Prevalence of pseudoischemic ST-segment changes during ambulatory electrocardiographic monitoring

High incidence of ST-T changes in women during tilt-table testing

INTRODUCTION

We have observed electrocardiographic (ECG) changes primarily in women during tilt table testing.

METHODS

We reviewed 12 lead ECGs during tilt studies between 2012 and 2016 for changes in ST segments and T waves during tilt table testing. Patients with distinctly abnormal baseline ECGs were excluded.

RESULTS

Of the 180 tilt studies, 117 (65%) were in women. There were 32 patients with ECG changes during tilting. Of these, 28 (87.5%) were in women with an average age of 45years. None had a history of CAD or exertional chest pain. Echocardiograms were available in 21 of the 28 women with tilt induced ECG changes and all were normal. ECG changes during tilt table testing were found in 4/64 (6.25%) of men. The occurrence of ST-T wave changes during tilt testing was significantly higher among women compared to men, with a p value of 0.008. Of the 28 women with ECG changes during tilt, 11 had T wave inversions alone. ST segment depression alone was noted in 7 women. There were 10 women who had both ST segment depression and T wave inversions. Changes occurred immediately upon tilting in 6. In the remaining, they occurred at an average of 4.8±4min after tilting. The slight increase in heart rate in patients with ECG changes was similar to that in the patients without new ECG changes. The ECG changes were not related to the presence of syncope.

CONCLUSIONS

ECG changes during the testing was observed at a relatively high incidence primarily in women. The clinical significance of these repolarization changes during tilt testing is unknown. These ECG changes during tilt testing may correlate with the high incidence of false positive ECGs in women during exercise testing but do not necessarily indicate the presence of ischemic coronary disease. Additional research is needed to explain this phenomenon.

Pulse wave velocity is increased in patients with transient myocardial ischemia

OBJECTIVE

We have recently shown that mean pulse pressure is higher in patients with transient myocardial ischemia. Pulse pressure elevation might be an important consequence of increased arterial stiffness. The aim of this study was to prove if arterial stiffness is changed in patients with transient myocardial ischemia who bear a high cardiovascular risk. Additionally we investigated whether arterial stiffness or wave reflection is the best indicator for transient myocardial ischemia. Aortic pulse wave velocity (PWV) is a measure of arterial stiffness, and augmentation index (AIx) an indication of arterial wave reflection. Both are indicators for cardiovascular risk.

METHODS

PWV (carotid-femoral) and AIx (SphygmoCor) were assessed in 74 hypertensive patients. Transient myocardial ischemia was detected using an ST-triggered 24-h ambulatory blood pressure monitoring device.

RESULTS

ST-segment depressions were recorded in 30 of 74 patients. There were no significant differences with regard to age, mean arterial pressure, systolic blood pressure, diastolic blood pressure or heart rate. PWV was seen to be higher in patients with transient myocardial ischemia (10.6 versus 9.5 m/s, P = 0.036). There was no significant difference in AIx between the two groups. PWV (r = 0.36, P = 0.002) but not AIx correlated with pulse pressure.

CONCLUSIONS

PWV is higher in hypertensive individuals (age > 60 years) with transient myocardial ischemia, suggesting that PWV is an indicator of increased cardiovascular risk. Although AIx is known to be associated with several cardiovascular diseases, it was not seen to be associated with silent myocardial ischemia. Our results suggest that the clinical significance of parameters of arterial stiffness and arterial wave reflection change with age, with a higher clinical importance of PWV indicated in patients over the age of 60.

The Clinical Value of the ECG in Noncardiac Conditions

The ECG is an indispensable tool in the ICU for the detection and diagnosis of heart disease. ECG abnormalities however can be present in a wide variety of noncardiac conditions, complicating the differential diagnosis with primary cardiac pathology. This overview discusses the ECG abnormalities and their pathophysiologic basis in the most frequently encountered noncardiac conditions, such as electrolyte abnormalities, pulmonary embolism, CNS diseases, esophageal disorders, hypothermia, and drug-related and other conditions. Knowledge of the characteristic ECG changes may provide early clues to the presence of these disorders, the prompt recognition of which can be life saving.

