Usefulness of a high-dose dipyridamole-echocardiography test for diagnosis of syndrome X

Diagnostic approach for coronary microvascular dysfunction in patients with chest pain and no obstructive coronary artery disease

A large number of studies has demonstrated that abnormalities of coronary microcirculation may be responsible for both acute and chronic cardiac ischemic syndromes. In clinical practice the microvascular origin of myocardial ischemia and angina is usually considered in patients who are found to have normal or near-normal coronary arteries at angiography. In this article, we review the diagnostic approach to patients with suspected coronary microvascular dysfunction as a cause of ischemic syndromes and also suggest a classification of chronic and acute microvascular coronary ischemic syndrome, including myocardial infarction with normal coronary arteries.

Diagnostic Approach to Patients with Stable Angina and No Obstructive Coronary Arteries

The diagnosis of microvascular angina (MVA) is usually considered in patients presenting with angina symptoms and evidence of MI on non-invasive stress tests but normal coronary arteries at angiography. A definitive diagnosis of MVA, however, would require the presence of coronary microvascular dysfunction. Several invasive (e.g. intracoronary Doppler wire recording and thermodilution) and non-invasive (e.g. PET, cardiac MRI, transthoracic Doppler echocardiography) methods can be applied to obtain a diagnosis. Both endothelium-dependent and -independent coronary microvascular dilator function, as well as increased microvascular constrictor activity, should be investigated. The main issues in the assessment of clinical and diagnostic findings in patients with suspected MVA are discussed and a diagnostic approach is suggested.

[The Clinical use of Stress Echocardiography in Ischemic Heart Disease Cardiovascular Ultrasound (2017)15:7. Translation authors: Arystan A.Zh., Fettser D.V.]

Stress echocardiography is an established technique for the assessment of extent and severity of coronary artery disease. The combination of echocardiography with a physical, pharmacological or electrical stress allows detecting myocardial ischemia with an excellent accuracy. A transient worsening of regional function during stress is the hallmark of inducible ischemia. Stress echocardiography provides similar diagnostic and prognostic accuracy as radionuclide stress perfusion imaging or magnetic resonance, but at a substantially lower cost, without environmental impact, and with no biohazards for the patient and the physician. The evidence on its clinical impact has been collected over 35 years, based on solid experimental, pathophysiological, technological and clinical foundations. There is the need to implement the combination of wall motion and coronary flow reserve, assessed in the left anterior descending artery, into a single test. The improvement of technology and in imaging quality will make this approach more and more feasible. The future issues in stress echo will be the possibility of obtaining quantitative information translating the current qualitative assessment of regional wall motion into a number. The next challenge for stress echocardiography is to overcome its main weaknesses: dependence on operator expertise, the lack of outcome data (a widespread problem in clinical imaging) to document the improvement of patient outcomes. This paper summarizes the main indications for the clinical applications of stress echocardiography to ischemic heart disease.

The clinical use of stress echocardiography in ischemic heart disease

Stress echocardiography is an established technique for the assessment of extent and severity of coronary artery disease. The combination of echocardiography with a physical, pharmacological or electrical stress allows to detect myocardial ischemia with an excellent accuracy. A transient worsening of regional function during stress is the hallmark of inducible ischemia. Stress echocardiography provides similar diagnostic and prognostic accuracy as radionuclide stress perfusion imaging or magnetic resonance, but at a substantially lower cost, without environmental impact, and with no biohazards for the patient and the physician.

The evidence on its clinical impact has been collected over 35 years, based on solid experimental, pathophysiological, technological and clinical foundations. There is the need to implement the combination of wall motion and coronary flow reserve, assessed in the left anterior descending artery, into a single test. The improvement of technology and in imaging quality will make this approach more and more feasible. The future issues in stress echo will be the possibility of obtaining quantitative information translating the current qualitative assessment of regional wall motion into a number. The next challenge for stress echocardiography is to overcome its main weaknesses: dependance on operator expertise, the lack of outcome data (a widesperad problem in clinical imaging) to document the improvement of patient outcomes. This paper summarizes the main indications for the clinical applications of stress echocardiography to ischemic heart disease.

Role of echocardiography in the management of cardiac disease in women

The widespread use of echocardiography has contributed to the early recognition of several distinct cardiac diseases in women. During pregnancy, safe monitoring of the disease process, as well as a better understanding of hemodynamics, is possible. During the use of potentially cardiotoxic drugs for breast cancer chemotherapy, echocardiographic patient monitoring is vital. Compared to men, the addition of an imaging modality to routine electrocardiogram monitoring during stress testing is more informative for diagnosing coronary disease in women. This review briefly discusses the role of echocardiography in the management of several women-specific cardiac diseases where echocardiography plays a pivotal role in disease management.

Management of microvascular angina pectoris

Microvascular angina (MVA) is defined as angina pectoris caused by abnormalities of small coronary arteries. In its most typical presentation, MVA is characterized by angina attacks mainly caused by effort, evidence of myocardial ischemia on non-invasive stress tests, but normal coronary arteries at angiography. Patients with stable MVA have excellent long-term prognoses, but often present with persistent and/or worsening of angina symptoms. Treatment of MVA is initially based on standard anti-ischemic drugs (beta-blockers, calcium antagonists, and nitrates), but control of symptoms is often insufficient. In these cases, several additional drugs, with different potential anti-ischemic effects, have been proposed, including ranolazine, ivabradine, angiotensin-converting enzyme (ACE) inhibitors, xanthine derivatives, nicorandil, statins, alpha-blockers and, in perimenopausal women, estrogens. In patients with 'refractory MVA', some further alternative therapies (e.g., spinal cord stimulation, pain-inhibiting substances such as imipramine, rehabilitation programs) have shown favorable results.

Altered transmural contractility in postmenopausal women affected by cardiac syndrome X

BACKGROUND

Cardiac syndrome X (CSX) is characterized by typical angina and abnormal exercise test results, with normal coronary arteries. Cardiovascular magnetic resonance imaging has shown subendocardial hypoperfusion in patients with CSX after adenosine. The aim of this study was to investigate the contribution of separate myocardial layers to global function under stress in women with CSX.

METHODS

Twenty-two postmenopausal women with CSX were studied and compared with 20 healthy women matched for age and body mass index. All subjects underwent clinical evaluations and exercise echocardiography. Left ventricular systolic and diastolic parameters were evaluated at rest and at peak exercise. Layer-specific global longitudinal strain (GLS) and strain rate (SR) were assessed from the endocardium, midmyocardium, and epicardium using two-dimensional speckle-tracking echocardiography.

RESULTS

All subjects showed normal contractile function at rest and at peak exercise. Significant increases in GLS and SR in all myocardial layers were observed at peak exercise in the control group, whereas patients with CSX showed significantly lower increases in endocardial GLS and SR compared with the control group (endocardial ΔSR, 0.17 ± 0.19 vs 0.33 ± 0.13 [P < .01]; endocardial ΔGLS, 1.33 ± 2.93 vs 6.64 ± 2.62 [P < .001]). Moreover, significantly impaired diastolic function (ΔE', 1.1 ± 3.3 vs 4.0 ± 2.03) was observed in patients with CSX.

