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

Thallium-201 Single Photon Emission Computed Tomography in Patients with Symptoms of Heart Disease and Non-Significant Coronary Artery Lesions

Polar presentations of coronary angiograms and myocardial 201T1 SPECT were compared in 44 patients without significant coronary artery disease (< 50% stenosis at angiography). Regions of reduced isotope activity (defects) were present in 18 patients (41%). Nine of these had angiographic and/or clinical evidence of non-coronary heart disease, such as documented or suspected myocardial infarction, dilated cardiomyopathy or other myocardial diseases. Such defects could be caused by impaired small vessel blood flow, abnormalities in cell membrane transport or relative differences in left ventricular wall thickness. In 9 patients defects were probably due to attenuation artifacts. Defects in patients with heart diseases were significantly larger than in those without obvious disease. The information content in coronary angiography and 201T1 SPECT overlap but are not congruent. Coronary angiography describes morphology of large coronary vessels, whereas 201T1 SPECT contains information of large and small vessel perfusion as well as membrane transport of 201T1 ions.

Stress cardiomyopathy: Is it limited to Takotsubo syndrome? Problems of definition

In 2006, Takotsubo syndrome (TTC) was described as a distinct type of stress-induced cardiomyopathy (stress cardiomyopathy). However, when thinking about Takotsubo cardiomyopathy from the viewpoints of the AHA and ESC classifications, 2 possible problems may arise. The first potential problem is that a forecast of disease outcome is lacking in the ESC classification, whereas the AHA only states that 'outcome is favorable with appropriate medical therapy'. However, based on the literature data, one can make a general conclusion that occurrence of myocardial lesions in TTC (i.e., myocardial fibrosis and contraction-band necrosis) causes the same effects as in other diseases with similar levels of myocardial damage and should not be considered to have a lesser impact on mortality. To summarise, TTC can cause not only severe complications such as pulmonary oedema, cardiogenic shock, and dangerous ventricular arrhythmias, but also damage to the myocardium, which can result in the development of potentially fatal conditions even after the disappearance of LV apical ballooning. The second potential problem arises from the definition of TTC as a stress cardiomyopathy in the AHA classification. In fact, the main factors leading to TTC are stress and microvascular anginas, since, as has been already discussed, coronary spasm can cause myocardium stunning, resulting in persistent apical ballooning. Thus, based on this review, 3 distinct types of stress cardiomyopathies exist (variant angina, microvascular angina, and TTC), with poor prognosis. Adding these diseases to the classification of cardiomyopathies will facilitate diagnosis and preventive prolonged treatment, which should include intensive anti-stress therapy.

Frequency and severity of myocardial perfusion abnormalities using Tc-99m MIBI SPECT in cardiac syndrome X

Background

Cardiac syndrome X is defined by a typical angina pectoris with normal or near normal (stenosis <40%) coronary angiogram with or without electrocardiogram (ECG) change or atypical angina pectoris with normal or near normal coronary angiogram plus a positive none-invasive test (exercise tolerance test or myocardial perfusion scan) with or without ECG change. Studies with myocardial perfusion imaging on this syndrome have indicated some abnormal perfusion scan. We evaluated the role of myocardial perfusion imaging (MPI) and also the severity and extent of perfusion abnormality using Tc-99m MIBI Single Photon Emission Computed Tomography (SPECT) in these patients.

Methods

The study group consisted of 36 patients with cardiac syndrome X. The semiquantitative perfusion analysis was performed using exercise Tc-99m MIBI SPECT. The MPI results were analyzed by the number, location and severity of perfusion defects.

Results

Abnormal perfusion defects were detected in 13 (36.10%) cases, while the remaining 23 (63.90%) had normal cardiac imaging. Five of 13 (38.4%) abnormal studies showed multiple perfusion defects. The defects were localized in the apex in 3, apical segments in 4, midventricular segments in 12 and basal segments in 6 cases. Fourteen (56%) of all abnormal segments revealed mild, 7(28%) moderate and 4 (16%) severe reduction of tracer uptake. No fixed defects were identified. The vessel territories were approximately the same in all subjects. The Exercise treadmill test (ETT) was positive in 25(69%) and negative in 11(30%) patients. There was no consistent pattern as related to the extent of MPI defects or exercise test results.

Conclusion

Our study suggests that multiple perfusion abnormalities with different levels of severity are common in cardiac syndrome X, with more than 30 % of these patients having at least one abnormal perfusion segment. Our findings suggest that in these patients microvascular angina is probably more common than is generally believed.

Myocardial glucose metabolism assessed by positron emission tomography and the histopathologic findings of microvessels in syndrome X

BACKGROUND

Syndrome X has been recognized as a disease that is primarily reflected in the cardiac microvasculature. Myocardial metabolism in this condition has been studied, but not in relation to small vessel pathology.

METHODS AND RESULTS

In order to examine the relationship between myocardial metabolism and small vessel pathology, 24 consecutive patients with syndrome X (7 men, 17 women; mean age 58 years) were evaluated by the thallium exercise stress test, positron emission tomography using F-18 fluoro-deoxyglucose (FDG), and an endomyocardial biopsy. All patients showed either diffuse or focal increase in the myocardial uptake of FDG, but only 17 patients (71%) showed hypoperfused areas with partial or complete redistribution in the thallium study. Quantification of myocardial FDG uptake revealed that the value in syndrome X patients was 10-fold higher than in controls (p<0.0001). Histopathological examination revealed that in syndrome X there is an extensive increase in smooth muscle cells and thickening of the vascular wall, even in capillary vessels, and the small vessel lumen was markedly narrowed. There was a significant inverse correlation between FDG myocardial uptake and the microvessel luminal area.

CONCLUSIONS

In syndrome X patients, myocardial FDG uptake is increased extensively, which is strongly associated with narrowed myocardial microvasculature.

