Coronary reserve and exercise ECG in patients with chest pain and normal coronary angiograms

[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.

Automated Pixel-Wise Quantitative Myocardial Perfusion Mapping by CMR to Detect Obstructive Coronary Artery Disease and Coronary Microvascular Dysfunction: Validation Against Invasive Coronary Physiology

OBJECTIVES

This study sought to assess the performance of cardiovascular magnetic resonance (CMR) myocardial perfusion mapping against invasive coronary physiology reference standards for detecting coronary artery disease (CAD, defined by fractional flow reserve [FFR] ≤0.80), microvascular dysfunction (MVD) (defined by index of microcirculatory resistance [IMR] ≥25) and the ability to differentiate between the two.

BACKGROUND

Differentiation of epicardial (CAD) and MVD in patients with stable angina remains challenging. Automated in-line CMR perfusion mapping enables quantification of myocardial blood flow (MBF) to be performed rapidly within a clinical workflow.

METHODS

Fifty patients with stable angina and 15 healthy volunteers underwent adenosine stress CMR at 1.5T with quantification of MBF and myocardial perfusion reserve (MPR). FFR and IMR were measured in 101 coronary arteries during subsequent angiography.

RESULTS

Twenty-seven patients had obstructive CAD and 23 had nonobstructed arteries (7 normal IMR, 16 abnormal IMR). FFR positive (epicardial stenosis) areas had significantly lower stress MBF (1.47 ± 0.48 ml/g/min) and MPR (1.75 ± 0.60) than FFR-negative IMR-positive (MVD) areas (stress MBF: 2.10 ± 0.35 ml/g/min; MPR: 2.41 ± 0.79) and normal areas (stress MBF: 2.47 ± 0.50 ml/g/min; MPR: 2.94 ± 0.81). Stress MBF ≤1.94 ml/g/min accurately detected obstructive CAD on a regional basis (area under the curve: 0.90; p < 0.001). In patients without regional perfusion defects, global stress MBF <1.82 ml/g/min accurately discriminated between obstructive 3-vessel disease and MVD (area under the curve: 0.94; p < 0.001).

CONCLUSIONS

This novel automated pixel-wise perfusion mapping technique can be used to detect physiologically significant CAD defined by FFR, MVD defined by IMR, and to differentiate MVD from multivessel coronary disease. A CMR-based diagnostic algorithm using perfusion mapping for detection of epicardial disease and MVD warrants further clinical validation.

Epicardial and microvascular coronary vasomotor dysfunction and its relation to myocardial ischemic burden in patients with non-obstructive coronary artery disease

AIM

To assess the relative contribution of epicardial endothelium-dependent (EDD) and microvascular endothelium-independent (EIMVD) coronary vasomotor dysfunction to the extent of myocardial ischemia in patients with normal angiograms or non-obstructive coronary artery disease (NOCAD).

METHODS

Coronary vasomotion was evaluated by quantitative angiography and blood flow (CBF) measurements during intracoronary acetylcholine, nitroglycerine, and adenosine in 101 patients. Myocardial SPECT ischemic burden was evaluated by semi-quantitative scoring of summed stress (SSS) and summed ischemic (SDS) perfusion defect size.

RESULTS

Coronary vasomotor dysfunction was found in most patients (83; 77%) with a divergent behavior of EDD and EIMVD in one half of them (52.4%). There was no significant difference in SDS between patients with and without EIMVD, whereas SDS was significantly greater in subjects with EDD as compared to patients with normal response to acetylcholine (4.31 ± 2.44 vs 1.35 ± 1.45; P < .0001). Patients with EDD, either alone or in combination with EIMVD, had significantly higher SSS as compared to patients with lone EIMVD or normal vasomotor function (8.50 ± 5.32; 5.55 ± 3.21; 2.60 ± 2.14; and 1.74 ± 1.66, respectively; P < .0001). Acetylcholine CBF correlated inversely with both SDS (r = -0.545; P < .001) and SSS (r = 0.538; P < .001).

CONCLUSIONS

In NOCAD patients with symptoms and signs of myocardial ischemia, vasomotor dysfunction is common. EDD is associated with greater extent of ischemia as compared to isolated EIMVD. Thus, assessment of both EIMVD and EDD is needed to recognize mechanisms of ischemia and identify patients with greater ischemic burden.

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.

Cardiac Syndrome X: Update

Cardiac Syndrome X (CSX), characterized by angina-like chest discomfort, ST segment depression during exercise, and normal epicardial coronary arteries at angiography, is highly prevalent in women. CSX is not benign, and linked to adverse cardiovascular outcomes and a poor quality of life. Coronary microvascular and endothelial dysfunction and abnormal cardiac nociception have been implicated in the pathogenesis of CSX. Treatment includes life-style modification, anti-anginal, anti-atherosclerotic, and anti-ischemic medications. Non-pharmacological options include cognitive behavioral therapy, enhanced external counterpulsation, neurostimulation, and stellate ganglionectomy. Studies have shown the efficacy of individual treatments but guidelines outlining the best course of therapy are lacking.

Cardiac Syndrome X: update 2014

Cardiac Syndrome X (CSX), characterized by angina-like chest discomfort, ST segment depression during exercise, and normal epicardial coronary arteries at angiography, is highly prevalent in women. CSX is not benign, and linked to adverse cardiovascular outcomes and a poor quality of life. Coronary microvascular and endothelial dysfunction and abnormal cardiac nociception have been implicated in the pathogenesis of CSX. Treatment includes life-style modification, anti-anginal, anti-atherosclerotic, and anti-ischemic medications. Non-pharmacological options include cognitive behavioral therapy, enhanced external counterpulsation, neurostimulation, and stellate ganglionectomy. Studies have shown the efficacy of individual treatments but guidelines outlining the best course of therapy are lacking.

