Scintigraphic quantification of myocardial ischemia: a new approach

Visualization of the improvement of myocardial perfusion after coronary intervention using motorized fractional flow reserve pullback curve

This study aimed to evaluate the feasibility and utility of using motorized pullback of the pressure guidewire to provide a graphic assessment and prediction of the benefits of coronary intervention. Fractional flow reserve (FFR) measurements were performed with motorized pullback imaging in 20 patients who underwent successful percutaneous coronary intervention (PCI) of the left anterior descending artery. Physiological lesion length (PLL) was calculated using frame counts to determine stent length. FFR area was calculated by integrating the FFR values recorded during pullback tracing (FFRarea). The percentage increase in FFR area (%FFRarea) was defined as the ratio of the difference between the pre- and post-intervention FFRarea to the total frame count. The average FFR values were enhanced following PCI, from 0.64 to 0.82, and the median value of the difference between pre- and post-interventional FFR values (D-FFR) and %FFRarea were 0.13 and 10.6%, respectively. The %FFRarea demonstrated a significant positive correlation with D-FFR (R², 0.61; p < 0.01). PLL tended to be longer and the %FFRarea was smaller in lesions with a gradual pressure-drop pattern than those with an abrupt pressure-drop pattern (35.37 vs. 20.40 mm, p = 0.07; 5.78 vs. 16.21%, p < 0.05, respectively). Motorized pullback tracing was able to identify the extent and location of stenosis and help in appropriate stent implantation, in addition to visualizing and quantifying the improvement in FFR following PCI.

Prevalence, characteristics, and risk stratification of electrocardiographic and symptomatic silence of myocardial ischemia despite scintigraphically evidenced ischemia in symptomatic patients presenting with severe coronary artery stenosis

Symptoms of angina pectoris and transient ST-segment depression are most commonly used to evidence acute myocardial ischemia during exercise testing. However, the diagnostic accuracy of either or both criteria in relation to clinical characteristics and the patient's exercise response has been a subject of controversy. The prevalence and severity of symptoms of angina pectoris and/or ST-segment depression were studied prospectively in 147 consecutive patients with a history of daily angina pectoris, scintigraphic evidence of exercise-induced myocardial ischemia, and coronary artery stenosis > 75%. Logistic regression analysis was applied to determine absence of any or both criteria by the clinical characteristics or exercise response of the patient. During exercise testing, ST-segment response failed to prove scintigraphically evidenced myocardial ischemia in 14/147 patients (10%) and 35/147 patients (24%) when ST-segment depression > or = 0.1 in either > or = 1 or > or = 2 ECG leads was chosen. Symptoms of angina pectoris were found to be absent in 69/147 patients (47%). Only 58 patients (40%) suffered from angina and met the ECG criterion at the time of scintigraphic myocardial ischemia. Absence of ST-segment depression was best predicted by clinical variables such as large myocardial infarction (increase: 2.6 times, p = 0.007), number of stenoses < or = 2 (2.0 times, p = 0.023), and presence of diabetes mellitus (4.3 times, p = 0.035). Painless myocardial ischemia was determined by blood response to exercising. Thus, a double product > 23 increased the risk of painless myocardial ischemia by 1.5 times (p = 0.017).(ABSTRACT TRUNCATED AT 250 WORDS)

What is the role of silent coronary artery disease and left ventricular hypertrophy in the genesis of ventricular arrhythmias in men with essential hypertension?

