Syndrome X revisited

A historical review of experimental imaging of the beating heart coronary microcirculation in vivo

Following a myocardial infarction (MI), the prognosis of patients is highly dependent upon the re-establishment of perfusion not only in the occluded coronary artery, but also within the coronary microcirculation. However, our fundamental understanding of the pathophysiology of the tiniest blood vessels of the heart is limited primarily because no current clinical imaging tools can directly visualise them. Moreover, in vivo experimental studies of the beating heart using intravital imaging have also been hampered due to obvious difficulties related to significant inherent contractile motion, movement of the heart brought about by nearby lungs and its location in an anatomically challenging position for microscopy. However, recent advances in microscopy techniques, and the development of fluorescent reporter mice and fluorescently conjugated antibodies allowing visualisation of vascular structures, thromboinflammatory cells and blood flow, have allowed us to overcome some of these challenges and increase our basic understanding of cardiac microvascular pathophysiology. In this review, the elegant attempts of the pioneers in intravital imaging of the beating heart will be discussed, which focussed on providing new insights into the anatomy and physiology of the healthy heart microvessels. The reviews end with the more recent studies that focussed on disease pathology and increasing our understanding of myocardial thromboinflammatory cell recruitment and flow disturbances, particularly in the setting of diseases such as MI.

The usefulness of plateletcrit to predict cardiac syndrome X in patients with normal coronary angiogram

Introduction

Cardiac syndrome X (CSX) is a clinical entity defined as the triad of typical angina pectoris on exercise, electrocardiographic or metabolic findings of ischemia and normal epicardial coronary arteries. Platelets, whose amount in the blood is indicated with plateletcrit (PCT), play an important role in inflammatory and thrombotic processes and the physiopathology of cardiovascular events.

Aim

To investigate the association between cardiac syndrome X and PCT and platelet count.

Material and methods

A total of 113 patients with normal coronary angiogram were included in the study. Fifty patients with typical chest pain and evidence of myocardial ischemia in non-invasive tests formed the CSX patient group. The control group consisted of 63 age- and gender-matched patients with normal coronary arteries but without angina.

Results

The mean PCT value of the CSX group was significantly higher than that of the control group (0.22 ±0.06 vs. 0.19 ±0.04; respectively, p=0.03). Higher PCT was found to be associated with the presence of CSX in patients with normal coronary arteries by multivariate logistic regression analysis.

Conclusions

We suggest that high PCT may predict the presence of cardiac syndrome X in patients with normal coronary arteries. The value of PCT appears additive to conventional expensive methods commonly used in CSX prediction.

Cardiac syndrome X: current concepts

Cardiac syndrome X is a heterogeneous entity, both clinically and pathophysiologically, encompassing a variety of pathogenic mechanisms. Management of this syndrome represents a major challenge to the treating physician. They often seek medical care because of recurring and disabling chest pain, which may imply repetitive and costly invasive and non-invasive investigations. A careful patient evaluation for underlying pathophysiologic mechanism and exclusion of other causes of chest pain along with attention to various psychological aspects is helpful in reducing the stress and suffering of these patients. This article reviews the available literature on the pathophysiology and current controversies surrounding the management of this difficult to treat condition.

Cardiocytic apoptosis and capillary endothelial swelling as morphological evidence of myocardial ischemia in ventricular biopsies from patients with angina and normal coronary arteriograms

BACKGROUND

The cause of chest pain in patients with normal coronary arteriograms (CAG) remains poorly understood.

