Continuous recording of coronary sinus oxygen saturation during atrial pacing in patients with coronary artery disease or with syndrome X

Skin sympathetic nerve activity and ST-segment depression in women

Background

ST-segment depression (ST depression) on exercise electrocardiogram (ECG) and ambulatory ECG monitoring may occur without myocardial ischemia. The mechanisms of nonischemic ST depression remain poorly understood.

Objective

The study sought to test the hypothesis that the magnitudes of skin sympathetic nerve activity (SKNA) correlate negatively with the ST-segment height (ST height) in ambulatory participants.

Methods

We used neuECG (simultaneous recording of SKNA and ECG) to measure ambulatory ST height and average SKNA (aSKNA) in 19 healthy women, 6 women with a history of Takotsubo syndrome (TTS), and 4 women with ischemia and no obstructive coronary arteries (INOCA).

Results

Baseline aSKNA was similar between healthy women, women with TTS, and women with INOCA (1.098 ± 0.291 μV, 0.980 ± 0.061 μV, and 0.919 ± 0.0397 μV, respectively; P = .22). The healthy women had only asymptomatic upsloping ST depression. All participants had a significant (P < .05) negative correlation between ST height and aSKNA. Ischemic episodes (n = 15) were identified in 2 TTS and 4 INOCA participants. The ischemic ST depression was associated with increased heart rate and elevated aSKNA compared with baseline. An analysis of SKNA burst patterns at similar heart rates revealed that SKNA total burst area was significantly higher during ischemic episodes than nonischemic episodes (0.301 ± 0.380 μV·s and 0.165 ± 0.205 μV·s; P = .023) in both the TTS and INOCA participants.

Conclusion

Asymptomatic ST depression in ambulatory women is associated with elevated SKNA. Heightened aSKNA is also noted during ischemic ST depression in women with TTS and INOCA. These findings suggest that ST segment depression is a physiological response to heightened sympathetic tone but may be aggravated by myocardial ischemia.

Cardiomyocyte Na+/H+ Exchanger-1 Activity Is Reduced in Hypoxia

Fully-activated Na⁺/H⁺ exchanger-1 (NHE1) generates the cardiomyocyte's largest trans-membrane extrusion of H⁺ ions for an equimolar influx of Na⁺ ions. This has the desirable effect of clearing excess intracellular acidity, but comes at a large energetic premium because the exchanged Na⁺ ions must ultimately be extruded by the sodium pump, a process that consumes the majority of the heart's non-contractile ATP. We hypothesize that the state of NHE1 activation depends on metabolic resources, which become limiting in periods of myocardial hypoxia. To test this functionally, NHE1 activity was measured in response to in vitro and in vivo hypoxic treatments. NHE1 flux was interrogated as a function of intracellular pH by fluorescence imaging of rodent ventricular myocytes loaded with pH-sensitive dyes BCECF or cSNARF1. Anoxic superfusates promptly inhibited NHE1, tracking the time-course of mitochondrial depolarization. Mass spectrometry of NHE1 immuno-precipitated from Langendorff-perfused anoxic hearts identified Tyr-581 dephosphorylation and Tyr-561 phosphorylation. The latter residue is part of the domain that interacts with phosphatidylinositol 4,5-bisphosphate (PIP₂), a membrane lipid that becomes depleted under metabolic inhibition. Tyr-561 phosphorylation is expected to electrostatically weaken this activatory interaction. To test if a period of hypoxia produces a persistent inhibition of NHE1, measurements under normoxia were performed on myocytes that had been incubated in 2% O₂ for 4 h. NHE1 activity remained inhibited, but the effect was ablated in the presence of Dasatinib, an inhibitor of Abl/Src-family tyrosine kinases. Chronic tissue hypoxia in vivo, attained in a mouse model of anemic hypoxia, also resulted in persistently slower NHE1. In summary, we show that NHE1 responds to oxygen, a physiologically-relevant metabolic regulator, ostensibly to divert ATP for contraction. We describe a novel mechanism of NHE1 inhibition that may be relevant in cardiac disorders featuring altered oxygen metabolism, such as myocardial ischemia and reperfusion injury.

Soluble CD40 ligand expression in stable atherosclerosis: A systematic review and meta-analysis

BACKGROUND AND AIMS

The role of inflammation in atherosclerosis development and expression in different arterial territories is unclear. Soluble CD40 ligand (sCD40L) mediates inflammation and atherogenesis. Through a systematic review and meta-analysis, we assessed whether sCD40L was dysregulated in stable atherosclerosis, irrespective of the diseased arterial territory, and whether this dysregulation differed according to the specific territory.

METHODS

Systematic literature searches were performed in MEDLINE, Cochrane Library, Web of Science, and Embase for studies reporting circulating sCD40L levels in individuals with and without stable atherosclerosis. sCD40L levels were compared using random-effects meta-analysis, weighted by the inverse variance method (study protocol: PROSPERO CRD42020181392).