Ventricular arrhythmias are not uncommon in patients with hypertension, are often attributed to left ventricular hypertrophy and are thought to be associated with an increased risk of sudden death. However, underlying silent coronary artery disease, another potential cause of ventricular arrhythmias, is often present in the same patient group. Therefore, the prevalence of ventricular arrhythmias was prospectively examined in 183 consecutive asymptomatic men with hypertension with neither clinical nor electrocardiographic (ECG) evidence of coronary artery disease in whom technically adequate echocardiograms could be obtained. After previous therapy had been withdrawn for greater than or equal to 4 days, each patient underwent exercise or dipyridamole thallium-201 scintigraphy, 48-h Holter ambulatory ECG monitoring and echocardiography for measurement of the left ventricular mass index. Forty patients (22%) had frequent ventricular ectopic activity, defined on the basis of greater than 10 premature ventricular complexes/h (38 patients) or ventricular tachycardia (11 patients), or both. A higher proportion of patients with than without a reversible thallium-201 defect had frequent premature ventricular complexes (33% vs. 18%, p less than 0.02) or ventricular tachycardia (14% vs. 4%, p less than 0.02). Similarly, more patients with than without left ventricular hypertrophy (defined as left ventricular mass index greater than or equal to 134 g/m2) had frequent premature ventricular complexes (29% vs. 15%, p less than 0.05) and ventricular tachycardia (12% vs. 2%, p less than 0.01). By stepwise logistic regression analysis, both findings were independent predictors of ventricular arrhythmia, which was present in 53% of patients with both abnormalities, but in only 12% of those with neither abnormality.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of daily high-intensity exercise on myocardial perfusion in angina pectoris

Forty male patients with chronic stable angina pectoris and no prior myocardial infarction were studied by planar thallium scintigraphy with use of circumferential profile analysis. Ischemic defects were assessed by measuring degrees of circumference involved and area of defect. Data were collected for 3 vascular regions in each of 3 views (anterior, 45 degrees and 65 degrees left anterior oblique projection). Patients were then randomized to exercise and control groups, the former training for a period of 1 year using the Canadian Airforce plan for physical fitness. After 1 year, both groups were restudied. Exercise training produced a 34% reduction in degrees of ischemia overall (p less than 0.02), the most significant change being seen on the anterior view (72 degrees +/- 59 degrees before vs 30 degrees +/- 35 degrees after training). Regional analysis showed markedly improved perfusion anterolaterally and apically on the anterior view and anteroseptally on the 65 degrees left anterior oblique view. These improvements support the hypothesis that exercise training improves myocardial perfusion by enhanced collateral function.

ST/HR slope and improved exercise ECG detection of myocardial ischemia in patients with suspected coronary artery disease

Predictive values of ST/HR slope and ST-segment displacement during symptom-limited exercise were determined in 85 patients who underwent coronary angiography for suspected coronary artery disease, using perfusional and functional radionuclide images with 99mTc-2-methoxy-isobutil-isonitrile as an index of stress-induced myocardial ischemia. ST/HR slope showed a better sensitivity than conventional stress-induced changes of ST-segment displacement (96% vs. 73%, respectively). In patients with clinical suspicion of coronary artery disease, the main result was the negative predictive value of ST/HR slope when compared with conventional ST-segment displacement (98% vs. 41%). ST/HR slope was unable to perfectly separate patients with different degrees of ischemia, however, subjects without scintigraphic signs of stress-induced ischemia and patients with ischemic impairment in three myocardial regions were correctly identified as distinct populations. In patients with a previous myocardial infarction, no difference was found between the two criteria and a wide overlap of ST/HR slope values was present. The authors conclude that ST/HR slope is useful to detect the rate of change in electric parameters during exercise and might therefore more adequately be used to separate normal from definitely abnormal responses to exercise.

Is quantitative analysis superior to visual analysis of planar thallium 201 myocardial exercise scintigraphy in the evaluation of coronary artery disease? Analysis of a prospective clinical study

Quantitative analysis of myocardial exercise scintigraphy has been previously reported to be superior to visual image interpretation for detection of the presence and extent of coronary artery disease. Computer analysis of perfusion defects and washout rate of thallium 201 was performed on scintigrams from a group of 131 consecutive patients (prospective group), using criteria defined from a previous group of 72 patients (initial group), and compared with visual interpretation of scintigrams for detection and evaluation of coronary artery disease. The sensitivity of the quantitative technique with regard to overall detection of coronary artery disease was not significantly different from the visual method (69% and 74%, respectively), whereas the specificity was higher (86% and 68%). Quantitative analysis did not increase the sensitivity of thallium imaging over the visual method in the left anterior descending artery (46% vs 65%) and the right coronary artery (51% vs 72%) but did increase sensitivity in the left circumflex artery (75% vs 47%). Whereas in the initial group quantitative analysis resulted in a better identification of multivessel disease (sensitivity 81% vs 57%), in the prospective group sensitivity decreased (54% vs 67%) without significant loss of specificity. The initial group had a 40% incidence of three-vessel disease and the prospective group, 22% (P less than 0.05). One-vessel disease was higher in the prospective group (32% vs 11%, P less than 0.05). Thus, assessing the quantitative technique in a larger prospective patient population, there was no improvement of detection of the presence and extent of coronary artery disease when compared with visual interpretation.

