Significant ST-segment Changes Research Articles

Increases in serum unbound free fatty acid levels following coronary angioplasty

Serum unbound free fatty acid levels (FFA u) were measured in patients undergoing percutaneous transluminal coronary angioplasty (PTCA) using the fluorescent probe acrylodan intestinal fatty acid binding protein (ADIFAB). These are the first measurements of FFA u under nonphysiologic conditions. In these studies, FFA u levels were determined in 22 patients 5 minutes before and 30 minutes after the procedure. Post-PTCA FFA u levels were higher than pre-PTCA levels in all patients. The average post-PTCA level for all patients was 103 nM, about 14-fold higher than the 7.5 nM value observed in healthy subjects. Although all patients exhibited elevated FFA u levels after PTCA, ischemic ST-segment changes were observed in only 11 of these patients. The average post-PTCA FFA u levels for patients with significant ST-segment changes (123 nM) were significantly higher than those in patients who did not exhibit such changes (47 nM). Average FFA u (22 nM) levels before the procedure were elevated in the patient population relative to healthy subjects and these values correlated positively with post-PTCA levels. These results suggest that increased serum FFA u levels reflect angioplasty-induced ischemia and that FFA u levels may provide a more sensitive measure of ischemia than electrocardiographic measurements. Moreover, because 30% of these patients had post-PTCA FFA u concentrations exceeding those found to alter in vitro cell function, the increased serum FFA u levels that accompany ischemia may be deleterious for myocardial function.

Aerobic exercise function of patients with persistent coronary artery aneurysms secondary to Kawasaki disease.

Nine patients with persistent coronary artery aneurysms 1.7-14.0 years after an episode of Kawasaki disease underwent progressive bicycle ergometry with expiratory gas analysis. Two of the patients had aneurysms complicated by angiographically documented coronary artery stenosis. Results of the exercise tests were compared to those obtained from a group of age- and gender-matched normal control subjects. The Kawasaki disease patients did not differ significantly from the control subjects with regard to peak oxygen consumption (81 +/- 7% versus 79 +/- 12% predicted), peak workload (75 +/- 13% versus 77 +/- 9% predicted), anaerobic threshold (21.9 +/- 6.5 versus 18.9 +/- 4.0 ml/kg per minute) or oxygen pulse (96 +/- 7% versus 90 +/- 14% predicted). None of the patients developed significant ST segment changes or rhythm disturbances during exercise. The exercise function of the patients with coronary artery stenosis did not differ from that of patients without stenosis. It was concluded that the aerobic exercise function of patients with persistent coronary artery aneurysms after an episode of Kawasaki disease appears to be well preserved. Kawasaki disease patients with significant coronary artery pathology are not accurately identified by a single assessment of aerobic exercise function.

Transient autonomic dysfunction precedes ST-segment depression in patients with syndrome X

Increased sympathetic drive has been suggested to play a role in the pathogenesis of syndrome X (angina pectoris, positive exercise testing, and angiographically normal coronary arteries). Heart rate variability (HRV) studies have shown that patients with syndrome X have an imbalance in autonomic nervous system activity (sympathetic predominance). However, it is not known if transient ST-segment depression which occurs in syndrome X during daily activities is related to this autonomic nervous system dysfunction. This study investigates the relation between the response of the autonomic nervous system, as assessed by HRV analysis, and the occurrence of transient ST-segment depression during 24-hour ambulatory electrocardiographic monitoring in 23 patients (4 men and 19 women, mean age 55 ± 6 years) with syndrome X. The frequency-domain variables of HRV low-frequency (0.04 to 0.15 Hz) and high-frequency (0.15 to 0.40 Hz) power were measured at 6-minute intervals during the 30 minutes preceding the onset of transient ST-segment depression. Fourteen patients (61%) had ≥1 episode of ST-segment depression in the 24 hours, whereas the remaining 9 patients (39%) had no significant ST-segment change. HRV measures differed according to whether or not ST-segment depression was associated with increased heart rate. Episodes of ST-segment depression associated with increased heart rate were preceded by a reduction of high-frequency power and an increase in the low-frequency-high-frequency ratio, whereas episodes of ST-segment depression not associated with increased heart rate showed no significant HRV changes. Low-frequency power remained unchanged irrespective of heart rate. Thus, in patients with syndrome X, a sympathovagal imbalance (sympathetic predominance due to vagal tone withdrawal) precedes episodes of ST-segment depression that are associated with an increased heart rate.

