Can myocardial ischemia be recognized by the exercise electrocardiogram in coronary disease patients with abnormal resting Q waves?

This study was performed in order to determine whether exercise-induced myocardial ischemia demonstrated by thallium-201 imaging could be detected by ST segment shifts in patients with abnormal Q waves at rest. Fifty-four patients with coronary artery disease and exercise-induced thallium-201 defects were compared to 22 patients with similar Q wave patterns but without thallium-201 exercise defects and to 14 normal subjects. Exercise data were analyzed visually in the 12-lead ECG and for spatial ST vector shifts. Both ST segment depression observed on the 12-lead ECG and spatial criteria were reasonably sensitive and specific for ischemia when the resting ECG showed no Q waves or inferior Q waves (range 69% to 93%). However, when anterior Q waves were present, ST segment shifts could not distinguish patients with ischemia from those with normal perfusion as determined by thallium imaging.     

Silent myocardial ischemia in patients with essential hypertension]

Holter monitoring was performed in 61 patients with essential hypertension. Painless, silent ST segment depression was found in 34 patients. Exercise myocardial scintigraphy indicated the occurrence of transient perfusion defects without abnormal clearance (Group 1) and those with abnormal clearance (Group 2). The patients from Group 1 showed more severe myocardial hypertrophy, higher platelet aggregation, coronary atherosclerosis was detected in 1 case. The patients from Group 2 exhibited less myocardial hypertrophy, lower platelet aggregation. Coronary atherosclerosis was revealed in 4 cases. The patients from the two groups had elevated plasma norepinephrine levels at the onset of silent myocardial ischemia.     

Comparison of Holter electrocardiography and thallium 201 scintigraphy in the detection of myocardial ischemia

OBJECTIVE OF THE STUDY: To compare ischemic changes (I) detected by Holter ECG (H ECG) to the myocardial perfusion defects found in 201 TI myocardial perfusion scintigraphy. DESIGN: 201 TI exercise test was made during the performance of a 24 hours H ECG. The validation of ST segment changes detected by H ECG during the exercise test was made on basis of reversible myocardial perfusion defects (RPD) detected on 201 TL and a relation between ST segment changes detected during the remaining 24 hours recording period and 201 TI (TI) RPD was established. SETTING: The patients (pt) included in the study have come from Cardiology and Heart Surgery Clinics of a Central teaching hospital. MATERIAL AND METHODS: 20 pt with a high coronary artery disease prevalence have been submitted to a two lead (V5 and aVF) 24 hour H ECG during which they have performed a symptom limited bicycle exercise test followed by an injection of 201 TI with acquisition 5 minutes later. Ischemic episodes detected on H ECG were quantified and their relation with heart rate and symptoms was established. As far as 201 TI studies are concerned the fixed and reversible perfusion defects as well as their location were evaluated. RESULTS: 1. H ECG: 6 pt (30%) presented ST changes on H ECG during the exercise test and a total of 9 pt (45%) had ST changes during exercise and during the remaining period of H ECG. 2. TI: 19 pt presented perfusion defects images (fixed in 7, reversible in 14, both kinds of defects in 7). 3. H ECG validation: H ECG during exercise presented I in 6 out of 14 pt with RPD on TI (sensitivity = 43%). Six of these 8 pt, with negative H and positive TI, had a chronic myocardial infarction. All the 6 pt with negative TI had negative H ECG (specificity = 100%). 4. H ECG TI comparison: 7 (50%) of the 14 pt with RPD had ST changes on 24 hrs H ECG. Seven of 11 pt with negative H ECG had RPD in TI. Two pt with negative TI had positive H ECG. These 2 pt had during H ECG a higher heart rate (HR) than the HR recorded during the exercise test. CONCLUSIONS: 1. In pt with known CAD, TI has a high sensitivity and specificity to show perfusion defects. 2. Considering TI as gold standard, H ECG showed to be a useful method to detect I in the studied population (sens. = 43%; spec. = 100%). 3. H ECG revealed to be an important diagnostic tool in detecting additional I episodes beyond the ones recorded during TI exercise test.     

