Mechanism of rest and nocturnal angina: observations during continuous hemodynamic and electrocardiographic monitoring

Unstable Angina Pectoris: An Interventional Approach to Management

The therapy of unstable angina has changed consider ably in the last 15 years. An improved understanding of the pathophysiology has led to many of the changes. Thrombus, platelet activation, progression of athero sclerosis, and coronary vasospasm all appear to have a role. Initial management in unstable angina should begin with aggressive medical therapy with nitrates, calcium antagonists, beta blockers, and aspirin. In patients who are refractory to aggressive medical management, early cardiac catheterization and coronary arteriography is in dicated. The literature appears to confirm that patients with unstable angina who are stabilized with aggressive medical therapy fare as well as those treated with emer gency bypass surgery. Percutaneous transluminal coro nary angioplasty (PTCA) is the treatment of choice in medically refractory unstable angina patients with single-vessel coronary disease.

New approaches include culprit lesion angioplasty, thrombolytic therapy, coronary sinus retroperfusion, and new catheter-based revascularization methods such as intracoronary stents, laser methods and atherectomy. Culprit lesion angioplasty involves angioplasty of only the angina-producing artery in patients with multivessel coronary disease. Early data suggest that this may be an effective short-term alternative to multivessel PTCA or bypass surgery. Recent data also suggest a beneficial role for thrombolytic therapy and synchronized coronary si nus retroperfusion with arterial blood in patients with unstable angina. New catheter-based approaches are in the early stages of development, and their eventual role in the treatment of coronary artery disease and unstable angina remains to be elucidated.

Acute Arterial Hypertension in Acute Pulmonary Edema: Mostly a Trigger or an Associated Phenomenon?

BACKGROUND

The role of acute arterial hypertension in acute pulmonary edema (APE) as an associated or triggering phenomenon has been poorly investigated and is relevant to patient management.

METHODS

This was a prospective observational study of clinical, electrocardiographic, and echocardiographic characteristics of patients with APE. Potential triggers, including acute coronary syndrome (ACS), rapid atrial fibrillation (AF) (≥ 120 bpm in AF), fever > 38°C or volume overload, isolated acute hypertension (systolic blood pressure ≥ 170 mm Hg), and unknown factors were investigated.

RESULTS

There were 742 patients, 578 with coronary artery disease (78%), 116 with valvular heart disease or cardiomyopathy (16%), and 47 without identifiable heart disease (6%). ACS was present in 482 (65%) patients (silent in 154 of them), AF was present in 76 (10%) patients, fever/volume overload was present in 62 (8%) patients, acute hypertension was present in 50 (7%) patients, and no apparent trigger was seen in 72 (10%) patients. Admission hypertension occurred in 260 patients (35%): 155 (60%) with ACS (silent in 49 [32%]), 36 (14%) with AF, 19 (7%) with fever/volume overload, and 59 (19%) as an isolated trigger. Similar results were obtained when analyzing patients using coronary angiography (467 patients [63%]). Acute hypertension was present more frequently in patients with severe hypoventilation (arterial Pco₂ > 60 mm Hg) than in those without (57% vs 29%; P < 0.001) and in those without moderate-severe mitral regurgitation than in those with (51% vs 30%; P < 0.001).

CONCLUSIONS

In patients with APE, with or without ACS, acute hypertension is often present but mainly as an associated/reactive phenomenon and seems favoured by severe hypoventilation. Silent myocardial ischemia/necrosis deserves systematic investigation because it is not rare that it may be the underlying cause of APE.

Extent of myocardial ischemia during coronary occlusion in single vessel disease. A comparison between patients with exercise-induced angina and patients with recurrent angina at rest

Patients with exercise angina >2 months (n:13) showed significantly lower SigmaST elevation during 120 s balloon coronary occlusion than those with =<2 months (n:7), or those with angina at rest <=2 days (n:8) but similar to patients with angina at rest >2 days (n:7). These results underscore the importance of the kind and duration of angina in limiting the extent of ischemia during coronary occlusion.

Comparison of clinical and angiographic features and longterm follow-up events between patients with variant angina and patients with ST elevation myocardial infarction

We investigated to what extent patients with variant angina and significant coronary stenosis (>or=70%) present a clinical and angiographic profile similar to patients with ST elevation myocardial infarction. Thus, the clinical and angiographic features as well as follow-up events of 200 patients were prospectively analyzed and were compared with those of 422 patients with a first ST elevation myocardial infarction survivors of the early phase (3 days) and those of 70 patients with variant angina and non significant stenosis. Age and incidence of smoking, systemic hypertension, diabetes and maximum ST elevation were similar in the 2 groups. Furthermore, among patients with significant coronary stenosis, stenosis severity and the proportion of eccentric lesions were also comparable. Incidence of recent-within 30 days prior to admission-angina at rest was higher in variant angina patients with significant stenosis (67% vs. 27%, p<0.001) than in those with myocardial infarction but long standing angina at rest (>30 days) was low and comparable in these 2 groups (15% vs. 11%, ns). Also, in a 5-year follow-up most patients from these 2 groups were free from angina at rest (86% vs. 84%) which in variant angina patients was largely attributable to a high revascularization rate (72%). Moreover, the rate of myocardial infarction/cardiac death (20% vs. 19%) was also similar. Patients with variant angina and non-significant stenosis, however, had longer antecedent angina, more frequent follow-up angina and a lower incidence of cardiac events than the other 2 groups. Thus, these findings suggest that patients with variant angina and significant coronary stenosis generally behave as an acute coronary syndrome-likely associated with an acutely complicated plaque-rather than as recurrent vasospastic angina, and should be managed accordingly.

Non-rapid eye movement sleep parasomnias

Parasomnias are unpleasant or undesirable behavioral or experiential phenomena that occur during sleep. Once believed unitary phenomena related to psychiatric disorders, it is now clear that parasomnias result from several different phenomena and usually are not related to psychiatric conditions. Parasomnias are categorized as primary (disorders of the sleep states) and secondary (disorders of other organ systems that manifest themselves during sleep). Primary sleep parasomnias can be classified according to the sleep state of origin: rapid eye movement sleep, non-rapid eye movement sleep, and miscellaneous (those not respecting sleep state). Secondary sleep parasomnias are classified by the organ system involved.

Thirty day prognosis of patients with acute pulmonary oedema complicating acute coronary syndromes

OBJECTIVES

To investigate the characteristics of the acute coronary syndromes underlying acute pulmonary oedema and their 30 day prognosis.

PATIENTS

185 consecutive patients with acute coronary syndromes and acute pulmonary oedema admitted to a tertiary care centre.

MAIN OUTCOME AND MEASURES

Clinical, ECG, echocardiographic, enzymatic, and angiographic features were prospectively investigated.

