Mintu Nath

Body-Mass Index and Mortality Among Adults Undergoing Cardiac Surgery:A Nationwide Study with a Systematic Review and Meta-Analysis

Background: In an apparent paradox, morbidity and mortality are lower in obese patients undergoing cardiac surgery, although the nature of this association is unclear. We sought to determine whether the obesity paradox observed in cardiac surgery is attributable to reverse epidemiology, bias, or confounding. Methods: Data from the National Adult Cardiac Surgery registry for all cardiac surgical procedures performed between April 2002 and March 2013 were extracted. A parallel systematic review and meta-analysis (MEDLINE, Embase, SCOPUS, Cochrane Library) through June 2015 were also accomplished. Exposure of interest was body mass index categorized into 6 groups according to the World Health Organization classification. Results: A total of 401 227 adult patients in the cohort study and 557 720 patients in the systematic review were included. A U-shaped association between mortality and body mass index classes was observed in both studies, with lower mortality in overweight (adjusted odds ratio, 0.79; 95% confidence interval, 0.76–0.83) and obese class I and II (odds ratio, 0.81; 95% confidence interval, 0.76–0.86; and odds ratio, 0.83; 95% confidence interval, 0.74–0.94) patients relative to normal-weight patients and increased mortality in underweight individuals (odds ratio, 1.51; 95% confidence interval, 1.41–1.62). In the cohort study, a U-shaped relationship was observed for stroke and low cardiac output syndrome but not for renal replacement therapy or deep sternal wound infection. Counter to the reverse epidemiology hypotheses, the protective effects of obesity were less in patients with severe chronic renal, lung, or cardiac disease and greater in older patients and in those with complications of obesity, including the metabolic syndrome and atherosclerosis. Adjustments for important confounders did not alter our results. Conclusions: Obesity is associated with lower risks after cardiac surgery, with consistent effects noted in multiple analyses attempting to address residual confounding and reverse causation.

Randomized trial of red cell washing for the prevention of transfusion-associated organ injury in cardiac surgery

Background. Experimental studies suggest that mechanical cell washing to remove pro‐inflammatory components that accumulate in the supernatant of stored donor red blood cells (RBCs) might reduce inflammation and organ injury in transfused patients. Methods. Cardiac surgery patients at increased risk of large‐volume RBC transfusion were eligible. Participants were randomized to receive either mechanically washed allogenic RBCs or standard care RBCs. The primary outcome was serum interleukin‐8 measured at baseline and at four postsurgery time points. A mechanism substudy evaluated the effects of washing on stored RBCs in vitro and on markers of platelet, leucocyte, and endothelial activation in trial subjects. Results. Sixty adult cardiac surgery patients at three UK cardiac centres were enrolled between September 2013 and March 2015. Subjects received a median of 3.5 (interquartile range 2‐5.5) RBC units, stored for a mean of 21 (SD 5.2) days, within 48 h of surgery. Mechanical washing reduced concentrations of RBC‐derived microvesicles but increased cell‐free haemoglobin concentrations in RBC supernatant relative to standard care RBC supernatant. There was no difference between groups with respect to perioperative serum interleukin‐8 values [adjusted mean difference 0.239 (95% confidence intervals ‐0.231, 0.709), P=0.318] or concentrations of plasma RBC microvesicles, platelet and leucocyte activation, plasma cell‐free haemoglobin, endothelial activation, or biomarkers of heart, lung, or kidney injury. Conclusions. These results do not support a hypothesis that allogenic red blood cell washing has clinical benefits in cardiac surgery. Clinical trial registration. ISRCTN 27076315.

Diurnal variation and repeatability of arterial stiffness and cardiac output measurements in the third trimester of uncomplicated pregnancy

