Differences in regional cerebral oximetry during cardiac surgery for patients with or without postoperative cerebral ischaemic lesions evaluated by magnetic resonance imaging.

BACKGROUND: Near infrared spectroscopy (NIRS) is widely used to monitor regional cerebral tissue oxygenation (rScO2). We compared rScO2 values during cardiac surgery in patients with or without new cerebral ischaemic lesions on diffusion weighted magnetic resonance imaging (DWI). We hypothesised patients with new cerebral lesions would have impaired tissue oxygenation reflected in their rScO2 values. METHODS: NIRS and DWI data were collected in 152 elective cardiac surgery patients. Absolute rScO2 values, duration of desaturation below thresholds (baseline, 10%, and 20%), and accumulated cerebral desaturation load were compared between patients with or without new cerebral lesions on DWI. Primary outcome was time below 10% from rScO2 baseline. RESULTS: The time below 10% from rScO2 baseline was significantly longer for patients with new cerebral lesions than for patients without [median (inter-quartile range): 11.0 (0.4; 37.5) min vs 1.8 inter-quartile range: (0.05; 20.9) min, P=0.02]. Furthermore, they had a higher accumulated desaturation load below baseline (P=0.02) and 10% below baseline (P=0.02). Finally, their absolute minimum rScO2 value was significantly lower (P=0.01). However, the frequency of patients with desaturation below 10% and 20% was comparable between patients with and without new cerebral lesions. Receiver-operating characteristic curve analysis did not identify a clear-cut critical threshold among the investigated rScO2 variables. CONCLUSIONS: Use of NIRS identified significant group differences in rScO2 values between patients with or without new ischaemic lesions. However, a critical threshold could not be identified because of a high variation in NIRS values across both groups. CLINICAL TRIAL REGISTRATION: NCT 02185885.

Arterial pressure during cardiopulmonary bypass is not associated with acute kidney injury.

BACKGROUND: Acute kidney injury (AKI) after cardiac surgery is common and is associated with increased mortality. We wanted to investigate if the arterial pressure or the use of norepinephrine during cardiopulmonary bypass were associated with AKI. METHODS: A retrospective analysis of patients who underwent coronary artery bypass grafting with or without concomitant procedures was conducted. AKI was defined using the RIFLE criteria. Data on arterial pressure and use of norepinephrine during cardiopulmonary bypass were entered in a binary logistic regression model to control for possible perioperative confounders. RESULTS: A total of 623 patients were included. Mean age was 68.3 ± 9.7 years and 81% were males. AKI was observed in 198 patients (32%). Mean arterial pressure was 47 ± 6 mmHg and 45 ± 6 mmHg (P = 0.008) in the AKI and no-AKI group, respectively. Norepinephrine was used more frequently and in higher amounts, during cardiopulmonary bypass, in patients who developed AKI. These differences in arterial pressures and use of norepinephrine between the groups were not found to be significant when entered in the binary logistic regression model. CONCLUSION: No independent relationship between arterial pressure or use of norepinephrine and AKI was found.

Measurements of cardiac output obtained with transesophageal echocardiography and pulmonary artery thermodilution are not interchangeable.

BACKGROUND: Echocardiography is increasingly becoming an integrated tool for circulatory evaluation in the intensive care unit and the operating room. Therefore, it is imperative to know the reproducibility of measurements obtained by echocardiography. In this study, a comparison of cardiac output (CO) measurements obtained with transesophageal echocardiography (TEE) and pulmonary artery catheter (PAC) thermodilution (TD) was carried out to test the precision, accuracy and trending ability of CO measurements obtained with TEE. METHODS: Twenty-five patients completed the study. Each patient was placed in the following successive positions: supine, head-down tilt, head-up tilt, supine, supine with phenylephrine administration, pace heart rate 80 beats per minute (bpm), pace heart rate 110 bpm. TEE CO and PAC CO were measured simultaneously. The agreement was analysed by Bland-Altman plots, and to assess trending ability, a polar plot was constructed. RESULTS: Both methods showed an acceptable precision 8% (PAC TD) and 16% (TEE). In comparison with PAC TD, the TEE was associated with a bias of -0.22 l/minute [95% confidence interval: -0.54; 0.10], wide limits of agreement (-1.73 l/minute; 1.29 l/minute), a percentage error of 38.6% and a trending ability with a radial degree of 53.6°, corresponding to a poor trending ability. CONCLUSION: In comparison, CO measurements obtained with TEE and PAC TD had wide limits of agreement, a larger percentage error than would be expected from the precision of the two methods, and a poor trending ability. Thus, TEE is not interchangeable with PAC TD for measuring CO.

