Suppression of silent ischemia by metoprolol without alteration of morning increase of platelet aggregability in patients with stable coronary artery disease

Circadian influence on inflammatory response during cardiovascular disease

Circadian rhythms follow a 24 h day and night cycle, regulate vital physiological processes, and are especially relevant to cardiovascular growth, renewal, repair, and remodeling. A recent flurry of clinical and experimental studies reveals a profound circadian influence on immune responses in cardiovascular disease. The first section of this review summarizes the importance of circadian rhythms for cardiovascular health and disease. The second section introduces the circadian nature of inflammatory responses. The third section combines these to elucidate a new role for the circadian system, influencing inflammation in heart disease, especially myocardial infarction. Particular focus is on circadian regulation of the NACHT, LRR, and PYD domains-containing protein 3 inflammasome, neutrophils, monocytes/macrophages, and T cells involved in cardiac repair. A role for biological sex is noted. The final section explores circadian influences on inflammation in other major cardiovascular conditions. Circadian regulation of inflammation has profound implications for benefitting the diagnosis, treatment, and prognosis of patients with cardiovascular disease.

Influence of the Cardiomyocyte Circadian Clock on Cardiac Physiology and Pathophysiology

Cardiac function and dysfunction exhibit striking time-of-day-dependent oscillations. Disturbances in both daily rhythms and sleep are associated with increased risk of heart disease, adverse cardiovascular events, and worsening outcomes. For example, the importance of maintaining normal daily rhythms is highlighted by epidemiologic observations that night shift workers present with increased incidence of cardiovascular disease. Rhythmicity in cardiac processes is mediated by a complex interaction between extracardiac (e.g., behaviors and associated neural and humoral fluctuations) and intracardiac influences. Over the course of the day, the intrinsic properties of the myocardium vary at the levels of gene and protein expression, metabolism, responsiveness to extracellular stimuli/stresses, and ion homeostasis, all of which affect contractility (e.g., heart rate and force generation). Over the past decade, the circadian clock within the cardiomyocyte has emerged as an essential mechanism responsible for modulating the intrinsic properties of the heart. Moreover, the critical role of this mechanism is underscored by reports that disruption, through genetic manipulation, results in development of cardiac disease and premature mortality in mice. These findings, in combination with reports that numerous cardiovascular risk factors (e.g., diet, diabetes, aging) distinctly affect the clock in the heart, have led to the hypothesis that aberrant regulation of this mechanism contributes to the etiology of cardiac dysfunction and disease. Here, we provide a comprehensive review on current knowledge regarding known roles of the heart clock and discuss the potential for using these insights for the future development of innovative strategies for the treatment of cardiovascular disease.

Diurnal variation in platelet inhibition by clopidogrel

Morning increase in the occurrence of myocardial infarction, stroke and sudden cardiac death is a well-recognized phenomenon, which is in line with a morning enhancement of platelet aggregation. We investigated whether platelet inhibition during clopidogrel and aspirin therapy varies during the day. Fifty-nine consecutive patients (45 men and 14 women) with first ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary interventions (pPCI) on dual antiplatelet therapy were prospectively enrolled into the study. Blood samples were collected 4 days after start of clopidogrel treatment at 6.00 a.m., 10.00 a.m., 2.00 p.m. and 7.00 p.m. Arachidonic acid and adenosine diphosphate (ADP)-induced platelet aggregation were assessed by impedance aggregometry. Platelet inhibition by clopidogrel was lowest in the midmorning: median ADP-induced platelet aggregation was 55%, 17% and 27% higher at 10.00 a.m. compared to 6.00 a.m., 2.00 p.m. and 7.00 p.m., respectively (p < 0.002). Nonresponsiveness to clopidogrel defined according to the device manufacturer was 2.4-fold more frequent in the midmorning than in the early morning. We observed a more pronounced midmorning increase in ADP-induced platelet aggregation in diabetic patients when compared to non-diabetics. In contrast, no diurnal variation in the antiplatelet effect of aspirin was observed. In conclusion, in patients presenting with STEMI undergoing pPCI, platelet inhibition by clopidogrel is less strong in the midmorning hours. This periodicity in platelet aggregation in patients on dual antiplatelet therapy should be taken into consideration when assessing platelet function in clinical studies.

Modification of the circadian pattern of ventricular tachyarrhythmias by beta-blocker therapy

BACKGROUND

Sudden cardiac death exhibits a circadian variation and predominantly occurs during morning hours, Beta-adrenergic antagonists have shown to blunt this morning peak. However, previous reports studying the effects of beta blockers on the circadian variation did not analyze the underlying cause of sudden cardiac death. It thus remains unclear whether ventricular tachyarrhythmias are influenced by beta-blocker therapy.

HYPOTHESIS

This study tested the hypothesis that beta-blocking agents blunt the morning peak of life-threatening ventricular tachyarrhythmias.

METHODS

In 87 patients who were treated and monitored with an implantable cardioverter defibrillator, the circadian distribution of ventricular tachyarrhythmias terminated by appropriate shocks was analyzed and compared in those receiving beta blockers versus those not receiving beta-blocker therapy.

RESULTS

Tachyarrhythmic episodes in the absence of beta-blocker therapy (n = 344) exhibited a circadian variation with a distinct morning peak (16, 38, 28, and 18% of episodes at 0-6, 6-12, 12-18, and 18-24 h, respectively, p < 0.001). In contrast, tachyarrhythmic episodes during beta-blocker therapy (n = 104) were equally distributed over time (22, 27, 24, and 27% of episodes at 0-6, 6-12, 12-18, and 18-24 h, respectively, p = 0.95). The circadian distribution of episodes was significantly different in patients with and those without beta blockade (p < 0.05).

CONCLUSION

Beta-adrenergic antagonists influence the circadian distribution of malignant ventricular tachyarrhythmias in patients with an implantable cardioverter defibrillator. The blunted morning peak of tachyarrhythmic events during beta blockade supports the hypothesis that a sympathetic surge is involved in the circadian pattern of malignant arrhythmias.

Endogenous circadian rhythm in human motor activity uncoupled from circadian influences on cardiac dynamics

The endogenous circadian pacemaker influences key physiologic functions, such as body temperature and heart rate, and is normally synchronized with the sleep/wake cycle. Epidemiological studies demonstrate a 24-h pattern in adverse cardiovascular events with a peak at approximately 10 a.m. It is unknown whether this pattern in cardiac risk is caused by a day/night pattern of behaviors, including activity level and/or influences from the internal circadian pacemaker. We recently found that a scaling index of cardiac vulnerability has an endogenous circadian peak at the circadian phase corresponding to approximately 10 a.m., which conceivably could contribute to the morning peak in cardiac risk. Here, we test whether this endogenous circadian influence on cardiac dynamics is caused by circadian-mediated changes in motor activity or whether activity and heart rate dynamics are decoupled across the circadian cycle. We analyze high-frequency recordings of motion from young healthy subjects during two complementary protocols that decouple the sleep/wake cycle from the circadian cycle while controlling scheduled behaviors. We find that static activity properties (mean and standard deviation) exhibit significant circadian rhythms with a peak at the circadian phase corresponding to 5-9 p.m. ( approximately 9 h later than the peak in the scale-invariant index of heartbeat fluctuations). In contrast, dynamic characteristics of the temporal scale-invariant organization of activity fluctuations (long-range correlations) do not exhibit a circadian rhythm. These findings suggest that endogenous circadian-mediated activity variations are not responsible for the endogenous circadian rhythm in the scale-invariant structure of heartbeat fluctuations and likely do not contribute to the increase in cardiac risk at approximately 10 a.m.