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.

921-71 Transcatheter Coil Embolization of Congenital Coronary Artery Fistulae

We describe our experience with nonsurgical closure of coronary artery fistulae (CAF) using a transcatheter approach and Gianturco coils. Since 7/92 6 patients (pts) age 9 to 22 years (mean = 14.5) were referred for evaluation and treatment of CAF. Two were symptomatic with chest pain and a third had dyspnea on exertion. Catheterization was performed from the femoral region using IV sedation in 5, and general anesthesia in 1. Selective coronary angiograms were performed in all pts followed by hand or power injections within the fistulas themselves. Angled views were employed to detail fistula anatomy as well as to visualize coronary artery branches. Catheters were manipulated into each fistula from a retrograde aortic approach. Temporary balloon occlusion of the fistula with EKG monitoring was performed in 5. Coils were placed through an end hole catheter positioned distally within the fistula. Each pt had asingle fistula. Two CAF arose from the LAD: 1drained into the RV and 1 into the RA. One CAF arose from the circumflex artery and drained into the RV. Three CAF arose from the RCA: 2 drained into the RA and 1 into the RV. Temporary balloon occlusion in one pt resulted in significant ST segment changes and aided in the identification of the origin of the posterior descending artery adjacent to the fistulous connection to the RV. Coil embolization was not attempted in this pt. The remaining 5 pts underwent successful complete occlusion of the CAF using multiple (2 to 16) Gianturco coils. There were 2 coil embolizations to the pulmonary artery with successful retrieval of 1. At follow-up (1-15 months, mean = 11) all pts are asymptomatic with no clinical or echocardiographic evidence of recanalization or residual shunts. Transcatheter closure is the preferred method to safely and effectively close most CAF.

Beta-adrenergic stimulation induces ST-segment elevation in dogs with healing myocardial infarction.

There is controversy with regard to the mechanism of the exercise-induced ST-segment elevation in myocardial infarction. The purpose of the present study was to investigate the mechanism of ST-segment elevation through pharmacologic interventions. Transmural anterior myocardial infarction was produced by gelatin sponge embolization of the left anterior descending artery in seven closed-chest dogs. One and four weeks after myocardial infarction, the dogs underwent the following three interventions: right atrial pacing, norepinephrine infusion (3.75, 7.5, and 15 micrograms/min) with the pacing, and methoxamine injection (2.5 and 5.0 mg) with the pacing. All dogs had transmural infarction with a mean infarct size of 12.0 +/- 4.2% of the left ventricular weight. Right atrial pacing did not induce significant changes in ST-segment. Norepinephrine induced a marked elevation of ST-segment at leads V1 to V4, while methoxamine did not. Norepinephrine induced a significant increase in left ventricular ejection fraction, while methoxamine produced a marked decrease in the ejection fraction and an increase in ventricular volume. The mean percent radial shortening of the non-infarct ventricular wall showed a significant increase with norepinephrine, but a decrease with methoxamine. In conclusion, myocardial ischemia and wall motion abnormality may be excluded as possible mechanisms of ST-segment elevation and an enhanced beta-adrenergic mechanism in the non-infarct myocardium is suggested to be responsible for ST-segment elevation.

Comparison of exercise echocardiography with an exercise score to diagnose coronary artery disease in women