Technetium-99m tetrofosmin myocardial perfusion single photon emission computed tomography in syndrome X: a preliminary report

Syndrome X is used to describe patients with chest pain and a normal coronary angiogram. We reviewed technetium-99m tetrofosmin (Tc-99m TF) myocardial perfusion single photon emission computed tomography (SPECT) results and clinical data of 43 syndrome X patients and 30 healthy controls with normal left ventricular ejection fraction and no cardiac abnormalities. The Tc-99m TF myocardial perfusion SPECT results showed 12 (27.9%) syndrome X patients had normal myocardial perfusion and 31 (72.1%) had abnormal myocardial perfusion, including 6 (14.0%) patients with fixed defects. 20 (46.5%) patients with transient defects, and 5 (11.6%) patients with reverse defects. The results of exercise ECG were not related to perfusion defects in Tc-99m TF myocardial perfusion SPECT. In contrast, all of the 30 (100.0%) healthy controls had normal myocardial perfusion SPECT results. We conclude that abnormal Tc-99m TF myocardial perfusion SPECT is common in syndrome X and does not correlate well with the exercise ECG. However, further studies with larger case numbers and long term follow up in patients with myocardial events are necessary to support our findings.

The higher likelihood of developing cardiomegaly during follow-up in patients with syndrome X and abnormal thallium-201 myocardial perfusion SPECT

'Syndrome X' describes patients with exertional chest pain and a normal coronary arteriogram. In some patients, acute myocardial ischemia can be demonstrated by regional myocardial perfusion defects on thallium-201 exercise test. However, some patients with typical angina have normal perfusion on thallium-201 heart scintigraphy. It is not clear whether there are different prognoses for patients with normal and abnormal thallium studies. In this study, the clinical features, long term follow-up and clinical results of syndrome X patients with normal and abnormal thallium studies were evaluated to determine the differences between these two groups. Fifty-nine patients (52 males, seven females, mean age 62+/-6 years) with syndrome X were enrolled and divided into two groups on the basis of results of thallium-201 heart scintigraphy. Group I was comprised of 22 patients with normal thallium-201 perfusion scan and group II was comprised of 37 patients with abnormal thallium-201 heart scan. All subjects received coronary arteriography, exercise test, thallium-201 myocardial SPECT, ejection fraction of left ventricle, echocardiography, blood analysis and long term follow-up with questionnaire for 10 years. Lower maximal rate-pressure product and higher angina scores were found in group II. More patients developed cardiomegaly (nine of 33 patients) in group II than in group I (one of 21 patients). Both groups, however, were at low risk for cardiac events (cardiac death or myocardial infarction).

Negative stress echocardiographic responses in normotensive and hypertensive patients with angina pectoris, positive exercise stress testing, and normal coronary arteriograms

OBJECTIVES

To systematically compare the results of dobutamine stress echocardiography in matched groups of hypertensive and normotensive patients with anginal chest pain and normal coronary arteriograms (CPNA).

SETTING

University hospital.

SUBJECTS

33 patients with exertional anginal chest pain, a positive exercise stress ECG, and a completely normal coronary arteriogram; 17 had a history of systemic hypertension (14 women; mean (SD) age 57 (6) years), and 16 had no hypertensive history (12 women; age 54 (9) years).

METHODS

Ambulatory ECG monitoring, dobutamine stress echocardiography, and thallium-201 single photon emission computed tomography (SPECT) were performed in all subjects.

RESULTS

All patients had normal left ventricular systolic function at rest and none fulfilled the criteria for ventricular hypertrophy. Eight normotensive patients and 10 hypertensive patients had perfusion abnormalities on thallium SPECT (p = 0.61). Dobutamine infusion reproduced anginal pain in seven normotensive and seven hypertensive patients (p = 0.88). ST segment depression was also recorded in eight normotensive patients and seven hypertensive patients (p = 0. 61). No patient in either group developed regional wall motion abnormalities during dobutamine stress echocardiography.

CONCLUSIONS

Neither hypertensive nor normotensive CPNA patients developed regional wall motion abnormalities during dobutamine stress echocardiography, despite the high prevalence of scintigraphic perfusion defects in both groups and the presence of chest pain and ST segment depression. Thus myocardial ischaemia was not present in either group, or else dobutamine stress echocardiography is insensitive to ischaemia caused by microvascular dysfunction.

Elevated endothelin concentrations are associated with reduced coronary vasomotor responses in patients with chest pain and normal coronary arteriograms

OBJECTIVES

The purpose of this study was to investigate the relationship between arterial and coronary sinus endothelin (ET) concentrations and coronary vasomotor responses during rapid atrial pacing in patients with chest pain and normal coronary arteriograms (CPNA).

BACKGROUND

Plasma ET concentrations are significantly higher in CPNA patients than in healthy control subjects.

METHODS

We investigated 19 carefully characterized CPNA patients (14 women; mean age 53 +/- 9 years) of whom 10 had positive electrocardiographic responses to exercise. The percentage fall in coronary vascular resistance (%d.CVR) after 10 min of rapid atrial pacing was determined using a thermodilution pacing catheter. Plasma ET concentrations were measured by radioimmunoassay on simultaneously drawn arterial and coronary sinus samples.

RESULTS

No significant differences in ET concentrations were observed between men and women, but a strong statistical trend suggested that %d.CVR was lower in women than men (27[23 to 31]% vs. 34[29 to 45]%--median[interquartile range]; p = 0.07). Simple regression analysis including only the women (n = 14) suggested a significant relationship between baseline arterial ET concentrations and %d.CVR (R2 = 0.34; p = 0.06). Furthermore, stepwise multivariate regression analysis of the group as a whole indicated that both gender (p = 0.03) and baseline arterial ET concentration (p = 0.02) were independently predictive of %d.CVR (R2 = 0.44; overall p = 0.02); this relationship predicts that women with high ET levels would have the lowest %d.CVR during pacing.

