Spatial R wave amplitude changes during exercise: relation with left ventricular ischemia and function

Thirty patients who exhibited increased and 65 patients decreased spatial R wave amplitude during exercise testing were compared for left ventricular function and ischemic variables. Spatial R wave amplitude was derived from the three-dimensional Frank X, Y, Z leads using computerized methods. All patients had stable coronary artery disease and they were classified into two groups: one that attained a higher (n = 48) and one a lower (n = 47) median value of maximal heart rate during exercise (161 beats/min). Within these two groups, patients with increasing or decreasing spatial R wave amplitude during exercise were analyzed for differences in oxygen consumption, exercise-induced changes in spatial R wave amplitude, ST segment depression laterally (ST60, lead X), ST displacement spatially, left ventricular ejection fraction at rest, change in left ventricular ejection fraction with exercise and thallium-201 ischemia during exercise. Significant differences were demonstrated only in exercise-induced spatial R wave amplitude changes (p less than 0.0001). There was no significant correlation between exercise-induced change in heart rate and change in spatial R wave amplitude in either the group with increasing or the group with decreasing spatial R wave amplitude. It is concluded that changes in spatial R wave amplitude during exercise are not related to ischemic electrocardiographic or thallium-201 imaging changes or to left ventricular ejection fraction determined at rest or during exercise.     

Thallium-201 myocardial imaging in young asymptomatic subjects with "ischaemic" changes in exercise electrocardiogram.

In order to assess the significance of a positive electrocardiographic response to exercise test in 10 asymptomatic subjects with normal resting ECG, a myocardial perfusion scanning with Thallium-201 at rest and during exercise was performed. The following ECG tests were also performed on these subjects: forced hyperventilation, exercise test after nitroglycerin (TNG), exercise test after propranolol. Myocardial perfusion scans did not reveal any defect at rest nor during exercise. Hyperventilation determined abnormalities of ventricular repolarization in all subjects. TNG did not improve the response to exercise test and even decreased the ischemic threshold. After propranolol the electrocardiographic response to exercise became normal in 9 cases, while in 1 subject the ST depressions were impressively reduced. All subjects had a follow-up of 14 to 91 months. During this period none presented symptoms suggesting a coronary disease. This study suggests that combined evaluation of Thallium myocardial perfusion imaging during exercise and exercise ECG test after TNG is most useful in differentiating ischemic from nonischemic exercise ST depressions in asymptomatic population.     

The diagnostic value of bloodless methods and follow-up in young asymptomatic subjects with positive exercise test (author's transl)]

Fifty asymptomatic subjects, aged 22 to 40, with normal resting ECG and "ischemic" ST depressions during exercise were followed for 44 +/- 18 months. Coronary events occurred only in two cases. Unexpectedly in 12 subjects the response to maximal exercise became normal. In 25 subjects forced hyperventilation, exercise test after nitroglycerin (TNG), and after propranolol (P) were performed. Hyperventilation determined abnormalities of ventricular recovery in all cases. TNG did not improve the response to exercise, as it does in coronary patients, and even significantly decreased the "ischemic threshold"; after P the exercise test became normal in 20 subjects, while in 5 the electrocardiographic ST depressions were markedly reduced. The responses to pharmacological tests after the follow-up period were similar to the first observation. In 8 subjects, in which exercise ST depressions were particularly impressive, Tallium 201 myocardial scanning at rest and during exercise was performed. Myocardial perfusion imaging did not reveal any defect, thus confirming the non-ischemic nature of the ECG abnormalities. Our results confirm the low predictive accuracy (4%) of a positive stress test in a young asymptomatic population and suggest that, among non-invasive methods, exercise response after TNG is usefull in recognizing the "false positive" tests.     

