Prevalence and functional significance of transient ST-segment depression during daily life activity: comparisons of ambulatory ECG with stress redistribution thallium 201 single-photon emission computed tomographic imaging

Correlation of ST-segment depression during ambulatory electrocardiographic monitoring with myocardial perfusion and left ventricular function

To assess the relation between silent ischemia and objective markers of ischemia we compared ambulatory electrocardiographic (AECG) monitoring, exercise stress testing, and technetium-99m methoxyisobutyl isonitrile single-photon emission computed tomography (SPECT) in 68 patients with coronary artery disease. ST-segment depression at AECG monitoring occurred in 40%, exercise testing was positive in 88%, and SPECT was abnormal in 98% of patients. Patients with ST-segment depression had a higher incidence of 3-vessel disease (70% vs 45%, p = 0.04), shorter duration of exercise (267 +/- 109 vs 416 +/- 167 seconds, p < 0.01), lower workload achieved (5.1 +/- 1.9 vs 7.6 +/- 2.8 METs, p < 0.0002), and a greater extent of ischemia at scintigraphy (p = 0.01). Patients with a total ischemic time of >30 minutes in a 24-hour period had a lower ejection fraction (48 +/- 21% vs 70 +/- 9%, p = 0.001), a higher perfusion index at rest (2.4 +/- 0.6 vs 1.6 +/- 0.6, p = 0.001), and a greater number of segments with fixed perfusion defects (4.1 +/- 3.7 vs 1.3 +/- 1.8, p = 0.02) in comparison with those who had a shorter ischemic time. We conclude that AECG monitoring fails to identify a substantial proportion of patients with objective markers of ischemia; however, ST-segment depression reflects more significant disease. Longer total ischemic time correlates with the area of myocardial damage but not with other markers of ischemia.

Light versus heavy sedation after cardiac surgery: myocardial ischemia and the stress response. Maritime Heart Centre and Dalhousie University

The influence of light versus heavy sedation after coronary artery bypass graft (CABG) surgery on the development of postoperative myocardial ischemia has not been described. After uncomplicated CABG surgery, 50 patients were randomly assigned to receive LOW (n = 24; target Ramsay Sedation Score [RSS] = 2) or HIGH (n = 26; target RSS = 4) sedation with propofol. Analgesia was provided to maintain a visual analog scale (VAS) pain score <7. Myocardial ischemia was identified perioperatively using continuous 3-lead Holter monitoring. By measuring creatine kinase (CK) MB levels preoperatively, at entry to the intensive care unit (ICU), and every 12 h for 48 h; and by obtaining serial 12-lead electrocardiograms (ECG) (preoperatively; 2, 4, 12, 24, and 48 h after ICU admission, 8:00 AM the morning after surgery; and 5 min pre- and postextubation), myocardial infarction was identified. Endocrine stress response was assessed by measuring serum cortisol levels preoperatively, on admission to the ICU, and 24 h postoperatively. In a subset of patients (LOW n = 10, HIGH n = 11), plasma and urinary catecholamine levels were also measured. There were no between-group differences in demographics, operative course, hemodynamic variables, or cortisol levels while in the ICU. The VAS pain score and target RSS were achieved and sustained, and they differed between groups. There were three myocardial infarctions in each group by CKMB criteria alone. No ECG-identifiable myocardial infarction occurred. The ST segment versus time curve (LOW 187 +/- 295 versus HIGH 1071 +/- 2137 mm/min) differed between groups. Urinary and plasma catecholamine levels were similar between groups over the observation period. We conclude that the use of a reduced sedation regimen in combination with adequate analgesia did not result in an increased endocrine stress response or risk of myocardial ischemia.

IMPLICATIONS

This randomized study of patients after coronary artery bypass surgery examined whether light (versus heavy) sedation with propofol in the intensive care unit was associated with an increased degree of myocardial ischemia. Using techniques to detect myocardial ischemia, including Holter monitoring, electrocardiogram, and myocardial enzyme measurements, no differences were found. We conclude that light sedation does not increase the endocrine stress response or the risk of myocardial infarction.

Clinical implications of silent versus symptomatic exercise-induced myocardial ischemia in patients with stable coronary disease

OBJECTIVES

This study was undertaken to better understand the functional and prognostic significance of silent relative to symptomatic ischemia.

BACKGROUND

Previous studies have reached conflicting conclusions as to whether painless ischemia identified during noninvasive cardiac testing is related to a lesser extent of myocardial ischemia or a different prognosis than ischemia accompanied by angina, or both.

METHODS

Nine hundred thirty-six clinically stable patients 1 to 6 months after an acute coronary event, either myocardial infarction or unstable angina, underwent ambulatory monitoring, exercise treadmill testing and stress thallium-201 scintigraphy. They were then followed up prospectively for a mean of 23 months for recurrent cardiac events (cardiac death, nonfatal myocardial infarction or unstable angina).

RESULTS

Compared with patients with symptomatic ischemia during testing (n = 125), those with silent ischemia (n = 378) demonstrated less severe and extensive reversible defects on stress thallium scintigraphy (p = 0.0008), less functional impairment during treadmill testing manifested by longer exercise duration (640 +/- 173 vs. 529 +/- 190 s, p = 0.002) and longer time to ST segment depression (530 +/- 215 vs. 419 +/- 205 s, p = 0.0001) and less frequent ST segment depression during ambulatory monitoring (9% vs. 19%, p = 0.005). Patients with symptomatic ischemia had a significantly (p = 0.004) increased number of subsequent recurrent cardiac events (28.8%) versus those with silent (18.0%) or no (17.3%) ischemia. Adverse outcomes were especially concentrated in the subgroup with symptomatic ischemia and poor exercise tolerance. The difference in cardiac event rates between patients with silent versus symptomatic ischemia persisted after adjustment for baseline clinical characteristics by Cox regression analysis.