CONCLUSIONS

These data support the hypothesis that elevated ET activity may be associated with reduced coronary flow responses during rapid atrial pacing in CPNA patients.

Early and delayed Tc-99m-tetrofosmin myocardial SPECT in patients with left bundle branch block

To determine the utility of the myocardial tracer Tc-99m-tetrofosmin in the examination of patients with left bundle branch block (LBBB) and to investigate Tc-99m-tetrofosmin uptake and retention in the myocardium, early and delayed Tc-99m-tetrofosmin SPECT was performed in 10 patients having LBBB without coronary stenosis.

METHODS

After 740 MBq of Tc-99m-tetrofosmin injection in the resting state, the early and delayed SPECT imaging was done at 30 min and 180 min, respectively.

RESULTS

Decreased Tc-99m-tetrofosmin uptake in the septal segments was observed in 4 patients (40%) at 30 min and in 9 (90%) at 180 min. Reverse redistribution was seen in 9 of 10 patients. In patients with LBBB, the septal-to-lateral uptake ratio was lower in the delayed images than in the early images (0.80 +/- 0.09 vs. 0.89 +/- 0.09, p < 0.001). In patients with LBBB, the washout rate of Tc-99m-tetrofosmin was higher in the septal segments than in the lateral segments (28.3 +/- 4.3% vs. 22.8 +/- 3.3%, p < 0.001).

CONCLUSION

The SPECT data indicate that in LBBB without coronary stenosis, the uptake of Tc-99m-tetrofosmin is decreased in the septal wall, and that reverse redistribution occurs frequently. Our results contribute to the elucidation of both the cellular biokinetics of Tc-99m-tetrofosmin in the myocardium and the hemodynamics of the septum in LBBB, and indicate the possible clinical utility of Tc-99m-tetrofosmin.

Accuracy and cost-effectiveness of exercise echocardiography for detection of coronary artery disease in patients with mitral valve prolapse

Mitral valve prolapse is sometimes associated with chest pain, but this symptom may also be caused by coexisting coronary disease. The accuracy of exercise echocardiography in diagnosing coronary disease in these patients and the most cost-efficient diagnostic approach are unclear. We studied 96 patients (aged 59 +/- 12 years; 70 men) with mitral valve prolapse who underwent exercise electrocardiography, exercise echocardiography, and coronary angiography. The accuracies of seven diagnostic strategies based on the current and expected use of exercise electrocardiography and exercise echocardiography in patients with mitral valve prolapse were examined, with the costs calculated based on Medicare reimbursement. Thirteen (13.5%) patients had significant coronary artery disease. The sensitivity and specificity of exercise electrocardiography in the 71 patients with interpretable electrocardiograms were 50% and 72%, respectively. For the 73 patients who achieved >85% of maximal heart rate, 52 had interpretable exercise electrocardiograms (sensitivity 50%; specificity 69%). Exercise echocardiography had a sensitivity of 69% and a specificity of 98% in the 96 patients and a sensitivity of 82% and a specificity of 96% in patients who achieved >85% of maximal heart rate. Approaches adopting Bayes' theorem and restricting further investigation to patients with at least intermediate pretest probability of coronary disease were the least costly. When combined with exercise echocardiography as the initial test, clinical stratification was associated with a false-negative rate of 21%. The utility of exercise electrocardiography is limited by the high prevalence of resting electrocardiographic abnormalities and suboptimal sensitivity and specificity. The best balance of cost and diagnostic accuracy is to perform exercise echocardiography in patients with at least intermediate probability of coronary artery disease.

Functional myocardial perfusion abnormality induced by left ventricular asynchronous contraction: experimental study using myocardial contrast echocardiography

OBJECTIVES

The aim of this study was to clarify how myocardial perfusion is impaired by asynchronous contraction.

BACKGROUND

False septal hypoperfusion is noted in some patients with left bundle branch block.

METHODS

Eight dogs were examined with epicardial pacing at the left ventricular posterior wall, the right ventricular anterior wall and, as a control, the right atrial appendage. The pacing rate was 80, 110 and 150 beats/min (bpm). Myocardial perfusion was assessed by contrast echocardiography.

RESULTS

Left ventricular pacing at 80 and 110 bpm did not change systolic wall thickening or contrast intensity at the pacing site, although an early excitation notch was noted at the pacing site. However, at 150 bpm, systolic thickening was impaired (23.3 +/- 4.2% vs. 37.0 +/- 2.6% during atrial pacing, p < 0.05), and the peak intensity ratio of the pacing site to the ventricular septum was significantly decreased (24.1 +/- 5.7% vs. 37.0 +/- 2.8% at a pacing rate of 80 bpm, p < 0.01). The peak intensity ratio correlated with systolic wall thickening at the pacing site (y = 0.413 x -0.028, r = 0.81, p < 0.0001). However, right ventricular pacing did not change either systolic thickening or the peak intensity ratio at any pacing rate, although an early excitation notch was noted on the ventricular septum.

CONCLUSIONS

Wall motion abnormalities after early excitation vary depending on the pacing mode. When tachycardia induces regional wall motion abnormalities, the ventricular wall of the pacing site is functionally hypoperfused.

[Role of noninvasive examinations in the management of ischemic cardiopathy. V. Noninvasive examinations in the management of patients with chronic ischemic cardiopathy]

In the last few years the has been an enormous development in noninvasive testing in the field of clinical cardiology. In fact, excellent monographs on each one of these techniques have been published elsewhere, but fewer publications exist that treat the topic of their indications and use in an integrated way, except for in the most common clinical situations. In this paper, the treatment of patients who present chest pain, stable and unstable angina is discussed, including the study of postinfarction patients. Furthermore, the role of noninvasive tests in the detection of coronary heart disease in women and in patients with left bundle branch block is thoroughly analyzed; as well as their usefulness after surgical or percutaneous coronary revascularization and in patients with peripheral vascular disease.