RESULTS

Non-ST segment elevation myocardial infarction (NSTEMI) was the most frequent cause of acute pulmonary oedema (61%) followed by unstable angina (UA; 21%) and ST segment elevation myocardial infarction (STEMI; 18%). In each group, mean age was > or = 70 years, but NSTEMI patients were the oldest and > or = 65% of patients had chronic hypertension. Moreover, patients with NSTEMI and UA were older and had a higher incidence of diabetes, previous myocardial infarction, and moderate to severe mitral regurgitation but a similarly reduced ejection fraction (NSTEMI, 41%; UA, 39%; and STEMI, 39%) and increased incidence of diastolic dysfunction and rate of multivessel disease (94%, 87%, and 86%, respectively). However, patients with STEMI had a higher creatine kinase MB peak concentration (158 v 76 microg/l in the NSTEMI group, p < 0.001) and 30 day mortality (26% v 9% in the NSTEMI group and 8% in the UA group, p < 0.024). Multivariate analysis identified ejection fraction < 40% and a peak creatine kinase MB concentration > 100 microg/l as the main prognostic markers (p < 0.03).

CONCLUSIONS

Acute pulmonary oedema is mostly a complication of elderly hypertensive patients with NSTEMI or UA (82%) and with multivessel disease often associated with mitral regurgitation. On the other hand, the larger infarct size and higher mortality in patients with STEMI with a similarly reduced ejection fraction suggest a more extensive acute systolic loss.

Acute cardiogenic pulmonary edema--relevance of multivessel disease, conduction abnormalities and silent ischemia

The frequency distribution and severity of the cardiac disease underlying acute cardiogenic pulmonary edema (APE) to define appropriate subsequent diagnostic and management strategies were investigated in 216 consecutive patients. To this effect, the clinical, electrocardiographic, ecocardiographic and angiographic characteristics were analyzed. Coronary artery disease was identified in 185 patients (86%)-146 with acute myocardial infarction-as the underlying cause, isolated valvular disease in 10 (5%) and other causes in 21 (11%). Most patients were elderly (> or =70 years, 72%), hypertensive (71%) and diabetic (44%). Among coronary disease (CAD) patients, however, 105 (57%) showed conduction disturbances in the ECG (QRS>0.10 s) and 84 (45%) had no anginal pain during pulmonary edema. A 2D echocardiogram showed a 30% incidence of moderate-severe mitral regurgitation in coronary disease and non-coronary disease patients, and a 67% incidence of reduced ejection fraction (<50%), particularly in coronary disease patients (73%). A coronary angiography performed in 99 patients with coronary disease showed multivessel disease in 89 (91%) with a 32% incidence of significant left main disease. Therefore, these findings demonstrate that coronary disease is the most common cause of acute pulmonary edema and it is associated with a distinctly high prevalence of multivessel and left main disease. This diagnosis, however, may often be overlooked if no serial enzymatic sampling is performed given the increased frequency of conduction abnormalities and lack of anginal pain.

Relevance of multivessel disease in the development of in-hospital refractory angina and myocardial infarction in patients with unstable angina

We investigated the relationship between clinical, electrocardiographic and angiographic characteristics with development of refractory angina and acute myocardial infarction (AMI) in 976 consecutive patients with unstable angina (UA). AMI occurred in 63 (6%) and recurrent angina in 384 (39%), 201 of whom had >2 episodes (refractory, 21%). Patients with AMI were older (P<0.001) and had a higher rate of smoking (P<0.02), previous cerebrovascular accident (P<0.02), abnormal ST segment on admission (P<0.002), refractory angina (P<0.001) and multivessel disease (P<0.005) than those without AMI. Patients with refractory angina were older (P<0.001) and showed a higher incidence of abnormal ST segment on admission (P<0.001) and multivessel disease (P<0.001) than those without. A multivariate analysis, however, showed that refractory angina (P<0.0001), and multivessel disease (P<0.001) were the strongest predictors of AMI while age and multivessel disease were the strongest predictors of refractory angina (P<0.003). Thus, multivessel disease was the most frequent substrate of refractory angina and AMI in patients with UA. These findings may suggest that significant coronary stenosis in non-culprit arteries may facilitate recurrence of ischemia/AMI perhaps by reacting in concert with the culprit lesion and causing a further reduction of the ischemic threshold.

[Prognostic value of cardiac perfusion scintigraphy associated with the dobutamine test in acute coronary syndromes]

OBJECTIVES

This study aimed to establish the value of myocardial ischemia induced by the dobutamine infusion test associated to 99m technetium isonitrile single photon emission computed tomography in patients with unstable angina or non Q-wave infarction during the first days in the Coronary Care Unit.

METHODS

Fifty three patients with unstable coronary syndromes and common medical treatment were studied with a moderate-dose dobutamine test (5 to 20 microgram/Kg/min) using a 99mTc-MIBI SPECT. The results were correlated with the incidence of recurrent angina, infarction, death or revascularization.

RESULTS

The dobutamine test induced a reversible perfusion defect in 36 patients (68%) and angina in 12 of them (12/36, 33%). However, the patients who had a positive test had a similar incidence of events as those with a negative test (58% vs 59%). Thus, while the sensitivity of the dobutamine test to identify patients at risk was relatively high (68%), its specificity (32%) and its negative predictive value (41%) were low. The patients with dobutamine-induced angina, however, had a higher scintigraphy score (3.0 +/- 1,7 vs 1.6 +/- 1.8, p < 0.02) and a higher incidence of recurrent angina (8/12, 67% vs 13/41, 31%, p < 0.04) than those without, at a comparable double product.

CONCLUSIONS

In conventionally treated patients with unstable coronary syndromes, the specificity of the inducible scintigraphic ischemia with moderate dose of dobutamine performed during the first days is too low to be used as a marker for in-hospital events. However, inducible angina with dobutamine suggests an extensive jeopardized area and/or a particularly reduced ischemic threshold.

Thrombin formation and fibrinolytic activity in patients with acute myocardial infarction or unstable angina: in-hospital course and relationship with recurrent angina at rest

OBJECTIVES

The goal of this study was to investigate possible differences in thrombin generation or fibrinolytic capacity in patients with unstable angina (UA) or acute myocardial infarction (AMI) with or without recurrent angina at rest.

BACKGROUND

Angina at rest in patients with AMI or UA is generally produced by a reduction in coronary flow, but it is unclear whether patients with or without this event differ in their thrombin generation or in their fibrinolytic capacities, which might influence the course of the culprit lesion.

METHODS

Thrombin-antithrombin complex (TAT), D-dimer, fibrinogen and plasminogen activator inhibitor (PAI-1) antigen plasma levels were determined in 40 patients with AMI and in 23 with UA on admission, at 10 days and at three months.

RESULTS

First day values for TAT, fibrinogen and D-dimer were comparable in patients with AMI and in those with UA. At 10 days they increased significantly in each group, and at 3 months they decreased to a similar extent. First day PAI-1 levels, however, were highest in both groups and declined in AMI patients at 10 days and at three months, whereas they also decreased at 10 days in UA patients but not any further at three months. Ten patients with AMI (25%) and 12 with UA (52%) developed in-hospital angina at rest. First day values for TAT, fibrinogen and D-dimer were similar in patients with or without angina, but PAI-1 levels were higher in the former subset (p < 0.008). At 10 days, however, TAT (p < 0.013) and D-dimer (p < 0.013) were higher in patients who developed angina than in those who did not.

