Diagnostic Procedures

Noninvasive procedures provide important information in addition to that provided by the history and physical examination. Invasive procedures may also be needed (see Table 84-1).

Electrocardiography

Although left ventricular wall thickness and mass tend to increase with age, no age-specific criteria for ECG diagnosis of left ventricular hypertrophy have been developed. Limb lead and precordial QRS voltages decrease with age. Age-related increases in the frequency of ectopic beats, in PR and QT intervals, in left axis deviation, and in the frequency of right bundle branch block have no prognostic significance for elderly persons without clinical evidence of heart disease.

The most common ECG abnormality in the elderly is nonspecific changes in ST segments or T waves, which are often due to use of digoxin, a diuretic, an antiarrhythmic, or a psychoactive drug; such changes have little independent prognostic significance. However, if the patient is not using any of these drugs and if voltage criteria for left ventricular hypertrophy are met, these changes predict an increased risk of cardiovascular morbidity and mortality.

In the elderly, an ECG pattern of poor R-wave progression in leads V₁ to V₄ has low specificity and predictive value for anterior myocardial infarction (MI), probably because of age-related increases in resting lung volume and anteroposterior chest diameter. Thus, ECG may not be as useful in detecting silent MI in the elderly as in younger persons.

Ambulatory ECG monitoring, usually for 24 hours, is useful for elderly patients with unexplained syncope, palpitations, or other evidence suggesting major arrhythmias or conduction disorders. Patients with known organic heart disease, especially those who have had an MI, are appropriate candidates because they are the most likely to have a major arrhythmia during monitoring. However, because complex arrhythmias during ambulatory ECG monitoring are relatively common among healthy elderly persons, patients should record symptoms in a diary so that symptoms can be correlated with ECG rhythm disturbances. Ambulatory ECG monitoring is also useful for detecting asymptomatic episodes of myocardial ischemia.

When symptoms are infrequent and nondisabling, an ECG event recorder is a better choice because it is economical and can provide up to 6 weeks of intermittent monitoring. Loop event recorders can capture up to 4 minutes of retrospective ECG data before patient activation and can transmit the ECG via telephone to a central recording facility when symptoms occur.

Electrophysiologic Testing

Electrophysiologic testing includes recording of His bundle activity, atrial pacing, programmed atrial or ventricular stimulation, and mapping of tachyarrhythmias. However, in elderly patients, it is used mainly for programmed ventricular stimulation when coronary artery disease (CAD) or a life-threatening ventricular arrhythmia is present. Electrophysiologic testing in the elderly has a low morbidity rate and helps determine the need for antiarrhythmic drugs or for an implantable cardioverter-defibrillator.

Table Tilt Testing

Tilt table testing is usually recommended for patients who have unexplained syncope but do not have structural heart disease. Patients are typically tilted at a 60 to 80° angle on a motorized table for 15 to 20 minutes while their blood pressure and heart rate are continuously monitored. If hypotension (with or without bradycardia) does not occur, patients are given an infusion of isoproterenol sufficient to accelerate the heart rate by 20 beats/minute, and the test is repeated. The procedure produces many false-positive results and must be used only for patients with definite syncope and negative ambulatory ECG results. Diagnostic sensitivity tends to be lower but specificity tends to be higher in elderly patients with syncope than in younger patients.

Exercise Testing

Exercise testing is generally safe for the elderly (see Table 84-2). Treadmill or bicycle exercise testing with continuous ECG monitoring is an efficient, inexpensive procedure for diagnosing CAD and determining the prognosis for patients with known CAD, especially those who have had an MI. Test sensitivity increases with patient age, from 56% in patients < 40 to 85% in those > 60. This correlation is consistent with the higher prevalence and greater severity of CAD in the elderly. Test specificity decreases modestly with patient age, from 84% in patients < 40 to 70% in those > 60, probably because left ventricular hypertrophy, nonspecific resting ST-segment abnormalities, and valvular heart disease are more common among elderly patients.

Exercise-induced ST-segment depression has diagnostic and prognostic significance for elderly patients with chest pain. A reduced exercise capacity, a blunted increase in the heart rate-blood pressure product, and the occurrence of major ventricular arrhythmias during exercise indicate high risk of cardiac death for elderly patients who have had an MI.

The following age-related changes should be considered when exercise testing is performed in elderly patients:

• The elderly have a lower maximal aerobic capacity, so testing should begin at a level requiring low energy expenditure.
• Maximal heart rate decreases progressively by about 1 beat/ minute yearly until at least about age 90.
• Systolic blood pressure at rest and at any given submaximal external workload is higher in the elderly, although age-related differences are less prominent at maximal effort.
• The ability to exercise is often limited by conditions unrelated to the heart (eg, arthritis, neurologic disorders, peripheral vascular disease).
• Elderly persons may not exercise maximally because of psychologic factors (eg, unfamiliarity with vigorous exercise, fear, insufficient motivation).

