Gargle pool PCR testing in a hospital during medium and high SARS-CoV-2 incidence.

BACKGROUND: Hospitals need to be protected from SARS-CoV-2 infections to protect vulnerable patients. Thus, a safe, efficient, and cost-effective SARS-CoV-2 testing system for hospitals, in addition to standard hygiene measures and vaccination of staff, is necessary. Here we report on the feasibility and performance of a pool real-time reverse-transcriptase polymerase-chain-reaction (rRT-PCR) test system at, medium and high incidence. METHODS: We implemented a testing concept based on gargling at home and pooling of samples in the hospital before PCR testing in the laboratory. We used two PCR systems (point of care and standard 96-well plate system) to adapt to challenges in the hospital setting and respond to a rising incidence in the Omicron wave. FINDINGS: During our 10-week study period, we performed 697 pool PCRs (8793 tests in total) and identified 65 asymptomatic staff members by pool PCR and 94 symptomatic staff members by positive individual PCR. Virus loads in those detected by pool testing were significantly lower (P<0.001). The test system remained workable even during the peak of the Omicron wave and no outbreaks occurred in any specific area of the hospital during the study period. Unvaccinated individuals were over-represented in the positively tested (37% vs 22% positive tests, P=0.04). The test procedure was well accepted by a majority of the hospital staff (84%). CONCLUSION: Repeated gargle pool rRT-PCR testing can be implemented quickly in hospitals and is an effective, easily adaptable and well-accepted test system for hospitals, even during phases with very high infection rates.

Mechanically induced calcium movements in astrocytes, bovine aortic endothelial cells and C6 glioma cells.

Forces applied to resting primary astrocytes, bovine aortic endothelial cells and C6 glioma cells with collagen-coated magnetite particles produce a fast transient change of intracellular Ca(2+). It peaks in the micromolar range as measured by Fura-2. This mechanical response adapts within seconds so that repeated stimulation causes smaller responses requiring >10 min for recovery. When cytoplasmic Ca(2+) is high after treating with ATP, cyclopiazonic acid and thapsigargin, stimulation causes a transient decrease in Ca(2+). In these three cell types, no influx of ions is required for Ca(2+) elevation showing the response is not caused by activation of plasmalemmal mechanosensitive channels. Approximately half the cells tested showed similar behavior, while the other half, such as fibroblasts, required extracellular Ca(2+). The Ca(2+) response is not temperature sensitive suggesting the possible involvement of intracellular mechanosensitive channels. We tested a number of second messenger reagents and were only able to block the response in BAECs, but not C6 glioma cells, with Xestospongin C, a blocker of IP(3)-activated channels. Despite the lack of a causal involvement of plasmalemmal mechanosensitive channels, mechanical stimulation immediately activates a persistent Mn(2+) influx pathway. This Mn(2+) pathway may be mechanosensitive channels, Ca(2+)-activated cation channels or depletion-activated Ca(2+) channels.

Effect of short-term medroxyprogesterone acetate on left ventricular mass: role of insulin-like growth factor-1.

Previous studies using 17beta-estradiol and medroxyprogesterone acetate (MPA) have shown that hormone replacement therapy (HRT) increases left ventricular mass (LVM). To determine if insulin-like growth factor-1 (IGF-1) is associated with the increase in LVM, we measured IGF-1 and IGF-binding protein-3 (IGFBP-3) levels in 19 postmenopausal women before and after 8 weeks of oral treatment with MPA 5 mg/d. LVM was measured by two-dimensional echocardiography. Changes in IGF-1, IGFBP-3, and LVM from baseline were analyzed by paired ttest. Regression analysis was used to determine if changes in the IGF-1 axis with MPA treatment affect the increase in LVM. LVM increased 4.4% during the study (P = .006 vbaseline). IGF-1 increased 17% with MPA (P = .008), whereas IGFBP-3 did not change. The IGF-1/IGFBP-3 ratio increased 16.8% (P = .0003). Regression analysis of LVM with IGF-1, IGFBP-3, and the IGF-1/IGFBP-3 ratio suggested that IGF-1 during MPA therapy explains 2.4% and the IGF-1/IGFBP-3 ratio explains 3.2% of the variation in LVM. There was no effect of IGFBP-3 on LVM. Most of the variation in LVM with MPA (90.5%) was explained by baseline LVM. The IGF-1/IGFBP-3 ratio on MPA treatment was inversely related to the change in LVM: women with a lower LVM at baseline had the greatest increase in LVM with MPA. These findings suggest that MPA increases IGF-1 and LVM. Because the increase in IGF-1 with MPA treatment explains a fraction of the increase in LVM, other mechanisms must also be operative.

