Noninvasive demonstration of underlying severe coronary disease in patients with vasospastic angina

Dipyridamole test, isoproterenol test, and treadmill exercise test were performed in two groups of patients with vasospastic angina (Group 1: 10 patients with 70% or greater coronary narrowings, Group 2: 8 patients with narrowings less than 70%. The results were correlated with coronary anatomy. In Group 1, vasodilation of resistance vessels by dipyridamole elicited ischemic episodes in 9 patients and an increase in myocardial oxygen consumption by isoproterenol caused anginal attacks in 7 patients. None of patients of Group 2 showed positive responses to either drug. All patients of Group 1, and 3 patients of Group 2 gave positive responses to treadmill test. These observations show that several different mechanisms are involved in the pathogenesis of myocardial ischemia in patients with vasospastic angina. Pharmacological interventions have higher specificity than exercise tests in predicting coronary anatomy and are useful for the choice of therapy in the patients.     

Effect of nicorandil on abnormal coronary flow reserve assessed by exercise201Tl scintigraphy in patients with angina pectoris and nearly normal coronary arteriograms

Summary The purpose of the present study is to assess the effect of nicorandil, a coronary vasodilator with a mechanism of potassium channel opening, on the abnormal myocardial²⁰¹Tl perfusion evoked by exercise. Eleven patients who had a history of typical angina, positive exercise electrocardiograms, positive²⁰¹Tl scintigraphy, nearly normal coronary arteriograms, and negative coronary vasospasm underwent exercise²⁰¹Tl scintigraphies under no medication (baseline test) and administration of nicorandil (nicorandil test).²⁰¹Tl was injected at a matched workload in both tests. Nicorandil did not alter heart rate, blood pressure, or the rate-pressure product at the end of the exercise, but it significantly improved the extent score from 0.37±0.22 to 0.20±0.15 (p<0.05) and the severity score from 33.9±32.2 to 13.5±16.4 (p<0.05), and also significantly hastened the²⁰¹Tl mean washout rate from 30.5±14.8% to 37.4±13.1% (p<0.05). Anginal symptoms disappeared in 3 of 5 cases and ST depression improved in 5 of 7 cases after nicorandil. We conclude that nicorandil augments coronary flow reserve, possibly due to a reduction of vasotone in the small coronary arteries.     

Efficacy of intravenous dipyridamole with exercise in thallium-201 myocardial perfusion scintigraphy

To assess the feasibility and the value of thallium–201myocardial perfusion imaging with intravenous dipyridamole incombination with low-level exercise, 81 patients with suspectedor proven coronary artery disease were studied. All patientsunderwent coronary arteriography. Significant coronary arterydisease (stenoses 50%) was present in 59 patients (73%); multivesseldisease (double- and triple-vessel desease) was observed in33 patients (42%). The overall sensitivity and specificity ofthe test were 78% and 86%, respectively. Sensititvity and specificityfor detection of multivessel disease were 70% and 92%, respectively.The sensitivity for detecting coronary artery disease in theRCA, LAD, and LCX was 74%, 82% and 48%, respectively, and thespecificity was 85%, 88% and 88%, respectively. With the combinedprocedure no serious side effects were observed. Mild side effectslike headche, vertigo and uausea were seen in 12 patients (15%). Twenty volunteers with a 1% likelihood of significant coronaryartery disease were examined in the same manner to determinethe maximal specificity of the procedure (100%). Thus, the combinationof two different stress procedures (exercise testing and dipyridamoleinfusion) can be performed safely without serious side effects.The presence, location and extent of significnt coronary arterydisease can be assessed to a similar degree as with conventionalexercise thallium-201 scintigraphy, which has major implicationsfor the detection of coronary artery disease in patients whoare unable to perform maximal exercise.     

Angina pectoris due to possible vasospasm of small coronary arteries.

