Serum creatinine is an unreliable marker of renal function in patients undergoing heart transplantation.

BACKGROUND: Renal dysfunction is a common complication after heart transplantation (Htx). Glomerular filtration rate (GFR) can be assessed by various estimating equations (eGFR). We evaluated the correlation, agreement, and accuracy between eGFR and mGFR and the ability of eGFR to track changes in mGFR early after Htx. METHODS: A single-center prospective observational study on 55 patients undergoing Htx. Serum creatinine and mGFR (plasma clearance of Cr51-EDTA or iohexol) were measured preoperatively and on the fourth postoperative day. The accuracy of eGFR to predict true mGFR was calculated as the percentage of patients with an eGFR within 30% of mGFR (P30). The agreement between eGFR and mGFR was assessed according to Bland and Altman. A four-quadrant plot was made to evaluate the ability of eGFR to track changes in mGFR. RESULTS: The accuracy of eGFR to assess mGFR was 52%. The bias was 11.2 ± 17.4 mL/min/1.72 m2. The limits of agreement were -23.0 to 45.4 mL/min/1.72 m2 and the error 58%. The concordance rate between eGFR and mGFR was 72%. CONCLUSIONS: eGFR underestimated mGFR and the agreement between eGFR and mGFR was low with an unacceptably large between-group error and low accuracy. Furthermore, the ability of eGFR to assess changes in mGFR, postoperatively, was poor. Thus, the use of estimating equations from serum creatinine will not adequately assess renal function early after major heart surgery. To gain adequate information on renal function early after Htx, GFR needs to be measured, not estimated.

Three decades of heart transplantation: experience and long-term outcome.

Objectives. Heart transplantation (HTx) has become an established treatment option in patients with end-stage heart failure. The aim of this study was to report on long-term outcome over the past three decades. Design. Consecutive adult patients receiving first-time and isolated HTx from October 3, 1990, to November 2, 2020, at Rigshospitalet, Copenhagen, Denmark, were retrospectively evaluated. Data were obtained from the Scandinavian Transplant Registry and patient medical records. Recipients were grouped by time of transplantation (early era: 1990-1999; mid era: 2000-2009; recent era: 2010-2020). Results. A total of 384 recipients (77% men, median age 50 [IQR: 40-57]) were included. Median number of HTx procedures per year was 12 (10-14). Overall, 22% of patients were bridged to HTx with a mechanical circulatory support device. Median survival for the whole cohort was 13.8 years and improved numerically from the early era (12.6 years) to the mid era (14.9 years). Median survival conditional on survival to 1-year follow-up after HTx was 16.1 years. Survival probability by Kaplan-Meier method improved significantly from the mid to the recent era (log-rank p = .02). Conclusions. Heart transplantation remains an excellent treatment for selected patients with end-stage heart failure and long-term outcome has improved significantly over the past decades.

Cardiac arrhythmias in critically ill patients with coronavirus disease 2019: A retrospective population-based cohort study.

BACKGROUND: Coronavirus disease 2019 (COVID-19) may be associated with cardiac arrhythmias in hospitalized patients, but data from the ICU setting are limited. We aimed to describe the epidemiology of cardiac arrhythmias in ICU patients with COVID-19. METHODS: We conducted a multicenter, retrospective cohort study including all ICU patients with an airway sample positive for severe acute respiratory syndrome corona-virus 2 from March 1st to June 1st in the Capital Region of Denmark (1.8 million inhabitants). We registered cardiac arrhythmias in ICU, potential risk factors, interventions used in ICU and outcomes. RESULTS: From the seven ICUs we included 155 patients with COVID-19. The incidence of cardiac arrhythmias in the ICU was 57/155 (37%, 95% confidence interval 30-45), and 39/57 (68%) of these patients had this as new-onset arrhythmia. Previous history of tachyarrhythmias and higher disease severity at ICU admission were associated with cardiac arrhythmias in the adjusted analysis. Fifty-four of the 57 (95%) patients had supraventricular origin of the arrhythmia, 39/57 (68%) received at least one intervention against arrhythmia (eg amiodarone, IV fluid or magnesium) and 38/57 (67%) had recurrent episodes of arrhythmia in ICU. Patients with arrhythmias in ICU had higher 60-day mortality (63%) as compared to those without arrhythmias (39%). CONCLUSION: New-onset supraventricular arrhythmias were frequent in ICU patients with COVID-19 and were related to previous history of tachyarrhythmias and severity of the acute disease. The mortality was high in these patients despite the frequent use of interventions against arrhythmias.