Diagnosis of chronic coronary failure by clinical aspects, ECG and myocardial scintigraphy after infusion of isoprenaline. Comparison with coronarography

The purpose of this study was to assess the ability of isoproterenol (IPNA) to provoke chest pain, electrocardiographic (ECG) changes and transient defects on thallium 201 myocardial scintigraphy for coronary artery disease (CAD) diagnosis. Thirty patients without prior myocardial infarction who underwent coronary angiography were included. Significant stenosis was found in 15 and absent in the other 15. The most relevant clinical and ECG data were observed in the few minutes that followed IPNA perfusion: 1) angina pectoris occurred in ten patients of whom eight had CAD (sensitivity: 53 p. cent + 13 p. cent; specificity: 87 p. cent + 9 p. cent); 2) ST segment depression was observed in 11 CAD and 3 non-CAD patients (sensitivity: 73 p. cent + 11 p. cent; specificity: 30 p. cent + 10 p. cent); 3) reversible perfusion defects on planar myocardial thallium 201 scintigrams occurred in 16 patients of whom 13 had CAD. Thallium scintigraphy sensitivity was 87 p. cent + 9 p. cent and specificity was 80 p. cent + 10 p. cent. The combined interpretation and stochastic sequential analysis of two or three presumed independent criteria increased significantly the diagnostic value of the test. We conclude that the isoproterenol test is a safe and reliable method to provoke myocardial ischemia with clinical, ECG and myocardial scintigraphic expression. It has an information content nearly identical to exercise stress test for CAD detection. Because it allows a three step sequential probability analysis, the diagnosis is more reliable than with other pharmacological tests which apply only to scintigraphy.     

Exercise-induced prolongation of the infarct-related Q-waves as a marker of myocardial viability in the infarcted area

OBJECTIVE: It is known that exercise-induced ischemia in patients with coronary artery disease (CAD) may produce QRS prolongation in the surface electrocardiogram (ECG). To investigate the presence of exercise-induced Q-wave prolongation in patients with single-vessel CAD and Q-wave myocardial infarction (MI), in association with the presence of reversible perfusion defects during thallium scintigraphy in the infarcted area. METHODS: 107 consecutive patients (89 males, mean age 56+/-8 years) were evaluated. All patients underwent coronary arteriography, maximal treadmill exercise testing and thallium-201 scintigraphy. Q-wave duration was measured both before exercise testing and during maximal heart rate from 12-lead ECGs recorded with a paper speed of 50 mm/s. RESULTS: Only 57 out of the 107 studied patients showed reversible perfusion defects in the infarcted area during thallium scintigraphy. Q-wave duration was significantly increased from the resting to the stress ECG (DeltaQ-wave duration) in patients with reversible perfusion defects in the infarcted areas (10+/-13 ms), but not in patients with fixed defects in the infarcted zone (-2.0+/-5 ms, p<0.01). The sensitivities and the specificities of Q-wave prolongation, ST segment elevation, and the combination of ST segment elevation with ST segment depression in the reciprocal leads for the detection of myocardial viability in the infarcted area were 82%, 48%, 29% and 88%, 50%, and 90%, respectively. CONCLUSIONS: Exercise-induced Q-wave prolongation is demonstrated in those patients with single-vessel CAD and a recent MI who show reversible perfusion defects in thallium scintigraphy. Exercise-induced Q-wave prolongation was found to be a sensitive and specific ECG marker for the detection of myocardial viability in the infarcted area.     

Intracoronary electrocardiogram for early detection of myocardial viability during coronary angioplasty in acute myocardial infarction.

PURPOSE: The clinical value of the intracoronary electrocardiogram (ECG) for detecting myocardial viability in acute myocardial infarction was evaluated by thallium-201 scintigraphy and left ventriculogram at the chronic stage. METHODS: Intracoronary ECGs, recorded from the tip of a guidewire during emergency coronary angioplasty, were obtained in 65 patients with reperfused anterior myocardial infarction. Further ST segment elevation of greater than 0.2 mV detected during the balloon inflation was taken as significant. The left ventricular segmental shortening was measured from left ventriculograms recorded at acute and chronic stages. The infarct area was defined as viable when a thallium uptake of more than 50% was detected on thallium-201 myocardial scintigraphy at the chronic stage. RESULTS: During emergency coronary angioplasty, significant ST segment elevation was noted in 45 patients (Group A); however, the ST segment was not significantly elevated in the other 20 patients (Group B). The infarct area of 42 patients in Group A and three patients in Group B was viable on scintigraphy. Improvement left ventricular wall motion of the infarct area was observed in 39 of the 42 patients in Group A and the three patients in Group B. Therefore, intracoronary ECG can predict reversible dysfunction with excellent sensitivity (92.9%) and specificity (73.9%). CONCLUSIONS: The myocardium within an infarct area can be regarded as viable when a further ST segment elevation occurs on intracoronary ECG during emergency coronary angioplasty. It is useful, therefore, to monitor the intracoronary ECG during coronary angioplasty balloon inflation to assess the myocardial viability of the infarct area.     