Role of adenosine in pathogenesis of syndrome X: assessment with coronary hemodynamic measurements and thallium-201 myocardial single-photon emission computed tomography

OBJECTIVES

This study was performed 1) to examine the role of adenosine in the pathogenesis of syndrome X in patients with this syndrome and abnormal results on myocardial scintigrams during exercise, and 2) to determine the susceptibility to myocardial ischemia in this subset of patients with syndrome X.

BACKGROUND

A role for adenosine in the pathogenesis of syndrome X has recently been postulated, but there are few clinical data supporting this hypothesis.

METHODS

Exercise thallium-201 myocardial scintigraphy after intravenous administration of aminophylline, an adenosine receptor blocking agent, or saline solution and adenosine thallium-201 scintigraphy were performed in 26 patients with syndrome X. Hemodynamic variables during exercise and perfusion defect size after aminophylline and saline infusions were compared. At cardiac catheterization, coronary hemodynamic variables during separate infusions of adenosine and doubutamine were also examined and were compared among patients with abnormal or normal scintigrams and 10 control subjects.

RESULTS

Perfusion abnormalities on exercise-thallium-201 scintigraphy occurred in 14 of 26 patients with syndrome X. Intravenous infusion of aminophylline suppressed the scintigraphic perfusion defect and prolonged the time to 1-mm ST segment depression in patients with syndrome X with abnormal exercise scintigrams. Intravenous infusion of adenosine induced a perfusion defect in the same myocardial area where the perfusion defect was observed at exercise in 7 of the 14 patients with syndrome X. At cardiac catheterization, patients with syndrome X with abnormal exercise scintigrams had lower coronary flow reserve and a greater frequency of myocardial lactate production and ST segment depression in response to the infusions of adenosine and doubtamine than did the other two groups. During adenosine infusion, great cardiac vein blood flow and oxygen content were significantly increased and myocardial oxygen consumption and lactate extraction were significantly reduced from baseline without a significant increase in rate-pressure product in this subset of patients with syndrome X.

CONCLUSIONS

Patients with syndrome X with abnormal exercise scintigrams have high susceptibility to myocardial ischemia during exercise or pharmacologic stress tests, probably owing to reduced coronary flow reserve. A heterogeneous response to endogenous adenosine may contribute to scintigraphic perfusion abnormalities and myocardial ischemia during exercise in this subset of patients with syndrome X.

Tc-99m sestamibi myocardial SPECT in syndrome X

The authors reviewed the stress Tc-99m MIBI SPECT results and clinical data of 15 patients with syndrome X. The results of exercise EKG and resting left ventricular ejection fraction (LVEF) were compared with the results of Tc-99m MIBI SPECT. Of the 15 patients, 9 (60%) had a normal Tc-99m MIBI SPECT study and 6 (40%) had an abnormal Tc-99m MIBI SPECT. The authors found that 1) an abnormal Tc-99m MIBI SPECT was common in syndrome X, 2) the results of the exercise EKG were not related to perfusion defects on Tc-99m MIBI SPECT, and 3) for patients with an abnormal Tc-99m MIBI SPECT, the incidence of an abnormal resting LVEF and cardiac abnormalities were not higher than in patients with normal Tc-99m MIBI SPECT studies.

Effect of nicorandil on abnormal coronary flow reserve assessed by exercise 201Tl scintigraphy in patients with angina pectoris and nearly normal coronary arteriograms

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 myocardial 201Tl perfusion evoked by exercise. Eleven patients who had a history of typical angina, positive exercise electrocardiograms, positive 201Tl scintigraphy, nearly normal coronary arteriograms, and negative coronary vasospasm underwent exercise 201Tl 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 the 201Tl 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.

Angina pectoris and normal coronary arteriograms: clinical presentation and hemodynamic characteristics

Up to 30% of patients undergoing coronary angiography for the assessment of chest pain suggestive of coronary artery disease have "normal" studies. Several reports have indicated that a proportion of patients with angina and normal coronary arteriograms have reduced coronary flow reserve. The interpretation of these findings is, however, controversial as the majority of patients do not have definitive evidence for myocardial ischemia and have a good long-term prognosis. The clinical presentation of patients with angina and normal coronary arteriograms differs in different series and this may be just a reflection of the heterogeneous nature of the syndrome. A diversity of pathogenetic mechanisms have been postulated to explain "syndrome X" (chest pain and normal coronary arteriograms) but little is known at present about the true nature of the syndrome. The present article discusses the clinical and hemodynamic features of this intriguing disorder with particular reference to patients with syndrome X and microvascular angina.

Coronary vasodilator reserve, pain perception, and sex in patients with syndrome X

BACKGROUND

It remains unclear whether myocardial ischemia due to coronary microvascular dysfunction is the cause of chest pain in syndrome X (chest pain, ischemic-like stress ECG despite angiographically normal coronary arteries). To assess the function of the coronary microcirculation and its relation to pain perception, we measured myocardial blood flow (MBF) and coronary vasodilator reserve (CVR) in 29 patients with syndrome X and 20 matched normal control subjects.

METHODS AND RESULTS

MBF at rest and after intravenous dipyridamole (0.56 mg.kg-1 over 4 minutes) was measured using positron emission tomography with H2(15)O. CVR was calculated as MBFdipyridamole/MBFrest. ECG changes and chest pain after dipyridamole in syndrome X were compared with those in 35 patients with coronary artery disease (CAD). Resting and postdipyridamole MBFs were homogeneous throughout the left ventricle in syndrome X patients and control subjects. MBF was 1.05 (0.25), mean (SD) versus 1.00 (0.22) mL.min-1.g-1 (P = NS) at rest and 2.73 (0.81) versus 3.00 (1.00) mL.min-1.g-1 (P = NS) after dipyridamole in patients and control subjects, respectively. CVRs were 2.66 (0.76) and 3.06 (1.08) (P = NS) and after correction of resting MBF for rate-pressure product were 2.35 (0.83) and 2.34 (0.90) (P = NS) in patients and control subjects, respectively. Female syndrome X patients had higher resting MBF than males, at 1.18 (0.20) versus 0.88 (0.19) mL.min-1.g-1 (P < .001). Chest pain after dipyridamole occurred in syndrome X as frequently as in CAD (21/29 versus 22/35, P = NS).