Silent myocardial ischaemia: clinical relevance and treatment

Transient myocardial ischaemia in the absence of chest pain ('silent ischaemia') commonly occurs in patients with coronary artery disease (CAD) and has important prognostic implications. However, doubts exist as to whether and how silent ischaemia should be managed. In the present article we review current knowledge regarding silent ischaemia and the role of recently developed drugs that may be effective to control its occurrence. Since the description in the 1770s of the syndrome of 'angina pectoris' by William Heberden, the importance of chest pain for the diagnosis of CAD has remained un-abated. However, several decades ago it became apparent that both myocardial infarctions and transient episodes of myocardial ischaemia could occur in the absence of chest pain. Indeed, a large proportion of patients with CAD have both silent and painful myocardial ischaemia as a manifestation of CAD. Whether the presence of asymptomatic ischaemic electrocardiographic changes in patients with CAD has prognostic importance and whether it needs medical or surgical treatment has been a matter of speculation for several decades.

Longitudinal Study of Acute Myocardial Infarction in the Southeast Osaka District From 1988 to 2002

BACKGROUND

Data on clinical characteristics, long-term mortality rates, and factors influencing outcome of acute myocardial infarction (AMI) based on an unselected cohort in the percutaneous coronary intervention (PCI) era are still limited in Japan.

METHODS AND RESULTS

In the present study 415 consecutive patients with AMI who were admitted to hospital within 24 h of symptom onset between January 1988 and December 2002 were studied. There was a marked seasonal variation of AMI with a minimum in summer and a maximum in winter, as well as a marked circadian variation with a significant morning peak. Overall, 45.8% of patients were treated with primary PCI. Increased age and female sex were negatively associated with the probability of undergoing PCI. During the follow-up period (mean duration, 4.01+/-3.41 years), the unadjusted long-term all-cause mortality rate was 21.4%. Multivariate Cox regression analysis showed that age, prior cerebrovascular disease, renal failure, Killip > or =2, and ventricular tachycardia/fibrillation were independent predictors of worse long-term mortality after AMI. Furthermore, the use of PCI was independently associated with favorable long-term survival after AMI.

CONCLUSIONS

Although PCI was associated with a favorable long-term mortality, it remains underused in subsets of patients and increased use may further reduce the long-term mortality rate in Japanese AMI patients.

Endogenous circadian rhythm in an index of cardiac vulnerability independent of changes in behavior

There exists a robust day/night pattern in the incidence of adverse cardiac events with a peak at approximately 10 a.m. This peak traditionally has been attributed to day/night patterns in behaviors affecting cardiac function in vulnerable individuals. However, influences from the endogenous circadian pacemaker independent from behaviors may also affect cardiac control. Heartbeat dynamics under healthy conditions exhibit robust complex fluctuations characterized by self-similar temporal structures, which break down under pathologic conditions. We hypothesize that these dynamical features of the healthy human heartbeat have an endogenous circadian rhythm that brings the features closer to those observed under pathologic conditions at the endogenous circadian phase corresponding to approximately 10 a.m. We investigate heartbeat dynamics in healthy subjects recorded throughout a 10-day protocol wherein the sleep/wake and behavior cycles are desynchronized from the endogenous circadian cycle, enabling assessment of circadian factors while controlling for behavior-related factors. We demonstrate that the scaling exponent characterizing temporal correlations in heartbeat dynamics does exhibit a significant circadian rhythm (with a sharp peak at the circadian phase corresponding to approximately 10 a.m.), which is independent from scheduled behaviors and mean heart rate. Cardiac dynamics under pathologic conditions such as congestive heart failure also are associated with a larger value of the scaling exponent of the interbeat interval. Thus, the sharp peak in the scaling exponent at the circadian phase coinciding with the period of highest cardiac vulnerability observed in epidemiological studies suggests that endogenous circadian-mediated influences on cardiac control may be involved in the day/night pattern of adverse cardiac events in vulnerable individuals.

Unheralded sudden cardiac death: do autonomic tone and thrombosis interact as key factors in aetiology?

Unheralded sudden cardiac death is a personal and family tragedy that continues to elude research-based progress on aetiology or prevention. Instinctive links between autonomic imbalance, sympathetic activation and serious arrhythmia are longstanding and backed by many observational reports. However the role of the more familiar mechanisms of coronary occlusion and thrombus formation are underplayed. Sympathetic overactivity may also mediate sudden death through precipitation of vasospasm; platelet activation and inhibition of endogenous fibrinolysis as well as the propagation of arrhythmia. The integration of autonomic, thrombotic and vascular tone may be the key to better understanding of the individual process of unheralded sudden cardiac death. In this review we analyse the evidence for this hypothesis.

Smokers lack morning increase in platelet sensitivity to nitric oxide

This study investigated whether a circadian variation is present in the sensitivity of platelets to nitric oxide (NO) and, if so, if long-term smoking modifies it. Blood samples were taken at 0:00, 6:00, 9:00, 12:00, and 18:00 from 14 nonsmokers and 10 smokers. Dose-response curves for platelet aggregation by collagen were constructed in both the presence and absence of 1.0 micro M of NOR-3, a NO donor. The antiaggregation properties of NOR-3 were quantified by the half maximal concentration (EC50) ratio in the presence of NOR-3 to that in its absence. Platelet aggregation showed a monophasic circadian rhythm, with the lowest levels at 6:00 and the highest at 18:00 in both groups. However, there was a significant (p < 0.01) upward shifting of platelet aggregation in the smokers. A circadian variation in sensitivity to NOR-3 also was demonstrated in the nonsmokers. The sensitivity was lowest at 6:00 (1.68 +/- 0.19), increased significantly at 9:00 (2.58 +/- 0.26; p < 0.01), and remained high at 12:00 (2.47 +/- 0.21; p < 0.05). In smokers, however, a circadian variation in platelet sensitivity to NOR-3 was not found. Furthermore, the sensitivity was significantly lower at 9:00 and 12:00 in smokers (1.94 +/- 0.26 and 1.76 +/- 0.13, respectively; p < 0.05 for both) than in nonsmokers. Thus, long-term smoking impairs the normal morning increase in platelet sensitivity to NO, making platelets in smokers more thrombogenic during the hazardous hours.

Modulation of beta-adrenergic receptor subtype activities in perioperative medicine: mechanisms and sites of action

This review focuses on the mechanisms and sites of action underlying beta-adrenergic antagonism in perioperative medicine. A large body of knowledge has recently emerged from basic and clinical research concerning the mechanisms of the life-saving effects of beta-adrenergic antagonists (beta-AAs) in high-risk cardiac patients. This article re-emphasizes the mechanisms underlying beta-adrenergic antagonism and also illuminates novel rationales behind the use of perioperative beta-AAs from a biological point of view. Particularly, it delineates new concepts of beta-adrenergic signal transduction emerging from transgenic animal models. The role of the different characteristics of various beta-AAs is discussed, and evidence will be presented for the selection of one specific agent over another on the basis of individual drug profiles in defined clinical situations. The salutary effects of beta-AAs on the cardiovascular system will be described at the cellular and molecular levels. Beta-AAs exhibit many effects beyond a reduction in heart rate, which are less known by perioperative physicians but equally desirable in the perioperative care of high-risk cardiac patients. These include effects on core components of an anaesthetic regimen, such as analgesia, hypnosis, and memory function. Despite overwhelming evidence of benefit, beta-AAs are currently under-utilized in the perioperative period because of concerns of potential adverse effects and toxicity. The effects of acute administration of beta-AAs on cardiac function in the compromised patient and strategies to counteract potential adverse effects will be discussed in detail. This may help to overcome barriers to the initiation of perioperative treatment with beta-AAs in a larger number of high-risk cardiac patients undergoing surgery.