Aim: To investigate same day repeated measures and diurnal variation of arterial stiffness, cardiac output (CO), stroke volume (SV) and total peripheral resistance (TPR) during the third trimester of normal pregnancy. Methodology: Pulse wave velocity (PWV) and augmentation index (AIx) were recorded using the Arteriograph, while CO, SV and TPR were recorded using noninvasive cardiac output monitoring. The measurements were obtained in the third trimester of pregnancy from 21 healthy pregnant women at four time points (morning, afternoon, evening and midnight) over a 24-h period. Triplicate measurements of 67 women were obtained at 5-min intervals to assess repeatability between measurements within a patient. Results: Diurnal measurements of arterial stiffness for brachial AIx, aortic AIx and PWV were not statistically significantly different at any of the four time points. Estimated means (SD) for PWV at the four stated time points were 7.81 (2.05), 8.45 (1.68), 7.87 (1.74) and 7.64 m/s (1.15), respectively (P = 0.267). Estimates for AIx at those time points were 10.22 (15.62), 4.44 (10.07), 6.49 (10.92) and 8.40% (8.16), respectively (P = 0.295). Similarly, mean arterial pressure, SV, SV index and TPR did not show any evidence of diurnal variation. However, we observed that the mean CO, cardiac index (CI) and heart rate (HR) varied from morning to midnight; the mean CO, HR and CI increased significantly in the afternoon compared with the corresponding mean morning measurements in a similar fashion to HR. Mean (SD) CO estimates at the four stated time points were 5.90 (1.33), 6.38 (1.49), 6.18 (1.43) and 5.80 ml/min (1.19), respectively, (P < 0.001), whereas mean CI estimates were 3.65 (0.58), 3.93 (0.68), 3.81 (0.65), and 3.57 (0.48), respectively, (P < 0.001), and mean HR estimates were 95 (12), 98 (13), 95 (12) and 88 (12.98), respectively (P < 0.001). Triplicate measurements of 61 women in our repeatability study showed moderate-to-high correlation between observations on the same woman for all Arteriograph and noninvasive cardiac output monitoring variables (estimates of intraclass correlation ranged from 0.49 to 0.91). Conclusion: With the exception of CO, CI and HR which showed a diurnal variation, measurements of most haemodynamic parameters did not change significantly from morning to midnight, suggesting there was no evidence of systematic differences in the mean values of these variables at these time points. Multiple consecutive noninvasive measurements of vascular stiffness, CO, SV and TPR were highly correlated confirming repeatability of measurements in the third trimester of uncomplicated pregnancy, so these haemodynamic measurements do not need to be undertaken at a specific time period of the day.

A Comparison of Red Cell Rejuvenation versus Mechanical Washing for the Prevention of Transfusion-associated Organ Injury in Swine

Background: We evaluated the effects of two interventions that modify the red cell storage lesion on kidney and lung injury in experimental models of transfusion. Methods: White–landrace pigs (n = 32) were allocated to receive sham transfusion (crystalloid), 14-day stored allogeneic red cells, 14-day red cells washed using the red cells washing/salvage system (CATS; Fresenius, Germany), or 14-day red cells rejuvenated using the inosine solution (Rejuvesol solution; Zimmer Biomet, USA) and washed using the CATS device. Functional, biochemical, and histologic markers of organ injury were assessed for up to 24 h posttransfusion. Results: Transfusion of 14 day red cells resulted in lung injury (lung injury score vs. sham, mean difference −0.3 (95% CI, −0.6 to −0.1; P = 0.02), pulmonary endothelial dysfunction, and tissue leukocyte sequestration. Mechanical washing reduced red cell–derived microvesicles but increased cell-free hemoglobin in 14-day red cell units. Transfusion of washed red cells reduced leukocyte sequestration but did not reduce the lung injury score (mean difference −0.2; 95% CI, −0.5 to 0.1; P = 0.19) relative to 14-day cells. Transfusion of washed red cells also increased endothelial activation and kidney injury. Rejuvenation restored adenosine triphosphate to that of fresh red cells and reduced microvesicle concentrations without increasing cell-free hemoglobin release. Transfusion of rejuvenated red cells reduced plasma cell-free hemoglobin, leukocyte sequestration, and endothelial dysfunction in recipients and reduced lung and kidney injury relative to 14-day or washed 14-day cells. Conclusions: Reversal of the red cell storage lesion by rejuvenation reduces transfusion-associated organ injury in swine.

Longitudinal study to assess changes in arterial stiffness and cardiac output parameters among low-risk pregnant women.

AIM A single-centre, prospective longitudinal study to assess changes in maternal arterial stiffness and cardiac output parameters among low-risk healthy pregnant women. METHODOLOGY Thirty low-risk, healthy, pregnant women attending their routine antenatal dating ultrasound scan were recruited. Non-invasive assessment of arterial stiffness and cardiac output was undertaken at five gestational windows from 11 to 40 weeks of pregnancy. Data were analysed using a linear mixed model incorporating time and other relevant predictors as fixed effects, and patient as a random effect. RESULTS Gestational age had a significant effect on all arterial stiffness parameters, including brachial augmentation index (AIx) (p = .001), aortic AIx (p = .002) and aortic pulse wave velocity (p = .002). The aortic AIx (%) reduced during pregnancy: the lowest mean (standard error, SE) was 4.07 (1.01) at 28 weeks before it increased to 7.04 (SE 1.64) at 40 weeks. Similarly, non-invasive assessments of cardiac output (p < .001), stroke volume (p = .014), heart rate (p < .001) and total peripheral resistance (p < .001) demonstrated significant changes with gestational age. Mean cardiac output (l/m) increased during pregnancy reaching a peak at 28 weeks gestation 6.66 (SE 0.28), but dropped thereafter to reach 5.71 (SE 0.25) around term. CONCLUSION The current study provides pregnancy normograms for gestational changes in arterial stiffness and cardiac output parameters among low-risk, healthy pregnant women. Further work will be required to assess the risk of placental mediated diseases and pregnancy outcome among pregnant women with parameters outside the normal range.

