Validation of MRI assessment of foot perfusion for improving treatment of patients with peripheral artery disease.

INTRODUCTION: Information on tissue perfusion in the foot is important when treating patients with chronic limb-threatening ischemia. This study aims to test the reliability of different magnetic resonance sequences when measuring perfusion in the foot. METHODS: Sixteen healthy volunteers had their right foot scanned in a test/retest study with six different magnetic resonance sequences (BOLD, multi-echo gradient echo (mGRE), 2D and 3D pCASL, PASL FAIR, and DWI with intravoxel incoherent motion (IVIM) with quantitative measurements of perfusion. For five sequences, cuff-induced ischemia followed by a hyperactive response was measured. Images of the feet were segmented into angiosomes and perfusion data were extracted from the five angiosomes. RESULTS: BOLD, PASL FAIR, mGRE, and DWI with IVIM had low mean differences between the first and second scans, while the results of 2D and 3D pCASL had the highest differences. Based on a paired t-test, BOLD, and FAIR were able to distinguish between perfusion and no perfusion in all angiosomes with p-values below 0.01. This was not the case with 2D and 3D pCASL with p-values above 0.05 in all angiosomes. The mGRE could not distinguish between perfusion and no perfusion in the lateral side of the foot. CONCLUSION: BOLD, mGRE, pASL FAIR, and DWI with IVIM seem to give more robust results compared to 2D and 3D pCASL. Further studies on patients with peripheral artery disease should explore if the sequences can have clinical relevance when assessing tissue ischemia and results of revascularization. IMPLICATIONS FOR PRACTICE: This study provides knowledge that could be used to improve the diagnosis of patient with chronic limb-threatening ischemia to explore tissue perfusion.

Reoperation after antireflux surgery: a population-based cohort study.

BACKGROUND: Antireflux surgery for gastro-oesophageal reflux disease (GORD) and/or hiatal hernia is effective. Between 10 and 20 per cent of patients undergo reoperation for recurrent symptoms. Most studies are undertaken in a single centre and possibly underestimate the rate of reoperation. The aim of this nationwide population-based cohort study was to investigate long-term reoperation rates after antireflux surgery. METHODS: This study included patients who underwent antireflux surgery between 2000 and 2017 in Denmark, and were registered in the Danish nationwide health registries. Reoperation rates were calculated for 1, 5, 10 and 15 years after the primary antireflux operation for GORD and/or hiatal hernia. Duration of hospital stay, 30- and 90-day mortality and morbidity, and use of endoscopic pneumatic dilatation were assessed. RESULTS: This study included a total of 4258 antireflux procedures performed in 3717 patients. Some 3252 patients had only primary antireflux surgery and 465 patients underwent reoperation. The 1-, 5-, 10- and 15-year rates of repeat antireflux surgery were 3·1, 9·3, 11·7 and 12·8 per cent respectively. Thirty- and 90-day mortality rates were similar for primary surgery (0·4 and 0·6 per cent respectively) and reoperations. The complication rate was higher for repeat antireflux surgery (7·0 and 8·3 per cent at 30 and 90 days respectively) than primary operation (3·4 and 4·8 per cent). A total of 391 patients (10·5 per cent of all patients) underwent endoscopic dilatation after primary antireflux surgery, of whom 95 (24·3 per cent) had repeat antireflux surgery. CONCLUSION: In this population-based study in Denmark, the reoperation rate 15 years after antireflux surgery was 12·8 per cent. Reoperations were associated with more complications.