Circadian variation of the onset of acute myocardial infarction in the Osaka area, 1998-1999: characterization of morning and nighttime peaks

The onset of acute myocardial infarction (AMI) shows characteristic circadian variations; that is, a definite morning peak related to biologic rhythms and a vague nighttime peak related to socioeconomic factors. The recent economic recession in Japan may change the circadian variation, especially the nighttime peak. This study evaluated the recent circadian variation of AMI in Osaka and specified the patient subgroups showing either a morning or nighttime peak predominantly. Of 1,609 consecutive patients with AMI registered from April 1998 to January 2000, 1,252 whose onset of AMI was definitely identified were studied. The day was divided into six 4-h periods with a morning peak between 08.01 h and 12.00h, and nighttime peak between 20.01 h and 24.00h. When subgroup analysis was performed, female patients aged 65 years or more showed a morning peak alone and male patients aged less than 65 years with an occupation and the habits of cigarette smoking and alcohol intake showed a nighttime peak alone. Thus, in Osaka nighttime socioeconomic factors may currently be more potent triggers of AMI than the morning surges in younger male workers who smoke and drink.

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.

Silent ischaemia and hypertension

For many years now, silent ischaemia has been recognized as a distinct clinical entity, and its relevance in different patient groups has been established. However, a number of basic questions have not been answered. In explaining the pathophysiology of silent ischaemia, factors affecting both the demand and the supply side are now being recognized. With the exception of certain well-defined groups, it is not clear why some patients are mostly symptomatic, while other patients are predominantly asymptomatic. There appear to be many factors influencing the ischaemic pain threshold. Studies investigating the prevalence of silent ischaemia show a remarkably high prevalence of silent ischaemia in different patient groups. Patients with hypertension but without coronary artery disease form a specific and vulnerable high-risk population that is particularly prone to silent ischaemia. Since changes at the macrovascular level are not responsible, various factors negatively influencing either cardiac supply or demand have been investigated. A reduced coronary reserve is central in explaining the increased prevalence of silent ischaemia in hypertensives. Left ventricular hypertrophy renders meaningful detection of ST segment changes difficult, but a possible solution dealing with this problem is offered by applying more stringent criteria in terms of minimal ST depression in the definition of ischaemia. The treatment of silent ischaemia is largely the same as for angina pectoris, but whether therapy should be directed at elimination of all ischaemic episodes or only of symptomatic episodes depends on further prospective work addressing this question.

Application of noninvasive and invasive tests for risk assessment in patients with ventricular arrhythmias

Sudden cardiac death remains a major public health problem in western society. Because most patients who experience cardiac arrest are not successfully resuscitated, primary prevention of sudden death remains an important challenge. A number of noninvasive risk stratification techniques have been suggested as providing useful information in patients with underlying structural heart defects. Unfortunately, the positive predictive value of most of these techniques has been limited. Left ventricular ejection fraction, the presence of nonsustained ventricular tachycardia on Holter monitoring, and inducible sustained ventricular tachycardia at electrophysiologic testing in patients with coronary artery disease remain the best established prognostic test. However, with the exception of two ICD studies using the combination of these markers, prospective studies have not yet completely validated the use of these and other prognostic markers. Further understanding of the pathophysiology of ventricular fibrillation and other risk stratification techniques will be necessary before a clear algorithm can be developed for application to patients at risk for sudden death.

European survey on circadian variation of angina pectoris (ESCVA): design and preliminary results

A circadian variation has been observed for acute coronary syndromes (myocardial infarction, sudden cardiac death, angina pectoris) with a peak during the morning and a trough during the night. The previous reports, however, were based primarily on selected patients in clinical studies. The present study has been designed to determine the timing of attacks of angina pectoris in ambulatory patients, the association of wake time and possible external triggers with angina attacks, and the influence of cardiac medication. The European Survey on Circadian Variation of Angina Pectoris is a multicenter international cross-sectional survey of outpatients treated in general medical practice of seven European countries. Inclusion criteria are stable angina pectoris for at least 3 months, average frequency of two or more attacks per week, and treatment with on-demand nitrates. Standardised self-administered questionnaires are provided to all consecutive patients and their physicians. From January to July 1998, 1087 patients (61% male, 64 +/- 9 years; 39% female, 67 +/- 10 years) were enrolled in 196 centers. A total of 3453 angina pectoris attacks were reported, on average 3.2 per patient per week (range 0-48). The occurrence of angina pectoris attacks demonstrates a significant circadian variation (p < 0.001) with a primary morning peak from 9:00 to 12:00 (relative risk 3.0 compared with other times of day) and a secondary afternoon peak from 15:00 to 18:00. Of all attacks, 50% occured within 6 h after awakening. Seventy-four percent of all patients reported possible external triggers of angina such as physical activity or anger. The present multicenter survey in general medical practice demonstrates a marked wake time related circadian variation in angina pectoris attacks. To improve preventive strategies, therefore, type, dosage and particularly timing of cardiac medication appear of importance, as may be behavior modification approaches.

Effect of systemic alpha-2 adrenergic blockade on the morning increase in platelet aggregation in normal subjects

To assess whether activation of platelets by catecholamines contributes to the increase in platelet aggregation associated with either the assumption of upright posture or exercise, we studied the effect of oral yohimbine on these phenomena. Whole blood platelet aggregation and plasma catecholamine levels were measured before and after standing and at peak exercise in untreated normal subjects and after oral yohimbine. Neurochemical indexes indicated systemic alpha2-receptor blockade by yohimbine. Yohimbine reduced the orthostatic increase in platelet aggregation response by 63+/-11%, but exercise-induced increase in aggregation was unaffected. Thus, alpha2-adrenergic blockade attenuates the orthostatic increase in platelet aggregation. Agents designed to inhibit the morning surge in catecholamine levels or block platelet alpha2 adrenoceptors may reduce the risk of thrombotic vascular events in atherosclerosis.

High thoracic epidural anesthesia, but not clonidine, attenuates the perioperative stress response via sympatholysis and reduces the release of troponin T in patients undergoing coronary artery bypass grafting

In this prospective study, we evaluated whether high thoracic epidural anesthesia (TEA) or i.v. clonidine, in addition to general anesthesia, affects the cardiopulmonary bypass- and surgery-associated stress response and incidence of myocardial ischemia by their sympatholytic properties. Seventy patients scheduled for elective coronary artery bypass graft (CABG) received general anesthesia with sufentanil and propofol. TEA was randomly induced before general anesthesia and continued during the study period in 25 (anesthetized dermatomes C6-T10). Another 24 patients received i.v. clonidine as a bolus of 4 microg/kg before the induction of general anesthesia. Clonidine was then infused at a rate of 1 microg x kg(-1) x h(-1) during surgery and at 0.2-0.5 microg x kg(-1) x h(-1) postoperatively. The remaining 21 patients underwent general anesthesia as performed routinely (control). Hemodynamics, plasma epinephrine and norepinephrine, cortisol, the myocardial-specific contractile protein troponin T, and other cardiac enzymes were measured pre- and postoperatively. During the preoperative night and a follow-up of 48 h after surgery, five-lead electrocardiogram monitoring was used for ischemia detection. Both TEA and clonidine reduced the postoperative heart rate compared with the control group without jeopardizing cardiac output or perfusion pressure. Plasma epinephrine increased perioperatively in all groups but was significantly lower in the TEA group. Neither TEA nor clonidine affected the increase in plasma cortisol. The release of troponin T was attenuated by TEA. New ST elevations > or = 0.2 mV or new ST depression > or = 0.1 mV occurred in > 70% of the control patients but only in 40% of the clonidine group and in 50% of the TEA group. We conclude that TEA (but not i.v. clonidine) combined with general anesthesia for CABG demonstrates a beneficial effect on the perioperative stress response and postoperative myocardial ischemia.

