Robust explicit estimators using the power-weighted repeated medians.

This paper consists of two parts. The first part of the paper is to propose an explicit robust estimation method for the regression coefficients in simple linear regression based on the power-weighted repeated medians technique that has a tuning constant for dealing with the trade-offs between efficiency and robustness. We then investigate the lower and upper bounds of the finite-sample breakdown point of the proposed method. The second part of the paper is to show that based on the linearization of the cumulative distribution function, the proposed method can be applied to obtain robust parameter estimators for the Weibull and Birnbaum-Saunders distributions that are commonly used in both reliability and survival analysis. Numerical studies demonstrate that the proposed method performs well in a manner that is approximately comparable with the ordinary least squares method, whereas it is far superior in the presence of data contamination that occurs frequently in practice.

Candesartan and carvedilol for primary prevention of subclinical cardiotoxicity in breast cancer patients without a cardiovascular risk treated with doxorubicin.

BACKGROUND: There is no proven primary preventive strategy for doxorubicin-induced subclinical cardiotoxicity (DISC), especially among patients without a cardiovascular (CV) risk. We investigated the primary preventive effect on DISC of the concomitant use of angiotensin receptor blockers (ARBs) or beta-blockers (BBs), especially among breast cancer patients without a CV risk. METHODS: A total of 385 patients who were scheduled for doxorubicin chemotherapy were screened. Among them, 195 patients of the study populations were included and were randomly divided into two groups [candesartan 4 mg q.d. vs. carvedilol 3.125 mg q.d.] and patients who were unwilling to take one of the medications were evaluated as controls. The primary outcomes were the incidence of early DISC (DISC developing within 6 months after chemotherapy), and late DISC (DISC developing only at least 12 months after chemotherapy). RESULT: Compared with the control group (8 out of 43 patients (18.6%)), only the candesartan group (4 out of 82 patients (4.9%)) showed a significantly lower incidence of early DISC (p = 0.022). Compared with the control group, the candesartan group demonstrated a significantly reduced decrease in left ventricular ejection fraction (LVEF) throughout the study period [-1.0% vs. -3.00 (p < 0.001) at the first follow-up, -1.10% vs. -3.40(p = 0.009) at the second follow-up]. CONCLUSIONS: Among breast cancer patients without a CV risk treated with doxorubicin-containing chemotherapy, subclinical cardiotoxicity is prevalent and concomitant administration of low-dose candesartan might be effective to prevent an early decrease in LVEF. Further large-scale, randomized controlled trials will be needed to confirm our findings.

Load-Sharing Model under Lindley Distribution and Its Parameter Estimation Using the Expectation-Maximization Algorithm.

A load-sharing system is defined as a parallel system whose load will be redistributed to its surviving components as each of the components fails in the system. Our focus is on making statistical inference of the parameters associated with the lifetime distribution of each component in the system. In this paper, we introduce a methodology which integrates the conventional procedure under the assumption of the load-sharing system being made up of fundamental hypothetical latent random variables. We then develop an expectation maximization algorithm for performing the maximum likelihood estimation of the system with Lindley-distributed component lifetimes. We adopt several standard simulation techniques to compare the performance of the proposed methodology with the Newton-Raphson-type algorithm for the maximum likelihood estimate of the parameter. Numerical results indicate that the proposed method is more effective by consistently reaching a global maximum.

Massive pulmonary thromboembolism combined with transient thyrotoxicosis in an 18 year old girl.

BACKGROUND: Pulmonary thromboembolism (PTE) is thought to usually stem from deep vein thrombosis (DVT). However, evidence of DVT could not be found in many cases. Furthermore, transient thyrotoxicosis is a rare but potentially life-threatening emergency involving a systemic hypercoagulable state. We report on an 18 year-old-girl with transient thyrotoxicosis with massive PTE without DVT. CASE PRESENTATION: An 18-year-old girl was admitted to the hospital with syncope. Patient had no history of trauma, any known underlying disease or oral contraceptives use. Chest computed tomography (CT) showed massive PTE in both central pulmonary arteries and diffuse goiter. However, a low extremity Doppler sonogram did not detect DVT. To manage the PTE, we administered low molecular weight heparin. On the other hands, thyroid function test indicated a state of thyrotoxicosis. In addition, patient had a partial protein S deficiency but no other immunologic abnormality. Therefore, the patient was diagnosed with massive PTE, thyrotoxicosis, and partial protein S deficiency. Patient was discharged with oral warfarin and methimazole. A follow-up echocardiogram obtained 3 months after anticoagulation therapy demonstrated normal dimensions and systolic function. After thyrotoxicosis was treated with methimazole for a month, a euthyroid state was achieved and the goiter decreased to a normal size. The methimazole was gradually tapered off and stopped at 4 months. At a 6-month follow up visit, PTE and pulmonary hypertension had disappeared but the patient still had a partial protein S deficiency. We decided to stop all medication with careful monitoring. During a 4-year follow-up period after the episode, she was asymptomatic without any evidence of recurrent systemic thromboembolism or hyperthyroidism. CONCLUSIONS: Early recognition and appropriate treatment of PTE combined with transient thyrotoxicosis were vital to preventing other complications.

