Duane D. Blatter

Cardiac magnetic resonance versus transthoracic echocardiography for the assessment of cardiac volumes and regional function after myocardial infarction: an intrasubject comparison using simultaneous intrasubject recordings

BackgroundAlthough echocardiography is commonly used to evaluate cardiac function after MI, CMR may provide more accurate functional assessment but has not been adequately compared with echo. The primary study objective was to compare metrics of left ventricular volumes and global and regional function determined by cardiac magnetic resonance (CMR) and echocardiography (echo) in patients (pts) with recent myocardial infarction (MI).MethodsTo compare CMR with echo, 47 consecutive patients (pts 70% male; mean age = 66 ± 11 years) with MI >6 wks previously and scheduled for imaging evaluation were studied by both echo and CMR within 60 min of each other. Readers were blinded to pt information. Pearsons correlation coefficient, paired t-tests, and chi-square tests were used to compare CMR and echo measures. Further comparisons were made between pts and 30 normal controls for CMR and between pts and published normal ranges for echo.ResultsMeasures of volume and function correlated moderately well between CMR and echo (r = 0.54 to 0.75, all p < 0.001), but large and systematic differences were noted in absolute measurements. Echo underestimated left ventricular (LV) volumes (by 69 ml for end-diastolic, 35 ml for end-systolic volume, both p < 0.001), stroke volume (by 34 ml, p < 0.001), and LV ejection fraction (LVEF) (by 4 percentage point, p = 0.02). CMR was much more sensitive to detection of segmental wall motion abnormalities (p < 0.001). CMR comparisons with normal controls confirmed an increase in LV volumes, a decrease in LVEF, and preservation of stroke volume after MI.ConclusionThis intra subject comparison after MI found large, systematic differences between CMR and echo measures of volumes, LVEF, and wall motion abnormality despite moderate inter-modality correlations, with echo underestimating each metric. CMR also provided superior detection and quantification of segmental function after MI. Serial studies of LV function in individual patients should use the same modality.

Use of an implantable needle guide to access difficult or impossible to cannulate arteriovenous fistulae using the buttonhole technique

Purpose The aim of this work was to assess the safety and efficacy of the VWING Vascular Needle Guide to assist in cannulation of difficult or impossible to access fistulae using the buttonhole cannulation technique. Methods VWING devices were surgically implanted into patients with difficult to access fistulae. A nondevice site and a device site were used to access the fistula and perform dialysis over a six month period. The device site utilized the buttonhole cannulation technique. The performance of each access site was recorded. Results VWING devices were implanted in nine patients. A total of 387 cannulations took place over 1367 study days. The device site was successfully used 94% of the time compared to 77% for the nondevice site. Cannulation success was comparable between the device and nondevice sites. Ease of insertion, pain during insertion and complication rates were also comparable. No interventions were required at the device site to maintain access compared with four interventions for the nondevice access site. Conclusions The VWING performed as intended by facilitating required repeated access to the vascular system and access for hemodialysis treatment. The study has demonstrated that the VWING is a potential solution for access to difficult to cannulate fistulae.

Normal Cardiac Magnetic Resonance Measurements and Interobserver Discrepancies in Volumes and Mass Using the Papillary Muscle Inclusion Method

Background: The potential of cardiac magnetic resonance (CMR) imaging to provide precise and reproducible measurements might not be realized currently. Methods: We acquired CMR images on 30 healthy adults and compared readings of 2 experienced physicians to determine sources of measurement variability. Results: Simultaneous review of tracings revealed 3 major sources of interobserver variability: 1) choice of end- diastolic/end-systolic frames; 2) choice of the most basal left and right ventricular short-axis slices; and, 3) approach to endocardial edge selection. Study Plan. These objectives were to be achieved through a prospective study in an adequate number of healthy subjects. Qualifying subjects were to undergo a stan- dardized functional CMR evaluation. Predefined cardiovas- cular measurements were made using workstation-specific methods. Key volume and mass measurements were to be performed independently by 2 observers to improve accu- racy, to determine reproducibility, and to develop consensus methods. Results were to be used for clinical and research