IMPLICATIONS

Thoracic epidural anesthesia combined with general anesthesia attenuates the myocardial sympathetic response to cardiopulmonary bypass and cardiac surgery. This is associated with decreased myocardial ischemia as determined by less release of troponin T. These findings may have an impact on the anesthetic management for coronary artery bypass grafting.

Circadian variations of QTc dispersion: is it a clue to morning increase of sudden cardiac death?

BACKGROUND

Several studies related to cardiac events including sudden death have shown a peak incidence in the early morning hours. It has also been known that acute ischemia is a potent stimulus to increased dispersion of repolarization and development of malignant arrhythmias.

HYPOTHESIS

The purpose of the present study was to investigate diurnal variations of corrected QT dispersion (QTcD) in patients with coronary artery disease (CAD) (Group 1) compared with controls with normal coronary angiograms (Group 2).

METHODS

We investigated a total of 110 patients who had been referred for coronary angiography, of whom 62 (42 men, 20 women; age 55 +/- 7 years) had double- or triple-vessel disease, and of whom 48 (31 men, 17 women; age 54 +/- 9 years) had normal coronary angiograms. QTcD measurements were calculated from a 12-lead resting electrocardiogram (ECG) during sinus rhythm. These ECGs were obtained for each patient in the morning, at noon, in the evening, and at night on the day after performance of coronary angiography. QTcD was significantly greater in patients with abnormal coronary angiograms (Group 1) than in patients with angiographically documented normal coronary arteries (Group 2). This difference appeared to be more prominent in the morning hours (p < 0.001) than at other times. QTcD in the evening and night hours was not statistically different (p > 0.05) between both groups. We also compared intragroup QTcD values: QTcD values were significantly increased in the morning hours and were more prominent in Group 1 than in Group 2.

CONCLUSIONS

Our data suggest that QTcD has a circadian variation with an increase in the morning hours, especially in patients with coronary artery disease. This finding was thought to be an explanation for the role played by sympathetic nervous system in the occurrence of acute cardiac events and sudden death during these hours.

[Postoperative locoregional analgesia in the adult: epidural and peripheral techniques. Indications, adverse effects and monitoring]

Regional analgesia is a very effective way to treat postoperative pain. Lumbar and thoracic epidural analgesia are well adapted to major abdominal and thoracic surgery. Nevertheless, respiratory side effects induced by opioids are potentially severe and an adequate monitoring is essential. In orthopaedic surgery, perineural blocks are the best technique to manage postoperative pain and perineural catheters may be used. The importance of intra-articular analgesia, simple and safe, is not fully understood. The association of a local anaesthetic inducing a minor motor block and a strong sensitive block (bupivacaine, ropivacaine), with an opioid seems to be the best pharmacologic choice regarding quality of analgesia and safety. Benefits of postoperative regional analgesia on mortality and morbidity are not demonstrated. Medical and nursing staff and specialized units should improve quality of postoperative regional analgesia as well. General guidelines for the practice of regional anaesthesia must be closely followed.

Comparison between metoprolol orally osmotic once daily and metoprolol two or three times daily in suppressing exercise-induced and daily myocardial ischemia

Metoprolol is a widely used anti-ischemic drug with a relatively short half-life. To improve patient' compliance and to provide 24-hour coverage, its once daily ORally OSmotic (OROS) formulation was developed. In this multicenter double-blind study, the anti-ischemic effects of metoprolol OROS given once daily at doses of 190 and 285 mg were compared to the regular metoprolol formulation of 100 mg 2 or 3 times daily. Sixty-five patients with stable coronary artery disease, positive exercise tests, and ischemic episodes during daily activity as recorded by ambulatory electrocardiographic monitoring (AEM) were included. In the OROS group, 23 patients completed all 3 treatment periods. In these patients, the number of myocardial ischemic episodes decreased from 239 on placebo to 128 during the 190 mg/day dose (p < 0.0001) and to 86 during the 285 mg/day treatment period (p < 0.0001). In the metoprolol group, there were 204 episodes at baseline and 142 and 140 during the 100 mg 2 or 3 times daily treatment periods (p < 0.0001 for both). During exercise testing, time to 1-mm ST depression increased significantly in the OROS group from 6.3 minutes at baseline to 7.1 and 9.6 minutes during 190- and 285-mg treatment periods. In the metoprolol group, it increased from 5.8 to 7.2 and 8.2 minutes, respectively. Both formulations of metoprolol were well tolerated. The OROS formulation was highly effective in suppressing daily and exercise-induced ischemia and exerted its effect throughout the 24-hour period.

Mechanisms underlying the morning increase in platelet aggregation: a flow cytometry study

OBJECTIVES

Mechanisms underlying the morning increase in platelet aggregation produced by arising and assuming the upright posture were studied by examining 1) the expression on the platelet surface of activation-dependent markers; 2) platelet aggregation in whole blood; and 3) hematologic factors likely to influence aggregation.

BACKGROUND

The morning increase in thrombotic cardiovascular events has been attributed, in part, to the morning surge in platelet aggregability, but its mechanisms are poorly understood.

METHODS

Expression of seven platelet surface antigens (including P-selectin, activated GPIIb,IIIa and GPIb-IX), whole-blood platelet aggregation, platelet count and hematocrit were measured before and after arising in 17 normal volunteers. The fibrinolytic variables, tissue-type plasminogen activator, plasminogen activator inhibitor 1 and catecholamine levels were also measured.

RESULTS

On arising and standing, platelet aggregation increased by 71% (p < 0.01) and 27% (p < 0.03) in response to collagen and adenosine diphosphate, respectively. However, there was no change in any of the activation-dependent platelet surface markers. Whole-blood platelet count and hematocrit increased by 15% and 7% (both p < 0.0001), respectively. Norepinephrine and epinephrine levels increased by 189% (p < 0.0001) and 130% (p < 0.01), respectively. Tissue-type plasminogen activator antigen increased (31%, p < 0.01), but there was no significant increase in plasminogen activator inhibitor 1, suggesting an overall increase in fibrinolysis on standing. Prothrombin fragment 1.2 increased by 28% (p < 0.02), indicating a small increase in thrombin generation. The increases in hematocrit and platelet count that occurred on standing were carefully mimicked in vitro and resulted in a 115% (p < 0.05) increase in platelet aggregation in response to adenosine diphosphate.

CONCLUSIONS

These data demonstrate that the morning increase in platelet aggregation is not accompanied by expression of activation-dependent platelet surface receptors and suggest that the increase in whole-blood aggregation may be primarily due to the increases in catecholamine levels, platelet count and hemoconcentration.

Relation of circadian ventricular ectopic activity to cardiac mortality. CAST Investigators

The relation between the circadian occurrence of ventricular premature depolarizations (VPD) and sudden arrhythmic death was examined in a subset of patients entered into the Cardiac Arrhythmia Suppression Trial (CAST). Ambulatory electrocardiographic recordings with hourly measurement of VPD frequency were available in 357 patients. Forty percent of the patients (142 of 357) demonstrated circadian variation in VPD frequency between 6:00 A.M. and 9:59 A.M. that was significantly higher (p < 0.05) than what could randomly be expected from an overall 24-hour average for that patient. The only baseline characteristics in patients with circadian VPDs were age (p < 0.04), history of cardiac arrest (p < 0.01), presence of higher frequency of VPDs (p < 0.002), more frequent episodes of ventricular tachycardia (p < 0.04), and more frequent episodes of slow runs (p < 0.04). There was no difference in mortality in patients with or without circadian VPD variation; drug treatment did not effect mortality. These data indicate that the presence of circadian VPDs is not a predictor of sudden arrhythmic death in patients with a high frequency of VPDs.