CONCLUSIONS

When patients with syndrome X are compared with control subjects, no differences are found in MBF either at rest or after dipyridamole, despite syndrome X patients experiencing chest pain after dipyridamole to the same extent as patients with CAD. These findings, together with the absence of any relation among MBF, chest pain, and ECG changes under stress, cast further doubt on ischemia as the basis of the chest pain, at least in the majority of syndrome X patients.

Results of dobutamine stress echocardiography in patients with syndrome X

This study describes the results of Dobutamine stress echocardiography in 10 patients with Syndrome X. The diagnosis of Syndrome X was made on the basis of the presence of exertional angina, positive exercise stress test, negative ergonovine stress test and normal coronary arteries at angiography. All patients underwent Dobutamine stress echocardiography after interruption of any antianginal therapy. Dobutamine was infused starting with a dose of 5 mcg/kg/min over 3 minutes with incremental steps of 5 mcg/kg/min every 3 minutes up to a maximal dose of 40 mcg/kg/min. Two-dimensional echocardiography and 12-lead electrocardiography was monitored during the infusion of the drug. Nine patients received the maximal dose while one patient prematurely stopped the test for the occurrence of side effects. None of the ten patients developed segmental left ventricular wall motion abnormalities indicative of myocardial ischemia; ST-segment depression diagnostic for ischemia developed in 30% of patients; angina was elicited in one of these patients and in two additional patients. A hyperkinetic response to Dobutamine infusion involving all the segments of the left ventricle was observed both in patients with and without chest pain or electrocardiographic changes. In patients with Syndrome X Dobutamine induces a hyperkinetic left ventricular response indicative of normal contractile reserve despite the presence in some cases of angina and electrocardiographic signs of ischemia.

Relations between resting ventricular long axis function, the electrocardiogram, and myocardial perfusion imaging in syndrome X

OBJECTIVE

To investigate interrelations between ventricular long axis function, resting electrocardiogram, and myocardial perfusion imaging in a group of patients with syndrome X in order to define possible underlying mechanisms.

DESIGN

Prospective echocardiographic, electrocardiographic, and myocardial perfusion imaging.

SETTING

A tertiary referral centre for cardiac diseases with invasive and non-invasive facilities.

PATIENTS

50 consecutive patients with syndrome X selected on the basis of a history of angina, ST segment depression on exercise, and normal coronary arteriograms and 21 controls of similar age.

RESULTS

Long axis motion of one or both ventricles assessed by echocardiography was abnormal in 37 patients. The onset of systolic shortening was delayed by > 130 ms (upper limit of normal 95% confidence interval) in eight patients, and was associated with prolonged shortening during the isovolumic relaxation period in seven (p < 0.01) (systolic abnormalities). The onset of diastolic lengthening was delayed by > 80 ms in 20. Early diastolic peak lengthening rate was < 4.5 cm.s-1 in 13 patients, and the relative amplitude of lengthening during atrial systole was > 45% in 18. On the resting electrocardiogram septal q waves were absent in 12 patients. This was associated with long axis systolic disturbances in seven patients (p < 0.05). T waves were abnormal in 10 and associated with delayed onset of early diastolic lengthening in all (p < 0.001). Late diastolic long axis disturbances were not associated with any consistent electrocardiographic abnormality. Myocardial perfusion imaging was abnormal in six of 33 patients, four of whom had systolic abnormalities (p < 0.03). Imaging was normal in the rest, but in 13 of them long axis function was abnormal in the left side and in four it was abnormal on the right ventricle. Both electrocardiography and imaging were normal in 10 patients. No patient with an abnormal electrocardiogram or myocardial perfusion had normal long axis motion on echocardiography.

CONCLUSION

The function of the left and right ventricular long axes was abnormal in about 70% of a sample of patients with syndrome X. Systolic disturbances were consistently associated with absent septal q wave and abnormal myocardial perfusion imaging, while early diastolic disturbances correlated with T wave abnormalities. These associations suggest that the three different investigations detect related objective abnormalities in one or more subgroups of patients with syndrome X.

Left ventricular hypercontractility and ST segment depression in patients with syndrome X

OBJECTIVES

This study was designed to assess the relation between rest left ventricular function and exercise capacity in patients with syndrome X.

BACKGROUND

Clinical observation has suggested that some patients with syndrome X have a high rest left ventricular ejection fraction. In this study we determined the relation between left ventricular ejection fraction and exercise capacity and the electrocardiographic (ECG) changes that develop on exercise.

METHODS

The pattern of left ventricular function, exercise capacity and 24-h ambulatory ECG monitoring were studied in 37 patients (9 men, 28 women; mean age 52 +/- 7 years) with syndrome X (angina with normal coronary arteries and a positive exercise test result). All patients had normal findings on echocardiogram and rest ECG. All treatment was discontinued for > or = 48 h. Left ventricular ejection fraction was determined by computerized analysis of the left ventricular angiogram. In patients with syndrome X, exercise duration and heart rate were measured at 1-mm ST segment depression and at peak exercise.