Sex-specific factors in microvascular angina

In women presenting for evaluation of suspected ischemic symptoms, a diagnosis of normal coronary arteries is 5 times more common than it is in men. These women are often labelled as having cardiac syndrome X, and a subset of them have microvascular angina caused by microvascular coronary dysfunction (MCD). MCD is not benign and is associated with an annual 2.5% cardiac event rate. Noninvasive testing for MCD remains insensitive, although newer imaging modalities, such as adenosine cardiac magnetic resonance imaging, appear promising. The gold standard for diagnosis of MCD is coronary reactivity testing, an invasive technique that is not available in many countries. With regard to treatment, large-scale trials are lacking. Although research is ongoing, the current platform of therapy consists of antiangina, antiplatelet, and endothelium-modifying agents (primarily angiotensin-converting enzyme inhibitors and statins).

Attenuated systemic microvascular function in men with coronary artery disease is associated with angina but not explained by atherosclerosis

INTRODUCTION

Refractory angina is the occurrence of clinical symptoms despite maximal therapy. We investigated associations between microvascular function, atherosclerotic burden, and clinical symptoms in subjects with CAD.

METHODS

Skin microvascular response to heating and ischemia was assessed in 167 male volunteers by laser Doppler fluximetry; 82 with CAD on maximal therapy and 85 with no known CAD (noCAD). CAC scores, carotid IMT, and femoral IMT were measured and symptoms were scored using the Rose angina questionnaire.

RESULTS

Patients with CAD had poorer microvascular response to heating (114[95% CI 106-122]au CAD vs. 143[134-153]au no CAD; p < 0.0001) and ischemia (42[38-46]au CAD vs. 53[78-58]au. noCAD; p = 0.001). Thirty-eight percent of the noCAD group had elevated CAC scores. There were no associations between markers of atherosclerosis and microvascular function. Forty-two percent of the CAD group had refractory angina. This was associated with impaired microvascular function compared to those with elevated CAC scores but no symptoms (109 [95-124]au vs. 131[122-140]au; p = 0.008).

CONCLUSIONS

Men with symptomatic CAD have poorer microvascular function compared to individuals without CAD. Microvascular function does not correlate with atherosclerosis, but is impaired in individuals with refractory angina. Microvascular dysfunction may play a role in the symptomatology of angina.

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.

Inflammation and microvascular dysfunction in cardiac syndrome X patients without conventional risk factors for coronary artery disease

OBJECTIVES

The aim of this study was to ascertain whether coronary microvascular dysfunction (CMD) and inflammation are related in cardiac syndrome X (CSX).

BACKGROUND

CMD can lead to CSX, defined as typical angina and transient myocardial ischemia despite normal coronary arteriograms. Inflammation has been suggested to play a role in the pathogenesis of myocardial ischemia in CSX.

METHODS

We assessed 21 CSX patients (age 52 ± 10 years; 17 women) without traditional cardiovascular risk factors and 21 matched apparently healthy control subjects. Positron emission tomography was used to measure myocardial blood flow (MBF) and coronary flow reserve (CFR) in response to intravenous adenosine, whereas high-sensitivity C-reactive protein (CRP) was measured to assess inflammation. Patients were subdivided a priori into 2 groups according to CRP concentrations at study entry (i.e., ≤3 or >3 mg/l).

RESULTS

There were no differences in resting (1.20 ± 0.23 ml/min/g vs. 1.14 ± 0.20 ml/min/g; p = 0.32) or hyperemic MBF (3.28 ± 1.02 ml/min/g vs. 3.68 ± 0.89 ml/min/g; p = 0.18) between CSX patients and the control group, whereas CFR was mildly reduced in CSX patients compared with the control group (2.77 ± 0.80 vs. 3.38 ± 0.80; p = 0.02). Patients with CRP >3 mg/l had more severe impairment of CFR (2.14 ± 0.33 vs. 3.16 ± 0.76; p = 0.001) and more ischemic electrocardiographic changes during adenosine administration than patients with lower CRP, and a negative correlation between CRP levels and CFR (r = -0.49, p = 0.02) was found in CSX patients.

CONCLUSIONS

CSX patients with elevated CRP levels had a significantly reduced CFR compared with the control group, which is indicative of CMD. Our study thus suggests a role for inflammation in the modulation of coronary microvascular responses in patients with CSX.

Quantitative cardiac positron emission tomography: the time is coming!

In the last 20 years, the use of positron emission tomography (PET) has grown dramatically because of its oncological applications, and PET facilities are now easily accessible. At the same time, various groups have explored the specific advantages of PET in heart disease and demonstrated the major diagnostic and prognostic role of quantitation in cardiac PET. Nowadays, different approaches for the measurement of myocardial blood flow (MBF) have been developed and implemented in user-friendly programs. There is large evidence that MBF at rest and under stress together with the calculation of coronary flow reserve are able to improve the detection and prognostication of coronary artery disease. Moreover, quantitative PET makes possible to assess the presence of microvascular dysfunction, which is involved in various cardiac diseases, including the early stages of coronary atherosclerosis, hypertrophic and dilated cardiomyopathy, and hypertensive heart disease. Therefore, it is probably time to consider the routine use of quantitative cardiac PET and to work for defining its place in the clinical scenario of modern cardiology.

Women, cardiac syndrome X, and microvascular heart disease

New data suggest that persistent chest pain, despite normal coronary angiography, is less benign than previously thought. It has long been recognized that cardiac syndrome X (CSX) is associated with significant suffering, disability, and health care costs, but the biggest shift in thinking comes in terms of long-term risk. It is now recognized that the prognosis is not benign and that a significant proportion of patients are at increased cardiovascular disease risk. Of major debate is the question of whether the mechanisms that explain this chest pain are cardiac vs noncardiac. The most current definition of CSX is the triad of angina, ischemia, and normal coronary arteries, which is associated with an increased cardiovascular risk. This paper provides a review of CSX, epidemiology of the problem, proposed explanatory mechanisms, and important next steps in research. Central to this review is the proposition that new insights into CSX will be fostered by both clinical and scientific collaboration between cardiovascular and pain scientists.