Recently, the presence of vasospasm in small coronary arteries is speculated in animals and humans. A 40-year-old female patient complained of chest pain at rest. Left ventriculogram showed normal wall motions. Left and right coronary arteries were also normal. After methylergometrine maleate was selectively administered to a right coronary artery, she complained of chest pain, and ST-segment elevation was detected in leads II, III, and aVF of ECG. Right coronary arteriography was performed immediately, but no coronary stenosis was found. The next day, methylergometrine maleate was again administered intravenously and the patient complained of chest pain, but no ischemic changes were observed in ECG. Thallium-201 myocardial scintigraphy followed immediately. Apical perfusion defect was detected in stress image. In the delayed image, it showed complete redistribution. Three days later, catheterization and scintigraphy were performed at the same time. When methylergometrine maleate was administered to the left coronary artery, she complained of chest pain within a few minutes of the injection; however, ECG remained unchanged. 201Tl myocardial scintigraphy was performed immediately. In the stress image, it showed apical perfusion defect as shown in the intravenous methylergometrine maleate injection study. It also showed complete redistribution in the delayed image. Apical perfusion defect can be attributed to myocardial ischemia of left coronary artery, which are too small to be detected by conventional coronary arteriography. Vasospasm in small coronary arteries may be involved in this phenomenon.     

Thallium-201 scintigraphy after dipyridamole infusion with low-level exercise. III. Clinical significance and additional diagnostic value of ST segment depression and angina pectoris during the test

Intravenous dipyridamole thallium testing is a useful alternativeprocedure for assessing coronary artery disease (CAD) in patientswho are unable to perform maximal exercise tests. IschaemicST segment depression and angina pectoris are frequently observedduring the test, in particular when exercise is added to dipyridamoleinfusion. To establish the clinical significance and additionaldiagnostic value of these markers of ischaemia during dipyridamolelow-level exercise testing (DXT) 57 patients with CAD (groupA), 21 patients with normal or near-normal coronary arteriesat coronary arteriography (group B), and 20 healthy subjectswith low likelihood of CAD (group C) were studied. During DXT ischaemic ST segment depression was observed in 28patients (47%) of group A and in two patients (10%) of groupB. Angina pectoris was experienced by 35 patients (61%) of groupA and by five patients (24%) of group B. The positive predictivevalue of both ST depression and angina pectoris was high (88and 93%, respectively), but the negative predictive values werelow (42 and 40%, respectively). Combining ST segment analysiswith the findings of thallium imaging significantly increasedthe diagnostic accuracy of the test. ST segment depression, angina pectoris, and thallium abnormalitieswere highly specific findings if the study population consistedof asymptomatic subjects with a low likelihood of CAD (groupC). Sensitivity for the detection of the presence of CAD increasedwith the extent of CAD for all parameters studied. Thus, STdepression and angina pectoris, alone or in combination, duringDXT have little diagnostic significance, although sensitivityis increased in patients with triple-vessel CAD. Analysis ofthe ST segment provides additional information and should thereforebe included in the overall interpretation of the test results.A marked difference in the false positive rates for all parameterswas observed between asymptomatic subjects and angiographicallynormal patients with chest pain syndromes, which can be explainedby selection bias.     

Impact of thallium-201 imaging on clinical assessment and management of patients with chest pain

The histories, rest, and exercise ECG results of 60 patients without myocardial infarction complaining of chest pain were submitted to 6 physicians (3 cardiologists and 3 noncardiologists) who were unaware of the angiographic findings. The physicians were requested to estimate the probability of coronary artery disease present in percentages and to assess the need for coronary angiography on a five-point scale (1 = definitely not indicated, 5 = definitely indicated). After obtaining the results of thallium-201 imaging following dipyridamole (0.50 mg/kg intravenously) administration, the physicians were again requested to estimate probability and need for angiography. In the 43 patients with coronary artery disease the judgment of probability was increased significantly after 201Tl from 75.6 +/- 20.2% to 82.9 +/- 23.2% (p less than 0.001) and the need for angiography from 4.3 +/- 0.9% to 4.5 +/- 0.9% (p less than 0.001). In the subgroup of patients with atypical angina the relative change in probability was higher than in other subgroups of patients with coronary artery disease. In the 17 patients with normal coronary arteries the probability estimation fell after 201Tl from 36.7 +/- 22.0% to 24.8 +/- 21.0% (p less than 0.001), the need for angiography was decreased from 2.7 +/- 1.1% to 2.2 +/- 1.2% (p less than 0.001). With the 201Tl information, cardiologists performed a better diagnostic differentiation of patients with and without coronary artery disease than noncardiologists. The study demonstrates the improvement of clinical diagnosis in patients with chest pain by thallium-201 imaging and confirms the favorable influence of the method on the management of the patients in terms of indications for coronary angiography.     