ANTECEDENTES: La cirugía antirreflujo es efectiva en el tratamiento de la enfermedad por reflujo gastroesofágico (gastro-oesophageal reflux disease, GORD) y/o de la hernia de hiato. Entre el 10% y el 20% de los pacientes tienen que ser reoperados por recidiva de los síntomas. La mayoría de los estudios son unicéntricos, lo que posiblemente infravalora la tasa de reintervenciones. El objetivo de este estudio de cohortes de base poblacional nacional fue investigar las tasas de reintervenciones a largo plazo tras la cirugía antirreflujo. MÉTODOS: Este estudio incluyó pacientes sometidos a cirugía antirreflujo entre 2000 y 2017 en Dinamarca y que fueron registrados en los registros nacionales de salud daneses. Se calcularon las tasas de reintervención para 1, 5, 10 y 15 años tras la operación antirreflujo primaria por GORD y/o hernia de hiato. Se evaluaron la duración de la estancia hospitalaria, la morbilidad y mortalidad a 30 y 90 días, y el uso de dilatación neumática endoscópica. RESULTADOS: Este estudio incluyó un total de 4.258 procedimientos antirreflujo efectuados en 3.717 pacientes. Unos 3.252 pacientes fueron sometidos únicamente a cirugía antirreflujo primaria y 465 pacientes a una reintervención. Las tasas de cirugía antirreflujo de revisión a 1, 5, 10 y 15 años fueron del 3,1%, 9,3%, 11,7% y 12,9%, respectivamente. La mortalidad a los 30 y 90 días fue similar cuando se comparó cirugía primaria y reintervenciones (mortalidad a 30 días 0,4% y 90 días 0,6% versus 0% y 0,4%, respectivamente). La tasa de complicaciones fue más elevada para la cirugía antirreflujo de revisión en comparación con la cirugía primaria: tasa de complicaciones a los 30 días 7,0%, 90 días 8,3% versus 30 días 3,4% y 90 días 4,8%, respectivamente. Un total de 391 pacientes (10,5% de todos los pacientes) fueron sometidos a dilatación endoscópica tras la cirugía antirreflujo primaria y 95 de 391 pacientes (24,3%) precisaron cirugía antirreflujo de revisión. CONCLUSIÓN: En este estudio de base poblacional en Dinamarca, la tasa de reintervención a los 15 años tras cirugía antirreflujo fue del 12,9%. Las reintervenciones se asociaron con más complicaciones.

Five-year outcomes following a randomized trial of femorofemoral and femoropopliteal bypass grafting with heparin-bonded or standard polytetrafluoroethylene grafts.

BACKGROUND: Cohort studies suggest superior long-term patency of luminal heparin-bonded polytetrafluoroethylene (Hb-PTFE) bypass grafts compared with standard PTFE grafts. The aim of this study was to compare the outcomes of Hb-PTFE grafts with those of standard PTFE grafts 5 years after a randomized trial. METHODS: Patients with intermittent claudication or critical limb ischaemia requiring femorofemoral or femoropopliteal bypass grafting were randomized in a clinical trial of Hb-PTFE versus standard PTFE in 11 Scandinavian centres between 2005 and 2009. Patients were followed up for 5 years with clinical assessment and surveillance Duplex ultrasound imaging. The primary endpoint of this study was primary patency. Secondary endpoints included major amputation and mortality. RESULTS: Overall, 569 patients were enrolled in the randomized trial. Some 552 had follow-up data available for analysis of the primary outcome. Use of Hb-PTFE significantly improved patency by 37 per cent at 2 years, but 5 years after randomization there was no difference in primary patency (adjusted hazard ratio (HR) 0·95, 95 per cent c.i. 0·71 to 1·28; P = 0·748). In patients with critical limb ischaemia the use of Hb-PTFE reduced the 5-year risk of loss of primary patency by 37 per cent (HR 0·63, 0·40 to 0·99; P = 0·049). CONCLUSION: In this study there was no difference in primary graft patency between Hb-PTFE and standard PTFE grafts. Patients receiving Hb-PTFE grafts for critical limb ischaemia were more likely to have a patent graft at 5 years than those with standard PTFE grafts.

Editor's Choice - High Heritability of Liability to Abdominal Aortic Aneurysms: A Population Based Twin Study.