Microvascular coronary dysfunction in women: pathophysiology, diagnosis, and management

Women exhibit a greater symptom burden, more functional disability, and a higher prevalence of no obstructive coronary artery disease compared to men when evaluated for signs and symptoms of myocardial ischemia. Microvascular coronary dysfunction (MCD), defined as limited coronary flow reserve and/or coronary endothelial dysfunction, is the predominant etiologic mechanism of ischemia in women with the triad of persistent chest pain, no obstructive coronary artery disease, and ischemia evidenced by stress testing. Evidence shows that approximately 50% of these patients have physiological evidence of MCD. MCD is associated with a 2.5% annual major adverse event rate that includes death, nonfatal myocardial infarction, nonfatal stroke, and congestive heart failure. Although tests such as adenosine stress cardiac magnetic resonance imaging may be a useful noninvasive method to predict subendocardial ischemia, the gold standard test to diagnose MCD is an invasive coronary reactivity testing. Early identification of MCD by coronary reactivity testing may be beneficial in prognostication and stratifying these patients for optimal medical therapy. Currently, understanding of MCD pathophysiology can be used to guide diagnosis and therapy. Continued research in MCD is needed to further advance our understanding.

Impact of previous myocardial infarction on the incremental value of myocardial contrast to two-dimensional supine bicycle stress echocardiography in evaluation of coronary artery disease

BACKGROUND

If compared to two-dimensional echocardiography (2DE), myocardial contrast echocardiography (MCE) improves detection of coronary artery disease (CAD) during pharmacological stress, but data on MCE vs. 2DE during supine bicycle stress is limited. Although previous myocardial infarction (MI) influences sensitivity of 2DE, its effect on MCE has not been evaluated.

OBJECTIVES

The study sought to determine the incremental benefit of MCE over 2DE for evaluation of CAD during supine bicycle stress and to assess the impact of previous MI on diagnostic values of both methods.

METHODS

We studied 103 consecutive patients scheduled for coronary angiography. Prior to coronary angiography, all patients underwent supine bicycle stress. 2DE and MCE were performed during this stress test. The diagnosis of obstructive CAD (> or =50% stenosis) was based on the presence of inducible wall motion and perfusion abnormalities.

RESULTS

Quantitative coronary angiography revealed > or =50% stenosis in 53 of 77 patients without previous MI and in 21 of 26 patients with previous MI. If compared to 2DE, MCE was more sensitive (68% vs. 86%; p<0.001) and more accurate (73% vs. 86%; p < 0.001) to detect > or =50% stenosis. In patients without previous MI, 2DE and MCE yielded sensitivity of 65% and 85% (p < 0.01) and accuracy of 71% and 85% (p < 0.01), whereas in patients with previous MI sensitivity was 79% and 90% (p=NS) and accuracy 79% and 88% (p = NS), respectively.

CONCLUSIONS

MCE enhances sensitivity and accuracy of 2DE in detection of obstructive CAD during supine bicycle stress. The incremental benefit of MCE is especially present in patients without previous MI.

Lack of correlation between noninvasive stress tests and invasive coronary vasomotor dysfunction in patients with nonobstructive coronary artery disease

BACKGROUND

Despite a nonobstructive coronary angiogram, many patients may still have an abnormal coronary vasomotor response to provocation and to myocardial demand during stress. The ability of noninvasive stress tests to predict coronary vasomotor dysfunction in patients with nonobstructive coronary artery disease is unknown.

METHODS AND RESULTS

All patients with nonobstructive coronary artery disease who had invasive coronary vasomotor assessment and a noninvasive stress test (exercise ECG, stress echocardiography, or stress nuclear imaging) within 6 months of the cardiac catheterization with provocation at our institution were identified (n=376). Coronary vasomotor dysfunction was defined as a percentage increase in coronary blood flow of <or=50% to intracoronary acetylcholine (endothelium-dependent dysfunction) and/or a coronary flow reserve ratio of <or=2.5 to intracoronary adenosine (endothelium-independent dysfunction). We determined the sensitivity and specificity of various noninvasive stress tests to predict coronary vasomotor dysfunction in these patients. On invasive testing, 233 patients (63%) had coronary vasomotor dysfunction, of which 187 patients (51%) had endothelium-dependent dysfunction, 109 patients (29%) had endothelium-independent dysfunction, and 63 patients (17%) had both. On noninvasive stress testing, 157 (42%) had a positive imaging study and 56 (15%) a positive ECG stress test. The noninvasive stress tests had limited diagnostic accuracy for predicting coronary vasomotor dysfunction (41% sensitivity [95% CI, 34 to 47] and 57% specificity [95% CI, 49 to 66]), endothelium-dependent dysfunction (41% sensitivity [95% CI, 34 to 49] and 58% specificity [95% CI, 50 to 65]), or endothelium-independent dysfunction (46% sensitivity [95% CI, 37 to 56] and 61% specificity [95% CI, 54 to 67]). The exercise ECG test was more specific but less sensitive than the imaging tests.

CONCLUSIONS

This study suggests that a negative noninvasive stress test does not rule out coronary vasomotor dysfunction in symptomatic patients with nonobstructive coronary artery disease. This underscores the need for invasive assessment or novel more sensitive noninvasive imaging for these patients.

Advances in coronary microvascular dysfunction

Considerable focus has been directed towards coronary arterial disease in the management of coronary heart disease, however the coronary microcirculation plays a major role in the regulation of coronary blood flow. Thus while we have multiple medical and revascularisation therapies to treat large vessel coronary artery disease, therapies directed towards the microcirculation are very limited. This review paper summarises important aspects of coronary microvascular dysfunction including (a) methods of assessment, (b) clinical classification of associated disorders, (c) possible pathophysiological mechanisms, and (d) potential therapies. Hence this will provide important background to advancing our understanding and management of coronary heart disease by targeting the coronary microcirculation.