RESULTS

Fifty-four studies (59 estimates) including 7705 patients and 7841 controls were analyzed. sCD40L levels were found to be increased in patients with atherosclerosis, irrespective of the territory (standardized mean difference [SMD] 0.43, 95% CI 0.29-0.57; 59 estimates; χ² heterogeneity p < 0.001; I² = 92%). SMD was greatest in carotid atherosclerosis (SMD 0.58, 95% CI 0.30-0.86; 17 estimates), followed by coronary (SMD 0.43, 95% CI 0.24-0.62; 33 estimates), lower extremity (SMD 0.26, 95% CI -0.02-0.54; 7 estimates), and renal atherosclerosis (SMD -0.07, 95% CI -2.77-2.64; 2 estimates) (χ² heterogeneity p < 0.001; I² ≥ 80% for all). Subgroup analysis revealed that sCD40L levels were increased in clinical, but not subclinical, atherosclerosis.

CONCLUSIONS

sCD40L levels were increased in stable atherosclerosis, particularly in the carotid and coronary territories. These novel data support sCD40L as a marker of systemic atherosclerosis, possibly with differential roles in specific territories.

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

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

Fractional flow reserve: physiological basis, advantages and limitations, and potential gender differences

Fractional flow reserve (FFR) is a physiological index of the severity of a stenosis in an epicardial coronary artery, based on the pressure differential across the stenosis. Clinicians are increasingly relying on this method because it is independent of baseline flow, relatively simple, and cost effective. The accurate measurement of FFR is predicated on maximal hyperemia being achieved by pharmacological dilation of the downstream resistance vessels (arterioles). When the stenosis causes FFR to be impaired by > 20%, it is considered to be significant and to justify revascularization. A diminished hyperemic response due to microvascular dysfunction can lead to a false normal FFR value, and a misguided clinical decision. The blunted vasodilation could be the result of defects in the signaling pathways modulated (activated or inhibited) by the drug. This might involve a downregulation or reduced number of vascular receptors, endothelial impairment, or an increased activity of an opposing vasoconstricting mechanism, such as the coronary sympathetic nerves or endothelin. There are data to suggest that microvascular dysfunction is more prevalent in post-menopausal women, perhaps due to reduced estrogen levels. The current review discusses the historical background and physiological basis for FFR, its advantages and limitations, and the phenomenon of microvascular dysfunction and its impact on FFR measurements. The question of whether it is warranted to apply gender-specific guidelines in interpreting FFR measurements is addressed.

Monitoring tissue perfusion, oxygenation, and metabolism in critically ill patients

Alterations in oxygen transport and use are integral to the development of multiple organ failure; therefore, the ultimate goal of resuscitation is to restore effective tissue oxygenation and cellular metabolism. Hemodynamic monitoring is the cornerstone of management to promptly identify and appropriately manage (impending) organ dysfunction. Prospective randomized trials have confirmed outcome benefit when preemptive or early treatment is directed toward maintaining or restoring adequate tissue perfusion. However, treatment end points remain controversial, in large part because of current difficulties in determining what constitutes "optimal." Information gained from global whole-body monitoring may not detect regional organ perfusion abnormalities until they are well advanced. Conversely, the ideal "canary" organ that is readily accessible for monitoring, yet offers an early and sensitive indicator of tissue "unwellness," remains to be firmly identified. This review describes techniques available for real-time monitoring of tissue perfusion and metabolism and highlights novel developments that may complement or even supersede current tools.

Myocardial preservation: controlled reperfusion

Reperfusion injury after reestablishing coronary flow by releasing the aortic cross clamp after cardiac surgery with cardioplegic arrest causes myocardial damage and even death. Attenuation of this reperfusion response by controlling the biochemical and physical environment can avoid morbidity and mortality. Use of a warm reperfusate with addition of drugs that are known to decrease reperfusion injury with manipulation of coronary vascular resistance and the physical parameters of the reperfusion environment helps the heart to reestablish coronary perfusion while decreasing the harm produced by the period of ischemia that occurs during cardiac surgery with intermittent cardioplegic arrest.

Two coronary "orphan" diseases in search of clinical consideration: coronary syndromes x and y

We set out to describe the clinical characteristics of patients presenting with acute or stable coronary syndromes and no stenosis in epicardial coronaries. Although the existence of patients who experience typical angina and who have intact epicardial coronaries is well accepted, the pathophysiology of cardiac ischemia in this setting remains poorly understood. In typical coronary syndrome X, it is believed that at least two components play a role: the first is the incapacity of coronary resistance vessels to adapt to situations of increased blood demand, resulting in demand ischemia; the second is an inappropriate transduction or generation or pain stimuli within the central nervous system. These two mechanisms concur to determine episodes of precordial pain and electrocardiogram (ECG) evidence of ischemia during exercise. In contrast, the coronary slow-flow phenomenon, or syndrome Y, is an angiographic finding that is characterized by delayed progression of the contrast medium during coronary angiography. Although the mechanism of this phenomenon remains largely unknown, it has been proposed that it might depend on the presence of inappropriately high resting coronary resistances, causing reduced blood flow and therefore low-flow ischemia and unstable angina. Importantly, the prognosis of many of the patients presenting with coronary slow-flow does not appear to be favorable, with recurrence of acute coronary syndromes and life-threatening arrhythmias. In the present article, we revise the current evidence regarding these two phenomena, and propose that syndrome Y should be considered a separate clinical entity.