OBJECTIVE: First degree relatives of patients with abdominal aortic aneurysm (AAA) have an increased risk of developing AAA; however, despite intensive investigation, the specific genetic factors involved in the development of the disease are still largely unknown. In twin studies the influence of genetic and environmental factors can be assessed by comparing concordance rates between monozygotic (MZ) and dizygotic (DZ) twins. Higher phenotypic similarity between MZ than DZ twins indicates a genetic attribution to the etiology. The objective of this study was to investigate the heritability of AAA among Danish twins using concordance rates and heritability estimates. METHODS: The Danish Twin Registry was used to identify all Danish twin pairs (born 1880-1971) where both twins were alive on January 1, 1977. AAA cases were then identified using the National Patient Registry and the Registry of Cause of Death. Probandwise concordance rates were calculated and heritability estimated using structural equation modeling. RESULTS: The study identified 414 twins with AAA; 69.8% (289/414) were men and 30.2% (125/414) women. The probandwise concordance rate in MZ twins was 30% (95% CI 20.3-43.3%) compared with 12% (95% CI 7.0-20.1%) in DZ twins. In the heritability analysis 77% (95% CI 67-85%) of the total variance was explained by additive genetic components and 23% (95% CI 15-33%) was explained by non-shared environmental factors. CONCLUSIONS: The probandwise concordance rate was found to be 2.5 times higher in MZ compared with DZ twins. An overall heritability of 77% was determined.

Abdominal aortic diameter is increased in males with a family history of abdominal aortic aneurysms: results from the Danish VIVA-trial.

OBJECTIVE: To investigate, at a population level, whether a family history of abdominal aortic aneurysm (AAA) is independently related to increased aortic diameter and prevalence of AAA in men, and to elucidate whether the mean aortic diameter and the prevalence of AAA are different between participants with male and female relatives with AAA. DESIGN: Observational population-based cross-sectional study. MATERIALS: 18,614 male participants screened for AAA in the VIVA-trial 2008-2011 with information on both family history of AAA and maximal aortic diameter. METHODS: Standardized ultrasound scan measurement of maximum antero-posterior aortic diameter. Family history obtained by questionnaire. Multivariate regression analysis was used to test for confounders: age, sex, smoking, comorbidity and medication. RESULTS: From the screened cohort, 569 participants had at least one first degree relative diagnosed with AAA, and 38 had AAA. Participants with a family history of AAA (+FH) had a significantly larger mean maximum aortic diameter (20.50 mm) compared with participants without family history of AAA (-FH) (19.07 mm, p < .0001), and +FH with female relatives with AAA had significantly larger mean maximum aortic diameter (21.8 mm) than +FH with male relatives (19.9 mm, p = .007). Furthermore the prevalence of AAA was significantly higher among +FH (6.7%) compared with -FH (3.0%) with an odds ratio (OR) of 2.2 (95% CI: 1.6 to 3.2, p < .001) and +FH with female relatives with AAA had a more than two and a half times increased prevalence of AAA compared with +FH with male relatives with AAA with an OR of 2.65. CONCLUSIONS: First-degree male relatives of AAA patients have wider aortas and a twofold higher prevalence of AAA compared with the age adjusted background population. The prevalence of AAA was markedly higher in participants related to female, rather than male, patients with AAA.

Flow during exercise in the total cavopulmonary connection measured by magnetic resonance velocity mapping.

