Assessment of left atrial volumes at 1.5 Tesla and 3 Tesla using FLASH and SSFP cine imaging.

PURPOSE: To investigate left atrial volumes and function and their variability in healthy volunteers using steady state free precession (SSFP) and fast low angle shot (FLASH) sequences at both 1.5 and 3 T using both the short-axis and biplane area-length methods. MATERIALS AND METHODS: Ten healthy volunteers underwent CMR at both 1.5 and 3 Tesla. The biplane area-length method utilized volumes from the horizontal and vertical long axis images. RESULTS: There were no significant differences between left atrial short-axis volumes or function between 1.5 and 3 T assessed using either FLASH or SSFP sequences. The biplane area-length method underestimated maximal left atrial volume using FLASH by 12 mL at 3 T (18%) and by 10 mL (14%) at 1.5 T (p = 0.003 and p = 0.05 respectively). Variability was larger for left atrial measurements using the biplane area-length method. CONCLUSION: Field strength had no effect on left atrial volume and function assessment using either FLASH or SSFP. The use of the short-axis method for the acquisition of left atrial parameters is more reproducible than the biplane area-length for serial measurements.

Semi-automatic boundary detection to improve reporting of regional left ventricular function.

AIMS: The reporting of regional left ventricular function is based on subjective assessment of endocardial motion and thickening and has a significant learning curve. We hypothesized that the use of an semi-automatic boundary detection system generating images with superimposed moving endocardial borders and a fixed end-diastolic reference border could improve the reporting of regional function. METHODS: We obtained 58 resting contrast images of 15 patients and using a new boundary detection system (Quamus), generated images with superimposed endocardial borders. The contrast images, images with additional Quamus borders and Quamus borders alone were assessed by two level 1 and two level 2 echocardiographers. They scored regional function and results were compared to two level 3 experienced stress echocardiography readers. RESULTS: The addition of borders improved the agreement of level 1 echocardiographers (weighted Kappa increased from 0.55 to 0.64) but did not change for level 2 echocardiographers (0.63 to 0.64) and has the potential to be a useful training tool.

Joint outpatient clinics for the adult with congenital heart disease at the district general hospital: an alternative model of care.

Congenital heart disease (CHD) affects approximately 250,000 adults in the UK. Most of these patients would benefit from specialized follow-up. However, there is at present a significant shortfall of specialized tertiary care expertise and facilities for this growing cardiovascular field in the UK and around the world. We aimed to report our experience with a joint adult CHD clinic run in a district general hospital with regular input from the local cardiology team and a visiting adult CHD specialist. In total, 148 patients aged 33.6+/-14.1 years were seen once or more in 12 clinics over the study period (September 1999 to January 2003). Diagnostic case mix consisted of 2.9% complex, 67.9% moderate and 29.2% minor cases of CHD. Twenty percent of patients visited the counterpart tertiary center for additional investigations (mostly MRI) and 8% for intervention (with no operative mortality). There was one death during the study period giving an overall mortality of 0.2%/year. Patients were referred to the clinic from tertiary centres, the local cardiology and paediatric clinics and with time from obstetric and community sources. Nonattendance rates were relatively low, comparing favourably with tertiary care. This model of joint care for the adult CHD patient at a general district hospital with regular onsite specialized input appears to be effective and highlights the need for additional resource allocation to provide optimal care for these patients. Our data may be useful in future planning for CHD services.

Inhibition of platelet aggregation with glyceryl trinitrate and xanthine oxidoreductase.

Xanthine oxidoreductase (XOR) is a mammalian enzyme that possesses a series of redox centers, which use either NAD(+) or molecular oxygen for oxidation of the purines xanthine and hypoxanthine to uric acid. The ability of XOR to act as an NADH oxidase is a less well recognized function of the enzyme, and it is this function that we used to explore the metabolism of glyceryl trinitrate. The antiplatelet effect of nitric oxide (NO) on platelet aggregation was used as a bioassay to assess the bioconversion of glyceryl trinitrate to NO by XOR. The thromboxane mimetic U46619, 2 microM, was used to stimulate platelet aggregation in platelet-rich plasma prepared from healthy drug-free human volunteers. All incubations were carried out at 37 degrees C for 2 min after the addition of U46619. XOR produced a dose-dependent antiaggregant effect when incubated with glyceryl trinitrate (GTN), 220 microM. This did not occur when GTN or XOR was incubated with platelet-rich plasma independently. The antiaggregant effect of XOR plus GTN was dose dependently inhibited by allopurinol, with an IC(50) of 100 microM. The addition of superoxide dismutase (SOD), 100 U/ml produced a shift to the left in the antiaggregant dose-response curve for XOR. The IC(50) for XOR at 200 U/l without SOD was decreased to 80 U/l with SOD. Oxyhemoglobin, an extracellular NO scavenger, produced a dose-dependent, noncompetitive inhibition of the antiaggregant effect of XOR plus GTN. These findings suggest that GTN may be reduced to NO in vitro by the enzyme XOR in sufficient amounts to inhibit platelet aggregation.