Hypertension is associated with oral, laryngeal, and esophageal cancer: a nationwide population-based study.

Several studies have reported an association between hypertension and upper aerodigestive tract cancer, but no large-scale, population-based studies have been conducted to confirm this.The aim of this study was to explore the association between hypertension and risk of upper aerodigestive tract cancer in Koreans. Participants who underwent a national health screening examination from January 1 to December 31, 2009 (n = 9,746,606) were enrolled. We assessed the development of oral, laryngeal, or esophageal cancer until 2016 using records from the Korean Health Insurance claims database during the study period. During the seven-year follow-up period, 6,062, 2,658, and 4,752 subjects were newly diagnosed with oral, laryngeal, and esophageal cancer, respectively. Participants with metabolic syndrome had the highest risk of developing oral cancer (hazard ratio (HR) 1.09, 95% confidence interval (CI) 1.03-1.16), laryngeal cancer (HR 1.27, 95% CI 1.17-1.38), and esophageal cancer (HR 1.11, 95% CI 1.04-1.19). Hypertension was a remarkable risk factor for each cancer (HR 1.11, 95% CI 1.04-1.17 for oral cancer; HR 1.23, 95% CI 1.13-1.33 for laryngeal cancer; HR 1.25, 95% CI 1.18-1.33 for esophageal cancer) after adjusting for age and other variables including gender, smoking status, alcohol intake, exercise, body mass index, and diabetes. Patients with untreated hypertension were at highest risk of developing oral cancer (HR 1.15; 95% CI 1.05-1.26), laryngeal cancer (HR 1.25; 95% CI 1.09-1.44), and esophageal cancer (HR 1.47; 95% CI 1.33-1.63) after adjusting for confounders. Hypertension was associated with the risk of oral, laryngeal, and esophageal cancer, despite of the lack of detailed biochemical information including the cancer cell types (squamous cell carcinoma or adenocarcinoma), cancer stage, physical findings and other medical history. Further studies are warranted to determine the reasons for this association and to establish effective interventions in this vulnerable population.

Predictors of Significant Coronary Artery Disease in Patients with Cerebral Artery Atherosclerosis.

OBJECTIVE: There are few existing data on the status of coronary artery disease (CAD) in patients with atherosclerosis of the cerebral artery detected by brain imaging studies. We aimed to analyze the predictors of asymptomatic angiographically significant CAD detected by simultaneous cerebral and coronary angiography. METHODS: This retrospective cohort study screened data obtained between August 2009 and April 2019; 11,047 patients underwent cerebral angiography for atherosclerotic change (>50% stenosis or aneurysm) seen in brain magnetic resonance angiography (MRA) or computed tomography angiography (CTA) at a single center by endovascular neurosurgeon's decision. Of these, 700 patients including 622 patients who underwent simultaneous coronary and cerebral angiography and 78 patients who underwent coronary angiography within a month were enrolled. We investigated the characteristics and predictors of angiographically significant CAD (>50% stenosis). Furthermore, we also analyzed the major adverse cardiovascular and cerebrovascular events (MACCE), including all-cause death, myocardial infarction, and stroke for 5 years. RESULTS: The frequency of significant CAD was 59% (413/700), the mean age was 68.9 ± 10.3 years, and 60.6% were male. During mean follow-up of 50 months, the MACCE rate of our whole cohort was significantly higher in the CAD group (21.5%) than in the non-CAD group (14.6%; hazard ratio 1.65, 95% CI 1.17-2.33, p value = 0.005). Considering that the embolic stroke is less associated with atherosclerotic change, our predictive model of significant CAD was made without embolic stroke (n = 599). In our multivariate model 2 including univariate <0.1, the independent predictors of significant CAD were male (OR 1.62, 95% CI 1.11-2.35, p = 0.012), diabetes mellitus (OR 1.81, 95% CI 1.22-2.68, p = 0.003), previous stroke (OR 1.63, 95% CI 1.02-2.60, p = 0.039), low ankle-brachial index (ABI; <0.9; OR 3.25, 95% CI 1.21-8.73, p = 0.019), left ventricular ejection fraction (EF) <50% on echocardiography (OR 2.82, 95% CI 1.25-6.35, p = 0.012), troponin I or T positive (OR 2.76, 95% CI 1.69-4.53, p < 0.001), and complex features on cerebral angiography (OR 2.73, 95% CI 1.78-4.19, p < 0.001). CONCLUSIONS: Accurate coronary evaluation by coronary angiography might be considered when patients with atherosclerotic cerebral artery detected on brain MRA or CTA planned cerebral angiography were male or have diabetes mellitus, previous stroke, low ABI (<0.9), left ventricular EF <50% on echocardiography, troponin I or T positivity, and complex features on cerebral angiography.