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.

Cardiac syndrome X

Cardiac syndrome X, the triad of angina pectoris, a positive exercise electrocardiogram for myocardial ischaemia and angiographically smooth coronary arteries, is frequently associated with debilitating symptomology, increased psychological morbidity and a poor quality of life. While various avenues of research have been undertaken, there are as yet no definitive conclusions regarding the exact pathogenesis of the condition. A number of physiological mechanisms have been explored, including the existence of underlying myocardial ischaemia, suggested endothelial dysfunction, abnormal pain perception, hormonal irregularities and insulin resistance, while the psychological impact of the condition has also been explored. Various treatment regimens have also been the subject of research with varying degrees of success. The heterogeneous nature of the patient population suggests that the mechanistic pathway may be multifactorial, while a comprehensive treatment regimen including both psychosocial and pharmacological interventions may offer the best outcome for patients with cardiac syndrome X.

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.

Coronary hemodynamic and metabolic studies of the coronary slow flow phenomenon

BACKGROUND

The coronary slow flow phenomenon (CSFP) is an angiographic finding characterized by Thrombolysis in Myocardial Infarction (TIMI)-2 flow in the absence of significant large vessel coronary disease. Although clinical and pathological features have been previously described, the underlying pathophysiology has not been fully elucidated. This study investigates the persistence of the phenomenon on serial angiographic studies, coronary hemodynamic findings at rest and during provocative stimuli, and biochemical evidence of inducible myocardial ischemia.

METHODS

Twelve patients with CSFP underwent repeat angiography and coronary sinus canulation that allowed for the assessment of coronary blood flow, transmyocardial lactate, and oxygen extraction. Parameters were assessed at rest and during rapid atrial pacing, cold pressor stimulation, and acetylcholine infusion. Angiographic and coronary hemodynamic findings were compared with 47 patients who underwent angiography and 8 patients who were hemodynamic control subjects, respectively.

RESULTS

Persistent TIMI-2 flow was demonstrated with repeat angiography in only 4 of the patients. However, the corrected TIMI frame count remained delayed compared with that in control subjects. Furthermore, resting coronary sinus oxygen saturation was low compared with control subjects (23% +/- 4% vs 31% +/- 4%; P <.01), reflecting an increased basal coronary vasomotor tone. The coronary vasodilatory response to atrial pacing was similar to that in control subjects; however, several patients exhibited abnormal vasomotor responsiveness to cold pressor and acetylcholine stimuli. There was no evidence of nett myocardial lactate production with atrial pacing.

CONCLUSION

The CSFP is associated with a chronically elevated resting coronary microvascular tone, even when symptoms are relatively quiescent.

[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.

The response of the myocardial metabolism to atrial pacing in patients with coronary slow flow

The pathophysiology of angina pectoris is not precisely known yet in patients who have no coronary lesion but slow coronary flow by angiography. In this study we aim to display metabolic ischemia via atrial pacing to determine the difference of lactate production and arterio-venous O2 content difference (AVO2). Thirty-four patients with slow coronary flow detected by coronary angiography via the TIMI 'frame count' method were included in this study. The resting and stress images from the patients undergoing myocardial perfusion tomography were recorded, pre and postpacing lactate extraction and AVO2 content difference values were calculated. Patients were classified according to their metabolic responses to atrial pacing stress. Group I consisted of 28 patients (18 male, 10 female, mean age 54.42 +/- 9.61) who did not demonstrate metabolic ischemia and group II consisted of six patients (four male, two female, mean age 60 +/- 5.76) who had metabolic ischemia after the procedure. There was no statistically significant difference between prepacing AVO2 content difference in group I (57.38+/-2.05%) and group II (58.23 +/- 2.11%) (P = NS). However postpacing AVO2 content difference of group I and group II was statistically significant (respectively, 57.96+/-2.65 vs. 68.35 +/- 2.15%, P < 0.001). In other words, postpacing AVO2 content difference was unchanged from the basal AVO2 content difference level in group I (respectively, 57.38 +/- 2.05 vs. 57.96 +/- 2.65%; P = NS) in contrast to the postpacing AVO2 content difference which increased significantly in group II (58.23 +/- 2.11 vs. 68.35 +/- 2.15%; P < 0.028). Although basal lactate extraction rates were similar in groups I and II (respectively, 0.24 +/- 0.1 vs. 0.23 +/- 0.18; P = NS), postpacing lactate extraction rates were decreased significantly in the two groups, prominently in group II (0.154 +/- 0.15 vs. -0.471 +/- 0.27; P < 0.0001) which indicated that lactate extraction converted to lactate production. Metabolic ischemia was detected in only 17.6% of patients included in this study and 83.4% of these six patients with proven metabolic ischemia had perfusion defects in scintigraphy. Our data confirmed that angina pectoris was not originated from myocardial ischemia in most of the patients with slow coronary flow. We conclude that perfusion scintigraphy is a reliable and accurate method for detection of true ischemia in this group of patients.