Limitations of regional myocardial thallium clearance for identification of disease in individual coronary arteries

The purpose of this study was to critically evaluate the usefulness of postexercise regional myocardial thallium-201 clearance for identifying disease in individual coronary arteries. Exercise and redistribution planar imaging studies were performed in 114 subjects, including 19 normal volunteers and 95 patients undergoing cardiac catheterization (70 with and 25 without greater than or equal to 50% narrowing in one or more coronary arteries). Thallium clearance was measured from predefined myocardial regions corresponding to the left anterior descending, left circumflex and right coronary arteries and was expressed as the percent decrease in activity at 4 h, assuming monoexponential clearance. In regions perfused by a normal or insignificantly diseased coronary artery, mean 4 h clearance was 58.9 +/- 9.4% for normal volunteers, 43.1 +/- 15.5% for catheterized patients without coronary artery disease and 36.3 +/- 24.9% for catheterized patients with coronary artery disease (p less than 0.001 patients with coronary artery disease versus normal volunteers). Clearance from normal regions was significantly associated with two measures of exercise performance: percent of predicted maximal heart rate achieved (r = 0.49) and exercise duration (r = 0.35). In regions perfused by a stenotic coronary artery, mean clearance was lower (31.1 +/- 19.8%) but was not significantly different from that in normal regions in the same patients. Clearance from diseased regions was also associated with maximal exercise heart rate (r = 0.28) and exercise duration (r = 0.41), but not with percent coronary artery stenosis (r = 0.02). After taking exercise performance into account, the number of diseased vessels or the presence or absence of disease in a given vessel had little influence on regional thallium clearance. Although measurement of regional post-exercise thallium clearance may help to identify stenotic coronary arteries in selected patients, variability related to exercise performance and other physiologic and technical factors greatly limits the clinical usefulness of absolute thallium clearance measurements.

Usefulness of thallium-201 scintigraphy in predicting the development of angina pectoris in hypertensive patients with left ventricular hypertrophy

Hypertension and left ventricular (LV) hypertrophy are independent risk factors for the development of coronary artery disease. To determine whether patients at higher risk for coronary artery disease can be identified, 40 asymptomatic hypertensive men with LV hypertrophy were prospectively studied using exercise thallium-201 scintigraphy and exercise radionuclide angiography. Endpoints indicative of coronary artery disease were defined as the subsequent development of typical angina pectoris, which occurred in 8 patients during a median follow-up of 38 months, or myocardial infarction, which did not occur. The exercise electrocardiogram was interpreted by standard ST-segment criteria and by a computerized treadmill exercise score. Abnormal ST-segment responses were present in 16 of the 40 hypertensives (40%), whereas the treadmill score was positive in 8 of those same 40 patients (20%). Scintigraphic perfusion defects assessed both visually and semiquantitatively were observed in 8 of 40 (20%) patients. An abnormal ejection fraction response to exercise was present in 40% (16 of 40) of patients, and 3 of 40 (7.5%) developed new wall motion abnormalities during exercise. Six of 8 patients with either perfusion defects or abnormal treadmill score developed typical angina during follow-up. All 5 patients with concordant positive exercise scintigrams and treadmill score developed chest pain during follow-up and had coronary artery disease confirmed by coronary angiography. However, only 7 of 16 (44%) patients with positive ST changes or abnormal ejection fraction responses during exercise developed chest pain during follow-up. In contrast, of 32 patients with negative scintigrams only 2 developed atypical chest pain syndromes, and significant coronary artery disease was excluded by angiography in 1 patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Systemic hypertension, left ventricular hypertrophy and coronary artery disease