Anti-ischemic intervention as prognosis improvement in patients with coronary artery disease, with special focus on verapamil

Angina pectoris is a significant risk predictor in patients with atherosclerotic heart disease. The major complications are myocardial infarction, heart failure, and arrhythmias. Plaque rupture turns stable angina pectoris into acute coronary syndrome by provoking platelet aggregation and thereby thrombus formation. Verapamil significantly inhibits platelet aggregation and thrombus formation, which may be one of several reasons for the protective effect of verapamil on reinfarction in patients recovering from myocardial infarction. Ischemia may lead to left ventricular dilation and diastolic dysfunction, and thereby heart failure. In postinfarction patients intervention with verapamil significantly reduced the use of diuretics compared with placebo, indicating that anti-ischemic intervention may prevent heart failure. Ventricular arrhythmias are significantly associated with arrhythmic as well as non-arrhythmic death. The lack of preferential association of ventricular arrhythmias with arrhythmic death rather than nonarrhythmic death may imply that arrhythmias are provoked by ischemia. Antiarrhythmic intervention in postinfarction patients significantly increases death and arrhythmic events compared with placebo, especially in patients with residual ischemia. This may be due to a significant slowing of conduction during ischemia in patients treated with antiarrhythmic agents. In animal studies anti-ischemic agents prevent or suppress ventricular arrhythmias during ischemia, whereas traditional antiarrhythmic drugs have no effect or even worsen the arrhythmias, especially during episodes with elevated sympathetic activity. Verapamil significantly reduces plasma norepinephrine levels and the norepinephrine release during ischemia, whereby ventricular arrhythmias may be prevented. Also, supraventricular arrhythmias are significantly associated with myocardial ischemia and are prevented by verapamil. In patients with atherosclerotic heart diseases, angina pectoris is a significant risk predictor, but anti-ischemic intervention should be considered even in patients in whom the major problem is heart failure or arrhythmias.

Circadian patterns and triggers of sudden cardiac death

Sudden cardiac death and other acute cardiovascular events have been demonstrated to occur in certain temporal patterns. The study of these patterns may yield important clues to the pathophysiology of the disease process. Most studies of the timing of onset of sudden cardiac death have revealed a prominent midmorning peak, thought to be related to a surge in catecholamines associated with arising and assuming the upright posture, that is blunted or eliminated by beta blockers. In addition, some studies have also shown a secondary peak in late afternoon or early evening of uncertain cause. The development of third-generation implantable cardioverter defibrillators with memory capabilities offers a unique opportunity to accurately define event chronology.

Hemostatic factors as triggers of cardiovascular events

A growing body of evidence supports a role for hemostatic factors in triggering cardiovascular events. Fibrinogen has been identified as an independent cardiovascular risk factor that is as powerful a predictor as cholesterol. Factor VII, fibrinolytic potential, von Willebrand's factor, and platelet reactivity also have been linked to increased incidence of cardiovascular disease. Further characterization of these factors may lead to improved risk assessment and the development of new therapies for prevention.

Hemodynamic changes as triggers of cardiovascular events

Although a large number of clinical studies during the past decade have documented that myocardial ischemia, acute myocardial infarction, and sudden cardiac death have definite circadian patterns, recently published work suggests that it is not necessarily a specific time of the day but the sleep/wake cycle and postural changes as well as the balance between triggers and protective factors that determine the onset of cardiovascular events. A clear understanding of the pathophysiologic processes responsible for ischemic events and the specific roles played by various triggers would be helpful in better defining the therapeutic strategies designed for the prevention and treatment of acute cardiac events. Because changes in hemodynamic parameters are of paramount importance in initiating an ischemic event, it is critical to review their role and relationship in the pathogenesis of acute coronary events.

Treatment of silent ischemia in unstable angina: a randomized comparison of sustained-release verapamil versus metoprolol

Silent ischemia is a frequent finding in patients with unstable angina and portends a poor prognosis. We compared the efficacy of sustained-release (SR) verapamil and metoprolol in reducing silent ischemia in patients with unstable angina and assessed whether detection of silent ischemia was related to unfavorable outcomes in the contemporary setting of concurrent therapy with heparin and aspirin. Holter monitoring (leads a VF, V2, V5) for the first 72 h was used to assess the frequency and duration of ST-shift episodes. There were 37 patients in the verapamil-SR group and 40 patients in the metoprolol group, with both groups having similar baseline characteristics. There were more episodes of angina in the verampamil-SR group (29 vs. 12, p = 0.05). There was no difference between the two groups in the frequency (51 vs. 49 episodes, p = 0.9) or duration (23 +/- 48 vs. 18 +/- 50 min, p = 0.6) of ST-shift episodes. There were 20 unfavorable in-hospital outcomes distributed equally between the two groups (p = 0.9). Patients with unfavorable outcomes had ST shift more often (50 vs. 28%, p = 0.07) and for a longer duration (40 +/- 69 vs. 13 +/- 38 min, p = 0.03). Patients with ST shift > or = 60 min had a 60% probability of unfavorable outcome compared with 33% for ST shift of 1-59 min duration and 20% for no ST shift (p = 0.04). We conclude that metoprolol appears to reduce symptoms better than verapamil-SR, but no difference in silent ischemia or unfavorable outcomes was seen. Silent ischemia remains a common occurrence in these patients despite heparin and aspirin therapy and its detection continues to have prognostic value.

ST-segment depression on ambulatory electrocardiography in the early in-hospital period after acute myocardial infarction predicts early and late mortality: a short-term and a 3-year follow-up study

A surveillance study was conducted to determine the in-hospital and long-term prognostic value of ST-segment depression assessed by ambulatory electrocardiographic monitoring (AEM) during the early in-hospital period after acute myocardial infarction (AMI). ST-segment depression (STD) was determined by computer analysis of 24-h ECG tapes as a horizontal or downsloping change in ST level by > 0.1 mV from the reference base line. The ST level was measured 80 ms after the J point of all normally conducted complexes for > or = 1 min. All computer-detected ST events were verified by one trained reader. Tapes corresponding to 74 patients were analyzed. In addition, 23 tapes corresponding to age- and gender-matched controls were also analyzed. Patients were divided into two groups: 22 patients (30%) showed STD (Group A), and 52 patients (70%) had no episode of STD (Group B). Among controls, 1 person (4%) showed STD. During the early follow-up period (14 +/- 11 days after hospital admission), cardiac events occurred in 11 patients [7 (32%) in Group A and 4(8%) in Group B, p < 0.01], including 6 cardiac death [5 (23%) in Group A and 1 (2%) in Group B, p < 0.01], 3 acute coronary artery bypass surgeries [2 (9%) in Group A and 1 (2%) in Group B, p = NS], and 2 nonfatal myocardial infractions (both in Group A, p = NS). During a mean follow-up period of 3 years (36 +/- 15 months), 18 patients died [10 (45%) in Group A and 8 (15%) in Group B, p = 0.01]. Eleven deaths were sudden [7 (32%) in Group A and 4 (8%) in Group B, p < 0.01]. Eighteen AMI occurred [11 (50%) in Group A and 7 (13%) in Group B, p < 0.005]. Twenty patients underwent revascularization procedures [7 (32%) in Group A and 13 (25%) in Group B, p = NS].(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment and significance of ST-segment changes detected by ambulatory electrocardiography after acute myocardial infarction

This study assessed the prognostic value of ST-segment changes detected by ambulatory electrocardiographic monitoring during the early in-hospital period after acute myocardial infarction. New methods for defining the ST-segment reference level and for measuring ST-segment elevation were used. ST-segment depression was defined as a change in ST level by > or = 0.1 mV 80 ms after the J point, elapsing > or = 1 minute. ST-segment elevation was defined as a deviation by > or = 0.15 mV, elapsing > or = 1 minute, and measured at the J point. An interval of > or = 2 minutes was required before another discrete episode was counted. Four ST-segment reference levels were automatically calculated: (1) "isoelectric," (2) "nearest to normal," (3) "24-hour median," and (4) "first-hour median." During a mean follow-up period of 3 years (mean 36 +/- 15 months), 47 cardiac events occurred in 38 patients: 18 deaths, 9 nonfatal reinfarctions, and 20 revascularization procedures. More deaths occurred in patients with than without ST elevation-24-hour median (22% vs 5%, p = 0.03), and in patients with than without ST depression-isoelectric (61% vs 32%, p = 0.02), and in patients with than without ST-depression-24-hour median (61% vs 23%, p = 0.003). "All cardiac events" (deaths, infarctions, or revascularization procedures) occurred more often in patients with than without ST depression-isoelectric (55% vs 22%, p = 0.003), and in patients with than without ST-depression-24-hour median (47% vs 17%, p = 0.004). Sensitivity, specificity, and accuracy of ST depression/elevation-24-hour median to assess mortality were 78%, 71%, and 73%, respectively.

