Significance of hyperventilation-induced ST segment depression in patients with coronary artery disease

To investigate the significance of hyperventilation-induced ST segment depression, 329 consecutive patients with angina and documented coronary artery disease who underwent hyperventilation and exercise tests during pharmacologic washout were studied. The hyperventilation test induced ST segment depression in 79 patients. In 36 of these 79 patients, the electrocardiographic changes occurred early during overbreathing (Group I), whereas in 26 they occurred late during recovery (Group II). Seventeen patients developed ST segment depression both during over-breathing and during recovery (Group III). Group I patients had a higher frequency of history of angina during exercise, multivessel disease and lower tolerance to exercise as compared with patients in Group II. In Group I, the rate-pressure product at the time to onset of ST depression during overbreathing was similar to that during exercise (152 +/- 24 versus 148 +/- 42; p = NS), whereas in Group II the rate-pressure product at the time to onset of ST depression during recovery was comparable with that under control conditions (104 +/- 30 versus 98 +/- 27; p = NS) and far less than that required to produce ischemia during exercise (104 +/- 30 versus 201 +/- 56; p less than 0.0011). In nine Group III patients, the acute administration of propranolol prevented the early hyperventilation-induced ST segment depression, whereas nifedipine abolished the delayed hyperventilation-induced ST segment depression. These findings suggest that early hyperventilation-induced ST segment depression is due to increased oxygen demand in patients with poor coronary reserve and may be prevented by beta-adrenergic blockers, which are useful for lowering oxygen consumption.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diurnal variation of QT dispersion in patients with and without coronary artery disease

QT dispersion defined as interlead QT variability in a 12-lead electrocardiogram was proposed by Day and associates as a simple method to evaluate the repolarization heterogenicity of the ventricular myocardium. The frequency of onset of myocardial infarction and sudden death has been reported to have a circadian variation, with a peak incidence in the early morning hours. The authors investigated whether there is diurnal variation of QT interval and QT interval dispersion in healthy subjects and in patients with coronary artery disease. The study population consisted of two groups. Group I consisted of 62 subjects without coronary artery disease and group II consisted of 82 patients with coronary artery disease. Twelve-lead ECG was recorded for each patient in the morning (between 7 AM and 8 AM), afternoon (between 3 PM and 5 PM) and at night (between 11 PM and 1 AM), on the day after performance of coronary angiography. QTc dispersion was significantly higher in patients with coronary artery disease than in healthy subjects in the morning hours and afternoon (p<0.001). Although the differences were much prominent in group I than group II, both QTc dispersion of morning and afternoon were significantly greater than those at night. There were no statistically significant differences between group I and group II at nighttime with respect to maximum QTc, minimum QTc intervals, and QTc dispersion (p>0.05). In conclusion, QT dispersion shows diurnal variation with an increase in the morning hours in both patients with coronary artery disease and subjects without coronary artery disease. The mechanism of diurnal variation of QT dispersion in patients with coronary artery disease is quite different from that of healthy subjects.     

Arteriographic features of angina pectoris associated with ST segment depression during coronary arterial spasm

To examine the angiographic features of vasospastic angina associated with ST segment depression, we attempted to analyze the coronary arteriograms of 12 patients who exhibited ST segment depression during the ergonovine provocative test. Right and left coronary arteriograms were obtained successively within a short period when the ergonovine administration revealed ST segment depression. Eight out of 12 patients showed non-total spastic obstructions in one of the major coronary arteries. Among them, a collateral augmentation was found only in one patient. Two cases exhibited the well-developed collateral channels during non-anginal periods and in one case a collateral blood supply was reduced by the spasm occurred in the donating artery. In another one, the collateral circulation did not change during anginal period. Three out of 4 patients who showed total spastic obstructions demonstrated transiently augmented collateral circulation which was supplied by the non-spastic artery. These findings may indicate that ST segment depression during coronary artery spasm could attribute to a subendocardial ischemia caused by an incomplete occlusion of large coronary artery and transient reduction or augmentation of collateral blood flow.     

Left and right heart haemodynamics during spontaneous angina pectoris. Comparison between angina with ST segment depression and angina with ST segment elevation.