The potential mechanisms for the development of myocardial ischemia in hypertensive left ventricular (LV) hypertrophy involve changes in the coronary circulation characterized by a reduction of coronary vascular reserve and an acceleration of the atherosclerotic process. This combination of factors is probably reflected in the epidemiologic findings of increased coronary morbidity and mortality in hypertension, particularly when it is associated with LV hypertrophy. The failure of several antihypertensive trials to reduce coronary morbidity and mortality emphasizes the importance of early detection of significant coronary artery disease (CAD) among hypertensive patients with LV hypertrophy. A strategy to detect asymptomatic CAD based on combined probability of 2 noninvasive tests is discussed. Results obtained in hypertensive LV hypertrophy showed a 20% to 30% incidence of abnormal exercise test results, and these positive findings were predictive for the development of typical angina during a 3-year follow-up. Based on these results and reported data, it is extrapolated that patients with silent ischemia may contribute up to 40% of the coronary mortality observed in previous antihypertensive trials. These findings suggest the need for an early detection and separate follow-up of these patients with silent CAD, to better assess the influence of antihypertensive treatment on coronary morbidity and mortality.

Computer versus visual analysis of exercise thallium-201 images: a critical appraisal in 325 patients with chest pain

Although computer-aided analysis of planar thallium images has been previously reported to be superior to visual analysis, a segment-by-segment comparison of all thallium variables (presence of initial defect, presence of redistribution, and presence of abnormal lung:heart thallium ratio) has not been performed with the use of both methods. In the present study, such a comparison was performed to determine which thallium variable(s) are superior, when the computer method is used. In addition, both methods were compared to determine their correlations with the angiographic extent of coronary artery disease (no disease, or one-vessel disease vs multivessel, or left main disease) and the occurrence of future events (cardiac-related death or nonfatal myocardial infarction). Computer-aided analysis was superior to visual analysis (an average of three independent blinded observers) for detection of coronary disease because: (1) it was more specific for detecting initial defects despite having the same sensitivity (89.6% vs 91.0%, p = NS) and (2) it was more sensitive for detecting redistribution in the territory of a stenosed vessel (68% vs 46%, p less than 0.001). However, absolute myocardial clearance of thallium had very poor specificity compared to visually assessed redistribution. Only when segmental clearance was considered abnormal on a relative basis (if it was slower by 98% or more than the fastest clearing segment in the heart) did abnormal clearance achieve the same specificity (99%) and a better sensitivity (60% vs 48%, p less than 0.01) than visual analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative aspects of myocardial perfusion imaging

Computer quantitation of myocardial perfusion images has enhanced the detection of thallium perfusion abnormalities compared to visual analysis. Computer analysis is more specific than visual analysis for detection of initial defects and more sensitive for detection of redistribution. Computer analysis is equally good for detecting thallium abnormalities in the distribution of the three major coronary arteries. Measurement of absolute clearance of thallium results in an unacceptable high false-positive rate. However, when clearance in a myocardial segment is compared to the fastest clearing segment in the heart, the specificity of clearance improves significantly. Quantitation of lung:heart ratio is very useful. Increased lung:heart ratio reflects exercise induced left ventricular dysfunction and is a strong marker of prognosis. Single photon emission computerized tomography (SPECT) offers the potential of more precisely sizing the risk area. The question of whether this technique offers a significant advantage over planar thallium imaging has to be answered.

Left ventricular volume during supine exercise: importance of myocardial scar in patients with coronary heart disease

Existing studies suggest that exercise-induced ischemia produces an increase in left ventricular end-diastolic volume; however, all of these studies have included patients with previous myocardial infarction. To test whether the end-diastolic volume response to exercise is related to the extent of myocardial scar, the results of gated radionuclide supine exercise tests performed on 130 subjects were reviewed. The patient group comprised 130 subjects were reviewed. The patient group comprised 130 men aged 35 to 65 years (mean +/- SD 52 +/- 5) with documented coronary heart disease. The extent of myocardial ischemia and scar formation was assessed by stress electrocardiography and thallium-201 scintigraphy. Patients were classified into three groups on the basis of left ventricular end-diastolic volume response at peak exercise: group 1 (n = 72) had an increase of end-diastolic volume greater than 10%, group 2 (n = 41) had a change in end-diastolic volume less than 10% and group 3 (n = 17) had a decrease in end-diastolic volume greater than 10% (n = 17). At rest there was no significant difference among groups in heart rate, systolic blood pressure, end-diastolic (EDVrest) or end-systolic volumes or ejection fraction (p greater than 0.05); however, at peak exercise the end-systolic volume response was significantly greater for group 1 (p less than 0.002).(ABSTRACT TRUNCATED AT 250 WORDS)