The feasibility of tricuspid annular plane systolic excursion performed by transesophageal echocardiography throughout heart surgery and its interchangeability with transthoracic echocardiography.

Tricuspid annular plane systolic excursion (TAPSE) is a robust measure of RV function, but the performance of transesophageal echocardiography (TEE) measured TAPSE during surgery is not well established. We aim to evaluate feasibility of various TEE views before, during and after surgery. Furthermore, we compare performance of individual TEE measurements depending on view and method (AMM- and M-mode as well as 2D) as well as TAPSE measured using TEE with transthoracic echocardiography (TTE) TAPSE. The study was conducted from January 2015 through September 2016. In 47 patients with normal left ventricular ejection fraction, TEE was prospectively performed during coronary artery bypass grafting surgery. TAPSE and tricuspid annulus tissue Doppler imaging (TDI) were recorded in five different views at pre-specified time points during surgery. Data were analyzed for availability (obtainable/readable images) and reliability (intra-/inter-observer bias and precision). Finally, TEE TAPSE was compared to TTE TAPSE immediately before and after surgery. TAPSE and TDI with TEE was achievable in > 90% of patients in the transgastric view during surgery. The AM- and M-mode had the best reliability and the best correlation with TAPSE measured with TTE. The deep transgastric view was achievable in less than 50% after sternotomy, and TAPSE measured from 2D had a poorer performance compared to the AM- and M-mode. TDI demonstrated a high reliability throughout surgery. RV function can be evaluated by TAPSE and TDI using TEE during surgery. TEE values from the transgastric view demonstrated high performance throughout surgery and a good agreement with TTE TAPSE measurements.

Antiremodeling effects on the left ventricle during beta-blockade with metoprolol in the treatment of chronic heart failure.

OBJECTIVES: The purpose of the study was to investigate the effects of beta1-blockade on left ventricular (LV) size and function for patients with chronic heart failure. BACKGROUND: Large-scale trials have shown that a marked decrease in mortality can be obtained by treatment of chronic heart failure with beta-adrenergic blocking agents. Possible mechanisms behind this effect remain yet to be fully elucidated, and previous studies have presented insignificant results regarding suspected LV antiremodeling effects. METHODS: In this randomized, placebo-controlled and double-blind substudy to the Metoprolol CR/XL Randomized Intervention Trial in Heart Failure (MERIT-HF), 41 patients were examined with magnetic resonance imaging three times in a six-month period, assessing LV dimensions and function. RESULTS: Decreases in both LV end-diastolic volume index (150 ml/m2 at baseline to 126 ml/m2 after six months, p = 0.007) and LV end-systolic volume index (107 ml/m2 to 81 ml/m2, p = 0.001) were found, whereas LV ejection fraction increased in the metoprolol CR/XL group (29% to 37%, p = 0.005). No significant changes were seen in the placebo group regarding these variables. Left ventricular stroke volume index remained unchanged, whereas LV mass index decreased in both groups (175 g/m2 to 160 g/m2 in the placebo group [p = 0.005] and 179 g/m2 to 164 g/m2 in the metoprolol CR/XL group [p = 0.011). CONCLUSIONS: This study is the first randomized study to demonstrate that the beta1-blocker metoprolol CR/XL has antiremodeling effects on the LV in patients with chronic heart failure and consequently provides an explanation for the highly significant decrease in mortality from worsening heart failure found in the MERIT-HF trial.

Evaluation of impaired left ventricular ejection fraction and increased dimensions by multiple neurohumoral plasma concentrations.