OBJECTIVE: To measure caval and pulmonary flows at rest and immediately after exercise in patients with total cavopulmonary connection (TCPC). DESIGN: An observational study using the patients as their own controls. SETTING: Using a combination of magnetic resonance (MR) phase contrast techniques and an MR compatible bicycle ergometer, blood flow was measured in the superior vena cava, the tunnel from the inferior vena cava, and in the left and right pulmonary arteries during rest and on exercise (0.5 W/kg and 1.0 W/kg). PATIENTS: Eleven patients aged 11.4 (4.6) years (mean (SD)) were studied 6.3 (3.8) years after TCPC operation. MAIN OUTCOME MEASURES: Volume flow measured in all four branches of the TCPC connection during rest and exercise. RESULTS: Systemic venous return (inferior vena cava plus superior vena cava) increased from 2.5 (0.1) l/min/m2 (mean (SEM)) to 4.4 (0.4) l/min/m2 (p < 0.05) during exercise, with even distribution to the two pulmonary arteries. At rest, inferior vena caval flow was higher than superior vena caval flow, at 1.4 (0.1) v 1.1 (0.1) l/min/m2 (p < 0.05). During exercise, inferior vena caval flow doubled (to 3.0 (0.3) l/min/m2) while superior vena caval flow only increased slightly (to 1.4 (0.1) l/min/m2) (p < 0.05). The increased blood flow mainly reflected an increase in heart rate. The inferior vena caval to superior vena caval flow ratio was 1.4 (0.1) at rest and increased to 1.8 (0.1) (p < 0.05) at 0.5 W/kg, and to 2.2 (0.2) at 1.0 W/kg (p < 0.05). CONCLUSIONS: Quantitative flow measurements can be performed immediately after exercise using MR techniques. Supine leg exercise resulted in a more than twofold increase in inferior vena caval flow. This was equally distributed to the two lungs, indicating that pulmonary resistance rather than geometry decides flow distribution in the TCPC circulation.

Serial magnetic resonance imaging of global and regional left ventricular remodeling during 1 year after acute myocardial infarction.

Biplane long-axis cine MRI was performed in 51 patients 1, 13, 26, and 52 weeks after their first AMI. LV mass index (LVMI) was significantly increased 1 week after AMI (84.3 +/- 16.9 vs. 68.1 +/- 11.4 g/m(2) controls, n = 48, p < 0.001), presumably owing to edema of the infarcted myocardium. Six months after AMI, LVMI decreased to 76.5 +/- 16.4 g/m(2), but had again augmented after 1 year (81.8 +/- 17.3 g/m(2), p < 0.05), suggesting late, compensatory left ventricular hypertrophy. In patients treated with primary percutaneous transluminal coronary angioplasty, LVMI decreased 5% over 1 year, while LVMI increased 10% in patients receiving thrombolysis (p < 0.05). In the entire population, the global increase in LVMI 1 year after AMI seemed to reflect global cavity dilatation with unchanged thickness of the vital myocardium. In conclusion, in patients receiving contemporary treatment, LV remodeling only partially complied with the classical patho-anatomical concept.

Biplane long-axis magnetic resonance imaging. Survey projections for rapid estimation of left ventricular mass and global function.

OBJECTIVE: To evaluate the accuracy and precision of biplane long-axis magnetic resonance imaging (MRI) and two-dimensional (2D)-echocardiography, for the assessment of left ventricular (LV) mass and volumes, with multislice short-axis MRI as reference standard. DESIGN: Forty-five cardiac patients and four volunteers with varying LV dilatation and hypertrophy were examined by biplane long-axis gradient-echo MRI, 2D-echocardiography, and multiple short-axis gradient-echo MRI. RESULTS: Compared with multislice MRI, the accuracy, i.e. the coefficient of variation (c.v.) of inter-method differences of measured variables, was median 15.7% for biplane MRI and 18.5% for 2D-echocardiography. The precision, expressed as the c.v. of repeated measurements, was median 8.5% for multislice MRI, 9.5% for biplane MRI and 12.4% for 2D-echocardiography. For the determination of LV mass index, MRI was significantly more precise (c.v.: 6.0-8.4%) than 2D-echocardiography (c.v.: 13.7-14.3%, p < 0.05). CONCLUSION: Biplane long-axis MRI is a fast and simplified method, offering the advantage of displaying anatomy and function in recognizable projections. For the estimation of LV mass and volumes, biplane MRI had an acceptable accuracy, and a precision that did not differ significantly from that of multislice MRI.

Motion correction for the quantification of mitral regurgitation using the control volume method.

