Friday, October 31, 2014

Is Appropriate Use Similar for Cardiology and Non-Cardiology Providers?

Utilization patterns of single-photon emission cardiac tomography myocardial perfusion imaging studies in a rural tertiary care setting.
BACKGROUND: Appropriate use criteria (AUC) for single-photon emission computed tomographic myocardial perfusion imaging (SPECT MPI) were revised in 2009 to include 15 new clinical scenarios.

OBJECTIVE: are the appropriate utilization rates of SPECT MPI imaging similar for cardiology and non cardiology providers?

METHODS: all SPECT MPI studies performed for over a 6-month period at our center were reviewed.

RESULTS: 88% of studies were classified as appropriate, 5.5% as inappropriate,  and 7% as uncertain. The ordering provider specialty did not show any relation with appropriateness of the test (P = 0.46).

CONCLUSIONS: A great majority of MPI studies are performed for appropriate indications regardless of ordering provider specialty.

Clin Cardiol. 2014 Feb;37(2):67-72

Monday, October 20, 2014

Ranolazine and SPECT Myocardial Perfusion Scans

BACKGROUND: Patients with angina relieved by ranolazine (RAN) and a normal SPECT myocardial perfusion scan present a dilemma. Should patients with angina relieved by RAN but a normal SPECT undergo angiography?

METHODS: a chart review was performed. Angiography was done on all the patients with complete angina relief taking RAN, as well as nonresponders whose anginal etiology could not be explained. Stenoses were considered flow-restrictive when more than 70% diameter stenosis is observed by quantitative angiography, or when 50 to 70%, fractional flow reserve (FFR) measured ≤0.80.

RESULTS: RAN relieved angina in 36 of 54 (67%) patients. For 25 of these 36 patients had stenoses ≥50% with 15 (60%) having 1 vessel disease; 9 (36%) having multivessel disease; and 1 (4%) having left main disease. 18 of the 25 (72%) patients had stenoses considered to be flow restrictive. Eight RAN non-responders with no explanation for angina had no obstructive disease on angiography.

CONCLUSION: angina relief by ranolazine helps identify an increased risk of flow-restrictive stenosis in patients with a negative SPECT myocardial perfusion scan. Patients with angina relief by ranolazine are likely to benefit from angiography.

COMMENT: SPECT and angiography do not represent the same thing. SPECT images physiology, and angiography images anatomy. While often the two agree, frequently obstructive disease is not associated with ischemia (e.g. good collateralization) and ischemic disease is not associated with obstruction (e.g. coronary artery spasm). Ranolazine is a partial fatty acid oxidation inhibitor.

Int J Angiol. 2014 Sep;23(3):165-70

Thursday, October 16, 2014

Can Low Grade Radiation Protect Against Cancer?

Surprising Research Finds Beneficial Effects of Low Level Radiation Exposure

Cancer is a heterogeneous disease characterized by uncontrolled cellular growth and multiplication. There are several risk factors associated with cancer, including smoking, inactivity, and a poor diet. However, the role of radiation exposure as a risk factor is unclear. We do know that sudden high doses of radiation, such as that experienced by people exposed to the atomic bomb blasts in Hiroshima and Nagasaki, increases cancer risk. But does all radiation increase the risk of cancer? Surprising evidence suggests that the opposite occurs, that low levels of radiation may actually protect against cancer by a process called radiation hormesis .
The best evidence for a beneficial effect of low level radiation comes from Asia. In Taiwan, approximately 25 years ago, recycled steel was accidentally contaminated with radioactive cobalt-60. This steel was used to build more than 180 buildings, and approximately 10,000 people occupied this buildings for about 10 to 20 years. The mean dose to the residents was approximately 13 mSv per year and the maximum dose was 160 mSv per year. For comparison purposes, the occupational limit for radiation workers in the U.S. is 50 mSv per year. The International Atomic Energy Agency sets the occupational limit at 20 mSv per year.
This unique research, made possible due to the accidental contamination of steel used to make apartment buildings, found that estimates of radiation risk from the International Commission on Radiological Protection were completely wrong. Compared to residents of nearby apartment buildings, that did not contain the radioactive cobalt-50 contamination, the people exposed to low level radiation had greatly reduced cancer deaths and congenital malformations. The cancer death rate among those exposed to low level radiation was only 3% of the rate of the general public. Put another way, the general public was more than 30 times more likely to die of cancer than the people living in the apartment buildings that exposed them to low level radiation over many years. Furthermore, the congenital malformation rate of the radiation exposed residents was 6.5% of the rate of the general public. The general public was more than 15 times more likely to have a child with congenital malformations compared to the radiation exposed residents.
This is strong evidence that a low level of radiation exposure has a beneficial health effect in terms of cancer and congenital malformations. Furthermore, this research is from real world data, not conjecture or theoretical mathematical models.
Based upon this promising research, and similar findings from other epidemiologic studies, some scientists have proposed that further human experiments be carried out, perhaps in nursing homes. Of course, such research would require full consent, Institutional Review Board oversight, and full disclosure to all individuals involved. But if death from cancer can be reduced by a factor of 30, certainly more research into this possibility is needed.
Current radiation hysteria and the linear no-threshold hypothesis do not appear to be based upon valid, scientific evidence. It is time to move out of the dark ages when it comes to radiation, and insist that policy decisions be based upon real world evidence.
REFERENCE: Chen WL et al. Is chronic radiation an effective prophylaxis against cancer? J Amer Phys Surg 2004;9(1):6-10.

The PET/CT Scanner I helped install for Johns Hopkins International

Published by Tom Heston MD 3/24/2012
Tom Heston MD is a Johns Hopkins trained physician who practices clinical medicine in the Pacific Northwest.