CONCLUSIONS

The results of this study show subendocardial impairment of contractile function during exercise in patients with CSX, confirming the existence of reduced myocardial perfusion reserve in patients with CSX and suggesting layer-targeted exercise echocardiography as a sensitive diagnostic tool in the assessment of suspected CSX.

Additive prognostic value of coronary flow reserve in patients with chest pain syndrome and normal or near-normal coronary arteries

In patients with angiographically normal coronary arteries and chest pain, pharmacologic stress echocardiography can identify a subgroup of patients with a less benign prognosis. Coronary flow reserve (CFR) in the left anterior descending artery (LAD) can currently be combined with wall motion analysis during vasodilator stress echocardiography. The aim of this study was to assess the prognostic value of CFR response in patients with normal coronary arteries and normal wall motion during stress. We selected 394 patients (171 men, 61 +/- 11 years of age) who underwent dipyridamole stress echocardiography (0.84 mg/kg over 6 minutes) with 2-dimensional echocardiography and CFR evaluation of the LAD by Doppler. All had angiographically nonsignificant (<50% quantitatively assessed) stenosis in any major vessel, normal left ventricular function (wall motion score index 1), and test negativity for conventional wall motion criteria. Images were independently read by a core laboratory for wall motion and a core laboratory for CFR. Mean CFR was 2.5 +/- 0.6 and 87 patients (22%) had an abnormal CFR <2. During a median follow-up of 51 months, 31 events occurred, namely 4 deaths and 27 nonfatal myocardial infarctions (3 ST-elevated myocardial infarctions and 24 non-ST-elevated myocardial infarctions). Kaplan-Meier survival estimates for hard events showed a better outcome for those patients with a normal CFR compared with those with an abnormal CFR (96% vs 55%, p = 0.001, at 48 months of follow-up). In conclusion, in patients with angiographically normal or near-normal coronary arteries and preserved at-rest regional and global left ventricular function at baseline and during stress, CFR adds incremental value to the prognostic stratification achieved with clinical and angiographic data.

Stress echocardiography expert consensus statement: European Association of Echocardiography (EAE) (a registered branch of the ESC)

Stress echocardiography is the combination of 2D echocardiography with a physical, pharmacological or electrical stress. The diagnostic end point for the detection of myocardial ischemia is the induction of a transient worsening in regional function during stress. Stress echocardiography provides similar diagnostic and prognostic accuracy as radionuclide stress perfusion imaging, but at a substantially lower cost, without environmental impact, and with no biohazards for the patient and the physician. Among different stresses of comparable diagnostic and prognostic accuracy, semisupine exercise is the most used, dobutamine the best test for viability, and dipyridamole the safest and simplest pharmacological stress and the most suitable for combined wall motion coronary flow reserve assessment. The additional clinical benefit of myocardial perfusion contrast echocardiography and myocardial velocity imaging has been inconsistent to date, whereas the potential of adding - coronary flow reserve evaluation of left anterior descending coronary artery by transthoracic Doppler echocardiography adds another potentially important dimension to stress echocardiography. New emerging fields of application taking advantage from the versatility of the technique are Doppler stress echo in valvular heart disease and in dilated cardiomyopathy. In spite of its dependence upon operator's training, stress echocardiography is today the best (most cost-effective and risk-effective) possible imaging choice to achieve the still elusive target of sustainable cardiac imaging in the field of noninvasive diagnosis of coronary artery disease.

Exercise-induced intra-ventricular gradients as a frequent potential cause of myocardial ischemia in cardiac syndrome X patients

Background

The development of intra-ventricular gradients (IVG) during dobutamine or exercise stress is not infrequent, and can be associated to symptoms during stress.

The purpose of this study was to assess the occurrence of IVG during exercise stress echocardiography in cardiac syndrome X patients.

Methods

We prospectively evaluated 91 patients (pts) mean aged 51 ± 12 years (age ranged 20 to 75 years old), 44 of whom were women. All pts had angina, positive exercise ECG treadmill testing, normal rest echocardiogram and no coronary artery disease on coronary angiogram (cardiac X syndrome). After complete Doppler echocardiographic evaluation with determination of left ventricular outflow tract index (LVOTi), relative left ventricular wall thickness (RLVWT) and left ventricular end-diastolic volume index (LVDVi), all patients underwent stress echocardiography with two-dimensional and Doppler echographic evaluation during and after treadmill exercise.

Results

For analysis purpose patients were divided in 2 groups, according to the development of IVG. Doppler evidence of IVG was found in 33 (36%) of the patients (Group A), with mean age 47 ± 14 years old (age ranged 20 to 72 years) and with a mean end-systolic peak gradient of 86 ± 34 mmHg (ranging from 30 to 165 mmHg). The IVG development was accompanied by SAM of the mitral valve in 23 pts. Three of these pts experienced symptomatic hypotension. Ten were women (30% pts). 58 pts in group B, 34 of whom were women (59%) (p = 0,01 vs group A), mean aged 53,5 ± 10,9 years old (age ranged 34 to 75 years) (p = 0,03 vs group A), did not develop IVG. LVOTi was 10,29 ± 0,9 mm/m² in group A and 11,4 ± 1 mm/m² in group B (p < 0,000); RLVWT was 0,36 ± 0,068 in group A and 0,33 ± 0,046 in group B (p < 0,01); LVDVi was 44,8 ± 10 ml/m² in group A and 56 ± 11,6 ml/m² in group B (p = 0,000).

Conclusion

1. A significant number of patients with cardiac X syndrome developed IVG during upright exercise in treadmill. These pts (group A) are mainly males and younger than those who did not develop IVG.

2. The development of IVG and mitral valve SAM on exertion seems to be associated with ST segment downsloping during stress testing in patients without epicardial coronary disease.

3. The development of IVG and mitral valve SAM seems to be associated with lower LVOTi, lower LVDVi and higher RLVWT.

Usefulness of a novel ultrasound transducer for continuous monitoring treadmill exercise echocardiography to assess coronary artery disease

BACKGROUND

The feasibility of a novel ultrasound probe, which can be attached to the left ventricular (LV) apex chest wall and allows free rotation around its long axis direction for the continuous monitoring of LV wall motion, was tested.

METHODS AND RESULTS

There were 36 subjects who had coronary artery disease (CAD). By attaching a novel ultrasound probe to the chest wall, the LV apical views were recorded during treadmill exercise stress echocardiography (Echo). The continuous monitoring of LV wall motion was satisfactorily feasible in 30 of 36 patients. The visualization rate of the overall LV segments was higher at rest (90%) compared to that during peak exercise (77%). The segments were better visualized in apical portions (90-100%) than in mid (77-96%) or basal portions (68-87%). The sensitivity, specificity, and accuracy for detecting CAD were 61, 100 and 77%, respectively. The wall motion score index 3 and 6 min after exercise decreased significantly compared to those at peak exercise. The number of segments with dyssynergy was highest at the peak exercise. Ischemic ST-T depression on electrocardiography was observed only at peak stress periods.

