Approaches to Revising the Cardiovascular Listings
ISSUES IN REVISING THE LISTINGS
This report primarily addresses the specific cardiovascular listings and several cardiovascular conditions for which listings might be useful (see Chapters 5 through 14). This chapter discusses issues common to all or most of the cardiovascular listings and the approach the committee took to addressing them. These include the criteria for evaluating listings, the trade-off between sensitivity and specificity inherent in designing a screening tool such as the listings, the limited predictive capacity of most clinical factors, the safety of exercise tests, and the impact of comorbidities (discussed in more detail in Chapter 15).
Attributes of Effective Listings
Ideally, listings have the following attributes:
Up to date with advances in diagnosis and treatment and with changes in the nature of work;
Useful (SSA, 2005).
Several of these attributes were emphasized in the Social Security Administration’s (SSA’s) presentation to this committee at its first meeting (SSA, 2009). The committee was urged to recommend revisions that would
make the cardiovascular listings more inclusive; more up to date regarding the latest knowledge, science, and technology; and more user-friendly, that is, as objective as possible and requiring the minimum number of criteria to be fulfilled to meet a listing.
The committee kept these criteria in mind throughout its discussions, while recognizing the inherent trade-offs among them. The recommendations incorporate the latest knowledge and technology based on current clinical guidelines and scientific literature, but they would only require tests and other procedures that are widely available in medical settings throughout the country. If a claimant has had more sophisticated, cutting-edge diagnostic tests that are only available in leading medical centers, the results should be used, but are not required. In addition, some techniques required by clinical guidelines for a definitive diagnosis (e.g., right heart catheterization to establish pulmonary hypertension) are considered to be too risky for SSA to require claimants to have the procedure if they have not already had it.
Objective criteria may be easier to use and lead to more consistent decisions, but they do not necessarily lead to more correct decisions. The generally limited ability of objective clinical tests to predict functional capacity or work disability is discussed below.
The committee did not try to consider the changing nature of work, other than to be aware of the long-term trend away from physically demanding jobs to less strenuous, but more cognitively demanding, jobs. The committee also could not determine whether the current cardiovascular listings or proposed revisions are correct in terms of validity, that is, the extent to which they allow all claimants who are truly unable to engage in any gainful employment—and only those claimants. This would require further research.
The general approach taken by the committee to revising the cardiovascular listings is shown in an algorithm outlined in Box 4-1. The algorithm was designed to arrive at the listings-level criteria that were the most objective and easiest to administer while maintaining a reasonable degree of accuracy.
Few diagnoses are sufficient by themselves to meet the Listings. Examples in other body systems include amyotrophic lateral sclerosis and amputation of both hands. Most of the compassionate allowance conditions are based on diagnosis, such as aggressive, incurable cancers and certain rare diseases that are invariably fatal; none of them is a cardiovascular condition.
The committee is not recommending any diagnoses as sufficient to meet a cardiovascular listing, except the current listing for heart transplantation.
Committee’s Approach to Revising the Listings
It automatically allows benefits for a 12-month period after the procedure, which the committee would not recommend revising.
Diagnosis Plus a Specific Degree of Medical Severity
A number of listings require evidence of a certain degree of medical severity according to a specified test or examination, including one cardiovascular listing. For example, the current listing for peripheral artery disease (PAD) is met with a resting ankle-brachial index (ABI) of less than 0.50 or certain toe pressure values. Adjudicators find such listings to be objective and easy to apply, but the problem with most medical severity measures is their lack of sensitivity (i.e., their inability to identify many true positives), especially if they are set at a point of high specificity to prevent false positives. This stems from the limited capacity of most severity measures to predict degree of functional limitation or vocational capacity and is discussed more fully below.
The committee could have recommended clinical criteria so severe that anyone meeting them would almost certainly be unable to work. For example, the PAD listing could specify an ABI of less than 0.40, when critical leg ischemia requiring emergency intervention to avoid amputation becomes
likely. The problem with this approach is that relatively few claimants who are truly unable to work would meet the criteria, which would undermine the purpose of the Listings. Their purpose is to allow claimants to meet the criteria quickly if they would be highly likely to do so after undergoing the usual in-depth, time-consuming evaluation.
The committee agreed that it would be appropriate for certain conditions to meet a listing based on diagnosis and severity alone. These include:
Symptomatic severe aortic stenosis that meets certain anatomical impairment criteria determined by echocardiogram or heart catheterization because it is likely to be fatal in a short time unless treated successfully by surgery (see Recommendation 12-1).