A case of marked exercise-induced ST segment depression in anterior precordial leads with inferoposterior left ventricular aneurysm and significant stenosis of left anterior descending artery

A 71-year-old man was admitted to a community hospital and diagnosed as having acute infero-posterior myocardial infarction. Severe ST segment depression occurred in anterior precordial leads with only 50 m walking, but he had no chest pain. He was then admitted to our hospital. Left ventriculography showed infero-posterior dyskinesis and aneurysm formation. Coronary angiography revealed triple-vessel disease including 90% stenosis at distal site of left anterior descending artery. Exercise thallium-201 myocardial scintigraphy by ergometer showed no filling defect in the anterior segment, though severe ST depression appeared in anterior precordial ECG leads. Infero-posterior segment showed persistent defect. We performed intravenous digital ventriculography at rest and during atrial pacing. Anterior wall motion during pacing was shown to be normal by amplitude and phase analysis. At the same time, the motion of the inferior wall was seen as abnormal and ST segment depression on anterior precordial leads appeared. We considered that in this case the anterior ST depression did not mean anterior myocardial ischemia but might be due to dyskinetic movement of the infero-posterior aneurysm.     

Alterations in myocardial perfusion during painless ST-segment depression in patients with angina pectoris

In order to determine whether painless ST changes represent myocardial ischemia, we studied regional myocardial perfusion in patients with angina pectoris who showed painless ST-segment depression during a treadmill exercise test. Twenty-one patients were evaluated by myocardial imaging using thallium-201 injected intravenously during exercise when painless ST-segment depression was evident. The same examination was repeated in 5 of the above patients when they showed ST-segment depression with chest pain. Myocardial images obtained during painless ST-segment depression revealed perfusion defects in 15 of 21 patients (71%). Images obtained during ST-segment depression with chest pain showed perfusion defects in all 5 patients (100%) including 3 patients who demonstrated no defects during painless ST-segment depression. In these 5 patients, the ST-segment depression associated with pain was significantly greater than that without pain (3.4 +/- 1.1 vs 2.1 +/- 1.1 mm, p less than 0.01). These results suggest that the majority of episodes of painless ST-segment depression occurring during exercise are accompanied by regional myocardial perfusion abnormalities and that transient painless ST-segment depression in patients with angina pectoris might represent less severe myocardial ischemia.     

Ventricular arrhythmias in patients with rest angina: correlation with ST segment changes and extent of coronary atherosclerosis

Major ventricular arrhythmias occurring concurrently with myocardial ischemia are presumed to be the most frequent mechanism for sudden cardiac death. Two hundred eighteen catheterized patients with angina pectoris at rest were reviewed to identify clinical, ECG, and arteriographic features that might correlate with the presence of serious ventricular arrhythmias occurring during episodes of rest pain. Ventricular arrhythmias during episodes of rest pain were significantly more common in patients who manifested transient ST segment elevation in the anterior leads and in patients with marked transient ST segment shifts (greater than 5 mm). Ventricular arrhythmias during episodes of rest pain were not more common in patients with extensive coronary artery disease.     

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.     

