An exercise stress test for contrast-enhanced duplex ultrasound assessment of lower limb muscle perfusion in patients with peripheral arterial disease.

OBJECTIVE: The aim of the present study was to develop a standardized contrast-enhanced duplex ultrasound (CE-DUS) protocol to assess lower-extremity muscle perfusion before and after exercise and determine relationships of perfusion with clinical and functional measures. METHODS: CE-DUS (EPIQ 5G, Philips) was used before and immediately after a 10-minute, standardized bout of treadmill walking to compare microvascular perfusion of the gastrocnemius muscle in older (55-82 years) patients with peripheral arterial disease (PAD) (n = 15, mean ankle-brachial index, 0.78 ± 0.04) and controls (n = 13). Microvascular blood volume (MBV) and microvascular flow velocity (MFV) were measured at rest and immediately following treadmill exercise, and the Modified Physical Performance Test (MPPT) was used to assess mobility function. RESULTS: In the resting state (pre-exercise), MBV in patients with PAD was not significantly different than normal controls (5.17 ± 0.71 vs 6.20 ± 0.83 arbitrary units (AU) respectively; P = .36); however, after exercise, MBV was ∼40% lower in patients with PAD compared with normal controls (5.85 ± 1.13 vs 9.53 ± 1.31 AU, respectively; P = .04). Conversely, MFV was ∼60% higher in patients with PAD compared with normal controls after exercise (0.180 ± 0.016 vs 0.113 ± 0.018 AU, respectively; P = .01). There was a significant between-group difference in the exercise-induced changes in both MBV and MFV (P ≤ .05). Both basal and exercise MBV directly correlated with MPPT score in the patients with PAD (r = 0.56-0.62; P < .05). CONCLUSIONS: This standardized protocol for exercise stress testing of the lower extremities quantifies calf muscle perfusion and elicits perfusion deficits in patients with PAD. This technique objectively quantifies microvascular perfusion deficits that are related to reduced mobility function and could be used to assess therapeutic efficacy in patients with PAD.

Measurement of thrombus resolution using three-dimensional ultrasound assessment of deep vein thrombosis volume.

OBJECTIVE: Current imaging techniques are limited in their ability to quantify thrombus burden, progression, resolution, and organization over time in patients with acute deep vein thrombosis (DVT). These assessments are critical measures of therapeutic success when thrombolytic or thrombectomy treatment protocols are utilized for DVT. We evaluated the reliability of a new, commercially available method of acquiring and analyzing three-dimensional (3D) ultrasound images of DVTs that measures thrombus volume and echogenicity. METHODS: We studied 25 consecutive hospital in-patients (18 male, seven female; age range, 37-87 years) with a first episode of acute DVT. Treatment decisions were not influenced by the study protocol. Scanning was performed independently by two sonographers, then the first sonographer repeated the scan. A combination of routine imaging in grayscale, color-flow, and power-Doppler modes (2D transducer) along with volumetric imaging (3D transducer) was performed. Patients underwent imaging at baseline and on one or more follow-up days 7, 14, 21 and 30. Image-processing software loaded on the ultrasound machine was used to obtain thrombus volume and echogenicity measurements. RESULTS: Thrombus volume was reliably determined by our protocol. The median volume of thrombus at baseline was 0.4 cm(3). Mean inter- and intraobserver differences in volume measurements were 0.006 ± 0.26 cm(3) and -0.12 ± 0.29 cm(3) (mean ± standard deviation). Thrombus resolved over time at a rate of -0.042 ± 0.01 cm(3)/day (P < .003). The median echogenicity of thrombus at baseline expressed as the grayscale median value was 59. There was a trend for thrombus organization (measured as echogenicity) to increase with time, +0.36 ± 0.23 grayscale median units/day (P < .13). Adjustment for the use of anticoagulation, gender of subject, or location of DVT in the upper vs lower extremity did not alter the relationship between time and volume or time and echogenicity. CONCLUSIONS: We describe a 3D imaging protocol that reliably measures thrombus volume and echogenicity over time. The method is convenient and can be utilized in routine clinical practice. Acute DVT was associated with a reduction in thrombus size and trend for increased echogenicity over 1 month. This protocol will be of increasing value as our appreciation for the deleterious effects of residual thrombus after DVT increases and our utilization of aggressive thrombus removal treatments for acute DVT increases.