The function of both right and left sides of the heart was studied during spontaneous attacks of angina pectoris at rest in 7 patients showing ST depression (type I) and 4 showing ST elevation (type II) during the attack. In none of the 44 type I attacks and 29 type II attacks which were recorded did circulatory changes; the latter were different in the two groups. Type I attacks showed: a) a brief fall in arterial pressure, accompanied by b) a rise of right atrial and pulmonary wedge pressures and c) a decrease of cardiac output, right and left stroke work, the mean rate of systolic ejection, and indirect left ventricular pre-ejection dP/dt. In the course of the attack a hypertensive phase followed, which was paralleled by an increase of heart rate, cardiac output, left and right stroke work, and mean systolic ejection rate, left dP/dt; right atrial pressure and wedge pressure remained raised. All of the circulatory functions started to revert towards the pre-attack levels coincident with the waning phase of the electrocardiographic alteration, the latter occurring either spontaneously or after nitroglycerin. Type II attacks for the entire duration of the electrocardiographic changes showed: a) a reduction of arterial pressure, cardiac output, right and left stroke work, mean systolic ejection rate, and left dP/dt, b) a rise of right atrial and wedge pressures, and c) quite small changes of heart rate. When the electrocardiogram started to revert to the pre-attack aspect, the cardiac function rapidly improved and, after a supernormal phase, returned to the basal levels in about 2 minutes. It is concluded: 1) that no circulatory factor interfering with the mechanical effort of the heart is responsible for eliciting spontaneous angina: 2) that in type I attacks right and left ventricular impairment occurs which recovers rapidly, possibly through a sympathetic compensation; 3) that in type II attachs dysfunction of both sides of the heart occurs and persists throughout the episode of electrocardiographic alteration; 4) that the dynamic impairment is probably more severe in type I than in type II angina.     

心绞痛患者528次缺血性ST段下移分析

83例心绞痛患者经24小时动态心电图监测到528次缺血性ST段下移,分析结果表明:1.在心绞痛患者缺血性ST段下移中,无症状性心肌缺血占75％,发生次数是有症状的3倍;2.缺血性ST段下移,85％与活动有关;3.缺血性ST段下移有明显的昼夜分布规律,上午6—10时为发作高峰,占全天总次数32％。提示在冠心病治疗中应重视包括无症状性心肌缺血在内的总缺血负荷,并结合缺血的昼夜分布规律调整给药时间。     

心绞痛患者QT离散度与经皮腔内冠状动脉成形术的关系

目的 :探讨经皮腔内冠状动脉成形术 ( PTCA)对心绞痛患者 QT及 JT离散度 ( QTd及 JTd)的作用。方法 :测定 5 0例心绞痛患者 (心绞痛组 ) PTCA术前和术后的 QTd及 JTd,并以 5 0例正常冠状动脉者作对照 (对照组 )。结果 :1心绞痛组于 PTCA后 QTd及 JTd显著减小 ( P <0 .0 1) ,而对照组于冠状动脉造影术后 QTd及JTd与术前比较 ,无明显改变。 2与对照组比较 ,心绞痛组 PTCA前 QTd及 JTd明显增大 ( P <0 .0 1)。术后心绞痛组 QTd及 JTd值虽高于对照组 ,但无统计学意义 ( P >0 .0 5 )。结论 :PTCA能使 QTd及 JTd减小     

Antilipolytic therapy in angina pectoris. Reduction of exercise-induced ST segment depression.

A double-blind cross-over study was performed on 12 men sith stable angina pectoris in order to determine the effect of antilipolytic treatment on exercise tolerance and exercise-induced electrocardiographic changes. The men were exercised to the onset of anginal pain using a reproducible and standardized ergometric load. A nicotinic acid analogue was used to reduce plasma free fatty acids and free glycerol before and during exercise testing and to eliminate their post-exercise rise. This was associated with significant reduction of exercise-induced ST segment depression (p less than 0-005), though there was no significant difference in the duration of exercise before the oneset of pain. A change in the prportions of lipid and carbohydrate for oxidation by the ischaemic myocardium, making relatively more glucose available, is a likely explanation.     

食管心房调搏负荷试验心率校正ST段变化对冠心病的诊断价值

目的：探讨经食管心房调搏负荷试验（TEAPT）心率校正ST段变化对冠心病的诊断价值。方法：观察55例正常对照组和38例冠心病组患者的试验结果，测定每一时点心电图ST段压低值，计算最大ST／HR斜率和ΔST／HR指数，并比较其与传统ST段压低标准的诊断效能。结果：正常组最大ST／HR斜率、ΔST／HR指数和ST段标准的95％上限值分别为1．1μV／次／min、0．77μV/次／min和70μV，以此为界限值，最大ST／HR斜率诊断冠心病的敏感性，准确性显著大于传统ST段压低标准（P＜0．05）。结论：食管心房调搏负荷试验无创、安全、经济，最大ST／HR斜率诊断冠心病具有较高的准确性。     

Effects of intravenous glucose during pacing-induced angina pectoris in patients with coronary artery disease.

The effects of hypertonic glucose infusion on the anginal threshold determined by atrial pacing was studied in 14 patients with significant coronary artery disease. After glucose, angina occurred at a significantly lower heart rate and double product (systolic arterial pressure x heart rate), suggesting a decreased tolerance to ischemic stress. No stoichiometric relationship was noted between glucose uptake and lactate production, and there was no evidence that hypertonic glucose infusion resulted in enhanced anaerobic glycolysis in the ischemic myocardium. Acute elevation of plasma glucose levels may not be beneficial to patients with coronary artery disease.     

