A novel low-complexity digital filter design for wearable ECG devices.

Wearable and implantable Electrocardiograph (ECG) devices are becoming prevailing tools for continuous real-time personal health monitoring. The ECG signal can be contaminated by various types of noise and artifacts (e.g., powerline interference, baseline wandering) that must be removed or suppressed for accurate ECG signal processing. Limited device size, power consumption and cost are critical issues that need to be carefully considered when designing any portable health monitoring device, including a battery-powered ECG device. This work presents a novel low-complexity noise suppression reconfigurable finite impulse response (FIR) filter structure for wearable ECG and heart monitoring devices. The design relies on a recently introduced optimally-factored FIR filter method. The new filter structure and several of its useful features are presented in detail. We also studied the hardware complexity of the proposed structure and compared it with the state-of-the-art. The results showed that the new ECG filter has a lower hardware complexity relative to the state-of-the-art ECG filters.

Effects of acute rejection vs new-onset diabetes after transplant on transplant outcomes in pediatric kidney recipients: analysis of the Organ Procurement and Transplant Network/United Network for Organ Sharing (OPTN/UNOS) database.

Improving long-term transplant and patient survival is still an ongoing challenge in kidney transplant medicine. Our objective was to identify the subsequent risks of new-onset diabetes after transplant (NODAT) and acute rejection (AR) in the first year post-transplant in predicting mortality and transplant failure. A total of 4687 patients without preexisting diabetes (age 2-20 years, 2004-2010) surviving with a functioning transplant for longer than 1 year with at least one follow-up report were identified from the OPTN/UNOS database as of September 2014. Study population was stratified into four mutually exclusive groups: Group 1, patients with a history of AR; Group 2, NODAT+; Group 3, NODAT+ AR+; and Group 4, the reference group (neither). Multivariate regression was used to analyze the relative risks for the outcomes of transplant failure and mortality. The median follow-up time was 1827 days after 1 year post-transplant. AR was associated with an increased risk of adjusted graft and death-censored graft failure (HR 2.87, CI 2.48-3.33, P < .001 and HR 2.11, CI 1.81-2.47, P < .001), respectively. NODAT and AR were identified in 3.5% and 14.5% of all study patients, respectively. AR in the first year post-transplant was a major risk factor for overall and death-censored graft failure, but not mortality. However, NODAT was not a risk factor on graft survival or mortality.

Automatic detection of atrial fibrillation using stationary wavelet transform and support vector machine.

BACKGROUND: Atrial fibrillation (AF) is the most common cardiac arrhythmia, and a major public health burden associated with significant morbidity and mortality. Automatic detection of AF could substantially help in early diagnosis, management and consequently prevention of the complications associated with chronic AF. In this paper, we propose a novel method for automatic AF detection. METHOD: Stationary wavelet transform and support vector machine have been employed to detect AF episodes. The proposed method eliminates the need for P-peak or R-Peak detection (a pre-processing step required by many existing algorithms), and hence its performance (sensitivity, specificity) does not depend on the performance of beat detection. The proposed method has been compared with those of the existing methods in terms of various measures including performance, transition time (detection delay associated with transitioning from a non-AF to AF episode), and computation time (using MIT-BIH Atrial Fibrillation database). RESULTS: Results of a stratified 2-fold cross-validation reveals that the area under the Receiver Operative Characteristics (ROC) curve of the proposed method is 99.5%. Moreover, the method maintains its high accuracy regardless of the choice of the parameters' values and even for data segments as short as 10s. Using the optimal values of the parameters, the method achieves sensitivity and specificity of 97.0% and 97.1%, respectively. DISCUSSION: The proposed AF detection method has high sensitivity and specificity, and holds several interesting properties which make it a suitable choice for practical applications.

Impact of Diabetes Mellitus on Survival Outcome of Lung Transplant Recipients: An Analysis of OPTN/UNOS Data.

