Exercise radionuclide ventriculography: practical considerations and sensitivity of coronary artery disease detection

Very late survival after vascular surgery

PURPOSE

The aim of this study was to define very late survival in veterans who routinely underwent preoperative assessment of left ventricular function using radionuclide ventriculography (RNVG) before elective major vascular surgery from 7/84 to 7/88 at one Veterans Affairs Medical Center.

METHODS

RNVG defined left ventricular ejection fraction (EF) and determined the presence of ventricular wall motion abnormalities. Patients undergoing elective vascular surgery (n = 310) who had preoperative RNVG were then followed over the years using direct contact, VA administrative databases, and, most recently, the Social Security Death Index.

RESULTS

Follow-up was 6.64 +/- 4.62 years (range 0 to 16.2 years). Current survival is 10% (11/107) after carotid surgery, 12% (10/82) after aortic aneurysm repair, 15% (17/111) after extremity reconstruction, and 0% (0/10) after visceral artery reconstruction (ns). There was no statistically significant difference in mortality between the different types of vascular surgery at 30 days or at 1, 5, and 10 years after surgery (ns). Actual survival rates at 5 years after carotid surgery, aneurysm repair, extremity reconstruction, and visceral reconstruction were 55, 61, 59, and 50%, respectively. Stepwise logistic regression analysis was performed which included preoperatively defined cardiovascular risk factors, type of surgery, and results of RNVG. The final regression model indicated that age, diabetes, smoking at the time of surgery, and low EF were independently associated with overall mortality while angina, prior myocardial infarction (MI), and type of operation were not. Mean survival duration with normal EF (>50%) was 7.99 years versus 4.78 years with low EF (P < 0.001). No patient with severe left ventricular dysfunction (EF < or = 35%; n = 39) or who had postoperative cardiac complications (MI, CHF, ventricular arrhythmia; n = 38) survived to the present.

CONCLUSIONS

Very late survival after major vascular surgery was related to the presence of diabetes, active smoking at the time of surgery, left ventricular function, and postoperative cardiac complications. Since there was no association of overall mortality with angina or prior MI, an aggressive approach to coronary evaluation in such patients might not alter very late survival.

Exercise-induced QRS prolongation in patients with coronary artery disease: a marker of myocardial ischemia

The objective of this study was to investigate the effect of myocardial ischemia on the QRS duration in patients with coronary artery disease since acute myocardial ischemia decreases conduction velocity through the ischemic myocardium and may produce QRS prolongation on the surface electrocardiogram. One hundred fifty patients who underwent cardiac catheterization and exercise radionuclide ventriculography within 1 month of each other were studied. Forty patients had normal coronary arteries and 110 had coronary artery disease. QRS duration decreased with exercise in patients with normal coronary arteries (-3.0 msec, confidence limits -6.2 to 0.2), but increased in patients with coronary artery disease; exercise-induced QRS prolongation was directly related to the number of diseased vessels (4.8 msec in patients with one, 7.8 msec in patients with two, and 13.3 msec in patients with three-vessel disease, p < 0.001). Likewise, QRS duration decreased with exercise in patients without exercise-induced segmental contraction abnormalities (-1.8 msec, confidence limits -3.7 to 0.1), but increased in patients with segmental contraction abnormalities (6.7 msec in patients with one, 13.5 msec in patients with two, and 21 msec in patients with three segmental contraction abnormalities, p < 0.0001). Exercise-induced QRS prolongation was better related to the number of segmental contraction abnormalities than to the number of diseased vessels (p < 0.01). It was concluded that exercise produces QRS prolongation in patients with coronary artery disease in direct relation to the number of diseased vessels and to exercise-induced segmental contraction abnormalities.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac left ventricular function before and during early thyroxine treatment in severe hypothyroidism