Effect of short-term hormone replacement therapy on left ventricular mass and contractile function.

OBJECTIVE: To determine the effect of hormone replacement therapy (HRT) on cardiac structure and function and whether these changes are related to changes in blood volume. DESIGN: Open-label pilot study. SETTING: Academic medical center. PATIENT(S): Eighteen healthy postmenopausal women. INTERVENTION(S): We administered medroxyprogesterone acetate orally, 5 mg/d for 2 months followed by 2 months of oral sequential 17beta-estradiol, 1 mg/d plus medroxyprogesterone acetate, 10 mg/d for the last 12 days of each month. MAIN OUTCOME MEASURE(S): Cardiac output, stroke volume, heart rate, end diastolic volume, end systolic volume, ejection fraction, and left ventricular mass were measured by echocardiography; blood and plasma volumes were measured using 125I-albumin dilution. RESULT(S): Cardiac output, stroke volume, left ventricular mass, end diastolic volume, and ejection fraction increased by 12.8%, 11.7%, 9.4%, 7.2%, and 10.9%, respectively, by 16 weeks. End systolic volume decreased, whereas heart rate was unaffected. There was a significant increase in blood volume (5.2%) and plasma volume (4.8%) from baseline during treatment, which could explain the increased cardiac output but not the increased ejection fraction. CONCLUSION(S): Hormone replacement therapy causes modest but significant increases in cardiac output, ejection fraction, and left ventricular mass. These pilot data suggest a direct myocardial effect of HRT that is preload independent.

Ca2+ uptake in GH3 cells during hypotonic swelling: the sensory role of stretch-activated ion channels.

Hypotonic cell swelling triggers an increase in intracellular Ca2+ concentration that is deemed responsible for the subsequent regulated volume decrease in many cells. To understand the mechanisms underlying this increase, we have studied the Ca2+ sources that contribute to hypotonic cell swelling-induced Ca2+ increase (HICI) in GH3 cells. Fura 2 fluorescence of cell populations revealed that extracellular, but not intracellular, stores of Ca2+ were required. HICI was abolished by nifedipine, a blocker of L-type Ca2+ channels, and Gd3+, a nonspecific blocker of stretch-activated channels (SACs), suggesting two components for the Ca2+ membrane pathway: L-type Ca2+ channels and SACs. Using HICI as an assay, we found that venom from the spider Grammostola spatulata could block HICI without blocking L-type Ca2+ channels. The venom did, however, block SAC activity. This suggests that Ca(2+)-permeable SACs, rather than L-type Ca2+ channels, are the sensing elements for HICI. These results support the model for volume regulation in which SACs, activated by an increase of the membrane tension during hypotonic cell swelling, trigger HICI, leading to a volume decrease.

Effects of exercise on left ventricular performance determined by echocardiography in chronic, severe mitral regurgitation secondary to mitral valve prolapse.