Myocardial metabolic, hemodynamic, and electrocardiographic significance of reversible thallium-201 abnormalities in hypertrophic cardiomyopathy

BACKGROUND. Exercise-induced abnormalities during thallium-201 scintigraphy that normalize at rest frequently occur in patients with hypertrophic cardiomyopathy. However, it is not known whether these abnormalities are indicative of myocardial ischemia. METHODS AND RESULTS. Fifty patients with hypertrophic cardiomyopathy underwent exercise 201Tl scintigraphy and, during the same week, measurement of myocardial lactate metabolism and hemodynamics during pacing stress. Thirty-seven patients (74%) had one or more 201Tl abnormalities that completely normalized after 3 hours of rest; 26 had regional myocardial 201Tl defects, and 26 had apparent left ventricular cavity dilatation with exercise, with 15 having coexistence of these abnormal findings. Of the 37 patients with reversible 201Tl abnormalities, 27 (73%) had metabolic evidence of myocardial ischemia during rapid atrial pacing (myocardial lactate extraction of 0 mmol/l or less) compared with four of 13 patients (31%) with normal 201Tl scans (p less than 0.01). Eleven patients had apparent cavity dilatation as their only 201Tl abnormality; their mean postpacing left ventricular end-diastolic pressure was significantly higher than that of the 13 patients with normal 201Tl studies (33 +/- 5 versus 21 +/- 10 mm Hg, p less than 0.001). There was no correlation between the angiographic presence of systolic septal or epicardial coronary arterial compression and the presence or distribution of 201Tl abnormalities. Patients with ischemic ST segment responses to exercise had an 80% prevalence rate of reversible 201Tl abnormalities and a 70% prevalence rate of pacing-induced ischemia. However, 69% of patients with nonischemic ST segment responses had reversible 201Tl abnormalities, and 55% had pacing-induced ischemia. CONCLUSIONS. Reversible 201Tl abnormalities during exercise stress are markers of myocardial ischemia in hypertrophic cardiomyopathy and most likely identify relatively underperfused myocardium. In contrast, ST segment changes with exercise and systolic compression of coronary arteries on angiography are unreliable markers of inducible myocardial ischemia in hypertrophic cardiomyopathy. Apparent cavity dilatation during 201Tl scintigraphy may indicate ischemia-related changes in left ventricular filling, with elevation in diastolic pressures and endocardial compression.     

Regional myocardial dysfunction in patients with angina at rest and response to isosorbide dinitrate assessed by phase analysis of radionuclide ventriculograms

Left and right ventricular synchrony was assessed in 15 patients with angina at rest but no previous infarction by phase analysis of equilibrium radionuclide ventriculograms. Transient thallium-201 perfusion defects were noted in all during angina at rest and coronary vasospasm was documented in nine of the patients. Radionuclide ventriculograms were performed at control, during the ischemic episodes and after intravenous isosorbide dinitrate. Left and right ventricular phase histograms were quantified by the standard deviation from the mean of the peak (SD). Left ventricular ejection fraction averaged 65 +/- 11% (mean +/- standard deviation) at control, decreased in all patients during angina at rest to 49 +/- 14% (p less than 0.01) and increased in all patients after isosorbide dinitrate to 66 +/- 12%. However, ejection fraction during ischemia was abnormal in only nine patients and changed in two by less than 5% from the control value. Regional wall motion abnormalities were noted in all patients during the ischemic episodes but resolved after isosorbide dinitrate administration. Control left ventricular SD was 14.5 +/- 4 degrees, increased in all patients to 22.8 +/- 5 degrees during angina at rest (p less than 0.01) and returned to control values after isosorbide dinitrate administration (14.2 +/- 4 degrees). In contrast, right ventricular SD did not significantly change during ischemia as compared with control and isosorbide dinitrate. It is concluded that in angina at rest, a normal left ventricular ejection fraction does not exclude severe regional dysfunction; separate left and right ventricular SD is a sensitive index in detecting transient left ventricular dysfunction, and relief of ischemia is associated with rapid normalization of regional left ventricular function.     

