Value of measuring end tidal partial pressure of carbon dioxide as an adjunct to treadmill exercise testing

The end tidal partial pressure of carbon dioxide (Pco₂) was measured during treadmill exercise in 30 normal controls and 113 patients referred for assessment of chest pain. Among the 92 patients without significant ST depression hypocapnia occurred more often in those reporting “typical” than “atypical” chest pain (17 of 22 patients compared with 29 of 70; p<0·01). Hypocapnia was uncommon in patients with significant ST depression whether reporting typical or atypical chest pain (one of 10 patients and two of 11, respectively).Hypocapnia at rest (Pco₂ <4 kPa) occurred in 16 (14%) patients but in only one control. Hypocapnia occurred during or after exercise in only one control and three of the 21 patients with significant ST depression on exercise (group 1). The remaining 92 patients were divided into those with a history suggestive of hyperventilation (group 2; n=30) and those without (group 3; n=62). Hypocapnia developed significantly more often in both these groups (21 and 25 patients respectively) than in controls or patients with significant ST depression.An abnormal response of the Pco₂ to exercise provided objective data to support a clinical suspicion of chest pain induced by hyperventilation in 24 cases, suggested a cause for equivocal ST depression other than coronary stenosis in five patients, and led to the diagnosis of previously unsuspected respiratory disease in 14 patients.Measurement of end tidal Pco₂ gives additional valuable diagnostic information during the conventional treadmill exercise test in patients with both typical and atypical chest pain.     

The incidence of “Silent” Coronary Heart Disease

In a group of clinically normal male executives subjected to maximal treadmill stress testing, the occurrence of ischemic st segment responses was in all cases unaccompanied by pain, while in a clinically suspect group a large proportion of those having ischemic st segment responses did not have chest pain.While a significant number of persons have no subjective sensation of pain while having ischemic st segment changes on the electrocardiograph during or after maximal treadmill exercise, occasionally atypical pain may occur during or following exercise. Maximal treadmill stress testing is useful in discovering “silent” coronary artery disease.     

Myocardial ischaemia in patients with frequent angina pectoris.

One hundred patients with angina pectoris underwent 16-point electrocardiographic (ECG) mapping of the left hemithorax during a standardised exercise test. Forty-five patients had maximum ST-segment depression at position V5, while 35 had no ECG signs of ischaemia at this position. In 20 V5 was on the edge of the precordial area, which showed less severe ST-depression than the central positions. An Oxford ECG recorder and highspeed analyser were modified and used in 50 of the patients with daily angina for recording ST-segment changes over 24 hours. Serial 24-hour ambulatory recordings from the edge of the precordial area of ischaemia identified during exercise detected a mean of only 14 +/- SD 3% of the episodes of ST-segment changes recorded from the centre of the same area. Only 16 +/- 2% of the episodes detected by ECG were accompanied by chest pain. More episodes occurred between 4 am and 6 am than at any other time during the night. This study shows the importance of recording ECG evidence of ischaemia from the precordial position showing maximum changes during exercise. ECG evidence of ischaemia occurs more frequently than anginal pain. These objective measurements add important information to the frequency of chest pain reported by patients with ischaemic heart disease.     

A Novel Approach to Standard Techniques in the Assessment and Quantification of the Interventricular Systolic Relationship

A 51-year-old female undergoing an outpatient stress echocardiogram to evaluate atypical chest pain developed acute ST elevation in the anterior precordial leads on electrocardiogram following exercise. Echocardiography revealed a severe rise in pulmonary artery systolic pressure (PASP) with marked right ventricular (RV) enlargement and interventricular septum flattening. Subsequently, cardiac catherization confirmed an exercise-induced elevation in PASP and diagnosed pulmonary arterial hypertension without evidence of coronary artery disease. This case suggests that an acute elevation in pulmonary artery pressure with RV dilation may be a potential cause of acute ST elevation during stress testing.     