CONCLUSIONS

The higher inhibition of fibrinolytic activity in the first day in patients with AMI or UA who will develop recurrent angina suggests that maintenance of a prothrombotic status may contribute to its mechanisms, perhaps by preventing passivation of the culprit thrombus/plaque. This is consistent with greater thrombin generation and greater levels of fibrynolitic products at 10 days observed in these patients compared with those who attain early stability.

Fasting and postprandial ischemic threshold in patients with unstable angina with and without postprandial angina at rest

BACKGROUND

Postprandial angina develops within minutes after a meal in patients with unstable angina, but the clinical characteristics of these patients and why it develops in only some of those with advanced coronary artery disease remain largely unknown. A severely reduced coronary reserve associated with postprandial increases in heart rate could be a contributory mechanism.

METHODS

The clinical and angiographic characteristics of 277 patients with unstable angina with (23) or without (254) postprandial angina were analyzed. The coronary reserve was also analyzed by measuring the ischemic threshold by atrial pacing in a fasting state in all patients and 15 minutes after a 900-calorie meal in 54.

RESULTS

Patients with postprandial angina were older, more likely to be women, and had a higher incidence of hypertension and three-vessel disease than those without (p < 0.005) and had a lower fasting ischemic threshold (131.8 [SD 13.0] vs 147.5 [SD 23.4] beats/min, p < 0.0001). However, 67 of the 79 patients with the lowest fasting thresholds (< or =130 beats/min) (84.8%) had no postprandial angina. Moreover, among patients with and without postprandial angina who were matched for age, sex, and extent of coronary disease, the ischemic threshold was also lower in those with postprandial angina (p < 0.005) and there were no differences in left ventricular end-diastolic pressure or volume. Postprandial pacing was positive in 37 patients but postprandial ischemic threshold was comparable to fasting threshold (132 [SD 14] vs 132 [SD 16] beats/min). Moreover, in the 10 patients who experienced in-hospital postprandial angina, heart rate during postprandial angina was similar to nonpostprandial angina (93.1 [SD 14.7] vs 90.3 [SD 17.6]) and lower than the fasting ischemic threshold (132.0 [SD 10.8] beats/min, p < 0.0001).

CONCLUSIONS

Thus postprandial angina tends to occur among elderly and hypertensive patients with advanced coronary disease and severely reduced ischemic threshold. The fact that the postprandial ischemic threshold was clearly higher than the heart rate attained during postprandial angina suggest that factors others than increases in heart rate account for postprandial angina. Furthermore, the lack of a decline in the postprandial ischemic threshold suggests that, in the absence of postprandial angina, there is not a consistent postprandial change in coronary tone or that the increases in myocardial oxygen demands due to increased myocardial contractility-wall tension do not seem to play a major role in postprandial ischemia.

Adherence to a prophylactic medication regimen in patients with symptomatic versus asymptomatic ischemic heart disease

Although angina pectoris is the most common symptom of coronary artery disease, some patients do not experience angina during ischemic episodes. The effects of asymptomatic (silent) heart disease on patient self-management have rarely been studied. Studies of other patient populations with asymptomatic illnesses indicate that patients with silent myocardial ischemia might adhere less well to a prophylactic medication regimen than would those with symptomatic ischemia. Depression, a state associated with poor adherence to medical regimens is more common among patients with symptomatic ischemia. For prevention of thromboembolic events, 37 patients with documented ischemic heart disease who denied having anginal symptoms and 28 patients who reported almost daily symptoms were given a 3-week supply of low-dose aspirin packaged in an unobtrusive electronic adherence monitor. All other medications were provided in standard pill bottles. The symptomatic patients removed their prescribed aspirin on 62.4% of the days; the patients with silent ischemia took their medication on 77.3% of the days. Possible explanations for these results, their clinical implications, and directions for future research are discussed.

[Prognosis of patients with angina pectoris or silent ischemia: exercise 99mTC-MIBI SPECT]

INTRODUCTION AND OBJECTIVES

Although different reports have compared the extent of the myocardial ischemia in patients with or without angina during exercise test, there have been few publications which have studied their prognosis. The aim of this study is to analyze the prognostic value of the presence of angina during 99mTc-MIBI SPECT in patients with proven coronary artery disease without previous myocardial infarction.

PATIENTS AND METHODS

We studied 82 patients prospectively with at least one coronary stenosis > 70% and with reversible perfusion defects in 99mTc-MIBI SPECT (long protocol). Twenty two of these patients had angina during exercise test. The extension of ischemia was quantified on SPECT and the severity of coronary stenoses on coronary angiography. The mean follow-up period was 3.2 years.

RESULTS

The angina patients showed a significantly lower coronary reserve (exercise duration: 6.3 min vs 8 min; p = 0.03), a lower maximal O2 consumption (5.8 METs vs 6.2 METs; p = 0.04), a higher rate of ST depression > 1 mm (64% vs 19%; p = 0.006) and a higher degree of ST depression (0.9 mm vs 0.4 mm; p = 0.01) than those patients without angina. There were no significant differences in the extent of ischemia in SPECT or in the angiographic severity of coronary disease between either groups. During the follow-up period the presence of severe complications (myocardial infarction or death) tended to be higher (27% vs 17%; NS) in patients with angina and the indication of surgical revascularization was also significantly higher (50% vs 17%; p = 0.002) in this group.

CONCLUSIONS

Presence of angina during 99mTc-MIBI SPECT portends a higher risk of medium and long term complications, mainly due to surgical revascularization.

Parasomnias including the restless legs syndrome

The three states of mammalian being, W, REM sleep, and NREM sleep, are not mutually exclusive, and may occur simultaneously, oscillate rapidly, or appear in dissociated or incomplete form to produce primary sleep parasomnias. In addition, dysfunctions of a wide variety of organ systems may take adwide variety of organ systems may take advantage of the sleeping state to declare themselves, resulting in secondary sleep parasomnias. Contrary to popular opinion, the majority of the often bizarre and frightening experiences are not the manifestation of underlying psychological or psychiatric conditions. There is an interesting interaction between sleep-disordered breathing and parasominas. Formal study in an experienced sleep disorders center will usually reveal a diagnosable and treatable condition that explains the spells. Continued study of unusual sleep-related events undoubtedly will reveal more fascinating conditions, expanding our knowledge of sleep physiology, and strengthening the bonds between clinicians and basic-science sleep researchers.

Blood pressure changes during transient myocardial ischemia: insights into mechanisms

OBJECTIVES

We investigated the contribution of changes in systemic blood pressure to the genesis of spontaneous myocardial ischemia.