Regional distribution and extent of perfusion abnormalities, and the lung to heart uptake ratios during exercise thallium-201 SPECT imaging in patients with cardiac syndrome X

BACKGROUND: Cardiac syndrome X is defined as angina-like chest pain with transient ischemic ST-segment changes during exercise and angiographically normal epicardial coronary arteries. Studies with myocardial perfusion imaging in this syndrome have indicated that some patients, but not all, have an abnormality on perfusion scan. However, the impact of these perfusion abnormalities on pulmonary thallium uptake is not clear in this group of patients. OBJECTIVE: To evaluate the regional distribution and extent of perfusion abnormalities, and the lung to heart (L:H) uptake ratios using exercise thallium-201 single-photon emission computed tomography (TI-201 SPECT) in patients with cardiac syndrome X. METHODS: The study group consisted of 31 selected cardiac syndrome X patients with regional perfusion abnormalities during exercise TI-201 SPECT imaging. A control group included 26 healthy subjects with normal coronary angiograms, exercise testing and exercise TI-201 SPECT imaging. Exercise TI-201 SPECT results were analyzed with further estimation of the L:H ratios, number and localization of regional perfusion defects, and their mean extent scores expressed in pixels and in per cent of the left ventricular wall. Twenty-two patients with known coronary artery disease were also included in the analysis of the L:H ratios. RESULTS: Multiple perfusion defects were detected in 13 (42%) patients and perfusion defects of single localization were detected 18 (58%) patients. All patients had reversible perfusion abnormalities: 21 (67.7%) had anterior, 14 (45.2%) had inferior and 12 (38.7%) had lateral localization of perfusion defects. The analysis of the extent of the perfusion defects revealed that the mean scores of the extent of the single regional defects were 38.61+/-43.8 pixels and those of multiregional defects were 106.1+/-55.2 pixels, which corresponded to 6.05+/-1.8% and 16.6+/-5.4% of the left ventricular wall defects, respectively. Patients with cardiac syndrome X had a significantly higher L:H ratio during exercise than the healthy subjects (0.46+/-0.02 versus 0.34+/-0.03, P<0.01). In addition, L:H ratios were found to be higher in patients with multiple perfusion defects (0.50+/-0.02) than in patients who had only anterior (0.45+/-0.08) or inferior (0.43+/-0.02) perfusion defects (P<0.05 for both). There were no statistically significant differences in the rest L:H ratios between the study and control groups. Also, no significant differences were observed in exercise L:H ratios between the cardiac syndrome X patients and the patients with coronary artery disease (0.46+/-0.02 versus 0.49+/-0.03, P>0.05). CONCLUSIONS: The results suggest that multiple perfusion defects in multiple vascular regions are relatively common in cardiac syndrome X patients, with the majority of these patients having at least one abnormal perfusion bed. Patients with this syndrome who have perfusion abnormalities also had significantly higher L:H ratios during exercise than did the control patients. Increased exercise L:H ratios were more prominent in patients with multiple perfusion defects.     

Beta-methyl-15-P-[123I] iodophenyl-pentadecanoic acid and thallium-201 in the assessment of myocardial perfusion defects

The purpose of this investigation was to examine the ability of beta-methyl-15-P-[123I]-iodophenyl-pentadecanoic acid (beta 123IPPA) and thallium-201 to assess the ischemic risk zone associated with myocardial infarction. The hearts of mongrel dogs were infarcted by ligating the left anterior descending coronary artery and at 6 h post infarction injected with thallium-201 (2 mCi; scanning time 30 mins) followed by beta 123IPPA (3 to 5 mCi; scanning time 30 mins). Scintigraphic assessment of the perfusion defect yielded perfusion defect size (percentage of whole slice), which was then compared to the defect when assessed by tetrazolium staining. Myocardial ratios were calculated to assess differences in localization between tracers. Any differences noted may affect identification of the area at risk following acute myocardial infarction. A slice-by-slice comparison of perfusion defect size for scintigraphic methods and histochemical method showed no significant difference between beta 123IPPA and thallium-201. The mean ratio for myocardial defect size expressed as beta 123IPPA/thallium-201 was 1.03 +/- 1.29. Enzymatic analysis demonstrated significant increases in creatine kinase (160.33 +/- 46.44 to 5030.6 +/- 2238 U) and creatine kinase-MB% (31.85 +/- 15.11 to 82.99 +/- 8.14%) post infarction (P less than 0.05 in both cases). Elevated ST segments were also seen in all dogs post infarction. It can be concluded that the combined use of beta 123IPPA and thallium-201 does not allow the identification of the ischemic risk zone (percentage area at risk) often associated with myocardial perfusion defects. Problems continue to exist with image resolution and border demarcation.     