Continuous haemodynamic monitoring using transoesophageal Doppler during acute normovolaemic haemodilution in patients with coronary artery disease

Transoesophageal Doppler monitoring allows non-invasive assessment of stroke volume. We studied haemodynamic changes during acute normovolemic haemodilution (ANH) in anaesthetised patients with coronary artery disease. Twenty patients were randomly assigned to either ANH or a control group. During ANH, a mean (SD) blood volume of 15.3 (3.4) ml.kg(-1) was withdrawn decreasing systemic oxygen delivery from 12.7 (3.3) to 9.3 (1.8) ml.kg(-1).min(-1) (p < 0.001). In the control group, haemodynamic data remained unchanged, whereas in the ANH group, stroke volume and central venous pressure increased significantly (mean = +21 ml [95% CI: 18-25 ml.min(-1)]; mean = +2.5 mmHg [95% CI: 2.2-2.8 mmHg], respectively) and heart rate decreased (mean = -6 beat.min(-1)[95% CI: 6-8 beat.min(-1)], p < 0.05). According to the Frank-Starling relationship, individual changes in stroke volume compared with central venous pressure fitted a quadratic regression model (R2 > 0.91). A reduced viscosity associated with ANH resulted in improved venous return, higher cardiac preload and increased cardiac output. In summary, this study demonstrated that ANH to a haemoglobin value of 8.6 g.dl(-1) was well tolerated in patients with coronary artery disease.

ST-segment depression in hypertensive patients is linked to elevations in blood pressure, pulse pressure and double product by 24-h Cardiotens monitoring

BACKGROUND

Various statements are made concerning peaks of heart rate (HR), blood pressure (BP) and double product (product of HR and systolic BP) as triggers for ST-segment depression. The aim of the present study was to identify determinants of ST-segment depression with a new ambulatory device for simultaneous 24-h electrocardiogram (ECG) and BP monitoring.

METHODS

A total of 63 treated patients (63 +/- 9 years, 33 women and 30 men) with arterial hypertension and ischemic heart disease were studied with a new ambulatory 24-h BP measurement (ABPM) device evaluated according to the BHS protocol (Cardiotens, Meditech, Hungary). This device allows simultaneous ST-segment analysis with extra BP recordings triggered by episodes of ST-segment depression.

RESULTS

ST-segment (Holter ECG) depression (> 1 mm and > 60 s) was demonstrated in 26 patients with a mean duration of 4.95 +/- 2.6 min and a peak in the early morning hours. All ST-segment depressions were silent and occurred during a significant increase of BP (15 +/- 11 mmHg systolic and 10 +/- 5 mmHg diastolic, compared with the mean ABPM values) and a significant increase of the double product from 10 921 +/- 2 395 (24-h mean) to 14 515 +/- 2329 (during ST-depression). The recorded systolic and diastolic BP (SBP, DBP) values from the pre ST-event were significant higher compared with 24-h values (153 +/- 19 versus 145 +/- 22 mmHg systolic, 83 +/- 12 versus 78 +/- 14 diastolic). The mean pulse pressure (PP) value in the group with ST-depression was significantly higher than in the group without ST changes (69 +/- 16 versus 58 +/- 10 mmHg; P < 0.005). A total of 73% of patients with ST-events compared with 35% without ST-events showed a PP >or= 60 mmHg (P = 0.025).

CONCLUSION

Simultaneous ABPM and ST-segment analysis identifies episodes of silent myocardial ischemia during increases of BP and HR. Hypertensive patients with ischemic heart disease and ST events show higher mean pulse pressure values than are observed in patients without events. A PP of >or= 60 mmHg is linked to an increased risk of silent myocardial ischemias.

