Significance of silent myocardial ischemia during exercise testing in patients with coronary artery disease

To evaluate the significance of ischemic ST-segment depression without associated chest pain during exercise testing, data were analyzed from 2,982 patients from the Coronary Artery Surgery Study (CASS) registry who underwent coronary arteriography and exercise testing and were followed up for 7 years. Patients with proved coronary artery disease (CAD) (at least 70% diameter narrowing) were grouped according to whether they had at least 1 mm of ST-segment depression or anginal chest pain during exercise testing. Four hundred twenty-four had ischemic ST depression without angina (group 1); 232 had angina but no ischemic ST depression (group 2); 456 had both ischemic ST depression and angina (group 3); and 471 had neither ischemic ST depression nor angina (group 4). Sixty-three percent of patients in group 1 and 55% in group 2 had multivessel CAD (difference not significant). The 7-year survival rates were similar for patients in groups 1 (76%), 2 (77%), and 3 (78%), but were significantly better for patients in group 4 (88%, p less than 0.001). Among group 1 patients, survival was related to severity of CAD (p less than 0.001). The 7-year survival rate in group 1 was significantly worse than that in a separate group of 282 patients with ischemic ST depression without angina during exercise testing who had no CAD (95% survival, p less than 0.001). Thus, in patients with silent myocardial ischemia during exercise testing, the extent of CAD and the 7-year survival rate are similar to those of patients with angina during exercise testing. Prognosis is determined primarily by the severity of CAD. In patients without CAD, the survival rate is excellent.     

冠心病患者无症状心肌缺血阈的分析

目的：探讨冠心病患者无症状心肌缺血阈的临床意义。方法：应用24h动态心电监测，检测62例冠心病患者心肌缺血阈值、MIT的变异度、每次缺血发作持续时间和ST段最大位移，以及昼夜缺血次数。结果：共检出506次心肌缺血，93．5％在ST段压低时心率加快，夜间心肌缺血阈值较低，但缺血时间及ST段压低程度明显重于昼间。结论：心肌缺血有不同的机制，应根据情况给予不同的治疗。     

Sauna-induced myocardial ischemia in patients with coronary artery disease.

PURPOSE: Sauna bathing is a popular recreational activity that is generally considered to be safe. However, there have been case reports of adverse cardiac events. We sought to determine whether sauna use caused myocardial ischemia in patients with coronary artery disease. METHODS: Sixteen patients with proven coronary artery disease were submitted to three conditions (rest, exercise, and sauna bathing) with continuous electrocardiographic (ECG) monitoring and regular blood pressure measurements. During each condition, patients were injected with Tc-99 sestamibi followed by nuclear scintigraphic imaging. Perfusion defect scores were calculated in 15 patients. RESULTS: Sauna bathing was well tolerated. There was a mean (+/- SD) increase in heart rate of 32% +/- 20% in the sauna (resting mean heart rate = 60 +/- 9 beats per minute vs sauna mean heart rate = 79 +/- 11 beats per minute, P <0.001) and a 13% +/- 6% drop in systolic blood pressure (resting mean systolic blood pressure = 142 +/- 14 mm Hg vs sauna mean systolic blood pressure = 123 +/- 15 mm Hg, P <0.001). There were no arrhythmias or ECG changes in the sauna. Compared with rest, there was significant ischemia during sauna bathing (average perfusion defect score at rest = -0.44 vs average sauna score = -0.93, P <0.001). The perfusion defect score in the sauna was worse than the resting score in 14 of the 15 patients. Sauna-associated perfusion defect scores were highly correlated with exercise-induced scores (R2 = 0.65, P <0.001). CONCLUSION: In patients with stable coronary artery disease, sauna use is clinically well tolerated but is associated with scintigraphically demonstrated myocardial ischemia.     