Simultaneous measurement of left ventricular function and myocardial perfusion during a single exercise test: dual isotope imaging with gold-195 m and thallium-201

The state of left ventricular function and myocardial perfusionare important determinants of prognosis in patients with coronaryartery disease and information on both can be valuable for planningindividual patient management. We have studied the feasibilityof simultaneous measurement of left ventricular ejection fractionwith ultra short-lived gold-195 m (half life 30.5 seconds) andmyocardial perfusion with thallium-201, at rest and after exercisewith a single-crystal gamma camera. The results with first-passradionuclide angiocardiography (RNA) using gold-195 m at restwere reproducible and agreed closely with the results obtainedusing technetium-99 m equilibrium radionuclide angiocardiography(r = 0.93). Ejection fraction by firstpass gold-195 m RNA duringsemi-supine ergometric exercise decreased by >5% in 13 outof 18patients with coronary artery disease and stable angina.Simultaneous myocardial imaging with thallium-201 was abnormalin all patients. The change in regional wall motion abnormalityscore during exercise correlated with the change in myocardialperfusion (r = 0.71, P<0.01) and with the change in globalleft ventricular ejection fraction (r = 0.77, P<0.001). Thewidely differing energy levels and half-lives of gold-195 mand thallium-201 made it possible to separate clearly the imagesdue to each radionuclide. This study has demonstrated the feasibilityof simultaneous or sequential assessment of left ventricularfunction and myocardial perfusion during a single exercise test,a technique which can offer advantages in clinical evaluationof patients with coronary artery disease.     

Improved myocardial ischemia and left ventricular function during exercise after successful percutaneous transluminal coronary angioplasty

Percutaneous transluminal coronary angioplasty (PTCA) was performed in 42 patients with effort angina, 28 (67%) of them underwent successful angioplasty. Treadmill exercise testing, thallium-201 myocardial scintigraphy and radionuclide ventriculography were performed before and after PTCA for evaluation of the improvement of myocardial ischemia and left ventricular function at rest and during exercise. The average exercise duration by treadmill testing in 14 successful cases increased from 14 +/- 4 (mean +/- S.D.) to 16 +/- 2 minutes (p less than 0.05). Sixteen of 28 the patients were studied by thallium-201 myocardial scintigraphy. Before PTCA, regions of decreased thallium-201 uptake after exercise were observed in 12 of the 16 patients. After angioplasty, no distinct defects were recognizable in 9 of the 12 patients, and in the remaining three, a significant decrease in defects was recognized. Fifteen of the 28 patients were studied by radionuclide ventriculography. The mean ejection fraction was 61 +/- 5% at rest and 56 +/- 11% during exercise (N.S.) before PTCA. After angioplasty, the ejection fraction was unchanged at rest (61 +/- 5 to 62 +/- 4%), but increased significantly during exercise (62 +/- 4 to 74 +/- 4%, p less than 0.001). In conclusion, left ventricular function was improved by successful PTCA due to improvement of myocardial ischemia. The long term results require further study.     