COVID-19 Assessment with Bedside Lung Ultrasound in a Population of Intensive Care Patients Treated with Mechanical Ventilation and ECMO.

The COVID-19 pandemic has increased the need for an accessible, point-of-care and accurate imaging modality for pulmonary assessment. COVID-19 pneumonia is mainly monitored with chest X-ray, however, lung ultrasound (LUS) is an emerging tool for pulmonary evaluation. In this study, patients with verified COVID-19 disease hospitalized at the intensive care unit and treated with ventilator and extracorporal membrane oxygenation (ECMO) were evaluated with LUS for pulmonary changes. LUS findings were compared to C-reactive protein (CRP) and ventilator settings. Ten patients were included and scanned the day after initiation of ECMO and thereafter every second day until, if possible, weaned from ECMO. In total 38 scans adding up to 228 cineloops were recorded and analyzed off-line with the use of a constructed LUS score. The study indicated that patients with a trend of lower LUS scores over time were capable of being weaned from ECMO. LUS score was associated to CRP (R = 0.34; p < 0.03) and compliance (R = 0.60; p < 0.0001), with the strongest correlation to compliance. LUS may be used as a primary imaging modality for pulmonary assessment reducing the use of chest X-ray in COVID-19 patients treated with ventilator and ECMO.

Variation in Time to Peak Values for Different Lung Function Parameters After Double Lung Transplantation.

BACKGROUND: Establishment of baseline values for forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), or total lung capacity (TLC) is required when diagnosing and phenotyping chronic lung allograft dysfunction after lung transplant. It is generally accepted that the baseline (peak) values of these parameters occur simultaneously, but this assumption has not been substantiated for TLC. METHODS: All lung function measurements in all double lung transplant recipients from a single center in the period from 1992-2014 were included. Time to baseline FEV1 was assessed according to standards from the International Society for Heart and Lung Transplantation, and time to peak FVC, TLC, and diffusion capacity for carbon monoxide were evaluated. RESULTS: A total of 288 double lung transplants surviving more than 3 months after transplant were included. Baseline FEV1 occurred at a median of 0.77 years post transplant and was statistically different from median times to the peak FVC (1.02 years), to peak TLC (1.37 years), and to peak diffusion capacity for carbon monoxide 1.04 years post transplant (all log-rank P < .001). At the time of baseline FEV1, FVC, and TLC were at a mean of 96% and 95% of their peak values, respectively. CONCLUSION: The peak lung function is reached at different time points for different parameters post transplant with FEV1 baseline occurring first. For most patients values of FVC and TLC obtained at time for baseline FEV1 is a good estimate of peak values, but in a small percentage of patients this procedure may jeopardize phenotyping of chronic lung allograft dysfunction based solely on lung function parameters.

Vector Flow Imaging of the Ascending Aorta in Patients with Tricuspid and Bicuspid Aortic Valve Stenosis Treated with Biological and Mechanical Implants.