This study compares the accuracy of the routine exercise electrocardiogram, exercise score, and exercise echocardiography for the diagnosis of coronary artery disease (CAD) in women. Seventy women with a pretest probability of 53 ± 30% for CAD were stressed using a maximal symptom-limited bicycle exercise protocol. Significant ST-segment change was defined by a depression of >0.1 mV 0.06 second after the J point. The exercise score was calculated from ST response, heart rate, and workload using an equation derived from a multivariate model. A positive stress echocardiogram was defined by development of a new or worsening wall motion abnormality. The results were compared with the presence or absence of significant (>50% diameter) stenoses at angography. Exercise echocardiography identified 29 of the 33 patients (88%) with CAD, compared with 22 (67%) using ST analysis alone, and 20 (61%) using the exercise score (both p <0.05 vs exercise echocardiography). The specificity of exercise echocardiography (84%) and the multivariate score (73%) were comparable, and exceeded that of the ST analysis (51%) in 37 patients without CAD (p <0.01). The accuracy of exercise echocardiography (86%) exceeded that of the exercise score (67%, p = 0.01) and ST analysis (59%, p <0.01). Among all 70 patients, an intermediate (20% to 80%) probability of coronary disease was identified in 21 patients on the basis of exercise echocardiography, in 38 based on the multivariate score, and in 38 based on the ST analysis alone. Exercise echocardiography is more sensitive than the exercise score, and more sensitive and specific than ST-segment analysis for the diagnosis of CAD in women. Moreover, exercise echocardiography is more effective than either of the other tests for classifying patients into groups at high and low probability of CAD.

Iomeprol and iopamidol in cardiac angiography: a randomised, double-blind, parallel-group comparison

During cardiac angiography, hemodynamic alterations and surface electrocardiographic changes are common, predictable and dose-related adverse reactions to radiocontrast media. High osmolality, inadequate sodium content and local transient hypocalcemia are thought to be the main mechanisms responsible for these untoward cardiovascular effects. The purpose of this double-blind, parallel-group trial was to compare the hemodynamic and electrocardiographic responses to cardiac and selective coronary artery injection of iomeprol 400 (400 mgI/ml) and iopamidol 370 (370 mgI/ml). One-hundred consenting adult inpatients were randomised to receive iomeprol 400 (41 males, nine females; mean age, 56.6 years) or iopamidol 370 (46 males, four females; mean age, 57.6 years). Both agents produced minor and transient hemodynamic and electrophysiological effects. Following left ventriculography, iopamidol 370 produced a significantly greater increase in LVEDP than iomeprol 400 (mean increases after first and second left ventriculogram: 2.5 and 4.6 mmHg with iomeprol 400, 3.3 and 9.9 mmHg with iopamidol 370, P = 0.027). The QT-interval was more affected by iopamidol 370 than by iomeprol 400. However, post-contrast prolongation of the QT-interval was not significant with either agent, nor were there any significant T-wave, ST-segment or RR-interval changes associated with the injection of the test compounds. No serious adverse events occurred throughout the study. Mild pain was complained by only one patient, while most patients reported mild to moderate sensation of heat. Image quality of the vast majority of the procedures was rated as good or excellent in both patient groups. It is concluded that both iomeprol 400 and iopamidol 370 are safe, well tolerated and effective contrast media when used for cardiac angiography. Iomeprol 400 might produce less hemodynamic disturbance than iopamidol 370. Larger trials on iomeprol in cardiac angiography are warranted.

Magnetocardiography and exercise testing

Twenty healthy male subjects (age range, 15–25 years; median, 21 years) underwent magnetocardiography during physical exercise. Significant ST-segment displacements of the magnetic signal were found during exercise at a heart rate of 120 beats/min compared to the magnetic signal at rest ( P < .001). Since no significant ST-segment changes were found in the electrocardiogram recorded simultaneously with the magnetocardiogram, it is concluded that the magnetocardiogram shows junctional ST-T segment changes earlier than the electrocardiogram.

Noninvasive assessment of reperfusion and reocclusion after thrombolysis in acute myocardial infarction

The clinical significance of ST-segment changes and of the time course of appearance in serum of different cardiac proteins has been reviewed for the diagnosis of coronary reperfusion and reoclusion after thrombolysis. In particular, the value of serial 12-lead electrocardiographic (ECG) studies, of Holter monitoring, and of continuous multilead computer-assisted ECG monitoring is compared. Regarding the serum proteins, the clinical significance of reperfusion indices described so far for serum creatine kinase (CK), its isoenzyme serum creatine kinase MB, the CK isoforms, and myoglobin is reviewed. Emphasis is placed on (1) the calculation method used for deriving the reperfusion indices; (2) the sensitivity and the specificity of the reperfusion indices; (3) the minimum turn-around time needed to produce the reperfusion indices (depending on the practicability of the analytical and calculation methods and their applicability in an emergency laboratory); (4) the ability of the indices to produce reliable estimates of reperfusion efficacy of the thrombolytic agents under study; and (5) the ability of the marker proteins to detect reinfarction as well as the suitability of the markers to detect real-time necrosis.

