Inferior vena cava assessment in the bedside diagnosis of acute heart failure.

OBJECTIVES: The objective of this study was to determine the test characteristics of the caval index and caval-aortic ratio in predicting the diagnosis of acute heart failure in patients with undifferentiated dyspnea in the emergency department (ED). METHODS: This prospective observational study was performed at an urban ED that enrolled patients, 50 years or older, with acute dyspnea. A sonographic caval index was calculated as the percentage decrease in the inferior vena cava (IVC) diameter during respiration. A caval-aortic ratio was defined by the maximum IVC diameter divided by the aortic diameter. The sensitivity, specificity, and likelihood ratios of these measurements associated with heart failure were estimated. RESULTS: Eighty-nine patients were enrolled in the study with a mean age of 68 years. A caval index of less than 33% had 80% sensitivity (95% confidence interval [CI], 63%-91%) and 81% specificity (95% CI, 68%-90%) in diagnosing acute heart failure, whereas an index of less than 15% had a 37% sensitivity (95% CI, 22%-55%) and 96% specificity (95% CI, 86%-99%). The sensitivity of a caval-aortic ratio of more than 1.2 was 33% (95% CI, 18%-52%) and the specificity was 96% (95% CI, 86%-99%). Positive likelihood ratios were 10 for a caval index of less than 15%, 4.3 for an index of less than 33%, and 8.3 for a caval-aortic ratio of more than 1.2. CONCLUSION: Bedside assessments of the caval index or caval-aortic ratio may be useful clinical adjuncts in establishing the diagnosis of acute heart failure in patients with undifferentiated dyspnea.

The respiratory, metabolic, and neuroendocrine effects of a new generation electronic control device.

INTRODUCTION: Electronic control devices (ECDs) have become popular in law enforcement because these devices have filled a gap left by other law enforcement devices, tactics, or tools and have been shown to reduce officer and suspect injuries. The TASER X3 is the latest generation device from the manufacturer. This device has the capability of firing three cartridges in a "semi-automatic" mode. This study is the first of the metabolic, neuroendocrine, and respiratory effects of this newer generation device. METHODS: This was a prospective, observational study of human subjects. A master instructor shot subjects with a TASER X3 in the anterior thorax with either one or two cartridges. Each subject received a 10-s exposure from the device. Vital signs were measured before and after the exposure. Venous pH, lactate, electrolytes, and catecholamines were measured before and after the exposure. Creatine kinase (CK) was measured before and at 24h post-exposure. Continuous spirometry was also performed. RESULTS: Fifty-three subjects completed the study. There were no important changes in vital signs or electrolytes. Venous pH, lactate, and catecholamine changes were similar to previous studies on earlier generation devices. There was no evidence of impairment of breathing. CK changes were greater for multiple "circuits". CONCLUSIONS: In our study, the respiratory, metabolic, and neuroendocrine effects were similar to previous generation devices. There was an increase in CK with more probes deployed.

Human cardiovascular effects of a new generation conducted electrical weapon.

OBJECTIVES: The conducted electrical weapon (CEW) is used by law enforcement to control potentially violent people. Much of the research in CEW safety has focused on the TASER X26, which uses a single deployment cartridge. New Generation CEW (NGCEW) technology has been developed that uses a different circuit and multiple cartridges that can be simultaneously deployed. The objective of this study is to examine the cardiovascular effects of the NGCEW in different deployment possibilities. METHODS: This was a prospective study of human subjects during NGCEW training courses. Subjects received a NGCEW probe deployment to the frontal torso in 1 of 3 configurations: 2, 3,or 4 embedded probes and then underwent a 10-s exposure. Before and after vital signs, electrocardiograms (ECGs), and serum troponin I values were obtained. Real-time echocardiography was utilized before, during and after the exposure to evaluate heart rate and rhythm. RESULTS: Initially, a 1st version NGCEW (NGCEWv1) that was in the final stages of manufacturer verification was used at the training courses. It had not been publicly released. During a NGCEWv1 exposure with 2 probes, there was an apparent brief episode of cardiac capture. Testing was halted and the manufacturer was notified. The device was redesigned and the study continued when a redesigned, 2nd version (NGCEWv2) was used. The NGCEW1 was studied in 8 subjects. The NGCEWv2 was studied in 45 subjects with no evidence of cardiac capture. There were no important post-exposure vital sign, troponin I or ECG changes found in any volunteers. CONCLUSIONS: An apparent brief myocardial capture event occurred with the NGCEWv1. This device was not released and was redesigned. The NGCEWv2 appears to exhibit a reasonable degree of cardiac safety with frontal torso exposures and multiple probe combination configurations.