Myocardial ischemia-reperfusion damage after pacing-induced tachycardia in patients with cardiac syndrome X

The presence of myocardial ischemia in syndrome X (chest pain, "ischemia-like" electrocardiogram changes, and normal coronary angiograms) is uncertain possibly because, when focally distributed, it may not cause contractile dysfunction or lactate production. We measured lipid hydroperoxides (ROOHs) and conjugated dienes (CDs), two sensitive, independent markers of ischemia-reperfusion oxidative stress, in paired aortic and great cardiac vein blood samples before and after pacing-induced tachycardia in nine patients with syndrome X. Diagnostic ischemic S-T segment changes during pacing were followed by a consistent increase in ROOH and CD levels in the great cardiac vein (from 4.83 +/- 1.18 micromol/l at baseline to 7.88 +/- 1.12 micromol/l and from 0.038 +/- 0.002 to 0.051 +/- 0.003 arbitrary units, respectively, P < 0.01). In controls, ROOH and CD levels did not change after pacing. The large postpacing cardiac release of lipid peroxidation products, consistently observed in all patients and similar to that previously observed after ischemia caused by percutaneous transluminal coronary angioplasty, is consistent with an ischemic origin of syndrome X.

Abnormal myocardial phosphorus-31 nuclear magnetic resonance spectroscopy in women with chest pain but normal coronary angiograms

BACKGROUND

After hospitalization for chest pain, women are more likely than men to have normal coronary-artery angiograms. In such women, myocardial ischemia in the absence of clinically significant coronary-artery obstruction has long been suspected. Most methods for the detection of the metabolic effects of myocardial ischemia are highly invasive. Phosphorus-31 nuclear magnetic resonance (31P-NMR) spectroscopy is a noninvasive technique that can directly measure high-energy phosphates in the myocardium and identify metabolic evidence of ischemia.

METHODS

We enrolled 35 women who were hospitalized for chest pain but who had no angiographically significant coronary-artery obstructions and 12 age- and weight-matched control women with no evidence of heart disease. Myocardial high-energy phosphates were measured with 31P-NMR spectroscopy at 1.5 tesla before, during, and after isometric handgrip exercise at a level that was 30 percent of the maximal voluntary grip strength. We measured the change in the ratio of phosphocreatine to ATP during exercise.

RESULTS

Seven (20 percent) of the 35 women with chest pain and no angiographically significant stenosis had decreases in the phosphocreatine:ATP ratio during exercise that were more than 2 SD below the mean value in the control subjects without chest pain. There were no significant differences between the two groups with respect to hemodynamic variables at rest and during exercise, risk factors for ischemic heart disease, findings on magnetic resonance imaging and radionuclide perfusion studies of the heart, or changes in brachial flow during the infusion of acetylcholine.

CONCLUSIONS

Our results provide direct evidence of an abnormal metabolic response to handgrip exercise in at least some women with chest pain consistent with the occurrence of myocardial ischemia but no angiographically significant coronary stenoses. The most likely cause is microvascular coronary artery disease.

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.

Clinical follow-up after cessation of chronic electrical neuromodulation in patients with severe coronary artery disease: a prospective randomized controlled study on putative involvement of sympathetic activity

The present study assessed the reoccurrence of myocardial ischemia after withholding electrical neurostimulation. After randomization, in the study or withdrawal group, spinal cord stimulation (SCS) was set active during the first 4 weeks, followed by 4 weeks of withholding stimulation. In the control group, SCS was switched off during 4 weeks before the end of the study. The control group had no crossover period. Measurements were done at baseline, then after 4 and 8 weeks. The first periods at 4 weeks of each sequence of both groups were compared. In addition, a comparison of clinical variables was performed between the study group 4 weeks after withholding stimulation and the control group 4 weeks following randomization. A total number of 24 patients with refractory angina and an implanted spinal cord stimulator were included in the study (n = 12) and control group. Angina pectoris complaints, nitroglycerin intake, ischemia, and heart rate variability using 48-hour ambulatory electrocardiographic monitoring were assessed. In addition, neurohormonal status and symptom-limited aerobic capacity were evaluated. There was no increase of anginal complaints or ischemia after withholding stimulation. Neurohormonal levels and aerobic capacity were not altered. We conclude that there is no adverse clinical rebound phenomenon after withholding neurostimulation in patients with refractory angina pectoris.

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.

Parasympathetic withdrawal antedates dynamic myocardial ischemia in patients with syndrome X

This study was to evaluate the dynamic changes in cardiac autonomic control preceding electrocardiographic (ECG) myocardial ischemia in patients with syndrome X. Twenty-four-hour ambulatory ECG was obtained in 34 consecutive patients in a drug-free state. Fourteen (41%) of them, aged 58.8+/-13.5 years, presented a total of 19 ischemic episodes, mean duration 12.4+/-19.8 min (ranged 1 to 90 min). Heart rate variability was measured for 24 h; for 3 min and 30 min before, and during the 15 min (in five 3-min intervals) immediately antedating ST segment depression; and for another 3 min after ST segment back to normal. There were significant progressive shortenings in sinus cycle lengths over the 30 min preceding myocardial ischemia (-30 vs -3 minute, 822+/-32 ms vs 637+/-23 ins, P<0.05; a decrement of 22.5%). The sinus cycle lengths lengthened after ischemia ceased. High frequency activity, pNNSO and rMSS.D. were significantly reduced from the -30 min baseline to a nidus in the last 3 min before ischemia (P<0.05), whereas low frequency band and low/high frequency ratio did not present significant change. These findings strongly argue that cardiac autonomic control, especially vagal withdrawal, is involved in the pathogenesis of dynamic myocardial ischemia in syndrome X.

