SUBJECTS AND METHODS: Forty-five subjects were studied: 29 subjects (age 51±12 years, M:F=14:15, Control group) with a normal coronary angiogram and 16 patients with multivessel CAD (age 60±12 years, M:F=9:7, CAD group). After obtaining the tubular color flow signals of the distal left anterior descending coronary artery (LAD) using an ultra-band transducer (5-12 MHz) with a special preset program in the low velocity range, the peak (PDV), mean diastolic velocity (MDV) and velocity time integral (VTI) were measured before and after administering sublingual nitroglycerin (NTG) (0.6 mg). In all subjects, 3DE image acquisition and reconstruction of the distal LAD flow was performed before and after sublingual nitroglycerin (NTG) using a 3DE unit with a magnetic tracking system (TomTec Imaging Systems) linked to the conventional 2D ultrasound system (Sonos 7500). Quantitative analysis of coronary vasodilation was performed on cross-sectional images.

RESULTS: The % change in the PDV, MDV and VTI after NTG administration was 41.3±14.0%, 37.9±13.8% and 40.3±18.2% in the control group and 23.0±13.9%, 19.1±11.5% and 26.1±12.4% in the CAD group (p<0.05, versus Control group, respectively) The distal LAD diameter on the coronary 3DE after NTG administration increased from 2.28±0.79 mm to 3.32±1.07 mm (52.3±28.5%) in the control group and from 2.36±0.65 mm to 2.89±0.81 mm (23.7±23.9%) in the CAD group (p<0.005 versus Control group). The magnitude of vasodilation correlated with the % change in the PDV (r=0.516, p<0.005), MDV (r=0.519, p<0.005) and % VTI (r=0.392, p=0.008).

CONCLUSION: These results suggest that level of vasodilation after NTG administration is reduced in advanced atherosclerosis and can be measured noninvasively. A 3D reconstruction of the distal LAD flow using free-hand 3DE with rotational scanning is a promising noninvasive technique for examining the coronary vasomotor function.