Postoperative myocardial ischemia: etiology of cardiac morbidity or manifestation of underlying disease?

STUDY OBJECTIVE

To determine the relationship between postoperative ST segment changes and clinically apparent cardiac morbidity in noncardiac surgery patients.

DESIGN

Prospective, cohort study.

SETTING

General inpatient and intensive care units at a tertiary care hospital.

PATIENTS

145 high-risk noncardiac surgery patients.

MEASUREMENTS AND MAIN RESULTS

Patients were monitored for ST segment changes using ambulatory electrocardiographic (ECG) recorders from the end of the surgical period for up to the third postoperative day. Patients were evaluated for a clinically apparent cardiac event (cardiac death or myocardial infarction) by daily 12-lead ECGs, and CK-MB isoenzymes, as clinically indicated. Nine patients sustained a clinically apparent cardiac event, 7 of whom had a cardiac event during the period in which they were monitored by ambulatory ECG. All 7 patients who sustained a cardiac event during the monitoring period had at least one episode of myocardial ischemia, which persisted for a minimum of 30 minutes either prior to or at the same time of the event, with no morbidity occurring in the group of patients who had only short durations of myocardial ischemia. Three of the patients with events had continuous ST segment changes, while the other patients had transient ST segment changes.

CONCLUSIONS

These observations suggest that clinically apparent cardiac events are associated with prolonged ST segment changes detected on ambulatory ECG recorders. The cardiac ischemia leading to prolonged postoperative ST segment changes may itself result in cardiac morbidity, or it may be a reflection of underlying pathophysiology.

Effect of amlodipine, atenolol and their combination on myocardial ischemia during treadmill exercise and ambulatory monitoring. Canadian Amlodipine/Atenolol in Silent Ischemia Study (CASIS) Investigators

OBJECTIVES

This study compared the effects of amlodipine, atenolol and their combination on ischemia during treadmill testing and 48-h ambulatory monitoring.

BACKGROUND

It is not known whether anti-ischemic drugs exert similar effects on ischemia during ambulatory monitoring and exercise treadmill testing.

METHODS

Patients with stable coronary artery disease and ischemia during treadmill testing and ambulatory monitoring were randomized to receive amlodipine (n = 51) or atenolol (n = 49). Each group underwent a counterbalanced, crossover evaluation of single drug and placebo, followed by evaluation of the combination.

RESULTS

Amlodipine and the combination prolonged exercise time to 0.1-mV ST segment depression by 29% and 34%, respectively (p < 0.001) versus 3% for atenolol (p = NS). During ambulatory monitoring, the frequency of ischemic episodes decreased by 28% with amlodipine (p = 0.083 [NS]), by 57% with atenolol (p < 0.001) and by 72% with the combination (p < 0.05 vs. both single drugs; p < 0.001 vs. placebo). Suppression of ischemia during exercise testing and ambulatory monitoring was similar in patients with and without exercise-induced angina. Exercise time to angina improved by 29% with amlodipine (p < 0.01), by 16% with atenolol (p < 0.05) and by 39% with the combination (p < 0.005 vs. placebo, atenolol and amlodipine). In patients with angina, total exercise time improved by 16% with amlodipine (p < 0.001), by 4% with atenolol (p = NS) and by 19% with the combination (p < 0.05 vs. placebo and either single drug). In those patients without angina, no therapy significantly improved total exercise time.

CONCLUSIONS

Ischemia during treadmill testing was more effectively suppressed by amlodipine, whereas ischemia during ambulatory monitoring was more effectively suppressed by atenolol. The combination was more effective than either single drug in both settings.

Daily life cardiac ischaemia. Should it be treated?

Daily life cardiac ischaemia is defined as reversible myocardial cellular hypoxia that occurs during activities of daily living, without artificial provocation. Most of these daily life ischaemic episodes are not associated with symptoms. However, it is not practical to distinguish silent versus symptomatic daily life ischaemia as both are associated with haemodynamic abnormalities and future adverse outcomes. Daily life cardiac ischaemia is best detected using ambulatory electrocardiogram (ECG) monitoring; however, there are other diagnostic tools (e.g. exercise treadmill) that can be used. Once detected, the optimal therapy for daily life myocardial ischaemia has yet to be identified. However, it does appear that usual antianginal medications including nitrates, beta-blockers, calcium antagonists and antiplatelet drugs are effective in reducing the incidence and severity of daily life myocardial ischaemia. Medical therapy and revascularisation should be utilised to obliterate all episodes of daily life cardiac ischaemia to prevent future cardiac events. Moreover, the efficacy of the chosen therapeutic regimen for each patient should be documented with follow-up objective testing. The diagnosis and management of daily life myocardial ischaemia is continually evolving. Future research as well as economic considerations will shape future management strategies.

Intermittent transdermal nitrates do not improve ischemia in patients taking beta-blockers or calcium antagonists: potential role of rebound ischemia during the nitrate-free period

OBJECTIVES

This study was conducted to determine whether rebound ischemia occurs during nitrate-free periods with intermittent cutaneous nitroglycerin therapy in patients with angina pectoris who are receiving background antianginal therapy.

BACKGROUND

Rebound angina has been suggested to be a complication of the nitrate-free period with long-term cutaneous nitroglycerin therapy given intermittently to prevent tolerance.

METHODS

Fifty-two patients with stable effort angina taking either a beta-adrenergic blocking agent (n = 25) or diltiazem (n = 22) or their combination (n = 5) completed a randomized, double-blind, placebo-controlled crossover study of cutaneous nitroglycerin patches (50 mg). Active or placebo patches were worn for 1 week, applied at 8 AM and removed at 10 PM to provide a 10-h daily nitrate-free (or placebo-free) period. During the last 48 h of each study phase, a Holter monitor was used to detect ischemia.

RESULTS

Only 31 patients experienced ischemia during either phase of the study (23 during the patch-off period). A total of 463 ischemic episodes were recorded: 246 during placebo and 217 during nitroglycerin (p = 0.8, for per patient comparison). The majority (88%) of ischemic episodes were silent. Mean (+/- SEM) duration of ischemia during the total 48-h period was similar during active and placebo phases (35.5 +/- 15.0 min/24 h for active therapy vs. 29.7 +/- 9.8 for placebo, p = 0.8). This was due to an increase in duration of ischemia with active therapy during the patch-off period (46.9 +/- 17.9 min/24 h for active therapy vs. 22.5 +/- 9.2 for placebo, p = 0.07) and a decrease during the patch-on period (27.5 +/- 14.0 min/24 h for active therapy vs. 34.5 +/- 11.0 min/24 h for placebo, p = 0.16). The pattern of diurnal distribution of ischemic episodes differed between active and placebo phases. During placebo there was a nadir in the incidence of ischemia in the overnight patch-off period, with a significantly lower incidence between midnight and 6 AM (25 episodes) compared with the mean number of episodes during the three other 6-h periods (73 episodes, p < 0.001). During the nitroglycerin patch-off period, there was a loss of this overnight nadir, with the same incidence of ischemia between midnight and 6 AM (53 episodes) as the mean number of episodes for the three other 6-h periods (54 episodes).