Exercise-induced ST-segment depression: imbalance between myocardial oxygen demand and myocardial blood flow

OBJECTIVE: ST-segment depression is believed as a common electrocardiographic sign of myocardial ischemia during exercise testing. Ischemia is generally defined as oxygen deprivation due to reduced perfusion. However, the exact relationship of the ischemic definition to ST-segment depression remains unclear. This study was conducted to evaluate the correlation between myocardial oxygen demand and myocardial blood flow (MBF) when ischemic (horizontal or downsloping) ST-segment depression of > or = 0.1 mV 80 ms after the J point developed during low-level exercise. METHODS AND RESULTS: Seventy-two patients with angiographically proven coronary artery disease (CAD) and 9 healthy volunteers underwent exercise positron emission tomography (PET). Myocardial oxygen demand was defined as a rate-pressure product (RPP, heart rate x systolic blood pressure) during exercise and MBF was quantified by nitrogen-13 ammonia perfusion PET. The myocardial demand-supply balance (MDSB) index was calculated from the MBF ratio (values during exercise/values at rest) against the RPP ratio (values during exercise/values at rest). The MDSB index was significantly lower in patients with ischemic ST-segment depression than in patients with non-ischemic ST depression and healthy volunteers (0.82 +/- 0.16 vs. 1.02 +/- 0.17, p < 0.0001 and vs. 0.99 +/- 0.14, p = 0.0109). Further, the presence of inadequate increase in MBF of < or = 10% (2 SD below the mean % value of healthy volunteers) during exercise in regional myocardium perfused by stenotic CAD significantly correlated with exercise-induced ischemic ST-segment depression (p = 0.0105). CONCLUSIONS: Our study could demonstrate that exercise-induced ischemic ST-segment depression is associated with myocardial ischemia due to exercise-induced imbalance between myocardial oxygen demand and global and regional MBF supply in patients with proven CAD.     

Regional myocardial perfusion and function after coronary bypass surgery: evaluation using handgrip exercise Doppler echocardiography]

To evaluate myocardial perfusion and function of the interventricular septum after coronary artery bypass surgery, 29 patients with internal mammary artery grafts (IMAG) were examined using handgrip exercise Doppler echocardiography. IMAG flow was measured by color flow Doppler. Septal excursion and percent thickening of the interventricular septum during systole were measured as indicators of regional left ventricular function by M-mode echocardiography. Myocardial perfusion was estimated by thallium-201 exercise myocardial scintigraphy using a treadmill. 1. At rest, there were no significant correlations between IMAG flow and septal excursion and percent thickening or myocardial perfusion. 2. After the isometric handgrip exercise test, IMAG flow increased 20.0 +/- 3.9% from at rest, and the percentage of change in IMAG flow correlated significantly with changes in septal excursion (r = 0.63) and percent thickening (r = 0.72). It was found that a response of bypass graft flow to exercise has a correlation with contractility of cardiac muscle. 3. The rate of increase in IMAG flow in patients with normal myocardial scintigraphic findings (31.8 +/- 6.2%) was higher than that in patients with ischemia (15.3 +/- 5.6%) or infarction (15.0 +/- 11.3%). 4. A greater increase of percent thickening was observed in patients with normal exercise myocardial scintigraphic findings. These results suggest that the responses of the bypass graft flow to handgrip exercise may reflect viability and contractility of cardiac muscles perfused by the graft. Thus, exercise Doppler echocardiography is useful for evaluating regional myocardial perfusion and function of the interventricular septum after coronary artery bypass surgery.     

Systolic and diastolic left ventricular dysfunction in middle-aged asymptomatic non-insulin-dependent diabetics.

Radionuclide ventriculographic studies were performed at rest and during exercise in 15 middle-aged asymptomatic patients with non-insulin-dependent diabetes mellitus (NIDDM) whose mean age was 58.7 +/- 10.5 years (mean +/- SD), and in 10 age- and sex-matched normal control subjects. The patients had neither clinical evidence of cardiovascular diseases nor obvious perfusion defects during maximal exercise testing with thallium-201 myocardial scintigraphy. The average left ventricular ejection fraction (LVEF) at rest was 69.1 +/- 5.3% in the diabetic patients and 65.6 +/- 4.2% in the control subjects, and during exercise, the average LVEFs were 68.3 +/- 6.9% and 72.1 +/- 5.0%, respectively. The changes in LVEF during exercise were -0.7 +/- 7.6% in the diabetic group and +6.5 +/- 2.6% in the control group (p < 0.01). However, the filling fraction during the first third of diastole at rest was significantly less in the diabetic group than in the control group (p < 0.05), the time to peak filling rate (TPF) was longer, and the TPF/R-R, normalized by the R-R interval and expressed as a percentage, was greater in the NIDDM patients than in the control subjects. There was close correlation between the abnormal response of LVEF to exercise and the reduced early diastolic filling in the diabetic patients. We concluded that 1) not only the response of LVEF to exercise but also the early left ventricular diastolic filling at rest are impaired in middle-aged asymptomatic NIDDM patients, and 2) some common factors could cause dysfunction of both the systolic and diastolic left ventricles in NIDDM patients, possibly latent global myocardial ischemia or metabolic myocardial disturbances.     