Alternatives to treadmill exercise testing include bicycle ergometry, arm ergometry, atrial or esophageal pacing, and pharmacologic stress testing with IV dipyridamole, adenosine, or graded IV infusions of dobutamine. If dobutamine increases the heart rate to < 85% of predicted maximum, atropine may be added. These pharmacologic stress tests are safe and effective for elderly patients and are preferred when patients cannot perform treadmill or bicycle exercise--eg, because of musculoskeletal or pulmonary disorders.

Thallium-201 myocardial perfusion scintigraphy during exercise or pharmacologic stress testing is considered the most accurate noninvasive test for detecting CAD in all age groups. Perfusion defects detected at rest generally indicate a previous MI. Segmental defects that are detected during exercise (or pharmacologic stress testing) and that resolve or improve within 3 to 4 hours indicate exercise-induced ischemia. This imaging procedure can be used to screen for CAD in the many elderly patients who have left ventricular hypertrophy or bundle branch block or who are receiving digoxin or other antiarrhythmic drugs.

The procedure's sensitivity and specificity for CAD is nearly 90% for patients of all ages. The extent of the exercise-induced defect is a useful prognostic indicator for elderly patients with known or suspected CAD. Adding tomographic imaging increases sensitivity but may decrease specificity for mild disease. In patients >= 70, IV dipyridamole-thallium imaging has a sensitivity of 86% and a specificity of 75%. Use of IV adenosine instead of dipyridamole results in a higher incidence of adverse effects, such as conduction system disturbances or arrhythmias caused by impulse formation.

Technetium-99m sestamibi produces better images than thallium and is useful for elderly patients with chronic obstructive pulmonary disease or marked obesity.

Chest X-ray

When rales are detected, a chest x-ray may be indicated to document left-sided heart failure. When pulmonary hypertension is suspected, a chest x-ray can confirm the diagnosis by showing large central pulmonary arteries with oligemic lung fields.

Aortic knob calcification is detected in about 30% of the elderly but has no pathologic significance. In contrast, intracardiac calcification, most commonly on the aortic valve and the mitral annulus, is almost always pathologic; it signifies valvular stenosis. In the elderly, coronary artery calcification, best seen with fluoroscopy, does not necessarily signify major stenosis, as it does in younger patients. Calcification of the pericardium (due to constrictive pericarditis) or the left ventricular wall (due to an old MI) is occasionally also seen.

Echocardiography

In the elderly, echocardiography is useful for assessing left ventricular chamber size and function after diagnosis of heart failure or after acute MI; for assisting in the differential diagnosis of systolic murmurs, especially those grade 3/6 or higher in loudness; for measuring left atrial size and assessing left ventricular function in patients with new atrial fibrillation; for determining pulmonary artery pressures in patients with heart failure; for confirming the presence of pericardial effusion or tamponade; and for detecting a left ventricular aneurysm. Echocardiography can detect thickened aortic or mitral valve leaflets or a calcified mitral annulus, which are the most common sources of systolic murmurs in the elderly. Atrial myxomas, left ventricular thrombi, and valvular vegetations are best detected by echocardiography.

Echocardiography performed immediately after treadmill or pharmacologic stress testing may be used instead of radionuclide perfusion imaging to detect myocardial ischemia (which is indicated by wall motion abnormalities) and to determine prognosis. For patients >= 70, dobutamine stress echocardiography, which is the preferred noninvasive test for the elderly by many clinicians, has a sensitivity of 87%, a specificity of 84%, and an accuracy of 86% for the diagnosis of CAD. Adenosine stress echocardiography has a sensitivity of 66%, a specificity of 90%, and an accuracy of 73%. Exercise echocardiography has a sensitivity of 85% and a specificity of 77%.

M-mode echocardiography can detect age-related changes such as small increases in aortic root and left atrial dimensions, an increase in left ventricular wall thickness with no change in cavity size, and a decrease in mitral valve E-F closure slope (the rate of mitral valve closure in early diastole). Despite these changes, values for elderly persons usually remain within the limits of what is considered normal for younger persons.

Doppler echocardiography is used to quantify aortic valve stenosis. It is also used to assess diastolic dysfunction, particularly in patients with heart failure of unclear etiology. Doppler echocardiography can be used to predict length of survival for elderly patients with heart failure on the basis of E- and A-wave velocity measurements. Color Doppler echocardiography, with flow mapping, is useful for detecting and estimating the severity of valvular regurgitation. Mild multivalvular regurgitation is common among otherwise healthy elderly persons, so regurgitation is significant only if it is moderate or severe.