Quantifying mitral regurgitation is difficult because of the complexity of the flow, geometry and motion of the mitral valve. In this paper a MRI compatible phantom was built incorporating a left ventricle and mitral valve motion. Valve motion was obtained using a pneumatic piston. The mitral valve was made regurgitant and the regurgitant volume quantified using a modified control volume method. The modification to the method was the addition of mitral motion correction. This was attained by moving the control volume in unison with the mitral valve and by correcting for this motion in the integration of velocity. This correction was found to be simple, in that it represented the volume swept out by the moving control surface. The measured regurgitant volume was compared to a second MR measurement using a single slice technique, made possible by the tubular construction of the phantom's left atrium. Regression analysis between these two methods produced a regression line of y = 0 + 1.02 x; R = 0.97; standard error of the estimate = 3.47 ml.

Magnetic resonance imaging seems safe in patients with intracoronary stents.

We elucidated whether exposure to cardiac magnetic resonance imaging (MRI) of patients with implanted intracoronary stents is associated with increased risk of stent-thrombosis, stent-restenosis, or other cardiovascular complications. Forty-seven patients admitted with acute myocardial infarction (AMI) were studied. Twenty-three were included in a serial cardiac MRI study, using 1.5-T scanners with standard gradient systems. The remaining patients were control subjects who were matched for age and gender with the MRI group. All patient had intracoronary stents implanted in connection with primary angioplastic treatment (PTCA) of AMI (n = 21), secondary PTCA procedures due to recurrent angina (n = 22), or both (n = 4). In the MRI group (n = 23, aged 58 +/- 10 yr), MRI was carried out one to five times in each patient a median of 166 days (range, 1-501) after stent implantation. The control group comprised 24 patients, ages 59 +/- 11 yr. The incidences of stent-thrombosis, stent-restenosis, and other cardiovascular complications did not differ statistically significantly between the two groups. In the MRI group, stent-related thrombosis (n = 1) or restenosis (n = 7) was observed in eight cases a median of 102 days (range, 7-547) after MR examination and a median of 318 days (range, 138-713) after stent implantation, compared with nine cases in the control group (thrombosis, n = 1; restenosis, n = 8) observed a median of 147 days (range, 1-267) after stent implantation. No acute thromboembolic or other complication occurred in immediate connection with MRI. The follow-up time was 21.3 +/- 4.5 months. This small study shows no evidence of an MRI-related risk of stent-restenosis or other cardiovascular complications, not even if cardiac MRI is performed early after stent implantation.

Prosthetic heart valve evaluation by magnetic resonance imaging.

OBJECTIVE: To evaluate the potential of magnetic resonance imaging (MRI) for evaluation of velocity fields downstream of prosthetic aortic valves. Furthermore, to provide comparative data from bileaflet aortic valve prostheses in vitro and in patients. METHODS: A pulsatile flow loop was set up in a 7.0 Tesla MRI scanner to study fluid velocity data downstream of a 25 mm aortic bileaflet heart valve prosthesis. Three dimensional surface plots of velocity fields were displayed. In six NYHA class I patients blood velocity profiles were studied downstream of their St. Jude Medical aortic valves using a 1.5 Tesla MRI whole-body scanner. Blood velocity data were displayed as mentioned above. RESULTS: Fluid velocity profiles obtained from in vitro studies 0.25 valve diameter downstream of the valve exhibited significant details about the cross sectional distribution of fluid velocities. This distribution completely reflected the valve design. Blood velocity profiles in humans were considerably smoother and in some cases skewed with the highest velocities toward the anterior-right ascending aortic wall. CONCLUSION: Display and interpretation of fluid and blood velocity data obtained downstream of prosthetic valves is feasible both in vitro and in vivo using the MRI technique. An in vitro model with a straight tube and the test valve oriented orthogonally to the long axis of the test tube does not entail fluid velocity profiles which are compatible to those obtained from humans, probably due to the much more complex human geometry, and variable alignment of the valve with the ascending aorta. With the steadily improving quality of MRI scanners this technique has significant potential for comparative in vitro and in vivo hemodynamic evaluation of heart valves.

Age-dependent changes in spatial and temporal blood velocity distribution of early left ventricular filling.