CONCLUSIONS

The majority of patients taking background antianginal therapy experienced no ischemia during the patch-off period. In the 44% of patients with ischemia during this period, there was a nonsignificant increase in the duration of ischemia with active therapy. Although this result was statistically inconclusive, the change in the distribution of diurnal ischemia offers suggestive evidence that rebound ischemia may be a problem with regard to intermittent cutaneous nitroglycerin.

Platelet aggregability in vivo is attenuated by verapamil but not by metoprolol in patients with stable angina pectoris

The effects of 1 month of treatment with either verapamil or metoprolol on several aspects of platelet function were studied at rest and during physical exercise or mental stress in patients with stable angina pectoris participating in the Angina Prognosis Study in Stockholm. Platelet aggregability was measured by filtragometry ex vivo, which reflects platelet aggregability in vivo and by Born aggregometry in vitro. Platelet secretion in vivo was assessed by measurements of beta-thromboglobulin in plasma. Verapamil reduced plasma norepinephrine levels (from 2.6 +/- 1.0 to 2.2 +/- 1.0 nmol/L; p < 0.01) and attenuated platelet aggregability at rest (filtragometry readings were prolonged from 219 to 295 seconds; p < 0.05, n = 46). Aggregability in platelet-rich plasma was not influenced. Metoprolol did not significantly affect filtragometry readings (n = 58) or aggregability in vitro (there was a tendency toward enhanced adenosine diphosphate sensitivity; p = 0.08). beta-thromboglobulin levels were low (approximately 25 ng/ml) and not influenced by either treatment. Physical exercise (bicycle ergometry) increased platelet aggregability in vivo both before and after drug treatment. Verapamil also attenuated platelet aggregability after exercise, whereas metoprolol had no such effect. Platelet function was not seriously altered by mental stress (Stroop's color word test) despite significant effects on hemodynamics and plasma catecholamines either before or after treatment with either drug. Thus, verapamil attenuates platelet aggregability in patients with stable angina pectoris, whereas metoprolol has no such effect.

Medical treatment to reduce total ischemic burden: total ischemic burden bisoprolol study (TIBBS), a multicenter trial comparing bisoprolol and nifedipine. The TIBBS Investigators

OBJECTIVES

We compared the effects of bisoprolol on transient myocardial ischemia with those of nifedipine in patients with chronic stable angina.

BACKGROUND

Both beta-adrenergic blocking agents and calcium antagonists reduce transient ischemic episodes, but comparisons of these agents have been made in only a few larger studies.

METHODS

The Total Ischemic Burden Bisoprolol Study (TIBBS) was a randomized double-blind controlled study with two parallel groups; 330 patients from 30 centers in seven European countries with stable angina pectoris, a positive exercise test and more than two transient ischemic episodes during 48 h of Holter monitoring (central evaluation) were included. Of these patients 161 were randomized to receive bisoprolol and 169 to receive nifedipine slow release. There were two treatment phases of 4 weeks each, with 48-h Holter monitoring after each phase. During phase 1, patients received either 10 mg of bisoprolol daily or 2 x 20 mg of nifedipine slow release. During phase 2, they received either 20 mg of bisoprolol daily or 2 x 40 mg of nifedipine slow release.

RESULTS

In phase 1 of the trial, 4 weeks of bisoprolol therapy (10 mg daily) reduced the mean [+/- SD] number of transient ischemic episodes from 8.1 +/- 0.6 to 3.2 +/- 0.4/48 h. Nifedipine (2 x 20 mg) reduced transient ischemic episodes from 8.3 +/- 0.5 to 5.9 +/- 0.4/48 h. Total duration of ischemia was reduced from 99.3 +/- 10.1 to 31.9 +/- 5.5 min/48 h with bisoprolol and from 101 +/- 9.1 to 72.6 +/- 8.1 min/48 h with nifedipine. Reductions were statistically significant for both drugs; the difference between bisoprolol and nifedipine was also significant (p < 0.0001). Bisoprolol reduced the heart rate at onset of episodes by 13.7 +/- 1.4 beats/min from a baseline value of 99.5 +/- 1.2 beats/min (p < 0.001). Heart rate was unchanged with nifedipine. Bisoprolol had significantly higher responder rates than nifedipine. Doubling of the dose in phase 2 of the trial had small additive effects. Only bisoprolol showed a marked circadian effect by reducing the morning peak of transient ischemic episodes (by 68% at peak time, 8:00 to 8:59 AM).

CONCLUSIONS

Both bisoprolol and nifedipine reduced the number and duration of transient ischemic episodes in patients with chronic stable angina. Bisoprolol was significantly more effective than nifedipine in both doses tested and reduced the morning peak of ischemic activity.

Use of exercise test parameters to predict presence and duration of ambulatory ischemia in patients with coronary artery disease

Myocardial ischemia is an indicator of adverse prognosis. In patients with stable angina and positive exercise tests, prolonged cumulative ischemia on ambulatory electrocardiographic monitoring identifies a high-risk group with severe coronary artery disease and poor survival. To determine whether features of the exercise test can accurately (1) predict the occurrence of ambulatory ischemia, and (2) classify patients into subgroups at varying levels of risk for ambulatory ischemia, we studied 48 patients with a history of angina and documented coronary disease who underwent the standard Bruce protocol and ambulatory monitoring. All patients had a positive exercise treadmill test, and 26 had ischemia on Holter monitoring (total of 2,922 minutes, 173 episodes, 94% with silent ischemia). The remaining 22 patients did not have ischemia. The exercise test parameters showing significant differences between the 2 groups were (1) time to > or = 1 mm ST-segment depression (p < 0.0003), (2) maximal ST-segment depression (p < 0.004), and (3) exercise capacity (p < 0.037). These data were used to develop a model for predicting the presence and the severity of ambulatory ischemia. Time to onset of > or = 1 mm ST-segment depression and maximal ST-segment depression on exercise treadmill testing can be used to determine the likelihood of mild (1 to 5 episodes or lasting < or = 60 minutes) or severe prolonged (> 5 episodes or lasting > 60 minutes) ambulatory ischemia. Patients with a very high or very low probability of ischemia on Holter monitoring can be identified by certain exercise test parameters and may not need to undergo monitoring.(ABSTRACT TRUNCATED AT 250 WORDS)

Heart rate variability before the occurrence of silent myocardial ischemia during ambulatory monitoring

Thirty-three ischemic episodes in 19 patients with stable coronary artery disease were studied to clarify changing autonomic nervous system activity during daily life before the occurrence of myocardial ischemia. Nonischemic points were studied for comparison of control data with ischemic episodes. These were defined as (1) patient showing no ischemic ST-T change while having the same heart rate with onset of ischemic episodes, and (2) presence within 1 to 2 hours before or after onset of ischemic episodes in the same patient. We analyzed heart rate (HR) variability during the 30-minute period before the onset and after the end of ischemic episodes during 24-hour monitoring. The period of 30 to 40 minutes before ischemia was regarded as the baseline, and HR variability was analyzed at 10-minute intervals before each ischemic episode and nonischemic point. HR variability was quantified on the band of 2 components: low frequency (0.04 to 0.15 Hz; LF) and high frequency (0.15 to 0.40 Hz; HF). Of the 33 episodes, 24 (73%) had a greater LF/HF value during the 30-minute period before ischemia than that before the nonischemic points. Distribution of the number of the 24 episodes demonstrated circadian rhythm with a peak from 8 to 10 A.M. HF power began to decrease from the last 10 minutes before ischemia, compared with baseline. A significant decrease in HF power with a background of greater value of LF/HF may explain the reduced ischemic threshold for ischemia during daily life.