In some patients with severe hypothyroidism, thyroxine replacement therapy precipitates or aggravates angina pectoris, whereas in other patients angina pectoris is ameliorated or even cured. Cardiac function in eight severely hypothyroid patients was studied by means of radionuclide ventriculography (RNV) at rest and during supine bicycle exercise before thyroxine treatment, and repeated during treatment before and after administration of 160 mg of oral verapamil. There was an exercise-induced fall in left ventricular ejection fraction (LVEF) in two patients before therapy, and in two additional subjects after 17 d on suboptimal doses of thyroxine. Verapamil attenuated the fall and induced a significant increase in LVEF during exercise (P less than 0.014). No abnormal regional cardiac wall movement (RWM) was observed. After 2 months of thyroxine treatment, LVEF increased significantly during exercise both before and after verapamil (P less than 0.012 and P less than 0.005). These findings are indicative of reversible coronary artery dysfunction. We recommend that, if feasible, thyroxine should be supplemented with verapamil during the early phase of treatment.

Acute elevation of blood carboxyhemoglobin to 6% impairs exercise performance and aggravates symptoms in patients with ischemic heart disease

Acute exposure to carbon monoxide has the potential to impair exercise capacity in patients with ischemic heart disease. The effect of sufficient inhalation of this compound to gradually produce a level of 6% carboxyhemoglobin was studied in 30 nonsmoking patients with obstructive coronary artery disease and evidence of exercise-induced ischemia. After an initial training session, subjects were exposed to air or carbon monoxide on successive days in a randomized double-blind crossover fashion. Cardiac function and exercise capacity were assessed during symptom-limited supine radionuclide ventriculography. On the carbon monoxide day, mean postexposure carboxyhemoglobin was 5.9 +/- 0.1% compared with 1.6 +/- 0.1% (p less than 0.01) after air exposure. The mean duration of exercise was significantly longer after air compared with carbon monoxide exposure (626 +/- 50 s for air versus 585 +/- 49 s for carbon monoxide, p less than 0.05). Actuarial methods suggested that subjects were likely to experience angina earlier during exercise on the day of carbon monoxide exposure (p less than 0.05). Both the level (62 +/- 2.4 versus 60 +/- 2.4%, p = 0.05) and change in left ventricular ejection fraction at submaximal exercise (1.6 +/- 1.6 versus -1.2 +/- 1.6%, p = 0.05) were greater on the air exposure day compared with the carbon monoxide day. The peak exercise left ventricular ejection fraction was not different for the two exposures (57 +/- 2.5% for both). These results demonstrate earlier onset of ventricular dysfunction, angina and poorer exercise performance in patients with ischemic heart disease after acute carbon monoxide exposure sufficient to increase blood carboxyhemoglobin to 6%.

Effects of exercise tolerance, age, and gender on the specificity of radionuclide angiography: sequential ejection fraction analysis during multistage exercise

We investigated the factors that determine the left ventricular ejection fraction response to exercise in 57 middle-aged, untrained patients with angiographically normal coronary arteries. The ejection fraction was measured by blood pool radionuclide angiography during each stage of exercise. Stepwise regression analysis was applied to 39 variables, and the resulting significant variables were then included in a logistic regression model to determine which of them would predict a normal ejection fraction response. By stepwise regression analysis, the best model (F = 5.6, p = 0.0004) was obtained by combining four variables: achieving 85% of maximal predicted heart rate, peak heart rate, number of exercise stages performed, and resting pulse pressure. Only the latter two variables were significant by logistic regression analysis. The specificity of greater than or equal to 5 ejection fraction unit increase at peak exercise was 42%, 75%, and 100% in patients who exercised one, two, or three stages, respectively. Furthermore, the increase in ejection fraction during each exercise stage was independent of age or gender. Thus the standard criteria of normality during exercise radionuclide angiography have high specificity only when applied to patients with good exercise performance, regardless of age or gender.

The efficacy of cardiovascular nuclear medicine exercise studies

Radionuclide stress tests were initially introduced into medicine as new diagnostic tests for coronary artery disease (CAD). These tests are very effective for this purpose when applied to populations with an intermediate pre-test probability of coronary artery disease. Radionuclide stress tests, however, also are used now in guiding many management decisions in patients with established CAD, based on the ability of these tests to assess the extent and severity of myocardial ischemia, the functional significance of coronary stenoses, and myocardial viability. Specific uses beyond diagnosis include decisions regarding whom to catheterize, send to coronary bypass surgery, or angioplasty; risk stratification following myocardial infarction or before noncardiac surgery; and evaluation of the results of therapy. This article reviews both the diagnostic efficacy of radionuclide stress tests and their efficacy in guiding management decisions in patients with known coronary artery disease.