This study describes early diastolic inflow dynamics based on three-directional magnetic resonance velocity data and investigates age-dependent changes in early diastolic inflow characteristics. We examined 26 young healthy volunteers age 25 (3) years (mean, SD), and 23 healthy older volunteers age 63 (8) years. Three-directional magnetic resonance velocity mapping was performed in a long axis plane through the heart. Transverse velocity profiles were read in five different positions in the early diastolic inflow stream of the left ventricle. The size and timing of the maximum velocities at each level were recorded and the repeatability of the method was tested. Compared with the younger group, the older group was characterized by: 1) lower maximum velocity in all positions, 2) increased deceleration of blood downstream from the mitral leaflet tips, and 3) delayed velocity propagation. The described method was repeatable and enabled detection of the age-dependent differences between groups of normal subjects. In conclusion, the early diastolic inflow pattern changes with age, probably reflecting changes in the diastolic function of the myocardium.

A semi-automated method to quantify left ventricular diastolic inflow propagation by magnetic resonance phase velocity mapping.

A new method of analysis was used for clinical magnetic resonance phase velocity mapping (PVM) to quantify propagation speed (PS) of early diastolic left ventricular (LV) inflow. A group of older volunteers (OV; n = 21, age 58+/-11 years) and a group of aortic stenosis patients (AS; n = 21, age 69+/-8 years) were studied. PVM was used to measure diastolic inflow in the LV outflow tract plane. PS was quantified by a semi-automated method (Auto) and by an operator (Manual). The mean+/-SD PS was 0.71+/-0.21 (Auto) and 0.67+/-0.23 (Manual) m/sec in the OV group, versus 0.49+/-0.28 (Auto) and 0.43+/-0.18 m/sec (Manual) in the AS group. There were no differences in peak transmitral E-wave (P = 0.70) between OV and AS. However, there were differences in PS-Auto (P = 0.0079) and PS-Manual (P = 0.0007) between the two groups. PS is a promising index for identifying diastolic LV dysfunction in AS patients. The semi-automated technique is a practical approach for quantifying LV filling.

Pulmonary and caval flow dynamics after total cavopulmonary connection.

OBJECTIVE: To assess flow dynamics after total cavopulmonary connection (TCPC). DESIGN: Cross-sectional study. SETTING: Aarhus University Hospital. PATIENTS: Seven patients (mean age 9 (4-18) years) who had previously undergone a lateral tunnel TCPC mean 2 (0. 3-5) years earlier. INTERVENTIONS: Pressure recordings (cardiac catheterisation), flow volume, and temporal changes of flow in the lateral tunnel, superior vena cava, and right and left pulmonary arteries (magnetic resonance velocity mapping). RESULTS: Superior vena cava flow was similar to lateral tunnel flow (1.7 (0.6-1.9) v 1. 3 (0.9-2.4) l/min*m2) (NS), and right pulmonary artery flow was higher than left pulmonary artery flow (1.7 (0.6-4.3) v 1.1 (0.8-2. 5) l/min*m2, p < 0.05). The flow pulsatility index was highest in the lateral tunnel (2.0 (1.1-8.5)), lowest in the superior vena cava (0.8 (0.5-2.4)), and intermediate in the left and right pulmonary arteries (1.6 (0.9-2.0) and 1.2 (0.4-1.9), respectively). Flow and pressure waveforms were biphasic with maxima in atrial systole and late ventricular systole. CONCLUSIONS: Following a standard lateral tunnel TCPC, flow returning via the superior vena cava is not lower than flow returning via the inferior vena cava as otherwise seen in healthy subjects; flow distribution to the pulmonary arteries is optimal; and some pulsatility is preserved primarily in the lateral tunnel and the corresponding pulmonary artery. This study provides in vivo data for future in vitro and computer model studies.

Where to place the Doppler sample volume in the human main pulmonary artery: evaluated from magnetic resonance phase velocity maps.