RESULTS

Left ventricular hypercontractility (ejection fraction > or = 80%) was observed in 12 patients (32%) (group 1), whereas 25 patients (68%) had normal left ventricular contraction (group 2). The time to 1-mm ST depression on exercise testing was significantly earlier in group 1 than in group 2 (5.13 +/- 1.03 vs. 10.76 +/- 0.63 min, respectively, p < 0.001). The magnitude of the ST segment depression at peak exercise was significantly greater in group 1 than in group 2 (2.03 +/- 0.2 vs. 1.33 +/- 0.05 mm, respectively, p < 0.001). The mean time for ST segment depression to normalize was significantly greater in group 1 than in group 2 (4.76 +/- 0.78 vs. 3.16 +/- 0.39 min, respectively, p < 0.05). Linear regression analysis of all patients with syndrome X showed a significant correlation between exercise duration and ejection fraction (r = 0.55, p < 0.001). The mean circadian variation of heart rate and episodes of ST segment depression on 24-h ambulatory ECG monitoring were similar in the two groups of patients.

CONCLUSIONS

These findings indicate that approximately one third of patients with chest pain, normal coronary angiograms and a positive exercise test have left ventricular hypercontractility, and this is associated with the development of ST segment depression at a lower heart rate and work load and a longer time to normalization of ST segment depression after exercise.

AAI pacing mode: when is it indicated and how should it be achieved?

AAI pacing offers better hemodynamic characteristics than dual-chamber pacing and is the optimal mode for patients with sick sinus syndrome without AV conduction disorders. AAI pacing may be achieved by single-chamber atrial pacing, by programming a dual-chamber pacemaker to the AAI mode, or by programming a dual-chamber pacemaker to DDD mode with a long AV delay. The annual incidence of AV block development in patients with sick sinus syndrome is low, probably 1-5%, but there is no method of detecting patients immune or prone to future development of AV block. Chronotropic incompetence is often present in patients with sick sinus syndrome but the value of additional rate response is not yet firmly established. Our recommendations for the choice of the optimal method of pacing are discussed.

Prognosis with abnormal thallium images in the absence of significant coronary artery disease

In the presence of coronary artery disease (CAD), thallium imaging has been reported to add prognostic information that is independent of coronary anatomy. To investigate the prognostic importance of thallium imaging in the absence of significant CAD, 87 patients (65 men, 22 women) with abnormal thallium images without significant CAD were followed for a median duration of 22 months (range 11 to 50). Tomographic thallium images obtained immediately and 4 hours after exercise were interpreted by 2 experienced observers who graded thallium uptake in 24 segments in 3 views (short axis, horizontal long axis, vertical long axis) on a 5-point scale (normal; mildly, moderately, or severely reduced; absent). All patients had an abnormal thallium study, defined as a reversible defect of at least mild severity or a fixed defect of at least moderate severity seen in > or = 2 views, or a combination of these, and a coronary angiogram with stenosis not > or = 70% in diameter narrowing. Eighty-two patients had at least 1 reversible segment, and 26 patients had defects in > or = 2 coronary artery distributions. During follow-up there were no deaths or myocardial infarctions. Coronary angioplasty and bypass surgery were performed in 2 patients. Three-year survival without myocardial infarction or revascularization was 97%. Patients with abnormal thallium images in the absence of significant CAD have an excellent short-term prognosis.

Regional myocardial perfusion and glucose metabolism in experimental left bundle branch block

BACKGROUND

Several authors have reported cases in which 201Tl scintigraphy demonstrated perfusion abnormality in the septum of patients with left bundle branch block (LBBB) and normal coronary arteriogram. The mechanism of this abnormality, however, remains to be clarified.

METHODS AND RESULTS

To determine whether LBBB itself induces abnormal myocardial perfusion and ischemia and to elucidate its mechanism, we used an in vivo animal model. LBBB was induced by right ventricular pacing in 17 open-chest dogs. We examined myocardial perfusion and glucose uptake using 201Tl and 18F-labeled 2-fluoro-2-deoxy-D-glucose. 201Tl activity in the septum was reduced to 74.7 +/- 14.5% of its maximal activity, and mean activity was 86.5 +/- 5.3% in the free wall (p less than 0.05). 18F activity in the septum was also reduced compared with that in the free wall (67.4 +/- 12.1% versus 88.0 +/- 5.2%, p less than 0.05). Regional myocardial blood flow was significantly reduced in the septum compared with the free wall, averaging 0.53 +/- 0.18 ml/min/g versus 0.84 +/- 0.14 ml/min/g, respectively (p less than 0.01). Systolic thickening in the septum was reduced from 1.36 +/- 0.20 to 0.98 +/- 0.04 (p less than 0.01) after the induction of LBBB, and the intramyocardial pressure in the septum in diastolic phase, in which the major flow of left anterior descending coronary artery (LAD) exists, increased from 26.6 +/- 10.5 to 57.8 +/- 22.2 mm Hg (p less than 0.02). Mean aortic pressure, LAD flow, and lactate extraction rate showed no significant change.

CONCLUSIONS

LBBB itself may reduce myocardial perfusion and glucose uptake in the septum because of impaired systolic thickening and augmented intramyocardial pressure in the septum; however, this is not necessarily related to septal ischemia.