Nuclear scans: a clinical decision making tool that reduces the need for cardiac catheterization

We have assessed the impact of cardiovascular nuclear medicine studies (CVNMS) on physicians' decisions to send patients with suspected ischemic heart disease (N = 439) on to cardiac catheterization at three Bronx hospitals. A change in management plans with respect to catheterization was observed in 31% of cases. Catheterization rates were reduced by 25% among patients referred for resting studies and by 49% for exercise studies (thallium perfusion or exercise wall motion studies). Results of CVNMS had little impact on catheterization decisions for resting study patients (N = 192). Among exercise study patients (N = 247), those with normal results had a relative reduction in catheterization post-CVNMS of 82% vs 27% for patients with abnormal results (p less than 0.001). However, impact of exercise CVNMS test results on post-CVNMS catheterization rates obtained for men only; women with abnormal exercise study results were much less likely to undergo subsequent catheterization (7.7%) than men with abnormal results (41.9%), p less than 0.005, independent of age. The apparent discrepancy in referral for catheterization based on sex needs to be investigated further.

Changes in left ventricular function during exercise and their relation to ST segment changes in patients with angina

The high count sensitivity of the non-imaging nuclear probe affords the possibility of measuring left ventricular ejection fraction continuously during short term interventions. The nuclear probe was used to examine the pattern of change of left ventricular function during dynamic exercise and its temporal relation to ST segment depression in 12 patients with stable exertional angina. After in vivo blood pool labelling with technetium-99m the left ventricular time-activity waveform was detected by the nuclear probe and was continuously recorded on a strip chart. The 15 beat mean ejection fraction and the ST segment level 80 ms after the J point were measured at rest and every 30 seconds during maximal ergometric exercise and during recovery. The mean ejection fraction was 54.3% (range 46-64%) at rest and fell during exercise in all subjects by a mean of 16.8% (range 6-25%). In contrast, in a control group of 16 healthy male volunteers the mean ejection fraction was 55.9% (range 47-64%) at rest and increased in all by a mean of 10.2% (range 3-19%) during exercise. The difference of ejection fraction response to exercise between the patients and controls was due to pronounced increases in relative end diastolic and especially end systolic volumes in the patients. Relative stroke volume differed between patients and controls only at peak exercise. ST segment depression greater than 1 mm developed in 11 of the 12 patients. A decrease of greater than 5% in ejection fraction occurred within 1 minute of starting exercise in nine of the 12, and in 11 patients it preceded the beginning of ST depression. In most of this selected group of patients the ejection fraction had fallen during exercise before the appearance of ischaemic electrocardiographic changes.

Dopamine: its potential for inducing ischemic left ventricular dysfunction

As an agent potentially capable of inducing ischemia in patients with coronary artery disease, dopamine administered intravenously was evaluated as a pharmacologic stress agent by supine radionuclide angiography, and the results were compared with ergometer exercise. In a preliminary group of 11 subjects (4 normal subjects and 7 patients with coronary disease), dopamine alone was administered in increments of 2.5 micrograms/kg per min to a maximum of 15 micrograms/kg per min. There were significant differences between exercise and dopamine in maximal stress heart rates, 129.3 +/- 30.0 versus 88.0 +/- 35.8 beats/min (p less than 0.05) in normal subjects and 118.9 +/- 21.1 versus 87.6 +/- 22.6 beats/min (p less than 0.05) in patients with coronary disease, as well as in maximal stress rate-pressure products, 213.3 +/- 51.4 versus 155.0 +/- 52.5 mm Hg/min X 10(2) (p less than 0.02) in normal subjects and 216.0 +/- 45.6 versus 161.0 +/- 48.6 mm Hg/min X 10(2) (p less than 0.003) in patients with coronary disease. As a result, in these patients the ejection fraction response was significantly different: -3.3 +/- 4.5% with exercise versus + 6.3 +/- 4.6% with dopamine (p less than 0.05). In a second group of 41 subjects (9 normal subjects and 32 patients with coronary disease), atropine (0.6 mg) was administered intravenously before and after every second dopamine dose increment. This produced statistically similar maximal stress heart rates as compared with exercise in all subjects, rate-pressure products in normal subjects and slightly higher values with dopamine in patients with coronary disease: 200.3 +/- 47.2 versus 183.1 +/- 43.0 (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Noninvasive prediction of the angiographic extent of coronary artery disease after myocardial infarction: comparison of clinical, bicycle exercise electrocardiographic, and ventriculographic parameters