METHODS AND RESULTS

Left ventricular endomyocardial biopsies from 11 anginal patients with normal CAG and normal left ventriculograms and from seven anginal patients with coronary stenosis were studied by light and electron microscopy. Biopsies from seven non-anginal patients (non-ischemic electrocardiogram abnormalities but no evident heart or systemic diseases) served as controls. In anginal patients with normal CAG, both cardiocytic diameter (17.2 +/- 5.5 microm) and interstitial space percentage area (37.6 +/- 14.9%) were significantly larger than those (13.7 +/- 0.9 microm, 14.9 +/- 2.9%) in control participants. Some cardiocytic nuclei (1.9% of 2000 randomly selected nuclei) exhibited DNA degradation by in-situ nick-end labeling. Electron microscopy revealed cardiocytic nuclei with distinct apoptotic ultrastructures (2.8% of 200 nuclei), phagocytic degradation of cardiocytic cytoplasm, and capillary endothelial swelling (7.1% of 200 capillary transverse sections). No significant infiltration of inflammatory cells was seen. In anginal patients with coronary narrowing (cardiocytic diameter, 16.8 +/- 1.1 microm; interstitial space, 20.1 +/- 5.8%; DNA degraded nuclei, 1.3%), there were however no apoptotic cardiocytic nuclei or cytoplasm and less capillary endothelial swelling (1.6%) in ultrastructure.

CONCLUSIONS

In biopsies from anginal patients with normal CAG, the presence of cardiocytic hypertrophy and replacement fibrosis are both abnormal. Cardiocytic apoptosis and capillary endothelial swelling, found by others as characteristic of experimental myocardial reperfusion injury, are evident. This supports the possibility of myocardial transient ischemia and reperfusion injury in patients with angina and normal CAG.

Cardiac amyloidosis presenting as microvascular angina--a case report

Cardiac amyloidosis usually presents with heart failure, but rarely leads to coronary insufficiency. The authors report a case of a 69-year-old Japanese woman with cardiac amyloidosis presenting as microvascular angina. She had exertional angina with positive exercise test and normal coronary angiograms. However, heart failure developed, and she died 3 years after symptom onset. On autopsy, coronary arteries were patent. In contrast to that of the epicardial coronary arteries, histologic examination of the heart revealed severe obstructive alterations of the intramural coronary arteries with amyloid. Furthermore, amyloid was present mainly in the endocardium and the intramural coronary arteries, but there was little present in the myocardium. This case was a rare AL amyloidosis. There have been only 4 reported cases of cardiac amyloidosis that presented with exertional angina, a positive exercise test, and normal coronary angiograms and histologic examination.

Coronary microvascular disease in humans

Myocardial perfusion abnormalities occur in the absence of epicardial coronary artery disease in patients with a wide spectrum of cardiovascular disorders including microvascular angina, hypertension and left ventricular hypertrophy, coronary atherosclerosis, hypercholesterolemia, and non-ischemic left ventricular dysfunction. These patients have limited coronary microvascular dilator reserve which occasionally is associated with evidence of myocardial ischemia. Primary microvascular hyperconstriction (spasm) is also proposed to cause myocardial ischemia in a subset of patients with rest angina. There is ample evidence suggesting that endothelial dysfunction contributes to microvascular dysfunction, but the precise mechanism of endothelial dysfunction is not known. Nitric oxide is one of the key molecules which control microvascular tone and therefore coronary blood flow, and its decreased availability appears to be involved under certain conditions. This hypothesis has attracted considerable interest as a new therapeutic strategy for these patients having coronary microvascular derangements caused by divergent cardiovascular diseases.

Angina pectoris caused by coronary microvascular spasm

BACKGROUND

Microvascular angina can occur during exercise and at rest. Reduced vasodilator capacity of the coronary microvessels is implicated as a cause of angina during exercise, but the mechanism of angina at rest is not known. Our aim was to test the hypothesis that primary hyperconstriction (spasm) of coronary microvessels causes myocardial ischaemia at rest.

METHODS

Acetylcholine induces coronary artery spasm in patients with variant angina. We tested the effects of intracoronary acetylcholine at graded doses in 117 consecutive patients with chest pain (at rest, during exertion, or both) and no flow-limiting (>50%) organic stenosis in the large epicardial coronary arteries. We also assessed the metabolism of myocardial lactate during acetylcholine administration in 36 of the patients by measurement of lactate in paired blood samples from the coronary artery and coronary sinus vein.

FINDINGS

Of the 117 patients, 63 (54%) had large-artery spasm, 29 (25%) had microvascular spasm, and 25 (21%) had atypical chest pain. The 29 patients with microvascular spasm developed angina-like chest pain, ischaemic electrocardiogram (ECG) changes, or both spontaneously (two patients) or after administration of acetylcholine (27 patients) without spasm of the large epicardial coronary arteries. Testing of paired samples of arterial and coronary sinus venous blood showed that lactate was produced during angina attack in nine of 11 patients with microvascular spasm. There was more women (p<0.01) and fewer coronary risk factors (p<0.01) in patients with microvascular spasm than in those with large-artery spasm.