Role of abnormal pain sensitivity and behavioral factors in determining chest pain in syndrome X

OBJECTIVES

We sought to investigate whether patients with syndrome X have an abnormal perception of cardiac pain.

BACKGROUND

Previous studies have reported an increased sensitivity to potentially painful cardiac stimuli in patients with syndrome X. However, it is not clear whether this increase is due to an increased perception of pain or to an enhanced tendency to complain.

METHODS

We assessed cardiac sensitivity to pain in 16 patients with syndrome X and 15 control subjects by performing right atrial and ventricular pacing with increasing stimulus intensity (1 to 10 mA) at a rate 5 to 10 beats higher than the patient's heart rate. False and true pacing were performed in random sequence, with both patients and investigators having no knowledge of the type of stimulation being administered.

RESULTS

No control subject had pacing-induced pain; conversely, 8 patients with syndrome X reported angina during atrial pacing (50%, p < 0.01) and 15 during ventricular pacing (94%, p < 0.001). During atrial stimulation, both true and false pacing caused chest pain in a similar proportion of patients (50% vs. 63%, p = 0.61), whereas during ventricular stimulation, true pacing caused chest pain in a higher proportion of patients (94% vs. 50%, p < 0.05). Pain threshold and severity of pain (1 to 10 scale) were similar during true and false atrial pacing, whereas true ventricular pacing resulted in a lower pain threshold (mean +/- SD 3.7 +/- 3.0 vs. 7.9 +/- 2.8 mA, p < 0.001) and a higher level of pain severity (7.3 +/- 2.7 vs. 3.1 +/- 3.5, p < 0.001) than did false pacing.

CONCLUSIONS

Patients with syndrome X frequently reported chest pain even in the absence of cardiac stimulation. Yet, in addition to this increased tendency to complain, they also exhibited a selective enhancement of ventricular painful sensitivity to electrical stimulation.

Comparison of left ventricular function and volumes during transesophageal atrial pacing combined with two-dimensional echocardiography in patients with syndrome X, atherosclerotic coronary artery disease, and normal subjects

Nine patients with syndrome X were compared with 2 groups of patients known to have coronary artery disease (CAD) (8 patients who developed regional wall motion abnormalities [group ECHO+] and 6 patients who showed only ST depression at echo-pacing [group ECG+]) and with 6 healthy volunteer control subjects. Left ventricular function at rest was normal in all patients. End-diastolic and end-systolic volumes (ml/m2) and ejection fraction were calculated at baseline and at peak of echo-pacing using a Simpson's biplane method. No regional wall motion abnormalities were observed during the echo-pacing in patients with syndrome X or in the volunteers. End-diastolic volume decreased in patients with syndrome X, in the volunteers (from 47 +/- 11 to 30 +/- 12 and from 72 +/- 7 to 38 +/- 6, respectively, p <0.01 for both), and in ECG+ patients (from 48 +/- 10 to 33 +/- 6, p <0.05), whereas it did not change in ECHO+ patients. End-systolic volume decreased in patients with syndrome X and in the volunteers (from 17 +/- 5 to 11 +/- 4 and from 28 +/- 6 to 16 +/- 4, respectively, p <0.01 for both), whereas it did not change or else slightly increased in patients with CAD (from 18 +/- 10 to 16 +/- 5 for ECG+ patients and from 19 +/- 5 to 24 +/- 9 for ECHO+ patients, p = NS for both), regardless of whether regional wall motion abnormalities appeared. Ejection fraction decreased in ECG+ and ECHO+ patients (from 64 +/- 12 to 52 +/- 11 and from 62 +/- 9 to 44 +/- 13, respectively, p <0.01 for both), whereas it did not change in patients with syndrome X and in the volunteers (from 64 +/- 8 to 61 +/- 8 and from 61 +/- 7 to 58 +/- 7, respectively, p = NS for both). During echo-pacing in syndrome X patients no regional wall motion was detected. Left ventricular volumes and ejection fraction showed the same patterns of variation in these patients as they did in the healthy control subjects, in contrast with those patients with CAD, whether or not regional wall motion abnormalities appeared in the latter.

