Quantitative perfusion imaging assessing acquired discrete peripheral pulmonary artery stenosis.

We present the case an 8-yr-old boy evaluated for anastomotic stenosis of the right pulmonary artery after surgical repair of hemitruncus at 6 wk of age. Pulmonary angiography revealed only mild narrowing and a 10-mm pressure gradient across the anastomosis, but quantitative perfusion imaging demonstrated that the right lung only received 16% of pulmonary blood flow. Subsequently, balloon angioplasty of the anastomotic site was performed, resulting in complete resolution of the stenosis and gradient. Early postangioplasty perfusion imaging demonstrated increased perfusion of the right lung to 35% of total pulmonary blood flow. It is theorized that initially a chronically hyperperfused lung may develop more capacious vessels and recruit new capillaries during the years of hyperperfusion such that a "perfect" angioplasty may result in less than symmetric perfusion. The inexpensive, noninvasive quantitative perfusion study is more sensitive and accurate in evaluating acquired (postsurgical) pulmonary artery stenoses.

Effect of diltiazem and low-dose aspirin on platelet aggregation and ATP release induced by paired agonists.

The authors studied the effects of diltiazem, administered alone and together with low-dose aspirin, on the platelet response to paired agonists. After a baseline period, 25 healthy volunteers were given oral diltiazem for 1 week (120, 240, or 360 mg/day), and then crossed over randomly between 1 week on diltiazem plus aspirin (81 mg/day), and 1 week on aspirin (81 mg/day) alone. Platelet function was tested on 2 consecutive days in each period. Synergistic platelet aggregation and ATP release were obtained at baseline using a subthreshold concentration of arachidonic acid combined with platelet activating factor, ADP, or epinephrine. Diltiazem resulted in significant decrease from baseline in platelet aggregation and ATP release using the arachidonic acid-epinephrine combination (35% and 40% decrease, respectively, p < 0.01) and a significant decrease in aggregation using the arachidonic acid-ADP combination (22% decrease, p < 0.01). The effects were neither dose-related, nor accompanied by any significant change in serum thromboxane B2 levels or bleeding times. There was no significant difference between the effects of aspirin alone and aspirin plus diltiazem on the synergistic platelet aggregation and ATP release induced by the paired agonists, or on thromboxane B2 levels or bleeding times. Diltiazem administered in vivo partially inhibits the synergistic platelet aggregation and ATP release induced by paired agonists; however, in contrast to a previous in vitro study it does not potentiate the platelet-inhibitory effect of aspirin.

Effect of dilantin on myocardial uptake of Tl-201 thallous chloride. A case report.

Dilantin has been reported to decrease myocardial uptake of Tl-201 thallous chloride by as much as 38.8% in rats. To date, no studies have been done in humans to document the effect of dilantin on the myocardial uptake of thallium or its effect clinically on the interpretation of images obtained while on dilantin. The authors report a case in which simultaneous exercise echocardiogram and Tl-201 myocardial scintigraphy and serial Tl-201 myocardial scintigraphy were performed but revealed no adverse effect on image quality or interpretation.