To assess alternative criteria for the prediction of multivessel coronary artery disease after myocardial infarction, we compared the clinical, bicycle electrocardiographic, and radionuclide ventriculographic (ejection fraction and wall motion) responses in 110 patients undergoing coronary angiography after myocardial infarction. Ninety-seven of the 110 patients had multivessel coronary artery disease (two or more diseased vessels). Clinical or electrocardiographic abnormalities were observed in 41 of 97 (sensitivity = 43%) patients with multivessel disease, and in only two of 13 (specificity = 85%) patients without multivessel disease. The average information content of these combined clinical and electrocardiographic variables relative to perfect discrimination was 5%. Among the scintigraphic parameters, the conventional criterion for ejection fraction abnormality, a rise of less than 5% had a sensitivity of 72% and a specificity of 62% for multivessel coronary artery disease, while a fall in ejection fraction of 5% or more had a sensitivity of 39% and specificity of 92% for multivessel coronary artery disease. The presence of an exercise wall motion abnormality in the nonadjacent noninfarcted (remote) region had a sensitivity of 82% and specificity of 55% for multivessel coronary artery disease. A more stringent criterion, worsening of remote wall motion with exercise, had a sensitivity of 52% and specificity of 75%. When this latter criterion was combined with a fall in ejection fraction, the sensitivity for multivessel coronary artery disease increased to 62%, specificity remained 75%, and information content increased from 5% to 10%. We conclude that conventional diagnostic criteria for abnormal clinical, bicycle electrocardiographic, or scintigraphic results do not identify patients with additional coronary artery disease after infarction with high accuracy. Two alternative ventriculographic parameters--a fall in ejection fraction and wall motion worsening--are similar to clinical parameters in specificity, but have a higher sensitivity and information content.

Use of electrocardiographic-thallium exercise testing in clinical practice

Although there is a great deal of data on the accuracy of combined electrocardiographic-thallium exercise testing, little is known about the use of these tests in clinical practice. A quantitative likelihood system was employed to characterize referral patterns for such testing, and the impact of test results on the likelihood of coronary artery disease was examined. Two hundred thirteen subjects consecutively referred for the purpose of establishing or excluding the presence of coronary artery disease were studied. No subject had a history of a prior myocardial infarction. By historical evaluation, 96 had a low likelihood of coronary disease (less than or equal to 0.20), 88 an intermediate likelihood (0.21 to 0.80) and 29 a high likelihood (greater than 0.80). As anticipated from theoretical analyses, testing produced the greatest shifts in disease likelihood in subjects with an intermediate pretest disease likelihood, and confirmed the historical evaluation in patients at the extremes of pretest disease likelihood. Therefore, although electrocardiographic-thallium stress testing is best suited for subjects with intermediate pretest disease likelihood, the majority of referrals had either a high or low likelihood. Clinicians appear to value confirmatory results in patients at the extremes of pretest disease likelihood. Electrocardiographic exercise testing would serve a similar purpose.

The effect of dobutamine on exercise performance in patients with symptomatic ischemic heart disease

The effect of dobutamine on exercise performance was assessed in 20 patients with ischemic heart disease (CAD) and a positive stress test. These patients had a wide range of resting left ventricular ejection fraction (range 22% to 69%, mean 42%). Each patient entered a double-blind crossover study in which two identical exercise radionuclide ventriculograms were performed in patients on dobutamine, 5 micrograms/kg/min intravenously, or placebo. Dobutamine increased resting left ventricular ejection fraction. Although ejection fraction fell with dobutamine during submaximal exercise, it remained higher than with placebo. At peak exercise, ejection fraction fell to the same level on dobutamine as with placebo. Dobutamine diminished exercise time and time to ischemia while peak pressure-rate product was unchanged. Four of 20 patients developed complex ventricular premature beats, all while on dobutamine. Although useful when administered to resting patients with acute left ventricular failure, dobutamine's effects may be deleterious in exercising patients with chronic ischemic heart disease.

