Coronary atherosclerosis is characterized by an early loss of endothelium-dependent vasodilation. However, the methods of assessing coronary endothelial function are invasive and difficult to repeat over time. Recently, a noninvasive ultrasound method has been widely used to measure flow-mediated dilation in the brachial artery as a surrogate test for endothelial function. We seek to further validate this method of measuring vascular function. The brachial artery diameters and blood flow of 20 normal volunteers (10 males and 10 females) were measured using high resolution (7.5 MHz) ultrasound and strain gauge plethysmography. Flow-mediated endothelium-dependent vasodilation was measured in the brachial artery during reactive hyperemia after 5 minutes of cuff occlusion in the upper arm. The brachial artery diameter increased maximally by 9.7 +/- 4.3% from baseline at 1 min after cuff release and blood flow increased by 1002 +/- 376%. Five min of cuff occlusion was sufficient to achieve 97 +/- 6% of maximal brachial artery dilation and degree of dilation was not different whether the cuff was inflated proximally or distally to the image site. The intraobserver variability in measuring brachial diameters was 2.9% and the variability of the hyperemic response was 1.4%. In young, healthy men and women, the baseline brachial artery diameter was the only factor that was predictive of the flow-mediated vasodilation response. The brachial noninvasive technique has been further validated by the determination of flow-mediated dilation. This method of assessing endothelial function may help to determine the importance of vasodilator dysfunction as a risk factor in the development of atherosclerosis.

Patients who undergo peripheral vascular surgery are at increased risk for postoperative cardiac events and are difficult to assess preoperatively because of limitations on their activity. We prospectively studied 176 consecutive eligible patients undergoing elective vascular surgery to determine the value in predicting a postoperative cardiac event of preoperative electrocardiographic monitoring to detect myocardial ischemia. Of the 176 patients, 32 (18 percent) had 75 episodes of monitored ischemic ST-segment depression preoperatively (of which 73 were asymptomatic), and 13 (7 percent) met strict criteria for major postoperative cardiac events, including 1 with a fatal myocardial infarction, 3 with nonfatal infarctions, 4 with unstable angina, and 5 with ischemic pulmonary edema. Of the 32 patients with ischemia before their operations, 12 had postoperative events (univariate relative risk, 54; 95 percent confidence interval, 7.2 to 400). Only 1 postoperative event occurred among 144 patients who did not have preoperative ischemia. The sensitivity of preoperative ischemia was 92 percent, the specificity 88 percent, the predictive value of a positive result 38 percent, and the predictive value of a negative result 99 percent. In multivariate analyses, preoperative ischemia was the most significant correlate of postoperative cardiac events and remained a statistically significant independent correlate even after we had controlled for all other preoperative factors (multivariate relative risk, 24.4; 95 percent confidence interval, 6.8 to 88). These preliminary data suggest that preoperative electrocardiographic monitoring to detect episodes of myocardial ischemia is a useful method for assessing cardiac risk in patients who undergo elective vascular surgery. In particular, the absence of ischemia during monitoring indicates a very low risk.

1 To determine the distribution of flow, the regional haemodynamic response to 100 mg of captopril was determined in 36 patients with refractory cardiac heart failure. Measurements included forearm blood flow by venous occlusion plethysmography (eight patients), splanchnic blood flow by indocyanine green clearance (10 patients), and coronary blood flow by thermodilution (12 patients). 2 Cardiac index significantly rose in one hour (1.9 +/‐ 0.1 to 2.2 +/‐ 0.1 1/m/m2, p less than 0.01) while forearm blood flow rose slightly (2.9 +/‐ 0.8 to 3.2 +/‐ 0.3 ml/100 ml/min). Renal blood flow rose significantly by 30% (344 +/‐ 48 to 533 +/‐ 82 ml/min, p less than 0.02). Despite a fall in rate pressure product (8.8 +/‐ 0.7 to 7.1 +/‐ 0.5 mm Hg bt x 10(3), p less than 0.02), coronary blood flow did not significantly change (160 +/‐ 20 to 133 +/‐ 12 ml/min), indicating an improved supply‐demand relationship. 3 External myocardial efficiency improved (19 +/‐ 3 to 26 +/‐ 6%, p less than 0.05). Coronary blood flow is unaffected and converting‐enzyme inhibitor improves myocardial efficiency. This strategic reduction in vascular impedence distinguishes converting‐ enzyme inhibitors as a unique class of vasodilators in the treatment of coronary heart failure.

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