The design and use of a simple device for the MRI assessment of changes in cardiovascular function by lower-body negative-pressure-simulated reduction of central blood volume.

AIM: To use a locally designed and simple lower-body negative-pressure (LBNP) device and 1.5 T magnetic resonance imaging (MRI) to demonstrate the ability to assess changes in cardiovascular function during preload reduction. These effects were evaluated on ventricular volumes and great vessel flow in healthy volunteers, for which there are limited published data. MATERIAL AND METHODS: After ethical review, 14 volunteers (mean age 33.9 ± 7 years, mean body mass index [BMI] 23.1 ± 2.5) underwent LBNP prospectively at 0, -5, -10, and -20 mmHg pressure, using a locally designed LBNP box. Expiratory breath-hold biventricular volumes, and free-breathing flow imaging of the ascending aorta and main pulmonary artery were acquired at each level of LBNP. RESULTS: At -5 mmHg, there was no change in aortic flow or left ventricular volumes versus baseline. Right ventricular output (p=0.013) and pulmonary net flow (p=0.026) decreased. At -20 mmHg, aortic and pulmonary net flow (p<0.001) decreased, as were left and right ventricular end diastolic volume (p<0.001) and left and right end systolic volumes (p=0.038 and p=0.003 respectively). CONCLUSIONS: Use of a MRI-compatible LBNP device is feasible to measure changes in ventricular volume and great arterial flow in the same experiment. This may enhance further research into the effects of preload reduction by MRI in a wide range of important cardiovascular pathologies.

Coronary artery stenosis in an Australian population.

The purpose of this study was to examine the extent and severity of coronary stenosis in an Australian population. The subjects were autopsy cases among people aged 20-69 yrs dying in and out of hospital in the Newcastle area of New South Wales in 1985-86. Three groups were compared: coronary deaths, deaths from other natural causes and deaths due to external causes. Cross-sectional luminal narrowing in each major subepicardial artery was measured by stereological point counting. Stenosis was found, as expected, to be more severe in males than in females, increased with age and was greatest in those who died from coronary disease. Even in non-coronary deaths mean percentage luminal narrowing in the narrowest segments ranged from about 40% in people aged 20-29 yrs to over 60% in those aged 60-69 yrs. Narrowing was more pronounced in the left anterior descending artery and least in the left circumflex artery. To the extent that results from this autopsy study can be generalized to the whole population, these findings illustrate that, despite declining mortality from ischemic heart disease in Australia, coronary atherosclerosis remains a widespread problem.