Appropriate Use of Nuclear Cardiology

Chapter 25 Appropriate Use of Nuclear Cardiology

Spending on health care in the United States has been increasing at an alarming rate. Over the past 40 years, the annual increase in federal health care spending has outpaced the annual growth of the gross domestic product (GDP) by an average of 2.5%.¹ Currently, U.S. health care spending exceeds $2 trillion and accounts for 16% of the GDP.² The Congressional Budget Office projects that if current trends were to persist over the next 40 years, federal spending on Medicare and Medicaid (ignoring state spending on Medicaid) would approach 20% of the GDP (Fig. 25-1). To appreciate the significance of this projection, it is important to realize that total federal revenue over the past 60 years has ranged between 17.0% and 20.9% of the GDP and has never in the history of the United States exceeded 20.9%.³ In other words, the projected federal spending on Medicare and Medicaid alone by the midpoint of this century would equal (as a percentage of the GDP) what has historically been spent on all components of the federal budget (social security, defense, education, interest on the national debt, agriculture, etc.).

Figure 25-1 Federal spending on Medicaid and Medicare as a percent of GDP. Over the past 60 years, total federal revenue (horizontal band) has always been between 17% and 21% of the GDP. By 2040, spending on Medicaid and Medicare alone is projected to approximate 17% of the GDP.

(Reprinted from Orszag PR: Health care and the budget: Issues and challenges for reform. CBO Testimony before the Committee on the Budget, United States Senate, 2007.)

Spending on cardiovascular diseases accounts for a substantial proportion of total health care spending. In 2007, the estimated direct and indirect costs for cardiovascular diseases were nearly $432 billion.⁴ The rate of growth in cardiac imaging services has recently been especially steep. Stress imaging, which as defined by Medicare incorporates both stress single-photon emission computed tomography (SPECT) and stress echocardiography, grew at a rate of 6% per year between 1993 and 2001.⁵ This rate of growth for stress imaging far exceeded the rate of growth in acute myocardial infarction, cardiac catheterizations, or coronary artery revascularization procedures during this time period (Fig. 25-2). Published data further demonstrate that the use of stress imaging is highly heterogenous across the country, with rates of imaging varying by more than 10-fold between different geographic regions (Fig. 25-3).⁶

Figure 25-2 Growth in Medicare stress imaging (which incorporates both SPECT and stress echocardiography) compared to cardiac catheterizations, revascularization procedures, and acute myocardial infarction between the years 1993 to 2001. The rate of growth of stress imaging far exceeded that of the other procedures or occurrence of myocardial infarction.

(Reprinted from Lucas FL, DeLorenzo MA, Siewers AE, et al: Temporal trends in the utilization of diagnostic testing and treatments for cardiovascular disease in the United State, Circulation 113:374–379, 2006.)

Figure 25-3 Dartmouth health care atlas map illustrating rates of stress imaging (both SPECT and stress echocardiography) studies in 1996 by Medicare referral regions compared to the national average. Regions in the darkest colors, concentrated primarily in selected locations in the Northeast, Southeast, Midwest, and Southwest, had rates far above the national average.

(Reprinted from Wennberg JE, Birkmeyer JD, Birkmeyer NJO, et al: The Dartmouth Atlas of Cardiovascular Health Care. Chicago: American Hospital Association Press, 1999.)

In response to these concerns about the use of cardiovascular imaging, the American College of Cardiology Foundation (ACCF) initiated a process to address the appropriateness of different cardiovascular imaging procedures.⁷ Examining the appropriateness of medical resource use is not a novel concept.⁸^–¹⁰ The American College of Radiology (ACR) published appropriateness criteria for radiologic imaging procedures in 1995.¹¹ The ACR criteria address a variety of imaging procedures across multiple medical and surgical disciplines. They have not been widely applied to the practice of clinical cardiology. The ACCF appropriateness criteria focus on single cardiovascular imaging procedures. In October 2005 the ACCF, in collaboration with the American Society of Nuclear Cardiology (ASNC), published the first set of appropriateness criteria, which addressed SPECT myocardial perfusion imaging (SPECT MPI).¹² Since then, appropriateness criteria have been published for cardiac computed tomography and cardiac magnetic resonance imaging,¹³ transthoracic and transesophageal echocardiography,¹⁴ stress echocardiography,¹⁵ and coronary revascularization.¹⁶

The approach the ACCF has followed to examine the appropriateness of a cardiovascular imaging modality is based on a method originally developed by the RAND Corporation, in collaboration with researchers from the University of California, Los Angeles (UCLA), to examine the appropriateness of medical and surgical procedures.¹⁷ Although the ACCF methodology is based on the RAND/UCLA approach, it is important to note that the RAND/UCLA method focuses on the therapeutic benefit of invasive procedures, whereas cardiovascular imaging has different goals. Another major difference relates to the number of clinical scenarios considered. The RAND/UCLA document addresses literally hundreds of clinical scenarios. The ACCF approach limits the number of situations to fewer, more broadly defined clinical scenarios where imaging is most commonly applied. The ACCF method follows the precedent set by the ACR and uses the modified Delphi method to develop appropriateness criteria. With this approach, members of an expert panel assign ratings for imaging to various clinical indications, initially without any interaction with other panel members. The panel then meets to discuss the assigned ratings, and members again assign ratings after this panel interaction. The ACCF approach differs from the ACR approach by not trying to achieve consensus of panel members and by using fewer rounds of ratings.⁷