Dobutamine thallium myocardial perfusion tomography

Dobutamine has favorable properties for the pharmacologic manipulation of myocardial oxygen demand in the provocation of ischemia during the investigation of coronary artery disease. The value of dobutamine infusion for thallium myocardial perfusion tomography was assessed in 50 patients with exertional chest pain undergoing coronary arteriography. Dobutamine was infused in 5-min stages at incremental rates from 5 to 20 micrograms/kg per min or until limited by symptoms. The myocardium was divided into nine segments for analysis of perfusion. Thirty-nine of 40 patients with coronary artery disease had a reversible perfusion defect demonstrated by dobutamine thallium tomography (sensitivity 97%) and 8 of 10 patients with normal coronary arteries had normal myocardial perfusion (specificity 80%). These values were significantly better than the sensitivity and specificity of exercise electrocardiography (78% and 44%, respectively; p less than 0.01). There was a significant relation between the mean number of segments with abnormal perfusion and the number of diseased coronary vessels (0.6, 2.6, 4.4 and 6 segments in zero-, one-, two- and three-vessel disease, respectively; p less than 0.001). There was also a significant relation between the maximal tolerated dose of dobutamine and the treadmill exercise time (r = 0.56, p less than 0.001), but a wide range of exercise times was achieved in the 15- and 20-micrograms/kg per min groups, principally because of exercise limitation by noncardiac symptoms. Dobutamine infusion was well tolerated in all patients, including six with asthma. There were no significant arrhythmias or limiting symptoms other than chest pain.(ABSTRACT TRUNCATED AT 250 WORDS)

Stable angina pectoris: 2. Cardiac evaluation and diagnostic testing

The examination of a patient with angina pectoris begins with clinical assessment. Certain clinical findings that are present only during angina, such as mitral regurgitation due to ischemia-induced papillary muscle dysfunction, may clarify an otherwise uncertain diagnosis. Electrocardiography is a useful and relatively inexpensive test for detecting evidence of ischemia in patients with suspected angina. The presence of cardiomegaly on the chest roentgenogram has adverse prognostic implications. Exercise stress testing is important in the diagnosis of coronary artery disease and also provides prognostic information. Patients should be classified into high-, intermediate-, or low-risk subsets by noninvasive techniques. Although relatively easy and inexpensive, treadmill exercise stress testing cannot be performed in all patients, and sometimes it will yield equivocal results. In these cases, radionuclide testing (with thallium scintigraphy or radionuclide angiography) can be helpful and also can identify high-risk patients. Some patients will require coronary angiography.

Quantitative analysis of myocardial ischaemia on end-diastolic thallium 201 perfusion images

ECG gating of images with thallium 201 (201Tl) may improve the representation of myocardial perfusion by allowing isolation of the end-diastolic (ED) portion of the cardiac cycle. To characterize this phenomenon, circumferential distribution profiles for ED and conventional total-cycle images (TC) with 201Tl were analysed after summing ECG gated acquisitions; redistribution was defined as net washing of 201Tl for specific myocardial segments visualized on the left anterior oblique images. Scintigraphic data were compared with the presence of coronary stenoses in 150 patients. ED images had relatively less activity in the inferoseptal and inferoapical region than TC profiles. The ED mode of washout analysis provided more frequent confirmation of visually suggested redistribution than did the TC mode (84% incidence of net wash in for ED, 69% for TC). ED analysis showed a higher incidence of net 201Tl wash in in relation to critical circumflex and left anterior descending artery lesions, but yielded a similar overall performance to TC analysis in distinguishing patients with diseased coronary arteries from normal subjects. Thus, in selected cases, analysis of ED images could assist in confirming 201Tl redistribution.

Exercise thallium-201 scintigraphy in the localization of myocardial ischaemia

We performed a retrospective study in order to study the ability of thallium-201 exercise scintigraphy to detect and to localize coronary artery perfusion defects (in comparison with a recent coronary angiogram). We studied 81 patients (67 males); their average age was 52.3 years (men 50.5 and women 54.1 years). They performed a pulse-conducted cycle exercise test, and 2 min before end of exercise 75 MBq of thallium-201 was infused intravenously, and tomographic images were reconstructed by using a Siemens-Rota SPECT gamma camera immediately and 4 h after exercise. The thallium-201 uptake defects were attributed to different coronary arteries, and the results were compared with a coronary angiogram made afterwards in 48 patients. The groups of one-, two- and three-vessel disease were 27, 21, and 21 patients, and only 12 patients did not have significant (over 50%) stenoses. The latter had the highest ejection fraction and working capacity. Sensitivity of thallium-201 exercise scintigraphy was 65%, whereas that of exercise ECG was 41% in patients with a low ejection fraction, while in the whole material the sensitivity of thallium-201 scintigraphy was 91% and that of exercise ECG was 54%. A stenosis in the right coronary artery was best localized by the thallium-201 scintigram (86% correctly); a stenosis in the left anterior descending artery was localized correctly in 75% of the cases, but a stenosis in left circumflex artery was localized correctly only in 44%. We conclude that exercise thallium-201 scintigraphy is a useful method not only in detecting but also in localizing coronary artery disease.

Myocardial 201Tl washout after combined dipyridamole submaximal exercise stress: reference values from different patient groups

Dipyridamole stress is favorable in patients unable to exercise maximally for 201Tl myocardial scintigraphy. Aside from an analysis of uptake defects, proper washout analysis can be limited by heart rate variations when isolated dipyridamole stress is used. Heart rate standardized 201Tl washout kinetics after a combined dipyridamole and submaximal exercise stress protocol (CDSE), feasible in elderly patients as well as in patients with peripheral artery disease, were therefore studied to investigate the 201Tl washout after CDSE in differently defined patient groups: Group I comprised 19 patients with documented heart disease and angiographically excluded coronary artery disease (CAD); group II contained 17 patients with a very low likelihood of CAD determined by both normal exercise radionuclide ventriculography and normal 201Tl uptake. Group III comprised 56 patients with a 50% pretest likelihood of CAD but normal 201Tl uptake. Mean washout values were nearly identical in all groups. Despite similar uptake patterns, however, washout standardized by CDSE was significantly lower than the normal washout values after maximal treadmill exercise. Thus an obviously lower 201Tl washout after CDSE than after maximal treadmill exercise must be considered if washout analysis criteria after dipyridamole are applied to evaluate ischemic heart disease. Nevertheless, heart rate elevation achieved by additional submaximal exercise stress seems necessary, adequate and clinically safe for standardisation of washout analysis in dipyridamole 201Tl scintigraphy.