Reliability analysis of load-sharing systems with memory.

The load-sharing model has been studied since the early 1940s to account for the stochastic dependence of components in a parallel system. It assumes that, as components fail one by one, the total workload applied to the system is shared by the remaining components and thus affects their performance. Such dependent systems have been studied in many engineering applications which include but are not limited to fiber composites, manufacturing, power plants, workload analysis of computing, software and hardware reliability, etc. Many statistical models have been proposed to analyze the impact of each redistribution of the workload; i.e., the changes on the hazard rate of each remaining component. However, they do not consider how long a surviving component has worked for prior to the redistribution. We name such load-sharing models as memoryless. To remedy this potential limitation, we propose a general framework for load-sharing models that account for the work history. Through simulation studies, we show that an inappropriate use of the memoryless assumption could lead to inaccurate inference on the impact of redistribution. Further, a real-data example of plasma display devices is analyzed to illustrate our methods.

Effects of active rehabilitation therapy on muscular back strength and subjective pain degree in chronic lower back pain patients.

[Purpose] This study applied active rehabilitation therapy to muscular back strength and assessed the subjective pain degree in chronic low back pain patients. [Subjects and Methods] Subjects were randomly assigned to two groups: experimental (n=8) and control (n=8). The experimental group performed two types of rehabilitation therapy programs four times per week for eight weeks. The rehabilitation program was based on the Korea Occupational Safety and Health Agency's program. There were several types of stretching and strengthening. Back strength was measured using the Back Muscle Dynamometer TKK-5402. The visual analog scale score, selected to measure degrees of subjective pain, was used to assess treatment efficacy. [Results] For the experimental group, muscular back strength increased from 133.90 ± 11.84 kg before exercise to 145.59 ± 14.49 kg after exercise. In the control group, muscular back strength decreased from 133.92 ± 3.84 kg before exercise to 133.90 ± 5.81 kg after exercise. In the experimental group, the visual analog scale score for subjective pain decreased from 6.63 ± 0.52 before exercise to 5.75 ± 0.46 after exercise; in the control group, it decreased from 5.61 ± 0.52 before exercise to 5.61 ± 0.52 after exercise. [Conclusion] Active rehabilitation therapy is a positive intervention that can provide relief from back pain.

Effects of Cracking Test Conditions on Estimation Uncertainty for Weibull Parameters Considering Time-Dependent Censoring Interval.

It is extremely difficult to predict the initiation time of cracking due to a large time spread in most cracking experiments. Thus, probabilistic models, such as the Weibull distribution, are usually employed to model the initiation time of cracking. Therefore, the parameters of the Weibull distribution are estimated from data collected from a cracking test. However, although the development of a reliable cracking model under ideal experimental conditions (e.g., a large number of specimens and narrow censoring intervals) could be achieved in principle, it is not straightforward to quantitatively assess the effects of the ideal experimental conditions on model estimation uncertainty. The present study investigated the effects of key experimental conditions, including the time-dependent effect of the censoring interval length, on the estimation uncertainties of the Weibull parameters through Monte Carlo simulations. The simulation results provided quantified estimation uncertainties of Weibull parameters in various cracking test conditions. Hence, it is expected that the results of this study can offer some insight for experimenters developing a probabilistic crack initiation model by performing experiments.

A high normal thyroid-stimulating hormone is associated with arterial stiffness, central systolic blood pressure, and 24-hour systolic blood pressure in males with treatment-naïve hypertension and euthyroid.