OBJECTIVE: To give recommendations for the placement of Doppler sample volumes for blood flow assessment in the human main pulmonary artery. METHODS: In 10 healthy volunteers MR-phase velocity measurements were obtained and computing of the mean temporal blood velocity data was performed to guide single point Doppler velocity recordings. RESULTS: The mean temporal blood velocity profiles were consistently skewed with the lowest blood velocities towards the inferior/right vessel wall. Blood velocity indices (ratio of point to mean velocities, where a point equals a square of 4 pixels) varied considerably with the lowest indices located towards the inferior/right vessel wall. A centrally located fictive sample volume revealed an average blood velocity index value (average of all 10 subjects) of 1.08 (range 0.99-1.25; s.d. 0.08) where the central point was defined at maximum systole, and a value of 1.13 (range 0.97-1.34; s.d. 0.11) when the central point was defined in end-diastole. The mean of multiple sample volumes along the inferior/right to superior/left diameter revealed a blood velocity index of 1.01 (range 0.87-1.21; s.d. 0.09) in systole and 1.03 (range 0.87-1.19; s.d. 0.09) in diastole. CONCLUSIONS: For practical clinical purposes, single point estimation of the mean blood velocity in the pulmonary artery should be performed centrally. The use of multiple sample volumes placed along the inferior/right to superior/left diameter improves the mean velocity estimate in healthy volunteers. Further studies should be conducted to reinforce the basis for Doppler velocity recording in the diseased human pulmonary artery as well as to investigate other important determinants of Doppler-derived CO, namely angle of insonation and assessment of the cross-sectional area.

The impact of ischemic heart disease on main pulmonary artery blood flow patterns: a comparison between magnetic resonance phase velocity mapping and transesophageal color Doppler.

OBJECTIVE: To give a detailed evaluation on main pulmonary artery blood velocity patterns, in patients with ischemic heart disease and to provide recommendations for pulsed Doppler sample volume placement, in order to optimize cardiac output estimation. METHODS: Using magnetic resonance phase and esophageal color Doppler velocity mapping in 12 patients with ischemic heart disease and undergoing coronary artery by-pass grafting, very similar data on pulmonary artery blood velocity patterns were provided for comparison with each other. RESULTS: Peak blood velocities were located in the inferior half of the main pulmonary artery cross-sectional area. Early after peak systole the highest velocities shifted towards the superior/left (major curvature) with a simultaneous decrease in velocities inferiorly. The velocity decrease further evolved into retrograde flow to the inferior/right (minor curvature). This feature was significantly enhanced compared to earlier findings in healthy volunteers. The mean temporal blood velocity profiles were asymmetrically skewed, thereby giving unreliable cardiac output estimates based on single point Doppler blood velocity recordings. The error incurred may amount to more than 100% in extreme cases. According to our data, optimal assessment of cardiac output should be based on multiple sample volumes placed along the inferior/right to superior/left diameter. CONCLUSIONS: MR-phase velocity mapping and multiplane transesophageal color Doppler recordings provided similar blood velocity patterns in patients with ischemic heart disease. The skewness of the mean temporal blood velocity profile is enhanced compared with healthy subjects, resulting in error in the assessment of CO by means of pulsed Doppler echocardiography. By using multiple Doppler sample volumes, the error can be minimized.

Magnetic resonance imaging of blood velocity distribution around St. Jude medical aortic valves in patients.

BACKGROUND AND AIMS OF THE STUDY: Complications after replacement of diseased heart valves with mechanical prostheses may be related to fluid dynamic disturbances. Magnetic resonance velocity mapping may allow quantitative, non-invasive, serial assessment of the blood velocity distribution around prosthetic heart valves in patients. MATERIAL AND METHODS: Velocity mapping was performed in six patients with aortic St. Jude Medical valves. Axial velocity components were measured at three positions near the valve and correlated with earlier in vitro results and with earlier invasive measurements. RESULTS: The velocity profiles downstream of the valve prostheses reflected the valve design and thus confirmed previous findings. In the one diameter downstream position blood flow velocities accelerated initially through the lateral orifices of the valve. Later in the acceleration phase the velocity profile became skewed and the antegrade velocity components increased in the part of the vessel corresponding to the central slit of the valve. Retrograde velocities occurred in part of the lateral orifice regions. CONCLUSIONS: MR velocity mapping provides valuable information on velocity fields around prosthetic bileaflet aortic valves. The velocity fields from the present study disclose qualitative similarity to those previously obtained. The present study, however, suggests a more skewed velocity profile than predicted from former studies. More extensive studies on larger patient groups should be performed, also with other valve types in order to establish a bank of reference data.

