Angioplasty Guidewire Velocity: A New Simple Method to Calculate Absolute Coronary Blood Velocity and Flow

The Thrombolysis In Myocardial Infarction (TIMI) frame count is a relative index of coronary flow that measures time by counting the number of frames required for dye to travel from the ostium to a standardized coronary landmark in a cineangiogram filmed at a known speed (frames/s). We describe a new method to measure distance along arteries so that absolute velocity (length ÷ time) and absolute flow (area × velocity) may be calculated in patients undergoing percutaneous transluminal coronary angiography (PTCA). After PTCA, the guidewire tip is placed at the coronary landmark and a Kelly clamp is placed on the guidewire where it exits the Y-adapter. The guidewire tip is then withdrawn to the catheter tip and a second Kelly clamp is placed on the wire where it exits the Y-adapter. The distance between the 2 Kelly clamps outside the body is the distance between the catheter tip and the anatomic landmark inside the body. Velocity (cm/s) may be calculated as this distance (cm) ÷ TIMI frame count (frames) × film frame speed (frames/s). Flow (ml/s) may be calculated by multiplying this velocity (cm/s) and the mean cross-sectional lumen area (cm²) along the length of the artery to the TIMI landmark. In 30 patients, velocity increased from 13.9 ± 8.5 cm/s before to 22.8 ± 9.3 cm/s after PTCA (p <0.001). Despite TIMI grade 3 flow both before and after PTCA in 18 patients, velocity actually increased 38%, from 17.0 ± 5.4 to 23.5 ± 9.0 cm/s (p = 0.01). For all 30 patients, flow doubled from 0.6 ± 0.4 ml/s before to 1.2 ± 0.6 ml/s after PTCA (p <0.001). In the 18 patients with TIMI grade 3 flow both before and after PTCA, flow increased 86%, from 0.7 ± 0.3 to 1.3 ± 0.6 ml/s (p = 0.001). Distance along coronary arteries (length) can be simply measured using a PTCA guidewire. This length may be combined with the TIMI frame count to calculate measures of absolute velocity and flow that are sensitive to changes in perfusion. TIMI grade 3 flow is composed of a range of velocities and flows.     

The review process used by U.S. health care plans to evaluate new medical technology for coverage

OBJECTIVE: To examine the process and information used by medical directors (MDs) of private health plans to make medical coverage determinations for new medical technologies, and to assess the influence of plan characteristics on the process. DESIGN: Cross-sectional national survey. PARTICIPANTS: Two hundred thirty-one MDs at private health plans representing 66% and 72% of the U.S. population covered by HMOs and indemnity plans, respectively. MEASUREMENTS: Actual and optimal review process, final decision authority, sources, and evidence used for technology coverage decisions. RESULTS: In 96% of plans, MDs take part in the medical policy review process for new technology. However, MDs have final authority over coverage decisions in only 27% of plans. Indemnity plans are more likely to assert that MDs should be responsible for final decisions, odds ratio (OR)=3.3 (95% confidence interval [95% CI] 1.4, 10). Optimal sources of information on new technology were journals, medical society statements or practice guidelines, and opinions of national experts. Actual sources of information used differed from optimal ones; local experts were used more often than is considered optimal (p<.001). For-profit plans were more likely than nonprofit plans to use national experts, OR 2.5 (95% CI 1.3, 5.0), and practice guidelines, OR 5.0 (95% CI 2.5, 10). Randomized trials (94% of MDs) meta-analyses (61%), and reviews (42%) were considered the best evidence for making coverage decisions. Barriers to making optimal decisions were lack of timely evidence on effectiveness and cost-effectiveness, not legal or regulatory issues; HMO, small, and nonprofit plans were two to three times more likely to list lack of cost-effectiveness data than their counterparts (p<.05). CONCLUSIONS: Although MDs are nearly always involved in the technology evaluation process, a minority of MDs retain final authority over coverage decisions. Evidence from strong scientific research designs is the most frequently cited basis for decisions, but there is need for more timely, rigorous scientific evidence on medical interventions. How a health plan evaluates a new medical technology for coverage varies with identifiable plan characteristics. Presented in part at the 18th annual meeting of the Society of General Internal Medicine and the American Federation for Clinical Research national meeting, San Diego, Calif., May 1995. Supported in part by the Office of Technology Assessment, U.S. Congress, Washington, DC, and computational assistance from General Clinical Research Center grants 5M01RR00722 and RR0035 from the National Center for Research Resources, Bethesda, Md. This paper does not represent policy of either the Agency for Health Care Policy and Research or the U.S. Department of Health and Human Services (DHHS). The views expressed herein are those of the authors and no official endorsement by AHCPR or DHHS is intended or should be inferred.     