BACKGROUND: We compared the results of laboratory examinations, echocardiography, arterial stiffness, central blood pressure (BP) and ambulatory BP monitoring (ABPM) between treatment-naïve patients with low normal thyroid-stimulating hormone (TSH) and those with high normal TSH levels. METHODS: A total of 285 consecutively-eligible patients with both treatment-naïve hypertension and euthyroid were divided into two groups: those with low-normal TSH (0.40-1.99 µIU/mL, group 1) and high-normal TSH (2.00-4.50 µIU/mL, group 2) and compared according to group and gender. RESULTS: Males were divided into group 1 (n = 113, 68.9%) and group 2 (n = 51, 31.1%) and females were divided into group 1 (n = 71, 58.7%) and group 2 (n = 50, 41.3%). Multivariate analyses revealed that the augmentation index (71.0 [adjusted mean] ± 1.7 [standard error] vs. 78.8 ± 2.5%, P = 0.045), central systolic BP (SBP) (143.3 ± 2.1 vs. 153.0 ± 3.2 mmHg, P = 0.013), systemic vascular resistance (SVR, 21.4 ± 0.6 vs. 23.9 ± 0.9 mmHg/L/min, P = 0.027), SBP during daytime (144.1 ± 1.4 vs. 151.6 ± 2.1 mmHg, P=0.004) and nighttime (130.4 ± 1.6 vs. 138.5 ± 2.5 mmHg, P=0.008), and nighttime pulse pressure (PP, 47.2 ± 0.9 vs. 51.7 ± 1.4 mmHg, P = 0.010) were significantly higher while cardiac output (5.4 ± 0.1 vs. 4.8 ± 0.2L/min, P = 0.043) and PP amplification (1.02 ± 0.02 vs. 0.94 ± 0.03, P = 0.039) were significantly lower in the male group 2 than in the male group 1. However, there were no significant differences between the two groups in females. CONCLUSIONS: Treatment-naïve hypertensive males with high normal TSH and euthyroid showed higher arterial stiffness, central SBP, SVR, and SBP in ABPM and lower cardiac output and PP amplification as compared to the the low normal TSH group, but not females.

Imatinib mesylate attenuates myocardial remodeling through inhibition of platelet-derived growth factor and transforming growth factor activation in a rat model of hypertension.

Imatinib mesylate is a specific tyrosine kinase inhibitor that may block the platelet-derived growth factor and transforming growth factor pathways. These pathways are known to provoke fibroblast activation. We evaluated whether imatinib, by inhibiting these pathways, prevents diastolic dysfunction and attenuates myocardial remodeling using spontaneously hypertensive rats (SHRs). Eight-week-old male SHRs were randomly assigned to either imatinib treatment group (30 mg/kg per day; n=10; SHR-I) or hypertensive control group (distilled water, n=10; SHR-C). Wistar-Kyoto rats were used as normal controls (n=10). At 16 weeks, all rats underwent hemodynamic studies and Doppler echocardiography and then were euthanized. Their hearts were extracted for histopathologic, immunoblotting, and quantitative reverse transcriptase polymerase chain reaction analyses. Although imatinib did not affect blood pressure, it markedly reduced perivascular and interstitial fibrosis in the hearts of SHR. Echocardiogram showed that imatinib significantly reduced the left ventricular wall thickness (septal/posterior wall; SHR-C versus SHR-I, 18±1/19±2 versus 15±1/15±1 mm; P<0.001) and increased the E/A ratio (SHR-C versus SHR-I, 1.59±0.11 versus 1.84±0.16; P=0.001). Also, imatinib significantly reduced the mRNA expression of collagen type I, III, and platelet-derived growth factor receptor-ß phosphorylation in the hearts of SHR. In addition, imatinib reduced collagen production by inhibiting the phosphorylation of c-abl and platelet-derived growth factor receptor-ß in rat cardiac fibroblasts. In conclusion, these results suggest that imatinib could attenuate myocardial remodeling and improve left ventricular diastolic dysfunction in a hypertensive rat model by affecting platelet-derived growth factor and transforming growth factor-ß1 pathway without the blood pressure-lowering effect.

Successful percutaneous aspiration thrombectomy for acute mesenteric ischemia in a patient with atrial fibrillation despite optimal anticoagulation therapy.