BACKGROUND

Although increases in heart rate often precede the development of spontaneous myocardial ischemia, it remains a subject of controversy whether these are accompanied by simultaneous changes in blood pressure.

METHODS

Using an ambulatory monitoring device that triggered blood pressure recordings from the level of the ST segment, we documented systolic and diastolic blood pressure and heart rate changes related to episodes of ST segment depression in 17 patients with stable coronary artery disease.

RESULTS

Systolic blood pressure and heart rate, but not diastolic pressure, increased significantly before the onset of ST segment depression and persisted throughout the ischemic episode. There was a significant correlation between the changes in heart rate and systolic blood pressure during episodes of myocardial ischemia (r = 0.5, p = 0.0005) and between heart rate and systolic blood pressure changes at 1-mm ST segment depression during treadmill exercise testing and ambulatory monitoring (r = 0.73, p = 0.0005 for heart rate; r = 0.77, p = 0.0008 for systolic blood pressure), indicating that patients with a low heart rate threshold during ischemic episodes also had a lower systolic blood pressure threshold before ischemia during both tests. Circadian changes in systolic blood pressure paralleled the variations in heart rate and ischemic episodes, with the lowest values at night.

CONCLUSIONS

Significant increases in myocardial oxygen demand, including systolic blood pressure, occur during episodes of spontaneous myocardial ischemia. Patients with a lower heart rate threshold during ischemic episodes had a lower systolic blood pressure threshold during both ambulatory monitoring and treadmill exercise. The effects of antianginal therapy on blood pressure changes during ischemia need to be explored further.

Decreased digital flow persists after the abatement of cocaine-induced hemodynamic stimulation

This study determined whether the development of delayed ischemic sequelae due to cocaine use--after the return of arterial blood pressure (BP) and heart rate to near-baseline values--may be attributable to regional vasoconstriction which persists beyond the acute systemic hemodynamic response. Five cocaine-using volunteers received intravenous infusions of saline placebo and cocaine 0.50 mg/kg several days apart in a double-blinded cross-over design. The intensity and duration of the cocaine-induced decrease in peripheral blood flow (as documented by laser Doppler flowmetry of the finger) were compared to the increases in BP (obtained with a Dinamap) and heart rate using paired t-test and repeated-measures analysis of variance. A significant increase in BP and a significant decrease in finger flow were noted by the first time point (5 min). Within 15 min, cocaine induced a 36% +/- 5% increase in BP and a 73% +/- 18% decline in finger flow (P < 0.05 for difference between percent change in BP and percent change in flow). Dinamap(systolic) and Dinamap(diastolic) returned to within 15% of baseline within 30 min, while finger flow remained more than 50% below baseline for the remainder of the 60-min study period (P < 0.05). Changes in heart rate paralleled those in BP. Except for isolated cases of documented coronary vasoconstriction in patients presenting with complications after cocaine use, this study is the first to document the persistence of cocaine-induced vasoconstriction of a sensitive vascular bed beyond the hypertensive response. It thus helps to explain the development of ischemic injury after cocaine use despite a stable rate-pressure product.

NREM sleep parasomnias

The three states of mammalian being--wakefulness, REM sleep, and NREM sleep--are not mutually exclusive and may occur simultaneously, oscillate rapidly, or appear in dissociated or incomplete form to produce primary sleep parasomnias. Dysfunctions of a wide variety of organ systems may take advantage of the sleeping state to declare themselves, resulting in the secondary sleep parasomnias. Contrary to popular opinion, most of these often bizarre and frightening experiences are not the manifestation of underlying psychological or psychiatric conditions. Formal study in an experienced sleep disorders center usually reveals a diagnosable and treatable condition. Various parasomnias may result in injurious or violent behavior. The forensic science implications are beyond the scope of this article but have been reviewed extensively elsewhere. Continued study of unusual sleep-related events undoubtedly will reveal more fascinating conditions, expanding our knowledge of sleep physiology and strengthening the bonds between clinicians and basic science sleep researchers.

Calcium channel antagonists in the management of anginal syndromes: changing concepts in relation to the role of coronary vasospasm

Despite the increasing evidence that alterations in coronary vascular tone can and do occur in patients with anginal syndromes, only in a minority of such patients with Prinzmetal's angina is there decisive evidence that the coronary vasodilation induced by calcium channel antagonists (CCAs) plays a specific therapeutic role. CCAs may also give therapeutic benefit in a number of conditions in which coronary vasoconstriction may contribute to ischemia, such as hyperventilation, cold-induced angina, or silent ischemia not caused by an increase in heart rate. Thus, the decision of whether or not to use CCAs in angina syndromes will often have to be made on grounds other than what appears to be a minor role of vasospasm in the overall spectrum of angina. There are preliminary indications that the long-term prognosis may be different among different categories of CCAs.

Comparative study of left ventricular function in patients with unstable angina, non-Q wave myocardial infarction and stable angina pectoris: assessment with atrial pacing and digital ventriculography

To compare left ventricular global and segmental function at rest and during right atrial pacing in patients with unstable angina, non-Q wave myocardial infarction, and stable angina (class III angina), low-dose digital subtraction ventriculography was performed at rest and after abrupt cessation of pacing in 42 patients with unstable angina, 8 patients with non-Q wave myocardial infarction and 15 patients with stable angina during selective coronary arteriography. Left ventricular ejection fraction was significantly lower at rest in patients with unstable angina (P < 0.01) and non-Q wave myocardial infarction (P < 0.05) and during pacing (P < 0.01). These two groups of patients had significantly higher values of left ventricular end-diastolic and end-systolic volumes at rest and during pacing as compared with stable angina group. In comparing various clinical patterns of unstable angina, ejection fraction was significantly (P < 0.05) lower during pacing in patients with crescendo angina than in new-onset angina. However, ejection fraction was significantly (P < 0.01) lower in crescendo angina only at rest as compared with rest angina. The length of zone of severe hypokinesia was greater in unstable angina (P < 0.01) as well as in non-Q wave myocardial infarction (P < 0.05) both at rest and during pacing as compared with stable angina. Contractility of region of hypokinesia during pacing was higher (P < 0.01) in stable angina than in unstable angina and non-Q wave myocardial infarction. In analyzing segmental function in various subgroups of unstable angina, the authors found that the length of total hypokinesia was significantly higher (P < 0.05) during pacing in crescendo angina than in new-onset angina. Contractility of region of hypokinesia was lowest at rest and during pacing in patients with crescendo angina. This study demonstrates that patients with unstable angina as well as non-Q wave myocardial infarction were characterized by more pronounced global and segmental left ventricular dysfunction at rest and during pacing as compared with patients with stable angina, which may explain the poorer prognosis in the former two groups. This study also shows that patients with crescendo angina have more profound left ventricular global and regional dysfunction as compared with patients with new-onset as well as rest angina.