BACKGROUND: A range of neurohumoral substances have been suggested as diagnostic markers in heart failure. It is, however, undetermined which marker has the greatest diagnostic potential, and whether additional information is gained by a comprehensive neurohumoral evaluation. AIMS: The purpose of the study was to compare the value of epinephrine, norepinephrine, renin activity, aldosterone (ALDO), atrial (ANP) and brain (BNP) natriuretic peptides, arginine-vasopressin and endothelin (ENDO) as markers for left ventricular (LV) dimensions and ejection fraction (LVEF) in patients with systolic heart failure. METHODS: Forty-eight patients with symptomatic heart failure were examined with blood samples and magnetic resonance imaging along with 20 age and gender-matched normal controls. RESULTS: In multiple regression analyses, BNP was the strongest independent marker for LV end-diastolic (r=0.71, P<0.0001), and end-systolic (r=0.75, P<0.0001) volumes, myocardial mass (r=0.69, P<0.0001), and LVEF (r=-0.78, P<0.0001). ANP was a supplementary independent marker for LV end-diastolic (r=0.76, P<0.0001) and end-systolic (r=0.78, P<0.0001) (ANP and BNP combined) volumes, ENDO for myocardial mass [r=0.71, P<0.0001 (ENDO/BNP)], and ALDO for LVEF [r=-0.81, P<0.0001 (ALDO/BNP)]. CONCLUSION: BNP is the strongest marker for LV dimensions and LVEF in patients with systolic heart failure. However, a comprehensive neurohumoral evaluation may add some information to the diagnosis.

Precision of bolus thermodilution cardiac output measurements in patients with atrial fibrillation.

BACKGROUND: The precision of bolus thermodilution cardiac output measurements in patients with atrial fibrillation (AF) has not previously been determined. A priori we suspected that the precision would be lower in patients with AF than in patients with sinus rhythm (SR). Consequently, we also determined if the precision could be improved by injecting the thermal indicator into the right ventricle instead of the right atrium. METHODS: Cardiac output was determined as the average result of four injections of 10 ml of iced saline. Replicate measurements were performed with thermal indicator injections into the right atrium and ventricle. The coefficients of variation and the precisions were calculated. RESULTS: In the 25 patients with AF, mean cardiac output was 3.96 l min(-1) (range 2.4-7.4), the coefficient of variation 0.073 (95% CI +/- 0.011), and the precision 0.38 l min(-1) (95% CI +/- 0.14) with injection into the right atrium. In the 25 patients with SR, mean cardiac output was 4.73 l min(-1) (range 2.4-7.3), the coefficient of variation 0.047(95% CI +/- 0.006), and the precision 0.38 l min(-1) (95% CI +/- 0.14). In both groups, an agreement analysis demonstrated that the injection of indicator into the right ventricle resulted in a significantly higher cardiac output [AF+0.25 (95% CI +/- 0.15) l min(-1), SR+0.29 ( +/- 0.20) l min(-1)]. CONCLUSION: The coefficient of variation for cardiac output determinations is 55% higher in patients with AF. Two measurements, separated by time or intervention, must differ by 15% in AF patients and 9% in SR patients before one can be 95% confident that a real change has taken place.

Thermodilution cardiac output--are three injections enough?

BACKGROUND: Bolus thermodilution cardiac output measurements have been a mainstay in clinical monitoring of critically ill patients for more than 30 years. Usually the results of an arbitrarily chosen number (1-6) of thermal indicator injections are averaged to increase the reliability of the measurement. The number of injections needed to achieve a given level of precision has, however, not previously been systematically investigated. METHODS AND RESULTS: In 80 hemodynamically stable patients cardiac output was determined as the average of eight injections of 10 ml of iced saline. From the 638 measurements we examined the relationship between the number of thermal indicator injections and the precision of the resulting cardiac output estimate. Furthermore, the association between the number of injections and the least detectable difference among two sets of measurements was established. CONCLUSION: The current study shows that one needs to average the results of four injections to be 95% confident that the result is within 5% of the 'true' cardiac output and that two series of four measurements have to differ by at least 7% before one can be sure (95%) that a change in cardiac function has taken place.

Diagnostic and prognostic evaluation of left ventricular systolic heart failure by plasma N-terminal pro-brain natriuretic peptide concentrations in a large sample of the general population.