Additional value of thallium-201 SPECT to a conventional exercise test for the identification of severe coronary lesions after an episode of unstable coronary artery disease

The additional value of thallium-201 SPECT to a conventional exercise test for the identification of patients with severe coronary lesions was evaluated in 170 men, one month after an episode of unstable coronary artery disease. Severe coronary lesions at coronary angiography — defined as three vessel disease, left main stenosis or proximal left anterior descending artery stenosis as part of two vessel disease — were observed in 45.9%. In the SPECT image, the left ventricular myocardium was divided into nine segments and each segment was classified as either normal (=0), reduced uptake (=1) or uptake defect (=2). The sum of gradings in all segments post-exercise was denoted SPECT score. The patients were divided into nine different groups regarding ST-depression during exercise (no ST-depression, ST-depression in 1–2 leads or 3 leads) and SPECT score (no SPECT score, 1–3 scores or 4 scores). Severe coronary lesions were, in 68% identified by SPECT score 4 and in 65% by ST-depression in 1 lead at exercise test. The specificity for identification of severe coronary lesions was, for both tests, 65%. SPECT score 4 and/or ST-depression in 3 leads identified 82% of the patients with severe coronary lesions with a specificity of 63%. Furthermore, SPECT score 3 identified more patients with isolated proximal left anterior descending artery stenosis than ST-depression alone at exercise test.     

Abnormal heart rate control in vasospastic angina: effects of calcium antagonists

We examined the effects of administration of calcium antagonists on the heart rate response to treadmill exercise in 11 patients with vasospastic angina and 8 healthy young volunteers. The exercise test was performed by walking on a treadmill at a constant speed and grade according to a scheme of pseudo-randomized sequence for 19 min. The dynamic property of heart rate response to exercise was evaluated by using a frequency analytic procedure. The exercise test was also studied in 21 age-matched normal controls without drug administration. Administration of calcium antagonists revealed no significant effects on heart rate and blood pressure at rest in young healthy subjects or in patients with vasospastic angina. Young volunteers showed the same normal properties of heart rate response to exercise before and after calcium antagonists. Vasospastic angina showed abnormal heart rate response to exercise and revealed characteristically different transfer function from that in normal controls. These characteristics were not affected by treatment with calcium antagonists except for a slight, uniform decrease of gain of the system over the whole frequency range. Accordingly, the present exercise test can feasibly be used in the diagnosis and management of vasospastic angina even when calcium antagonists are administered to the patients.     

Exercise echocardiography after stabilization of unstable angina: correlation with exercise thallium-201 single photon emission computed tomography.

The diagnostic usefulness of predischarge exercise echocardiography in 35 patients with unstable angina who responded to medical therapy was correlated with exercise thallium-201 single photon emission computed tomography (TI-SPECT) performed, on the average, three days after the exercise echocardiography. None of the patients had myocardial infarction prior to hospitalization or before TI-SPECT and none had left bundle-branch block on their rest electrocardiogram (ECG). Exercise echocardiography was positive in 21 patients and TI-SPECT in 24. The results of the two techniques were concordant in 28 of 35 patients (agreement = 80%, k = 0.57 +/- 0.14, p less than 0.001). Wall-by-wall comparison of the distribution of exercise-induced wall motion abnormalities with reversible thallium defects showed complete or partial correlation in all of 19 patients in whom both the tests were positive. A positive exercise ECG and positive exercise echocardiography identified 11 of 11 patients with angiographically verified significant coronary artery disease (CAD) and 11 of 12 patients (92%) with positive TI-SPECT. Thus, exercise echocardiography is a valuable addition to routine predischarge exercise test in the noninvasive diagnosis of myocardial ischemia and shows a good correlation with TI-SPECT in detecting and localizing ischemia in patients with unstable angina stabilized on medical therapy.     

Abnormal thallium-201 scans in patients with chest pain and angiographically normal coronary arteries

We reviewed the exercise thallium-201 (TI-201) scans and clinical data of 41 patients with chest pain and normal coronary arteries to identify clinical factors associated with "false-positive" studies. Exercise TI-201 studies were performed before angiography and often precipitated referral. Sex, beta-blocker therapy, anginal pattern, and results of exercise electrocardiography were evaluated and compared with TI-201 imaging. A negative TI-201 study was the most common finding (p less than 0.005). Of the 41 patients, 11 (27%) had abnormal exercise TI-201 scans. No clinical factor was significantly associated with a false-positive TI-201 scans. Of the 11 patients with abnormal scans, 9 had greater than or equal to 1 cardiac abnormality: right bundle branch block in 2, mitral valve prolapse in 3, paroxysmal atrial fibrillation in 2, abnormal left ventricular diastolic pressure in 3, and left bundle branch block in 1. Thus, (1) when results of exercise TI-201 imaging are used to refer patients for angiography, "false-positive" TI-201 studies are common; (2) sex, beta blockade, anginal pattern, and results of exercise electrocardiogram are not useful predictors of a false-positive TI-201 study; and (3) patients with chest pain, normal coronary arteries, and abnormal TI-201 scans frequently have other cardiac abnormalities.     