Myocardial perfusion after aortic implantation for anomalous origin of the left coronary artery from the pulmonary artery

Postoperative myocardial perfusion and function were evaluated using thallium-201 myocardial imaging and technetium-99m cardiac pool imaging in five patients with an anomalous left coronary artery arising from the pulmonary artery. The patients underwent reimplantation of the left coronary artery at an age ranging from 10 months to 13 years. Postoperative electrocardiographic and radionuclide studies were performed both at rest and during stress 1 to 4 years after the operation. Electrocardiograms which were abnormal preoperatively returned to normal after surgery except that the T wave in lead aVL remained negative. Postoperatively, left ventricular ejection fraction measured by technetium-99m cardiac pool imaging was normal in all patients. Postoperative thallium-201 myocardial imaging, however, showed a perfusion defect with incomplete redistribution at the high-lateral or antero-lateral segment in all patients after a stress test. These data suggest that although myocardial ischaemic change decreases and global cardiac function improves after establishment of a dual coronary artery system, severe myocardial damage remains at the high-lateral or antero-lateral segment.     

Effect of rate-dependent left bundle branch block on global and regional left ventricular function

Seven subjects with rate-dependent left bundle branch block (RDLBBB) and 13 subjects with normal conduction (control group) underwent upright bicycle exercise radionuclide angiography to determine the effects of the development of RDLBBB on global and regional left ventricular function. Six of the seven subjects with RDLBBB had atypical chest pain syndromes; none had evidence of cardiac disease based on clinical examination and either normal cardiac catheterization or exercise thallium-201 scintigraphy. Radionuclide angiograms were recorded at rest and immediately before and after RDLBBB in the test group, and at rest and during intermediate and maximal exercise in the control group. The development of RDLBBB was associated with an abrupt decrease in left ventricular ejection fraction (LVEF) in six of seven patients (mean decrease 6 +/- 5%) and no overall increase in LVEF between rest and maximal exercise (65 +/- 9% and 65 +/- 12%, respectively). In contrast, LVEF in the control group was 62 +/- 8% at rest and increased to 72 +/- 8% at intermediate and 78 +/- 7% at maximal exercise. The onset of RDLBBB was associated with the development of asynchronous left ventricular contraction in each patient and hypokinesis in four of seven patients. All patients in the control group had normal wall motion at rest and exercise. These data indicate that the development of RDLBBB is associated with changes in global and regional ventricular function that may be confused with development of left ventricular ischemia during exercise.     

Spontaneous changes in thallium-201 myocardial perfusion imaging after myocardial infarction

To examine regional myocardial perfusion after myocardial infarction, 26 patients underwent exercise electrocardiographic testing with thallium-201 myocardial perfusion imaging 3 weeks and 3 months after infarction. At 3 weeks, 9 of 26 patients (35%) had myocardial ischemia by exercise electrocardiographic testing, whereas 18 of 26 (69%) had ischemia by thallium-201 imaging. The thallium-201 scintigrams were scored by dividing each image, in 3 views, into 5 segments, using a 5-point scoring scheme. The exercise thallium-201 score was 44.3 ± 1.2 and increased to 47.3 ± 1.2 in the redistribution study (p < 0.001). Three months after infarction, although there was a significantly greater rate-pressure product which would predict a larger ischemic defect and a decrease in the stress thallium-201 score, the stress score was improved (48.3 ± 1.1, p < 0.001). The redistribution score was similar, that is, 48.9 ± 1.0. The improvement in thallium-201 myocardial perfusion was associated with a loss of stress-induced ischemia in 8 patients (30%). These results indicate that spontaneous improvements in thallium-201 myocardial perfusion imaging may occur after myocardial infarction.     