Symptomatic chronic venous insufficiency (CVI) with severe trophic skin changes or persistent venous ulcers (see Recommendation 9-1).
In several instances, the committee recommends that claimants should meet a listing on the basis of a certain degree of severity alone or, for a somewhat lower degree of severity, if they are severely functionally limited. Adding a second basis for meeting a listing that requires less impairment severity—if the claimant can demonstrate a marked limitation of capacity to function due to that impairment or impairments—increases the sensitivity of the Listings, that is, identifies more claimants who should be allowed. Examples include:
Systolic heart failure with a left ventricular ejection fraction of 20 percent or less, because this severity would preclude gainful employment for nearly everyone, or with a left ventricular ejection fraction between 20 and 30 percent in conjunction with marked functional limitations (see Recommendations 5-3 and 5-1, respectively).
Pulmonary hypertension with a mean pulmonary artery pressure of 40 mm Hg or higher, or with a mean pulmonary artery pressure between 25 and 40 mm Hg in conjunction with marked functional limitations (see Recommendations 11-1A and 11-1B, respectively).
Diagnosis Plus a Specific Degree of Medical Severity Plus a Specific Degree of Whole-Person Functional Limitation
In many conditions, even a substantial degree of impairment of an organ or body system does not always rule out capacity to work. In most cases, at a given degree of severity (e.g., ejection fraction less than 30 percent), most people will not be able to work, although some will have that
capacity. Therefore, additional information is needed to establish whether a claimant is unable to work (i.e., has functional limitations considered to be tantamount to inability to work). Most of the current cardiovascular listings are structured this way. For example, given a diagnosis of systolic heart failure and an ejection factor of 30 percent or less, the current listing is not met unless the claimant is unable to perform 5 metabolic equivalents of task (METs) on an exercise test, or has had three or more episodes of acute heart failure, or has persistent symptoms “which very seriously limit the ability to independently initiate, sustain, or complete activities of daily living.”
After reviewing evidence regarding the relationship of impairment measures (e.g., the ABI, ejection fraction, degree of left main artery stenosis, pulmonary artery pressure, valvular regurgitation volume to functional capacity), the committee concluded that such measures generally should be considered necessary, but not sufficient to meet a listing. Most of the recommendations for listing-level criteria therefore take the form of (1) an anatomical abnormality of a certain severity, and (2) a certain degree of functional limitation. This is the approach taken to the listing criteria for heart failure, ischemic heart disease (unless the ejection fraction is 20 percent or less), PAD, and CVI.
Diagnosis Plus a Specific Degree of Functional Limitation
In some cases, evidence of very serious functional limitations is all that is needed in addition to a diagnosis. Other than in many of the mental listings, this is not common in the adult Listings. It is always an option in the childhood Listings, where claimants may functionally equal the Listings. The committee concluded that this approach would not be suitable for any of the adult cardiovascular conditions.
The criteria in the cardiovascular listings are all measures obtained from using some kind of instrument or protocol. Examples of measures include left ventricular diameter, left ventricular ejection fraction, heart wall thickness, peak VO2 and other cardiopulmonary exercise (CPX) test readings, New York Heart Association functional classification, Canadian Cardiovascular Society (CCS) angina classification, ST-segment depression and other electrocardiogram (ECG) readings, degree of artery stenosis, ABI, arterial O2 saturation, mean pulmonary artery pressure, METs, amount of heart valve regurgitation, size and rate of growth of an aortic aneurysm, amount of reflux in a leg vein, and activities of daily living (ADLs). These measures are not perfect for a variety of reasons. The reading may not
be representative if the process being measured is variable, such as blood pressure or heart rate. The image may be complex to read, such as an echocardiogram of a ventricle or the aorta. The measure may be an indirect estimate, such as METs from a treadmill test done without measuring respiratory gas exchange. The test may be of low quality because the equipment was not well maintained or the tester was not adequately trained and certified to conduct it.