Coronary vasomotion in patients with syndrome X: evaluation with positron emission tomography and parametric myocardial perfusion imaging

The aim of this study was to elucidate further the causative mechanism of abnormal coronary vasomotion in patients with syndrome X. In patients with syndrome X, defined as angina pectoris and documented myocardial ischaemia during stress testing with normal findings at coronary angiography, abnormal coronary vasomotion of either the micro- or the macrocirculation has been suggested as the causative mechanism. Accordingly, we evaluated endothelial function, vasodilator reserve, and perfusion heterogeneity in these patients. Twenty-five patients with syndrome X (definitely normal coronary arteriogram, group A), 15 patients with minimal coronary artery disease (group B) and 21 healthy volunteers underwent [13N]ammonia positron emission tomography at rest, during cold pressor stimulation (endothelial function) and during dipyridamole stress testing (vasodilator reserve). Heterogeneity of myocardial perfusion was analysed by parametric polar mapping using a 480-segment model. In both patient groups, resting perfusion was increased compared to the normal subjects: group A, 127+/-31 ml.min-1.100 g-1; group B, 124+/-30 ml.min-1.100 g-1 normal subjects, 105+/-21 ml.min-1.100 g-1 (groups A and B vs normals, P<0.05). These differences were abolished after correction for rate-pressure product. During cold pressor stimulation, the perfusion responses (ratio of cold pressor perfusion to resting perfusion) were similar among the patients and the control subjects (group A, 1.20+/-0.23; group B, 1.24+/-0.22; normal subjects, 1.23+/-0.14). Likewise, during dipyridamole stress testing, perfusion responses were similar among the three groups (group A, 2.71+/-0.67; group B, 2.77+/-1.29; normal subjects, 2. 91+/-1.04). In group A the heterogeneity of resting perfusion, expressed as coefficient of variation, was significantly different from the volunteers (20.1+/-4.5 vs 17.0+/-3.0, P<0.05). In group B (coefficient of variation 19.4+/-3.9) the difference from normal volunteers was not significant. In this study, patients with syndrome X and patients with minimal coronary artery disease showed normal perfusion responses during cold pressor stimulation and dipyridamole stress testing. Our findings therefore suggest that endothelial dysfunction and impaired vasodilator reserve are of no major pathophysiological relevance in patients with syndrome X. Rather, other mechanisms such as increased sympathetic tone and focal release of vasoactive substances may play a role in the pathogenesis of syndrome X.

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.

17-beta-Estradiol therapy lessens angina in postmenopausal women with syndrome X

OBJECTIVES

We sought to investigate the hypothesis that estrogen replacement therapy ameliorates symptoms in postmenopausal women with syndrome X.

BACKGROUND

Syndrome X (angina pectoris, positive findings on exercise electrocardiography and normal results on coronary angiography) frequently occurs in menopausal women. This observation, in conjunction with the known vasoactive properties of estrogens, suggests that estrogen depletion may contribute to the pathogenesis of syndrome X in some women.

METHODS

Twenty-five postmenopausal patients with syndrome X completed a double-blind, placebo-controlled study of the effect of 17-beta-estradiol cutaneous patches (100 micrograms/24 h) on the frequency of chest pain and on exercise tolerance. Patients were randomly assigned to receive either placebo or 17-beta-estradiol patches for 8 weeks and were then crossed over to the other treatment.

RESULTS

During the placebo phase, patients had a mean of 7.3 episodes of chest pain/10 days. A reduction to 3.7 episodes/10 days was observed during the 17-beta-estradiol phase (p < 0.05). No significant differences were observed between the effects of 17-beta-estradiol and placebo on exercise duration or the results of other cardiologic investigations.

CONCLUSIONS

Estrogen replacement reduces the frequency of chest pain and may be a useful new therapeutic option for treating postmenopausal women with syndrome X.

Changes in cardiac autonomic activities in patients with syndrome X. A study of spectral analysis of heart rate variability

The present study was designed to assess cardiac autonomic activities, coronary microvascular function, and their relationship in patients with syndrome X. Control of coronary blood flow is complex, and impaired coronary flow reserve has been attributed as the cause of myocardial ischemia in patients with syndrome X. It is unknown whether cardiac autonomic activities are altered in the presence of coronary microvascular dysfunction in patients with syndrome X. Eighteen patients with syndrome X were studied. Great cardiac vein flow was measured by the thermodilution method and the coronary flow reserve was determined by intravenous dipyridamole (0.56 mg/kg) infusion. Twenty-four-hour ambulatory electrocardiograms were obtained in a drug-free state. Another 14 age- and sex-matched normal subjects served as a control group. The amplitude (in ms) of ultralow (ULF), very-low (VLF), low (LF), and high (HF) frequency bands and total spectra of heart rate variability were measured for twenty-four-hour and every four-hour interval of the day.