CONCLUSIONS

Continuous monitoring treadmill exercise Echo using a novel ultrasound probe seems feasible for the non-invasive and physiological assessment of CAD.

[Cardiovascular syndrome X and endothelial dysfunction]

Up to 30% of patients with chest pain who undergo coronary arteriography, have completely normal coronary angiograms. The subgroup with typical angina and a positive response to stress testing is generally included under the diagnosis of cardiovascular syndrome X. Several causes and mechanisms have been investigated in the past twenty years, to explain both chest pain and ischemic angina-like ST segment depression that are commonly observed in these patients. Clinical and pathogenic heterogeneity appears to be the main features of the syndrome. Among the suggested pathophysiological mechanisms, endothelial dysfunction of the coronary microcirculation features prominently. In this review, we present the available evidence regarding endothelial dysfunction in cardiovascular syndrome X.

Diagnosis of myocardial ischemia in hypertensive patients

Arterial hypertension can provoke a reduction in coronary flow reserve through several mechanisms that are not mutually exclusive (i.e. epicardial coronary artery disease (CAD), left ventricular hypertrophy and structural and/or functional microvascular disease). These different targets of arterial hypertension should be explored with different diagnostic markers. In fact, stress-induced wall motion abnormalities are highly specific for angiographically assessed epicardial CAD, whereas ST segment depression and/or myocardial perfusion abnormalities are frequently found with angiographically normal coronary arteries associated with left ventricular hypertrophy and/or microvascular disease. Exercise-electrocardiography stress test can be used to screen patients with negative maximal test due to its excellent negative predictive value, which is high and comparable in normotensives and hypertensives. When exercise-electrocardiography stress test is positive (or uninterpretable or ambiguous), an imaging stress-echo test is warranted for a reliable identification of significant, prognostically malignant epicardial CAD in view of an ischemia-guided revascularization.

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.

Dipyridamole stress echocardiography

Dipyridamole stress is the forerunner and prototype of pharmacological stress echo tests in the diagnosis of coronary artery disease. The safety of this test has been conclusively demonstrated as a result of extensive experience in large-scale multicenter projects. The diagnostic accuracy of dipyridamole stress echo is comparable to dobutamine and largely a function of the employed dose. Higher dosages (up to 0.84 mg/kg) are being required to achieve good sensitivity. The prognostic value has been shown to be independent and additive to clinical, exercise echocardiogram, and angiographic data. The test positive response should be titrated on the basis of severity, extent, and timing of induced dyssynergy with low positivity being associated to more anatomically and functionally severe forms of disease. Multicenter, randomized, prospective, international studies on cost-effectiveness directly comparing a noninvasive strategy centered on stress echo versus an invasive strategy centered on coronary angiography are currently ongoing.

Transesophageal echocardiography with stress for the evaluation of patients with coronary artery disease

Echocardiography permits a comprehensive assessment of resting regional and global left ventricular function, the presence and extent of inducible myocardial ischemia, and the identification of myocardial viability. Accordingly, stress echocardiography has become a valuable tool for the evaluation of patient with known or suspected coronary artery disease. In some patients however, a suboptimal transthoracic echocardiogram may limit the performance of interpretation of the test. Transesophageal echocardiography in combination with stress has been recently used for the evaluation of patients with coronary artery disease. This technique is semi-invasive, more time-consuming, and requires a greater degree of expertise on the part of the personnel assisting with the test. In general, complications and side-effects are self-limited and rarely affect the diagnostic accuracy of the test. Based on its ability to provide high quality images, transesophageal stress echocardiography should be considered in patients who have suboptimal transthoracic ultrasound window for the quantitative assessment of myocardial wall-thickening in clinical investigations of ischemic heart disease.

Abnormal cardiac nerve function in syndrome X

Syndrome X is likely to be caused by a dysfunction of small coronary arteries. Several authors suggested that an increased adrenergic activity could be involved in the pathogenesis of syndrome X, but studies investigating this topic by indirect methods led to conflicting results. We directly investigated cardiac sympathetic nerve function in syndrome X by myocardial radionuclide studies with 123I-metaiodobenzylguanidine (MIBG). Twelve syndrome X patients and 10 healthy controls were enrolled in the study. Cardiac MIBG uptake was assessed calculating the heart/mediastinum (H/M) ratio and a semiquantitative MIBG uptake score. Cardiac MIBG images were normal in all but 1 of controls (10%). Conversely, abnormalities in cardiac MIBG uptake were found in 9 syndrome X patients (75%, p < 0.01). In 5 patients the heart was totally or almost totally invisible on radionuclide MIBG images, while regional defects were found in other 4 patients. The H/M ratio was lower and cardiac MIBG uptake score strikingly higher in syndrome X patients. At 3 hours the H/M ratio was 1.70 +/- 0.6 in patients and 2.19 +/- 0.3 in controls (p = 0.03), while MIBG uptake score was 36.7 +/- 31 and 4.0 +/- 2.5 (p = 0.003) in the 4 groups, respectively. There were no differences between patients and controls in lung and salivary MIBG uptake. Reversible perfusion defects on stress thallium scintigraphy were found in 5 syndrome X patients (45%), all of whom also had abnormal MIBG scintigrams, while all 3 patients with normal MIBG scintigraphy also had normal thallium images. Thus, the function of efferent cardiac adrenergic nerve fibers is strongly impaired in the majority (i.e., 75%) of syndrome X patients. This abnormal function likely contributes significantly to the pathophysiologic and clinical features of syndrome X. We speculate that also the increased perception of cardiac pain reported in these patients could be an expression of the abnormal function of cardiac nerves, reflecting alterations of afferent nociceptive cardiac nerve fibers, as the abnormalities in MIBG uptake reflect alterations of efferent cardiac adrenergic nerve fibers.

Significance of myocardial ischemic electrocardiographic changes during dipyridamole stress echocardiography

The aim of this study was to assess the diagnostic and prognostic value of the presence and characteristics of ischemic electrocardiographic (ECG) changes during dipyridamole stress echocardiography. The ECG response in 178 patients with echocardiographic evidence of myocardial ischemia during dipyridamole stress testing was analyzed. ECG changes occurred in 105 patients (59%). Patients with ECG changes had a higher incidence of echocardiographic signs of ischemia at a low dose than patients with an unchanged electrocardiogram (50% vs 23%; p = 0.0002). Three-vessel and/or left main coronary artery disease (CAD) was found in 41% of patients with and in 21% of patients without ECG changes (p = 0.029). During follow-up (33 +/- 19 months), 30 cardiac events occurred: 10 deaths, 6 infarctions, and 14 unstable anginas. Coronary revascularization was performed in 48 patients with and in 17 patients without ECG changes (p = 0.0022). The univariate predictors of cardiac events were: presence of ischemia in > or =4 ECG leads (p = 0.0004), echocardiographic evidence of ischemia at a low dose (p = 0.0062), ST-segment shift on precordial leads (p = 0.0094), family history of CAD (p = 0.0115), coexistence of > or =3 cardiovascular risk factors (p = 0.0156), ST-segment depression (p = 0.0172), and ECG changes during testing (p = 0.0335). At Cox analysis, occurrence of ischemia at a low dose (odds ratio 3.0; 95% confidence interval 1.3 to 6.8) and the presence of ischemia in > or =4 ECG leads (odds ratio 3.5; 95% confidence interval 1.3 to 9.3) had an independent prognostic importance. In conclusion, the presence and characteristics of ischemic ECG changes are associated with more extensive CAD and worse prognostic outlook than are echocardiographic changes alone during dipyridamole stress echocardiography.