Effects of nadolol on hemodynamic and hemostatic responses to potential mental and physical triggers of myocardial infarction in subjects with mild systemic hypertension

Although beta-adrenergic blocking agents are known to reduce the risk of myocardial infarction, the mechanism of this protective effect is not well understood. The recent demonstration that beta blockers selectively blunt the increased morning risk of myocardial infarction suggests that these agents block the pathophysiologic consequences of stressors concentrated in the morning. We determined the effect of nadolol on the hemodynamic and hemostatic responses to mental stress and isometric exertion (handgrip), 2 potential triggers of infarction. The study was conducted in 15 subjects with mild systemic hypertension, using a placebo-controlled, double-blind, crossover design. Nadolol reduced systolic pressure and heart rate after mental stress. Poststress systolic pressure was 139 +/- 4 mm Hg during therapy with nadolol versus 161 +/- 4 mm Hg during placebo administration (p < 0.05). Heart rate increased to 61 +/- 2 during nadolol therapy versus 89 +/- 5 beats/min during placebo therapy (p < 0.05). The systolic pressure increase was similar during therapy with nadolol and placebo (29 +/- 2 vs 33 +/- 2 beats/min, p = NS); however, heart rate increase was less during nadolol therapy (4 +/- 1 vs 12 +/- 4 vs beats/min, p < 0.01). The responses to handgrip and their modification during nadolol therapy were similar to those observed after mental stress. Neither platelet aggregability nor fibrinolytic potential was altered by nadolol. Thus, nadolol modified hemodynamic indexes without altering the hemostatic indexes measured. This hemodynamic effect may contribute to the decrease in morning cardiovascular events by beta-adrenergic blockers and their well-documented cardioprotective effect.

Epidural morphine reduces the risk of postoperative myocardial ischaemia in patients with cardiac risk factors

Perioperative myocardial ischaemia is a predictor of postoperative cardiac morbidity (PCM). Epidural anaesthesia and adequate perioperative analgesia have been shown to improve myocardial oxygen dynamics due to interruption of pain and sympathetic pathways. The aim of the present study was to compare the incidence of ischaemia after either general anaesthesia followed by parenteral analgesia with morphine or combined epidural/general anaesthesia followed by analgesia with epidural morphine. In a prospective observer-blinded analysis of the occurrence of ischaemia, 55 patients (epidural = 29/parenteral = 26) scheduled for elective surgery with defined risks for ischaemic cardiac disease were entered and followed for 24 hr after surgery with two-lead continuous Holter monitoring. Groups were similar with respect to age, weight, modified Goldman (Detsky) risk classification and the use of cardiac medications. Fewer patients receiving the epidural anaesthesia/analgesia had ischaemic episodes (17.2 vs 50.0%, P = 0.01), and tachyarrhythmias (20.7 vs 50.0%, P < 0.05). Epidural patients had a four-fold reduction of the relative risk for either event (P < 0.001). All ischaemic events were asymptomatic and unrecognized (silent). All major morbid events (n = 5) (MI, congestive heart failure and death) occurred in patients who had perioperative episodes of ischaemia. There were three distinct peaks in onset of ischaemia, at 1-4 hr, 9-12 hr and 22-24 hr postoperatively. One third of postoperative ischaemic events occurred within the first four hours after operation and lasted from 1 to 31 min. Forty-two percent of ischaemic episodes were associated with a heart rate > 100 bpm, or an increase of 20% over the baseline heart rate. We conclude that epidural anaesthesia/analgesia reduces but does not eliminate the risk of myocardial ischaemia and tachyarrhythmia. We were unable to determine any associated reduction in the risk of PCM.

Silent myocardial ischemia

The documentation of abnormalities related to myocardial ischemia, whether symptomatic or silent, is of central importance. Whenever this information is available, it should be used in the overall assessment of the patient at risk for adverse outcome. The level of concern for treatment of CAD should be based on the risk implications associated with the ischemia-related abnormalities detected during objective testing rather than on the presence or absence of pain. The exercise stress test is still the single most useful test to begin the evaluation of a patient with an analyzable ST segment. In persons suspected of having CAD, the detection of ischemic-type ST-segment depression, at a low workload (e.g., < 120 beats/min or < 6.5 METS) of > 2 mm magnitude or persisting for more than 6 min implies high risk for adverse outcome. Asymptomatic ischemia during everyday activities, detected by Holter monitoring, in the high-risk patient, most probably adds additional risk beyond the risk of an abnormal stress test alone. Left ventricular imaging by two-dimensional echocardiography, RNA, angiogram, vest, etc, showing an ejection fraction > or = 40%, reversible wall motion abnormalities in multiple regions and redistribution defects or a failure to increase ejection fraction during exercise even if the patient remains asymptomatic, also imply high risk. The presence of any of these abnormal findings, regardless of symptoms, should therefore prompt as high a degree of concern as with ischemia-related signals associated with pain. Thus any therapy chosen should be directed toward elimination of transient ischemia, not just relief of symptoms that may or may not be ischemia related. If this course is chosen, the efficacy of the therapeutic regimen and possible progression of CAD should be assessed with follow-up testing for ischemia. We believe that risk factor modification and aspirin should be considered for most, if not all, patients in whom ischemia, silent or symptomatic, is suspected or detected. If symptoms or ischemia suggesting low risk is present, anti-ischemic medical therapy may be considered, but follow-up is advised. If a high-risk ischemic signal, even without symptoms, is detected, medical therapy should be used to attempt to modify the signal. If the ischemic signal suggesting high risk persists despite medical therapy, revascularization should be considered. Until additional data from large clinical trials are available, this approach appears to have the greatest likelihood of modifying the adverse outcome of CAD.

Changing circadian variation of transient myocardial ischemia during the first year after a first acute myocardial infarction

In a consecutive series of 123 men (aged 55 +/- 8 years) with a recent first acute myocardial infarction (AMI), 24-hour ambulatory ST-segment monitoring was performed early after discharge (day 11 +/- 5), 6 months (day 185 +/- 6) and 1 year (day 368 +/- 8) after AMI. No difference in the prevalence of transient myocardial ischemia was found between the 3 recordings (17, 17 and 20%), and most ischemic episodes were silent (98, 100 and 97%). In the early postinfarction period, a peak of ischemic activity was demonstrated between 6 P.M. and midnight (40 of 93 episodes [43%]). Over time, the maximal occurrence of ischemia gradually advanced toward the morning hours with a peak activity between 6 A.M. and noon at 1-year follow-up (32 of 73 episodes [44%]). Significantly more patients (16 of 21 [76%]) had ischemia from 6 P.M. to midnight at discharge compared with the findings 1 year later (9 of 23 patients [39%]) (p < 0.03). An opposite trend was found regarding patients who exhibited ischemic episodes in the hours from 6 A.M. to noon: 10 of 21 patients (48%) early after discharge versus 17 of 23 patients (74%) at 1-year follow-up (p = not significant). Results from the 6-month recording displayed characteristics between the findings from discharge and 1-year ambulatory monitoring. The pathophysiologic processes underlying the observations from this study are unknown. The change in circadian periodicity could not be explained from differences in heart rate variation patterns or medical antianginal treatment among the 3 recordings.(ABSTRACT TRUNCATED AT 250 WORDS)