BACKGROUND: There are limited data on the outcome of diabetic lung recipients, especially in those with new-onset diabetes after transplantation (NODAT). METHODS: We studied prevalence of pre-transplant diabetes mellitus (PDM) and cumulative incidence of NODAT in lung recipients using the Organ Procurement and Transplantation Network /United Network for Organ Sharing database. Between 2004 and 2011, adult (≥18 years old) recipients transplanted with either first single- or double-lung were included. Those who lacked a diabetes record or received multi-organ transplants were excluded. Patient survival were studied in recipients who had functioning grafts for at least one year. RESULTS: There were 10,226 recipients who had at least one diabetes record, the prevalence of PDM was 18.25% and the cumulative incidence of NODAT during the five years post-transplant was 39.43%. Of 9,117 recipients who had functioning grafts for at least one year, adjusted hazard ratios (HR) of PDM and NODAT, compared to the diabetes-free group, were 1.12 (p=0.048) and 1.12 (p=0.025), respectively. Independent risk factors for mortality included the presence of rejection in the one year, cytomegalovirus serology donor positive/recipient negative, and recipient age >60 years. Among recipients with cystic fibrosis, there was no statistical difference in mortality between diabetic recipients and the diabetes-free group. Compared to the diabetes-free group, the adjusted HRs for mortality of PDM and NODAT in recipients without cystic fibrosis were 1.15 (p=0.031) and 1.14 (p=0.011), respectively. CONCLUSIONS: Diabetes was associated with mortality in lung transplant recipients overall and in lung recipients without cystic fibrosis. However, there was no association between diabetes and mortality in lung recipients with cystic fibrosis.

Incidence of conversion to active waitlist status among temporarily inactive obese renal transplant candidates.

BACKGROUND: Candidates may be active or temporarily inactive (status 7) on the kidney transplant waiting list. One reason candidates may be inactive is for a "weight currently inappropriate for transplantation." We hypothesized that many of these candidates would not achieve active status. METHODS: Using OPTN/UNOS data from 2006 to 2012, we used competing risks methods to determine the cumulative incidence of conversion to active status (activation), death, and delisting before conversion among 1679 obese adult kidney candidates designated as status 7 because of a weight inappropriate for transplantation. Fine and Gray competing risks regression was performed to characterize factors associated with conversion to active status in the overall study population and of transplantation among a subgroup of activated candidates. RESULTS: At 6 years, the cumulative incidence of activation was 49%, of death before conversion was 15%, and of delisting was 21%. Higher body mass index (BMI) was strongly associated with a decreased subhazard of activation (BMI ≥45 versus 30-34.9, sHR: 0.22; 95% CI, 0.16-0.33). Female sex, diabetic end-stage renal disease, history of a previous transplant, panel reactive antibodies less than 80%, dialysis dependence at listing, and UNOS region 5 were negatively associated with activation. Among activated candidates, the cumulative incidence of transplantation at 6 years after initial waitlisting was 61%. CONCLUSION: Our findings indicate that half of obese status 7 candidates with a weight inappropriate for transplantation will not achieve active waitlist status. BMI at listing had a strong association with conversion to active status; comorbid factors and regional variation also impact activation.

Can aminotransferase-to-platelet ratio index and other non-invasive markers effectively reduce liver biopsies for renal transplant evaluation of hepatitis C virus-positive patients?

BACKGROUND: Advanced fibrosis or cirrhosis is still regarded as a contraindication for kidney transplantation alone by most centers. The value of aminotransferase to platelet ratio index (APRI) and other non-invasive markers has been less studied in hepatitis C virus (HCV)-positive patients with concurrent end-stage renal disease to predict hepatic fibrosis. Can these be used to effectively decrease the number of biopsies done in these patients being evaluated for transplantation? METHODS: Our study population included 255 patients with liver biopsy data. All patient information was collected and reviewed from medical records. The diagnostic accuracy of the predictive models was analyzed by calculating sensitivity, specificity, positive predictive value and negative predictive value. RESULTS: The variables associated with F3-F4 were aspartate aminotransferase (P = 0.007), bilirubin (P ≤ 0.001), platelet count (P = 0.01) and APRI (P ≤ 0.001). The use of any one laboratory abnormality to predict liver biopsy scores did not show high positive predictive values (22.6-72.7%). Having abnormal liver findings or cirrhosis on imaging was associated with high specificities (92.0-97.8%) but low sensitivities (31.4-42.9%). Using APRI levels of ≥0.40 and ≤0.95 as an indication for liver biopsy, 50% of patients with F3-F4 would have correctly avoided having a biopsy. However, 33% of patients with F3-F4 would have been mislabeled and not be indicated for biopsy. CONCLUSIONS: Our data suggest that there may not currently be a simple and sufficiently accurate non-invasive test to replace liver biopsy in renal transplant workup for HCV-positive patients. The risks outweigh the benefits when it comes to using non-invasive markers like the APRI.

Renal Transplant Outcomes in Waitlist Candidates with a Previous Inactive Status Due to Being Temporarily Too Sick.