The definition of an appropriate imaging study selected by the ACCF is:⁷

It is important to note that the “negative consequences” listed in this formal definition do not directly mention cost of the procedure. However, the ACCF methodology document does acknowledge the importance of cost: “Therefore, to identify the true risks of imaging, both inherent risks and downstream effects, including costs, must be considered. As such, if the imaging study provides little incremental information for an indication over standard clinical judgment and care, then cost considerations should contribute to deeming the procedure inappropriate.”⁷

For each imaging modality being rated for appropriateness, the ACCF method follows 4 steps:

1. Develop list of specific clinical indications

2. Expert panel ratings

3. Expert panel meeting followed by re-ratings

4. Tabulation of appropriateness recommendations

The panelists assign a rating for each clinical indication using a 9-point scoring system. Following the second round of voting by panel members, scores are categorized as follows:

Median score 7 to 9: Appropriate test for that specific indication.

Median score 4 to 6: Uncertain or possibly appropriate test for that specific indication.

Median score 1 to 3: Inappropriate test for that indication.

It is important to distinguish between appropriateness criteria and clinical guidelines. ACCF/American Heart Association (AHA) guidelines are based on comprehensive reviews of the medical literature (evidence-based) and employ a level-of-evidence rating scheme to assign indications to diagnostic procedures and therapies. Conversely, the appropriateness criteria are based on consideration of benefit versus risk of performing the imaging modality. Panel members are encouraged to consider the published literature when assigning a rating for a given indication, but there is no requirement that the rating be based on the literature. The emphasis is on a less formal approach of whether it is “reasonable” to consider performing the imaging study.⁷

The technical panel for SPECT MPI appropriateness criteria was composed of 12 physicians, 58% of whom were specialists in nuclear cardiology. This panel rated 52 clinical indications for SPECT imaging. Most (49) of these indications addressed stress SPECT for detection or risk assessment of coronary artery disease, one indication addressed assessment of viability, and two indications addressed evaluation of ventricular function (Tables 25-1 through 25-9).¹² Of the 52 indications, 27 were rated appropriate, 12 uncertain, and 13 inappropriate.

Table 25-1 Detection of Coronary Artery Disease: Symptomatic

Indication		Appropriateness Criteria (Median Score)
Evaluation of Chest Pain Syndrome
1.	• Low pretest probability of CAD • ECG interpretable AND able to exercise	I (2.0)
2.	• Low pretest probability of CAD • ECG uninterpretable OR unable to exercise	U* (6.5)
3.	• Intermediate pretest probability of CAD • ECG interpretable AND able to exercise	A (7.0)
4.	• Intermediate pretest probability of CAD • ECG uninterpretable OR unable to exercise	A (9.0)
5.	• High pretest probability of CAD • ECG interpretable AND able to exercise	A (8.0)
6.	• High pretest probability of CAD • ECG uninterpretable OR unable to exercise	A (9.0)
Acute Chest Pain (in Reference to Rest Perfusion Imaging)
7.	• Intermediate pretest probability of CAD • ECG—no ST elevation AND initial cardiac enzymes negative	A (9.0)
8.	• High pretest probability of CAD • ECG—ST elevation	I (1.0)
New-Onset/Diagnosed Heart Failure With Chest Pain Syndrome
9.	• Intermediate pretest probability of CAD	A (8.0)

A, appropriate; I, inappropriate; U, uncertain.

* Median scores of 3.5 and 6.5 were rounded to the middle (U).

Table 25-2 Detection of Coronary Artery Disease: Asymptomatic (Without Chest Pain Syndrome)

Indication		Appropriateness Criteria (Median Score)
Asymptomatic
10.	• Low CAD risk (Framingham risk criteria)	I (1.0)
11.	• Moderate CAD risk (Framingham)	U (5.5)
New-Onset or Diagnosed Heart Failure or LV Systolic Dysfunction Without Chest Pain Syndrome
12.	• Moderate CAD risk (Framingham) • No prior CAD evaluation AND no planned cardiac catheterization	A (7.5)
Valvular Heart Disease Without Chest Pain Syndrome
13.	• Moderate CAD risk (Framingham) • To help guide decision for invasive studies	U (5.5)
New-Onset Atrial Fibrillation
14.	• Low CAD risk (Framingham) • Part of the evaluation	U*(3.5)
15.	• High CAD risk (Framingham) • Part of the evaluation	A (8.0)
Ventricular Tachycardia
16.	• Moderate to high CAD risk (Framingham)	A (9.0)

A, appropriate; I, inappropriate; U, uncertain.

* Median scores of 3.5 and 6.5 are rounded to the middle (U).

Table 25-3 Risk Assessment: General and Specific Patient Populations

Indication		Appropriateness Criteria (Median Score)
Asymptomatic
17.	• Low CAD risk (Framingham)	I (1.0)
18.	• Moderate CAD risk (Framingham)	U (4.0)
19.	• Moderate to high CAD risk (Framingham) • High-risk occupation (e.g., airline pilot)	A (8.0)
20.	• High CAD risk (Framingham)	A (7.5)