Incremental value of clinical assessment, supine exercise electrocardiography, and biplane exercise radionuclide ventriculography in the prediction of coronary artery disease in men with chest pain

The incremental value of clinical assessment, exercise electrocardiography (ECG) and biplane radionuclide ventriculography (RVG) in the prediction of coronary artery disease (CAD) was assessed in 105 men without myocardial infarction who were undergoing coronary angiography for investigation of chest pain. Independent clinical assessment of chest pain was made prospectively by 2 physicians. Graded supine bicycle exercise testing was symptom-limited. Right anterior oblique ECG-gated first-pass RVG and left anterior oblique ECG-gated equilibrium RVG were performed at rest and exercise. Regional wall motion abnormalities were defined by agreement of 2 of 3 blinded observers. A combined strongly positive exercise ECG response was defined as greater than or equal to 2 mm ST depression or 1.0 to 1.9 mm ST depression with exercise-induced chest pain. A multivariate logistic regression model for the preexercise prediction of CAD was derived from the clinical data and selected 2 variables: chest pain class and cholesterol level. A second model assessed the incremental value of the exercise test in prediction of CAD and found 2 exercise variables that improved prediction: RVG wall motion abnormalities, and a combined strongly positive ECG response. Applying the derived predictive models, 37 of the 58 patients (64%) with preexercise probabilities of 10 to 90% crossed either below the 10% probability threshold or above the 90% threshold and 28 (48%) also moved across the 5 and 95% thresholds. Supine exercise testing with ECG and biplane RVG together, but neither test alone, effectively adds to clinical prediction of CAD. It is most useful in men with atypical chest pain and when the ECG and RVG results are concordant.

Noninvasive methods for the early detection of doxorubicin-induced cardiomyopathy

Ninety-eight female patients (mean age 54 years) who underwent doxorubicin therapy because of metastatic breast cancer were submitted to radionuclide angiography at rest. Left ventricular ejection fractions (LVEFs) were found to decrease significantly with the increasing cumulative doxorubicin dosage. Patients with prior local radiotherapy showed lower LVEFs at the same dosage level than nonirradiated patients, but the difference was not statistically significant. In a further study, 52 patients (mean age 56 years) were followed up regularly for their history and systolic time intervals prior to each doxorubicin treatment course. Before starting treatment, LVEF values were normal in all cases. Fifteen of these patients complained of dyspnea at some time during the treatment period before the critical cumulative dosage level of 550 mg/m2 was reached. Nine of these 15 patients showed an increase of the PEPI:LVETI ratio (greater than or equal to 0.40) and 12 patients a decrease of the LVEF values at rest at the same time. The rest of the patients did not complain of cardiac symptoms and did not show any significant alterations in systolic-time-interval measurements until the borderline dosage level (550 mg/m2) was attained. To evaluate myocardial function with greater accuracy, these 15 patients were submitted to right-heart catheterization and radionuclide angiography at rest and during exercise. As a result, doxorubicin treatment had to be discontinued in three of these patients because of heart failure of stage III or IV and treatment with methyl digoxin and nifedipine was started. In these three patients cardiotonic medication could produce more or less complete cardiac recompensation. We conclude from our findings that signs of stage-III heart failure in radionuclide angiography performed while the patient is at rest and exercising should be regarded as the upper limit of the therapeutic risk, where further doxorubicin treatment is contraindicated. Cardiotonic medication during cytostatic courses should be avoided, however, because the true functional condition of the myocardium could be masked during a potentially cardiotoxic therapy.

