Effect of intravenous adenosine infusion on myocardial perfusion and function. Hemodynamic/angiographic and scintigraphic study.

BACKGROUND: Myocardial perfusion imaging during adenosine-induced hyperemia with dipyridamole or adenosine is an accepted method to diagnose coronary artery disease (CAD) and risk assessment. The mechanism of perfusion abnormality may be caused by disparate flow responses or coronary steal. This study examined the relation between 201Tl perfusion pattern and hemodynamic/angiographic changes during intravenous adenosine infusion. METHODS AND RESULTS: Patients with suspected CAD underwent sequential hemodynamic, coronary arteriographic, and left ventriculographic studies simultaneously with 201Tl imaging during adenosine infusion (140 micrograms.kg-1.min-1 for 6 minutes). There were 33 patients with CAD and 12 patients without CAD. The 201Tl images (using single-photon emission computed tomography) were abnormal in 31 patients with CAD (sensitivity, 94%) and normal in the patients without CAD (specificity, 100%). In patients with and without CAD, there were significant increases in heart rate and cardiac output (p less than 0.0001) and decreases in systemic vascular resistance and blood pressure (p less than 0.0001). There was a 77 +/- 38% increase in pulmonary capillary wedge pressure in normal subjects and a 125 +/- 83% increase in patients with CAD (p = 0.02). ST segment depression was observed in 11 patients with CAD (33%). In CAD patients, there was no change in percent diameter or area stenosis measured quantitatively during adenosine infusion. In 15 patients, contrast left ventriculography was repeated during adenosine infusion. In these patients, 201Tl perfusion defects were seen in 31 of 75 segments (41%) whereas only six of 75 segments (8%) developed regional wall motion abnormality (p less than 0.001); the remaining segments showed either no change or improved function. The left ventricular ejection fraction did not change significantly (73% versus 75%). CONCLUSIONS: There is a disparity between the effects of adenosine on left ventricular perfusion and function; most patients with CAD have perfusion defects whereas the global and regional systolic function remains unchanged or improves. Diastolic left ventricular dysfunction is a probable mechanism of the increase in pulmonary capillary wedge pressure.

Delayed resolution of obstructing thrombus following acute closure.

A case of acute thrombotic closure following percutaneous coronary angioplasty demonstrating delayed clearance of obstructing thrombus is reported. Although common in other clinical scenarios this has not been reported following coronary angioplasty.

Myocardial imaging with Tc-99m teboroxime: technique and initial results.

This study examined the results of Tc-99m teboroxime imaging in 22 patients aged 59 +/- 9 years and compared the results with those of thallium-201. The exercise and rest teboroxime studies were obtained within 3 hours of each other using a dose of 15 mCi/study. Because of the very short wash-out half-life of teboroxime, imaging was begun within 1 to 2 minutes after injection. Both SPECT and planar images were obtained; the SPECT protocol was modified by changing the number of frames, the time per frame, or the filters used for reconstruction of images. The planar images were obtained in the supine or upright position. Shorter acquisition time for SPECT (10 sec/frame) and the use of a Butterworth filter with a frequency cutoff of 0.3 cycle/cm and a power of 10 yielded best image quality. There was a close agreement with thallium results in identifying an abnormal or normal perfusion pattern in 89% of vascular territories. The scans were abnormal by both techniques in 12 patients, normal in nine patients, and discordant in only one patient. Thus Tc-99m teboroxime myocardial imaging is feasible at rest and during exercise using either SPECT or planar imaging. Shorter acquisition time and appropriate filtering for SPECT imaging and the upright position in planar imaging improve image quality and are convenient for the patient.