OBJECTIVE: To evaluate N-terminal pro-brain natriuretic peptide (NT-proBNP) as a diagnostic and prognostic marker for systolic heart failure in the general population. DESIGN: Study participants, randomly selected to be representative of the background population, filled in a heart failure questionnaire and underwent pulse and blood pressure measurements, electrocardiography, echocardiography, and blood sampling and were followed up for a median (range) period of 805 (60-1171) days. SETTING: Participants were recruited from four randomly selected general practitioners and were examined in a Copenhagen university hospital. PATIENTS: 382 women and 290 men in four age groups (50-59 (n = 174); 60-69 (n = 204); 70-79 (n = 174); > or = 80 years (n = 120)). MAIN OUTCOME MEASURES: Value of NT-proBNP in evaluating patients with symptoms of heart failure and impaired left ventricular (LV) systolic function; prognostic value of NT-proBNP for mortality and hospital admissions. RESULTS: In 38 (5.6%) participants LV ejection fraction (LVEF) was < or = 40%. NT-proBNP identified patients with symptoms of heart failure and LVEF < or = 40% with a sensitivity of 0.92, a specificity of 0.86, positive and negative predictive values of 0.11 and 1.00, and area under the curve of 0.94. NT-proBNP was the strongest independent predictor of mortality (hazard ratio (HR) = 5.70, p < 0.0001), hospital admissions for heart failure (HR = 13.83, p < 0.0001), and other cardiac admissions (HR = 3.69, p < 0.0001). Mortality (26 v 6, p = 0.0003), heart failure admissions (18 v 2, p = 0.0002), and admissions for other cardiac causes (44 v 13, p < 0.0001) were significantly higher in patients with NT-proBNP above the study median (32.5 pmol/l). CONCLUSIONS: Measurement of NT-proBNP may be useful as a screening tool for systolic heart failure in the general population.

The influence of age, sex and other variables on the plasma level of N-terminal pro brain natriuretic peptide in a large sample of the general population.

OBJECTIVE: To identify potentially confounding variables for the interpretation of plasma N-terminal pro brain natriuretic peptide (NT-proBNP). DESIGN: Randomly selected subjects filled in a heart failure questionnaire and underwent pulse and blood pressure measurements, ECG, echocardiography, and blood sampling. SETTING: Subjects were recruited from four Copenhagen general practices located in the same urban area and were examined in a Copenhagen University Hospital. PATIENTS: 382 women and 290 men in four age groups: 50-59 years (n = 174); 60-69 years (n = 204); 70-79 years (n = 174); and > 80 years (n = 120). MAIN OUTCOME MEASURES: Associations between the plasma concentration of NT-proBNP and a range of clinical variables. RESULTS: In the undivided study sample, female sex (p < 0.0001), greater age (p < 0.0001), increasing dyspnoea (p = 0.0001), diabetes mellitus (p = 0.01), valvar heart disease (p = 0.002), low heart rate (p < 0.0001), left ventricular ejection fraction < or = 45% (p < 0.0001), abnormal ECG (p < 0.0001), high log10[plasma creatinine] (p = 0.0009), low log10[plasma glycosylated haemoglobin A1c] (p = 0.0004), and high log10[urine albumin] (p < 0.0001) were independently associated with a high plasma log10[plasma NT-proBNP] by multiple linear regression analysis. CONCLUSIONS: A single reference interval for the normal value of NT-proBNP is unlikely to suffice. There are several confounders for the interpretation of a given NT-proBNP concentration and at the very least adjustment should be made for the independent effects of age and sex.

Sustained postinfarction myocardial oedema in humans visualised by magnetic resonance imaging.

OBJECTIVE: To demonstrate postinfarction myocardial oedema in humans with particular reference to the longitudinal course, using magnetic resonance imaging (MRI). DESIGN: Prospective observational study. Subjects were studied one week, one month, three months, six months, and one year after presenting with a myocardial infarct. SETTING: Cardiology and magnetic resonance departments in a Danish university hospital. PATIENTS: 10 patients (three women, seven men), mean (SEM) age 58.2 (3.20) years, with a first transmural myocardial infarct. MAIN OUTCOME MEASURES: Location and duration of postinfarction myocardial oedema. RESULTS: All patients had signs of postinfarction myocardial oedema. The magnetic resonance images were evaluated by two blinded procedures, employing two MRI and two ECG observers: (1) MRI determined oedema location was compared with the ECG determined site of infarction and almost complete agreement was found; (2) the time course of postinfarction myocardial oedema was explored semiquantitatively, using an image ranking procedure. Myocardial oedema was greatest at the initial examination one week after the infarction, with a gradual decline during the following months (Spearman's rank correlation analysis: rho(observer 1) = 0.94 (p < 0.0001) and rho(observer 2) = 0.97 (p < 0.0001)). The median duration of oedema was six months. CONCLUSIONS: Postinfarction myocardial oedema seems surprisingly long lasting. This observation is of potential clinical interest because the oedema may have prognostic significance.