The role of heart rate in myocardial ischemia and infarction: implications of myocardial perfusion-contraction matching

The pathophysiology of myocardial ischemia traditionally has been attributed to disturbances of oxygen demand, as observed in classic effort-induced angina pectoris, or to a primary disruption of coronary blood supply, as in unstable angina or acute myocardial infarction. Laboratory research eliciting various types of perfusion-contraction matching has challenged such a historical distinction between supply and demand-induced determinants of myocardial ischemia. A growing number of clinical studies analyzing the role of heart rate in the course of coronary heart disease suggest the possibility that a common perfusion-contraction scheme may underlie these diverse clinical manifestations. During experimental myocardial ischemia, produced by a low coronary blood flow, regional perfusion-contraction matching exists in which the energy demands and regional contraction are reduced to match the diminished myocardial substrate supply. Heart rate is a major factor influencing transmural blood flow distribution and regional function, because when coronary vasodilation is maximal there is an inverse relation between the level of heart rate and subendocardial perfusion. Thus, in experimental regional ischemia, increasing heart rate reduces subendocardial flow and contraction, whereas slowing of heart rate causes improvement of contraction associated with increased subendocardial blood flow, accompanied by a decrease in outer wall blood flow. Also, "interventricular steal" of blood from the left ventricle by the right ventricle during ischemia can be reversed by slowing the heart rate in the presence of regional ischemia. Improvement of contraction by heart rate slowing is more than would be expected on the basis of the increase in subendocardial perfusion alone, reflecting a combination of decreased oxygen demand and increased oxygen supply, and separate curves relating blood flow per minute to contractile function are observed at different heart rates. However, when perfusion is normalized for heart rate by expressing subendocardial blood flow in units per beat, a single relation is observed at different heart rates. This observation supports the concept of a close coupling between subendocardial blood flow per beat and regional performance, or perfusion-contraction matching, during various levels of ischemia. Based on these principles, it can be predicted that exercise-induced regional ischemia in the presence of coronary stenosis will be attenuated by several mechanisms when heart rate is slowed using either a beta-blocking agent, or a specific bradycardic drug.(ABSTRACT TRUNCATED AT 400 WORDS)

In-hospital prognostic relevance of a reduced ischemic threshold. Studies in 357 consecutive patients with acute coronary syndromes

In 357 patients with unstable coronary syndromes, a reduced pacing ischemic threshold (1-mm ST-segment depression at a heart rate < or = 150 beats per minute) was an independent predictor of main in-hospital events (death, myocardial infarction, or coronary surgery), which occurred in 33 percent (65/200) of the patients with a reduced threshold and in 8 percent (13/157) of those with a normal threshold (p < 0.0001). The incidences of death and infarction in patients with a normal (> 150 beats per minute), modestly reduced (140 to 150 beats per minute), or severely reduced (< or = 130 beats per minute) threshold were progressively higher (1 percent and 4 percent; 3 percent and 12 percent; and 7 percent and 18 percent respectively; p < 0.01). Thus, a reduced coronary reserve is associated with a fourfold increase in in-hospital complications; and when the reserve is severely curtailed, there may be a sevenfold increase in mortality.

Prognostic implications of myocardial ischemia during daily life in low risk patients with coronary artery disease

OBJECTIVES

The purpose of this study was to determine the incidence and prognostic importance of myocardial ischemia detected by ambulatory monitoring in low risk, medically managed patients with coronary artery disease.

BACKGROUND

Previous studies have demonstrated that certain high risk subsets of patients with coronary artery disease have improved survival with revascularization. The remaining low risk medically managed patients may still have episodes of silent ischemia during daily living, but the frequency and prognostic implications of such episodes in this group are unknown.

METHODS

We prospectively studied the incidence and prognostic significance of ST segment changes recorded during daily activities in 116 asymptomatic or mildly symptomatic low risk patients with native coronary artery disease who were followed up for 29 +/- 13 months. Low risk patients were selected after excluding patients with 1) left main disease; 2) three-vessel coronary artery disease and left ventricular dysfunction at rest; 3) three-vessel disease and inducible ischemia during exercise; and 4) two-vessel disease, left ventricular dysfunction and inducible ischemia.

RESULTS

Forty-five patients (39%) had transient episodes of ST segment depression during 48-h electrocardiographic (ECG) monitoring (total 217 episodes, lasting 7,223 min, 82% of episodes silent). There were eight acute cardiac events (seven myocardial infarctions, one episode of unstable angina) and nine patients underwent elective revascularization. Seven of the eight acute events occurred in patients without silent ischemia during monitoring. Kaplan-Meier survival analysis revealed no significant differences in event-free survival from either acute or total events in subgroups with or without silent ischemia during ambulatory ECG monitoring. None of the clinical, treadmill exercise, radionuclide ventriculographic or cardiac catheterization variables were predictive of outcome by Cox multivariate proportional hazard function analysis. Analysis of coronary arteriograms before and after acute cardiac events revealed that in five of the six patients studied, acute occlusion occurred in a coronary artery different from the artery with the severest stenosis on initial angiography.

CONCLUSIONS

In patients categorized as at low risk on the basis of the results of cardiac catheterization and stress testing, silent myocardial ischemia during daily life was not uncommon, and its presence failed to predict future coronary events.

Role of myocardial oxygen demand in the pathogenesis of silent ischemia during daily life

The role of myocardial oxygen demand in the pathogenesis of silent ambulatory myocardial ischemia was evaluated by reviewing and assessing the methods and results of recent studies. The performance of simultaneous ambulatory electrocardiographic and blood pressure monitoring in 25 men with proven coronary artery disease (CAD) revealed significant increases in heart rate and blood pressure (p < 0.001) preceding most silent ischemic events. By plotting the mean heart rate obtained at 5-minute intervals during the 30 minutes before an ischemic event, the ischemic heart rate was shown to be significantly higher (95 +/- 15 vs 74 +/- 11 beats per minute [bpm]; p < 0.01) than the nonischemic heart rate. The evaluation of heart rate changes during ambulatory ischemia (in patients with CAD and ischemia induced by an exercise test using gradual work load increments) showed a significant heart rate increase (> 10 bpm) at 1-5 minutes preceding the onset of ST-segment depression. Heart rate increases during exercise testing according to the gradual work load increments of the National Institutes of Health protocol were compared with the heart rate preceding ischemic events during daily life monitored by ambulatory electrocardiography and were found to be closely related. In contrast, heart rate increases that occurred during exercise testing using the standard Bruce protocol were higher and correlated less with those preceding ischemia in daily life. Heart rate and blood pressure increased significantly in most silent ischemic episodes, indicating that increased myocardial oxygen demand plays a significant role in the pathogenesis of myocardial ischemia during daily life.