Thallium 201 Scintigraphy

The radioactive isotope thallium 201 behaves physiologically as a potassium analog, and when injected intravenously accumulates rapidly within the cells of many organs. Uptake of the isotope reflects both regional perfusion and sodium-potassium pump activity. The radionuclide emits 80 keV x-rays which are suitable for scintillation camera imaging.The main clinical application of ²⁰¹TI scintigraphy has been in myocardial imaging. Abnormal uptake of the isotope results in a cold spot on the myocardial image. In patients with coronary artery disease, the differentiation of ischemic and infarcted myocardium is made by comparing images obtained after injecting the radionuclide at the peak of a maximal exercise test with those obtained after injection at rest. Abnormalities due to ischemia usually are seen only on the stress image whereas fixed defects in both rest and stress studies usually indicate areas of infarction or scarring. Some investigators believe that redistribution images obtained four to six hours after stress injection (without administering further ²⁰¹TI) give the same information as a separate rest study. The sensitivity of stress imaging for detecting significant coronary disease is of the order of 80 percent to 95 percent, though computer processing of the images may be necessary to achieve the higher figure. The prediction of the extent of coronary disease from ²⁰¹TI images is less reliable. An abnormal ²⁰¹TI image is not entirely specific for coronary artery disease and the likelihood of an abnormal image being due to this diagnosis varies according to the clinical circumstances.The main clinical value of ²⁰¹TI myocardial imaging is likely to be in the noninvasive screening of patients with atypical chest pain or with ambiguous findings on stress electrocardiographic tests. It has also proved useful in studying patients with variant angina or following a coronary bypass operation. It is doubtful whether the technique is clinically helpful in most patients with suspected or established acute myocardial infarction.Imaging of organs other than the heart with ²⁰¹TI has received much less attention but has been reported in patients with peripheral vascular disease and various primary and secondary neoplasms.     

Effect of naloxone on exercise-induced angina pectoris: a randomized double blind crossover trial

To determine whether endogenous opioids play a role in modulating the appreciation of chest pain in angina pectoris, the specific opioid antagonist, Naloxone, was used. The hypothesis was that the appearance time of ischemic myocardial pain should decrease after Naloxone if centrally mediated pain perception is significantly influenced by the endorphin system in angina pectoris. A randomized double blind clinical trial was conducted in 5 men with effort-induced angina pectoris associated with ST segment changes. Three multi-stage exercise tests, using the Bruce protocol were performed on the same day and time, on three successive weeks. Chest pain was reported 4.3 +/- 0.3 (SEM) minutes after starting exercise on the first or baseline test. On subsequent tests patients received either Naloxone 2 mg IV or a similar volume of saline placebo. Angina pectoris occurred significantly (p. less than 0.05) earlier (1.6 +/- 0.2 minutes) after Naloxone compared to placebo. There were no significant differences in myocardial ischemia indicated by ST segment changes and no significant differences in resting or exercise blood pressure and heart rate between Naloxone and placebo. Thus, these data focus attention on a neglected area of myocardial ischemic pain and suggest that endogenous opioids play a significant role in the recognition of the pain of effort-related angina pectoris.     

'Heads I win, tails you lose': testing directional alternative hypotheses in ecological and evolutionary research

Whenever experiments make a priori predictions about the direction of change in some parameter, one-tailed test statistics offer a potentially large gain in power over the corresponding two-tailed test. This gain is rarely used in ecology and evolution because of (1) the belief that one-tailed procedures are unavailable for most statistical tests and (2) an inherent dilemma in one-tailed tests: how do we handle large parameter changes in the unanticipated direction? The first problem is a misconception, whereas the second is easily resolved by recognizing that one- and two-tailed tests are simply extremes in a continuum of testing options.     

Effect of treadmill exercise testing on serum enzymes and the resting electrocardiogram.

Fifty-three adult male patients with chest pain underwent treadmill exercise stress testing according to the Bruce protocol. The resting 12-lead electrocardiogram (ECG) and serum concentrations of glutamic oxaloacetic transaminase, lactic dehydrogenase creatine phosphokinase and alpha-hydroxybutyrate dehydrogenase were evaluated before, and at 1 and 20 hours after exercise. Twenty-eight subjects (53 percent) had a normal test result, 10 (19 percent) had ischemic ST -segment changes and anginal pain, and 15 (28 percent) were considered to have equivocal results because of an abnormal baseline ECG or the concurrent administration of cardioactive medication. In contrast to earlier reports, no significant changes in the serum enzyme values were seen in any of the three groups orin any individual subject, nor were ECG changes detected after recovery from exercise. The diagnostic evaluation of the exercise ECG must depend upon the demonstration of ischemic ST -segment changes and not upon changes in concentrations of serum enzymes.     

