Asymptomatic myocardial ischemia in patients with stable and typical angina pectoris

The sensitivity of the symptom angina pectoris as a marker of transient myocardial ischaemia in chronic stable angina pectoris

Therapeutic decisions in patients with angina pectoris are traditionally based on the history reported by the patient, since objective evidence of myocardial ischaemia during daily life is often not available. In this study, ambulatory ST segment monitoring was performed in 60 patients with a history of chronic stable angina pectoris, positive exercise test and/or positive coronary angiography, and a correlation was made between the episodes of chest pain and ST segment change. The patients were grouped according to the results of exercise testing and coronary arteriography, and one group was studied with and without antianginal medication. Overall, 195 episodes of angina were noted, only 94 of which (48%) were accompanied by ST segment depression. Pain and ST segment changes were best correlated in patients with a positive exercise test, positive angiography and who were not receiving antianginal medication. In 101 episodes of chest pain, ST segment change could not be identified; in 18 (18%) there was sinus tachycardia, in 12 (12%) ventricular premature beats, and in 71 (70%) sinus rhythm solely. Thus, anginal pain appears not to be the reliable indicator of transient myocardial ischaemia as was previously thought, a finding which supports the use of objective methods in identifying episodes of transient myocardial ischaemia in daily life.

Transient myocardial ischemia after abrupt withdrawal of antianginal therapy in chronic stable angina

In 47 patients with chronic stable angina and proven coronary artery disease, abrupt withdrawal of beta-adrenoceptor blocking agents either as monotherapy or in combination with calcium antagonists (group 1, n = 25) was compared with abrupt withdrawal of calcium antagonist monotherapy (group 2, n = 22) as regards the occurrence of cardiac events and total ischemic activity detected by ambulatory monitoring. Reinstitution of medical therapy was required in 6 patients (4 in group 1 and 2 in group 2). Ambulatory monitoring was initiated for 36 hours on 3 occasions: before withdrawal, and again 2 and 5 days after withdrawal. The first 2 monitorings were performed in the hospital and the last during daily activity. In group 1, the frequency of total ischemia increased by 64 and 148% from monitoring occasions 1 to 2 and 1 to 3, respectively (p less than 0.01), and silent ischemia increased by 100 and 129%, respectively (p less than 0.01). However, no significant change in transient myocardial ischemia was noted in group 2. Heart rate at onset of ischemia increased significantly in group 1 (p less than 0.01), in contrast to group 2 which had significant increases only in out-of-hospital values (p less than 0.05). These results indicate that a rebound increase in ischemic activity (mainly silent) occurs after abrupt withdrawal of beta-receptor blockade in patients with chronic stable angina. This increase in ischemic activity may be caused by increased myocardial oxygen demand.

Effects of long-term treatment with 120 mg of sustained-release isosorbide dinitrate and 60 mg of sustained-release nifedipine on myocardial perfusion

Forty patients with coronary artery disease and scintigraphically proven myocardial ischemia were randomized into 2 groups receiving 4 weeks of treatment with either 120 mg of isosorbide dinitrate (ISDN) release or 60 mg of nifedipine release. Control exercise testing and myocardial scintigraphy were continued until anginal pains occurred, and repeated at identical individual workloads at the end of the 4 weeks of drug therapy. Myocardial scintigrams were evaluated by quantitative recording of counts in 60 segments/frame. Twenty patients in the ISDN group (group I) exhibited 47 significantly ischemic areas. The remaining 20 patients (group II), treated with nifedipine, had 50 ischemic areas before therapy. In the ischemic areas in group I, there was a mean difference of 30.9% between counts at rest and during exercise in the pretreatment period, and a difference of 18.1% after therapy (39.0%). In group II, the pretreatment difference was 28.8%, decreasing to 20.6% after therapy (17.8%). Both groups of patients were subsequently subdivided into 3 subsets: (1) significantly improved perfusion, (2) significant worsening, and (3) unchanged myocardial perfusion. Group I had 59.5% of areas with significant improvement and 10.6% of areas with significant worsening. In 29.7% of the areas, the findings were unchanged. Group II had improvement in 40% of areas, of significantly worsened areas in 6%, and unchanged areas in 54%, in both groups myocardial ischemia was reduced by therapy, but ISDN improved myocardial perfusion to a considerably greater extent than did nifedipine.

Role of nitrates in silent myocardial ischemia

Assessment of systemic and coronary hemodynamics, myocardial metabolic and mechanical function and scintigraphic and electrocardiographic studies has provided ample evidence for the existence of asymptomatic silent myocardial ischemia in both acute and chronic coronary artery syndromes. There is growing evidence to suggest that a primary decrease in coronary blood flow, resulting from increased coronary arterial resistance, is the principal cause for spontaneous symptomatic and asymptomatic myocardial ischemia in these patients. The precise mechanism for increased coronary arterial resistance has not been clarified, and it is likely to be different in different angina syndromes but similar for both symptomatic and asymptomatic myocardial ischemia. Since nitroglycerin and nitrates can decrease coronary arterial tone and coronary artery resistance, as well as myocardial oxygen requirements, these agents have the potential to relieve episodes of silent myocardial ischemia in patients with coronary artery syndromes.