老年冠心病者无症状心肌缺血阈的分析

目的 探讨老年冠心痛者无症状心肌缺血(SMI)时心肌缺血阈(MIT)的发生规律及临床意义.方法 对128例患者进行24h动态心电图(DCG)检测,观察其MIT值、MIT变异度、每次缺血发作持续时间和ST段最大位移,以及昼夜缺血次数.结果 共检测984阵心肌缺血,其中932阵为SMI,93.6%在ST段压低时心率加快,心率增快的高低与缺血的程度呈正相关,夜间MIT较低,缺血时间及ST压低程度明显重于昼间(P<0.05).结论 DCG是临床上检测SMI的重要方法之一,对临床评估SMI的预后及给药有重要临床意义.     

Prediction of the frequency and duration of ambulatory myocardial ischemia in patients with stable coronary artery disease by determination of the ischemic threshold from exercise testing: importance of the exercise protocol

The relation between ambulatory myocardial ischemia and the results of exercise testing in patients with ischemic heart disease remains undefined, because of the dissimilar results of previous reports. To further investigate this issue and, in particular, to ascertain the importance of the exercise protocol in determining that relation, 70 patients with stable coronary artery disease underwent 48 h ambulatory electrocardiographic (ECG) monitoring and treadmill exercise tests after withdrawal of medications. Patients exercised using two different protocols with slow (National Institutes of Health [NIH] combined protocol) and brisk (Bruce protocol) work load increments. Exercise duration was longer with the NIH combined protocol (14.1 +/- 5 versus 6.8 +/- 2 min; p less than 0.0001), but the maximal work load and peak heart rate achieved were greater with the Bruce protocol (9.8 +/- 2 versus 6.5 +/- 2 METs, and 142 +/- 19 versus 133 +/- 22 beats/min, respectively; p less than 0.0001). A close inverse correlation between exercise testing and the results of ambulatory ECG monitoring was observed using the NIH combined protocol; the strongest correlation was observed between time of exercise at 1 mm of ST segment depression and number of ischemic episodes (r = -0.86; p less than 0.0001). With the Bruce protocol a significantly weaker inverse correlation was found (r = -0.35). The mean heart rate at the onset of ST segment depression was similar during monitoring and during exercise testing with the NIH combined protocol (97.2 +/- 13 versus 101.0 +/- 17 beats/min, respectively) but it was significantly higher (110.4 +/- 13) when using the Bruce protocol (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Exercise-induced myocardial ischemia in patients with coronary artery ectasia without obstructive coronary artery disease

BACKGROUND: Aetiology, clinical significance and treatment options for coronary artery ectasia/aneurysm is not clear. OBJECTIVE: We sought to determine whether exercise can induce coronary ischemia in patients with coronary artery ectasia/aneurysm without significant coronary stenosis. METHODS: Coronary artery ectasia was defined as 1.5-2-fold, aneurysm as >2-fold luminal dilatation of the adjacent normal segment. The study patients could have irregularities with ectatic coronaries but they did not have stenotic lesions >50% with visual assessment of two blinded observers. Patients having coronary artery ectasia or aneurysm with prior myocardial infarction, dilated cardiomyopathy, valvular heart disease, bundle branch block, significant ST-T changes were excluded. The control group was formed from a well matched population of 32 patients with normal coronary arteries who have not performed a treadmill test before coronary angiography. The study group underwent a symptom limited treadmill test if they did not have one before coronary angiogram, all control patients underwent treadmill test. RESULTS: Thirty-three patients with coronary artery ectasia/aneurysm (ranging from one to three vessels) but without significant stenosis were derived from 4470 cardiac catheterization procedures between January 1998 and July 2000. In the study group, 17 of the patients had positive treadmill tests with respect to five patients in the control group (P = 0.004). In subgroup analysis, diffuse ectasia/aneurysm (involving 2-3 vessels) was found to be strongly related with ischemia (P = 0.005) with respect to local disease. CONCLUSION: Coronary artery ectasia/aneurysm may lead to exercise induced ischemia, especially in the diffuse form.     