This report describes a case of acute mesenteric ischemia due to acute superior mesenteric artery (SMA) thromboembolism in a patient with chronic atrial fibrillation despite optimal anticoagulation therapy. The patient underwent SMA angiography and endovascular revascularization for acute mesenteric ischemia. We initially tried endovascular thrombolytic therapy for the thromboembolism of SMA, but it did not achieve complete revascularization. Therefore, we performed a percutaneous aspiration thrombectomy, which led to complete revascularization and successful treatment of acute mesenteric ischemia without any additional procedures.

Relationship between resting electrocardiographic parameters and estimated 10-year risk for coronary heart disease in healthy adults in the USA.

BACKGROUND: Little is known about the relationship between resting electrocardiogram (ECG) parameters and the incidence of coronary heart disease (CHD). We sought to establish the association between ECG parameters and estimated 10-year risk for CHD. METHODS: We applied the risk prediction algorithm used by the National Cholesterol Education Program Adult Treatment Panel III guidelines to data from 6399 individuals in the Third National Health and Nutrition Examination Survey (aged 40-79 years) who had sinus rhythm, no previous heart disease, and no evidence of prior myocardial infarction according to the 12-lead Minnesota Code. We used multiple linear and logistic regression models to determine the relationship between 10-year risk for CHD and levels of resting ECG parameters. RESULTS: After adjusting for age, gender, race, and body mass index, individuals with high risk had higher heart rate (HR), left ventricular mass index (LVMI), and cardiac infarction injury score (CIIS), and longer HR-corrected QT (QTc) interval than those with low risk. In models fully adjusted for coronary risk factors, individuals in the highest quintile of HR, PR, and QTc interval were 2.2, 0.7, and 1.8 times, respectively, more likely to have a high 10-year risk as those in the lowest quintiles. There are dose-dependent associations between HR, LVMI, CIIS, and QTc interval and the 10-year risk group. CONCLUSIONS: These findings indicate that high HR, LVMI, and CIIS and prolonged QTc interval are positively and prolonged PR interval is negatively associated with high 10-year risk for CHD in a general population.

Death caused by simultaneous subacute stent thrombosis of sirolimus-eluting stents in left anterior descending artery and left circumflex artery.

Simultaneous drug-eluting stent thrombosis in multivessel disease is a low incidence, but could cause lethal clinical event. We report a case with death caused by simultaneous subacute stent thrombosis of sirolimus-eluting stents in the proximal left anterior descending artery and in the proximal left circumflex artery.

Aortic Valve Sclerosis on Echocardiography is a Good Predictor of Coronary Artery Disease in Patients With an Inconclusive Treadmill Exercise Test.

BACKGROUND AND OBJECTIVES: The treadmill exercise test (TMT) is used as a first-line test for diagnosing coronary artery disease (CAD). However, the findings of a TMT can be inconclusive, such as incomplete or equivocal results. Aortic valve sclerosis (AVS) is known to be a good predictor of CAD. We determined the usefulness of assessing AVS on 2-dimensional (2D) echocardiography for making the diagnosis of CAD in patients with inconclusive results on a TMT. SUBJECTS AND METHODS: This prospective study involved 165 consecutive patients who underwent a TMT that resulted in inconclusive findings, 2D echocardiography to detect AVS, and coronary angiography to detect CAD. Following echocardiography, AVS was classified as none, mild, or severe. CAD was defined as >/=70% narrowing of the luminal diameter on coronary angiography. RESULTS: CAD was more common in patients with AVS than in patients without AVS (75% vs. 47%, respectively, p<0.01). Multiple logistic regression analysis showed that AVS was the only independent predictor of CAD {odds ratio=8.576; 95% confidence interval (CI), 3.739-19.672}. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of the presence of AVS for predicting CAD in a patient with an inconclusive TMT were 62%, 67%, 64%, 75%, and 53%, respectively. During a 1-year clinical follow-up, patients with and without AVS were similar in terms of event-free survival rates. CONCLUSION: If the results of TMT for patients with chest pain on exertion are inconclusive, the presence of AVS on echocardiography is a good predictor of CAD.

Age is an Independent Risk Factor for the Early Morning Blood Pressure Surge in Patients Never-Treated for Hypertension.