The "warm-up" phenomenon occurs in patients with chronic stable angina but not in patients with syndrome X

Most patients with chronic stable angina show an improvement in ischemic threshold when a second exercise test is performed a few minutes after a first positive test. In this study we evaluated whether this "warm-up" phenomenon also occurs in patients with syndrome X. We performed 2 consecutive exercise tests in 14 patients with chronic stable angina and 11 patients with syndrome X. The second exercise test was performed after 10 minutes from the end of the first one, always after complete recovery to baseline of ST segment. In patients with stable angina, heart rate (108+/-18 vs 99+/-16 beats/min, p = 0.005), rate-pressure product (17,020+/-4,541 vs 15,215+/-3,734 beats/min x mm Hg, p = 0.028), and exercise time (587+/-297 vs 444+/-244 seconds, p = 0.002) at 1-mm ST depression were higher in the second test than in the first one and a significant improvement in these parameters during the second test was also observed at peak exercise. Conversely, in patients with syndrome X, there were no significant differences between the 2 tests in heart rate (128+/-18 vs 131+/-23 beats/min), rate-pressure product (19,922+/-5,153 vs 19,390+/-5,654 beats/min x mm Hg), and exercise time (592+/-243 vs 566+/-228 seconds) at 1-mm ST-segment depression. Similarly, in this group of patients, no significant differences in exercise variables between the 2 tests were observed at peak exercise. Thus, unlike patients with chronic stable angina, patients with syndrome X have no evidence of warm-up in response to repeated exercise testing.

Left ventricular diastolic filling dynamics during isometric exertion in syndrome X assessed with Doppler flowmetry

To study left ventricular diastolic properties in syndrome X, we analyzed transmitral filling dynamics during handgrip exertion. In 14 normal subjects (N), 17 with syndrome X (Syn X), 16 with single-vessel disease (SVD), and 8 with multiple-vessel disease (MVD), transmitral inflow was recorded at baseline and during handgrip (50% of maximal effort for one minute) using pulsed Doppler echocardiography. We measured early diastolic (E) and late atrial (A) inflow velocities, A/E ratio and percent change of A/E from baseline (%A/E). Blood pressure and heart rate increased to the same degree in each group during handgrip. In normal subjects, E did not change with handgrip; A (51 +/- 10 vs 54 +/- 11 cm/sec, P < 0.05) and A/E (1.16 +/- 0.22 vs 1.25 +/- 0.33, P < 0.05) increased minimally. In Syn X subjects, E decreased (51 +/- 10 vs 38 +/- 10 cm/sec, P < 0.0001), A increased (52 +/- 11 vs 60 +/- 14 cm/sec, P < 0.005), and A/E increased markedly (1.07 +/- 0.31 vs 1.68 +/- 0.51, P < 0.0001). The %A/E in Syn X and MVD were significantly larger than that in SVD and N (Syn X: 58 +/- 29%; MVD: 45 +/- 25%; SVD: 22 +/- 21%; N: 8 +/- 13%). Handgrip-induced changes in diastolic filling in syndrome X and are similar to those in MVD and more marked than in SVD. These changes are consistent with impaired ventricular relaxation and support a generalized left ventricular (LV) abnormality in syndrome X.

ECG in stress testing: child of a lesser diagnostic god?

When new technologies are added to the previously existing ones, the latter can be prematurely discarded and judged obsolete not only on the basis of rational scientific facts, but also on irrational trends. Old techniques, like electrocardiography, suffer from diagnostic ambiguities that can be solved by combination with a cardiac imaging technique, like stress echocardiography. ECG monitoring during all forms of stress testing can still offer surprising dividends for a better understanding of the complex physiology of coronary artery disease, a better clinical characterization of patients with microvascular angina, and may serve as an important adjunct marker to cardiac imaging techniques.

Abnormal cardiac adrenergic nerve function in patients with syndrome X detected by [123I]metaiodobenzylguanidine myocardial scintigraphy

BACKGROUND

Previous studies have suggested that an abnormal cardiac adrenergic tone may have a pathophysiological role in syndrome X (effort angina, positive exercise testing, angiographically normal coronary arteries).

METHODS AND RESULTS

To evaluate cardiac adrenergic nerve function, we performed [123I]metaiodobenzylguanidine (MIBG) myocardial scintigraphy in 12 patients with syndrome X and 10 control subjects. Cardiac MIBG uptake was assessed by the heart/mediastinum (H/M) ratio and by an MIBG uptake defect score (higher values=lower uptake). In syndrome X patients, we also correlated MIBG scintigraphic findings with stress myocardial perfusion as assessed by 201Tl scintigraphy. An inferior MIBG defect was observed in only 1 control subject, whereas 9 patients (P<.01) showed MIBG defects. The heart was totally or almost totally invisible on MIBG images in 5 patients, and predominantly regional defects were observed in 4. The H/M ratio was lower (1.70+/-0.6 versus 2.2+/-0.3, P=.03) and MIBG uptake defect score higher (35+/-31 versus 4+/-2, P=.003) in syndrome X patients. Reversible stress thallium perfusion defects were found in 62% of patients with MIBG defects but in no patient with normal MIBG uptake. MIBG defects persisted unchanged in 7 patients at a 5+/-3-month follow-up study.

CONCLUSIONS

In this study, obvious defects in global and/or regional cardiac MIBG uptake, indicating an abnormal cardiac adrenergic nerve function, were detected in 75% of patients with syndrome X. These findings strongly support the cardiac origin of chest pain in syndrome X, although the mechanisms and the pathophysiological meaning of the abnormal cardiac MIBG uptake in these patients deserve further investigation.

Investigation of the mechanism of chest pain in patients with angiographically normal coronary arteries using transesophageal dobutamine stress echocardiography

OBJECTIVES

The present study sought to determine whether myocardial contractile abnormalities accompany the development of chest pain in patients with normal coronary angiograms.

BACKGROUND

The mechanism of chest pain in patients with angina despite a normal coronary arteriogram is controversial. Although previous studies postulated the existence of coronary microvascular dysfunction, others failed to find evidence of myocardial ischemia, and recent studies have demonstrated abnormal cardiac sensitivity in these patients that can lead to chest pain on a nonischemic basis.