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.

Relation between stress-induced myocardial perfusion defects on cardiovascular magnetic resonance and coronary microvascular dysfunction in patients with cardiac syndrome X

OBJECTIVES

The purpose of this study was to investigate whether a direct relation can be demonstrated between myocardial perfusion defects detected during dobutamine stress test (DST) by cardiovascular magnetic resonance (CMR) and impairment of coronary microvascular dilatory function in patients with cardiac syndrome X (CSX).

BACKGROUND

Despite the fact that coronary microvascular dysfunction has been shown in most patients with CSX, the ischemic origin of CSX remains debated. No previous study assessed whether a strict relation exists between abnormalities in myocardial perfusion and coronary microvascular dysfunction in CSX patients.

METHODS

Eighteen CSX patients (mean age 58 +/- 7 years, 7 men) and 10 healthy control subjects (mean age 54 +/- 8 years, 4 men) underwent myocardial perfusion study by gadolinium-enhanced CMR at rest and at peak DST (maximal dose 40 microg/kg/min). Coronary flow response (CFR) to adenosine (140 microg/kg/min in 90 s) in the left anterior descending (LAD) coronary artery was assessed by high-resolution transthoracic echo-Doppler and expressed as the ratio between coronary flow velocity at peak adenosine and at rest.

RESULTS

At peak DST, reversible perfusion defects on CMR were found in 10 CSX patients (56%) but in none of the control subjects (p = 0.004). The CFR to adenosine in the LAD coronary artery was lower in CSX patients than in control subjects (2.03 +/- 0.63 vs. 3.29 +/- 1.0, p = 0.0004). The CSX patients with DST-induced myocardial perfusion defects in the LAD territory on CMR had a lower CFR to adenosine compared with those without perfusion defects in the LAD territory (1.69 +/- 0.5 vs. 2.31 +/- 0.6, p = 0.01). A significant correlation was found in CSX patients between CFR to adenosine and a DST perfusion defect score on CMR in the LAD territory (r = -0.45, p = 0.019).

CONCLUSIONS

Our data concurrently show DST-induced myocardial perfusion defects on CMR and reduced CFR in the LAD coronary artery territory in CSX patients, thus giving strong evidence that a dysfunction of coronary microcirculation resulting in myocardial perfusion abnormalities is present in these patients.

Myocardial perfusion in patients with typical chest pain and normal angiogram

BACKGROUND

Approximately 10-30% of patients with typical chest pain present normal epicardial coronaries. In a proportion of these patients, angina is attributed to microvascular dysfunction. Previous studies investigating whether angina is the result of abnormal resting or stress perfusion are controversial but limited by varying inclusion criteria. Therefore, we investigated whether microvascular dysfunction in these patients is associated with perfusion abnormalities at rest or at stress.

PATIENTS AND METHODS

In 58 patients (39 female, 19 male, mean age 58+/-10 years) with angina and normal angiogram as well as 10 control patients with atypical chest pain and normal coronaries (six female, four male, mean age 53+/-11 years) myocardial blood flow (MBF) was measured at rest and under dipyridamole using 13N-ammonia PET. Resting MBF and coronary flow reserve (CFR) as the ratio of hyperaemic to resting MBF were corrected for rate-pressure-product (RPP): normalized resting MBF (MBFn)=MBFx10,000/RPP and CFRn=CFRxRPP/10,000.

RESULTS

Sixteen/58 patients had a normal CFRn (=2.5; group I; CFRn: 3.1+/-0.88); the same as the controls (CFRn: 3.3+/-0.74). Forty-two/58 patients presented a reduced CFRn (group II; CFRn: 1.78+/-0.57). Group II had both a higher MBFn (group II: 1.30+/-0.33 vs. Group I: 1.03+/-0.26; P<0.05 and vs. controls: 1.07+/-0.19; P<0.01) and a lower hyperaemic MBF (group II: 2.25+/-0.76 mL g-1 min-1 vs. Group I: 3.07+/-0.78 mL g-1 min-1; P<0.001 and vs. controls: 3.41+/-0.94 mL g-1 min-1; P<0.0001).

CONCLUSION

Impaired CFRn in patients with typical angina and normal angiogram is owing to both an increased resting and reduced hyperaemic MBF. Therefore, PET represents a prerequisite for further studies to optimize treatment in individuals with anginal pain and normal coronary angiogram.

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.

Pattern of exercise-induced ST change is related to coronary flow reserve in patients with chest pain and normal coronary angiogram

OBJECTIVE

To evaluate the usefulness of exercise treadmill test in determining the true microvasculature-induced ischemia, we compared the pattern of ST depression with coronary flow reserve (CFR) using transthoracic Doppler echocardiography (TTE) in patients with chest pain and normal coronary angiogram.

DESIGN

Fifty-nine subjects (M/F=21:38, mean age 55+/-9 years) with chest pain and normal coronary angiogram underwent maximal symptom-limited exercise treadmill test (ETT). CFR was estimated with TTE and dipyridamole. Patients with a history of acute myocardial infarction, regional wall motion abnormalities, hypertrophic cardiomyopathy, ejection fraction less than 50%, or primary valvular heart disease were excluded from this study.

RESULTS

No ST change was observed in 20 of 59 (34%) patients, up slope depression was observed in 20 (34%), flat depression in 13 (22%), and down slope depression in 6 (10%). Eleven of thirty nine (28%) exercise positive patients had decreased CFR <2.1. CFR was 3.1+/-0.6 in group with no ST change, 3.1+/-0.6 in group with up slope depression, 2.1+/-0.6 in group with flat depression (p<0.05 versus group with no change and group with upslope depression, respectively), and 2.0+/-0.4 in group with down slope depression (p<0.05 versus group with no change and group with up slope depression, respectively). Flat to down slope depression of ST change during ETT had sensitivity of 58% and specificity of 95% for predicting CFR <2.1.