Holter monitoring before, during and after percutaneous transluminal coronary angioplasty for evaluation of high-resolution trend recordings of leads CM5 and CC5 for ST-segment analysis

Frequency-modulated Holter monitoring of leads CM5 and CC5 was performed before, during and after percutaneous transluminal coronary angioplasty (PTCA) in 16 patients with stenosis of the left anterior descending coronary artery, in 5 patients with stenosis of the left circumflex coronary artery, and in 5 patients with stenosis of the right coronary artery. All patients presented with 1-vessel coronary artery disease and stable or unstable angina pectoris. ST-segment analysis was based on high-resolution trend recordings. During balloon inflations all patients had significant (at least 0.1 mV) ST-segment changes in lead CM5. In lead CC5, associated ST-segment deviations were found in 22 of 26 patients. During 29.2 +/- 13.6 hours before PTCA, 90 spontaneous episodes with significant ST-segment deviations were detected in 10 patients. Of these episodes, 17% were characterized by ST-segment deviations in lead CC5 only, 57% by ST-segment deviations in lead CM5 only, and 27% by simultaneous ST-segment deviations in both leads. Asymptomatic episodes occurred twice as frequently as symptomatic episodes (66 vs 34%). Symptomatic episodes were more often characterized by ST-segment deviations of at least 0.15 mV (48 vs 9%, p less than 0.001) and by ST-segment deviations observed in both leads simultaneously (48 vs 15%, p less than 0.001). During 34.8 +/- 10.6 hours after successful PTCA, 5 spontaneous asymptomatic episodes with significant ST-segment deviations were detected in 2 patients.

Prognostic significance of silent myocardial ischemia in patients with unstable angina

Silent myocardial ischemia is common in unstable angina, but its prognostic significance is unknown. Fifty-two (42 with subsequent angiography) of 81 patients prospectively evaluated for unstable angina had ambulatory electrocardiographic (Holter) recordings analyzed by compact analog technique after they had received medical treatment (3 of the 52 had unanalyzable recordings and were excluded). From 1,103 hours of recordings, 298 ischemic episodes were identified, only 9% associated with angina. By Ridit analysis a significant correlation was found between the cumulative duration of transient myocardial ischemia and the number of diseased coronary vessels and indexes of proximal stenosis. During a 3 to 6 month follow-up period, there was one death and one patient was lost to follow-up among 20 patients without transient ischemia; in the group of 11 patients with a cumulative duration of transient ischemia less than 60 minutes/24 h, 7 were alive and well, 2 required coronary bypass surgery, 1 had coronary angioplasty for recurrence of angina and 1 was lost to follow-up. In the group of 18 patients with ischemia duration greater than 60 minutes/24 h, only 1 developed a stable angina pattern; 12 required coronary surgery (n = 11) or angioplasty (n = 1) and 5 developed myocardial infarction (2 died, 2 needed surgery for postinfarction angina and 1 recovered). A favorable clinical outcome occurred in only 6% of patients in the group with ischemia duration greater than 60 minutes/24 h; this rate was significantly lower (p less than 0.001) than that (70%) for the group with ischemia duration less than 60 minutes/24 h or that (95%) for the group without ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Characteristics and clinical significance of silent myocardial ischemia in unstable angina

The frequency and duration of transient myocardial ischemia on Holter recordings, analyzed by the compact analog technique, were determined in 41 patients (all men, mean age 54) with unstable angina (33 with angiographic evidence). There were 781 episodes of ischemia: 392 (50%) with ST-segment depression, 242 (31%) with ST elevation, 45 (6%) with ST elevation and depression in different leads, 70 (9%) with pseudonormalization of T waves and 32 (4%) with T-wave augmentation. Ventricular arrhythmias were associated with 18% of the episodes. The mean duration of ischemic episodes was 14 minutes (range 30 seconds to almost 12 hours); most were less than 5 minutes. Only 154 (20%) of the 781 episodes of ischemia were associated with pain. Conversely, 77 episodes of chest pain were not associated with electrocardiographic changes. Analysis of the temporal sequence of heart rate during the development of ischemia (analyzed in 415 episodes) showed that in only 43 (10%) the heart rate at the beginning of ischemia was significantly (greater than 6 beats/min) higher than that at 5 minutes (baseline) before the onset of ischemia. At the peak of the ischemic abnormality, the mean heart rate increase was 10% and returned to baseline at the end of the ischemic episode. The data indicate that 80% of ischemic episodes in unstable angina are silent and over 90% are not triggered by increases in heart rate; apparently increased oxygen demand is an uncommon cause of ischemia in unstable angina. Although most of the episodes were short-lived, some were extremely protracted without the development of myocardial infarction. The findings are of therapeutic significance.

