Flow volume measurement, ultrasound imaging and early intervention in dialysis access improves patency

Michael J. Howe, BA, Krishna M. Jain, MD, John S. Munn, MD, Mark C. Rummel, MD, Sarat K. Vaddineni, MD.
Michigan State College of Human Medicine, Kalamazoo, MI.

Abstract Objective: To identify hemodynamically significant stenosis in vascular access and correct it to improve patency.
Methods: In dialysis unit monthly transsonic interrogation of the access is performed. When the flow drops < 600 cc/min in grafts or < 400 cc/min in fistula ultrasound evaluation is done. Significant stenosis >70% prompts intervention. In this retrospective review covering January 1, 2004 to August 15, 2006, 132 patients were evaluated. All the demographic information, ultrasound findings, operative findings, and patency of the access were recorded. End-point was thrombosis. Stastical analysis was done.
Results: 131 patients had 209 ultrasound done.There were 72 PTFE grafts and 64 fistulas. There were 203 interventions in grafts and 73 in fistulas. 25 access thrombosed between the positive ultrasound and the planned intervention, or in the observation period.

	Graft	Fistula
Balloon angioplasty	67	41
Viabahn	24	1
Interposition	30	10
Patch	14	5
Thrombectomy	23	2
Stent	45	14

The positive predictive value of ultrasound was 0.89, negative predictive value was 0.73.

Life-table analysis

Months	Graft patency	Fistula patency
1	100	100
3	77.0	94.0
6	52.9	75.5
12	31.7	46.3
18	22.7	25.0
24	11.3	11.8
32	4.9	8.8

The mean patency of fistulas was 9.0 months and of 7.3 months for grafts. This is better as compared to historical controls from our institution when thrombosed access is rechanneled
Conclusion: Flow volume measurement and ultrasound imaging is a reliable and effective technique to evaluate lesions in dialysis access. Early intervention improves patency and is recommended.

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