CONCLUSION

Flat and down slope depression of ST segment during ETT might increase the sensitivity and specificity to detect the true microvasculature-induced ischemia that is defined as CFR less than 2.1 in patients with chest pain and normal coronary angiogram.

Relation between Duke treadmill score and coronary flow reserve using transesophageal Doppler echocardiography in patients with microvascular angina

OBJECTIVES

The link between coronary flow reserve (CFR) and Duke treadmill score (DTS) in patients with microvascular angina remains elusive.

METHODS

We studied 108 subjects (M/F=48:60, mean age 54+/-9 years) with chest pain and normal coronary angiogram. ETT was performed by Bruce's protocol and the equation for calculating DTS was DTS=exercise duration-(5x ST deviation)-(4x exercise angina), with 0=none, 1=nonlimiting, 2=exercise limiting. The coronary flow velocity at diastole (PDV) using transesophageal Doppler echocardiography (TEE) was obtained from the proximal left anterior descending coronary artery and CFR was calculated as the ratio of hyperemic PDV after the intravenous infusion of dipyridamole (0.56 mg/kg) to baseline PDV.

RESULTS

CFR was 3.04+/-0.45 in group with negative ETT and 2.19+/-0.62 in group with positive ETT (P<0.001) and was 1.51+/-0.31 in high risk group with a score of < or = -11, 2.39+/-0.63 in moderate risk group with scores between -11 and + 5, and 3.04+/-0.43 in low risk group with a score of > or = +5 on DTS (P<0.001 versus low risk group, respectively). DTS has significant correlation with CFR (r=0.704, P<0.001).

CONCLUSIONS

DTS is a composite index that reflects CFR and helps clinicians determine the severity of ischemia in patients with microvascular angina.

Cardiac syndrome X. Diagnosis, pathogenesis and management

Patients with cardiac syndrome X (typical chest pain and normal coronary arteriograms) represent a heterogeneous syndrome, which encompasses different pathogenic mechanisms. Although symptoms in most patients with cardiac syndrome X are non-cardiac, a sizable proportion of them have angina pectoris due to transient myocardial ischemia. Thus radionuclide myocardial perfusion defects, coronary sinus oxygen saturation abnormalities and pH changes, myocardial lactate production and stress-induced alterations of cardiac high energy phosphate suggest an ischemic origin of symptoms in at least a proportion of patients with cardiac syndrome X. Microvascular abnormalities, caused by endothelial dysfunction, appear to be responsible for myocardial ischemia in patients with cardiac syndrome X. Endothelial dysfunction is likely to be multifactorial in these patients and it is conceivable that risk factors such as hypertension, hypercholesterolemia, diabetes mellitus and smoking can contribute to its development. Most patients with cardiac syndrome X are postmenopausal women and estrogen deficiency has been therefore proposed as a pathogenic factor in female patients. Additional factors such as abnormal pain perception may contribute to the pathogenesis of chest pain in patients with angina pectoris and normal coronary angiograms. Although prognosis is good regarding survival, patients with cardiac syndrome X have an impaired quality of life. Management of this syndrome represents a major challenge to the treating physician. Understanding the mechanism underlying the condition is of vital importance for patient management. Thus diagnostic tests should aim at identifying the cause of the symptoms in the individual patient, i.e. myocardial ischemia, increased pain perception, abnormalities of adrenergic tone, non-cardiac mechanisms, etc. Moreover, it is important to bear in mind that treatment of cardiac syndrome X should be mainly directed towards improving quality of life, as prognosis is usually good in these patients. Conventional antianginal agents such nitrates, calcium channel antagonists, beta-adrenoceptor antagonists and nicorandil are effective particularly in patients in whom chest pain and ECG changes are clearly suggestive of myocardial ischemia and in those with objective documentation of ischemia. Angiotensin-converting enzyme inhibitors have been shown to be useful in syndrome X patients with increased adrenergic tone, borderline systemic hypertension, and those with documented endothelial dysfunction. Analgesic interventions of different sorts have been proposed based on the hypothesis that somatic and visceral perception of pain is altered in cardiac syndrome X patients. Pharmacological agents such as imipramine and aminophylline, and neural electrical stimulation techniques have been assessed in recent years with encouraging results. Psychological treatment, particularly cognitive therapy, appears to be useful in defined patient subsets. Relaxation techniques such as transcendental meditation have been successfully used in small studies and shown to improve not only chest pain but also exercise-induced ST segment changes. Reports indicate that these techniques improve quality of life.

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.

Different long-term course between chest pain and exercise-induced ST depression in syndrome X

The aim of the present study was to assess the long-term clinical course of patients with syndrome X, focusing on different courses between exercise-induced ST depression and chest pain. Forty-three patients with syndrome X were followed up for 6.4 +/- 3.8 years. They were divided into the 3 groups according to chest pain: disappeared (n = 24), improved (n = 14), or unchanged (n = 5). No patients had cardiac events and all had a favorable long-term prognosis. In patients showing disappearance of chest pain, exercise-induced ST depression and rate-pressure product (RPP) at peak exercise did not change during follow-up. However, ST depression and RPP decreased significantly in those with improved chest pain. These observations suggest that abnormal pain perception plays an important role in the development of chest pain.