Value of radionuclide assessment with thallium 201 scintigraphy in carnitine deficiency cardiomyopathy

The case of a 30 month-old boy who presented with isolated severedilated cardiomyopathy is reported. The diagnosis of systemiccarnitine deficiency was confirmed by low serum and tissue carnitinelevels. During oral L-carnitine therapy, dramatic improvementof the cardiac function was assessed by radionuclide methods.Myocardial thallium 201 uptake was closely correlated with cardiacfunction studied by angiosintigraphy. These methods are simple,easily reproducible, non-ivasive and involve little radiation.In a case of cardiomyopathy, we suggest an immediate trial oforal carnitine treatment; the efficacy of the therapy can beconfirmed by isotopic tests with thallium 201 scintigraphy.     

Long-term (10 years) prognostic value of a normal thallium-201 myocardial exercise scintigraphy in patients with coronary artery disease documented by angiography

In order to assess the prognostic significance of normal exercisethallium-210 myocardial scintigraphy in patients with documentedcoronary artery disease, we studied the incidence of cardiacdeath and non-fatal myocardial infarction in 69 symptomaticpatients without prior Q wave myocardial infarction, who demonstratedone or more significant coronary lesions (stenosis 70%) on anangiogram performed within 3 months of scintigraphy (Group 1).These patients were compared to a second group of 136 patientswith an abnormal exercise scintigram, defined by the presenceof reversible defect(s) and angiographically proven coronaryartery disease (Group 2), and to a third group of 102 patientswith normal exercise scintigraphy without significant coronarylesions (stenosis 30%) or with normal coronary angiography (Group3). In contrast to coronary lesions observed in Group 2, patientsin Group I presented more frequently with single- vessel disease(83% vs 35%, P>0·0001) and with more distal lesions(55% vs 23%, P>0·0001). Over a mean follow-up periodof 8·6 years, one fatal and eight non-fatal cases ofmyocardial infarction were observed in Group 1. The majorityof patients in Group 1 were treated medically: only 24 (35%)underwent myocardial revascularization, usually by coronaryangioplasty. There was no significant difference in the incidenceof combined major cardiac events (cardiac death, non-fatal myocardialinfarction) in patients with normal exercise scintigraphy, withor without documented coronary artery disease (Groups 1 and3), while the incidence was higher in Group 2. However, whilethe mortality remained very low in Group 1, the incidence ofnon-fatal myocardial infraction was not different from thatof Group 2, where most patients underwent revascularizationprocedures. In conclusion, patients with coronary artery disease and a normalexercise thallium-201 myocardial scintigram usually have mildcoronary lesions (single-vessel disease, distal location) andgood long-term prognosis, with a low incidence of cardiac death.     

Improvement of myocardial perfusion after thrombolysis assessed by thallium-201 exercise scintigraphy

The effects of recanalization by early intracoronary streptokinasein acute myocardial infarction on myocardial perfusion werestudied in a subset of 236 out of 533 patients enrolled in aprospective multicentre trial, randomly allocated to eitherconventional treatment or to thrombolysis. Maximal symptom-limitedthallium-201 stress testing was performed nine to 14 (median12) weeks after the acute event in 236 patients with a firstmyocardial infarction, of whom 108 patients were allocated toconventional treatment and 128 patients to thromolysis. Three-viewthallium exercise and redistribution scintigrams were dividedinto eight segments. The number of normal thallium segmentsat redistribution was 5.3±1.6 (mean±SD) in thecontrol group and 5.8±1.6 in the thrombolysis group (P<0.01), indicating increased myocardial perfusion after earlythrombolytic treatment. This beneficial effect was particularlyevident in patients with a first anterior infraction with 4.8±1.6normal thallium segments in the control group and 5.9±1.6normal segments in the thrombolysis group (P <0.001). Therewas no difference in residual ischaemia during exercise betweenthe control and the thrombolysis group either in the patientswith anterior or in those with inferior infarction. It is concluded that early thrombolysis within 4 h after onsetof symptoms, in some of the patients followed by angioplastyor coronary artery bypass surgery, leads to sustained improvementof myocardial perfusion at rest without excessive ischaemiaduring exercise, particularly in patients with acute anteriorinfarction.     