Transient autonomic dysfunction precedes ST-segment depression in patients with syndrome X

Increased sympathetic drive has been suggested to play a role in the pathogenesis of syndrome X (angina pectoris, positive exercise testing, and angiographically normal coronary arteries). Heart rate variability (HRV) studies have shown that patients with syndrome X have an imbalance in autonomic nervous system activity (sympathetic predominance). However, it is not known if transient ST-segment depression which occurs in syndrome X during daily activities is related to this autonomic nervous system dysfunction. This study investigates the relation between the response of the autonomic nervous system, as assessed by HRV analysis, and the occurrence of transient ST-segment depression during 24-hour ambulatory electrocardiographic monitoring in 23 patients (4 men and 19 women, mean age 55 +/- 6 years) with syndrome X. The frequency-domain variables of HRV low-frequency (0.04 to 0.15 Hz) and high-frequency (0.15 to 0.40 Hz) power were measured at 6-minute intervals during the 30 minutes preceding the onset of transient ST-segment depression. Fourteen patients (61%) had > or = 1 episode of ST-segment depression in the 24 hours, whereas the remaining 9 patients (39%) had no significant ST-segment change. HRV measures differed according to whether or not ST-segment depression was associated with increased heart rate. Episodes of ST-segment depression associated with increased heart rate were preceded by a reduction of high-frequency power and an increase in the low-frequency--high-frequency ratio, whereas episodes of ST-segment depression not associated with increased heart rate showed no significant HRV changes. Low-frequency power remained unchanged irrespective of heart rate. Thus, in patients with syndrome X, a sympathovagal imbalance (sympathetic predominance due to vagal tone withdrawal) precedes episodes of ST-segment depression that are associated with an increased heart rate.

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

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

Cardiac syndrome X: clinical characteristics and left ventricular function. Long-term follow-up study

OBJECTIVES

Our aim was to study the clinical characteristics and evolution of symptoms and left ventricular function in a clinically homogeneous group of patients with syndrome X (angina pectoris, positive exercise test results and normal coronary arteriograms).

BACKGROUND

The syndrome of angina with normal coronary arteriograms is heterogeneous and encompasses different pathogenetic entities. These characteristics may contribute to the existing controversy concerning the cause of syndrome X.

METHODS

We studied 99 patients with syndrome X (78 women, 21 men; mean age +/- SD 48.5 +/- 8 years). All underwent clinical characterization, ambulatory electrocardiographic (ECG) monitoring and echocardiographic assessment of left ventricular function during a follow-up period of 7 +/- 4 years.

RESULTS

The syndrome was more common in women than in men. Of the women, 61.5% were postmenopausal before the onset of chest pain. All 99 patients had exertional angina, and 41 also had rest angina. The average duration of episodes of chest pain was > 10 min in 53% of patients. Sublingual nitrate was effective for relief of pain in 42% of patients. Transient ST segment depression was observed during ambulatory ECG monitoring in 64 patients and myocardial perfusion abnormalities in 22. During the first stage of the exercise test, 32 patients had an increase > 20 mm Hg in systolic blood pressure and showed an earlier onset of ST depression and shorter exercise time than did patients whose blood pressure increased < or = 20%. During follow-up, no deaths or myocardial infarctions occurred, ventricular function was unchanged (shortening fraction 35.4 +/- 4% vs. 35.6 +/- 3%; heart failure developed in only one patient), systemic hypertension occurred in eight patients and conduction disturbances in four. Symptoms lessened in 11 patients, were variable or unchanged in 64 and worsened in 24.

CONCLUSIONS

Syndrome X, as defined in this study, occurs predominantly in postmenopausal women. Patients usually have chest pain typical for angina, but conventional antianginal treatment is not often successful. Myocardial perfusion abnormalities occur in a small proportion of patients. Long-term survival is not adversely affected, and deterioration of cardiac function rarely occurs.

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

BACKGROUND

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

METHODS AND RESULTS

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

CONCLUSIONS

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

Results of dobutamine stress echocardiography in patients with syndrome X

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

Long-term follow-up of patients initially diagnosed with syndrome X

The clinical course of 30 patients (27 women and 3 men) diagnosed with syndrome X (angina pectoris, positive exercise test and normal coronary arteries) was evaluated during 5-year follow up. Patients were divided at the control examination into 2 groups according to the median value of the heart rate/blood pressure product variation from rest to the first stage of a modified Bruce protocol, as follows: group 1 < or = 1,050 (n = 15) and group 2 > 1,050 mm Hg x beats/min (n = 15). All patients were followed at 6-month intervals during a mean follow-up of 60 +/- 8 months. During follow-up, chest pain was unchanged in 20 patients, decreased in severity and frequency in 9 (7 in group 1, and 2 in group 2), and disappeared in 1 in group 2; 3 patients in group 1 had prolonged episodes of anginal chest pain (> 30 minutes) that needed hospitalization. In group 2, 7 patients developed systemic hypertension, 4 had a progression of exercise-induced left bundle branch block to constant left bundle branch block, and 4 continued to develop rate-dependent block during exercise, but at a reduced heart rate. In the latter 8 patients, left ventricular ejection fraction at rest during follow-up decreased significantly from 61 +/- 6% to 51 +/- 8% (p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

[Continuous monitoring of mixed venous blood oxygen saturation]