Effects of angiotensin-converting enzyme inhibition on exercise-induced angina and ST segment depression in patients with microvascular angina

Objectives. This study was conducted to test the hypothesis that angiotensin-converting enzyme inhibition may lessen myocardial ischemia in patients with microvascular angina.Background. Patients with syndrome X (angina pectoris, positive findings on exercise testing and normal coronary arteriogram) have reduced coronary vasodilator reserve (“microvascular angina”, and may show an increased sympathetic drive. Angiotensin-converting enzyme inhibition attenuates sympathetic coronary vasoconstriction in patients with coronary artery disease.Methods. Ten patients (seven women and three men, mean age [±SD] 53 ± 6 years) with syndrome X and a reduced coronary flow reserve underwent a randomized, single-blind, crossover, placebo-controlled study of the effects of the angiotensin-converting enzyme inhibitor enalapril on angina and exercise-induced ST segment depression. Assessment was by symptom-limited treadmill exercise testing after 2 weeks of treatment with 10 mg/day of enalapril and after 2 weeks of placebo administration.Results. All patients had positive findings on exercise testing (≥1 mm ST segment depression and angina) white taking placebo, whereas six patients had a positive test results (four with angina) during enalapril therapy. Total exercise duration and time to 1 mm of ST segment depression were prolonged by enalapril over those obtained with placebo (mean 779 ± 141 vs. 690 ± 148s, p = 0.006 and 690 ± 204 vs. 485 ± 241 s, p = 0.007, respectively). The magnitude of ST segment depression was also less with enalapril than with placebo (mean 1.1 ± 0.4 vs. 1.5 ± 0.2 mm, p = 0.004). Heart rate and blood pressure at peak exercise and at 1 mm of ST depression were not significantly different during placebo and enalapril treatment.Conclusions. Angiotensin-converting enzyme inhibition lessens exercise-induced ischemia in patients with syndrome X and microvascular angina, probably by a direct modulation of coronary microvascular tone, which results in an increased myocardial oxygen supply.     

Effects of intravenous glucose during pacing-induced angina pectoris in patients with coronary artery disease

The effects of hypertonic glucose infusion on the anginal threshold determined by atrial pacing was studied in 14 patients with significant coronary artery disease. After glucose, angina occurred at a significantly lower heart rate and double product (systolic arterial pressure × heart rate), suggesting a decreased tolerance to ischemic stress. No stoichiometric relationship was noted between glucose uptake and lactate production, and there was no evidence that hypertonic glucose infusion resulted in enhanced anaerobic glycolysis in the ischemic myocardium. Acute elevation of plasma glucose levels may not be beneficial to patients with coronary artery disease.     

Anipamil prevents ST depression in patients with stable angina pectoris

Summary The purpose of this study was to examine the 24-hour antiischemic efficacy of once-a-day anipamil compared to placebo in the treatment of patients with stable angina. The study was designed as a double-blind, placebo-controlled crossover study with an initial 3 week single-blind placebo period. The patients received anipamil 80 mg once daily, anipamil 160 mg once daily, and placebo in a randomized order. At the end of each treatment period the patients underwent 24-hour ambulatory ECG recording. Nineteen patients were included, all with typical stable angina pectoris for at least 2 months, exercise test with 0.10 mV horizontal or downsloping ST-segment depression and limited by angina pectoris, and at least 10 attacks of angina pectoris in the initial single-blind placebo period. During the placebo period, a total duration of transient myocardial ischemia 0.10 mV during the 24-hour ambulatory ECG monitoring period was 2263 minutes, 75% of which were asymptomatic. Anipamil 80 mg and 160 mg significantly reduced the duration of episodes to 712 minutes (p<0.001), with 87% asymptomatic, and to 913 minutes (p>0.001), with 92% asymptomatic, respectively. In conclusion, anipamil given once a day is an effective 24-hour antiischemic drug in the treatment of transient myocardial ischemia.     