METHODS

Seventy patients (26 men and 44 women, mean age 49 +/- 10 years) with angina-like chest pain and angiographically normal coronary arteries underwent exercise treadmill testing, radionuclide angiography at rest and during exercise, thallium stress testing and transesophageal dobutamine stress echocardiography. The results of exercise treadmill testing and stress echocardiography were compared with those obtained in 26 normal control subjects (19 men and 7 women, mean age 56 +/- 7 years).

RESULTS

Abnormalities consistent with myocardial ischemia were noted in 31% of the patients during exercise treadmill testing, in 16% during exercise radionuclide angiography and in 18% during thallium stress testing. The findings of the radionuclide studies were not concordant with one another and were not related to the presence of repolarization changes during exercise testing. During infusion of dobutamine, chest pain developed in 59 patients (84%) and in none of the control subjects (p < 0.0001); repolarization changes occurred in 22 patients (34%) and in 2 control subjects (8%) (p < 0.04). None of the patients or the control subjects developed regional wall motion abnormalities with dobutamine. The quantitative myocardial contractile response to dobutamine was similar in patients and control subjects, with an 80% power to detect a 25% difference in systolic wall thickening at the maximal dose of dobutamine.

CONCLUSIONS

There was no agreement in the results of noninvasive tests in our patients. Despite the frequent provocation of chest pain and electrocardiographic abnormalities with dobutamine, the patients demonstrated a quantitatively normal myocardial contractile response without development of wall motion abnormalities. These observations strongly suggest that myocardial ischemia is not the cause of chest pain in patients with a normal coronary arteriogram.

Ischemic-like ST-segment changes during Holter monitoring in patients with angina pectoris and normal coronary arteries but negative exercise testing

To evaluate whether Holter electrocardiographic monitoring may improve the detection of ST-segment depression in patients with anginal chest pain and normal coronary arteries, we performed symptom-limited exercise testing and 24-hour Holter monitoring in a group of 38 such patients (27 women, age 54 +/- 8 years). Patients were divided into 2 groups:group X1 included 28 patients with and group X2 10 patients without significant ST-segment depression during exercise testing. There were no significant differences between the 2 groups in age, gender, characteristics of chest pain, exercise duration, heart rate (HR), and blood pressure at peak exercise, but anginal pain during exercise testing was reported by 10 patients of group X1 (36%) and 9 of group X2 (90%) (p <0.01). Episodes of ST-segment depression on Holter monitoring were found in 17 patients of group X1 (61%) and in 5 patients of group X2 (50%) (p = NS). There were no differences between the 2 groups in daily number of ST episodes (3.6 +/- 4 vs 2.8 +/- 5 episodes per patient), symptomatic episodes (8% vs 18%), and duration of the episodes. On average, HR increased significantly, in a similar way, from 15 minutes before ST-segment depression to 1-mm ST in both groups, and its value at the onset of ischemia was similar in the 2 groups (102 +/- 22 vs 109 +/- 18 beats/min, p = NS). Finally, HR at 1-mm ST during Holter monitoring was significantly lower than that observed at 1-mm ST during exercise testing (127 +/- 16 beats/min, p < or = 0.01) in group X1, and it was also lower than that observed at peak exercise (136 +/- 22 beats/min, p < or = 0.01) in group X2. In conclusion, Holter monitoring can significantly increase the detection of ST-segment depression in patients with anginal pain and normal coronary arteries, indicating a cardiac, although not necessarily ischemic, origin of the pain. Indeed, 50% of our patients with negative symptom-limited exercise testing showed spontaneous ST changes, compatible with transient myocardial ischemia, during daily activities. Differences in the response of coronary microvascular tone to exercise testing and to stimuli operating during daily life are likely to play a significant role in determining these findings.

Advantages and disadvantages of dobutamine stress echocardiography compared with treadmill exercise electrocardiography in detecting ischemia

We compared the effectiveness and practicability of dobutamine stress echocardiography (DSE) and treadmill exercise electrocardiographic testing (TMT) for detecting coronary artery disease. Ninety-six patients (mean age 58.8 +/- 9.0 years) who presented for coronary angiography underwent both DSE and symptom-limited TMT. Two-dimensional echocardiography was performed to detect ischemia-induced wall motion abnormalities during incremental dobutamine infusion (5-40 micrograms/kg per min administered in 5 min steps). The sensitivity of detecting ischemia was 63% for TMT and 79% for DSE (p < 0.05); the specificity was 61% for TMT and 88% for DSE (p < 0.05). The accuracy of TMT was 63% and of DSE 82% (p < 0.01). In patients in whom both tests gave true-positive results, the maximum ST depression was evaluated during DSE and TMT (n = 31). The ST segment depressions detected by DSE were significantly smaller than those detected by TMT (0.04 +/- 0.04 mV vs 0.17 +/- 0.07 mV, p < 0.01), and 10 patients had no evidence of ST segment depression despite the presence of new wall motion abnormalities. DSE took significantly longer to perform than TMT (26.0 +/- 5.0 min vs 5.5 +/- 2.0 min, p < 0.01). Thus, DSE is more sensitive, specific and accurate than TMT in detecting coronary artery disease and can detect ischemia at an earlier stage. However, it takes longer to perform than TMT and thus may be less suitable for routine clinical use.

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.

Dipyridamole echocardiography for diagnosis of coexistent coronary artery disease in hypertrophic cardiomyopathy. Echo-Persantine International Cooperative (EPIC) Study Group--Subproject Hypertrophic Cardiomyopathy

The recognition of coexistent coronary artery disease (CAD) in patients with hypertrophic cardiomyopathy may be difficult by noninvasive testing based upon electrocardiographic changes or perfusion defects. Dipyridamole-stress echocardiography has proved a sensitive and highly specific test for noninvasive diagnosis of CAD in various patient subsets. To establish the feasibility, safety, and diagnostic accuracy of dipyridamole-stress echocardiography in patients with hypertrophic cardiomyopathy, we performed high-dose dipyridamole testing (up to 0.84 mg/kg over 10 minutes) in 88 patients with hypertrophic cardiomyopathy (63 men; mean age +/- SD, 46 +/- 17 years). A subset of 60 patients was referred for coronary angiography independently of test results; CAD was defined as > or = 50% diameter narrowing in at least 1 major coronary vessel. Dipyridamole echocardiography/electrocardiography testing was completed in all patients, with no limiting side effects or adverse reactions. In the subgroup of 60 patients with coronary angiography (14 with and 46 without CAD), chest pain occurred in 18 patients (8 with and 10 without CAD, p = NS); ST-segment depression > or = 2 mm from baseline in 28 (7 with and 21 without CAD, p = NS); and transient dyssynergy in 10 patients (10 with and none without CAD, p < 0.0001). Assuming the transient regional dyssynergy to be the only criterion of positivity, the dipyridamole echocardiography test showed 71% sensitivity, 100% specificity, 100% positive predictive value, and 93% diagnostic accuracy for diagnosis of angiographically assessed CAD. We conclude that high-dose dipyridamole echocardiography testing may be considered a feasible and accurate tool for the noninvasive diagnosis of CAD in patients with hypertrophic cardiomyopathy.