Do emergency tests help in the management of acute medical admissions?

A two year combined retrospective and prospective study of 555 acute medical admissions to a district general hospital was carried out to assess the value of emergency biochemical, haematological, radiological, and electrocardiographic tests in diagnosis and treatment. For the study the tests were considered helpful only if they disclosed an abnormality and resulted in a definite diagnosis or change of treatment which would not have been possible from the history and examination alone. A total of 2372 emergency tests were carried out in the 555 patients who presented with 579 acute medical problems. Only 403 (17%) of the test results were abnormal and, of these, only one third helped in treatment and less than one third helped in diagnosis. The most useful diagnostic tests were serum amylase activity in abdominal pain, the electrocardiogram in chest pain, the chest radiograph in respiratory problems, and cerebrospinal fluid analysis in suspected meningitis or subarachnoid haemorrhage. The most useful tests in treatment were blood sugar value in diabetes, PCO2 in obstructive airways disease, and haemoglobin concentration in gastrointestinal haemorrhage. Of the tests requested by far the most often--blood urea and serum electrolyte concentrations--only 7% gave abnormal results and were rarely of any help in either diagnosis or treatment. Analysis of the reasons for the uncritical use of emergency tests by house officers suggested that better undergraduate training, regular audit by senior members of medical units, abolition of routine investigational procedures, and more selective laboratory reports would help to build up the house officer''s confidence in his own skills of history taking and physical examination without recourse to indiscriminate use of laboratory and other investigations.     

Chest Pain in Adolescents—Functional Consequences

In prospectively evaluating 100 cases of adolescents with chest pain (along with two control groups), 91 were found to have recurrent chest pain; fewer than 5 had a serious organic cause. Significantly higher school absenteeism occurred in patients with either chest or abdominal pain than in patients without pain. Adolescents with chest and abdominal pain were more likely to be high users of medical services than those with no pain. Most adolescents believed that persons their age could have attacks; 44 of those with chest pain thought their symptom was due to a heart attack. The occurrence of chest pain was not influenced by an adolescent''s age, sex, race, smoking status or family structure, nor was it consistently associated with depression. Chest pain is thus a common problem of adolescence that produces considerable functional impairment not attributable to serious underlying disease.     

Socioeconomic variations in responses to chest pain: qualitative study

ObjectiveTo explore and explain socioeconomic variations in perceptions of and behavioural responses to chest pain.DesignQualitative interviews.SettingCommunity based study in Glasgow, Scotland.Participants30 respondents (15 men and 15 women) from a socioeconomically deprived area of Glasgow and 30 respondents (15 men and 15 women) from an affluent area of Glasgow.ResultsResidents of the deprived area reported greater perceived vulnerability to heart disease, stemming from greater exposure to heart disease in family members and greater identification with high risk groups and stereotypes of cardiac patients. This greater perceived vulnerability was not associated with more frequent reporting of presenting to a general practitioner. People from the deprived area reported greater exposure to ill health, which allowed them to normalise their chest pain, led to confusion with other conditions, and gave rise to a belief that they were overusing medical services. These factors were associated with a reported tendency not to present with chest pain. Anxiety about presenting among respondents in the deprived area was heightened by self blame and fear that they would be chastised by their general practitioner for their risk behaviours.ConclusionsImportant socioeconomic variations in responses to chest pain may contribute to the known inequities in uptake of secondary cardiology services. Primary care professionals and health promoters should be aware of the ways in which perceptions of symptoms and illness behaviour are shaped by social and cultural factors.

What is already known on this topic

Socioeconomic variations in rates of angiography and revascularisation existAmong socioeconomically deprived patients with a diagnosis of angina, barriers to accessing services include fear, denial, low expectations, and diagnostic confusion

What this study adds

Perceived vulnerability to heart disease is associated with socioeconomic deprivation and is underpinned by positive family history and identification with high risk groups and stereotypesGreater perceived vulnerability to heart disease does not lead to reported presentation in deprived patientsIllness behaviour is influenced by normalisation of chest pain, comorbidity, and poor experience and low expectations of health care, which are more prominent in deprived patients     

Sudden death caused by aortic dissection in a patient with polycystic kidney disease