Aortic valve stenosis (AS) is treated with biological prostheses (BPs) and mechanical prostheses (MPs). Vector flow imaging (VFI), an angle-independent ultrasound method, can quantify flow complexity (vector concentration (VC)) and secondary rotation (SR). Ten patients (mean age: 70.7 y) with tricuspid AS scheduled for BPs, 10 patients (mean age: 56.2 y) with bicuspid AS scheduled for MPs and 10 patients (mean age: 63.9 y) with normal aortic valves were scanned intra-operatively on the ascending aorta with VFI and conventional spectral Doppler. Bicuspid AS (peak systolic velocity (PSV): 380.9 cm/s, SR: 16.7 Hz, VC: 0.21) had more complex flow (p < 0.02) than tricuspid AS (PSV: 346.1 cm/s, SR: 17.1 Hz, VC: 0.33). Both groups had more complex and faster flow (p < 0.0001) than normal aortic valve patients (PSV: 124.0 cm/s, SR: 4.3 Hz, VC: 0.79). VC (r = 0.87) and SR (r = 0.89) correlated to PSV. After surgery, flow parameters changed (p < 0.0001) for patients with MPs (PSV: 250.4 cm/s, SR: 9.8 Hz, VC: 0.54) and BPs (PSV: 232.4 cm/s, SR: 12.5 Hz, VC: 0.61), with MPs having slower SR (p < 0.01). None of the implants had normal flow (p < 0.0001). In conclusion, VFI can provide new flow parameters for AS and implant assessment.

Pediatric Transthoracic Cardiac Vector Flow Imaging - A Preliminary Pictorial Study.

Purpose Conventional pediatric echocardiography is crucial for diagnosing congenital heart disease (CHD), but the technique is impaired by angle dependency. Vector flow imaging (VFI) is an angle-independent noninvasive ultrasound alternative for blood flow assessment and can assess complex flow patterns not visible on conventional Doppler ultrasound. Materials and Methods 12 healthy newborns and 3 infants with CHD were examined with transthoracic cardiac VFI using a conventional ultrasound scanner and a linear array. Results VFI examinations revealed common cardiac flow patterns among the healthy newborns, and flow changes among the infants with CHD not previously reported with conventional echocardiography. Conclusion For assessment of cardiac flow in the normal and diseased pediatric heart, VFI may provide additional information compared to conventional echocardiography and become a useful diagnostic tool.

Tricuspid annular plane systolic excursion is significantly reduced during uncomplicated coronary artery bypass surgery: A prospective observational study.

OBJECTIVES: Longitudinal shortening constitutes most of the right ventricle (RV) contraction in the normal heart. However, after even uncomplicated cardiac surgery with preserved RV function a significant and sustained decrease in longitudinal contraction expressed as a reduction in tricuspid annular plane systolic excursion (TAPSE) has been observed. Why and exactly when this happens remains unsettled. The aim of this study was to evaluate the magnitude and timing of changes in TAPSE in relation to sternotomy, pericardial opening, cardiopulmonary bypass (CPB), and chest closure. METHODS: Fifty patients with normal preoperative ejection fraction and no valvulopathy, who underwent coronary artery bypass grafting with the use of CPB, were included. TAPSE was assessed using transthoracic echocardiography (TTE) at baseline and immediately after chest closure. Transesophageal echocardiography was performed at the following time points: after (1) anesthesia induction and transthoracic echocardiography; (2) sternotomy; (3) pericardiotomy; (4) completion of CPB; and (5) chest closure. RESULTS: TAPSE was significantly reduced to approximately half of its initial value in all patients (from 22 [95% confidence interval, 21-23 mm] after anesthesia induction to 9 [95% confidence interval, 8-10 mm] after chest closure). No change was seen after pericardiotomy. The most prominent reduction (30%-40%) was observed after weaning from CPB. An additional significant decrease of 13% to 16% was seen after chest closure. CONCLUSIONS: TAPSE was consistently reduced to approximately half of its initial value after uncomplicated coronary artery bypass grafting surgery. The reduction happened mainly after weaning from CPB, possibly reflecting conformational change of the RV.

Automatic Detection of B-Lines in In Vivo Lung Ultrasound.