Influence of hemodynamic conditions on fractional flow reserve: parametric analysis of underlying model

Pressure-based fractional flow reserve (FFR) is used clinically to evaluate the functional severity of a coronary stenosis, by predicting relative maximal coronary flow (Q(s)/Q(n)). It is considered to be independent of hemodynamic conditions, which seems unlikely because stenosis resistance is flow dependent. Using a resistive model of an epicardial stenosis (0-80% diameter reduction) in series with the coronary microcirculation at maximal vasodilation, we evaluated FFR for changes in coronary microvascular resistance (R(cor) = 0.2-0.6 mmHg. ml(-1). min), aortic pressure (P(a) = 70-130 mmHg), and coronary outflow pressure (P(b) = 0-15 mmHg). For a given stenosis, FFR increased with decreasing P(a) or increasing R(cor). The sensitivity of FFR to these hemodynamic changes was highest for stenoses of intermediate severity. For P(b) > 0, FFR progressively exceeded Q(s)/Q(n) with increasing stenosis severity unless P(b) was included in the calculation of FFR. Although the P(b)-corrected FFR equaled Q(s)/Q(n) for a given stenosis, both parameters remained equally dependent on hemodynamic conditions, through their direct relationship to both stenosis and coronary resistance.

Review article: the burden of illness of non-cardiac chest pain

BACKGROUND

Non-cardiac chest pain is a common condition affecting approximately one-quarter of the population during their lifetime, but the long-term economic costs of non-cardiac chest pain are poorly defined.

METHODS

A MEDLINE and Current Contents search was performed from 1991 to 2002 using specific keywords. All major articles on the subject of non-cardiac chest pain in this period were reviewed and their reference lists searched.

RESULTS

Limited studies suggest that the majority of those with non-cardiac chest pain do not consult a doctor regarding their symptoms; the drivers of health care seeking are not known. The impact on the quality of life in consulters can be severe, with as many as 36% reporting much lower quality of life levels. The diagnosis of non-cardiac chest pain can be difficult due to the heterogeneous nature of the condition, with significant overlap of gastro-oesophageal reflux disease, chest wall syndromes and psychiatric disease, which may drive up the costs of management. The prognosis appears to be good, but there are conflicting results in long-term studies.

CONCLUSIONS

The costs of non-cardiac chest pain to the health care system are likely to be large and represent a significant proportion of each Western country's health care budget. Further studies are required to determine methods of reducing health care costs.

Abnormal subendocardial perfusion in cardiac syndrome X detected by cardiovascular magnetic resonance imaging

BACKGROUND

In cardiac syndrome X (a syndrome characterized by typical angina, abnormal exercise-test results, and normal coronary arteries), conventional investigations have not found that chest pain is due to myocardial ischemia. Magnetic resonance techniques have higher resolution and therefore may be more sensitive.

METHODS

We performed myocardial-perfusion cardiovascular magnetic resonance imaging in 20 patients with syndrome X and 10 matched controls, both at rest and during an infusion of adenosine. Quantitative perfusion analysis was performed by using the normalized upslope of myocardial signal enhancement to derive the myocardial perfusion index and the myocardial-perfusion reserve index (defined as the ratio of the myocardial perfusion index during stress to the index at rest).

RESULTS

In the controls, the myocardial perfusion index increased in both myocardial layers with adenosine (in the subendocardium, from a mean [+/-SD] of 0.12+/-0.03 to 0.16+/-0.03 [P=0.02]; in the subepicardium, from 0.11+/-0.02 to 0.17+/-0.05 [P=0.002]); in patients with syndrome X, the myocardial perfusion index did not change significantly in the subendocardium (0.13+/-0.02 vs. 0.14+/-0.03, P=0.11; P=0.09 as compared with controls) but increased in the subepicardium (from 0.11+/-0.02 to 0.20+/-0.04, P<0.001; P=0.11 for the comparison with controls). Adenosine provoked chest pain in 95 percent of patients with syndrome X and 40 percent of controls (P<0.001).

CONCLUSIONS

In patients with syndrome X, cardiovascular magnetic resonance imaging demonstrates subendocardial hypoperfusion during the intravenous administration of adenosine, which is associated with intense chest pain. These data support the notion that the chest pain may have an ischemic cause.

Increased heterogeneity of coronary perfusion in patients with early coronary atherosclerosis

BACKGROUND

In patients with typical angina but angiographically normal coronary arteries, abnormal vasomotor function is assumed to be a major underlying cause. However, data on this issue are conflicting, and recent studies suggest that fluid dynamic abnormalities exist in these patients. The aim of the study was to evaluate whether early stages of atherosclerosis are characterized by alterations of baseline coronary hemodynamics and endothelium-independent vasomotion. Besides established intracoronary Doppler parameters, heterogeneity of perfusion was assessed and related to early signs of atherosclerosis as determined by electron-beam computed tomography (EBCT).

METHODS

In 59 patients with typical angina and angiographically normal or near-normal coronary arteries, intracoronary Doppler measurements were performed in all 3 major coronary arteries. Baseline average peak velocity (bAPV) and hyperemic average peak velocity (hAPV) in response to intracoronary injection of adenosine were measured, and coronary flow velocity reserve (CFVR) was calculated. Heterogeneity was assessed as variability of bAPV, hAPV, and CFVR and was calculated as (STD/MEAN). 100. Doppler data were analyzed according to tertiles of the EBCT-derived Agatston calcium score (ie, score 0-1 [lowest tertile], 2-28 [medium tertile], and >28 [highest tertile]).

RESULTS

The mean EBCT-derived Agatston calcium score was 49 +/- 107. No coronary calcium was observed in 17 (29%) patients. The mean values of bAPV, hAPV, and CFVR were not different between the calcium score tertiles. However, patients in the highest tertile had a significantly increased variability index of bAPV (29.6% +/- 11.6%) compared with patients in the lowest tertile (13.4% +/- 7.3%, P <.0001). Variability of CFVR was also increased in these patients (15.5% +/- 11.7% vs 10.5% +/- 4.0%, P =.03).

CONCLUSION

These results indicate that early stages of atherosclerosis are characterized by microvascular abnormalities that do not uniformly affect the myocardium but are heterogeneous. The high variability of baseline coronary flow velocity with increasing coronary calcium suggests that in patients with early stages of atherosclerosis fluid dynamic effects may play a crucial role even in the absence of angiographically appreciable epicardial stenoses.