Influence of platelet size before coronary angioplasty on subsequent restenosis

Platelet size has been shown to reflect platelet activity. We prospectively measured the mean platelet volume (MPV) in 47 patients undergoing single vessel angioplasty for symptomatic angina. The patients underwent repeat angiography 4-8 months later irrespective of symptomatic status. Restenosis was assessed quantitatively by hand held calliper measurements of the lesion and qualitatively by a return of angina, ST segment changes on an exercise test and visual analysis of the lesion severity by two experienced angiographers. Twenty-four patients developed recurrent angina during the follow-up period, the MPV in the group with chest pain was 8.54 +/- 0.60 fl compared to 8.1 +/- 0.69 fl in the asymptomatic group (P = 0.04). Twenty two patients had significant ST segment changes at exercise. In this group the MPV was 8.6 +/- 0.56 fl compared to 8.0 +/- 0.70 fl for the group with a negative test (P = 0.002). Similarly visually assessed angiographic stenosis showed a significant increase in the restenotic group (8.6 +/- 0.56 vs. 8.0 +/- 0.61 fl, P = 0.001). The relative odds for developing clinically defined restenosis were 10.2 times greater if the pre-procedural MPV lay in the upper compared to the lowest quartile. There was a positive correlation between MPV and change in minimal luminal diameter between post angioplasty and follow-up angiography, assessed quantitatively, r = +0.56, P = 0.016. There was no association between clinical or angiographic definitions of restenosis and haemoglobin, red cell count, mean corpuscular volume, white cell count or platelet count. Platelet size may influence the development of restenosis after successful coronary angioplasty.

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 electrocardiographie (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 mullivariate 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.

PERIOPERATIVE CONTINUOUS MONITORING OF ST-SEGMENT CHANGES IN PATIENTS UNDERGOING ELECTIVE CAESAREAN SECTION

Using continuous ambulatory electrocardiography, we have investigated the incidence of ST-segment changes occurring in patients undergoing elective Caesarean section under extradural, spinal or general anaesthesia. There was no evidence of significant perioperative ST-segment changes. The findings contrast with the results of other work published recently.

The incidence of cardiac events in Japanese men with atypical or nonanginal chest pain: A prospective study on the significance of exercise testing

The incidence of cardiac events in Japanese men (mean age 54 ± 10 years) with atypical or nonanginal chest pain was assessed prospectively. Three groups of patients, those with typical angina (TA; n = 134), those with atypical angina (AA; n = 192), and those with nonanginal chest pain (NA; n = 311) were studied with regard to cardiac events (cardiac death or nonfatal myocardial infarction), risk factors, and results of exercise testing. The total cholesterol and high-density lipoprotein-cholesterol levels were significantly different among the three groups, but no differences were observed for other risk factors. The incidences of cardiac events were 8.5%, 2.2%, and 1.3% in the TA, AA, and NA groups, respectively ( p < 0.05) during 3.2 ± 1.5 years. Significant ST segment changes were observed in 70.1%, 25.5%, and 18.0% of the patients in the TA, AA, and NA groups, respectively, at the time of enroliment. The risk ratio for cardiac events in a positive exercise test was 1.7 (difference not significant) for the TA group and 6.1 ( p < 0.05) for the others combined (AA and NA groups). The risk ratio adjusted for risk factors (Cox model) was 2.2 (difference not significant) for the TA group and 4.9 ( p < 0.05) for the AA and NA groups combined. In conclusion, the incidence of cardiac events in those with AA or NA chest pain was relatively low in Japan, but the independent prognostic significance of positive exercise testing was demonstrated in this group of patients.