Hemodynamic and electrocardiographic correlates of symptomatic and silent myocardial ischemia: pathophysiologic and therapeutic implications

Numerous hemodynamic, electrocardiographic, metabolic and radionuclide measurements in various subsets of patients with coronary artery disease (CAD) reveal that ischemia does not always occur on the basis of increases in myocardial oxygen consumption. Continuous hemodynamic monitoring indicates that most episodes of myocardial ischemia are not preceded by increases in such major determinants of oxygen consumption as heart rate or blood pressure, but that these usually increase in response to the development of ischemia. The development of pain during ischemia is a late feature and most episodes are silent. There are no significant differences in the hemodynamic characteristics of symptomatic versus asymptomatic episodes of myocardial ischemia in patients with angina at rest or between those associated with ST-segment depression and those with ST-segment elevation. Continuous Holter recordings analyzed by compact analog technique in hospitalized and ambulatory patients with ischemic heart disease indicate that in both unstable and chronic stable angina, over two-thirds of myocardial ischemic episodes are clinically silent. Symptomatic and silent episodes do not differ significantly with respect to duration. Most symptomatic and asymptomatic episodes are not triggered by increases in the determinants of oxygen demand. Such episodes may arise on the basis of a critical reduction in the lumen of the diseased coronary artery leading to a primary reduction in blood flow. Intermittent obstruction due to changes in coronary vasomobility or possibly formation of thrombi may be a common mechanism for the pathogenesis of myocardial ischemia in patients with a varying spectrum of coronary artery lesions. At present, the precise clinical and prognostic significance of silent ischemia in CAD is not completely defined.(ABSTRACT TRUNCATED AT 250 WORDS)

Character of transient ischemia in angina pectoris

There is growing interest in the possible therapeutic and prognostic significance of silent myocardial ischemia in coronary artery disease (CAD) and its detection by ambulatory electrocardiographic (ECG) monitoring. In 100 apparently healthy normal subjects (20 with angiographically normal coronary arteries), Holter monitoring revealed significant ST-segment depression in only 2 (both over 40 years, one with positive treadmill test, the other with risk factor for CAD). No significant ECG changes were found in those with normal coronary vessels. In 30 patients with documented CAD, significant ST-segment depression during 1,934 episodes over 446 days of monitoring over 18 months was found. Only 24% of the episodes were associated with angina. Asymptomatic and symptomatic episodes were associated with comparable changes in perfusion detected by positron emission tomography. Heart rate increases greater than 10 beats/min preceding the onset of the ST-segment changes occurred in only 23% of the episodes. There was considerable variability in the ST-segment changes in the same patient monitored serially over long periods of time. The data indicate that it is extremely uncommon for patients without CAD to exhibit silent myocardial ischemia, whereas patients with stable angina exhibit frequent, variable and often asymptomatic ECG evidence of myocardial ischemia rarely triggered by increases in heart rate. These findings are likely to be of therapeutic and prognostic significance.

Mechanisms and therapy of silent myocardial ischemia and the effect of transdermal nitroglycerin

Studies of the mechanisms and characteristics of ischemic heart disease have increasingly documented evidence of myocardial ischemia in the absence of symptoms. Recent work using objective criteria of ischemic events has confirmed that angina pectoris or its equivalents need not accompany true myocardial ischemia, and this appears to be quite common. The impact of these findings on prognosis awaits further study, but preliminary data suggest an improved prognosis for persons in whom coronary artery disease remains asymptomatic compared with symptomatic patients. Further, reduction of silent ischemic events with nitrate therapy may be associated with a more benign subsequent course. Preliminary trials show a reduction of the number, duration and magnitude of silent ischemic events by transdermal nitroglycerin. Ongoing technical innovations in monitoring systems should allow more complete characterization of this syndrome and lead to definition of medical therapy for it.

Incidence of complex ventricular arrhythmias in asymptomatic patients with recent myocardial infarction

The incidence of ventricular extrasystoles (VES) was documented in 50 patients with recent uncomplicated myocardial infarction, with a 72-h two-channel ambulatory electrocardiogram. All patients were free of symptoms of arrhythmias; unstable angina pectoris and heart failure were absent. A total of 82% of the patients had VES: 23/50 patients had multiform or complex VES, 8/50 patients had ventricular tachycardia. VES were independent of heart rate and stable angina pectoris. Thus, frequent and complex VES are common in asymptomatic patients with uncomplicated recent myocardial infarction. Even in the absence of symptoms, ambulatory electrocardiography is useful. The prognostic significance of asymptomatic complex VES in these patients remains unsettled.