A 43-year-old man presented at the emergency medical unit with chest pain. The results of a clinical examination were normal, apart from sternum pain (without radiation) on palpation. The patient had no respiratory problems and the pain was relieved by paracetamol. The electrocardiogram, laboratory tests and chest X-ray were normal. However, the man was found dead the next morning. In the autopsy, we noted the presence of haemopericardium, aortic dissection (starting from the vessel's origin and extended to the aortic arch and on through the diaphragm), polycystic kidney disease and liver cysts. In adult autosomal dominant polycystic kidney disease (ADPKD) patients, the main causes of death are ruptured intracerebral aneurysms, coronary artery disease, congestive heart failure, valvular heart disease and ruptured abdominal aortic aneurysms. Aortic dissection is considered to be rare cause of sudden death in ADPKD sufferers. ADPKD can have serious consequences for the vascular system. The families of confirmed ADPKD sufferers must be informed and screened as early as possible, in order to prevent renal and cardiovascular complications.     

Autoantibodies against oxidized LDL are associated with severe chest pain attacks in patients with coronary heart disease

Autoantibodies against oxidized low-density lipoprotein (oxLDL) predict the progression of atherosclerosis. Several studies have shown that oxLDL is present in atherosclerotic lesions and that several factors present in active atherosclerotic plaques can oxidatively modify LDL. Oxidation of LDL induces production of autoantibodies against oxLDL (oxLDLab) that can be measured using an EIA test. Our aim was to see whether oxLDLab are associated with severe chest pain attacks in coronary heart disease (CHD) patients. Patients having two- or three-vessel CHD, as assessed by coronary angiography, and their siblings were recruited into the study (n = 568, mean age 55.8 years, range 29.3–83.2 years). Nondiabetic patients having a history of severe chest pain attacks had significantly higher oxLDLab levels (0.611 ± 0.56) than those who did not have a history of severe chest pain attacks (0.487 ± 0.40) (p = 0.027), even though age, cholesterol level, body mass index, and blood pressure were similar in both groups. However, no difference was found in oxLDLab levels in diabetic patients with or without a history of severe chest pain attacks. Increased levels of oxLDL autoantibodies are associated with severe chest pain attacks in nondiabetic patients with CHD.     

非侵入性起搏器负荷超声心动图对永久起搏器植入术后合并冠脉病变的临床诊断意义

目的：探讨非侵入起搏器负荷超声心动图对永久起搏器植入术后合并冠脉病变的临床诊断意义。方法：采用前瞻性研究,实验对象为24名因房室传导阻滞或慢性心房纤颤而植入永久起搏器的患者（男12人,女12人,平均年龄70.2±6.1岁）,所有患者均因不典型心绞痛入院和完全起搏依赖,心电图改变无法判断是否存在心肌缺血。通过体外程控进行非侵入性起搏器负荷超声心动图检测室壁运动幅度如左室射血分数评估心功能,检测后行冠脉造影术评估冠脉狭窄情况,及实验前后测定B型脑钠肽的变化。结果：24例患者中,有13例通过起搏器负荷超声心动图应激实验测得LVEF随起搏心率增加而降低,这其中又有11例患者通过冠状动脉造影证实其冠脉存在不同程度的狭窄,诊断的准确性84.62%;11例冠脉造影结果阳性的患者实验后30分钟测得的BNP水平较实验前明显升高。结论：非侵入性起搏器负荷超声心动图应激实验作为一种简单、快速、安全及具有诊断意义的方法,可用来评价植入起搏器术后完全起搏依赖,心电图继发性ST-T改变难以判断的心肌缺血,为进一步检查及治疗提供可靠临床数据。     

Ergonovine-Provoked Esophageal Spasm During Coronary Angiography

In many patients with chest pain of esophageal origin, findings are normal on routine esophageal manometry and dysmotility develops only upon provocation with ergonovine maleate. Unfortunately, ergonovine may induce myocardial ischemia in patients in whom coronary artery spasm did not occur during previous provocative testing in a cardiac laboratory—limiting its clinical usefulness. We have recorded esophageal pressure simultaneously with ergonovine infusion during angiography in ten patients without significant arterial stenoses. In two patients their usual chest pain developed associated with esophageal spasm and without changes in coronary vessels. Simultaneous performance of angiography and manometry enhanced the diagnostic yield of provocative testing by showing esophageal motility changes. This method may detect significant changes in the esophageal motility, is easy to carry out and does not interfere with angiography. It maximizes the information gained from a single provocative test and avoids the risk of ergonovine infusion outside of a cardiac laboratory.     