This paper proposes an automatic method for accurate detection and visualization of B-lines in ultrasound lung scans, which provides a quantitative measure for the number of B-lines present. All the scans used in this study were acquired using a BK3000 ultrasound scanner (BK Ultrasound, Herlev, Denmark) driving a 5.5-MHz linear transducer (BK Ultrasound). Four healthy subjects and four patients, after major surgery with pulmonary edema, were scanned at four locations on each lung for B-line examination. Eight sequences of 50 frames were acquired for each subject yielding 64 sequences in total. The proposed algorithm was applied to all 3200 in-vivo lung ultrasound images. The results showed that the average number of B-lines was 0.28±0.06 (Mean±Std) in scans belonging to the patients compared to 0.03 ± 0.06 (Mean ± Std) in the healthy subjects. Also, the Mann-Whitney test showed a significant difference between the two groups with the p -value of 0.015, and indicating that the proposed algorithm was able to differentiate between the healthy volunteers and the patients. In conclusion, the method can be used to automatically and to quantitatively characterize the distribution of B-lines for diagnosing pulmonary edema.

Lung transplantation after ex vivo lung perfusion in two Scandinavian centres.

OBJECTIVES: We reviewed our combined clinical outcome in patients who underwent lung transplantation after ex vivo lung perfusion (EVLP) and compared it to the contemporary control group. METHODS: At 2 Scandinavian centres, lungs from brain-dead donors, not accepted for donation but with potential for improvement, were subjected to EVLP (n = 61) and were transplanted if predefined criteria were met. Transplantation outcome was compared with that of the contemporary control group consisting of patients (n = 271) who were transplanted with conventional donor lungs. RESULTS: Fifty-four recipients from the regular waiting list underwent transplantation with lungs subjected to EVLP (1 bilateral lobar, 7 single and 46 double). In the EVLP and control groups, arterial oxygen tension/inspired oxygen fraction ratio at arrival in the intensive care unit (ICU) was 30 ± 14 kPa compared to 36 ± 14 (P = 0.005); median time to extubation was 18 h (range 2-912) compared to 7 (range 0-2280) (P = 0.002); median ICU length of stay was 4 days (range 2-65) compared to 3 days (range 1-156) (P = 0.002); Percentage of expected forced expiratory volume at 1s (FEV1.0%) at 1 year was 75 ± 29 compared to 81 ± 26 (P = 0.18); and the 1-year survival rate was 87% [confidence interval (CI) 82-92%] compared to 83% (CI 81-85), respectively. Follow-up to a maximum of 5 years did not show any significant difference in survival between groups (log rank, P = 0.63). CONCLUSIONS: Patients transplanted with lungs after EVLP showed outcomes comparable to patients who received conventional organs at medium-term follow-up. Although early outcome immediately after transplantation showed worse lung function in the EVLP group, no differences were observed at a later stage, and we consider EVLP to be a safe method for increasing the number of transplantable organs.

Peripheral measurements of venous oxygen saturation and lactate as a less invasive alternative for hemodynamic monitoring.

BACKGROUND: Peripheral measurement of venous oxygen saturation and lactate is a less invasive alternative to monitor tissue oxygenation as compared to measurements from a central venous catheter. However, there is a lack of evidence to support the use of peripheral measurements. In this study, we investigated the agreement between central and peripheral venous oxygen saturation and lactate. METHODS: We conducted a prospective observational study including 115 patients who underwent elective cardiac surgery between April and May 2015 at Rigshospitalet, Copenhagen, Denmark. Measurements were obtained simultaneously at induction of anaesthesia, upon arrival in the ICU and 3-4 h postoperatively. Bias and trending ability was identified using Bland-Altman analysis and a four-quadrant plot. RESULTS: Bias was 13.37% for venous oxygen saturation preoperatively (95% CI: 11.52-15.22, LoA: ±19.10, PE: 22.08%), 11.29% at arrival to the ICU (95% CI: 8.81-13.77, LoA: ±25.10, PE: 32.39%) and 16.49% at 3-4 h postoperatively (95% CI: 14.16-18.82, LoA: ±21.20, PE: 26.82%). A four-quadrant plot demonstrated an 89% concordance. Central and peripheral lactate showed a bias of 0.14 mmol/L preoperatively (95% CI: 0.11-0.17, LoA: ±0.30, PE: 32.08%), 0.16 mmol/L at arrival to ICU (95% CI: 0.09-0.23, LoA: ±0.70, PE: 38.88%) and 0.23 mmol/L at 3-4 h postoperatively (95% CI: 0.11-0.35, LoA: ±0.50, 25.18%). DISCUSSION: Measurements of peripheral oxygen saturation and lactate may be valuable in an emergency setting, avoiding unnecessary and time consuming application of a CVC. CONCLUSION: We found a high bias but an acceptable trending ability between central and peripheral venous oxygenation. Central and peripheral lactate had excellent agreement. Further studies are necessary to validate the use of peripheral venous samples to identify patients at risk of impaired tissue oxygenation.