Left ventricular dysfunction in patients with angina pectoris and normal coronary angiograms

Left ventricular function was assessed in 201 patients who presented with angina pectoris and who were subsequently found to have completely normal coronary angiograms. Left ventricular angiograms from 187 patients were suitable for analysis of systolic regional wall motion; 121 were found to be normal and 66 had a total of 115 hypokinetic segments. Patients with hypokinesia had a significantly higher left ventricular end systolic volume and a significantly lower left ventricular ejection fraction and exercise capacity than those in whom regional wall motion was normal. Thirty one per cent of patients with normal wall motion and 30% of those with hypokinesia had a resting left ventricular end diastolic pressure greater than 15 mm Hg. There were significantly more smokers in the group with hypokinetic segments. Thus of patients with angina and normal coronary angiograms, 25% had evidence of left ventricular systolic dysfunction, 20% had evidence of diastolic dysfunction, and 11% had evidence of both systolic and diastolic dysfunction. The results suggest that smoking may be associated with left ventricular regional wall motion abnormalities.

The ST segment/heart rate slope as a predictor of coronary artery disease: comparison with quantitative thallium imaging and conventional ST segment criteria

The ST segment shift relative to exercise-induced increments in heart rate, the ST/heart rate slope (ST/HR slope), has been proposed as a more accurate ECG criterion for diagnosing significant coronary artery disease (CAD). Its clinical utility, with the use of a standard treadmill protocol, was compared with quantitative stress thallium (TI) and standard treadmill criteria in 64 unselected patients who underwent coronary angiography. The overall diagnostic accuracy of the ST/HR slope was an improvement over TI and conventional ST criteria (81%, 67%, and 69%). For patients failing to reach 85% of their age-predicted maximal heart rate, its diagnostic accuracy was comparable with TI (77% and 74%). Its sensitivity in patients without prior myocardial infarctions was equivalent to that of thallium (91% and 95%). The ST/HR slope was directly related to the angiographic severity (Gensini score) of CAD in patients without a prior infarction (r = 0.61, p less than 0.001). The ST/HR slope was an improved ECG criterion for diagnosing CAD and compared favorably with TI imaging.

The role of transdermal nitroglycerin in the treatment of coronary heart disease

Nitroglycerin has long been a mainstay of the treatment of ischemic cardiac pain. The introduction of transdermal formulations and in particular the development of controlled methods of delivery have been responsible for the renaissance of clinical interest in this simple and effective treatment. The pathophysiologic abnormality accompanying myocardial ischemia affords a natural theater for the exhibition of the therapeutic utility of these preparations and methods. The means whereby nitrates induce relaxation of vascular smooth muscle are not entirely clear, but their pharmacodynamic activities are perfectly plain. In the doses used in clinical practice, nitrates exert their predominant hemodynamic effects and therapeutic benefits through their peripheral vasodilator activities. This is particularly marked in veins, although in higher doses nitrates also dilate the larger systemic and coronary arteries. Criticisms of the efficacy of transdermal formulations of nitrates in the treatment of angina pectoris have arisen largely from uncritical acceptance of a small number of studies of questionable methodologic validity. Large-scale general practice studies have invariably found that transdermal nitrate delivery systems improve the quality of life in ambulant patients: anginal attacks are reduced with a minimum of side effects. The widespread acceptance of this novel form of drug delivery has stimulated its application in other therapeutic avenues. The efficacy of transdermal nitroglycerin in the suppression of silent ischemic attacks has been demonstrated. The maintenance of benefit initiated by intravenous nitroglycerin in patients with unstable angina also broadens the use of this method of nitrate delivery. In patients with acute myocardial infarction, whether complicated by left ventricular failure or not, the nitrates, and transdermal nitroglycerin in particular, appear to hold considerable promise. Improvement of hemodynamic abnormalities may cause reduction in infarct size and fewer life-threatening arrhythmias. Even survival may be extended. The utility of transdermal nitrates in the treatment of severe chronic heart failure is less certain. But the use of higher doses and an interval regimen of administration may hold promise for such patients. Naturally, more information is required before the overall therapeutic profile of this new method of controlled nitroglycerin delivery across the whole spectrum of coronary heart disease can be fully described. Fortunately, the high level of efficacy and safety of transdermal nitroglycerin demonstrated in the majority of reported studies encourages the pursuit of such an important therapeutic target.

Abnormal coronary flow reserve and abnormal radionuclide exercise test results in patients with normal coronary angiograms

Coronary flow reserve, exercise thallium-201 scintigraphy and exercise radionuclide ventriculography were compared in 18 patients with chest pain and angiographically normal coronary arteries. Regional exercise thallium-201 perfusion was abnormal in three patients, regional exercise wall motion was abnormal in three other patients and results of both tests were abnormal in one additional patient. Left ventricular ejection fraction responses were abnormal in five of these seven patients. The coronary flow reserve of arterial distributions with abnormal perfusion or regional dysfunction was significantly lower than that of distributions associated with normal radionuclide results (1.42 +/- 0.23 versus 2.58 +/- 0.83, p less than 0.001). All patients with abnormal scintigraphic results had low coronary flow reserve (less than 1.95) in at least one distribution. Perfusion abnormalities appeared to be more localized in the arterial distributions with the lowest flow reserve. Only two patients had low flow reserve (less than 1.95) with normal scintigraphic results; both were hypertensive. These data suggest that abnormal exercise scintigraphic findings in patients with angiographically normal coronary arteries and chest pain are indicative of true blood flow or perfusion abnormalities.

A 201T1 perfusion defect in a case with rate-dependent left bundle-branch block (LBBB)

We present a case report of a 67-year-old woman with rate-dependent left bundle-branch block (LBBB). Although coronary angiography demonstrated no significant obstructive lesions, a reversible focal defect developed on 201T1 myocardial scintigraphy when LBBB was induced by right-atrial pacing.