Transesophageal echocardiography is safe for elderly patients and should be considered for those with suspected heart disease if transthoracic echocardiography is not diagnostic. Transesophageal echocardiography is particularly useful for detecting aortic dissection, valvular vegetations, thrombi in the left atrium or left atrial appendage, and prosthetic valve dysfunction in patients who have the appropriate clinical presentation. Elderly patients with intra-aortic atherosclerotic debris detected by transesophageal echocardiography are at increased risk of thromboembolic events during cardiac surgery.

Intravascular ultrasonography allows detailed morphologic assessment of CAD but is expensive and invasive. This procedure may be useful for determining the suitability of a specific intervention (eg, balloon angioplasty, laser therapy, stent placement) for patients with CAD.

Radionuclide Ventriculography

Radionuclide ventriculography is the most accurate procedure for assessing global left and right ventricular function. It is especially useful for patients with chest wall abnormalities or pulmonary hyperinflation (about 25% of elderly patients), because technically adequate echocardiograms cannot be obtained in them. Two techniques are used: With the first-pass technique, the initial passage of technetium 99m through the cardiac chambers is recorded. With the more commonly used gated blood pool (equilibrium) technique, technetium 99m is allowed to equilibrate in the blood, and then ECG-gated (synchronized) images are recorded during many cardiac cycles. Both techniques can accurately measure global and regional left ventricular systolic performance as well as changes in left ventricular volume.

In elderly patients with suspected CAD, the first-pass or gated technique can be used to measure the left ventricular ejection fraction during bicycle exercise. Radionuclide ventriculography (as well as myocardial perfusion imaging) is particularly useful when ST-segment changes cannot be reliably interpreted because of left bundle branch block, left ventricular hypertrophy, or treatment with digoxin. An abnormal exercise response in elderly persons is best defined as any decrease in ejection fraction from the resting value. A regional wall motion abnormality that occurs during exercise is considered a specific indicator of CAD.

Positron Emission Tomography

Positron emission tomography is used to assess myocardial blood flow and metabolism. The procedure is very sensitive, but its diagnostic usefulness in the elderly is unknown. It is costly and requires an on-site cyclotron to generate radioisotopes.

Computed Tomography

CT of the heart is useful for diagnosing cardiac masses and pericardial effusions and may help detect pericardial thickening and distinguish pericardial fat from effusion. Echo-free pericardial spaces, indicating fat or effusion, increase in prevalence with age and occur in about 10% of women > 80.

Electron-beam CT detects CAD by determining the density of calcifications in the arterial wall; a calcium score above a predetermined threshold suggests significant luminal narrowing. The presence of calcium in coronary arteries is highly specific for CAD in younger patients; however, with age, this specificity decreases, from 74% in patients < 40 to 34% in those > 50. Because of the low specificity, this procedure is not recommended for diagnosing CAD in the elderly. The patency of coronary artery bypass grafts can be assessed using this procedure. It may be used instead of cardiac catheterization after bypass surgery, but IV injection of iodinated contrast media is required.

Magnetic Resonance Imaging

MRI can characterize cardiac anatomy and metabolism without use of ionizing radiation. It can assess myocardial viability in patients who have had an infarction and in those who have chronic heart failure or many other disorders. It is an alternative to echocardiography for measuring chamber size and thickness. ECG-gated imaging allows ventricular function assessment; however, it is expensive, restricting its use in primary diagnosis.

Cardiac Catheterization and Coronary Angiography

Cardiac catheterization with coronary angiography remains the gold standard for diagnosis and quantitation of CAD. It is the only procedure that directly measures intracardiac pressures and defines coronary artery anatomy. The risks of cardiac catheterization, including cerebral and peripheral embolization, renal failure, and death, are increased for the elderly. Risks may be increased because elderly patients are more likely to have preexisting coronary and peripheral vascular disease, renal insufficiency, and left ventricular dysfunction.

The incidence of death and major complications associated with coronary angiography in patients >= 60 is low but is still significantly higher than that in younger patients (see Table 84-3). The incidence is higher in the elderly partly because cardiomegaly and left ventricular dysfunction are more common and because obtaining vascular access is more difficult. Nonetheless, coronary angiography is appropriate for elderly patients with CAD when revascularization is being considered.

Digital subtraction angiography, a computer-enhanced imaging technique, may be safer because the amount of contrast media can be reduced by 75%.