Impact of coronary collateral circulation on QT dispersion in patients with coronary artery disease

OBJECTIVE: The aim of this study was to assess the effect of coronary collateral circulation (CCC) on QT dispersion (QTD) in coronary artery disease. BACKGROUND: A prolonged QTD has been linked to increased heterogeneity of ventricular repolarization implicated in the genesis of ventricular arrhythmias and has been associated with an adverse prognosis in patients with coronary artery disease. METHOD: CCC and corrected QTD (QTcD) were established in patients who had at least 85% stenosis in the left anterior descending coronary artery or in proximal part or in the body of the right coronary artery. Furthermore, left ventricular function score was determined for all the patients. RESULTS: While CCC was not present (CCC grade 0) in 32 patients, 68 patients were observed with CCC (CCC grade > or =1). Mean QTcD was higher in patients who had CCC grade > or =1 than in patients with grade 0 (64.3+/-3.5 and 46.8+/-2.7, respectively, P=0.002). We detected a significant correlation between the collateral score and QTcD (r=0.354, P=0.001). CCC grade > or =1 patients had higher mean left ventricular function scores than grade 0 patients (P=0.048). Left ventricular function score and QTcD were observed to be correlated (r=0.200, P=0.046). CONCLUSION: CCC in chronic coronary artery disease was not established to have a positive decreasing effect on QTcD. On the contrary, QTcD values were observed to be even higher in patients with well developed CCC. Further research including larger series and long-term follow-up is required to investigate this issue.     

运动负荷试验中心电图QT离散度和缺血性ST段下移对冠心病的诊断价值

目的 分析心电图平板运动负荷试验中QT离散度(QTd)及ST段变化对冠心病的诊断价值。方法 观察158例经冠状动脉造影诊断为冠心病的患者及96例平板运动试验阴性的健康者QTd与ST段的变化。结果 冠心病组较对照组QTd明显延长(P<0.05),其延长程度与心电图ST段压低程度相关,QTd≥60ms对冠心病诊断的准确性优于传统的ST段诊断标准。结论 心电图平板运动试验QT离散度的变化可成为临床诊断及治疗冠心病的新指标。     

Influence of exercise on QT dispersion in hypertensive patients with left ventricular hypertrophy without coronary artery disease

In hypertensive patients with left ventricular hypertrophy (LVH), the influence of exercise on the regional variations in ventricular repolarization is not well understood. The present study compared dispersions of QT and QT apex (QTD and QTaD), which are indices of regional variations in ventricular repolarization, between hypertensive patients with echocardiographic evidence of LVH and those without LVH. Seventy essential hypertensive patients underwent a modified Bruce protocol exercise test, and QTD and QTaD were measured at rest and at peak exercise level. All subjects had undergone coronary angiography and did not have coronary artery disease. None of them showed ST-segment depression during or after exercise. There were 20 patients with LVH and 50 patients without LVH. The QTD and QTaD at rest were not different between the patients with LVH and those without LVH (56+/-32 vs 57+/-28 ms, 52+/-20 vs 49+/-23 ms). At peak exercise level, QTaD was significantly decreased compared with the baseline in hypertensive patients without LVH (49+/-23 to 42+/-16ms, p<0.05), whereas in patients with LVH QTaD increased (52+/-20 to 67+/-17ms, p<0.05). QTaD at peak exercise level was positively correlated with the left ventricular mass index (r=0.357, p=0.0024). These data were unchanged after correction for heart rate using Bazett's equation. In conclusion, QTaD increased after exercise in hypertensive patients with LVH. Inhomogeneity of repolarization is induced by exercise stress in hypertensives with LVH.     

Exercise performance-based outcomes of medically treated patients with coronary artery disease and profound ST segment depression

OBJECTIVES

We sought to determine the relationship between exercise duration and cardiovascular outcomes in patients with profound (≥2 mm) ST segment depression during exercise treadmill testing (ETT).

BACKGROUND

Patients with stable symptoms but profound ST segment depression during ETT are often referred for a coronary intervention on the basis that presumed severe coronary artery disease (CAD) will lead to unfavorable cardiovascular outcomes, irrespective of symptomatic and functional status. We hypothesized that good exercise tolerance in such patients treated medically is associated with favorable long-term outcomes.

METHODS

We prospectively followed 203 consecutive patients (181 men; mean age 73 years) with known stable CAD and ≥2 mm ST segment depression who are performing ETT according to the Bruce protocol for an average of 41 months. The primary end point was occurrence of myocardial infarction (MI) or death.

RESULTS

Eight (20%) of 40 patients with an initial ETT exercise duration ≤6 min developed MI or died, as compared with five (6%) of 84 patients who exercised between 6 and 9 min and three (3.8%) of 79 patients who exercised ≥9 min (p = 0.01). Compared with patients who exercised ≤6 min, increased ETT duration was significantly associated with a reduced risk of MI/death (6 to 9 min: relative risk [RR] = 0.25, 95% confidence interval [CI] 0.08 to 0.76; >9 min: RR = 0.14, 95% CI 0.04 to 0.53). This protective effect persisted after adjustment for potentially confounding variables. We observed a 23% reduction in MI/death for each additional minute of exercise the patient was able to complete during the index ETT.

CONCLUSIONS

Optimal medical management in stable patients with CAD with profound exercise-induced ST segment depression but good ETT duration is an appropriate alternative to coronary revascularization and is associated with low rates of MI and death.