Painless myocardial ischemia in diabetic patients with coronary artery disease: evaluations by treadmill exercise tests

To elucidate the prevalence and features of painless myocardial ischemia among diabetic patients, 44 consecutive patients with angiographically-documented coronary artery disease and positive treadmill tests were examined. They were 26 with diabetes and 18 without it. Painless myocardial ischemia was defined as the absence of chest pain with 1 mm or more ST segment depression during the exercise stress tests. The severity of ischemia was determined by the magnitude of the ST segment depression. Painless myocardial ischemia was observed in 18 of the 26 (69%) diabetics, and in three of the 18 (17%) non-diabetics (p less than 0.005). The frequency of painless ischemia in the diabetics was relatively high regardless of the severity of ischemia, while painless ischemia was less frequent in the non-diabetics with severe ischemia. With a level of 2.5 mm ST depression, 11 of 12 (92%) diabetics were free of pain compared to four of 11 (36%) non-diabetics (p less than 0.01). Absence of chest pain during the exercise tests was not concordant with prior angina in diabetics, as opposed to non-diabetics in whom both clinical and exercise-induced angina developed concordantly. The diabetic patients without chest pain had a higher prevalence of three major diabetic complications such as neuropathy, nephropathy and retinopathy compared to those developing chest pain (p less than 0.025). It was concluded that in diabetics, painless myocardial ischemia is frequently observed during exercise stress tests and its prevalence is relatively high regardless of the severity of ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)     

"Silent" myocardial ischemia during and after exercise testing in patients with coronary artery disease

Although many patients with coronary artery disease (CAD) have a positive exercise test without pain, the frequency and significance of this "silent" ischemia is unclear. Therefore, we studied 122 consecutive clinically stable patients with angiographically defined CAD (greater than 75 per cent luminal stenosis) and a positive exercise test. Seventy-eight patients had pain or anginal equivalent during or after a positive exercise test; 44 did not, including 32 (26 per cent) with no symptoms at all. Patients were evaluated as to age, sex, prior myocardial infarction, congestive failure, hypertension, diabetes mellitus, and digoxin or propranolol therapy--in addition to anginal symptoms before, during, or after the exercise itself. Extent of CAD, presence of collaterals, and left ventricular ejection fraction were also determined. All exercise tests were evaluated for evidence of ST-T abnormalities or prior infarction on the control ECG as well as peak heart rate during exercise and post-exercise degree of ST segment depression. There were no significant differences between patients with and without exercise-induced pain in regard to any of the clinical and angiographic features noted above, demonstrating that "silent" myocardial ischemia during or after exercise testing is not uncommon and is not readily attributable to any obvious clinical or catheterization findings. Further studies are necessary to determine if patients with evidence of "silent" myocardial ischemia are especially prone to sudden death.     

Sleep-disordered breathing and myocardial ischemia in patients with coronary artery disease

STUDY OBJECTIVES: To examine the occurrence of nocturnal myocardial ischemia and its relationship to sleep-disordered breathing (apneas and oxygen desaturations) in randomly selected men and women undergoing coronary angiography because of angina pectoris. DESIGN: An observational study using an overnight sleep study and Holter recording to examine disordered breathing (oxyhemoglobin desaturations > or = 4% and apnea-hypopneas), heart rates, and ST-segment depressions (> or = 1 mm, > or = 1 min). SETTING: University Hospital, Ume?, a teaching hospital in northern Sweden. PATIENTS: One hundred thirty-two men and 94 women referred for consideration of coronary intervention were randomly included, by lot. RESULTS: ST-segment depressions occurred in 59% (134 of 226) of the patients, and nocturnal ST-segment depressions occurred in 31% (69 of 226). A ST-segment depression occurred within 2 min after an apnea-hypopnea or desaturation in 12% (27 of 226) of patients. This temporal association was seen in 19% of nocturnal ST-segment depressions (71 of 366), more frequently in men (p < 0.01) and in more severely disordered breathing (p < 0.001). Most of these ST-segment depressions were preceded by a series of breathing events: three or more apnea-hypopneas or desaturations or both in 70% (50 of 71). CONCLUSION: Episodes of nocturnal myocardial ischemia are common in patients with angina pectoris. However, a temporal relationship between sleep-disordered breathing and myocardial ischemia is present only in a minority of the patients, but occurs more frequently in men and in more severely disordered breathing.     