Exercise-induced thallium-201 myocardial perfusion defects in angina pectoris without significant coronary artery stenosis

We performed exercise thallium-201 myocardial scintigraphy in 32 patients with angina pectoris to study the incidence of perfusion defects, who had no significant organic stenosis on coronary angiography. None of them had myocardial infarction or cardiomyopathy. Thallium-201 myocardial scintigraphy and 12-lead ECG recording were performed during supine bicycle ergometer exercise. Perfusion defects in thallium-201 scintigrams in SPECT images were assessed during visual analysis by two observers. In the coronary angiograms obtained during intravenous infusion of nitroglycerin, the luminal diameter of 75% stenosis or less in the AHA classification was regarded as an insignificant organic stenosis. Myocardial perfusion defects in the thallium-201 scintigrams were detected in eight (25%) of the 32 patients. Six of these eight patients had variant angina documented during spontaneous attacks with ST elevations in standard 12-lead ECGs. Perfusion defects were demonstrated at the inferior or inferoposterior regions in six patients, one of whom had concomitant anteroseptal defect. The defects were not always accompanied by chest pain. All but one patient demonstrating inferior or inferoposterior defects showed ST depression in leads II, III and aVF on their ECGs, corresponding to inferior wall ischemia. The exception was a case with right bundle branch block. Thus, 25% of the patients with angina pectoris, who had no evidence of significant organic stenosis on their coronary angiograms, exhibited exercise-induced perfusion defects in their thallium-201 scintigrams. Coronary spasms might have caused myocardial ischemia in these patients.     

The detection of myocardial ischemia by thallium-201 myocardial scintigraphy in patients with multiple coronary arterioventricular connections.

The question of whether myocardial ischemia could be induced in 5 patients with multiple coronary arterioventricular connections by thallium-201 (201Tl) exercise stress myocardial scintigraphy was investigated. Both ST-T changes on ECG and transient myocardial perfusion defects in myocardial scintigrams were observed in 2 patients (40%). In previous reports, all multiple coronary arterioventricular connections, which were shown in angiograms, have been regarded as either Thebesian veins or embryonic sinusoids. However, it is unlikely that Thebesian veins cause myocardial ischemia judging from anatomy. If the vessels cause myocardial ischemia, they should be regarded as multiple coronary arterioventricular fistula. Angiography itself cannot differentiate multiple coronary arterioventricular fistula from Thebesian veins or remnants of embryonic sinusoids. Exercise stress myocardial scintigraphy has a high potential to detect myocardial ischemia due to intracoronary steal. Exercise stress myocardial scintigraphy was used to demonstrate myocardial ischemia in multiple coronary arterioventricular connections. It is concluded that exercise stress myocardial scintigraphy is a reliable test to differentiate multiple coronary arterioventricular fistula from Thebesian veins or remnants of embryonic sinusoids in clinical practice.     

Relation between left ventricular function at rest and with exercise and silent myocardial ischemia.

The prognostic value of radionuclide measures of left ventricular function at rest and exercise is well established. Some studies have suggested that the frequency and duration of silent ischemia during ambulatory monitoring provide similar prognostic information; however, studies comparing these two techniques have not been performed. This study examines the relation between left ventricular function at rest and exercise-induced ischemia assessed by radionuclide ventriculography with myocardial ischemia during ambulatory electrocardiographic (ECG) monitoring. Of the 155 patients with coronary artery disease studied, 88% had left ventricular dysfunction with exercise, defined as failure of the ejection fraction to increase by greater than 4% with exercise, and 33% of patients had left ventricular dysfunction at rest (ejection fraction less than 45%); 52% had transient episodes of ST segment depression during 48-h ambulatory ECG monitoring. Exercise-induced left ventricular dysfunction during radionuclide ventriculography was extremely sensitive (94%) in detecting patients with ischemic episodes during ambulatory ECG monitoring; however, only 55% of patients with exercise-induced left ventricular dysfunction had ST segment depression during ambulatory monitoring. Moreover, patients with left ventricular dysfunction at rest had a lower prevalence of transient episodes of ST segment depression (31%) than did patients with normal left ventricular function at rest (62%) (p = 0.008). The relation between prognostically important variables during exercise radionuclide ventriculography and the number and duration of transient episodes of ST depression was examined.(ABSTRACT TRUNCATED AT 250 WORDS)     

Significance of inferior ST segment changes in acute anterior myocardial infarction--relationship between the distribution of left anterior descending artery and concomitant ischemia of the inferior wall

