Noninvasive cardiac imaging experienced a rapid growth in the 1990s through the mid-2000s, and much of this was due to the rapid increase in nuclear myocardial perfusion imaging (MPI). Use of MPI, however, has recently declined. In a research letter published in JAMA, Edward J. McNulty, MD, and colleagues reported the results from an investigation of temporal trends in MPI use in a large, community-based population—and what factors led to the drop in MPI compared to other imaging modalities. Patient-level data were collected for MPIs performed from 2000-2011 in patients aged 30-65 years in the clinical database of Kaiser Permanente Northern California.

The investigators calculated age- and sex-adjusted annual rates of MPI tests per 100,000 person-years (with 2011 as the reference year). Overall, MPI was used in 302,506 community members during 23.2 million person-years of follow-up at 19 facilities. In the first half of the study period, MPI use increased by 41% (95% CI 39-44%; p < 0.001), but was followed by a reduction in 2006 that continued through 2011, when MPI use declined by 51% (TABLE). The likelihood of a patient receiving an MPI at this point in the study period was cut in half.

So, what factors played into this decline? McNulty et al. tested for the potential substitution of other imaging modalities for MPI and found that stress echocardiography use was unchanged (189 tests per 100,000 person-years in 2007 vs. 182 in 2011), and cardiac computed tomography use increased (37 tests per 100,000 person-years in 2007 vs. 73 in 2011). The authors noted that this increase could have accounted for 5% of the observed decline in overall MPI use, but the declines in MPI could not be completely explained by increasing use of alternative modalities.

"Although the abrupt nature of the decline suggests changing physician behavior played a major role, incident coronary disease, as assessed by MI, also declined," Dr. McNulty and colleagues concluded. "Nevertheless, the substantial reduction in MPI use demonstrates the ability to reduce testing on a large scale with anticipated reductions in health care costs."

McNulty EJ, Hung YY, Almers LM, et al. JAMA. 2014;311:1248-9.

TABLE. Myocardial Perfusion Imaging Trends

	Number of MPI		Change in Rate, % (95% CI)
	2000 (Baseline)	2011	2000-2006	2006-2011
Total MPI	19,326	17,323	41 (39 to 44)	-51 (50 to 52)
Sex
Female	8,998	8,591	47 (42 to 52)	-51 (49 to 52)
Male	10,328	8,732	36 (32 to 41)	-52 (50 to 53)
Clinical Setting
Inpatient	4,459	6,341	58 (53 to 64)	-31 (29 to 33)
Outpatient	14,867	10,982	36 (33 to 39)	-58 (57 to 59)
Received PCI or CABG
Yes	4,207	4,113	76 (70 to 82)	-58 (56 to 59)
No	10,660	6,869	20 (17 to 23)	-58 (57 to 59)

Keywords: Myocardial Perfusion Imaging, Follow-Up Studies, Tomography, X-Ray Computed, Echocardiography, Stress, Coronary Disease, Health Care Costs, Secretory Leukocyte Peptidase Inhibitor

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