in 50 patients who underwent successful CABG. Group A consisted of 17 patients, 12 men and 5 women, of mean age 66.9 +/- 5.9 years, who developed AF postoperatively. Group B consisted of 33 patients, 29 men and 4 women, mean age 62.4 +/- 7.8 years, who remained arrhythmid-free. Using custom-designed software, P wave duration and wavelet parameters expressing the mean and maximum energy of the P wave were calculated from 3-channel digital recordings derived from orthogonal ECG leads (X, Y, and Z), and the vector magnitude (VM) was determined in each of 3 frequency bands (200-160 Hz, 150-100 Hz and 90-50 Hz). Univariate logistic-regression analysis identified a history of hypertension, the mean and maximum energies in all frequency bands along the Z axis, the mean and maximum energies (expressed by the VM) in the 200-160 Hz frequency band, and the mean energy in the 150-100 Hz frequency band along the Y axis as predictors for post-CABG AF. Multivariate analysis identified hypertension, ejection fraction, and the maximum energies in the 90-50 Hz frequency band along the Z and composite-vector axes as independent predictors. This multivariate model had a sensitivity of 91% and a specificity of 65%. We conclude that the Morlet wavelet analysis of the P wave is a very sensitive method of identifying patients who are likely to develop AF after CABG. The occurrence of post-CABG AF can be explained by a different activation pattern along the Z axis.
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Steal syndrome complicating upper extremity hemoaccess procedures: incidence and risk factors.
INTRODUCTION: Steal syndrome is a potentially grave complication of upper extremity hemoaccess (HA) in patients with renal failure. To determine the incidence and risk factors for steal in these patients at the St. Boniface Hospital, Winnipeg, a tertiary care centre for vascular surgery and dialysis, we reviewed data from patients requiring hemodialysis between September 1986 and July 2000. PATIENTS AND METHODS: We excluded all venous catheter and lower extremity procedures. There remained 325 upper extremity procedures in 217 patients. Data were collected from the patients' charts or by interview. First by univariate analysis and then by multivariate analysis for independent risk factors, we studied the effect on the development of steal of age, sex, race diabetes mellitus, hypertension, coronary artery disease or cerebrovascular disease, smoking, proximal procedures based on the brachial artery, distal procedures based on the radial artery, the use of prosthetic graft material and the creation of autologous fistulas. RESULTS: The incidence of steal was 6.2%. The significant independent risk factors were diabetes mellitus (odds ratio [OR] 5.00, 95% confidence interval [CI] 1.39-18.08, p = 0.01) and Aboriginal race (OR 3.59, 95% CI 1.07-12.04, p = 0.04). An increasing risk for each year of advancing age at the time of procedure was suggested but was not significant (OR 1.04, 95% CI 1.00-1.09 p = 0.07). CONCLUSIONS: Patients who are diabetic or Aboriginal are at increased risk for steal with upper extremity HA procedures. This knowledge can guide discussion of dialysis options and informed consent. If upper extremity HA procedures are undertaken in patients at risk, they should be closely monitored and early intervention applied if necessary.
Adolescent↗
N-terminal pro-brain natriuretic peptide levels are elevated in patients with acute ischemic stroke.
Brain natriuretic peptide (BNP) is a counterregulatory hormone released by the ventricles of the heart. Its main actions are natriuresis and vasodilation. The authors studied N-terminal pro-brain natriuretic peptide (NT-proBNP) levels soon after an acute ischemic stroke. They compared plasma NT-proBNP concentrations in 30 patients with an acute ischemic stroke with those of 30 controls. The 2 groups were adjusted for age and gender, and there were no significant differences in vascular risk factors and left ventricular systolic and diastolic function. Venous samples were collected within the first 11.8 +/-1.2 hours after the onset of symptoms and again on day 6. Brain computed tomography/magnetic resonance imaging (CT/MRI) was performed on the same days (day 0 and day 6) in order to assess the site (carotid or vertebrobasilar), cause (atherothrombotic, cardioembolic, or lacunar), and size (large, medium, or small) of the brain infarct. NT-proBNP levels were elevated in patients with acute stroke (129.9 +/-9.9 fmol/mL) compared with the controls (90.8 +/-6.3 fmol/mL, p <0.05). These levels remained elevated at day 6 (113.5 +/-13.0 fmol/mL). NT-proBNP at admission was significantly higher in cardioembolic compared with atherothrombotic infarctions. There was no correlation between circulating NT-proBNP and stroke topography, infarct size, or severity as assessed by the National Institutes of Health Stroke Scale (NIHSS) at any of the 2 time points (admission and day 6). NT-proBNP levels were raised in patients with acute ischemic stroke; this effect persisted until day 6. The authors suggest that neurohumoral activation occurs in patients with acute ischemic stroke, either reflecting a counterbalancing vasodilating response to the cerebral ischemia or direct myocardial dysfunction.
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