Hypertension and ischemic heart disease. Role of dipyridamole echocardiography test

The aim of this study is to try to evaluate the relationship between arterial hypertension and ischemic heart disease (IHD) in the light of the physiopathologic response pattern to the dipyridamole echocardiography test (DET) in hypertensive patients, in pharmacologic washout, without any electrocardiographic ST segment depression during exercise tests or at rest. Sixty patients affected by mild to moderate asymptomatic essential arterial hypertension were studied: the subjects had a sitting diastolic blood pressure > or = 95 < or = 114 mmHg; there were 38 men and 22 women with a mean age of 49.8 +/- 7.6 years (range twenty-nine to sixty-eight). All patients had undergone high-dose DET (0.84 mg/kg in ten minutes). No patients developed side effects or asynergy in cardiac contractility during the test. In the absence of any significant coronary artery obstruction assessed angiographically, 18 patients (30%) showed ST segment depression > 1.0 mV during DET, sometimes with the presence of ventricular and/or supraventricular extrasystoles. In this group of patients the left ventricular mass index (LVMI) and duration of hypertension (in months) were higher as compared with those of the other 42 patients (respectively: 160.2 +/- 5.1 vs 129.2 +/- 9.2 g/m2, P < 0.02; and 30 +/- 4.8 vs 9 +/- 5.4 months, P < 0.007). In conclusion it is reasonable to speculate from these data that the ischemic-like" dipyridamole-induced ST segment depression, like that shown by patients affected by Syndrome X, might involve a worse prognosis in hypertensive patients. This may be because of increased coronary resistance due to structural modification or anatomic background.

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.

Left ventricular dysfunction during exercise in patients with angina pectoris and angiographically normal coronary arteries (syndrome X)

Left ventricular function during exercise and recovery was investigated in patients with angina pectoris, ST segment depression during exercise and angiographically normal coronary arteries (syndrome X) using a continuous left ventricular function monitor with cadmium telluride detector (CdTe-VEST). Fourteen patients with syndrome X and 14 patients with atypical chest pain without ST segment depression during exercise and normal coronary arteries (control group) performed supine ergometric exercise after administration of 740-925 MBq of technetium-99m labelled red blood cells, and left ventricular function was monitored every 20 s using CdTe-VEST. Left ventricular ejection fraction (EF) response was impaired (< or = 5% increase from rest to peak exercise) in 11 or 14 patients with syndrome X but in none of the control patients. Resting EF was similar in the two groups (62.1% +/- 6.7% in patients with syndrome X, 61.9% +/- 6.2% in controls); however, EF increase from rest to peak exercise was lower in syndrome X (-3.1 +/- 9.5% vs 14.7% +/- 7.4%, P < 0.001). After cessation of exercise, all patients showed rapid EF increase over baseline and this EF overshoot was lower (19.3% +/- 8.3% vs 26.4% +/- 7.3%, P < 0.001) with the time to EF overshoot longer (114 +/- 43 s vs 74 +/- 43 s, P < 0.05) in patients with syndrome X. Thus, in patients with syndrome X, left ventricular dysfunction was frequently observed during exercise in spite of normal epicardial coronary arteries.

Left ventricular functional reserve in patients with syndrome X: evaluation by continuous ventricular function monitoring

OBJECTIVES

The objective of this study was to evaluate cardiac functional reserve in patients with syndrome X.

BACKGROUND

Syndrome X is characterized by stress-induced anginal pain and ST segment depression, normal findings on coronary angiography and normal left ventricular function at rest. Reduced coronary vasodilative reserve and abnormal myocardial lactate metabolism have been described in such patients.

METHODS

To assess left ventricular functional reserve in patients with syndrome X, continuous radionuclide monitoring of left ventricular end-diastolic volume, end-systolic volume and ejection fraction was performed in 12 patients and 13 normal control subjects during supine bicycle ergometer exercise.

RESULTS

In control subjects, end-diastolic volume increased at peak exercise from 100% to 106.5% (p < 0.01), end-systolic volume decreased from 39.1% to 22.6% (p < 0.01) and ejection fraction increased from 60.9% to 78.6% (p < 0.01). In patients with syndrome X, end-diastolic volume increased at peak exercise from 100% to 106% (p < 0.01), and end-systolic volume decreased at ST segment depression < or = 0.5 mm (the ST point) from 37% to 28.8% (p < 0.01) but increased at peak exercise to 44.7% (p < 0.01 vs. the ST point). Thus, ejection fraction increased at the ST point from 63% to 72.7% (p < 0.01) but decreased at peak exercise to 57.7% (p < 0.01 vs. the ST point and control subjects) in proportion to the degree of ST segment depression. In nine patients (75%), ejection fraction at peak exercise was lower than baseline values. All patients and control subjects showed a rapid ejection fraction increase just after exercise during the recovery period. The degree of ejection fraction "overshoot" in patients was similar to that in control subjects, but the interval from the end of exercise to the overshoot in patients was significantly longer than that in control subjects (118 vs. 65 s, p < 0.01).

CONCLUSIONS

In patients with syndrome X subjected to exercise stress, left ventricular function remained normal before the onset of ST segment depression. Once ST segment depression appeared, left ventricular function deteriorated in proportion to the degree of depression, and reduced left ventricular function persisted into the recovery period. Continuous ventricular function monitoring is thus a useful predictor of reduced left ventricular functional reserve in patients with syndrome X.

Cardiopulmonary exercise testing in syndrome X

Patients with syndrome X have been found to have an abnormal coronary blood flow reserve. The physical performance during exercise, however, has been incompletely investigated. Cardiopulmonary exercise testing (CPX) is a reliable noninvasive method to provide indexes of lung, heart, circulation, and muscle functions. In 15 patients (10 women) with syndrome X and in age and sex-matched normal individuals, CPX was performed twice a day (8 AM and 4 PM) on two separate occasions 2 months apart. Time and oxygen consumption at peak exercise, at ventilatory anaerobic and electrocardiographic thresholds, as well as norepinephrine plasma concentrations at each work load and at peak exercise in both tests were obtained. In syndrome X in both evaluations, the 4 PM performance was characterized by an earlier onset of both ventilatory anaerobic and electrocardiographic thresholds despite lower values of VO2 and double-product, and by a greater peak ST segment depression despite similar total exercise time, VO2, and double-product. No difference between tests was found in the norepinephrine response to exercise. Normal subjects showed reproducible CPX and hormonal responses in the two tests. Thus these data may suggest a circadian variation of coronary vascular response to exercise in patients with syndrome X, leading to a lower ischemic threshold early in the afternoon. The parallel earlier onset of the ventilatory anaerobic threshold may reflect a concomitant abnormal muscular blood flow response (that is, vasoconstriction of working muscle arteries), suggesting a link between coronary and peripheral circulations.