Comparison of ST depression recorded by Holter monitors and 12-lead ECGs during coronary angiography and exercise testing

Data from previous studies are debatable regarding whether Holter monitors are a reliable electrocardiographic indicator of ischemia, for which the 12-lead electrocardiogram (ECG) is the standard. Simultaneous 12-lead and Holter ECGs were performed on 30 patients with typical angina pectoris during coronary angiography or exercise testing. ST depression recorded by both methods was directly compared, using the 12-lead ECG as the reference. The Holter tapes were also scanned by two automated ST analysis programs and the results were compared to 12-lead ECGs. Only 66 of the 178 12-lead ECG ST depression events were also present on the Holter recordings (37.1% Holter sensitivity). ST depression was underestimated by the Holter recordings compared to the 12-lead ECGs (p < 0.0001). The majority (67.0%) of ST depression events identified by one computer program were false positive events. The degree of ST depression was overestimated compared to 12-lead ECGs by the second program (p = 0.0033). Holter-detected ST depression may not be a reliable ECG indicator of myocardial ischemia.

Circadian distribution of onset of acute myocardial infarction in subgroups from analysis of 10,791 patients treated in a single center

A circadian variation of symptom onset in acute myocardial infarction (AMI) with an increased frequency in the late morning and possibly also in the evening has been found in several studies. It has been suggested that different circadian rhythms may exist in various subgroups of patients. This possibility was examined in a population of 10,791 patients collected between 1973 and 1987 in a continuously operating register of patients with AMI in Malmö, Sweden. In 6,763 patients (63%) in whom a distinct symptom onset could be established, symptom onset occurred with an increased frequency between 6:01 A.M. and 12:00 noon (30.6%) and between 6:01 P.M. and 12:00 midnight (26.9%). Similar bimodal circadian rhythms were seen in patients aged greater than 70 years (n = 2,923), less than or equal to 70 years (n = 3,840), men (n = 4,528), women (n = 2,235), smokers (n = 2,458), hypertensives (n = 1,999), diabetics (n = 653), patients with (n = 1,872) and without (n = 4,891) a history of previous AMI, and in patients with recent non-Q-wave AMI (n = 333). In 455 patients receiving cardioselective beta blockers the circadian distribution did not differ from a random, whereas in patients taking nonselective beta blockers or calcium antagonists significant bimodal rhythms were found. Statistically significant interactions were found between symptom onset and age dichotomized at 70 years, and between patients with and without a history of previous AMI. In a multivariate analysis only these variables age less than or equal to/greater than 70 years; +/- history of a previous AMI) were found to modify the circadian rhythm of symptom onset in the population.(ABSTRACT TRUNCATED AT 250 WORDS)

Relation between left ventricular function at rest and with exercise and silent myocardial ischemia

The prognostic value of radionuclide measures of left ventricular function at rest and exercise is well established. Some studies have suggested that the frequency and duration of silent ischemia during ambulatory monitoring provide similar prognostic information; however, studies comparing these two techniques have not been performed. This study examines the relation between left ventricular function at rest and exercise-induced ischemia assessed by radionuclide ventriculography with myocardial ischemia during ambulatory electrocardiographic (ECG) monitoring. Of the 155 patients with coronary artery disease studied, 88% had left ventricular dysfunction with exercise, defined as failure of the ejection fraction to increase by greater than 4% with exercise, and 33% of patients had left ventricular dysfunction at rest (ejection fraction less than 45%); 52% had transient episodes of ST segment depression during 48-h ambulatory ECG monitoring. Exercise-induced left ventricular dysfunction during radionuclide ventriculography was extremely sensitive (94%) in detecting patients with ischemic episodes during ambulatory ECG monitoring; however, only 55% of patients with exercise-induced left ventricular dysfunction had ST segment depression during ambulatory monitoring. Moreover, patients with left ventricular dysfunction at rest had a lower prevalence of transient episodes of ST segment depression (31%) than did patients with normal left ventricular function at rest (62%) (p = 0.008). The relation between prognostically important variables during exercise radionuclide ventriculography and the number and duration of transient episodes of ST depression was examined.(ABSTRACT TRUNCATED AT 250 WORDS)

Attenuation of circadian variation by combined antianginal therapy with suppression of morning and evening increases in transient myocardial ischemia

The circadian variation of total ischemic activity was examined during 3289 hours of ambulatory ECG monitoring in 101 patients with stable angina pectoris and proved coronary artery disease, who were not receiving any prophylactic antianginal therapy. The 101 patients displayed 411 episodes of ischemia, 312 (76%) of which were silent; a circadian rhythm was noted for the occurrence of total and silent ischemia. Thirty-eight percent of the ischemic episodes occurred between 6 AM and 12 noon, and total and silent ischemia were significantly more frequent during this period compared with the other three 6-hour periods (p less than 0.01); a lesser peak was noted in the evening. The effects of metoprolol and combined therapy with metoprolol and nifedipine on the circadian variation of ischemic activity were studied in two subgroups of patients in a random, double-blind study design (31 patients receiving metoprolol and 42 receiving combined therapy). During therapy with metoprolol the morning increase in ischemic activity was attenuated, and the highest frequency of ischemia was then noted in the evening (6 AM to 12 noon compared with 6 PM to 12 midnight; p less than 0.05). Combined therapy abolished the morning peak as did metoprolol monotherapy, but even the evening increase in ischemic activity was attenuated (p less than 0.05). The diurnal distribution of the mean heart rate at the onset of ischemia, when patients were off therapy, showed a morning increase similar to the increase in ischemic activity but no second peak in the evening.(ABSTRACT TRUNCATED AT 250 WORDS)

Myocardial ischemia during daily activities: the importance of increased myocardial oxygen demand

The role of increased myocardial oxygen demand in the pathophysiology of myocardial ischemia occurring during daily activities was evaluated in 50 patients with coronary artery disease and exercise-induced ST segment depression. Each patient underwent ambulatory electrocardiographic (ECG) monitoring for ST segment shifts during normal daily activities and symptom-limited bicycle exercise testing with continuous ECG monitoring. All 50 patients had ST depression greater than or equal to 0.1 mV during exercise. A total of 241 episodes of ST depression were noted in the ambulatory setting in 31 patients; only 6% of these were accompanied by angina pectoris. Significant (0.1 mV) ST depression during ambulatory monitoring was preceded by a mean increase in heart rate of 27 +/- 12 beats/min. Patients with ischemia during daily activities developed ST depression earlier during exercise (7.9 +/- 4.4 vs. 14.2 +/- 6.4 min, p less than 0.001) and tended to have significant ECG changes at a lower exercise heart rate and rate-pressure product than did those without ST depression during ambulatory monitoring. In the 31 patients with ischemia during daily activities, the mean heart rate associated with ST depression in the ambulatory setting was closely correlated with the heart rate precipitating ECG changes during exercise testing (r = 0.74, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence for reduced fibrinolytic activity in unstable angina at rest. Clinical, biochemical, and angiographic correlates

BACKGROUND

The goal of this study was to evaluate the role of the fibrinolytic system in patients with unstable angina at rest associated with transient electrocardiographic changes.