Symptomatic and silent myocardial ischemia during exercise testing in coronary artery disease

During exercise by patients with coronary artery disease (CAD), electrocardiographic evidence of myocardial ischemia may precede the onset of angina or may be unassociated with angina, even at peak levels of stress. However, neither the precise incidence of silent versus symptomatic ischemic episodes nor their interrelation in this setting has been clearly defined. The prevalence of silent and symptomatic myocardial ischemia during treadmill exercise testing was determined in 92 patients with angiographically documented CAD. The study group comprised 77 men (84%) and 15 women (16%) of mean age 57 years (range 32 to 79). Exercise testing resulted in ischemic ST-segment depression (greater than or equal to 1 mm for greater than or equal to 80 ms) only or in association with delayed (greater than or equal to 1 minute) angina in 39 patients (42%); angina only or in association with delayed ST-segment depression occurred in 42 patients (46%); and simultaneous occurrence of angina and ST-segment depression was noted in 11 patients (12%). Analysis of clinical, exercise and angiographic factors (age, sex, history of myocardial infarction, heart rate, maximal ST-segment depression, extent of CAD and left ventricular ejection fraction) revealed no significant correlation with the frequency of symptomatic and silent myocardial ischemia during exercise. Asymptomatic myocardial ischemia occurred commonly during exercise in patients with CAD, but there were no differences in the characteristics of patients with symptomatic and asymptomatic episodes.     

醋柳黄酮治疗老年冠心病的疗效观察

目的：观察醋柳黄酮治疗老年冠心病心肌缺血的临床疗效。方法：78例冠心病，随机分为治疗组（40例）与对照组（38例）。对照组常规治疗应用硝酸异山梨酯与阿司匹林。治疗组在常规治疗基础上，加用醋柳黄酮15mg，3次／d，连续3个月。每例于治疗开始前1日与结束次日，进行血脂、血液流变学与动态心电图（Holter）检测。结果：服醋柳黄酮3个月，血清总胆固醇（TC），甘油三酯（TG），低密度脂蛋白-胆固醇（LDL—C）水平明显下降（P〈0．01），高密度指蛋白-胆固醇（HDL—C）水平明显上升（P〈0．05），较对照组显著（P〈0．01）；血液流变学指标如全血粘度、血浆比粘度等均显著下降（P〈0．01或〈0．05），且优于对照组（P〈0．05）。Holter监测示心肌缺血的发作次数及其持续时间，两组均明显减少（P〈0．01、〈0．05），但治疗组减少更著（P〈0．05）。醋柳黄酮治疗未见不良反应。结论：醋柳黄酮有调脂与改善血液流变性作用，治疗老年冠心病安全、有效。     

Silent myocardial ischemia in diabetic and nondiabetic patients with coronary artery disease

Background: Patients with diabetes mellitus are at increased risk for CAD; silent ischemia is reported to be frequent in diabetic populations. The aim of the present study was to evaluate the prevalence of silent ischemia in diabetic and nondiabetic patients with assessed CAD. Methods and results: We recruited a total of 618 patients with CAD: 309 were consecutive diabetic patients and 309 were age- and gender-matched nondiabetic patients. Myocardial ischemia was evaluated both during daily life and during exercise testing. Angina pectoris during daily life was more frequent in diabetic than in nondiabetic patients (80% vs. 74%, P<0.05). The anginal pain intensity either during daily life or acute myocardial infarction (MI), the prevalence of a previous MI, the extent of CAD and ergometric parameters were similar in diabetics and nondiabetics. Silent ischemia during exercise was documented in 179 (58%) diabetics and in 197 (64%) nondiabetics (nonsignificant, ns). Both diabetics and nondiabetics with silent exertional myocardial ischemia differed from symptomatic subjects in higher heart rate values (P<0.01), systolic blood pressure (P<0.01), rate–pressure product (P<0.001), work load (P<0.01) and maximum ST-segment depression at peak exercise (P<0.05). Conclusions: The incidence of silent myocardial ischemia during exercise was similar in diabetic and nondiabetic CAD patients. Surprisingly, diabetics showed a higher prevalence of angina pectoris during daily activity than nondiabetics. A significant association between the presence of symptoms during daily life and exercise was observed in both groups. Our results may contribute to the planning of the clinical management of diabetic CAD patients and confirm the individual attitude to pain of CAD patients independent of the presence of diabetes.     