Myocardial perfusion changes following 1 year of exercise training assessed by thallium-201 circumferential count profiles

The effect of exercise training on myocardial perfusion was assessed using initial and 1-year thallium-201 (Tl-201) exercise studies in 56 patients with stable coronary artery disease (CAD). Subjects had been randomized into a trained group participating in supervised exercise three times per week and a control group. Indices (non-dimensional units) based on computer-analyzed circumferential count profile from nine regions of the heart, assessed in three projections, were used to eliminate observer bias and more accurately quantitate Tl-201 distribution and 4-hour washout. There was serial improvement of the global distribution count profiles in 21 of 27 (77.8%) of the trained and in 9 of 29 (31.0%) of the control subjects (p less than 0.001). The mean interval change in global initial distribution over the year period was 5 +/- 13 (mean +/- SD) in the trained and -6 +/- 14 in the control groups (p less than 0.003). The mean initial distribution of the trained group had improvement in all nine regions (significant in three), while the control group showed mean improvement in only one of nine regions. Additionally, the trained group showed improvement in the mean washout in five of nine regions (significant in three), while no mean regional washout improvement occurred in the control group. Thus, in this group of patients with stable CAD, exercise training resulted in apparently improved cardiac perfusion evidenced by enhance Tl-201 uptake and washout.

Regional variability in the myocardial clearance of thallium-201 and its importance in determining the presence or absence of coronary artery disease

There are several limitations in using absolute myocardial clearance of thallium-201 for the detection of coronary artery disease. Noncardiac factors such as peak exercise heart rate and blood level of thallium can affect its absolute myocardial clearance. However, because all myocardial segments in a given heart are exposed to the same noncardiac factors, a relative difference in myocardial clearance of thallium between segments could reflect the presence of coronary artery disease. Accordingly, myocardial clearance of thallium was analyzed in 370 patients. Patients in Group I (n = 45) had less than 1% probability of having coronary artery disease, patients in Group II (n = 44) had normal coronary arteries and patients in Group III (n = 281) had coronary artery disease. Although mean myocardial clearance of thallium in 15 myocardial segments in three views in Group I subjects was 3.4 +/- 0.7 hours, the variability between the slowest and fastest clearing segments in the same subject was as much as 98%. This variability was systematic, suggesting technical reasons associated with imaging as the cause of the variability: 78% of the slowest clearing segments were basal whereas 53% of the fastest clearing segments were apical (p less than 0.01). When Group II and III patients were compared based on Group I values, the absolute myocardial clearance of thallium had a sensitivity and specificity of 92 and 16%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

On the clinical value of thallium-201 washout analysis in the detection of multiple jeopardized myocardial regions

In this study the relative importance of visual assessment and quantitative analysis myocardial stress perfusion scintigraphy in 72 patients with a 40% incidence of triple-vessel coronary disease was tested. The quantitative analysis of the uptake scintigram in combination with a washout rate study of thallium-201 was not superior to the visual analysis with regard to the overall detection of significant coronary disease (obstructions of at least 50%). The sensitivity of the quantitative analysis was 0.85 for the entire population and 0.90 for the triple-vessel disease group (specificity 0.90). Detection of jeopardized myocardial flow regions in patients with triple-vessel disease, however, resulted in a significantly better identification by quantitative analysis. Of the 87 jeopardized flow regions in the 29 patients with triple-vessel disease, 62 regions were detected by the quantitative analysis whereas 48 regions were noted by the visual evaluation. The post-test likelihood of this regional quantitative analysis with respect to the triple-vessel disease was 66%. The incidence of global ischemia as detected by washout abnormalities in cases with no or a maximum of one regional uptake defect was 7%.