Mixed venous oxygen saturation (SvO2), measured on pulmonary artery blood, is a convenient indicator of matching between O2 transport (TaO2) and O2 body consumption (VO2). The measurement technique is based on the haemoglobin reflection spectrophotometry principle using two or three wave lengths. The Fick principle points out that SvO2 depends on five parameters: SvO2 = SaO2 - (VO2/CI x Hb x PO) where SaO2, CI and PO respectively represent arterial O2 saturation, cardiac index and O2 affinity. SvO2 does not always reflect tissue O2 tension: when considering a given value of SvO2, PvO2 will depend upon the position of the oxyhaemoglobin dissociation curve. It is impossible to establish in the absolute a "normal" value of SvO2. However, in most clinical circumstances, an SvO2 ranging from 60 to 80% attests that O2 tissue delivery is appropriate. Under certain conditions a continuous monitoring of SvO2 allows to assess another index such as ventilation-perfusion index or the O2 tissue extraction index. Usually SvO2 variations are more informative than the absolute SvO2 value. However, their interpretation should be cautious. First and foremost, the ability of each of the four main SvO2 determinants to influence the SvO2 is unequal as the numerical ranges of variation of these determinants are very different. Moreover, the attribution of a variation of SvO2 to one of its determinants implies that each of them is independent from the others, a feature which is very rarely seen in clinical practice. Finally as the mathematical relationship between SvO2 and its determinants is linear (SaO2 and VO2), or hyperbolic (CI and Hb), the weight of SaO2 or VO2 is independent of their absolute value, whereas CI or Hb weights will depend on their value. The limits of SvO2 monitoring are linked first to the occurrence of an anaerobic metabolism state when TaO2 becomes too low; SvO2 then just provides informations on the aerobic part of the metabolism. Moreover, SvO2 is just a global indicator for tissue O2 oxygenation status which does not give any indication about regional flow distribution. Therefore, SvO2 enables systemic imbalance supervision only. Finally, the existence of a right-to-left shunt will modify the SvO2 values through various mechanisms. However the SvO2 measured, in the pulmonary artery, remains reliable, whereas the presence of a left-to-right shunt will highly alter SvO2 basal value, only its time course remaining significant. SvO2 monitoring, element of diagnosis and monitoring, as well as a warning signal, has a priori specific indications poorly assessed, so far. (ABSTRACT TRUNCATED AT 400 WORDS)

Relationship between the extent of coronary artery disease and indicators of free radical activity

Clinical studies have demonstrated that patients with coronary artery disease (CAD) have markers suggestive of increased free radical (FR) activity when compared with normal subjects; however, the relationship between the extent of CAD and level of FR markers is not known. The following indices of FR activity, plasma malondialdehyde (MDA), plasma thiols (PSH), red blood cell (RBC) glutathione (GSH), and RBC superoxide dismutase (SOD) were measured in 58 patients admitted for coronary angiography and in 50 matched controls. Regression analysis demonstrated no significant correlation between MDA, PSH, GSH, or SOD, and the angiographic grade which indicated the severity of the CAD. Patients with angiographically proven CAD (median 7.9 nmol/ml IQR 6.9-9.2) and patients with a history suggestive of angina pectoris but normal coronary angiograms (median 8.4 nmol/ml IQR 7.4-9.9) had significantly raised MDA levels compared with the controls (median 6.85 nmol/ml IQR 6.1-7.4), p less than 0.001 and p less than 0.005, respectively. The patients with angiographically proven CAD had significantly lower GSH levels (median 1461 microM IQR 1348-1709, p less than 0.002) compared with the controls (median 1754 microM IQR 1492-1930). Significantly raised SOD levels also were detected in patients with angiographically proven CAD (median 121.8 U/ml RBC, IQR 113.8-143.9) and in patients with a history of suggestive of angina pectoris but normal coronary angiograms (median 146 U/ml RBC, IQR 96.8-156.7) when compared with controls (median 96.3 U/ml RBC, IQR 82.4-115.6), p less than 0.001 and p less than 0.02, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

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)

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.

Regulation of intracellular pH in the myocardium; relevance to pathology

Intracellular pH affects the contractile function of the heart, metabolic reactions, ion exchange and calcium homoeostasis. Numerous studies have concluded that a fall of extracellular pH, by whatever mechanism, causes a fall of contractility by alteration of intracellular pH. Measurement of cytosolic intracellular pH using microelectrodes has confirmed that earlier deduction. Acidosis reduces the slow calcium current and the release of calcium from the sarcoplasmic reticumul but, because the cytosolic calcium does not fall, the major site of action of hydrogen ions appears to be on the calcium sensitivity of the contractile proteins. In man acidosis can be detected 15 s after the occlusion of a coronary artery and is a major mechanism for the simultaneous loss of contractility in ischaemia. A transient alkalosis is not detected in man but has been reported in isolated heart preparations where ATP consumption is low. An imposed mild respiratory acidosis during hypoxia increases the subsequent recovery of mechanical function on reoxygenation whereas a severe acidosis can be harmful. Acidosis in ischaemic may be advantageous due to a cardioplegic effect, inhibition of transsarcolemmal calcium fluxes or a reduction of mitochondrial calcium overload. Calcium uptake on reperfusion or reoxygenation has been linked to an inward movement of sodium in exchange for hydrogen ions on reperfusion and subsequent sodium-calcium exchange. Such a mechanism in its simplest form cannot account for the similar uptake of calcium on reoxygenation and reperfusion. Acidosis is a cause of early contractile failure in ischaemia but the role of acidosis in causing cell necrosis is not established.