Gold-195m for serial first pass radionuclide angiocardiography during upright exercise in patients with coronary artery disease

Sequential first pass radionuclide angiocardiography can be performed in rapid succession using gold-195m because of its low radiation dose and short half-life (30.5 seconds). In 25 patients with known or suspected coronary artery disease, first pass studies with gold-195m were obtained using a computerized multicrystal gamma camera at rest (n = 29), at the end of each 3 minute stage of exercise (n = 25) and immediately after exercise (n = 23). In 13 patients, assessment of left ventricular function during exercise with gold-195m was combined with thallium-201 stress scintigraphy. Left ventricular ejection fraction at rest assessed with technetium-99m and gold-195m correlated well (r = 0.93). In addition, repeat left ventricular ejection fractions at rest with gold-195m correlated closely (r = 0.96). Comparing peak exercise left ventricular ejection fraction with ejection fraction at rest, abnormal left ventricular reserve was found in 20 of 25 patients. Various abnormal patterns of left ventricular ejection fraction response were noted, showing the diagnostic potential of serial exercise angiocardiography. Thallium-201 myocardial images, obtained on a single crystal gamma camera after multiple gold-195m injections, were all of good diagnostic quality and were abnormal in 10 of 13 patients. Thus, multiple high count rate first pass studies can be obtained with gold-195m during and after exercise, allowing serial study of physiologic changes in left ventricular function during exercise. Thallium-201 myocardial imaging can be performed using the same exercise test, providing direct comparison of myocardial function and perfusion.

The declining specificity of exercise radionuclide ventriculography

Although exercise radionuclide ventriculography was initially reported to be a highly specific test for coronary-artery disease, later studies reported a high false-positive rate. To verify this turnabout, we analyzed the responses in 77 angiographically normal patients; 32 were studied from 1978 to 1979 (the early period), and 45 from 1980 to 1982 (the recent period). Most patients studied in the early period had normal responses (94 per cent for ejection fraction and 84 per cent for wall motion). In contrast, normal responses were less frequent in patients studied in the recent period (49 per cent for ejection fraction and 36 per cent for wall motion, P less than 0.001). The probability of coronary disease before testing was higher in these patients (38 vs. 7 per cent, P less than 0.001). More patients studied in the recent period underwent radionuclide ventriculography before angiography (78 vs. 22 per cent, P less than 0.001), and more of these prior studies had abnormal results than those performed after angiography (55 vs. 6 per cent, P less than 0.0001). Thus, two factors are responsible for the temporal decline in specificity: a change in the population being tested (pretest referral bias) and a preferential selection of patients with a positive test response for coronary angiography (post-test referral bias).

Quantitative phase analysis of exercise radionuclide left ventriculography in normals and patients with coronary artery disease

Using multigated radionuclide ventriculography (RNV), the left ventricular (LV) phase histogram (PH) was used to quantitate LV synchrony at rest and at submaximal and maximal supine exercise in 10 normal and 10 coronary (CAD) patients. Each LV PH was obtained by masking the phase image with an LV region, generated semiautomatically and modified if necessary to minimize ambiguity of LV delineation. The shape and spread of each histogram was characterized by its standard deviation (SD) and skewness (SK). Normals had a tight resting PH with slight negative skewness (SD = 9.06 +/- 0.22 (mean +/- SEM; SK = -0.53 +/- 0.05). CAD patients had a wider resting PH with a larger SD and a significantly more positive skewness reflecting greater contractile asynchrony (SD = 16.53 +/- 2.26; SK = 0.35 +/- 0.22). With exercise the PH distribution for the normals remained tight (SD = 8.1 +/- 0.24) while SK changed little (SK = -0.29 +/- 0.04). In contradistinction, with exercise CAD patients markedly increased the spread of their LV PH (SD = 27.42 +/- 3.77) and increased the number of late pixels (SK = 0.75 +/- 0.15). It is concluded that quantitative PH analysis is a useful adjunct for the analysis of regional asynergy during resting or exercise radionuclide left ventriculography.