Comparing Methods for Cardiac Output: Intraoperatively Doppler-Derived Cardiac Output Measured With 3-Dimensional Echocardiography Is Not Interchangeable With Cardiac Output by Pulmonary Catheter Thermodilution.

BACKGROUND: Estimation of cardiac output (CO) is essential in the treatment of circulatory unstable patients. CO measured by pulmonary artery catheter thermodilution is considered the gold standard but carries a small risk of severe complications. Stroke volume and CO can be measured by transesophageal echocardiography (TEE), which is widely used during cardiac surgery. We hypothesized that Doppler-derived CO by 3-dimensional (3D) TEE would agree well with CO measured with pulmonary artery catheter thermodilution as a reference method based on accurate measurements of the cross-sectional area of the left ventricular outflow tract. METHODS: The primary aim was a systematic comparison of CO with Doppler-derived 3D TEE and CO by thermodilution in a broad population of patients undergoing cardiac surgery. A subanalysis was performed comparing cross-sectional area by TEE with cardiac computed tomography (CT) angiography. Sixty-two patients, scheduled for elective heart surgery, were included; 1 was subsequently excluded for logistic reasons. Inclusion criteria were coronary artery bypass surgery (N = 42) and aortic valve replacement (N = 19). Exclusion criteria were chronic atrial fibrillation, left ventricular ejection fraction below 0.40 and intracardiac shunts. Nineteen randomly selected patients had a cardiac CT the day before surgery. All images were stored for blinded post hoc analyses, and Bland-Altman plots were used to assess agreement between measurement methods, defined as the bias (mean difference between methods), limits of agreement (equal to bias ± 2 standard deviations of the bias), and percentage error (limits of agreement divided by the mean of the 2 methods). Precision was determined for the individual methods (equal to 2 standard deviations of the bias between replicate measurements) to determine the acceptable limits of agreement. RESULTS: We found a good precision for Doppler-derived CO measured by 3D TEE, but although the bias for Doppler-derived CO by 3D compared to thermodilution was only 0.3 L/min (confidence interval, 0.04-0.58), there were wide limits of agreement (-1.8 to 2.5 L/min) with a percentage error of 55%. Measurements of cross-sectional area by 3D TEE had low bias of -0.27 cm (confidence interval, -0.45 to -0.08) and a percentage error of 18% compared to cardiac CT angiography. CONCLUSIONS: Despite low bias, the wide limits of agreement of Doppler-derived CO by 3D TEE compared to CO by thermodilution will limit clinical application and can therefore not be considered interchangeable with CO obtained by thermodilution. The lack of agreement is not explained by lack of agreement of the 3D technique.

High-dose methylprednisolone in video-assisted thoracoscopic surgery lobectomy: a randomized controlled trial.