Some of the measures are obtained objectively, for example, blood pressure readings. Others are subjective, based on patient self-report, such as CCS angina class or ADL score. The main issue, however, is the extent to which a given test or protocol measures the phenomenon of interest. The ABI, for example, is objective, based on the ratio of two blood pressure readings. It is a validated test of peripheral artery disease, because, on average, individuals with an ABI of 0.90 have been shown by simultaneous angiography to have a 50 percent blockage of a major leg artery. However, it is not a strong measure of walking or of stair climbing capacity (which are themselves proxy measures of the phenomenon of interest, namely, degree of disability). An ABI of 0.50 is positively but weakly associated with distance walked in 6 minutes. ADL scores, on the other hand, while based on patient self-report, are a significant predictor of entry into a nursing home (Gaugler et al., 2007), use of hospital services and physician services, and mortality (Dunlop et al., 1999).
In the context of measuring inability to engage in any gainful activity—the definition of someone who should be allowed at Step 3—the appropriate way to evaluate a listing is as a screening tool or diagnostic test. The purpose of the listing is to correctly identify individuals whose medical condition or conditions either meet or equal that listing or do not meet or equal that listing. The former are true positives who should be allowed. The latter are true negatives who should be sent on to Step 4 and, if necessary, Step 5 (they may still be allowed if they meet the inability to perform any substantial gainful activity, the standard at Step 5). Individuals not identified and allowed at Step 3 are false negatives and constitute a lost opportunity to save time and resources. Allowed individuals may be false positives, who obtain benefits they are not entitled to. The appropriate metrics in this situation are sensitivity, specificity, and related measures of test accuracy. These are discussed in the next section in the context of assessing the limitations of the listings.
Limitations of the Listings as a Screening Tool
The Listings are used to determine if a claimant can or cannot engage in any gainful activity, that is, perform any work for pay. In fact, the work capacity of a population of claimants with a given impairment will vary
from no work to high-work capacity. There will always be claimants with conditions that are difficult to classify as totally incapacitating (therefore meeting or equaling the Listings) as opposed to almost totally incapacitating (therefore not meeting or equaling the Listings). This uncertainty results in classification errors, that is, false negatives (claimants who are denied, but should be allowed) and false positives (claimants who are allowed, but should have been denied). As with other diagnostic screening tools, restricting the criteria would reduce false positives (increase specificity) but also would increase false negatives (reduce sensitivity). Relaxing the criteria to reduce false negatives (thus allowing true positives to be allowed quickly) would also increase the number of false positives.
As the administrator of a government benefit program, SSA wants to keep the false-positive rate very low, but at the same time wants the Listings to be as sensitive as possible. Higher sensitivity would quickly allow a greater percentage of those who are truly unable to work to qualify for benefits, which is the purpose of having the Listings. Therefore, in formulating recommendations to improve them, the committee kept in mind the trade-off between sensitivity and specificity and SSA’s preference for high specificity. Generally, given the variable relationship between medical impairment measures and functional capacity—and the desire to increase sensitivity without unduly lowering specificity—most of the recommendations require both (1) an anatomical abnormality of a certain severity and (2) a certain degree of functional limitation, as discussed in the previous section. The false negatives (i.e., claimants who are truly unable to work but are not allowed at Step 3) resulting from the relative lack of sensitivity are not denied. They proceed through the remaining steps of the decision process, which involve an in-depth medical and vocational evaluation, and if they are unable to work, they should be allowed at Step 5.
Limitations on the Predictive Ability of Clinical Factors
The limited ability of clinical factors to predict the degree of functional capacity of an individual with an impairment makes it more challenging to increase the sensitivity of the Listings and to maintain high specificity at the same time. For example, most people with a left ventricular ejection fraction of 30 percent or less will not be able to get to and from or function in the workplace, but some will have that capacity. Meanwhile, some individuals with an ejection fraction of 40 or even 50 percent will be totally incapacitated. The same is true of using an ABI of less than 0.50 to predict the work capacity of individuals with PAD—some will be able to work.
This variability in functional capacity among people with the same clinical test results increases the uncertainty and, therefore, creates the problem of false negatives and false positives discussed above. In these cir-
cumstances, lowering the ejection fraction to 20 percent or the ABI to 0.40 would ensure specificity, but it would also reduce sensitivity to the point that most true positives would not meet or equal the Listings and would have to go through the time- and resource-intensive Steps 4 and 5 of the disability decision process. Using an ejection fraction of 50 percent or an ABI of 0.70 would likely allow most of the true positives, but at the same time it would allow many individuals who could work.
In most of the recommendations, therefore, the committee tried to increase sensitivity by requiring objective clinical documentation of severe impairments consistent with incapacity to work in most cases (e.g., ejection fraction of less than 30 percent for heart failure) and evidence of very serious functional limitations, which would serve to screen out false positives.