Reproducibility of myocardial thallium-201 washout in studies applying a standardized dipyridamole stress protocol

Thallium-201 (²⁰¹T1) washout analysis was proposed as an adjunctive tool to improve the detection of coronary artery disease (CAD). Since reproducibility of ²⁰¹T1 washout in dipyridamole (DPM) stress studies is unknown, this item was evaluated in 32 patients (24 with CAD, 8 without CAD), who were scintigraphed twice within 1–2 weeks. At 2 minutes following DPM infusion (0.5 mg/kg/5 min), 2 mCi ²⁰¹T1 were injected. Global and segmental washout were calculated by comparing circumferential profiles of respective background-corrected stress (left anterior oblique (LAO) 45°: 8 min postinfusion (p.i.), 35 min p.i.; anterior (ANT): 17 min p.i.; LAO 70°: 26 min p.i.) and redistribution (4 h p.i.) images. Whereas visual findings were comparable for study I and II, reproducibility of ²⁰¹T1 washout was low, indicated by comparing variances among patients with variance between studies, which were 28.8 and 71.2% of total variance, respectively. Mean differences of segmental washout between the studies ranged from 9.75 to 19.24% with only minor differences with regard to the different views and segments evaluated. Variability was lower using the intermediate instead of the initial scintigram as reference for the redistribution image (12.87±11.64% vs. 18.59±14.43%, n = 85; p<0.01). Variability was higher for nonstenosed compared to stenosed segments (14.54 ± 11.41%, n=32 vs. 9.89±8.03%, n=28, p<0.05). Correspondent with results of visual interpretation, variance of relative differences of washout values between neighboring segments was lower than variance statistically expected from variability of washout values between study I and II (12.79%, n=216 vs. 21.55%, n=270; F=2.76, p<0.01). It is suggested, that considerable washout variability might explain the controversially discussed diagnostic value of ²⁰¹T1 washout analysis in DPM stress studies.     

Thallium-201 scintigraphy perfusion defect with dipyridamole in a patient with a myocardial bridge

A patient with myocardial bridging and a thallium-201 scintigraphy perfusion defect after the administration of intravenous dipyridamole is presented. The same patient had a normal perfusion study on exercise stress testing. The effects of coronary vasodilators and dipyridamole on coronary artery flow patterns in patients with myocardial bridging are discussed. We suggest that coronary vasodilators may induce perfusion defects in patients with myocardial bridging and should be avoided in such patients.     

Autonomic balance in patients with angina and a normal coronary angiogram

The pathophysiology of angina pectoris in patients with a normalcoronary angiogram is not clear. Furthermore, the pathophysiologicalimpact of ST changes in syndrome X is controversial. The purposeof this study was to investigate cardiac autonomic function,by measuring 24 h heart rate variability, in patients with andwithout electrocardiographic evidence of ischaemia during exercise. Thirty-two patients with angina pectoris, a normal coronaryangiogram, echocardiogram, hyperventilation test and gastro-oesophagealinvestigation were studied. Fourteen healthy subjects servedas controls. Fifteen patients had significant ST segment depressionduring stress testing, whereas 17 had no electrocardiographicsigns of ischaemia. Heart rate variability was calculated as(1) mean RR= mean of all normal RR intervals, (2) the differencein mean RR level between when awake and when asleep (mean RRwake-sleep)—a tentative index of sympathetic activation,(3) the standard deviation (SD)—a broad band measure ofautonomic balance, and (4) a percentage of successive RR intervaldifferences 6% (pNN6%)—an index of vagal modulation. Thecoronary vascular resistance was measured at rest and duringpacing. Mean RR and autonomic indexes did not differ between patientswith a positive exercise test and controls (831/884 m 24 h SD125/134 m pNN6% 6.715.4%, respectively). Patients with a normalexercise test had shorter mean RR (758 ms vs 844 m P<0.05)and significantly reduced 24-h SD (103 ms vs 134 m P<0.05)than controls, whereas values for vagal index (6.5% vs 5.4%)did not differ from healthy controls. Mean RR wake-sleep alsotended to be lower in patients with a normal exercise test (–125 ms vs – 173 ms) compared to controls (P<0.1). Patientswith a positive exercise test had a significantly attenuatedreduction in coronary vascular resistance during pacing in comparisonto patients with a normal exercise test (–0.131–0.26mmHg x min. ml^{– 1}; P<0.05). The findings suggest the occurrence of general elevated sympatheticactivation in angina patients with a normal exercise test. Patientswith a positive exercise test exhibited no signs of autonomicdysfunction although these patients had altered coronary vascularresistance indicating microvascular angina. This supports thesuggestion that patients with a normal exercise test constitutean independent pathophysiological entity.     