Influence of exercise training soon after myocardial infarction on regional myocardial perfusion and resting left ventricular function.

There is scant information regarding the effect of exercise training begun soon after hospital discharge for myocardial infarction (MI) with respect to subsequent improvement in exercise tolerance, enhancement of regional myocardial perfusion, or left ventricular function. Accordingly, 19 post-MI patients (mean age 53 +/- 7 years) underwent treadmill exercise quantitative thallium-201 (Tl-201) scintigraphy and rest radionuclide angiography (RNA) prior to and after 12 weeks of thrice-weekly exercise training which was targeted to 70-85% of maximum exercise heart rate achieved. Training was begun at 25 +/- 3 days after hospital discharge. Eight Tl-201 scan segments were each scored from 1-6 points based upon uptake and washout criteria with 6 being the most severe defect (greater than 50% reduction in Tl-201 events with no delayed redistribution). When matched to the pretraining peak workload on exercise testing, 12 weeks of training significantly lessened heart rate (120 +/- 4 to 97 +/- 4, p less than 0.001), peak systolic blood pressure (142 +/- 6 to 129 +/- 5 mmHg, p less than 0.01), and significantly reduced double product [17.2 +/- 10.8 to 12.7 +/- 9 (x10(3), p less than 0.001]. Training was associated with a reduction of exercise-induced ST depression or angina (42 to 16%) which was not statistically significant. The mean resting by RNA ejection fraction was 50 +/- 3% prior to training and 51 +/- 3% after training. There was no significant change in overall Tl-201 defect score or the number of defect regions per patient scan comparing pre- and post-training scintigrams.(ABSTRACT TRUNCATED AT 250 WORDS)     

Iodine-123 phenylpentadecanoic acid myocardial scintigraphy in patients with left ventricular hypertrophy: alterations in left ventricular distribution and utilization

Regional alterations in myocardial substrate uptake and/or utilization have been demonstrated in rats with hypertension. To determine whether alterations in left ventricular fatty acid uptake and/or utilization are present in patients with left ventricular hypertrophy (LVH), we compared the results of rest and exercise iodine-123 phenylpentadecanoic acid (IPPA) myocardial scintigraphy in 10 patients with hypertension who had concentric LVH without evidence of coronary artery disease and in 15 normal subjects. Patients with LVH had more heterogeneous left ventricular activity of IPPA compared to normal subjects after exercise but not at rest (23 +/- 8% versus 13 +/- 5% difference in maximum segmental activity at 4 minutes after exercise; p = 0.005). Although IPPA clearance was similar in both patients with LVH and normal subjects, postexercise washout in segments showing decreased initial IPPA uptake was reduced compared to washout at rest in patients with LVH (11.7 +/- 7.5% versus 21.5 +/- 8.4% at 20 minutes after injection, n = 15; p = 0.005). Exercise thallium-201 (TI-201) scintigraphy was normal in all seven patients with LVH tested. Patients with LVH showed significantly greater heterogeneity in IPPA uptake compared to TI-201 uptake immediately after exercise (25 +/- 5% versus 16 +/- 6%; p = 0.013). We conclude that (1) compared to normal subjects, patients with LVH show heterogeneous myocardial IPPA activity after exercise but not at rest; (2) postexercise washout of IPPA was decreased in segments with reduced uptake after exercise in patients with LVH; and (3) the distribution of IPPA is more heterogeneous than that of TI-201 immediately after exercise in patients with concentric LVH. The postexercise heterogeneity in IPPA uptake and delayed washout in segments with reduced initial uptake is consistent with exercise-induced myocardial ischemia in patients with LVH.     