Data on the effects of exercise on left ventricular (LV) volumes and ejection performance in patients with severe mitral regurgitation (MR) are limited. With use of a matched-pairs design, 10 asymptomatic patients with chronic, severe MR and normal LV systolic function who were not receiving vasodilator therapy (group 1) and 10 matched normal control subjects with no structural heart disease (group 2) performed symptom-limited upright bicycle ergometry with quantitative echocardiographic analysis. An additional 8 patients with severe, chronic MR and normal LV systolic function who were receiving vasodilator therapy at the time of testing (group 3) were studied for comparison. The 3 cohorts exercised for similar periods of time. Group 1 and 3 patients had similar end-diastolic volumes at rest, both of which were significantly greater than those of normal controls. Although resting LV end-systolic volume was greater in groups 1 and 3 than in normal controls, the 3 groups had similar relative percent reductions in end-systolic volume during exercise (30 +/- 12%, 32 +/- 13%, and 30 +/- 24%; p = NS). A similar percent increase in LV ejection fraction was also observed in all 3 cohorts (18 +/- 9%, 15 +/- 9%, and 14 +/- 6%; p = NS). Forward stroke volume increased significantly in group 1 (59 +/- 21 and 71 +/- 18 ml; p <0.001) and in group 3 (59 +/- 17 and 68 +/- 13 ml; p < 0.05). Thus, in asymptomatic patients with chronic, severe MR and normal LV ejection fraction at rest, there is an improvement in LV ejection fraction and an increase in forward stroke volume during exercise. These effects are comparable to those observed in normal controls. Directional differences in the cohort receiving no activity therapy were indistinguishable from either patients receiving vasodilator therapy or normal control subjects.

Observations suggesting a high incidence of exercise-induced severe mitral regurgitation in patients with mild rheumatic mitral valve disease at rest.

OBJECTIVES: The aim of this study was to determine the hemodynamic effects of upright bicycle ergometry in symptomatic patients with mild, mixed mitral stenosis and regurgitation. BACKGROUND: Patients with seemingly mild rheumatic mitral valve disease often complain of exertional dyspnea or fatigue. These symptoms are usually ascribed to flow-dependent increases in the gradient across the stenotic mitral valve. Although catheterization studies in these patients may demonstrate an increase in mitral valve gradient proportional to an increase in cardiac output, this approach does not specifically address the underlying mechanism of any observed increases in mitral gradient or left atrial (i.e., pulmonary capillary wedge) pressure. Exercise echocardiography is uniquely suited to the dynamic assessment of exercise-induced hemodynamic changes. METHODS: Fourteen symptomatic patients with exertional dyspnea and mild mitral stenosis and regurgitation at rest performed symptom-limited upright bicycle ergometry with quantitative two-dimensional, Doppler and color Doppler echocardiographic analysis. RESULTS: Average pulmonary artery systolic pressure in the 13 patients with adequate spectral signals of tricuspid regurgitation increased from 36 +/- 5 mm Hg (mean +/- SD) at rest to 63 +/- 14 mm Hg at peak exercise (p < 0.001). The mean transmitral pressure gradient in all patients increased from 4.5 +/- 1.4 mm Hg at rest to 12.7 +/- 2.7 mm Hg at peak exercise (p < 0.001). Five patients developed severe mitral regurgitation during exercise. CONCLUSIONS: Patients with exertional dyspnea and mild mitral stenosis and regurgitation at rest demonstrate a marked increase in pulmonary artery systolic pressure and mean transmitral pressure gradient during dynamic exercise. In a subset of these patients, marked worsening of mitral regurgitation appears to be the underlying mechanism of this hemodynamic deterioration. Because of the small sample size, this novel observation must be considered preliminary with respect to the true prevalence of exercise-related development of severe mitral regurgitation. If additional studies confirm the importance of this phenomenon, it has important implications for the management of patients with rheumatic mitral valve disease.

Validation of global and segmental left ventricular contractile function using gated planar technetium-99m sestamibi myocardial perfusion imaging.