Coronary artery vasoregulation and left ventricular function in patients with angina pectoris-like pain and normal coronary angiograms

Twenty patients with angina pectoris-like pain, normal coronary angiography and abnormal exercise 201Tl scans were investigated by means of haemodynamic, coronary sinus blood flow and lactate determinations before and after cold provocation, pacing and dipyridamole infusion. Radionuclide angiography, a new exercise 201Tl scan and noninvasive hyperventilation and ergonovine tests were performed. Intracoronary infusions of acetylcholine were given in increasing doses and a second coronary angiogram in combination with a 201Tl scintigram was performed. Despite a previously pathological 201Tl scintigram, with reversible perfusion defects, only ten of the patients had reversible perfusion defects at the second investigation. Hyperventilation and ergonovine tests did not result in ECG signs indicative of coronary spasm. Intracoronary infusion of acetylcholine resulted in a diffuse coronary constriction in 3 of 14 patients, and in one patient a perfusion defect was observed on thallium scintigram. In conclusion, although most of the common methods for inducing coronary vasospasm were used, no consistent pattern of reaction was found to explain the chest pains experienced in this group of patients.     

Verapamil in effort-induced angina pectoris in patients with normal coronary arteries

Summary: Two patients with classical effort-induced angina pectoris associated with abnormal ST-segment depression on graded exercise testing and normal coronary arteriograms are described. Both patients deteriorated during treatment with propranolol, and became asymptomatic during treatment with verapamil with normal graded exercise tests. Verapamil may thus improve an inadequate vasodilatatory response of the coronary vascular bed to effort.     

Comparison of dipyridamole and treadmill exercise for enhancing thallium-201 perfusion defects in patients with coronary artery disease

Dipyridamole was compared with exercise as a method of enhancingmyocardial perfusion defects on thallium-201 scintiscans. Twentypatients with angina had scans after treadmill exercise to nearthe limit of effort tolerance, and again 4 h later in the redistributionphase. On a separate occasion the same patients had scans afterintravenous dipyridamole 0.6 mg/kg. Fifteen of them were alsoinvestigated by coronary angiography. Exercise and drug-inducedcoronary dilatation caused segmental abnormalities of similardegree but the anatomical areas showing these perfusion defectscorrelated less well. Neither technique offered any clear advantageover the other in predicting the site of coronary stenosis,or in the quality of images obtained. Unwanted drug effectsafter intravenous dipyridamole were minor but included chestpain in four patients. Intravenous dipyridamole can reasonablybe used instead of exercise for thallium-201 scintiscans. Thetechnique will be of particular value when exercise testingis impracticable.     

True-positive exercise electrocardiogram/false-negative thallium-201 scintigram: a proposal of a mechanism for the paradox

A 72-year-old man with exertional angina had a strongly positive exercise electrocardiogram (EECG) with a negative thallium-201 myocardial perfusion scintigram (Tl). Arteriography revealed triple-vessel coronary artery disease, for which he underwent aortocoronary bypass grafting. Repeat EECG was negative, and it was again associated with a negative Tl. The false-negative Tl on the first test was felt to be due to a rare phenomenon of homogeneously distributed reversible exercise-induced myocardial ischemia, leading to a uniform radiotracer count density. The even distribution of ischemia would also be expected to render a false-negative EECG, due to electrocardiographic cancellation, and this is frequently the case. However, in the patient presented herein, we propose that the ischemic cardiac apex rendered the EECG strongly positive because its position was not opposed by an ischemic muscular region, and thus an uncancelled ischemic ST-segment vector was generated. This hypothesis is supported by our recent work showing the unique role of the ischemic apex (among all the other myocardial territories) in rendering the EECG positive.