Functional Assessment Tools
The mainstay of functional capacity testing in cardiovascular medicine is the exercise test conducted on a motorized treadmill or cycle ergometer with ECG and blood pressure monitoring. Exercise tests provide an objective measure of a person’s maximal aerobic capacity and are commonly used to provide diagnostic and prognostic information. The information can also be compared with the aerobic demands of various jobs, usually expressed as METs (Ainsworth et al., 2000). The number of METs an individual can achieve can be estimated from a graded treadmill test with ECG findings or determined directly if the individual’s intake of oxygen and output of carbon dioxide are measured. The latter test, called a CPX test, can also determine how fully the patient is exerting himself or herself by measuring a respiratory exchange ratio to determine a patient’s level of effort (Balady et al., 2010).
Exercise testing is commonly performed for diagnostic and prognostic purposes on individuals with ischemic heart disease, heart failure, valvular heart disease (except for symptomatic aortic stenosis), peripheral artery disease, congenital heart disease, unexplained exertional dyspnea, and children with symptoms on exercise or “before certain athletic, recreational, or vocational activities” (Arena et al., 2007; Paridon et al., 2006). According to several reviews of recent studies, CPX testing is useful in determining functional capacity in patients with pulmonary arterial hypertension and heart failure (Arena et al., 2008, 2010).
Some individuals may not be suitable candidates for an exercise test but can undergo a pharmacologic stress test. A pharmacologic stress test is indicated for patients with severe debilitation or a noncardiovascular impairment that prevents them from achieving a maximal heart rate during an exercise stress test. In a pharmacologic stress test, cardiovascular stress
is induced by a pharmacologic agent and the functional response assessed with echocardiography or other imaging modality, such as radionuclide imaging.
Individuals with leg impairments or other severe debilitation may be good candidates for a timed walk test, such as the distance walked in 6 minutes, although timed walk tests are not considered a substitute for treadmill or ergometry exercise testing in individuals for whom treadmill or ergometry testing are not contraindicated (Arena et al., 2007).
It is well established that a person’s ability to perform specific everyday tasks is predictive of disability outcomes, such as nursing home entry and level of care needed in assisted living facilities. The best known measures are ADLs and instrumental activities of daily living (IADLs). ADLs are basic tasks of daily life, such as feeding oneself, dressing, bathing, using the toilet, and transferring (getting in and out of bed or a chair). IADLs are activities such as housework, preparing meals, shopping, managing money, and using the telephone (NRC, 2009). Tools for assessing capacity to perform ADLs and IADLs have been developed and validated for use in rehabilitation and long-term care settings (Katz, 1963; Katz and Apkom, 1976; Lawton and Brody, 1969; Mahoney et al., 1958).
Maximizing the Use of Exercise Testing
The introductory section of the cardiovascular system listings notes that exercise tolerance tests are widely used to determine functional capacity in patients with ischemic heart disease, heart failure, and peripheral artery disease. It is indicated that SSA might purchase an exercise test if it is needed to determine whether a claimant meets or equals a cardiovascular listing; however, the current cardiovascular listings are based on an overly strict assessment of the risk factors associated with the performance of these tests. In fact, an extensive body of research shows exercise testing to be safe in most cases and much safer than the criteria in the current listings assume (Arena et al., 2007; Balady et al., 2010; Gibbons et al., 2002).1 The committee encourages SSA to revise section 4.00.C.8 to bring it in line with the current understanding of the safety of exercise tests.
Serious complications, such as myocardial infarction (MI), arrhythmia, and death, can occur as a result of exercise testing. The incidence is very low, however. Multiple studies indicate that the risks of a complication that requires hospitalization, MI, or sudden cardiac death during or immediately after an exercise test are less than or equal to 0.2 percent, 0.04 percent,
and 0.01 percent, respectively (Myers et al., 2009, citing ACSM, 2006). Obviously, supervisory physicians should be well trained in the clinical indications for use of exercise testing and in signs and symptoms of serious adverse events to minimize risk to patients. According to American College of Cardiology/American Heart Association guidelines for exercise testing (Gibbons et al., 2002), absolute contraindications for exercise testing are an acute MI within the past 2 days, arrhythmias causing symptoms or hemodynamic compromise, symptomatic and severe aortic stenosis, uncontrolled symptomatic heart failure, acute pulmonary embolus or pulmonary infarction, acute myocarditis or pericarditis, and acute aortic dissection. Relative contraindications are left main coronary stenosis, moderate stenotic valve disease, electrolyte abnormalities, severe systolic hypertension (greater than 200 mm Hg), severe diastolic blood pressure (greater than 110 mm Hg), tachyarrhythmias or bradyarrhythmias, hypertrophic cardiomyopathy and other forms of outflow tract obstruction, mental or physical impairment leading to an inability to exercise adequately, and high-degree atrioventricular block.