METHODS AND RESULTS

Tissue plasminogen activator activity in plasma was comparable among patients with unstable angina (n = 17), patients with stable exertional angina (n = 10), and control patients with normal coronary arteriograms (n = 8). In contrast, plasminogen activator inhibitor-1 (PAI-1) activity in plasma was elevated in the unstable angina group (21.67 +/- 9.52 AU/ml) as compared with either the stable angina group (12.01 +/- 7.06 AU/ml, p less than 0.02) or the controls (12.49 +/- 8.54 AU/ml, p less than 0.02). Coronary angiography performed within 24 hours after the last anginal episode showed a similar extent of coronary artery disease in the unstable and stable angina groups. However, intracoronary thrombi were observed in eight patients in the unstable angina group while no thrombus was noted in the stable angina group (chi 2 = 7.22, p less than 0.01).

CONCLUSIONS

We conclude that patients with unstable angina at rest have a reduced fibrinolytic activity and an increased incidence of intracoronary thrombi. It is postulated that elevated PAI-1 activity in the presence of coronary arterial wall injury may be an important factor leading to the development of acute coronary syndromes.

Circadian variation in the frequency of onset of chest pain in acute myocardial infarction

The time of onset of chest pain was studied prospectively in 1154 consecutive patients admitted to a coronary care unit with myocardial infarction during a five year period. Statistical analysis confirmed a previous finding in a retrospective study of a bimodal frequency distribution with peaks in the time of onset of chest pain between 2330 and 0030 hours and between 0630 and 0830 hours.

Pathophysiology of silent myocardial ischemia during daily life. Hemodynamic evaluation by simultaneous electrocardiographic and blood pressure monitoring

The role of myocardial oxygen demand in the genesis of silent myocardial ischemia was evaluated by measuring the heart rate and blood pressure changes preceding the silent ischemic events during daily life in 25 men with proven coronary artery disease. Simultaneous 24-48-hour ambulatory electrocardiographic and blood pressure monitoring were performed during unrestricted daily activities. Of the 92 transient ischemic events recorded during monitoring, 85 (92%) were silent. Sixty-one percent of the silent events were preceded by an increase in the heart rate of 5 beats/min or more. Seventy-three percent of the silent ischemic events showed an average increase of 10 mm Hg in systolic blood pressure within 6 minutes preceding the onset of ST segment depression. The silent ischemic events showed a circadian pattern with a high density (34% of total events) between 6:00 AM and noon. The increase in heart rate and blood pressure paralleled the increase in silent ischemic events during these hours. These results showing significant (p less than 0.001 for both) increases in heart rate and blood pressure preceding a majority of silent ischemic events suggest that increase in myocardial oxygen demand plays a significant role in the genesis of silent ischemia. This pathophysiological mechanism has important therapeutic implications.

Reflex increase in blood pressure during the intracoronary administration of adenosine in man

Infusion of adenosine (0.022-2.2 mg/min) into the left anterior descending (LAD) coronary artery of 26 patients produced a dose-dependent increase in blood pressure without a change in heart rate. At adenosine 2.2 mg/min, systolic pressure rose by 21.0 +/- 2.2 mmHg from 134 +/- 4.3 mmHg (P less than 0.001) and diastolic pressure increased by 10.4 +/- 1.1 mmHg from 76 +/- 1.9 mmHg (P less than 0.001). The rise in arterial pressure was associated with a 22 +/- 3.4% increase in systemic vascular resistance (P less than 0.01) and no change in cardiac output (-2.8 +/- 4.3%, P = NS). Plasma norepinephrine levels rose by 40 +/- 14% from 105 +/- 9 pg/ml (P less than 0.05) and epinephrine levels by 119 +/- 31% from 37 +/- 9 pg/ml (P less than 0.01). Right atrial infusion of adenosine produced insignificant hemodynamic effects, suggesting that systemic spillover of adenosine was not responsible for the observed effects. In 20 cardiac transplant patients with denervated hearts, LAD infusion of adenosine (2.2 mg/min) produced no change in systolic pressure (-0.1 +/- 1.6 mmHg from 139 +/- 3.4 mmHg, P = NS) and a decrement in diastolic pressure (-4.7 +/- 1.2 mmHg from 98 +/- 2.5 mmHg, P less than 0.01). Thus, infusion of adenosine into the LAD coronary artery causes a reflex increase in arterial pressure due to a rise in systemic vascular resistance, probably as a result of increased sympathetic discharge. This reflex pathway may be of importance in disease states such as myocardial ischemia, in which myocardial adenosine levels are elevated.

Differing circadian patterns of symptom onset in subgroups of patients with acute myocardial infarction

Circadian variation of the onset of acute myocardial infarction has been noted in many studies and may carry important pathophysiologic implications. However, only a few previous studies have attempted subgroup analyses. In 4,796 patients with documented acute myocardial infarction, the time of symptom onset was recorded. As in other studies, the peak of onset occurred in the morning from 6:01 AM to 12:00 noon, and 28% of the population (1.16 times the average percentage for the other time periods) experienced symptom onset in that period (p less than 0.001). There was a second, lower peak (25%) in the evening between 6:01 PM and 12:00 midnight, which was also observed in some previous studies. We sought to determine whether or not the presence of subgroups with specific clinical characteristics would exhibit different patterns and thereby contribute to these peaks in the overall population. In patients with a history of congestive heart failure (n = 606) or with non-Q wave infarction (n = 832), a pronounced peak (29%) occurred only in the evening. Two nearly equal peaks were observed in patients older than 70 years of age (n = 1,422), smokers (n = 2,057), diabetics (n = 767), women (n = 1,213), and patients taking beta-blocking drugs (n = 847). Finally, in patients with a previous myocardial infarction (n = 1,104), no peaks were observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential effects of sleep stage on coronary hemodynamic function during stenosis

We have demonstrated in a previous study that in the normal heart REM sleep induces surges in heart rate and coronary blood flow which are abolished by bilateral stellectomy. To study the effects of sleep in the stenosed coronary circulation, dogs were instrumented with Doppler flow probes and hydraulic occluders around the left circumflex coronary artery to measure coronary blood flow and to produce a 60% flow reduction. Catheters were placed in the aorta to measure mean arterial blood pressure. Electrodes were implanted via the frontal sinus to identify sleep stages. In the absence of stenosis, mean blood pressure was 95 +/- 3 mmHg, HR was 111 +/- 4 bpm, and coronary blood flow was 33 +/- 2 ml/min. During stenosis, REM induced episodic increases in heart rate which were accompanied by 38% decreases in coronary blood flow. We conclude that in the stenosed coronary circulation, REM sleep produces episodic sinus tachycardia and coronary blood flow reduction.