Assessment of regional myocardial perfusion with thallium imaging during transient left anterior descending coronary arterial occlusion during angioplasty

To define the jeopardized territory perfused through a single coronary arterial stenosis, thallium-201, 2 mCi, was injected into the pulmonary artery at the onset of the last of a series of percutaneous transluminal coronary angioplasty (PTCA) balloon inflations in 10 patients with single-vessel left anterior descending coronary artery disease. Imaging was begun immediately after PTCA. Arterial thallium activity peaked 30 seconds after injection and decreased to 34 +/- 6% (mean +/- standard error of the mean) of peak activity at the time of balloon deflation. Regional thallium activity during exercise vs PTCA was scored qualitatively and quantitatively. A computer quantification program was used that permitted automatic realignment and normalization of the 2 initial thallium images. Only mean quantitative posterior activity was lower (93 +/- 1% vs 86 +/- 2%, p less than 0.05) on exercise scans compared with PTCA scans. The other 5 segments showed no difference in mean scores. There were no qualitative differences in initial thallium distribution, nor were there qualitative or quantitative differences in the number of abnormal segments or severity of reduction in activity in the segment with the lowest activity. In conclusion, regional thallium myocardial distribution with a single severe stenoses with injection during peak exercise is similar to that after complete coronary occlusion.

Determination of the quantitative thallium imaging variables that optimize detection of coronary artery disease

Although quantification of exercise thallium images has been previously reported, the relative value of different imaging variables for detection of coronary artery disease has not been analyzed in a large group of patients with cardiac catheterization data. Regional initial thallium uptake, redistribution and clearance on thallium study were measured in 325 patients also undergoing cardiac catheterization (281 patients with and 44 patients without coronary artery disease). Normal values were defined in 55 other clinically normal subjects. When five myocardial segments were analyzed in each view, the respective values for sensitivity and specificity were 95 and 50% for initial thallium uptake, 60 and 87% for redistribution and 74 and 66% for clearance. Initial thallium uptake was the most sensitive but least specific (p less than 0.001), whereas redistribution was the least sensitive and most specific (p less than 0.001). Using stepwise logistic regression analysis, the best correlate of coronary artery disease was initial thallium uptake. Addition of redistribution to a mathematical model of the probability of coronary artery disease did not alter sensitivity, but increased specificity from 50 to 70% (p less than 0.001). Once initial uptake and redistribution were considered, myocardial thallium clearance provided no additional improvement in the correlation. Excluding the two basal segments in each view from the analysis increased the specificity from 70 to 80% (p less than 0.001) without affecting sensitivity. Of the 15 patients (5%) with coronary disease not detected using this approach, none had left main disease and 10 (67%) had one vessel disease. A combination of variables derived from quantification of exercise thallium images provides a superior sensitivity and specificity for the detection of coronary artery disease compared with the use of a single variable.

Extent and severity of myocardial hypoperfusion as predictors of prognosis in patients with suspected coronary artery disease

The ability of exercise-induced myocardial hypoperfusion on thallium scintigraphy to predict coronary events was assessed in 1,689 patients with symptoms suggestive of coronary artery disease but without prior myocardial infarction or coronary artery bypass surgery. A total of 74 patients had a coronary event in the year after testing (12 cardiac deaths, 20 nonfatal infarctions and 42 referrals for bypass surgery more than 60 days after testing). Stepwise logistic regression identified only three independent predictors: the number of myocardial regions with reversible hypoperfusion (an index of the extent of hypoperfusion), the maximal magnitude of hypoperfusion (an index of the severity of hypoperfusion) and the achieved heart rate (an index of exercise performance). Both extent and severity were exponentially correlated with event rate (r greater than 0.97 and p less than 0.01 for each), whereas achieved heart rate was linearly correlated with event rate (r = 0.79 and p less than 0.05). On the basis of these data, a prognostic model was defined that employs extent and severity as stress-dependent orthogonal variables. Using this model, the predicted coronary event rate ranged over two orders of magnitude--from a low of 0.4% in patients able to exercise adequately without developing severe and extensive hypoperfusion at a low heart rate (less than 85% of their maximal predicted heart rate). Extent and severity of myocardial hypoperfusion, therefore, are important independent variables of prognosis in patients with suspected coronary artery disease.