Variability of transient myocardial ischemia in ambulatory patients with coronary artery disease

Ambulatory electrocardiographic (ECG) monitoring of patients with chronic stable angina has demonstrated frequent and prolonged episodes of ischemic ST segment depression, but its clinical use requires an understanding of the components and extent of variability. Therefore, variations in the frequency and duration of episodes of ST segment depression were evaluated with ambulatory ECG recording at daily, weekly, and monthly intervals in 42 patients with chronic stable angina and known coronary artery disease. Data were analyzed with a nested analysis of variance design that yields estimates of variance components. From the estimates of variance components, power calculations and minimum significant percent reductions in frequency and duration of ischemia were derived. During 4,656 hours of ambulatory ECG monitoring, 1,262 episodes of ischemic ST segment depression were detected. The frequency of episodes was 6.3 +/- 0.45/24 hr (mean +/- SEM), and the duration of episodes was 18.3 +/- 2.8/24 hr. Because of variability over time, the ability to detect significant changes was dependent upon the number of subjects, length of monitoring period, and intervals between monitoring periods. In a clinical trial, for example, a sample size of 25 patients monitored for 48 hours with 1 week between control and test conditions would require a 65% reduction in frequency, whereas a sample size of 50 patients monitored under similar conditions would require a 46% reduction in frequency, to attribute the change with 90% power to a therapeutic intervention rather than to a spontaneous variation. When monitoring a single patient for 48 hours with 1 week or 1 month between control and repeat monitoring sessions, episodes of ischemic ST depression must be eliminated to detect significant therapeutic changes in ischemic activity at the 95% confidence level.(ABSTRACT TRUNCATED AT 250 WORDS)     

Circadian variation of transient myocardial ischemia in patients with coronary artery disease

To examine whether a significant circadian variation of transient myocardial ischemia exists and to better understand the character of such variation, 32 patients with chronic stable symptoms of coronary artery disease underwent one or more days of ambulatory monitoring of ischemic ST segment changes during daily life. A total of 251 episodes of ischemic ST segment depression occurred in 24 (75%) of the 32 patients with a median duration of 5 min (range 1 to 253). A significant circadian increase in ischemic activity was found with 39% of episodes and 46% of total ischemic time occurring between 6 A.M. and 12 P.M. (p less than .05 and p = .02, respectively). In 21 patients with ST segment depression during the 6 hr after waking and the 6 hr before sleep, 68% of episodes occurred in the morning compared with 32% in the evening. There were no significant differences in heart rate at onset, heart rate at 1 min before onset, and activity score associated with ST segment depression. The proportion of minutes showing ST segment depression when the heart rate was above the lowest rate associated with ST segment depression was significantly greater in the morning compared with the evening (26% vs 15%; p = .03). Thus the early morning increase in ST segment depression does not appear to be explained by differences in extrinsic activity and/or stress measured by physical activity score and heart rate response. More importantly, this phenomenon is often ignored by the usual patterns of drug administration for angina.(ABSTRACT TRUNCATED AT 250 WORDS)     

Active transient myocardial ischemia during daily life in asymptomatic patients with positive exercise tests and coronary artery disease

The management of asymptomatic patients with coronary artery disease (CAD) is controversial, and the level of "activity" of their CAD during normal daily life remains largely unknown. To examine this question, ambulatory Holter monitoring of ST segments was performed out of the hospital in 7 asymptomatic subjects with CAD during normal daily activities. Their condition was detected because they all had a silent positive exercise test and angiographically proved CAD. During a total of 384 hours of monitoring, 37 asymptomatic episodes of ST depression (1 mm or greater and lasting at least 30 seconds) were recorded in 5 of the patients. Most episodes (68%) were 10 minutes or less in duration but ranged from 1 to 253 minutes, and most (70%) had a maximal ST depression of 1 to 2 mm. A small increase in heart rate, ranging from 1 to 34 beats/min, preceded 65% of the episodes, but 35% were associated with no change or even a decline before the onset of ischemia. Fifty-four percent of the episodes occurred during rest or usual light physical activity, 8% during sleep and only 38% during exercise, including 1 prolonged bout while jogging. During 78% of the episodes, the subjects rated their mental activity as usual and only 14% occurred during mental stress. In addition, a distinct diurnal variation was noted with 57% of the ischemia occurring between 0600 and 1200 hours (p = 0.008). Therefore, most asymptomatic subjects had active transient ischemia during daily life, with many of the characteristics already described in symptomatic subjects with CAD.     