Variability of indexes for myocardial ischemia: a comparison of exercise treadmill test, ambulatory electrocardiographic monitoring and symptoms of myocardial ischemia

Fifty-four patients with chronic stable angina were studied to determine and compare weekly variability of indexes for the detection of myocardial ischemia. All patients underwent three single-blind placebo periods, each lasting 1 week. An exercise treadmill test, 24 h ambulatory electrocardiographic (Holter) monitoring (analyzed blindly) and an accurate diary of anginal attacks and nitroglycerin use were obtained at the end of each placebo period. An unbalanced, completely random component of variance analysis was used to calculate a component for within subject variability and a component for among subject variability. The coefficient of variation and percent variation (within subjects) of onset of chest pain during exercise were 19% and 30%, respectively; the corresponding values were 28% and 33% for onset of 1 mm ST depression, 15% and 15% for exercise duration, 44% and 27% for number of ischemic episodes/24 h, 56% and 43% for anginal frequency and 55% and 27% for nitroglycerin consumption, respectively. With use of this statistical method and variation within subjects, the change in the value of each variable necessary to exceed those attributable to spontaneous variation was determined. The trade-off between repeated measurements and number of subjects, the sample size estimated for planning studies and the minimal sample size for using various designs were also determined. Although the data indicate that all indexes for myocardial ischemia, both during exercise and during daily activity, vary considerably, but the exercise variables have less variability and are more reproducible.(ABSTRACT TRUNCATED AT 250 WORDS)

Local platelet activation causes vasoconstriction of large epicardial canine coronary arteries in vivo. Thromboxane A2 and serotonin are possible mediators

The goal of the present study was to demonstrate that intracoronary platelet deposition may trigger intense vasoconstriction of large epicardial coronary arteries in vivo and that this is largely mediated by thromboxane A2 and serotonin released by activated platelets. Cyclic flow variations (progressive declines in blood flow followed by sudden restorations of flow) due to recurrent intracoronary platelet activation and thrombus formation were induced by damaging the endothelium and placing a cylindrical constrictor on the left anterior descending coronary artery (LAD) in open-chest, anesthetized dogs. Coronary diameters were measured in vivo by means of ultrasonic crystals sutured on the LAD immediately distal to the constrictor (LAD1) and 1 cm below (LAD2) and on the circumflex coronary artery (Cx). Coronary artery diastolic diameters were measured continuously before and during cyclic flow variations and after they were abolished by administration of LY53857, a serotonin-receptor antagonist (group 1, n = 7), or SQ29548, a thromboxane-receptor antagonist (group 2, n = 7). During cyclic flow variations, at the nadir of coronary flow, LAD1 (a site of maximal platelet accumulation) cross-sectional area decreased by 52 +/- 10% and 38 +/- 6% in group 1 and 2 animals, respectively (p less than 0.001 compared with values recorded during a brief LAD occlusion obtained by a suture snare), whereas LAD2 (a site of minimal or no platelet accumulation) cross-sectional area did not differ from that recorded during the brief LAD occlusion. SQ29548 abolished cyclic flow variations in seven of seven dogs and LY53857 in six of seven, but they affected the increased coronary vasoconstriction differently: LAD1 cross-sectional area increased by 32 +/- 6% of the control value in SQ29548-treated animals, whereas it returned to baseline dimension values in the LY53857-treated group as these interventions also abolished the cyclic flow variations. We conclude that a marked coronary vasoconstriction may be triggered by local platelet deposition and that thromboxane A2 and serotonin are mediators of this vasoconstriction.

Unstable angina with tachycardia: clinical and therapeutic implications

We prospectively evaluated 19 patients with prolonged chest pain not evolving to myocardial infarction and accompanied with reversible ST-T changes and tachycardia (heart rate greater than 100 beats/min) in order to correlate heart rate reduction with ischemic electrocardiographic (ECG) changes. Fourteen patients (74%) received previous long-term combined treatment with nifedipine and nitrates. Continuous ECG monitoring was carried out until heart rate reduction and at least one of the following occurred: (1) relief of pain or (2) resolution of ischemic ECG changes. the study protocol consisted of carotid massage in three patients (16%), intravenous propranolol in seven patients (37%), slow intravenous amiodarone infusion in two patients (10%), and intravenous verapamil in four patients (21%) with atrial fibrillation. In three patients (16%) we observed a spontaneous heart rate reduction on admission. Patients responded with heart rate reduction from a mean of 125 +/- 10.4 beats/min to 84 +/- 7.5 beats/min (p less than 0.005) and an ST segment shift of 4.3 +/- 2.13 mm to 0.89 +/- 0.74 mm (p less than 0.005) within a mean interval of 13.2 +/- 12.7 minutes. Fifteen (79%) had complete response and the other four (21%) had partial relief of pain. A significant direct correlation was observed for heart rate reduction and ST segment deviation (depression or elevation) (r = 0.7527 and 0.8739, respectively). These patients represent a unique subgroup of unstable angina, in which the mechanism responsible for ischemia is excessive increase in heart rate. Conventional vasodilator therapy may be deleterious, and heart rate reduction in mandatory.

Severity of silent myocardial ischemia on ambulatory electrocardiographic monitoring in patients with stable angina pectoris: relation to prognostic determinants during exercise stress testing and coronary angiography

The relation of silent ischemia in patients with stable angina to known predictors of severity of coronary disease on exercise stress testing and coronary angiography is poorly defined. This issue was therefore examined with use of Holter electrocardiographic (ECG) recordings, treadmill exercise tests and angiographic indexes in 102 patients (not taking antianginal therapy) and the results were compared with Holter and treadmill findings in 42 volunteers. A total of 159 ischemic episodes (90% silent) were identified during 2,503 h on Holter recording in 97 patients (mean duration per episode 22.7 +/- 147 min; range 1 to 234). Holter recordings had a 92% specificity and an 80% positive predictive value, but a sensitivity of only 37% and a negative predictive value of 27% for coronary disease. Sixty-three patients (Group I) had no ischemia on Holter recording, 22 (Group II) had a cumulative duration of 1 to 60 min/24 h and in 12 (Group III) ischemia exceeded 60 min/24 h. There was no significant correlation between cumulative ischemia duration on Holter recording and exercise duration or time to ST segment depression on treadmill exercise. In general, the greater the number of coronary vessels involved and the higher the proximal coronary artery stenosis score, the greater the likelihood of ischemia and the longer the cumulative ischemia duration on Holter recording. Irrespective of the severity of coronary disease, in about 25% of Holter recordings in each angiographic category there were no ischemic episodes.(ABSTRACT TRUNCATED AT 250 WORDS)

Unstable angina: current concepts of medical management

Unstable angina describes a clinical syndrome bridging the gap between stable angina and acute myocardial infarction. By definition, patients with angina of new onset, of a crescendo pattern, and with angina at rest are included in this high-risk group. The underlying pathogenetic mechanisms are complex and include initial atherosclerotic plaque rupture, release of vasoactive substances, and intracoronary thrombus formation. The currently established medical approach of the acute phase consists of heparin for anticoagulation and nitrates combined with beta-blockers for the relief of pain. Calcium antagonists are indicated, if anginal symptoms persist. The effect of thrombolytic therapy is still under investigation. Angina refractory to medical treatment and angina at rest are associated with a particularly unfavorable prognosis and prompt early catheterization. The long-term prognosis of the patient is markedly improved by chronic platelet inhibitory treatment with aspirin.