INTERPRETATION

Coronary microvascular spasm and resultant myocardial ischaemia may be the cause of chest pain in a subgroup of patients with microvascular angina.

Chest pain is an unreliable measure of ischemia in men and women during PTCA

OBJECTIVE

To investigate the differences between men and women in ischemia-induced pain, the amount of ST-segment deviation (the "ST deviation score"), and the relation between pain intensity and ST deviation score.

DESIGN

Retrospective, comparative descriptive.

SETTING

Cardiac catheterization laboratory of a large, urban, university-affiliated medical center with full cardiac services.

PATIENTS

Adults who underwent percutaneous transluminal coronary angioplasty (PTCA) and had electrocardiographic (ECG) evidence of myocardial ischemia during balloon inflation.

METHODS

Continuous 12-lead ECGs were recorded during balloon inflation in patients undergoing PTCA. Patients rated pain on a scale of 0 to 10. The total ST deviation score equaled baseline ECG ST minus maximal ST deviation; absolute deviations were totaled. Frequencies, measures of central tendency, or chi-square or t tests were used for data analysis with significance established at p < 0.05.

RESULTS

There were no difference in the degree of chest pain between men and women during balloon inflation, nor was ST deviation score associated with pain in either gender. Pain intensity did not correlate with total ST deviation in men (r = 0.02) or women (r = -0.07).

CONCLUSIONS

In this study, pain was a poor indicator of ischemia in both sexes during PTCA, and the degree of pain did not correlate with the magnitude of ST deviation. More than one third of men and more than one fourth of women experienced no chest pain during balloon inflation. Clinicians should consider continuous ST-segment monitoring and patient symptoms to monitor accurately for ischemia.

The puzzle of normal coronary arteries in the patient with chest pain: what to do?

Over one million Americans undergo cardiac catheterization each year because of chest pain, with the expectation that coronary artery disease will be found. However, up to 30%--a subgroup that includes patients with both cardiac and noncardiac pathology--will have angiographically normal coronary arteries. While the prognosis of the group as a whole is excellent, successful management requires a clear understanding of the multiple and varied conditions that can cause this syndrome.

Effects of physical exercise training in syndrome X

Syndrome X categorizes myocardial disease characterized by impaired myocardial flow without macrovessel injury. The pathogenesis of this condition remains obscure. Similarly, therapy is not well defined. We report the effects of physical exercise training in a patient with Syndrome X.

Impaired endothelium-dependent cholinergic coronary vasodilation in patients with angina and normal coronary arteriograms

The coronary vasomotor responses to selective infusion of graded concentrations (10(-6) to 10(-4) M) of acetylcholine into the left anterior descending artery were assessed by quantitative coronary arteriography in 24 patients with normal coronary arteriograms (12 patients with atypical symptoms and 12 patients with typical anginal pain) and 36 patients with coronary artery disease with different degrees of atherosclerosis of the left anterior descending artery. In the patients with normal coronary arteries and atypical chest pain, acetylcholine induced predominantly a vasodilator response, which was maximal during a 10(-5) M acetylcholine infusion. In contrast, in patients with coronary artery disease, acetylcholine caused dose-dependent vasoconstriction, which was observed even if the left anterior descending artery itself was smooth. Marked vasoconstriction was also induced in the patients with typical anginal pain and angiographically normal coronary arteries. In nine of these patients, this constrictor response was associated with anginal pain and electrocardiographic evidence of myocardial ischemia. Intracoronary administration of isosorbide dinitrate (1 mg) relieved the anginal pain and dilated all vessels. These data suggest that 1) patients with normal coronary arteriograms and angina pectoris manifest impairment of endothelium-dependent vasodilation similar to that observed in patients with overt coronary atherosclerosis; and 2) abnormal coronary vasoconstrictor responses resulting from this impairment may contribute to the pathogenesis of myocardial ischemia and angina in these patients.