The significance of inferior ST segment changes was studied in 23 patients with acute anterior myocardial infarction by the distribution of the left anterior descending artery (LAD) after percutaneous transluminal coronary recanalization. In 9 patients (Group A) LAD supplied the anterior wall of the left ventricle up to or including the apex but did not reach the inferior wall; in 8 patients (Group B) it continued beyond the apex onto the inferior wall of the left ventricle with well developed collateral circulation; in 6 patients (Group C) it continued beyond the apex onto the inferior wall of the left ventricle with less-developed or no collateral circulation. Thallium-201 scintigraphy and contrast left ventriculography showed that inferior myocardial ischemia was significantly more prominent in Group C than Group A. These results were consistent with coronary anatomy. Inferior ST segment was significantly more depressed in Group A with no concomitant inferior wall ischemia, than in Group C with concomitant inferior wall ischemia (maximal inferior ST segment change: -1.7 +/- 1.1; 0.8 +/- 1.7 mm, respectively; p less than 0.02). In Group A inferior ST segment was depressed in all 6 patients with lateral ST segment elevation, but it was depressed in only one of 3 patients with no lateral ST segment change. Lateral ST segment elevation tended to cause inferior ST segment depression. This study indicates that the inferior ST segment changes in patients with acute anterior myocardial infarction depend on concomitant ischemia of the inferior wall of the left ventricle by the distribution of LAD and the lateral ST segment changes.     

Dipyridamole thallium-201 scintigraphy as a preoperative screening test. A reexamination of its predictive potential. Study of Perioperative Ischemia Research Group.

BACKGROUND. We examined the value of dipyridamole thallium-201 (201Tl) scintigraphy as a preoperative screening test for perioperative myocardial ischemia and infarction. METHODS AND RESULTS. We prospectively studied 60 patients undergoing elective vascular surgery. We performed 201Tl scintigraphy preoperatively and blinded all treating physicians to the results. Historical, clinical, laboratory, and physiological data were gathered throughout hospitalization. Myocardial ischemia was assessed during the intraoperative period using continuous 12-lead electrocardiography (ECG) and transesophageal echocardiography (TEE) and during the postoperative period using continuous two-lead ambulatory ECG. Adverse cardiac outcomes (cardiac death, myocardial infarction, unstable angina, severe ischemia, or congestive heart failure) were assessed daily throughout hospitalization. Twenty-two patients (37%) had defects that improved or reversed on delayed scintigrams (redistribution defects), 18 (30%) had persistent defects, and 20 (33%) had no defects on 201Tl scintigraphy. There was no association between redistribution defects and adverse cardiac outcomes: 54% (seven of 13) of adverse outcomes occurred in patients without redistribution defects, and the risk of an adverse outcome was not significantly increased in patients with redistribution defects (relative risk 1.5, 95% confidence interval 0.6-3.9, p = 0.43). Consistent with these findings, there was also no association between redistribution defects and perioperative ischemia: 54% (19 of all 35) of perioperative ECG and TEE ischemic episodes and 58% (14 of 24) of severe ischemic episodes occurred in patients without redistribution defects. The sensitivity of 201Tl scintigraphy for perioperative ischemia and adverse outcomes ranged from 40% to 54%, specificity from 65% to 71%, positive predictive value from 27% to 47% and negative predictive value from 61% to 82%. CONCLUSIONS. These results differ from those of previous studies and suggest that the routine use of 201Tl scintigraphy for preoperative screening of patients undergoing vascular surgery may not be warranted.     

Vasospastic ischemic mechanism of frequent asymptomatic transient ST-T changes during continuous electrocardiographic monitoring in selected unstable angina patients

Asymptomatic episodes of ST segment and/or T wave changes are often reported during Holter monitoring in patients with angina pectoris. However, the interpretation of such changes is debated relative to silent myocardial ischemia. We studied 11 patients admitted to the CCU because of frequent episodes of unstable anginal attacks who had undergone repeated periods of Holter monitoring, characterized by predominantly occurring asymptomatic episodes of ST segment and/or T wave changes associated with less frequent typical anginal attacks. In a total of 89 days of Holter monitoring, the patients evidenced 520 episodes of transient ECG changes including 180 of ST elevation, 73 of ST depression, and 267 of T wave alterations. Only 12% of episodes were symptomatic. Coronary injection during asymptomatic ST-T changes was performed in eight patients. In six it was possible to document spontaneous coronary spasm. In seven patients ergonovine administration induced anginal pain, ST-T changes, and coronary spasm. In all patients the anginal attacks completely disappeared with medical treatment and the asymptomatic episodes were abolished in six and reduced in four. Our findings support the hypothesis that in certain selected unstable anginal patients, transient asymptomatic ECG changes are caused by acute myocardial ischemia.     