Acromegaly and the heart--echocardiographic and nuclear imaging studies

Left ventricular mass (LV mass) and function were assessed in 16 acromegalic patients by echocardiography, and rest and exercise gated blood pool scanning (GBPS) respectively. At the time of study, five patients had active acromegaly, five were hypertensive and three had coexisting coronary artery disease. Increased LV mass was found in six (38%) patients, of whom four were hypertensive and two others had active acromegaly of long duration. One normotensive patient, who did not have coronary disease, had increased LV mass associated with persistently elevated growth hormone (GH) levels for the previous 11 years. Abnormal LV function, as detected by GBPS, occurred only in the three patients with coronary disease. Thus, acromegaly is associated with increased LV mass in hypertensive patients and normotensive patients who have prolonged elevation of GH levels prior to adequate treatment. We found no detectable impairment of LV function, at rest or exercise unless other cardiac disease was present.

Reproducibility of equilibrium radionuclide ventriculography in patients with coronary artery disease: response of left ventricular ejection fraction and regional wall motion to supine bicycle exercise

To evaluate the reproducibility of ejection fraction (EF) and regional wall motion (RWM) analyses by rest and exercise equilibrium radionuclide ventriculography (RNV) in the presence of coronary artery disease (CAD), 18 patients underwent two maximum, multistage supine bicycle exercise studies separated by an interval of 2 weeks. There were no significant differences in EF between the two studies, both at rest (56.0 +/- 13.8% vs 58.2 +/- 11.7%, p = NS) and with exercise (51.1 +/- 17.6% vs 54.3 +/- 17.6%, p = NS) and a highly significant correlation was shown between the two groups of values (rest r = 0.90, exercise r = 0.93, p less than 0.001). There was no significant difference in the change from rest to exercise (-4.9 +/- 12.0% vs -3.8 +/- 11.5%, p = NS) between the two studies and the correlation was highly significant (r = 0.69, p less than 0.01). The interstudy variabilities were 2.2 +/- 6.1% and 1.2 +/- 7.3% for rest and exercise, respectively, and 2.0 +/- 9.2% for the change from rest to exercise. Ninety-four percent of both rest and exercise regions had similar RWM. Eighty-one percent of the abnormally contracting regions were common to both exercise studies. Utilizing conventional criteria for the diagnosis of CAD, 11 patients had abnormal EF response and nine had abnormal RWM response to exercise on both studies. Combining EF and RWM criteria resulted in the diagnosis of CAD in 15 patients in both studies. We conclude that: (1) there were no significant differences in rest and exercise radionuclide EF and RWM between two supine bicycle exercise studies performed 2 weeks apart in patients with stable CAD and there were significant correlations between the two studies; (2) despite these correlations, the interstudy variabilities emphasize the need for the inclusion of reproducibility studies in all evaluations of interventions by exercise radionuclide ventriculography; and (3) the variations in EF and RWM response to exercise result in lack of uniformity between the two studies regarding the diagnosis of CAD based on conventional RNV criteria.

Radionuclide angiographic correlation of the R wave, ejection fraction, and volume responses to upright bicycle exercise

The change in the R wave and the response of the ejection fraction to upright bicycle stress testing with radionuclide angiographic studies were determined for 18 control subjects and 29 patients with coronary arterial disease (70 percent stenosis or more). In the control group, all had an increase in the ejection fraction from 64.8 +/- 7.7 to 75.7 +/- 9.4 percent with stress (P less than 0.01). All control subjects had a decrease in the R wave with exercise. In the group with coronary arterial disease, most patients had a decrease in the ejection fraction averaging from 63.5 +/- 10.9 to 58.6 +/- 12.8 percent (P less than 0.01). An appropriate response of the R wave and ejection fraction (decrease in R wave and increase in ejection fraction or increase in R wave and decrease in ejection fraction) occurred in 23 (79 percent) of 29 subjects (P less than 0.005). The sensitivity, specificity, and predictive value for the response of the ejection fraction were as follows: 83 percent (24/29); 100 percent (18/18); and 100 percent (24/24). Of the patients with coronary arterial disease and an increase in the R wave, 17 (94 percent) had multivessel disease, while six (55 percent) of 11 with a decrease in the R wave had multivessel disease (P less than 0.05). The systolic volume decreased in all control subjects by -15.9 +/- 8.6 units (P less than 0.01) and increased in most of the group with coronary arterial disease by 13.7 +/- 17.8 units (P less than 0.01) in response to stress. There were 20 of 29 patients (P less than 0.05) with an appropriate response of the R wave and systolic volume to stress (increase in R wave and systolic volume or decrease in both). The change in the R wave did not correlate with the change in the diastolic volume with stress (P greater than 0.05). Changes in the R wave with exercise correlate with the change in the ejection fraction (and hence ventricular function) and with the changes in systolic volume, which may be one of the mechanisms of the response of the R wave, suggesting that the change in the R wave is related to changes in contractility. Increase in the R wave with stress suggests multivessel coronary arterial disease.

