Abnormal Response of Ankle Pressure After Exercise in Seemingly Normal Subjects Living in Blackfoot Disease-Hyperendemic Villages in Taiwan

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Abstract
Arsenic-related peripheral vascular disease has been reported in many countries, including Taiwan, where the disease was called blackfoot disease (BFD) after the dry gangrene at its terminal stages. Because the induction period of BFD is twenty to thirty years, the authors speculated that subclinical arterial insufficiency might be present. The purpose of this study was to detect possible minor arterial insufficiency in the seemingly normal subjects who had consumed the high-arsenic well water for more than thirty years. Twenty-three seemingly normal men living in BFD-hyperendemic villages and 28 age-sex-BMI-matched men from a nearby nonendemic area were recruited. All of them were not obese, had neither diabetes mellitus nor hypertension, did not smoke, and had normal Doppler ultrasound examination findings at rest. Brachial pressures on both arms and ankle pressures on both right and left dorsal pedal and posterior tibial arteries were measured before and after treadmill exercise (1.2 mph, 10% grade, ten minutes). Before exercise, brachial pressures, ankle pressures, ankle-brachial index, and ankle- brachial gradients were similar in BFD area and nonBFD area groups. After exercise, ankle pressure increased in correspondence to increased brachial pressure in the nonBFD area group, maintaining ankle-brachial index and ankle-brachial gradient within normal limits. However, in the BFD area group, a paradoxical drop of ankle pressures led to a significant fall of ankle-brachial index and ankle-brachial gradient. Only 3 (10.7%) cases (continued on next page) (Abstract continued) with 4 (7.1%) limbs from the nonBFD area showed negative values of ankle-brachial gradients (-3 mmHg to -10 mmHg). However, there were 13 (56.5%) cases with 20 (43.5%) limbs showing negative gradients (-1 mmHg to -33 mmHg) in the BFD area group. The odds ratios of having minor arterial occlusive disease was about 10 times higher in the seemingly normal subjects living in BFD-hyperendemic villages with ankle- brachial gradients after exercise either < 0 mmHg or < -9 mmHg as a cutoff point. The authors conclude that subclinical arterial insufficiency could be demonstrated in a high percentage of the seemingly normal subjects who had been chronically exposed to arsenic. For early detection of arterial disease and early intervention to prevent future amputation, they advocate the exercise test as a screening and monitoring method.