Haemodynamic differences amongst women who were screened for gestational diabetes in comparison to healthy controls

AIM To assess the changes in haemodynamics amongst pregnant women who were screened for gestational diabetes mellitus (GDM) in comparison to low-risk healthy pregnant controls. METHODOLOGY A total of 120 pregnant women of mean (standard deviation) age 31.03 (5.41) years who attended their oral glucose tolerance test as part of the national screening for GDM (study), and 60 low-risk healthy pregnant women (control) of mean age 29.71 (5.33) years, were invited to participate in this study. All women included in the study booked at the University Hospitals of Leicester NHS Trust and fulfilled the relevant inclusion criteria. Non-invasive assessment of arterial stiffness and cardiac output were undertaken on participants between 26 and 28 weeks of pregnancy. The mean difference between GDM and low-risk group for each of the arterial stiffness and cardiac output measurements was assessed by a two-sample unpaired t-test. RESULTS Significant differences were found between the study and control groups for brachial (-64.5 vs. -69.5, p < 0.04) and aortic augmentation indices (5.2 vs. 2.7, p = 0.04), though there was no significant difference for PWV (8.3 vs. 8.1, p = 0.49). Cardiac output (7.6 vs. 7.0, p = 0.011), stroke volume (84.4 vs. 76.9, p = 0.013) and central mean arterial pressure (71 vs. 58, <0.001) were also significantly different between groups. However, no significant differences were reported for heart rate, systolic and diastolic blood pressure, or total peripheral resistance. CONCLUSION Pregnant women at risk of GDM between gestational weeks 26 and 28 had significantly increased measures of arterial stiffness, as assessed by brachial and aortic augmentation indices, compared with low-risk healthy controls. Whether these women are at greater long-term cardiovascular disease risk warrants further investigation.

The effects of metformin on maternal haemodynamics in gestational diabetes mellitus: A pilot study

BACKGROUND Gestational diabetes mellitus (GDM) is a major clinical challenge and is likely to remain so as the incidence of GDM continues to increase. AIM To assess longitudinal changes in maternal haemodynamics amongst women diagnosed with GDM requiring either metformin or dietary intervention in comparison to low-risk healthy controls. METHODOLOGY Fifty-six pregnant women attending their first appointment at the GDM clinic and 60 low-risk healthy pregnant controls attending their routine antenatal clinics were recruited and assigned to three groups: GDM Metformin (GDM-M), GDM Diet (GDM-D) and Control. Non-invasive assessment of maternal haemodynamics, using recognised measures of arterial stiffness and central blood pressure (Arteriograph®), were undertaken under controlled conditions within four gestational windows: antenatal; AN1 (26-28 weeks), AN2 (32-34 weeks) and AN3 (37-40 weeks), and postnatal (PN) (6-8 weeks after delivery). Data were analysed using a linear mixed model incorporating gestational age and other relevant predictors, including age, blood pressure (BP), baseline bodyweight and pulse as fixed effects, and patient as a random effect. RESULTS Fitted linear mixed models showed evidence of a two-way interaction effect between groups (GDM-D, GDM-M and Control) and stages of gestation (AN1, AN2, AN3 and PN) for maternal haemodynamic parameters: brachial artery augmentation index (AIx) (p = 0.004), aortic AIx (p = 0.008), and central systolic BP (p = 0.001). However, differences in respect of aortic pulse wave velocity (p = 0.001) and heart rate (p < 0.001) were only significant for gestational stage. At AN2, we did not observe any evidence that the mean brachial Aix in the GDM-M was different from the control group (p = 0.158). CONCLUSION AIx and central systolic BP measures of arterial stiffness are adversely affected by GDM in comparison to controls during pregnancy. The possible beneficial effects of metformin therapy seen at 32 to 34 weeks of gestation require further exploration.