OBJECTIVES: The optimal postoperative analgesic strategy after video-assisted thoracoscopic surgery lobectomy remains undetermined. We hypothesized that high-dose preoperative methylprednisolone (MP) would improve analgesia compared to placebo. METHODS: A total of 120 adult patients were randomized equally to 125 mg MP or placebo before the start of their elective video-assisted thoracoscopic surgery lobectomy. Group allocation was blinded to patients, investigators and caregivers, and all patients received standardized multimodal, opioid-sparing analgesia. Our primary outcome was area under the curve on a numeric rating scale from 0 to 10, for pain scores on the day of surgery and on postoperative days 1 and 2. Clinical follow-up was 2-3 weeks, and telephone follow-up was 12 weeks after surgery. RESULTS: Ninety-six patients were included in the primary analysis. Methylprednisolone significantly decreased median pain scores on the day of surgery: at rest (numeric rating scale 1.6 vs 2.0, P = 0.019) and after mobilization to a sitting position (numeric rating scale 1.7 vs 2.5, P = 0.004) but not during arm abduction and coughing (P = 0.052 and P = 0.083, respectively). Nausea and fatigue were reduced on the day of surgery (P = 0.04 and 0.03), whereas no outcome was improved on postoperative Days 1 and 2. Methylprednisolone did not increase the risk of complications but increased blood glucose levels on the day of surgery (P < 0.0001). CONCLUSIONS: High-dose preoperative MP significantly reduced pain at rest and after mobilization to a sitting position on the day of surgery, without later analgesic effects. Nausea and fatigue were improved without side effects, except transient higher postoperative blood glucose levels. CLINICAL TRIAL REGISTRATION: Registered at clinicaltrialsregister.eu [7 November 2012, EudraCT 2012-004451-37; https://www.clinicaltrialsregister.eu/ctr-search/trial/2012-004451-37/DK].

[Extracorporeal cardiopulmonary resuscitation for patients with out-of-hospital refractory cardiac arrest].

Out-of-hospital cardiac arrest is associated with high mortality and morbidity. Treatment options remain few in refractory cases, but extracorporeal cardiopulmonary resuscitation (eCPR) is increasingly applied to improve the outcome. This article summarizes the use, experience and outcome of eCPR focussing on current knowledge of criteria for selection of relevant patients for treatment.

Aortic Valve Stenosis Increases Helical Flow and Flow Complexity: A Study of Intra-Operative Cardiac Vector Flow Imaging.

Aortic valve stenosis alters blood flow in the ascending aorta. Using intra-operative vector flow imaging on the ascending aorta, secondary helical flow during peak systole and diastole, as well as flow complexity of primary flow during systole, were investigated in patients with normal, stenotic and replaced aortic valves. Peak systolic helical flow, diastolic helical flow and flow complexity during systole differed between the groups (p < 0.0001), and correlated to peak systolic velocity (R = 0.94, 0.87 and 0.88, respectively). The study indicates that aortic valve stenosis increases helical flow and flow complexity, which are measurable with vector flow imaging. For assessment of aortic stenosis and optimization of valve surgery, vector flow imaging may be useful.

Increased Intracranial Pressure during Hemodialysis in a Patient with Anoxic Brain Injury.

Dialysis disequilibrium syndrome (DDS) is a serious neurological complication of hemodialysis, and patients with acute brain injury are at increased risk. We report a case of DDS leading to intracranial hypertension in a patient with anoxic brain injury and discuss the subsequent dialysis strategy. A 13-year-old girl was admitted after prolonged resuscitation from cardiac arrest. Computed tomography (CT) revealed an inferior vena cava aneurysm and multiple pulmonary emboli as the likely cause. An intracranial pressure (ICP) monitor was inserted, and, on day 3, continuous renal replacement therapy (CRRT) was initiated due to acute kidney injury, during which the patient developed severe intracranial hypertension. CT of the brain showed diffuse cerebral edema. CRRT was discontinued, sedation was increased, and hypertonic saline was administered, upon which ICP normalized. Due to persistent hyperkalemia and overhydration, ultrafiltration and intermittent hemodialysis were performed separately on day 4 with a small dialyzer, low blood and dialysate flow, and high dialysate sodium content. During subsequent treatments, isolated ultrafiltration was well tolerated, whereas hemodialysis was associated with increased ICP necessitating frequent pauses or early cessation of dialysis. In patients at risk of DDS, hemodialysis should be performed with utmost care and continuous monitoring of ICP should be considered.

Transesophageal Doppler reliably tracks changes in cardiac output in comparison with intermittent pulmonary artery thermodilution in cardiac surgery patients.

