Clinical utility of inappropriate positron emission tomography myocardial perfusion imaging: test results and cardiovascular events

BACKGROUND

Appropriate use criteria for myocardial perfusion imaging (MPI) were developed to categorize scenarios where MPI might be beneficial (appropriate) or not (inappropriate). Few investigations have evaluated the clinical utility of this categorization strategy, particularly with positron emission tomography (PET) MPI.

METHODS AND RESULTS

We conducted this retrospective cohort investigation in a Veterans Affairs (VA) medical center, on predominantly male subjects who underwent PET-MPI. We correlated appropriateness to test result and cardiovascular events. Of 521 subjects, 414 (79.5%) were appropriate, 54 (10.4%) were uncertain, and 53 (10.2%) were inappropriate. PET-MPI was abnormal more often when appropriate or uncertain (28% and 34.6%, respectively, vs 7.7% for inappropriate, P = .003). Among abnormal inappropriate tests, none detected occult ischemia. By Cox regression, summed difference score ≥5 (HR 5.06, 95% CI 2.72-9.44) and an abnormal test result (HR 4.48, 95% CI 2.19-9.14) were associated with higher likelihood of catheterization. Log-rank analysis demonstrated similar likelihood of catheterization when comparing abnormal vs normal test result (P < .0001) and between appropriate, uncertain, and inappropriate tests (P = .024).

CONCLUSIONS

Inappropriate PET-MPI was rarely abnormal, associated with low catheterization rates, and failed to detect occult ischemia for any subjects. The clinical utility of inappropriate PET-MPI is negligible.

A quality improvement project for reducing cardiac computed tomography radiation dose in a community-based, multihospital setting

Radiation associated with computed tomography coronary angiography (CTCA) is a persistent concern. Strategies for reducing radiation exposure have been described, primarily in academic settings. We developed a standard protocol for CTCA acquisition focused on radiation reduction strategies in a community-based, multihospital setting and hypothesized that the protocol would be effective at reducing radiation in this setting. The protocol included the use of body mass index based tube voltage adjustment and routine use of prospective electrocardiographic gating with either dose modulation or step-and-shoot acquisition. Data on radiation exposure were collected retrospectively and compared by nonparametric testing. Some hospitals failed to routinely record radiation exposure data; only 2 facilities had data available from both before and after the intervention for direct comparison. Data were acquired from 124 subjects, 41 from the standard of care group and 83 scanned under the new protocol. In hospital A, radiation was significantly reduced by 61% from 20.5 ± 4.6 millisieverts (mSv) to 7.9 ± 4.8 mSv (P < 0.001). Within the new protocol group for hospital A, radiation was lower with step-and-shoot (4.0 ± 1.5 mSv) as compared to dose modulation (10.2 ± 4.2 mSv, P < 0.001). In hospital B, which already employed step-and-shoot acquisition, radiation dose was reduced 16% from 9.3 ± 3.0 mSv to 7.9 ± 2.2 mSv (P < 0.017) by applying body mass index-based tube voltage adjustment alone. In conclusion, a minimal investment in institutional resources can result in a reduction in radiation exposure from CTCA, even in a community-based, multihospital setting. Some facilities do not routinely record radiation exposure data.

Recent developments with lipoprotein-associated phospholipase A2 inhibitors

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) is a calcium-independent phospholipase A(2) enzyme secreted by leukocytes and associated with circulating low-density lipoprotein and macrophages in atherosclerotic plaques. Until recently, the biological role of Lp-PLA(2) in atherosclerosis was controversial, but now the preponderance of evidence demonstrates a proatherogenic role of this enzyme. Lp-PLA(2) generates two proinflammatory mediators, lysophosphatidylcholine and oxidized nonesterified fatty acids, which play a major role in the development of atherosclerotic lesions and formation of a necrotic core, leading to more vulnerable plaques. These findings have opened the door to a potential novel therapeutic target, selective inhibition of Lp-LPA(2). Recently, both animal models and human studies have shown that selective inhibition of Lp-PLA(2) reduces plasma Lp-PLA(2) activity, plaque area, and necrotic core area. This article reviews the most recent developments with Lp-PLA(2) inhibitors.

Pneumothorax Secondary to Acupuncture Therapy

A 27-year-old medical student seeking acupuncture therapy for a right levator scapular muscle spasm developed acute dyspnea, chest pain, and nonproductive cough within minutes following the treatment. The patient was later diagnosed with a 30% pneumothorax of the right lung. Pneumothorax is a well-known adverse effect of medical procedures such as central line placement, thoracocentesis and transbronchial lung biopsy. This case illustrates another iatrogenic cause of pneumothorax--acupuncture-induced pneumothorax. A review of the literature since 1985 reveals nine case reports of acupuncture-induced pneumothorax.