Microvascular angina in a patient with aortic stenosis

A 39-year-old woman had exercise-induced ST segment depression associated with chest pain. Cardiac evaluation revealed moderate aortic stenosis (AS), related to the bicuspid valves, with an aortic mean pressure gradient of 22 mmHg, a calculated aortic valve area of 1.3 cm2 and normal left ventricular (LV) peak systolic and end-diastolic pressures, but no LV hypertrophy, resulting in normal LV wall stress. Although the coronary arteries were angiographically normal, rapid atrial pacing and an intracoronary papaverine injection revealed a significantly decreased coronary flow reserve (CFR), which may have played an important role in the pathogenesis of angina pectoris in this patient. Though the CFR is usually decreased in patients with AS, as well as in microvascular angina, in this particular case, it appeared to have decreased as a consequence of microvascular dysfunction rather than of AS-related mechanisms.

Abnormal myocardial blood flow distribution in patients with angina pectoris and normal coronary arteriograms

To evaluate coronary microvascular function and its relation to the genesis of chest pain and ST-segment depression during exercise in patients with syndrome X, pacing-induced changes in transmural myocardial blood flow distribution were quantitatively assessed by 2-dimensional myocardial contrast echocardiography. Of 25 patients with a history of chest pain and normal coronary arteries with the negative ergonovine test, 11 had exercise-induced chest pain and ST-segment depression (syndrome X), and 14 did not (controls). Myocardial blood flow distribution before and after pacing stress was assessed by measuring the ratio of the endocardial to epicardial gray level (ie, endo/epi gray level ratio) in the territory of the left anterior descending coronary artery. Pacing-induced chest pain and ST-segment depression were observed in syndrome X, but not in controls. The endo/epi gray level ratio in syndrome X significantly decreased after pacing (from 0.98+/-0.10 to 0.76+/-0.17, p<0.01), but not in controls (from 0.97+/-0.08 to 0.99+/-0.08, NS). Abnormal myocardial blood flow distribution may play an important role in exercise-induced chest pain and ST-segment depression in these patients.

Effects of trimetazidine on clinical symptoms and tolerance of exercise of patients with syndrome X: a preliminary study

BACKGROUND

Trimetazidine diminishes angina and improves tolerance of exercise of patients with ischemic heart disease, and has no influence on blood pressure and heart rate.

OBJECTIVE

To determine the effect of trimetazidine on angina symptoms and exercise tolerance in patients with syndrome X.

METHODS

We investigated the effect of trimetazidine on the clinical symptoms and tolerance of exercise of 34 patients (20 women and 14 men, aged 32-60 years) with syndrome X (angina pectoris, positive result of exercise test, and normal coronary angiogram). The exercise test was performed before initiation of oral administration of trimetazidine therapy (20 mg three times a day) and 1 and 6 months thereafter.

RESULTS

We obtained negative results of exercise treadmill tests for four patients (11.76%) after 1 month and five patients (14.71%) after 6 months of trimetazidine treatment. There was also a decrease in the incidence of effort angina after 6 months of treatment (26 patients or 76.47% before treatment versus 13 patients or 38.23% after 6 months of treatment). The drug had no significant influence on the heart rate and blood pressure. The duration for which patients could exercise was significantly prolonged by 1 month (652.9 +/- 206.2 versus 563.4 +/- 190.4 s, P = 0.0047) and 6 months (650.3 +/- 207.8 s, P = 0.0094) of treatment with trimetazidine.

CONCLUSION

Treatment with trimetazidine decreases signs of angina during exercise and improves tolerance of exercise of patients with syndrome X.

Role of the vascular endothelium in patients with angina pectoris or acute myocardial infarction with normal coronary arteries

Chest pain with normal coronary angiograms is a relatively common syndrome. The mode of presentation of this syndrome includes patients with syndrome X and patients with an acute myocardial infarction and angiographically normal coronary arteries. Different mechanisms have been proposed to elucidate the exact cause and to explain the various clinical presentations in these patients. Abnormalities of pain perception and the presence of oesophageal dysmotility have all been reported in patients with syndrome X. In situ thrombosis or embolization with subsequent clot lysis and recanalization, coronary artery spasm, cocaine abuse, and viral myocarditis have been described as potential mechanisms responsible for an acute myocardial infarction in patients with angiographically normal coronary arteries. Recent data suggest that both microvascular and epicardial endothelial dysfunction may play an important role in the pathophysiological mechanism of the syndrome of stable angina or acute myocardial infarction with normal coronary arteries.

Effect of alpha1-adrenoceptor blockade on coronary vasodilator reserve in cardiac syndrome X

We sought to test the response of the coronary microcirculation to alpha-adrenoceptor blockade in patients with syndrome X (angina, ischemia-like stress electrocardiogram, and a normal coronary arteriogram). The response of the microcirculation was assessed by quantification of coronary vasodilator reserve (the ratio of hyperemic to resting myocardial blood flow). We investigated 28 patients with syndrome X [18 women, age 54.4 (7.6) years]. Myocardial blood flow was measured at rest and after dipyridamole by using positron emission tomography with H(2)15O. The measurements were made before and after treatment for 10 days with doxazosin (1 mg o.d. for 3 days, followed by 2 mg o.d. for 7 days) or a matched placebo, similarly administered. Patients were randomized to alpha1-blockade or to placebo in double-blind fashion. No significant differences were demonstrable between syndrome X patients treated with doxazosin and those receiving placebo, with respect to resting myocardial blood flow, myocardial blood flow after dipyridamole, or coronary vasodilator reserve (the ratio of the latter two). In addition, no relations were demonstrable among myocardial blood flow, coronary vasodilator reserve, development of chest pain after dipyridamole, or development of ischemia-like ECG changes. Doxazosin had no effect on the perception of chest pain after dipyridamole. No differences were found between the effects of alpha1-blockade with doxazosin or those of placebo with respect to myocardial blood flow in syndrome X. The values obtained for myocardial blood flow and coronary vasodilator reserve for the patients were within the normal range. The data do not support the case for alpha1-mediated vasoconstriction having an etiologic role in the chest pain of syndrome X.