CONCLUSIONS

Patients with painless ischemia during exercise testing 1 to 6 months after recovery from a coronary event have less jeopardized ischemic myocardium and fewer recurrent cardiac events than patients with symptomatic ischemia.

Pathophysiologic factors governing the variability of ischemic responses to treadmill and bicycle exercise

Ischemic responses may vary considerably when patients with coronary artery disease (CAD) are tested serially, but the pathophysiologic mechanisms that govern this variability have not been well evaluated. We thus evaluated whether clinical, hemodynamic, physiologic, and anatomic factors influenced the variability in ischemic responses among 140 patients (mean age 54 +/- 11 years) subjected to both bicycle and treadmill exercise electrocardiography. Radionuclide ventriculography was obtained during bicycle exercise in each patient. The population included 77 patients with CAD, 21 patients with normal coronary arteriograms, and 42 patients with < 5% likelihood of CAD. Bicycle exercise evoked higher systolic blood pressure (p < 0.001) and double-product (p < 0.001) responses compared with treadmill exercise in the patients with CAD and in the normal subjects, and it evoked a lower frequency of chest pain (12% vs 41%, p < 0.001) in the 34 patients with CAD who had ST-segment depression during both exercise tests. There was a high frequency of variability in ischemic responses during treadmill versus bicycle exercise: 22 (39%) of the 56 CAD patients who had exercise-induced ST-segment depression manifested this response during one stress test only. This variability was strongly related to the functional and anatomic magnitude of disease. Ischemic variability decreased progressively as the response of left ventricular ejection fraction (LVEF) to exercise worsened progressively (p = 0.003 by analysis of variance), from 83% in those with an LVEF increase of > 10% with exercise to only 13% in those with an LVEF fall of > or = 5% with exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Triggers of angina and ST-segment depression in ambulatory patients with coronary artery disease: evidence for an uncoupling of angina and ischemia

This study evaluated daily-life physical and mental triggers of painful and painless myocardial ischemia and of anginal pain in patients with coronary artery disease (CAD) by using ambulatory electrocardiographic monitoring and a structured diary. Eighty-five percent of ambulant ischemic episodes occurred without chest pain; 66% of anginal pain reports were made in the absence of ischemic ST-segment depression. Chest pain reports in the absence of ischemia could not be attributed to "borderline" ST-segment changes. Compared with silent ischemia, painful ischemia was triggered at higher levels of physical activity (p < 0.05) and at higher levels of self-rated effort and negative emotion (p < 0.05). Painful episodes were associated with greater-magnitude ST depression (p < 0.02), but a substantial percentage of episodes with > or = 2 mm and > or = 3 mm ST depression were silent. These results reveal an uncoupling of anginal symptoms from ambulatory ischemic episodes in patients with CAD during daily life. In addition, specific activities and emotions correlate with the presence or absence of anginal symptoms as much as does the presence of ischemic ST depression. These results may have implications for antiischemic and antianginal treatment strategies.

Is 'silent' myocardial ischemia really as severe as symptomatic ischemia? The analytical effect of patient selection biases

BACKGROUND

The clinical significance of exercise-induced chest pain remains controversial, as reflected by sharply discordant clinical results within the medical literature. Thus, we developed a prospective study to compare the functional significance of silent versus symptomatic ischemia and to evaluate whether patient selection biases influence this analysis.

METHODS AND RESULTS

We evaluated 117 patients (mean age, 63 +/- 9 years) with ischemic ST-segment depression during treadmill testing. Each patient underwent Tl-201 myocardial perfusion single-photon emission computed tomography (SPECT) after exercise followed by 24-ambulatory ECG monitoring. Patients were divided into silent versus symptomatic cohorts and were compared for the degree of hemodynamic, exercise and ambulatory ECG, and thallium abnormalities during stress testing. Analyses were repeated as the patient population became increasingly restricted. Compared with the silent patients, patients with chest pain during exercise had a shorter exercise duration (P < .009), lower peak heart rate (P = .009) and double product (P = .005), lower heart rate threshold for ST depression (P < .05), more episodes of ambulatory ST-segment depression (P < .05), a higher frequency of ischemia abnormalities during Tl-201 SPECT (P = .02), and higher summed Tl reversibility scores (P = .002). As the population became increasingly restricted, the relative magnitude of differences in silent versus symptomatic cohorts diminished, whereas the absolute magnitude of ischemic abnormalities progressively increased in both cohorts. For example, within the restricted group having ischemia on both exercise and ambulatory ECG, 50% of the silent cohort had severe ischemia on Tl SPECT (five or more reversible defects) and more than one third demonstrated the ominous finding of transient left ventricular dilation after exercise.

CONCLUSIONS

The induction of chest pain is associated with substantially more functional abnormalities when it is analyzed in a relatively "broad-spectrum" coronary artery disease population; by contrast, chest pain tends to lose its apparent value as a clinical test parameter when its analysis is restricted to coronary artery disease populations with a greater a priori likelihood of manifesting inducible ischemia. These findings may help resolve some of the previous discordant literature reports.