BACKGROUND: In 2003, the United Network for Organ Sharing (UNOS) changed its policy to allow candidates with 'inactive' status to accrue time on the waitlist. In this study, we assessed the transplant outcomes among deceased donor kidney transplant (DDKT) recipients who were temporarily inactive specifically due to medical reason, i.e., being temporarily too sick (reason 7). METHODS: Using the UNOS database, adult DDKT recipients were divided into two groups: those who had never been inactivated (active group) and those with a history of being inactive due to reason 7 (reason 7 group). Patient and graft survival, 3-year risk of death, and graft failure were examined and compared. RESULTS: After 3 years of follow-up, patient survival in the reason 7 group was significantly lower than that of the active group (88.14% versus 91.93%, p < 0.01). The reason 7 group had a 20% increased risk of death (hazard ratio, HR 1.20, confidence interval, CI 1.04 - 1.38), a 16% increase in graft failure (HR 1.16, CI 1.06-1.28), and a 15% decrease in death-censored graft failure (HR 1.15, CI 1.01-1.31). CONCLUSION: Recipients with a history of reason 7 have lower patient and graft survival when compared to the active group. Nonetheless, the margins of difference are minimal. Candidates with a history of reason 7 should not be discouraged from transplantation once they return to active status. Standardized criteria for placing candidates on inactive status should be developed to reduce disparities among transplant centers.

Improved survival among sickle cell kidney transplant recipients in the recent era.

BACKGROUND: Studies from older cohorts of kidney recipients have observed that recipients with sickle cell disease (SCD) have lower patient survival compared with age- and race-matched controls. We examined whether survival has improved among SCD recipients in the current era. METHODS: Using Organ Procurement and Transplantation Network/United Network for Organ Sharing data, all black/African-American kidney recipients were stratified according to transplant year into an early (1988-99) and recent era (2000-11). Patient and allograft survival among SCD recipients and those with other diagnoses were compared (early era: SCD n = 67, others n = 20 694; recent era: SCD n = 106, others n = 34 428). A secondary-matched cohort analysis compared patient and allograft survival between SCD recipients matched to recipients with other diagnoses based on recipient and donor age, gender and donor type (deceased versus living). RESULTS: Patient survival at 6 years was lower among SCD recipients in the early era compared with other diagnoses (55.7 versus 78.0%; P < 0.001). Six-year patient survival among sickle cell recipients improved in the recent era (69.8%; P versus early era = 0.04), although still trended toward lower survival compared with other diagnoses (80.0%; P = 0.07). Multivariate Cox proportional hazard models revealed an increased mortality risk with SCD in both eras [early: hazard ratio (HR) = 3.12; 95% confidence interval (CI): 2.15-4.54; recent: HR: 2.03; 95% CI: 1.31-3.16]. Patient survival among matched SCD recipients in the recent era was comparable to diabetic recipients (SCD: 73.1%, diabetes: 74.1%; P = 0.44). CONCLUSIONS: Patient survival has improved among contemporary sickle cell recipients compared with an earlier cohort and is comparable to a matched cohort of diabetic kidney recipients. Appropriately selected SCD patients may receive kidney transplants with reasonable survival outcome.

Kidney failure requiring kidney transplantation after pancreas transplant alone.

Pancreas transplant alone (PTA) is usually performed in type 1 diabetic patients with preserved renal function to correct severe metabolic complications. One of the major concerns is renal failure after PTA. Here, we reported the cumulative incidence of kidney failure requiring kidney transplantation (KF/KT) among PTA recipients in the United States. Using the Organ Procurement Transplant Network/ United Network for Organ Sharing database, all primary adult PTA recipients with estimated baseline glomerular filtration rate (by the Modification of Diet in Renal Disease equation) >or=60 mL/min/1.73m2 were selected (n=1085). KF/ KT after PTA was defined as: wait-listing for or receiving a kidney alone (KA) or simultaneous pancreas kidney (SPK) transplant. The median follow-up time was 1185 days (25-75%: 524-2183). Ten years post PTA, 120 (11.1%) patients developed KF/KT; of those, 70 (6.5%) subsequently received a KA/SPK transplant (56 received KA and 14 received SPK) and 50 (4.6%) recipients were listed without receiving a transplant. The cumulative incidence of KF/KT after PTA at 1, 3, and 5 years after PTA was 0.3, 2.5, and 9.7%, respectively. In conclusion, KF/KT after PTA was not uncommon (9.7% at 5 years), and prospective PTA recipients should be aware of the risks of kidney failure after transplantation.