Lower threshold for adenosine-induced chest pain in patients with angina and normal coronary angiograms

OBJECTIVE

To investigate whether patients with angina-like chest pain and normal coronary angiograms are more sensitive to adenosine as an inducer of chest pain.

DESIGN

Increasing doses of adenosine were given in a single blind study as intravenous bolus injections. Chest pain and the electrocardiographic findings were noted.

PATIENTS

Eight patients with angina-like chest pain but no coronary stenoses (group A), nine patients with angina and coronary stenoses (group B), and 16 healthy volunteers (group C).

RESULTS

In the absence of ischaemic signs on the electrocardiogram adenosine provoked angina-like pain in all patients in groups A and B. The pain was located in the chest, and its quality and location were described as being no different from the patient's habitual angina. In group C, 14 of 16 subjects reported chest pain. The lowest dose resulting in chest pain was lower in group A (0.9 (0.6) mg) than in group B (3.1 (1.5)mg) (p < 0.005) and in group C (6.2 (3.7) mg) (p < 0.005). The maximum tolerable dose was lower in group A (4.7 (2.1) mg) than in group B (9.2 (3.8) mg) (p < 0.05) and in group C (12.0 (4.1) mg) (p < 0.005).

CONCLUSIONS

Patients with angina-like chest pain and normal coronary angiograms have a low pain threshold and low tolerance to pain induced by adenosine.

ST-segment depression during dipyridamole infusion, and its clinical, scintigraphic and hemodynamic correlates

The goal of this study was to determine whether dipyridamole-induced ST-segment depression reflects more severe or extensive myocardial hypoperfusion than the absence of this electrocardiographic finding. The clinical, hemodynamic and scintigraphic correlates of ST-segment depression during intravenous dipyridamole infusion were studied in 204 consecutive patients undergoing dipyridamole stress thallium-201 (Tl-201) imaging for evaluation of coronary artery disease. Of 182 patients with a diagnostic baseline electrocardiogram, 28 (15%) developed ST depression after dipyridamole. Patients with ST depression, compared with those without, were older (64 +/- 1 vs 60 +/- 1 years; p less than 0.03) and had a higher frequency of chest pain (57 vs 23%; p less than 0.001) and a higher heart rate-blood pressure product (12.7 +/- 0.6 vs 11.2 +/- 0.2 x 10(3); p less than 0.008) after dipyridamole. Patients with ST depression were more likely to have Tl-201 redistribution (64 vs 38%; p less than 0.02) and a greater number of redistribution defects (2.3 +/- 0.04 vs 0.9 +/- 0.1, p less than 0.001) than were those without ST depression. By multivariate logistic regression analysis, the most powerful correlate of ST depression was the number of segments having Tl-201 redistribution (p less than 0.001). Other independent correlates were presence of chest pain, heart rate at Tl-201 injection, and age. Thus, the determinants of dipyridamole-induced ST-segment depression include the scintigraphic extent of reversible hypoperfusion, as well as indexes of myocardial oxygen demand.

Coronary microvascular disease in hypertensives

Arterial hypertension can badly affect coronary circulation through several mechanisms that are not mutually exclusive, namely, coronary artery disease, left ventricular hypertrophy, and microvascular disease. Theoretical and experimental data suggest that coronary microvascular disease may exist in hypertensives, in whom it can cause both a reduction of coronary flow reserve and a shift to the right of the coronary flow autoregulation curve. To address this issue, we used dipyridamole- echocardiography test, which causes ischemic-like ST segment depression with no detectable changes in left ventricular function in different subsets of patients with microvascular disease (Syndrome X; Hypertrophic cardiomyopathy; acute heart rejection). We found that dipyridamole infusion can cause a similar pattern of response (i.e., echocardiographically silent ST segment depression) in mild-moderate essential hypertensives with normal epicardial coronary arteries, without left ventricular hypertrophy, with increased forearm minimal vascular resistances and with a reduced coronary reserve. This pattern of response identifies hypertensives with higher risk of ventricular arrhythmias, is amplified by acute reduction of diastolic blood pressure and can be reversed, together with the reduction of forearm vascular resistances by chronic antihypertensive treatment. Taken together these findings suggest that microvascular coronary disease can exist in hypertensives with two adverse consequences, consistent with the experimental background: the reduction of coronary flow reserve as well as a shift to the right of the coronary flow autoregulation curve.

A combination of electrocardiographic methods represents a further step toward the noninvasive identification of patients with syndrome X

Identification of patients with angina but normal coronary arteriograms (syndrome X) using noninvasive means would be desirable. The ability of four established exercise electrocardiographic methods to identify angina patients with and without coronary artery disease was compared with that of a method based on a combination of the above (combined method). A treadmill score, a multivariate method, the ST segment recovery loop, the ST/heart rate adjustment, and the combined method were applied to 112 patients who had typical exertional angina and positive exercise tests (greater than 1 mm ST segment depression); 90 had documented coronary artery disease and 22 had syndrome X. The combined method and the treadmill score had a significantly higher diagnostic accuracy (both 81%, as 91 of the 112 patients were correctly identified by both methods) than the multivariate (66%) and ST segment recovery loop (64%) methods (p less than 0.05). The ST/heart rate adjustment had a lower sensitivity for syndrome X than any other method (1 of 22). Thus methods that involve the assessment of both ST and non ST segment variables have greater accuracy in separating syndrome X and coronary artery disease patients than methods relying more heavily on ST segment changes.

Absence of myocardial dysfunction during stress in patients with syndrome X

Stress two-dimensional echocardiographic studies were performed in 18 patients with angina, a positive exercise test and normal findings on coronary angiography (syndrome X). Rest and immediate posttreadmill exercise two-dimensional echocardiograms were performed with a digitized cine loop and side by side visual analysis in all patients. In 16 of these patients, right atrial pacing up to 160 beats/min was also performed and percent systolic wall thickening was calculated at five equally spaced segments around the left ventricle, each corresponding to an anterior, lateral and inferior wall and the posterior and the anterior ventricular septum. Measurements of percent systolic wall thickening were established in 10 age- and gender-matched normal persons for comparison. ST segment depression occurred in all patients during exercise and persisted for 42.1 s (range 18 to 75) into the recovery period. Immediate postexercise echocardiography was started within 20.1 +/- 5.4 s and completed in 54.1 +/- 11.3 s. No patient had regional wall motion abnormalities seen on two-dimensional imaging of any myocardial segment. Thirteen patients (72%) reported reproduction of their usual chest pain, which led to termination of the test. During rapid right atrial pacing, nine patients (56%) developed ST segment depression that was associated with angina in seven. In all 16 patients, percent systolic wall thickening increased over values at rest in each myocardial segment. Percent systolic wall thickening averaged 47.1 +/- 6.1% at rest and increased to 74 +/- 8% during right atrial pacing (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Impaired left ventricular filling during ST-segment depression provoked by dipyridamole infusion in patients with syndrome X