MARIAN: an analysis tool for the assessment of left ventricular function measured by velocity encoding MRI.

Velocity encoding MRI is a new non-invasive technique for measuring cardiac blood flow velocities. Flow in the three directions of space can be measured during the entire heart cycle. However, the analysis of large amount of data obtained from this technique requires specialized computational software packages to provide physicians with efficient analysis tools. A data visualization software package named Magnetic Resonance Imaging Analyzer (MARIAN) was developed. This software package uses visualization, animation, analysis, and computational tools adapted to time series of cardiac MRI data files, all accessible through a sophisticated graphics user interface. MARIAN was used as a tool for the analysis of the left heart blood flow patterns in two groups of human subjects: ten volunteers and eight patients. The patients were diagnosed with incapacitating angina pectoris and previous left ventricular myocardial infarction. Vector plot animations of the left atrial flow were realized for all volunteer examinations. The temporal flow velocity profiles were sampled at the tips of the mitral leaflets and in the lumen of the right upper pulmonary vein, when possible. The isovolumic relaxation time (IVRT) was estimated. The following flow parameters were obtained from the velocity profiles: at the mitral valve, the early diastolic E-wave, the late diastolic A-wave, the time of occurrence of the E- and A- waves; at the right upper pulmonary vein, the systolic S-wave, the early diastolic D-wave and the reverse late diastolic R-wave. The results obtained were consistent with previous studies using similar MRI techniques. Compared to the control group, the patient group exhibited higher isovolumic relaxation time, a lower peak E-wave, and a lower D-wave. MARIAN thus provided a fast, efficient and accurate data visualization tool for the analysis of human data.

A new control volume method for calculating valvular regurgitation.

BACKGROUND: The purpose of the present study was to develop a new method of measuring heart valvular regurgitation based on control volume theory and to verify its accuracy in vitro and in vivo. Current methods of quantifying valvular regurgitation rely too much on assumptions about the flow field and therefore are difficult to apply in vivo. In particular, the proximal isovelocity surface area (PISA) method oversimplifies the proximal velocity field by assuming hemispherical isovelocity contours proximal to the orifice. This severely limits the applicability of the PISA method. Use of the basic control volume theory, however, removes the need to assume the manner in which the proximal flow accelerates toward the regurgitant orifice, the shape and size of the orifice, the shape of the orifice plate, and the non-newtonian behavior of the fluid. Apart from a correction that is necessary if the orifice plate is moving, the control volume method assumes only the incompressibility of the fluid and therefore is a potentially more accurate approach. In addition, the use of magnetic resonance imaging (MRI) precludes the need for an acoustic window. METHODS AND RESULTS: MRI has been used to measure the three-dimensional velocity field proximal to regurgitant orifices, including single and multiple orifices and a cone-shaped orifice plate. Both steady (0 to 7.5 L/min) and pulsatile (2 and 3 L/min) flows were used. By intergrating this velocity over a control volume surrounding the orifice, we calculated the flow rate through the orifice. As a validation, the cardiac output of a 50-kg pig also was measured and was compared with thermodilution measurements. It was found that MRI could be used to measure the three-dimensional flow proximal to regurgitant orifices. This enabled the calculation of the flow rate through the orifice by integrating the velocity over the surface of a control volume covering the orifice. This flow rate correlated well with the actual rate (0.992; correlation line slope, 1.01). Care had to be taken, however, to exclude from the integration regions of aliased velocity. The cardiac output of the pig measured using MRI was in close agreement with the themodilution measurements. CONCLUSIONS: Our new method of measuring valvular regurgitation has been shown to be very accurate in vitro and in vivo and therefore is a potentially accurate way to quantify valvular regurgitation.