Alterations in myocardial metabolism and function at rest in stable angina pectoris: relations with the amount of exercise-induced thallium-201 perfusion defect

The relation between the amount of exercise-induced ischemia and alterations in left ventricular (LV) function and metabolism at rest was studied in 18 coronary patients with stable angina pectoris. An ischemic defect area score was computed from quantitative exercise thallium-201 (Tl-201) scintigraphy; this estimation of the amount of ischemic myocardium was used to classify the patients in group I (n = 8; score less than 15%, mean 6.7 +/- 2.5%) and II (n = 10; score greater than 15%; mean 27.2 +/- 8.9%). Hemodynamics and metabolism were studied in basal state. No patient had anginal pain during the study, and the extent of angiographic coronary artery disease (CAD) was comparable in the two groups. Heart rate, aortic pressure, coronary blood flow, and myocardial oxygen uptake were also similar in both groups. However, ejection fraction was reduced in group II (51 +/- 13 vs 63 +/- 5%; p less than 0.01) and LV relaxation was impaired as shown by the increase in time-constant of isovolumic pressure fall (55 +/- 16 vs 44 +/- 6 ms in group I; p less than 0.05); the LV end-diastolic pressure was also increased in group II (19 +/- 8 vs 10 +/- 4 mmHg in group l; p less than 0.05). Furthermore, in group II, myocardial lactate uptake was reduced (4 +/- 19 vs 30 +/- 29 mumole/min in group I; p less than 0.01) and the productions of alanine and glutamine were augmented (-7.5 +/- 4.4 vs -4.6 +/- 1.6 mumole/min in group I; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of a quantitative treadmill exercise score with standard electrocardiographic criteria in screening asymptomatic young men for coronary artery disease

A computer-derived treadmill exercise score that quantifies the electrocardiographic response to exercise has been reported to have a high sensitivity (87 per cent) and specificity (92 per cent) in patients with a high prevalence of coronary artery disease. To test its accuracy in young, asymptomatic men with a low prevalence of coronary artery disease, we evaluated the responses of 377 military officers (mean age, 36.6 years) by two independent methods. According to standard electrocardiographic criteria, 45 of the subjects (12 per cent) had positive tests, whereas the treadmill exercise score indicated that only 3 (less than 1 per cent) had positive tests. Since two of these three had left ventricular hypertrophy and met only the criteria for the latter without associated coronary artery disease, the treadmill exercise score predicted that only 1 of 377 subjects would have clinically important coronary artery disease. Coronary arteriography, performed in 10 persons with the most positive scores on standard treadmill tests and the highest scores for risk factors, showed that nine subjects did not have coronary artery disease and that one had single-vessel disease (the same subject who the treadmill score predicted would have mild disease). The treadmill exercise score appears to improve the diagnostic specificity of exercise electrocardiography and may be more useful than values on standard stress tests in screening asymptomatic populations for coronary artery disease.

Accuracy of cardiokymography during exercise testing: results of a multicenter study

To determine the diagnostic accuracy of cardiokymography, recorded 2 to 3 minutes after exercise, 617 patients undergoing cardiac catheterization were evaluated from 12 participating centers using a standardized protocol. Adequate cardiokymographic tracings, which were obtained in 82% of patients, were dependent on the skill of the operator and on certain patient characteristics. Of the 327 patients without prior myocardial infarction who had technically adequate cardiokymographic and electrocardiographic tracings, 166 (51%) had coronary disease. Both the sensitivity and specificity of cardiokymography (71 and 88%, respectively) were significantly greater than the values for the exercise electrocardiogram (61 and 76%, respectively, both p less than 0.01). Coronary artery disease and multivessel disease were present in 98 and 68%, respectively, of the 70 patients with concordantly positive cardiokymographic and electrocardiographic results, and in 15 and 5%, respectively, of the 132 patients with concordantly negative test results (p less than 0.001). Cardiokymography was most helpful in those patients in whom the posttest probability of coronary disease was between 21 and 72% after exercise electrocardiography. In these patients a concordantly positive cardiokymographic result increased the probability of coronary disease to between 67 and 100%, whereas a negative response decreased it to between 12 and 15%. In the subgroup of 102 patients undergoing concomitant exercise thallium testing, the sensitivity and specificity for the thallium scintigraphy (81 and 80%, respectively) were similar to the values for cardiokymography (72 and 84%, respectively; differences not significant). Thus, cardiokymography performed during exercise testing improves the diagnostic accuracy of the electrocardiographic response and provides an additional and cost-effective indicator of myocardial ischemia.

