Early detection of digitalis-induced nonocclusive mesenteric ischemia using Doppler ultrasonography.

To the Editor: Acute mesenteric ischemia occurs in 1 of 1000 hospital admissions, and a nonocclusive mechanism makes up about 20% of these cases. (1) Nonocclusive mesenteric ischemia (NOMI) is a condition where the macrovasculature is patent, but the microvascular blood flow is inadequate to meet intestinal tissue demands leading to gangrene and disastrous consequences. The pathophysiology of NOMI involves low blood flow states such as shock, heart failure, hemodialysis and direct splanchnic arteriolar vasoconstriction by drugs, eg, digoxin. (2,3) Angiography is the gold standard for diagnosis; however, its invasive nature, potential for contrast nephropathy and limited availability makes it a less than optimal screening tool. Use of Doppler ultrasonography in the early detection of NOMI has not been reported. A 68-year-old man with congestive heart failure was admitted for recurrent ventricular tachycardia. His medications included digoxin, amiodarone, furosemide, metoprolol succinate, and warfarin. On physical examination, he was mildly hypotensive. Laboratory investigations showed a creatinine of 1.7 mg/dL, with normal electrolytes. The digoxin concentration was in the normal range. His medications, including digoxin, were continued in the hospital. On the third hospital day, he developed cramping abdominal pain with nausea starting 30 minutes after eating, which improved intermittently between meals. Abdominal examination was benign and x-rays were normal. Mesenteric ischemia was suspected and a Doppler ultrasound of the mesenteric arteries was obtained. There was normal peak systolic velocity with severely decreased diastolic flow both pre and postprandially in the superior mesenteric artery. This was suggestive of elevated resistance in the distal mesenteric arterioles consistent with NOMI. The digoxin was stopped. In the setting of renal insufficiency, it was decided to optimize hemodynamic status before angiography. The patient's symptoms started to resolve after 24 hours. Daily follow-up Doppler ultrasounds showed progressive improvement in diastolic flow. Angiogram of the mesenteric arteries four days after discontinuation of digoxin was normal. Doppler study performed at this time also showed normal diastolic flow with resolution of the vasospasm. The patient was discharged home without digoxin. On follow up one month later, the patient had no abdominal symptoms.

Doppler ultrasound is a noninvasive diagnostic tool with increasing utility in the assessment of chronic and acute mesenteric ischemia caused by atheromatous and thrombotic phenomenon. (4) Its role in diagnosing NOMI has not been described. NOMI is often diagnosed late, presenting commonly as massive intestinal gangrene requiring surgical intervention with resultant high morbidity and mortality. (3) This is largely attributable to nonspecific symptomatology and lack of noninvasive diagnostic modalities. The diagnosis of NOMI in our patient with Doppler ultrasound showing decreased to absent diastolic flow, which subsequently reverted to normal following discontinuation of digoxin, suggests that NOMI was detected at an early stage and thus could be reversed with optimization of splanchnic blood flow. This finding of "subacute NOMI" highlights the utility of Doppler ultrasound to detect this process early in its evolution. Given the noninvasive nature of this modality and increasing number of patients with high risk (low flow states) in modern intensive care units, Doppler ultrasonography holds great promise in the early diagnosis of NOMI.

Ahmed Awab, MD

Mehdi Hamadani, MD

Department of Medicine

University of Oklahoma Health Sciences Center

Oklahoma City, OK

Shoaib Saya, MD

Thomas Whitsett, MD

Department of Medicine and Section of Cardiovascular Disease and Vascular Medicine

University of Oklahoma Health Sciences Center

Oklahoma City, OK

References

1. Stoney RJ, Cunningham CG. Acute mesenteric ischemia. Surgery 1993;114:489-490.

2. Lock G, Scholmerich J. Non-occlusive mesenteric ischemia. Hepatogastroenterology 1995;42:234-239.

3. Howard TJ, Plaskon LA, Wiebke EA et al. Nonocclusive mesenteric ischemia remains a diagnostic dilemma. Am J Surg 1996;171:405-408.

4. Hermsen K, Chong WK. Ultrasound evaluation of abdominal aortic and iliac aneurysms and mesenteric ischemia. Radiol Clin North Am 2004;42:365-381.

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