Assessment of aldehyde dehydrogenase in viable cells

Cytosolic aldehyde dehydrogenase (ALDH), an enzyme responsible for oxidizing intracellular aldehydes, has an important role in ethanol, vitamin A, and cyclophosphamide metabolism. High expression of this enzyme in primitive stem cells from multiple tissues, including bone marrow and intestine, appears to be an important mechanism by which these cells are resistant to cyclophosphamide. However, although hematopoietic stem cells (HSC) express high levels of cytosolic ALDH, isolating viable HSC by their ALDH expression has not been possible because ALDH is an intracellular protein. We found that a fluorescent aldehyde, dansyl aminoacetaldehyde (DAAA), could be used in flow cytometry experiments to isolate viable mouse and human cells based on their ALDH content. The level of dansyl fluorescence exhibited by cells after incubation with DAAA paralleled cytosolic ALDH levels determined by Western blotting and the sensitivity of the cells to cyclophosphamide. Moreover, DAAA appeared to be a more sensitive means of assessing cytosolic ALDH levels than Western blotting. Bone marrow progenitors treated with DAAA proliferated normally. Furthermore, marrow cells expressing high levels of dansyl fluorescence after incubation with DAAA were enriched for hematopoietic progenitors. The ability to isolate viable cells that express high levels of cytosolic ALDH could be an important component of methodology for identifying and purifying HSC and for studying cyclophosphamide-resistant tumor cell populations.     

HLA-B13 and chronic calcific pancreatitis

In view of a possible role of genetic factors in the etiology of chronic calcific pancreatitis, we undertook a study of the frequency of HLA antigens in this disease. Sixty-four patients with chronic calcific pancreatitis were typed for the HLA-A,-B and-C loci. Fourteen of these 64 patients (21.9%) were found to have antigen B13 compared to 7.5% of 425 controls. These results have aP value of 0.00059 which remains significant (P=0.020) even when multiplied by the total number of antigens tested. Sex, alcoholism, age at the clinical onset of the disease, presence of pain, and diabetes had no apparent influence on the distribution of HLA alleles. The significant association between chronic calcific pancreatitis and HLA antigen B13 further supports the role of genetic factors in the etiology of the disease.     

Management of chronic heart failure in the community: role of a hospital based open access heart failure service

Objective: To evaluate the role of an open access heart failure service based at a teaching hospital for the diagnosis and treatment optimisation of patients with heart failure in the community and to identify measures that may further enhance the effectiveness of such a service.

Subjects: 963 patients with suspected heart failure seen over an eight year period referred by their general practitioners to the cardiology department at a district general hospital.

Main outcome measures: Presence or absence of left ventricular systolic dysfunction (LVSD) (left ventricular ejection fraction < 50% on echocardiography), and determination of the risk factors and predictors of LVSD.

Results: The majority of the patients were women (60% v 40%) and elderly (mean age 68.8 years). On echocardiography, only 30.8% were found to have LVSD. Patients were more likely to have LVSD if they were men (42.3% v 23.1%, p < 0.001, relative risk (RR) 1.8), were > 60 years of age (33.5% v 20.8%, p < 0.001, RR 1.6), or had a history of diabetes (49.4% v 29.1%, p < 0.001, RR 1.7), ischaemic heart disease (36.5% v 29.1%, p = 0.04, RR 1.3), or atrial fibrillation (52.6% v 27.8%, p < 0.001, RR 1.9). An abnormal ECG (48.4% v 19.5%, p < 0.001, RR 2.5) and cardiothoracic ratio > 0.5 on chest radiograph (44.3% v 17.8%, p < 0.001, RR 2.5) were found to be good predictors of LVSD. A normal ECG (negative predictive value 80.5%) and a cardiothoracic ratio of < 0.5 (negative predictive value 82.2%) can be used as baseline measures to identify patients with lower risk of developing LVSD (combined negative predictive value 87.9%).

Conclusions: An open access heart failure clinic is effective for the diagnosis and management of chronic heart failure in community based patients. The presence of risk factors and simple baseline tests can be used to identify patients with LVSD in the community. The introduction of a protocol based on these findings into a referral system can improve the efficiency and cost effectiveness of such a service.