The left ventricular filling and regional wall motion patterns were compared in 6 normal subjects, 20 patients with coronary artery disease, and 10 patients with syndrome X by means of Doppler and two-dimensional echocardiography during high-dose (0.9 mg/kg body weight in 10 min) dipyridamole infusion. During the procedure none of the normal subjects had chest pain or significant ST depression (greater than 0.1 mV) whereas 10 of 20 patients with coronary artery disease had ST depression, 3 with chest pain. Six patients with syndrome X had ST depression, 5 with chest pain. Regional wall motion abnormalities were identified in 6 patients with coronary artery disease who had ST depression but none were detected in normals or in patients with syndrome X. Compared with normals (-2.1 +/- 3.5%) there was a significant difference in percentage decrease in the peak early filling velocity in patients with coronary artery disease and ST depression (-10.3 +/- 6.2%; p less than 0.01) and in patients with syndrome X and ST depression (-9.4 +/- 6.9%; p less than 0.05). These findings indicate that, in the presence of dipyridamole-induced ST depression, patients with syndrome X have an abnormal left ventricular filling pattern similar to that observed in patients with coronary artery disease. This suggests that myocardial ischemia occurs in patients with syndrome X but the absence of regional wall motion abnormality suggests that it is diffuse.

Microvascular angina. Cardiovascular investigations regarding pathophysiology and management

A significant minority of patients with chest pain who undergo cardiac catheterization are found to have angiographically normal coronary arteries. Over the past 25 years, several studies have shown that a subset have demonstrable abnormalities in coronary flow and cardiac function; however, only a minority of these patients have convincing evidence for myocardial ischemia during stress, and alternative mechanisms have been explored to explain the frequent and debilitating symptoms of pain experienced by the majority of these patients undergoing study. Abnormal visceral nociception appears to be a fundamental abnormality in this population, whether or not demonstrable abnormalities in coronary flow or cardiac function can be demonstrated.

Increased myocardial perfusion at rest and diminished perfusion reserve in patients with angina and angiographically normal coronary arteries

Angiographically normal coronary arteries are found in a substantial number of patients evaluated for angina pectoris. One third to one half of such patients demonstrate abnormalities of myocardial perfusion or metabolism when evaluated with invasive techniques. This study was designed to determine whether angina in such patients is attributable to abnormalities of perfusion at rest, maximal perfusion or vasodilator reserve and whether any identified abnormalities were global or regional in nature. Positron emission tomography was performed with oxygen-15-labeled water (H2(15)O) and oxygen-15-labeled carbon monoxide (C15O) before and after intravenous dipyridamole to assess regional myocardial perfusion and perfusion reserve in absolute terms in 16 normal subjects and 17 patients with chest pain and angiographically normal coronary arteries. Eight of the 17 patients had a myocardial perfusion reserve less than 2.5 (the lower limit of normal in studies with positron emission tomography, as well as with other techniques) and 9 of 17 patients had a normal response. In the patients with an impaired perfusion reserve, perfusion at rest was significantly higher than that measured in normal subjects (1.61 +/- 0.38 versus 1.25 +/- 0.28 ml/g per min, p less than 0.02) and maximal flow and perfusion reserve were significantly reduced (2.26 +/- 0.92 versus 4.62 +/- 1.58 ml/g per min and 1.4 +/- 0.5 versus 3.8 +/- 1.1, respectively; p less than 0.001 for both comparisons). Abnormalities of perfusion and perfusion reserve were spatially homogeneous without detectable regional disparities. Thus, nearly half of patients with chest pain and normal coronary arteries have abnormalities of myocardial perfusion that are detectable noninvasively with positron emission tomography and H2(15)O.

ST segment depression elicited by dipyridamole infusion in asymptomatic hypertensive patients

In asymptomatic patients with essential hypertension, electrocardiographic changes suggestive of myocardial ischemia can be elicited by rapid pressure lowering or by pronounced coronary arteriolar dilation. The aim of this study was to assess whether dipyridamole infusion might induce ischemic-like electrocardiographic changes in asymptomatic essential hypertensive patients and to describe the clinical and echocardiographic correlates possibly associated with this response. We therefore studied a control group of 20 normotensive individuals and a group of 28 asymptomatic patients with mild-to-moderate essential hypertension. All underwent dipyridamole-echocardiography testing (12-lead electrocardiogram and two-dimensional echocardiographic monitoring with dipyridamole infusion, 0.84 mg/kg over 10'). No patient showed transient regional dyssynergy during dipyridamole infusion. None of the normotensive and 10 of 28 of the hypertensive participants had horizontal or downsloping ST segment depression more than 0.1 mV during dipyridamole (0% versus 36%, p less than 0.01). Hypertensive patients with ("responders") (n = 10) and without ("nonresponders") (n = 18) ST segment depression showed similar values of percent fractional shortening in baseline conditions (32 +/- 5 versus 33 +/- 6, p = NS) and at peak dipyridamole infusion (45 +/- 8 versus 43 +/- 5, p = NS). The peak early to peak late velocity ratio values (evaluated from transmitral flow tracings by Doppler technique) were also similar in baseline conditions (0.86 +/- 0.14 versus 0.94 +/- 0.30, p = NS) and at peak dipyridamole (0.72 +/- 0.15 versus 0.78 +/- 0.32, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Electrocardiographic changes suggestive of myocardial ischemia elicited by dipyridamole infusion in acute rejection early after heart transplantation

Acute cardiac rejection, syndrome X, and arterial hypertension can induce small vessel damage and, therefore, restriction of coronary reserve in the presence of normal epicardial coronary arteries. A characteristic response pattern to dipyridamole (DIP) infusion has been previously described in syndrome X and arterial hypertension: ST segment depression without any measurable systolic dysfunction. The aim of this study was to establish whether acute cardiac rejection might induce electrocardiographic alterations during DIP infusion. Changes in the 12-lead electrocardiogram and two-dimensional echocardiogram during high-dose DIP infusion (up to 0.84 mg/kg in 10 minutes) were evaluated within 24 hours of endomyocardial biopsy in 14 transplanted patients. A total of 47 biopsy-controlled DIP studies were performed within 5 weeks after cardiac transplantation. For each patient, at least 7 days elapsed between two consecutive studies. Electrocardiographic and echocardiographic tracings were analyzed without prior knowledge of endomyocardial biopsy findings. No remarkable side effects occurred in any case, so that the DIP study could be completed in all patients. A diagnostic (greater than 0.1 mV) ST segment depression was found in 11 studies. The sensitivity and specificity of DIP-induced ST segment depression for the detection of biopsy-proven acute rejection were 72% and 94%, respectively. These data show that DIP stress is feasible and safe in transplanted patients and that acute cardiac rejection can be accompanied by DIP-induced ST segment depression without detectable impairment in systolic function. These changes might provide noninvasive markers for surveillance of rejection.