Physiologic Demands of Prolonged Cardiopulmonary Resuscitation Performance by Physically Conditioned Patients With Cardiac Disease

Thirteen men with cardiac disease who were 37 to 71 years of age (mean, 58 years of age) and who had been aerobically conditioned for at least 6 weeks in a cardiac rehabilitation program were studied to determine whether they could safely perform 10 minutes of sustained cardiopulmonary resuscitation (CPR). Hemodynamic, metabolic, and electrocardiographic (ECG) changes were observed during 10 minutes of single-person CPR (compression and ventilatory phases) to determine if sign /symptomatic response occurred and the exertional effort the responses required. No subjects had serious arrhythmias or significant ST segment changes during CPR performance that were not apparent during exercise training. The highest mean energy cost was 11.4 mL · Kg-1 · min-1 (3.26 METS), measured at minute 6 of CPR performance. Heart rate (HR) peaked at minute 5 (32 beats per minute above resting values), and the rate-pressure product (RPP) increased progressively during CPR performance, achieving an increase of 47 units at minute 10. These responses were within normally prescribed exercise limits and indicated that these selected patients could safely perform prolonged CPR.

Significance of ST segment changes induced by dobutamine stress test after acute myocardial infarction. Which are reciprocal?

In order to determine the significance of predischarge stress-induced ST segment changes after a first non-complicated acute myocardial infarction, a dobutamine stress test was performed in 104 patients. Dobutamine was infused in doses of 5, 10, 15 and 20 micrograms.kg-1.min-1 every 5 min with ECG and blood pressure control. It induced a substantial increase in heart rate and systolic blood pressure. The patients were divided into 4 groups: (1) anterior (n = 28); (2) inferior (n = 32); (3) posteroinferior (n = 27) and (4) high lateral plus anterior or anterolateral (n = 17) infarction. They were followed for 2 to 18 months (mean 7.5 +/- 5). In basal conditions the ST segment was elevated in 49 patients and depressed in 20. Combined ST elevation and depression was seen in 11. After dobutamine there was ST elevation in 80 patients, depression in 71 and combined elevation and depression in 60. The magnitude of the maximal ST elevation was correlated with the magnitude of the maximal ST depression in each group of patients. There was a good inverse linear correlation between ST segment shifts in inferior vs high lateral leads, and ST depression was considered as a benign mirror image of opposite ST elevation in such leads. In patients with posterior infarction, anterior ST depression was considered as a mirror image of posterior ST elevation. In the remaining cases ST depression was a criterion of positivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Therapeutic implications of dynamic coronary stenosis in patients with single vessel coronary artery disease

Ten patients with proven single-vessel coronary artery disease and a positive exercise test for ischaemia were investigated to establish the importance and therapeutic implications of dynamic coronary stenosis in such patients. All patients interrupted their anti-anginal therapy and under took serial exercise testing in an attempt to identify variability in the ischaemic threshold. Ergonovine testing was performed in nine patients and all underwent 48 h of ambulatory ST segment monitoring while treatment was discontinued. Patients then entered a randomized double-blind study of atenolol and nifedipine; treadmill exercise testing and 48 h of ambulatory ST segment monitoring were performed at the end of each treatment phase. Six (60%) patients showed evidence of variability in coronary vasomotor tone four of whom developed significant ST segment changes during administration of ergonovine; a further two had greater than 30% variability in time to onset of ischaemia during serial treadmill exercise testing. Atenolol significantly increased the time to ischaemia on exercise testing, both in the group as a whole and in the subgroup with evidence of altered vasomotor tone when compared with no therapy, and led to a non-significant reduction in the frequency and duration of ischaemia during the patients' daily lives. Nifedipine, conversely, did not significantly increase time to ischaemia on exercise testing or reduce the frequency or duration of ambulatory ischaemia in either the whole group or the subgroup. With evidence of altered vasomotor tone when compared to no therapy however it was beneficial in terms of reduction in chest pain and requirement for glyceryl trinitrate during daily life.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of low osmolality ionic (ioxaglate) versus nonionic (iopamidol) contrast media in cardiac angiography