In this study a comparison of cardiac output (CO) measurements obtained with CardioQ transesophageal Doppler (TED) and pulmonary artery catheter (PAC) thermodilution (TD) technique was done in a systematic set-up, with induced changes in preload, afterload and heart rate. Twenty-five patients completed the study. Each patient were placed in the following successive positions: (1) supine, (2) head-down tilt, (3) head-up tilt, (4) supine, (5) supine with phenylephrine administration, (6) pace heart rate 80 beats per minute (bpm), (7) pace heart rate 110 bpm. The agreement of compared data was investigated by Bland-Altman plots, and to assess trending ability a four quadrants plot and a polar plot were constructed. Both methods showed an acceptable precision 6.4 % (PAC TD) and 12.8 % (TED). In comparison with PAC TD, the TED was associated with a mean bias in supine position of -0.30 l min-1 (95 % CI -0.88; 0.27), wide limits of agreement, a percentage error of 69.5 %, and a trending ability with a concordance rate of 92 %, angular bias of 1.1° and a radial sector size of 40.0° corresponding to an acceptable trending ability. In comparison with PAC TD, the CardioQ TED showed a low mean bias, wide limits of agreement and a larger percentage error than should be expected from the precision of the two methods. However, an acceptable trending ability was found. Thus, the CardioQ TED should not replace CO measurements done by PAC TD, but could be a valuable tool in guiding therapy.

Vector Flow Imaging Compared with Conventional Doppler Ultrasound and Thermodilution for Estimation of Blood Flow in the Ascending Aorta.

Transverse oscillation (TO) is a real-time ultrasound vector flow method implemented on a commercial scanner. The TO setup was examined on a flowrig with constant and pulsatile flow. Subsequently, 25 patients undergoing cardiac bypass surgery were scanned intraoperatively with TO on the ascending aorta and compared to transesophageal echocardiography (TEE) and pulmonary artery catheter thermodilution (PACTD). On the flowrig, TO had a precision of 5.5%, 9.4% and 14.7%, a percentage error of 18.2%, 14.6% and 40.7%, and a mean bias of 0.4 cm/s, 36.8 ml/min and 32.4 ml/min for velocity and flow rate (constant and pulsatile) estimation. The correlation coefficients for all flowrig evaluations were 0.99 indicating systematic bias. After bias correction, the percentage error was reduced to 11.5%, 12.6% and 15.9% for velocity and flow rate (constant and pulsatile) estimation. In the in vivo setup, TO, TEE, and PACTD had a precision of 21.9%, 13.7%, and 12.0%. TO compared with TEE and PACTD had a mean bias of 12.6 cm/s and -0.08 l/min, and a percentage error of 23.4%, and 36.7%, respectively. The percentage error was reduced to 22.9% for the TEE comparison, but increased to 43.8% for the PACTD comparison, after correction for the systematic bias found in the flowrig. TO is a reliable and precise method for velocity and flow rate estimation on a flowrig. However, TO with the present setup, is not interchangeable with PACTD for cardiac volume flow estimation, but is a reliable and precise angle-independent ultrasound alternative for velocity estimation of cardiac flow.

Intra-Operative Vector Flow Imaging Using Ultrasound of the Ascending Aorta among 40 Patients with Normal, Stenotic and Replaced Aortic Valves.

Stenosis of the aortic valve gives rise to more complex blood flows with increased velocities. The angle-independent vector flow ultrasound technique transverse oscillation was employed intra-operatively on the ascending aorta of (I) 20 patients with a healthy aortic valve and 20 patients with aortic stenosis before (IIa) and after (IIb) valve replacement. The results indicate that aortic stenosis increased flow complexity (p < 0.0001), induced systolic backflow (p < 0.003) and reduced systolic jet width (p < 0.0001). After valve replacement, the systolic backflow and jet width were normalized (p < 0.52 and p < 0.22), but flow complexity was not (p < 0.0001). Flow complexity (p < 0.0001), systolic jet width (p < 0.0001) and systolic backflow (p < 0.001) were associated with peak systolic velocity. The study found that aortic stenosis changes blood flow in the ascending aorta and valve replacement corrects some of these changes. Transverse oscillation may be useful for assessment of aortic stenosis and optimization of valve surgery.