Impaired exercise performance but normal skeletal muscle characteristics in female syndrome X patients

Pathophysiologic mechanisms in syndrome X (anginal chest pain, positive exercise stress test, and angiographically normal coronary arteries) have been extensively studied. Recent reports suggest an ischemic origin of the pain to be less probable. Other contributing mechanisms that have been hypothesized are enhanced sympathetic drive or sensitivity or an abnormal muscle metabolism. Our aim in this study was to characterize exercise performance, skeletal muscle characteristics, and sympathetic control of blood flow in patients with syndrome X. Seven female patients aged 50 to 65 years and 5 matched controls were tested. Exercise test was performed according to clinical routine. Plasma catecholamine and blood lactate levels were measured before, during, and after exercise. Autonomic blood flow control was measured plethysmographically in the resting contralateral forearm during isometric handgrip. Muscle biopsy specimens were obtained at rest from the lateral part of Musculus vastus at midthigh. The biopsy samples were investigated for the relative number of different fiber types, phosphagen content, and energy charge, calculated as (adenosine triphosphate +/- 1/2 adenosine diphosphate)/[adenosine triphosphate +/- adenosine diphosphate +/- adenosine monophosphate]). Exercise capacity was markedly decreased in syndrome X compared with controls (85 +/- 14 vs 156 +/- 11 W, p <0.0005) and all patients discontinued exercise because of chest pain (Borg CR-10, 5 +/- 3). Peak heart rate was lower in syndrome X (150 +/- 18 vs 176 +/- 7 beats/min, p <0.01), whereas systolic blood pressure and double product did not differ. Peak norepinephrine plasma levels were lower than in controls (11 +/- 6 vs 24 +/- 13 nmol/L, p <0.04), whereas peak blood lactate levels did not differ. Blood flow increase in the resting forearm during isometric handgrip was similar to that in controls. The proportion of different fiber types, phosphagen content, and energy charge were normal. Thus, patients with syndrome X have a reduced physical exercise capacity but no skeletal muscle abnormalities. Catecholamine hypersensitivity may contribute to their condition.

Musculo-skeletal pathology in patients with angina pectoris and normal coronary angiograms

PURPOSE

To evaluate the role of the musculo-skeletal apparatus in patients with angina pectoris despite normal coronary angiograms.

DESIGN

A survey of patients and controls investigated by blinded observers.

SETTING

A tertiary cardiologic referral centre.

SUBJECTS

Thirty women and 18 men (mean age 52.9 years) with chest pain of an average duration of 3 years and 11 months were investigated. All had normal resting electrocardiograms. No patients showed evidence of left ventricular hypertrophy or valvular heart disease on echocardiography and all had a normal coronary angiogram. All had left ventricular ejection fraction > 50%, and none had signs of coronary vasospasm. Eighteen healthy persons (10 women and eight men, mean age 51.2 years) served as controls.

MAIN OUTCOME MEASURES

The group frequency of chest wall complaints, spinal radiograph and physical examination findings; pressure pain thresholds.

RESULTS

The patients had significantly more complaints of pain from the neck, chest, and thoracic spine, and sensations and pain radiating to the arms than the controls. The patients had more degenerative findings on radiograph than the controls, mainly at levels C4-C7. Physical examination showed that abnormal findings were significantly more frequent in patients than in the control group in the anterior and posterior chest wall, in the spine at levels Th1-Th6 and in the muscles of the neck and shoulder girdle. There were no statistically significant differences in pain thresholds or in neurological examination.

CONCLUSION

The musculo-skeletal abnormalities observed in the patients could include reflex mechanisms. Whether the abnormal findings are mainly responsible for the angina pectoris symptoms or merely epiphenomena warrants further study.

Reduced responsiveness to endothelin-1 in peripheral resistance vessels of patients with syndrome X

OBJECTIVES

This study sought to assess the contribution and action of nitric oxide and endothelin-1 in peripheral resistance vessels of patients with syndrome X.

BACKGROUND

Patients with syndrome X may have a generalized disorder of vascular and endothelial function, promoting vasospasm.

METHODS

Changes in blood flow responses to intrabrachial infusion of the endothelium-dependent vasodilators substance P and acetylcholine, the endothelium-independent nitric oxide donor sodium nitroprusside and the endothelin type A (ET(A)) receptor antagonist BQ-123 were assessed using venous occlusion plethysmography in 10 patients with syndrome X and 10 matched control subjects. Vasoconstrictor responses to the nitric oxide synthase inhibitor L-N(G)-monomethyl arginine (L-NMMA) and endothelin-1 were also determined.

RESULTS

There were no significant differences in the responses to acetylcholine, substance P, sodium nitroprusside or BQ-123 between patients and control subjects. However, despite similar degrees of vasoconstriction in response to L-NMMA in both groups, endothelin-1 caused a reduction in forearm blood flow of only 20 +/- 2% in patients with syndrome X compared with 35 +/- 3% in matched control subjects at 90 min (p < 0.001). Although plasma endothelin-1 concentrations were not significantly higher in patients with syndrome X (4.8 vs. 4.0 pg/ml, p = 0.17), the vasoconstriction caused by endothelin-1 infusion correlated inversely with plasma endothelin-1 concentrations (r = -0.51, p = 0.04).

CONCLUSIONS

Patients with syndrome X had normal basal and stimulated nitric oxide activity and basal endogenous ET(A) receptor-mediated vascular tone. However, despite otherwise normal vascular function, there was reduced responsiveness to exogenous endothelin-1, possibly reflecting overactivity of this system and ET(A) receptor downregulation.

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.