A double-blind randomized study was performed in 60 patients to compare the electrocardiographic and hemodynamic changes induced during cardiac angiography by 2 contrast media with relatively low osmolality. Ioxaglate meglumine sodium, an ionic dimer contrast medium, was compared with iopamidol, a nonionic compound. Of the 30 patients who received ioxaglate, 13 (43%) experienced a mild to moderate adverse reaction to the contrast media, while only 2 of the 30 patients (7%) in the iopamidol group had similar side effects (p <0.005). Significant prolongations of the QT intervals occurred with the ioxaglate injections. The QT intervals increased from 402 ± 46 to 442 ± 59 ms (p < 0.001) with the right coronary artery injection and similar changes were observed after the left coronary artery injection and left ventriculography. Significant ST-segment and T-wave amplitude changes also occurred in the ioxaglate group. With iopamidol injections, there were no significant changes in any of these parameters. After the left ventriculogram, there were similar decreases in the systolic arterial pressures in both groups (−14 ± 10 mm Hg with ioxaglate and −21 ± 9 mm Hg with iopamidol). The left ventricular end-diastolic pressures increased after the ventriculogram in both groups (5 ± 5 vs 2 ± 3 mm Hg with ioxaglate and iopamidol, respectively, 60 seconds after the injection). This report demonstrates that mild to moderate adverse reactions, QT-interval prolongations, ST and T-wave changes were significantly greater during coronary angiography with ioxagiate when compared with iopamidol. Thus, despite similar osmolalities, the nonionic contrast medium (iopamidol) appears to be better tolerated than the ionic dimer (ioxaglate) during coronary angiography.

Silent myocardial ischaemia in chronic stable angina: a study of its frequency and characteristics in 150 patients.

One hundred and fifty unselected patients with documented coronary artery disease were studied to establish the frequency and characteristics of silent myocardial ischaemia. Patients underwent ambulatory ST segment monitoring off all routine antianginal treatment (total 6264 hours) and exercise testing (n = 146). Ninety one patients (61%) had a total of 598 episodes of significant ST segment change, of which 446 (75%) were asymptomatic. Twenty seven patients (18%) had only painless episodes; 14 (9%) patients only painful episodes; 50 patients (33%) had both painless and painful episodes. The mean number of ST segment changes per day was 2.58 (1.95 silent); however, 11 patients (7%) had 50% of all silent episodes, and 48 patients (32%) had 91% of all silent episodes. Fifty nine patients (39%) had no ST segment changes on ambulatory monitoring, and 73 patients (49%) had no evidence of silent ischaemia. Episodes of silent ischaemia occurred with a similar circadian distribution to that of painful ischaemia, predominantly between 0730 and 1930. There was a similar mean rise in heart rate at the onset of both silent and painful episodes of ischaemia. Silent ischaemia was significantly more frequent in patients with three vessel disease than in those with single vessel disease, and was also significantly related to both time to 1 mm ST depression and maximal exercise duration on exercise testing. There was a highly significant relation between the mean number and duration of episodes of silent ischaemia in patients with positive exercise tests when compared with those with negative tests. No episode of ventricular tachycardia was recorded in association with silent ischaemic change.

Systemic alkalosis as a provocative test for coronary artery spasm in patients with infrequent resting chest pain

Systemic alkalosis was used to detect coronary spasm in 237 patients with infrequent, resting, angina-compatible chest pain. The provocative test was performed without previous coronary arteriography but only in patients with negative submaximal exercise test results. Rapid infusion of alkaline solution followed by maximal hyperventilation raised arterial pH above the 7.65 value necessary for diagnostic significance in 196 (83%) patients. In 24 (12%) of these patients the provocative test induced significant ischemic ST segment changes. In all patients with a positive response, coronary artery disease, which was predominantly vasospastic (19 patients) or atheromatous with a vasospastic contribution (five patients), was demonstrated by coronary arteriography followed, if necessary, by ergot derivative injection. Chest pain and ECG changes were always reversed within 5 minutes by intravenous nitroglycerin. Coronary arteriography was not performed in all patients with a negative response; therefore, the sensitivity of the procedure could not be assessed. However, 36 patients with a negative response to hyperventilation underwent coronary arteriography; 33 (92%) had normal arteriograms and a negative response to ergot derivatives. Hyperventilation appears to be a safe and specific diagnostic procedure in a subset of patients in whom the probability of coronary artery disease may not be judged sufficient to warrant coronary arteriography as a primary diagnostic approach.