Adult height and risk of 50 diseases: a combined epidemiological and genetic analysis

BackgroundAdult height is associated with risk of several diseases, but the breadth of such associations and whether these associations are primary or due to confounding are unclear. We examined the association of adult height with 50 diseases spanning multiple body systems using both epidemiological and genetic approaches, the latter to identify un-confounded associations and possible underlying mechanisms.MethodsWe examined the associations for adult height (using logistic regression adjusted for potential confounders) and genetically determined height (using a two-sample Mendelian randomisation approach with height-associated genetic variants as instrumental variables) in 417,434 individuals of white ethnic background participating in the UK Biobank. We undertook pathway analysis of height-associated genes to identify biological processes that could link height and specific diseases.ResultsHeight was associated with 32 diseases and genetically determined height associated with 12 diseases. Of these, 11 diseases showed a concordant association in both analyses, with taller height associated with reduced risks of coronary artery disease (odds ratio per standard deviation (SD) increase in height ORepi = 0.80, 95% CI 0.78–0.81; OR per SD increase in genetically determined height ORgen = 0.86, 95% CI 0.82–0.90), hypertension (ORepi = 0.83, 95% CI 0.82–0.84; ORgen = 0.88, 95% CI 0.85–0.91), gastro-oesophageal reflux disease (ORepi = 0.85, 95% CI 0.84–0.86; ORgen = 0.94, 95% CI 0.92–0.97), diaphragmatic hernia (ORepi = 0.81, 95% CI 0.79–0.82; ORgen = 0.91, 95% CI 0.88–0.94), but increased risks of atrial fibrillation (ORepi = 1.42, 95% CI 1.38–1.45; ORgen = 1.33, 95% CI 1.26–1.40), venous thromboembolism (ORepi = 1.18, 95% CI 1.16–1.21; ORgen = 1.15, 95% CI 1.11–1.19), intervertebral disc disorder (ORepi = 1.15, 95% CI 1.13–1.18; ORgen = 1.14, 95% CI 1.09–1.20), hip fracture (ORepi = 1.19, 95% CI 1.12–1.26; ORgen = 1.27, 95% CI 1.17–1.39), vasculitis (ORepi = 1.15, 95% CI 1.11–1.19; ORgen = 1.20, 95% CI 1.14–1.28), cancer overall (ORepi = 1.09, 95% CI 1.08–1.11; ORgen = 1.06, 95% CI 1.04–1.08) and breast cancer (ORepi = 1.08, 95% CI 1.06–1.10; ORgen = 1.07, 95% CI 1.03–1.11). Pathway analysis showed multiple height-associated pathways associating with individual diseases.ConclusionsAdult height is associated with risk of a range of diseases. We confirmed previously reported height associations for coronary artery disease, atrial fibrillation, venous thromboembolism, intervertebral disc disorder, hip fracture and cancer and identified potential novel associations for gastro-oesophageal reflux disease, diaphragmatic hernia and vasculitis. Multiple biological mechanisms affecting height may affect the risks of these diseases.

Directional sensitivity of dynamic cerebral autoregulation in squat-stand maneuvers

Dynamic cerebral autoregulation (CA), the transient response of cerebral blood flow (CBF) to rapid changes in arterial blood pressure (BP), is usually modeled as a linear mechanism. We tested the hypothesis that dynamic CA can display nonlinear behavior resulting from differential efficiency dependent on the direction of BP changes. Cerebral blood velocity (CBV) (transcranial Doppler), heart rate (HR) (three-lead ECG), continuous BP (Finometer), and end-tidal CO2 (capnograph) were measured in 10 healthy young subjects during 15 squat-stand maneuvers (SSM) with a frequency of 0.05 Hz. The protocol was repeated with a median (interquartile range) of 44 (35-64) days apart. Dynamic CA was assessed with the autoregulation index (ARI) obtained from CBV step responses estimated with an autoregressive moving-average model. Mean BP, HR, and CBV were different (all P < 0.001) between squat and stand, regardless of visits. ARI showed a strong interaction ( P < 0.001) of SSM with the progression of transients; in general, the mean ARI was higher for the squat phase compared with standing. The changes in ARI were partially explained by concomitant changes in CBV ( P = 0.023) and pulse pressure ( P < 0.001), but there was no evidence that ARI differed between visits ( P = 0.277). These results demonstrate that dynamic CA is dependent on the direction of BP change, but further work is needed to confirm if this finding can be generalized to other physiological conditions and also to assess its dependency on age, sex and pathology.