Role of beta-endorphins in silent myocardial ischemia

The reason for the absence of pain perception in silent myocardial ischemia is unknown. A role of increased endorphinic activity in patients with silent ischemia has been postulated. To further investigate this hypothesis, 10 men with documented coronary artery disease and previous positive electrocardiographic findings during exercise without anginal pain were studied. Six healthy volunteers served as control subjects. The protocol included 2 bicycle exercise tests, the first test serving as baseline and the second performed after administration of naloxone, a specific opiate antagonist. Plasma beta-endorphin levels were measured by radioimmunoassay in both tests at rest, at peak exercise level and after recovery. All patients underwent thallium-201 scintigraphy after coronary vasodilation to provide an additional independent marker of ischemia. All patients showed stress-induced reversible perfusion abnormalities. No patient reported pain after naloxone application. Exercise duration, blood pressure and heart rate were not significantly altered by naloxone. Plasma beta-endorphin levels ranged from 18 +/- 6 pg/100 microliters (mean +/- standard deviation) at rest to 22 +/- 6 pg/100 microliters during exercise in the patient group and from 20 +/- 5 to 27 +/- 9 pg/100 microliters in the control subjects. Thus, there was no significant increase of plasma beta-endorphins during exercise or after naloxone administration, nor was there any difference observed between patients and control group. These data support the view that endorphinic activity does not play an essential role in the pathophysiology of silent myocardial ischemia.     

Mechanism underlying the absence of ischemic changes on the exercise electrocardiogram in patients with abnormal exercise thallium-201 imaging and coronary artery disease

Patients with coronary artery disease may have reversible abnormalities on a thallium myocardial perfusion study without simultaneous ischemic changes on the exercise electrocardiogram, but the mechanisms responsible for this disparity have not been fully elucidated. A group of 37 patients with angiographically demonstrated coronary artery disease and abnormal thallium perfusion imaging were divided into two groups on the basis of their exercise electrocardiographic ST segment response. Thirteen patients (Group A) had no significant electrocardiographic changes with exercise, while 24 patients (Group B) had ST changes consistent with ischemia during the test. There were no significant differences in clinical or angiographic characteristics between the two groups. Stress test results showed a similar mean duration of exercise in the two groups (6.2 +/- 1.8 versus 6.7 +/- 2.5 min, p = NS), but the patients in Group A achieved a significantly lower mean maximal heart rate (117 +/- 26 versus 132 +/- 21 beats/min, p less than 0.05) and mean maximal double product (19,650 +/- 5116 versus 22,650 +/- 4871, p less than 0.05). There was no consistent pattern of thallium perfusion abnormality noted in Group A to suggest that a particular region of electrically silent myocardium was responsible for ischemia in the absence of electrocardiographic changes. These results suggest that exercise thallium-electrocardiogram discordance is mediated by the level of myocardial workload achieved. An abnormal perfusion scan accompanying an exercise electrocardiogram which does not demonstrate any ischemic ST change may occur when there is sufficient increase in myocardial oxygen demand to result in differential augmentation of myocardial blood flow, but insufficient imbalance of supply and demand to result in signs of ischemia on the surface electrocardiogram.     

Evidence of impaired myocardial perfusion and abnormal left ventricular function during exercise in patients with isolated systolic narrowing of the left anterior descending coronary artery

Seven men ranging in age from 35 to 63 years with a chest pain syndrome and cineangiographically documented systolic narrowing of the left anterior descending coronary artery underwent thallium-201 myocardial scintigraphy and gated cardiac blood pool imaging. Grade II (50 to 75 percent) systolic coronary arterial constriction was present in three patients and grade III constriction (greater than 75 percent) in four. Three of the four patients with grade III constriction had an exercise-induced perfusion abnormality in the thallium-201 scintigram and an impaired left ventricular ejection fraction response during exercise. (In two patients the left ventricular ejection fraction did not change and in one patient it decreased.) Each of the three patients with grade II constriction had normal thallium-201 perfusion and a normal increase in ejection fraction during exercise. These data provide evidence of abnormal myocardial perfusion and impaired left ventricular function during exercise in patients with high grade systolic coronary arterial narrowing.