Application of appropriate use criteria for stress myocardial perfusion imaging at two academic medical centers: compliance and association with image findings.

PURPOSE: Explore the extent to which stress myocardial perfusion imaging (MPI) studies for coronary heart disease detection met published appropriate use criteria (AUC), and the association between AUC classification and image findings. DATA SOURCES: Retrospective, descriptive review of stress studies performed at the University of Washington Medical Center (UWMC n= 1377) and the Veterans Health Administration of Puget Sound (VA n= 1445) in the 31 months following AUC publication. CONCLUSIONS: At UWMC and VA, 69% and 89% of MPI studies, respectively, were classified as appropriate, 16% and 3% as inappropriate, and 15% and 8% as uncertain. All differences were significant, p < .001. At UWMC, 11% of appropriate studies and 10% of inappropriate or uncertain studies were abnormal (demonstrating myocardial ischemia or myocardial infarction), p= .93; these analyses were not performed on VA studies. IMPLICATIONS FOR PRACTICE: Most studies at both sites were classified as appropriate. At UWMC, the likelihood of a study classified as appropriate demonstrating an abnormality was not significantly different from a study classified as uncertain or inappropriate. AUC are imperfect tools but are increasingly created and referenced; as such, it is vital that practicing nurse practitioners are knowledgeable about their creation, application, and evaluation.

Heart rate variability and 24-hour minimum heart rate.

Heart rate variability (HRV) indices based on 24-hr electrocardiograph recordings have been used in clinical research studies to assess the aggregate activity of the autonomic nervous system. Although 24-hr HRV is generally considered noninvasive, use in research protocols typically involves considerable data collection and processing expenses and substantial participant burden. The purposes of this research methods evaluation were to describe the relationships between 24-hr minimum heart rate (HR) and several 24-hr time domain HRV indices (Ln SDNN, Ln SDANN, Ln SDNNIDX, Ln RMSSD, and Logit50) across several research data sets (normal women, normal men, children enrolled in a study of recurrent abdominal pain, women with irritable bowel syndrome, sudden cardiac arrest survivors, and heart failure patients) and to explore the possibility that 24-hr minimum HR might serve as a simpler alternative or adjunct to HRV measures in some situations. The correlations of global HRV measures (e.g., Ln SDNN, Ln SDANN) with 24-hr minimum HR were consistently larger (typical r approximately -.80) than with average HR (typical r approximately -.50). In repeated measurements, change in minimum HR was also correlated with change in general HRV (typical r approximately -.60). However, modest differentiation of minimum HR and HRV measures was noted in patients taking certain classes of cardiac medications (e.g., anti-arrhythmics, beta blockers). Twenty-four-hour minimum HR is correlated with general time domain HRV measures and might be useful as a simpler proxy, surrogate, or auxiliary variable in some clinical research applications, especially those in which participants are not receiving cardiac medications.

Abdominal pain impacts quality of life in women with irritable bowel syndrome.

OBJECTIVES: Patients with irritable bowel syndrome (IBS) report lower health-related quality of life (QoL) as compared to healthy controls. The aims of this analysis were to describe which IBS symptoms were rated on a daily diary as most distressing/severe by IBS women, and determine which IBS symptoms were most predictive of lower QoL and have the greatest impact on daily life. METHODS: This report is a secondary analysis of prospective and retrospective symptom severity and impact data, collected on 242 women with IBS, aged 18-48, who were studied between 1997 and 2004. RESULTS: On the daily diary, intestinal gas was the most frequent IBS symptom with subjects reporting at least minimal intestinal gas on 74% of days and moderate or worse severity on 27% of days. Abdominal pain occurred at least minimally on 62% of days. Diarrhea was the least common. Across women, abdominal pain was most strongly related to life impact variables and QoL, followed by intestinal gas and bloating. Analysis of day-to-day variation within women showed that abdominal pain was most strongly correlated with daily life impact variables and constipation had the weakest correlation. While diarrhea had a lower correlation with life impact, this was due to the low prevalence of diarrhea. When it occurs, diarrhea has a large impact. Partial correlation analysis showed that the impact of diarrhea is independent of abdominal pain. CONCLUSION: Abdominal pain is the most disruptive IBS symptom. Diarrhea also has an independent and significant impact when it occurs, especially in those with diarrhea-predominant IBS.

Logit50: a nonlinear transformation of pNN50 with improved statistical properties.

The traditional time domain heart rate variability index pNN50 is a percentage scale-based measure of large beat-to-beat changes in heart period that may reflect parasympathetic neural activity impinging on the sino-atrial node. However, pNN50 exhibits nonlinear saturation effects near 0% and 100% that may adversely affect its statistical properties. The purpose of this paper is to propose a revision of pNN50, Logit50, that is the natural logarithm of the odds of the occurrence of large beat-to-beat differences in R-R interval. Using five clinical and normal sample data sets, the revised Logit50 index is shown to retain the computational simplicity and interpretability of the pNN50, but to have better metric properties in statistical and clinical applications. In particular, the Logit50 is demonstrated to be relatively unaffected by the positive distributional skew that is common in most statistical applications of pNN50.