Cold pressor test in diagnosis of coronary artery disease: echophonocardiographic method.

The cold pressor test was used to induce myocardial ischaemia in patients with coronary artery disease and the rise in left ventricular filling pressure used as the index of myocardial ischaemia. Left ventricular filling pressure was derived from a non-invasive echophonocardiographic method. A study group of 19 consecutive patients with chest pain underwent the cold pressor test before coronary angiography. Eighteen responded with a rise in filling pressure exceeding 30% and, of these, 17 had serious coronary artery disease (three single vessel, one two vessel, and 13 triple vessel disease; one had coronary artery spasm only). The remaining patient, who showed no rise in filling pressure, did not have coronary artery disease. None of 15 normal controls showed a rise greater than 5% (patients with coronary artery disease versus normal controls p less than 0.001). The cold pressor test would be suitable for patients who cannot or should not exercise and may be combined with exercise electrocardiograms to improve the information content, as it uses a different marker of myocardial ischaemia.     

冠状动脉造影大致正常的胸痛患者临床分析

摘要 目的：探讨有胸痛症状的冠状动脉造影大致正常的患者的临床特点及病因。方法：回顾性分析2019年1月至2021年5月我院收治的有胸痛症状疑诊为冠状动脉粥样硬化性心脏病并行冠状动脉造影的1283例患者,纳入其中冠状动脉造影提示冠状动脉大致正常的患者,比较冠状动脉造影结果大致正常者与冠状动脉造影存在异常的患者的人口学资料、危险因素等,并统计冠状动脉造影结果大致正常者的确定诊断并进行分析。结果：最终纳入91例疑诊为冠心病的冠状动脉造影大致正常的患者。与冠状动脉造影存在异常的1192例患者的相比,冠脉造影大致正常组中无危险因素者占20.1%,单一高危因素者占50.5%,显著高于冠脉造影异常组,而多重高危因素者占28.6%,显著低于冠脉造影异常组（P＜0.05）。91例疑诊为冠心病的冠状动脉造影大致正常的患者中心脏神经官能症及心律失常分别占45例（49.5％）及12例(13.2％)。结论：临床上很多疑诊为冠心病的胸痛患者的冠状动脉造影大致正常,这部分患者与冠状动脉异常的患者相比冠心病的危险因素更少,胸痛由其他原因引起,所以对这部分患者应强调应用无创的检查手段。     

Is it possible to exclude a diagnosis of myocardial damage within six hours of admission to an emergency department? Diagnostic cohort study

ObjectiveTo assess the clinical efficacy and accuracy of an emergency department based six hour rule-out protocol for myocardial damage.DesignDiagnostic cohort study.SettingEmergency department of an inner city university hospital.Participants383 consecutive patients aged over 25 years with chest pain of less than 12 hours'' duration who were at low to moderate risk of acute myocardial infarction.InterventionSerial measurements of creatine kinase MB mass and continuous ST segment monitoring for six hours with 12 leads.ResultsOutcome of the gold standard test was available for 292 patients. On the diagnostic test for the protocol, 53 patients had positive results and 239 patients had negative results. There were 18 false positive results and one false negative result. Sensitivity was 97.2% (95% confidence interval 95.0% to 99.0%), specificity 93.0% (90.0% to 96.0%), the negative predictive value 99.6%, and the positive predictive value 66.0%. The positive likelihood ratio was 13.9 and the negative likelihood ratio 0.03.ConclusionsThe six hour rule-out protocol for myocardial infarction is accurate and efficacious. It can be used in patients presenting to emergency departments with chest pain indicating a low to moderate risk of myocardial infarction.

What is already known on this topic

Many patients with chest pain in emergency departments indicating a low to moderate risk of myocardial infarction are admitted to rule out myocardial damageSome 6% of those discharged have undiagnosed myocardial damage

What this study adds

An emergency department based chest pain assessment unit protocol to rule out myocardial damage is sensitive enough to allow safe discharge of patients at low to moderate risk of myocardial infarction within six hoursSuch units can also reduce the number of patients admitted unnecessarily