Exercise-induced regional wall motion abnormalities on radionuclide angiography. Lack of reliability for detection of coronary artery disease in the presence of valvular heart disease

Exercise-induced regional wall motion abnormalities on radionuclide angiography have been thought to be a reliable indicator of coronary artery disease. To evaluate their reliability, particularly in patients with valvular heart disease, exercise radionuclide angiography was performed in 12 normal subjects, 35 patients with coronary artery disease and 19 patients with valvular heart disease and normal coronary arteries. Exercise-induced regional wall motion abnormalities were found in none of the normal subjects, 63 percent of the patients with coronary artery disease and 42 percent of those with valvular heart disease and were predominantly inferoapical in location in the group with valvular heart disease. We conclude that exercise-induced regional wall motion abnormalities are not reliable for the detection of coronary artery disease in patients with valvular heart disease.

Physiologic Intervention in Cardiovascular Nuclear Medicine

Homeostasis of cardiac output is maintained by a complex intergration of many physiologic responses, both central and peripheral, including pulse,the contractile state of the ventricle, and pre-and after load. In the abnormal ventricle at rest, any or all of the measurable parameters that define left ventricular function may be normal. However, in disease states, exercise can provoke abnormalities in these parameters indicating a reduction in myocardial reserve. Regional asynergy occurs in patients with significant ischemic heart disease during exercise reflecting a local supply-demand mismatch. Recently, radionuclide ventriculography has been combined with exercise techniques in attempts to elucidate details of the normal and abnormal ventricular response to stress noninvasively. The majority of data describe the response of the ventricle during graded supine bicycle exercise. The normal response is to increase myocardial contractility, reducing end-systolic volume, while end-diastolic volume remains constant. This results in an increase in ejection fraction. In ischemic ventricles, regional asynergy develops and ejection fractions may either fall or fail to rise. This appears to be accomplished by an increase or no change in the end-diastolic volume, with an increase in end-systolic volume, particularly in patients with angina during exercise. Radionuclide methods can be applied to large mumbers of patients providing informaton that is unobtainable by more invasive procedures. This review traces the development of knowledge of the ventricular response to exercise, emphasizing the role of radionuclide ventriculography. Although radionuclide angiography has the capacity for advancing the understanding of the ventricular response to exercise, the technical limitations of this technique in specific diagnostic conditions has yet to be defined adequately.

Monitoring cardiac function with nuclear techniques

Noninvasive imaging with radioactive tracers has become widely used since its introduction in the early 1970s. Improvements continue to be made in the techniques and the clinical applications. Much of the information provided by these techniques is new. The first transit studies are used mainly in the evaluation of pulmonary transit time, detection of intracardiac shunting, evaluation of right ventricular function, measurement of ejection fraction and detection of wall motion abnormalities at rest and after exercise. The gated blood pool study is found to be most useful in assessment of global left ventricular function, regional wall motion, valve regurgitation and right ventricular function. The techniques of nuclear cardiac imaging are noninvasive, simple, successfully performed in almost 100 percent of cases. They are easy to interpret, able to be quantified and able to be almost totally automated. Their use is likely to become more widespread in the future.

Radionuclide wall motion study and ejection fraction in clinical practice

Assessment of ventricular function is important in diagnosis and as a predictor of survival in many cardiopulmonary disorders, and analysis of ventricular function is one of the oldest applications of radioactive tracers in medicine. A sequence of parallel developments in instrumentation, radiopharmaceuticals, and nuclear medicine computers has allowed implementation of accurate, sensitive, noninvasive techniques for analysis of both right and left ventricular function. Techniques, indications, applications, and information that can be obtained are discussed.