Effects of the Valsalva maneuver on myocardial ischemia in patients with coronary artery disease.

The influence of the Valsalva maneuver (VM) on myocardial ischemia was evaluated in 24 patients with coronary heart disease. Clinical and hemodynamic responses to the VM were studied during acute ischemia manifested by angina pectoris with transient left ventricular (LV) dysfunction and compared with responses during nonischemic intervals. In the absence of evidence for acute ischemia (angina and increased LV end-diastolic pressure), six patients had abnormal hemodynamic responses to the VM. Five had lack of systolic pressure overshoot and in one, systolic pressure did not decline during straining. When the VM was performed during an ischemic episode, 14 patients had abnormal responses (12 with lack of overshoot in phase IV and two with lack of systolic pressure decline in phase II). In 18 patients a prompt decline in LV end-diastolic pressure occurred with the disappearance of angina during the VM. These changes uniformly occurred during the latter part of straining (VM phase II) as cardiac size and systolic pressure declined. No adverse effects occurred when a VM was performed during acute ischemia. Our observations suggest that the VM abruptly reduces determinants of cardiac oxygen demand, relieving acute ischemia without harmful effects.     

Lack of ouabain effect on pacing-induced myocardial ischemia in patients with coronary artery disease

Sixteen patients with significant two and three vessel coronary artery disease but without clinical congestive heart failure were studied during rapid atrial pacing before and after infusion of 0.015 mg/kg of ouabain. Seven patients with a decreased (less than 50 percent) election fraction and nine patients with a normal election fraction had a significant (P < 0.05) increase in resting arterial systolic pressure after the administration of ouabain. However, resting values for coronary sinus flow, coronary vascular resistance, myocardial oxygen consumption and myocardial lactate extraction did not change significantly in either group. During pacing, patients with a decreased ejection fraction demonstrated more ischemia than patients with a normal ejection fraction; however, the administration of ouabain did not significantly alter pacing-related changes in coronary sinus flow, myocardial oxygen consumption, myocardial lactate extraction, ischemic electrocardiographic changes or onset of chest pain in either group. The administration of ouabain has a negligible effect on coronary hemodynamics, myocardial metabolism or clinical signs of ischemia in patients with coronary artery disease with normal or abnormal left ventricular function.     

Increase in myocardial oxygen consumption indexes by exercise training at onset of ischemia in patients with coronary artery disease

It has been unclear whether exercise training of patients with coronary artery disease increases the level of myocardial oxygen consumption, as indicated by heart rate and double product of heart rate and systolic blood pressure, at which electrocardiographic evidence of myocardial ischemia develops. To assess this question we evaluated the experience of 10 patients with coronary artery disease who underwent a modest-level exercise training program for 6 months. All of these subjects had achieved a training effect, had developed electrocardiographic evidence of ischemia during initial exercise testing, had not increased the amount of cardiac medication taken, and had not been taking digoxin. After completion of the training period, the mean heart rate at which electrocardiographic evidence of ischemia developed increased from 107 +/- 19 to 119 +/- 23 beats/min (p less than .05) and the mean double product increased from 166 +/- 18 to 209 +/- 51 X 10(2) mm Hg X beats/min (p less than .05). Eight of the 10 patients demonstrated an increase in heart rate at onset of ischemia (p less than .02), and seven of the eight in whom double product could be assessed manifested an increase in this parameter at onset of ischemia (p less than .05). Thus the rate of myocardial oxygen consumption at which myocardial ischemia develops, as indirectly assessed by heart rate and double product, can be favorably altered by 6 months of moderate-level exercise training.