Influence of R-wave amplitude on exercise-induced ST depression: need for a "gain factor" correction when interpreting stress electrocardiograms

Does 2 mm of ST depression induced by exercise have the same clinical significance in a patient with a 30-mm R wave as a patient with a 10-mm R wave in the same monitored lead? To answer this question the exercise responses of 85 patients were compared by 2 quantitative methods of assessing myocardial ischemia. A computer-derived treadmill exercise score, based largely on the characteristics of exercise-induced ST-segment depression, was compared with a thallium exercise score. Both scores correlated well over a wide range of values (r = 0.71, p less than 0.001). Then, the treadmill exercise score was corrected (by adjusting the magnitude of the ST depression to a standardized R-wave amplitude of 12 mm in V5 and 8 mm in aVF) to determine if this would improve its correlation with the thallium exercise score. The patients were separated into 2 groups by R-wave amplitude: 53 had an RV5 of 9 to 17 mm and 32 had an RV5 less than 9 or greater than 17 mm. Correction of the treadmill exercise score for R-wave amplitude did not change the slope and intercepts of the regression line for patients with an RV5 amplitude of 9 to 17 mm, but did for those with an RV5 amplitude less than 9 or greater than 17 mm. In this latter group, R-wave correction changed the regression line from one that differed significantly from that of patients with less extreme RV5 voltage to one that was indistinguishable from it. Correction of the treadmill exercise score also increased the correlation coefficient from 0.54 to 0.68 in this group.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical studies with transdermal nitroglycerin

The short- and long-term effects of various Nitro-Dur formulations on performance and hemodynamics were studied in 15 men with stable angina pectoris who also had a positive treadmill exercise test. A treadmill exercise score (TES) was used that quantified the "ischemic" ST segment response to exercise. The score incorporated information that reflected the rapidity of evolution of ST segment depression during exercise and the time required for it to resolve after cessation of exercise. In early tests (n = 10) Nitro-Dur improved both the TES (by 31%: p less than 0.0001) and the time required for 1 mm ST segment depression (by 33%: p less than 0.0001). At all dosage levels, Nitro-Dur also decreased resting systolic blood pressure and increased resting heart rate. No dose-response patterns emerged. Changes in TES and time to ST segment depression were greater with sublingual nitroglycerin than they were with Nitro-Dur. In tests conducted after prolonged dosage (n = 5), the effects of Nitro-Dur on blood pressure and heart rate became attenuated at weeks 2 and 4, although cardiac responsiveness was preserved, as reflected in the increased time required before the occurrence of 1 mm ST segment depression. The latter effect was also observed with sublingual nitroglycerin. The clinical relevance of these data to the design of individual patient therapy is discussed.

Detection and quantification of previous myocardial infarction by exercise-redistribution tomographic thallium-201 scintigraphy

Although myocardial perfusion scintigraphy at rest accurately diagnoses myocardial infarction (MI), the prevalence and size of previous MI is overestimated by exercise-redistribution thallium-201 studies. A new, quantitative approach to the analysis of tomographic thallium-201 scintigrams was developed in order to determine whether the presence and extent of MI could be determined. Sixty patients undergoing cardiac catheterization for chest pain syndromes, including 28 with previous MI, were studied by exercise and 3-hour delayed thallium-201 scintigraphy, with use of the 7-pinhole tomographic technique. Circumferential profiles of the postexercise and 3-hour radiotracer distribution were generated from apical, midventricular and basal left ventricular slices. The 3-hour profile fell below normal limits in 24 of 28 patients (86%) with remote MI, but was also abnormal in 9 of 22 patients (41%) with coronary disease but no MI. All missed MIs were either inferior or subendocardial and were associated with normal ejection fractions. To distinguish between MI and slowly resolving ischemic defects, a quantitative approach was used. MI area was calculated as the area in which the 3-hour profile fell below the 3-hour normal limits, and a redistribution area in the MI zone was determined as the area between the postexercise and 3-hour profiles in the region where the 3-hour profile was abnormal. The MI area was 1,000 +/- 980 units in patients with MI, vs 79 +/- 120 units in patients without MI (p less than 0.001), whereas the redistribution area was higher in patients without MI (1,240 +/- 810 vs 430 +/- 400 units, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)