Combining spin echoes with gradient echoes in the context of the global coherent free precession pulse sequence.

To extend the signal longevity of magnetically excited spins in flowing fluids while in a state of global coherent free precession (GCFP), a refocusing radiofrequency (RF) pulse and bipolar gradient waveforms were combined with the GCFP sequence. The data demonstrate that RF refocusing in the presence of flowing blood is possible, but the improvement in signal amplitude depends on the static magnetic field homogeneity along the direction of motion and the displacement of the spins between the excitation and the RF refocusing pulse, as well as displacement during subsequent RF refocusing pulses. The least amount of phase dispersion and thus the longest lasting signal is obtained with the shortest echo spacing where only one line of data is recorded between two RF refocusing pulses. This approach was successfully used in a phantom and in vivo to image fast and slow blood flow. Depending on the experimental conditions, signal persistence is improved significantly compared to playing the same sequence without RF refocusing, but the improvement is limited by the product of blood flow velocity and the time between RF refocusing pulses.     

Sexual sequelae of antihypertensive drugs: Treatment effects on self-report and physiological measures in middle-aged male hypertensives

Antihypertensive drugs are commonly associated with adverse side effects in both clinical and laboratory studies. We investigated the sexual sequelae of several major classes of antihypertensive drugs (e.g., beta blockers, central alpha agonists, diuretics) in normal males and in hypertensive patients. We compared the effects of four widely used agents (methyldopa, propranolol, atenolol, hydrochlorothiazide-triamterene) and placebo, in a selected sample of 21 sexually dysfunctional male hypertensives, 13 of whom completed all five phases of the study. Each study drug was administered for a 1-month treatment period, followed by a 2-week, single-blind washout phase, according to a randomized, Latin square crossover design. Dependent variables for the study included a broad range of hormonal, NPT, and self-report measures of sexual response. Results indicated a lack of consistent drug effects on measures of sexual response, although more frequent sexual and nonsexual side effects were observed with methyldopa and propranolol. As in our previous studies, age was negatively correlated with both hormonal and NPT measures, whereas changes in blood pressure were not significantly related to sexual function scores. Results do not support the hypothesis that sexually dysfunctional males are at greater risk for adverse sexual sequelae when treated with centrally active agents or diuretics.     

Horizontal cell axon terminals in growing goldfish

In the retina of teleost fish, cone horizontal cell axons penetrate the inner nuclear layer, where they enlarge into fusiform terminal swellings. The present study shows that horizontal cell axon terminals enlarge disproportionately during postembryonic growth of the retina in juvenile and adult goldfish: the relative volume of axon terminals increases almost 20-fold, while the volume of the entire retina increases only about fourfold during a 2-3-yr period. The enlarging axon terminals fill in the gaps created as the numerical density of nuclei in the inner nuclear layer falls. Horizontal cell axon terminals are thought to participate in cone-dominated visual pathways, although their precise role is unclear. The results of this study suggest that a comparison of horizontal cell function in small and large fish might help to resolve this issue.     

Role of nuclear cardiology for determining management of patients with stable coronary artery disease

Both radionuclide angiography and myocardial perfusion imaging provide important insights that determine the management of patients with stable coronary artery disease. Both nuclear cardiology procedures have clearly demonstrated use in the noninvasvie identification of severe (left main or three-vessel) coronary artery disease and the noninvasive assessment of prognosis and thereby determine which patients should be sent to coronary angiography. Both radionuclide angiography and myocardial perfusion imaging provide prognostic information that is independent of resting left ventricular function and coronary anatomy and thereby influence the decision regarding which patients should be sent to coronary revascularization. This review considers the evidence supporting the uses of these nuclear cardiology procedures and provides suggestions regarding their cost-effective application.     

The value of myocardial perfusion single-photon emission computed tomography in screening asymptomatic patients with atrial fibrillation for coronary artery disease.

OBJECTIVES: We sought to determine if screening for coronary artery disease (CAD) with stress single-photon emission computed tomography (SPECT) is of value in patients with atrial fibrillation (AF) who do not have symptoms of chest pain or dyspnea. BACKGROUND: Although noninvasive stress testing is often done to screen for CAD in asymptomatic patients with AF and is considered to be appropriate in selected patients, its potential utility has not been demonstrated. METHODS: A retrospective study was conducted of 374 asymptomatic patients with AF referred for the detection of CAD. Mean follow-up was 5.7 +/- 3.8 years. The study group was compared with a control group of 374 asymptomatic age and gender-matched patients without AF. RESULTS: The mean summed stress score (SSS) was not significantly different between AF patients and control subjects (3.6 +/- 5.3 vs. 3.5 +/- 5.9; p = 0.35). Compared with controls, asymptomatic AF patients had similar rates of abnormal SPECT studies (51.6% vs. 48.4%; p = 0.38) and high-risk studies (14.4% vs. 14.4%; p = 1.0). The SSS was a significant predictor of outcome in both AF patients and control subjects. However, total mortality was significantly greater in AF patients (5-year overall mortality 27% vs. 18%, 10-year overall mortality 47% vs. 40%; p < 0.001), and this difference persisted (p = 0.01) after adjusting for multiple clinical variables and the SSS. CONCLUSIONS: Screening for CAD using stress SPECT in asymptomatic AF patients has a yield similar to age- and gender-matched control patients without AF. Although SSS predicts mortality in patients with and without AF, patients with AF have increased total mortality independent of the findings on stress SPECT. These results suggest that factors other than obstructive CAD are responsible for the increased mortality in AF.