Is the shortening of the QTc interval in Q-wave leads showing ST segment shift during exercise testing a new ECG marker of myocardial ischemia and viability in patients with previous anterior myocardial infarction?

PURPOSE: To evaluate whether the shortening of the QTc-interval, measured in Q-wave leads showing ST segment elevation during exercise testing may be a marker of stress-induced transmural ischemia (and indirectly of myocardial viability) in the infarct zone in patients with prior Q-wave anterior myocardial infarction. METHODS: We evaluated 15 consecutive patients (Group A) with previous anterior myocardial infarction presenting these peculiarities: 1) ST segment elevation over Q waves during exercise testing; 2) critical (> 75%) stenosis of LAD; 3) evidence by echocardiography and stress-redistribution-reinjection 201thallium myocardial scintigraphy (SRR201TIMS) of viable myocardium in the infarct zone (akinetic segments with normal echo-reflectivity plus > 7 mm end-diastolic wall thickness and significant 201thallium redistribution after reinjection). The study control group (Group B) consisted of 15 patients with previous myocardial infarction, critical stenosis of LAD and evidence of scarring by imaging techniques (increased echo-reflectivity associated with an end-diastolic wall thickness < 6 mm and no 201thallium redistribution in infarcted areas). The QTc interval was measured at rest and at peak stress in all leads, and particularly in infarct-related leads showing ST-T changes, and the lead-by-lead fractional difference percentage between the QTc intervals (delta QTc) was calculated. The delta QTc was measured again during exercise testing in 11 patients from Group A (Group A1) who showed significant contractility recovery three months after complete myocardial revascularization. A delta QTc shortening < -10% was considered "significant". RESULTS: In 14/15 patients from Group A, a significant delta QTc shortening was measured, while in 14/15 patients from Group B no significant delta QTc shortening was detected (sensitivity = 93.3%; specificity = 93.3%) (p < 0.0001). The mean delta QTc in Group A was -18.1 +/- 8.5%; the mean delta QTc in Group B was -4.2 +/- 7.8% (p < 0.0001). No patient from Group A1 showed a significant delta QTc shortening in Q-wave leads (mean delta QTc group A1 = +6.9 +/- 14.8%). CONCLUSIONS: delta QTc shortening in infarct-related leads during exercise testing is a simple ECG marker of transmural ischemia and, indirectly, of myocardial-viability. This sign is no more evident after myocardial revascularization and may be useful in identifying "hibernating-myocardium".     

Transient ST-segment depression as a marker of myocardial ischemia during daily life

Patients with angina and coronary artery disease (CAD) have many episodes of transient ST-segment depression during ordinary daily life, and these are often asymptomatic. To investigate this signal as a marker of myocardial ischemia, 30 patients with chronic stable angina and CAD underwent positron tomography, recording the regional myocardial uptake of rubidium-82, pain and ST-segment changes before, during and after 59 technically satisfactory exercise tests, 35 cold pressor tests and 22 episodes of unprovoked ST depression. Exercise resulted in 53 episodes of ST depression with angina and in 5 episodes without pain. After cold pressor tests, there were 3 episodes of ST depression and pain and 12 of painless ST depression. Only 9 episodes of unprovoked ST depression were accompanied by pain. Tomography showed independent evidence of ischemia in 63 (97%) of the total 65 episodes of ST depression with angina and in all 30 episodes of painless ST depression. In each patient perfusion defects occurred in the same myocardial segment during painful and painless ST depression and responses were significantly different from those in 16 normal subjects studied in the same way. These findings support the use of transient ST depression in continuous monitoring to assess the activity of CAD, but only in patients with typical angina pectoris, ST depression during exercise and proved CAD. They strengthen the evidence derived from ambulatory monitoring for a wider picture of the disease than is generally appreciated, with more frequent episodes of silent myocardial ischemia than of angina pectoris.     