BACKGROUND AND OBJECTIVES: The early morning blood pressure surge (EMBPS) has been reported to be associated with cardiovascular events. The aim of this study was to investigate the relationship between 24-hour ambulatory BP monitoring (ABPM) parameters and conventional cardiovascular risk factors. SUBJECTS AND METHODS: Patients (n=346) never-treated for essential hypertension with no other cardiovascular risk factors, such as diabetes, dyslipidemia, and nephropathy were enrolled. The EMBPS was defined as the early morning systolic BP minus the lowest night systolic BP. We compared the 24-hour ABPM parameters in two groups divided by age (<60 and >/=60 years) and examined the association between the 24-hour ABPM parameters and cardiovascular risk factor. RESULTS: The EMBPS (18+/-14 vs. 24+/-14 mmHg, p=0.002), 24-hour mean blood pressure {MBP; 102+/-9 vs. 105+/-11 mmHg, p=0.044}, and 24-hour mean pulse pressure (PP; 52+/-10 vs. 58+/-11 mmHg, p<0.001) were significantly increased in the elderly subjects compared to the younger subjects. The degree of decrease was less in the elderly subjects (10+/-8 vs. 7+/-10%, p=0.002). Based on multivariate analysis, age was an independent risk factor for the highest quartile of EMBPS (>28 mmHg) after adjusting for gender differences, body mass index, and various 24-hour ABPM parameters (odds ratio, 1.051; 95% confidence interval, 1.028-1.075; p<0.001). CONCLUSION: Age is an independent risk factor for EMBPS in patients with never-treated hypertension. BP control in the early morning period is more important in elderly patients so as to prevent cardiovascular events.

Target organ status in white-coat hypertensives: usefulness of serum procollagen type I propeptide in the respect of left ventricular diastolic dysfunction.

BACKGROUND: Myocardial fibrosis is a feature of diastolic dysfunction and target organ damage, which was compared among subjects with normotension (NT), white-coat hypertension (WCH) and essential hypertension (EH). Serum procollagen type I propeptide (PIP) level was assessed as a marker of diastolic dysfunction in WCH. METHODS AND RESULTS: Of 90 subjects, 30 had NT and 30 had WCH (ambulatory daytime blood pressure <135/85 mmHg) and 30 had EH (untreated mild to moderate hypertension); all underwent biochemical and echocardiographic examinations. Those with WCH had a lower left ventricular (LV) mass index than those with EH, but it was higher than in the NT group. WCH patients had a lower mitral valve E/A ratio and a higher LV E/E' (E': septal mitral annular peak velocity) ratio than NT patients, whereas these values were higher and lower respectively than in the EH group. The LV E/E' ratio, an estimate of LV diastolic function, correlated with the serum PIP concentration in WCH patients (r=0.39, P=0.03). CONCLUSION: WCH is an intermediate group between NT and EH in respect of target organ damage. These results show a relationship between LV diastolic function and serum PIP in WCH, so the serum PIP level may be a useful marker of diastolic dysfunction and target organ damage in such patients.

Clinical and angiographic characteristics of acute myocardial infarction caused by vasospastic angina without organic coronary heart disease.

BACKGROUND: Vasospastic angina (VA) can occasionally cause acute myocardial infarction (AMI). METHODS AND RESULTS: From January 2003 to June 2005, coronary spastic angina was diagnosed in 292 patients by performing spasm provocation tests. Among the 292 patients, 21 (7.2% of all the VA patients) had an AMI. There were 20 patients who initially visited the emergency room for AMI without suffering prior VA. One patient with a history of VA had an AMI when he discontinued his medication. Among the 21 VA patients with AMI, 14 had experienced severe emotional stress before they visited the emergency room. The spasm provocation test showed that the VA patients with AMI had more multivessel and diffuse spasm than the VA patients without AMI (p<0.001). CONCLUSION: Clinically, the VA patients with AMI usually had their first symptom of VA as the severe chest pain of AMI. Two-thirds of the VA patients with AMI had experienced emotional stress before their AMI. Angiographically, the spasm provocation test for VA patients with AMI showed more multivessel and diffuse spasm than in VA patients without AMI.

Accelerated degradation models for failure based on geometric Brownian motion and gamma processes.

Based on a generalized cumulative damage approach with a stochastic process describing degradation, new accelerated life test models are presented in which both observed failures and degradation measures can be considered for parametric inference of system lifetime. Incorporating an accelerated test variable, we provide several new accelerated degradation models for failure based on the geometric Brownian motion or gamma process. It is shown that in most cases, our models for failure can be approximated closely by accelerated test versions of Birnbaum-Saunders and inverse Gaussian distributions. Estimation of model parameters and a model selection procedure are discussed, and two illustrative examples using real data for carbon-film resistors and fatigue crack size are presented.