Absolute indications for terminating an exercise test include a persistent drop in systolic blood pressure from baseline of more than 10 mm Hg despite an increase in workload (when accompanied by other evidence of ischemia); moderate to severe angina; central nervous system symptoms (e.g., ataxia, dizziness, or near syncope); signs of poor perfusion (e.g., cyanosis or pallor); technical difficulties monitoring the ECG or the systolic blood pressure; sustained ventricular tachycardia; ST elevation greater than or equal to 1 mm in leads without Q waves (other than V1 or aVR); or the subject’s request to stop. Relative indications for stopping include a drop in systolic blood pressure from baseline of more than 10 mm Hg despite an increase in workload (in the absence of other evidence of ischemia); ST or QRS changes such as excessive ST displacement (more than 2 mm of horizontal or down sloping) or marked axis deviation; arrhythmias other than sustained ventricular tachycardia; symptoms such as fatigue, shortness of breath, wheezing, leg cramps, or claudication; bundle-branch block or intraventricular conduction delay that cannot be distinguished from ventricular tachycardia; increasing chest pain; or hypertensive response (systolic blood pressure greater than 250 mm Hg or diastolic blood pressure greater than 115 mm Hg) (Fletcher et al., 2001; Gibbons et al., 2002).
Consideration of the Impact of Comorbidities
An extensive body of literature documents the presence and negative effects of comorbidities such as diabetes, obesity, chronic obstructive pulmonary disease, chronic kidney disease, malignancies, and major depression on the clinical outcomes and functional status of individuals
with cardiovascular disease. The committee carefully considered whether to include factors such as the presence of severe chronic depression in the cardiovascular listings, but decided against it because of the variable effects of comorbidities on individuals. However, the committee assumes that SSA, in applying the cardiovascular listings, will implement its existing policies regarding comorbidities as fully as possible. These policies permit a claimant to equal a listing on a case-by-case basis (see further discussion of this issue in Chapter 15).
This chapter has outlined the committee’s approach to revising the cardiovascular listings. In summary, the committee kept in mind the administrative purpose of the Listings, which is to create a shortcut for the approval of claimants whose impairments are so severe that they would most likely be allowed after going through the more in-depth, but time-consuming, process of determining their residual vocational capacity.
The committee found that, for some conditions, an anatomical measure of severity is sufficient to meet the listing; however, for most conditions, impairment severity is a relatively insensitive measure of a person’s capacity to function in the workplace or perform other usual life activities. Therefore, in revising most of the cardiovascular listings, the committee adopted the approach of recommending that claimants demonstrate both (1) severe impairment and (2) marked functional limitations. This approach was taken to increase the sensitivity of the Listings, and thus the share of deserving claimants allowed quickly, without increasing the false-positive rate appreciably.
We do not agree that this approach brings subjective functional considerations into purely objective medical decisions. Assessment of degree of anatomical impairment is certainly a medical function, performed as part of a regular medical evaluation of patients to determine treatment needs, but assessment of the person’s functional capacity is also a medical function and can be performed in the medical setting and documented in the medical record.
The most objective way to determine functional capacity of cardiovascular patients is exercise testing, which can be performed by most cardiovascular patients. SSA’s current criteria for deciding whether to pay for an exercise test are too restrictive given what is currently known about the safety of exercise testing, and the committee urges SSA to revise those criteria accordingly.
Evidence also shows that comorbidities prevalent among individuals with cardiovascular disease, such as depression and diabetes, not only worsen the cardiovascular disease, but also reduce functional capacity
beyond the effects of the cardiovascular disease. The committee does not recommend revising SSA’s current policies and procedures for considering comorbidities in the disability determination process, but urges SSA to provide adjudicators with up-to-date information about the impact of comorbidities and to support research on the effects of common cardiovascular comorbidities such as diabetes and major depression on functional capacity and disability (see Recommendation 16-1 in Chapter 16).
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