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Negative CT scan to rule out PE equal to angiography

Clinical question Can clinicians rely on a negative computed tomography scan to rule out suspected pulmonary embolism?

Bottom line A negative computed tomography (CT) scan is as accurate as pulmonary angiography in ruling out suspected pulmonary embolism (PE). Clinicians should strongly consider using clinical decision rules to accurately assess the pretest probability of PE in a individual patient, and then interpret diagnostic tests in light of this probability. For example, negative CT in a low-risk patient rules out PE, while negative CT in a high-risk patient may require further confirmation. (Level of evidence = 2a)

Quiroz R, Kucher N, Zou KH, et al. Clinical validity of a negative computed tomography scan in patients with suspected pulmonary embolism. A systematic review. JAMA. 2005;293:2012-2017.

Study design Systematic review

Setting Various (meta-analysis)

Synopsis Previous studies question the value of using CT alone to rule out suspected PE. These investigators thoroughly searched multiple databases – including MEDLINE, the Cochrane Registry of Controlled Trials, and Science Citation Index – and relevant journals for English language articles meeting selection criteria. Included studies used contrast-enhanced CT as the initial triage test to rule out the diagnosis of acute PE, had an appropriate clinical follow-up of at least 3 months, and a prospective design. The gold standard to establish the validity of testing to rule out PE was the rate of subsequent venous thromboembolic events (VTE) after anticoagulation therapy was withheld. Two reviewers independently abstracted data, and a third party arbitrated discrepancies. From the initial search that found 22 studies, 15 studies evaluating a total of 3,500 patients met the minimal inclusion criteria. Seven of these 15 met the criteria for level 1 diagnostic studies. Three different CT modalities were evaluated, including single-slice CT, multidetector-row (helical) CT, and electron-beam CT. Patient follow-up ranged from 3 months to 12 months. The overall negative likelihood ratio of a VTE after a negative CT scan for PE was 0.07 (95% CI, 0.05-0.11). There was no significant difference in the risk of a subsequent VTE based on the type of CT modality used. Compared with studies that used chest CT only, the risk of subsequent VTEs in studies using additional imaging tests prior to chest CT was not significantly reduced. The reported negative likelihood ratio in this analysis compares favorably with that reported for pulmonary angiography (Henry JW, Relyea B, Stein PD. Chest. 1995;107:1375-1378). A formal analysis found no evidence for significant publication bias, but there was some minimal heterogeneity among the results of the various trials.

High resting heart rate a risk factor for sudden cardiac death

Clinical question Is a high resting heart rate associated with an increased risk of sudden cardiac death?

Bottom line This study showed that a higher resting heart rate was associated with an increased risk of sudden death. We do not know whether any exercise or pharmacologic intervention in patients with an elevated heart rate would modify their risk. (Level of evidence = 1b)

Jouven X, Empana JP, Schwartz PJ, et al. Heart-rate profile during exercise as a predictor of sudden death. N Engl J Med. 2005;352:1951-1958.

Study design Cohort (prospective)

Setting Population-based

Synopsis If you were a male Parisian civil servant in the late 1960s, there is a good chance that you had a screening cardiac stress test. Those with a resting systolic BP greater than 180 mm Hg, an abnormal resting electrocardiogram, ischemic changes, or who did not achieve 80% of their predicted maximum heart rate were excluded from this analysis, as were those who were lost to follow-up (4.6%). This left 5,713 men, of whom 81 experienced a sudden cardiac death and 129 a nonsudden death from myocardial infarction. The researchers found a direct correlation between increasing resting heart rate and the risk of sudden cardiac death (higher heart rate being worse) and an inverse correlation between sudden death and the difference between the maximum heart rate during exercise and the resting heart rate (lower difference between the two being worse). After adjusting for age, tobacco use, physical activity, cholesterol level, family history, and diabetes, patients with a resting heart rate faster than 75 beats per minute were 3.5 times more likely to experience sudden cardiac death than those with a slow heart rate. The relative risk for all-cause mortality was 1.9. There was no significant relationship between heart rate and nonsudden death from MI.

Acupuncture effective for chronic back pain

Clinical question Is acupuncture effective in treating acute or chronic low back pain?

Bottom line Acupuncture is an effective treatment for decreasing pain in patients with chronic low back pain. It does not seem to be a placebo effect; acupuncture produces a significantly greater effect on pain than sham acupuncture. There is not enough research to allow a conclusion for the treatment of acute low back pain. (Level of evidence = 1a)

Manheimer E, White A, Berman B, et al. Meta-analysis: Acupuncture for low back pain. Ann Intern Med. 2005;142:651-663.

Study design Meta-analysis (randomized controlled trials)

Setting Various (meta-analysis)

Synopsis Acupuncture is becoming more common in Western medicine, with many traditionally trained physicians crosstrained in its use. This meta-analysis assembled 22 randomized controlled trials comparing acupuncture with no treatment, sham acupuncture, or another active treatment such as massage or analgesics in the treatment of chronic low back pain. Sham acupuncture is used to convince patients they are receiving acupuncture and consists of inserting acupuncture needles either superficially or at inappropriate sites, or by using the acupuncture needle tube or other blunt device to provide pressure without actual penetration. The studies (in any language) were identified by searching seven databases, contacting experts, handsearching a Japanese acupuncture journal, and using previous review articles. Two authors independently selected the studies and abstracted the data. Results of sham-controlled studies were homogeneous. One study of the five studies that compared acupuncture with no additional therapy produced heterogeneous results favoring no treatment as compared with acupuncture. Publication bias could not be assessed.

For patients with chronic low back pain, lasting at least 3 months, acupuncture was more effective than sham acupuncture, sham transcutaneous nerve stimulation (TENS), and no treatment for short-term pain relief. It was not significantly better or worse than massage, medication therapy, or actual TENS treatment, and was significantly less effective than spinal manipulation. It provided long-term pain relief as compared with sham TENS or no treatment but was not different from sham acupuncture or active TENS. There is not enough data on the effectiveness of acupuncture for acute back pain to provide a conclusion. Three studies evaluated the use of acupuncture in the treatment of antenatal low back pain; all three studies found a benefit, though their results could not be combined.