OBJECTIVES: The purpose of this study was to test the hypothesis that segmental wall motion analysis determined from gated planar technetium-99m sestamibi myocardial imaging is reproducible and agrees well with echocardiographic data. BACKGROUND: Technetium-99m sestamibi is a new radiopharmaceutical recently approved for myocardial perfusion imaging. Its advantages include a dosimetry that allows use of a dose 10 to 15 times higher than that of thallium-201. As a result, myocardial counts are markedly improved and images can be collected in a gated mode to potentially allow assessment of global and segmental ventricular function. However, the reproducibility and accuracy of technetium-99m sestamibi imaging for measurement of global and segmental left ventricular function have not been evaluated or compared with those of a standard ventricular function technique, such as echocardiography. METHODS: We studied 136 patients referred for clinical technetium-99m sestamibi imaging. One-day rest-stress planar technetium-99m sestamibi protocols were used, gating the stress images. After technetium-99m sestamibi imaging, all patients had standard rest two-dimensional echocardiography. Global and segmental technetium-99m sestamibi and echocardiographic left ventricular contraction was graded qualitatively as normal or abnormal using a four-point grading system. RESULTS: Interobserver and intraobserver agreement was extremely high for global and segmental technetium-99m sestamibi wall motion analysis, with absolute agreements ranging from 0.92 to 1.00 and corresponding kappa values of 0.74 to 1.00 (p < 0.00001). Agreement with global and segmental echocardiographic wall motion was similarly very high, with absolute agreements ranging from 0.93 to 1.00 and corresponding kappa values of 0.75 to 1.00 (p < 0.00001). CONCLUSIONS: Gated technetium-99m sestamibi cardiac imaging provides information with regard to rest global and segmental left ventricular systolic function that is highly reproducible and agrees very well with results of two-dimensional echocardiography.

Relation between left ventricular shape and exercise capacity in patients with left ventricular dysfunction.

OBJECTIVES: The aim of this study was to identify dynamic predictors of exercise duration in patients with systolic left ventricular dysfunction and to test the hypothesis that left ventricular shape is an independent determinant of exercise duration in these patients. BACKGROUND: Measurements of left ventricular volumes and ejection fraction at rest do not predict exercise capacity in patients with systolic left ventricular dysfunction. Left ventricular shape at rest has been reported to be an independent determinant of exercise duration in these patients. The significance of alterations in left ventricular shape that occur during dynamic exercise has not been investigated. METHODS: Twenty-one patients with a documented ejection fraction < 40% performed symptom-limited graded upright bicycle exercise with simultaneous quantitative two-dimensional echocardiography. End-diastolic volume, end-systolic volume, stroke volume, ejection fraction and sphericity index were measured at rest and peak exercise. RESULTS: Eleven patients exercised beyond stage II (6 min, 50 W), averaging 8.9 +/- 1.9 min; 10 patients were unable to complete stage II, averaging 4.9 +/- 0.9 min. No patient developed clinical evidence of ischemia during the exercise period. Of the echocardiographic variables considered, only end-systolic and end-diastolic sphericity indexes at peak exercise (r = 0.809 and 0.711, respectively) and the change in end-systolic sphericity index during exercise (r = 0.697) were strongly correlated with exercise duration. CONCLUSIONS: Conventional descriptors of left ventricular function are poor predictors of exercise capacity. Dynamic changes in heart shape correlate strongly with exercise duration and may be important determinants of exercise capacity in patients with systolic left ventricular dysfunction.

Exercise echocardiography in combined mild mitral valve stenosis and regurgitation.

Dynamic mitral regurgitation (MR) is typically associated with either severe systolic left ventricular dysfunction or episodes of acute myocardial ischemia. We report three patients with mild combined mitral stenosis and regurgitation and normal global left ventricular systolic function who presented with severe exertional dyspnea. Upright bicycle exercise echocardiography revealed development of severe dynamic MR in all three cases with Doppler evidence of severe pulmonary hypertension. There was no echocardiographic or electrocardiographic evidence of ischemia. Exercise echocardiography is an established tool for assessing dynamic changes in transvalvar pressure gradients. These results suggest that exercise echocardiography may also be useful for evaluating changes in severity of MR and for the assessment of dynamic changes in pulmonary artery systolic pressures.