A Reappraisal of Exercise Electrocardiographic Indexes of the Severity of Ischemic Heart Disease: Angiographic and Scintigraphic Correlates

Objectives. We explored how the exercise electrocardiographic (ECG) indexes generally presumed to signify severe ischemic heart disease (IHD) correlate with coronary angiographic and scintigraphic myocardial perfusion findings.

Background. In exercise testing, it is generally assumed that the early onset of ST segment depression and its occurrence at a low rate–pressure product (ischemic threshold); the amount of maximal ST segment depression; and a horizontal or downsloping ST segment and its prolonged recovery after exercise signify more severe IHD. However, the relation of these indexes to coronary angiographic and exercise myocardial perfusion findings in patients with IHD is unclear.

Methods. We prospectively carried out a symptom-limited 12-lead Bruce protocol thallium-201 single-photon emission computed tomographic (SPECT) exercise test in 66 consecutive subjects with stable angina, ≥70% stenosis of at least one coronary artery, normal rest ECG and left ventricular wall motion and a prior positive exercise ECG. The above ECG indexes, vessel disease (VD), a VD score and the quantitative thallium-SPECT measures of the extent, maximal deficit and redistribution gradient of the perfusion abnormality were characterized.

Results. Maximal ST segment depression could not differentiate the number of diseased vessels; was not related to VD score, maximal thallium deficit or redistribution gradient; but was related to the extent of perfusion abnormality (r = 0.29, 95% confidence interval [CI] 0.08 to 0.52, p = 0.02). Time of onset of ST segment depression correlated inversely only with VD (r = −0.22, 95% CI −0.44 to −0.05, p < 0.05), whereas the ischemic threshold had low inverse correlation only with VD score (r = −0.25, 95% CI −0.47 to −0.01, p < 0.05) and the redistribution gradient (r = −0.33, 95% CI −0.53 to −0.10, p < 0.01). A horizontal or downsloping compared with an upsloping ST segment did not demonstrate more severe angiographic and scintigraphic disease. Recovery time did not correlate with angiographic and scintigraphic findings, and correlations between angiographic and scintigraphic findings were also low or absent.

Conclusions. In this homogeneous study group, the exercise ECG indexes did not necessarily signify more severe IHD by angiographic and scintigraphic criteria. Lack of concordance between the exercise ECG, angiography and myocardial scintigraphy suggests that these diagnostic modalities examine different facets of myocardial ischemia, underscoring the need for caution in the interpretation of their results.

(J Am Coll Cardiol 1997;29:1497–504)     

A prospective clinical, scintigraphic, angiographic and functional evaluation of patients after inferior myocardial infarction with and without right ventricular dysfunction

To elucidate the functional and prognostic significance of right ventricular dysfunction after acute inferior wall myocardial infarction, 74 consecutive patients with inferior infarction were prospectively evaluated with gated equilibrium blood pool imaging at rest, submaximal exercise thallium-201 scintigraphy and coronary angiography before hospital discharge. In addition, symptom-limited stress thallium-201 scintigraphy was performed in 61 patients at 3 months, and all patients were followed up clinically for 23 +/- 15 months. Utilizing predetermined radionuclide angiographic criteria, 47 patients (Group I) had normal right ventricular function, 12 patients (Group II) had mild to moderate dysfunction and 15 patients (Group III) had severe right ventricular dysfunction. There were no significant differences among the groups with regard to age, history of prior myocardial infarction, peak creatine kinase values, maximal Killip functional class, number or type of in-hospital complications, left ventricular ejection fraction, prevalence of multivessel disease or the distribution and severity of disease affecting the infarct-related vessel. Exercise tolerance as assessed by treadmill time, blood pressure-heart rate product and peak work load in METS was comparable among the three groups, both before hospital discharge and at 3 month follow-up. No differences in indicators of exercise-induced ischemia were noted among the groups, including the prevalence of redistribution thallium-201 defects, ST segment depression or symptoms of chest pain. Finally, cardiac mortality, reinfarction rate and the incidence of medically refractory angina pectoris were similar in the three groups. Thus, right ventricular dysfunction after acute inferior wall myocardial infarction does not appear to limit exercise tolerance or identify a subgroup of patients at higher risk for recurrent cardiac events.