Silent ischaemia and hypertension

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

Detection of myocardial ischemia with a computer-assisted 12-lead 24-hour ECG monitoring system (EAGLE) in patients with suspected unstable angina

This study was undertaken to evaluate the diagnostic value of a new device, the 'EAGLE' computer-assisted multiple-lead long-term electrocardiography (ECG) monitoring and analyzing system, in patients with suspected unstable angina, and to compare the results with the Holter monitor. A total of 101 patients with a history of suspected unstable angina underwent a simultaneous 24-h examination with the EAGLE and 2-channel Holter monitors. The diagnosis of unstable angina was established in 70 patients: 41 had significant organic stenosis, and 29 had coronary spasm. Ischemic ST deviations were detected 229 times in 44 patients (62.9%) with the EAGLE system and 101 times in 20 patients (28.6%) with the Holter monitor. The sensitivity of myocardial ischemia in unstable angina with the EAGLE system was significantly higher than that with Holter monitor (62.9 vs 28.6%, p<0.05). The difference of sensitivity was due mainly to the low detection rate of the Holter monitor for asymptomatic myocardial ischemia (EAGLE vs Holter; 187 times vs 72 times) and myocardial ischemia in the infero-posterior area in patients with organic stenosis (30 times vs none). It is concluded that the EAGLE system is a sensitive tool for the diagnosis of unstable angina in patients without significant ECG changes, and an excellent tool for evaluating silent myocardial ischemia or myocardial ischemia of the infero-posterior area.

Electrocardiographic repolarization during stress from awakening on alarm call

OBJECTIVES

The present study aimed to characterize the electrocardiographic features of cardiac repolarization during an arousal reaction in healthy subjects.

BACKGROUND

Electrocardiographic ST segments and T waves may indicate the activity of cardiac autonomic nervous control. Abnormal dynamics of repolarization are considered to reveal susceptibility to cardiac arrhythmias. Responses in normal subjects may help to understand the effects on patients' arrhythmias.

METHODS

Ambulatory electrocardiography was performed in 30 healthy physicians during emergency calls while they were on duty in the hospital. Samples were taken before and during the 1st 30 s after the calls. Polarity of the T wave and ST segment depression were determined. The QT interval and the cardiac cycle length (CL) were measured, and their relation (QT/CL slope) was calculated. For comparison, the QT interval was also measured in stable conditions at specified heart rates of 60 to 110 beats/min.

RESULTS

During arousal, the T wave was inverted in 19 subjects (63%) and the ST segment depressed > or = 0.1 mV in 10 (33%). The proportional duration of the terminal T wave also varied. The time course of these alterations followed the change in heart rate. During the strongest arousal reaction, the heart rate increased from 55 +/- 7 to 112 +/- 18 beats/min (mean +/-SD) and reached maximum at 17s on average. The QT interval shortened only slightly and was on average 59 to 67 ms longer (p < 0.001) than that at similar heart rates during stable conditions. The QT/CL slope was almost horizontal, 0.085 +/- 0.061, during arousal and much steeper, 0.168 +/- 0.055 (p < 0.001), during stable conditions.

CONCLUSIONS

Derangements in the T wave and ST segment as signs of sympathetic overactivity are common during arousal and are associated with marked inertia in QT interval adaptation. These modifications of ventricular repolarization may mediate the generation of stress-provoked arrhythmias in electrically unstable hearts.

Prevalence and circadian variations of ST-segment depression and its concomitant blood pressure changes in asymptomatic systemic hypertension

Coronary artery disease is a major complication of hypertension; one of its manifestations is silent ischemia. The aim of this study was to assess the prevalence and circadian distribution of ST-segment depression together with concomitant blood pressure (BP) and heart rate variations. One hundred patients (male:female ratio 1:1) with a mean age (+/- SD) of 51 +/- 8 years underwent ambulatory monitoring using the combined AMP 5600 monitor which simultaneously records a continuous Holter electrocardiogram and intermittent noninvasive BP measurements at 15-minute intervals, with extra measurements triggered by detection of a horizontal or downsloping ST depression (> 1 mm and >60 seconds). Cardiovascular risk factors were fully evaluated in all patients; accurate and reliable echocardiogram enabled left ventricular mass index to be calculated in 52 patients. Twenty-three patients (15 men and 8 women) experienced a total of 72 episodes of ST depression. Duration of such episodes (mean +/- SD) was 132 +/- 65 seconds and amplitude was 1.51 +/- 0.55 mm. Circadian distribution showed 2 peaks: on awakening and in the late afternoon periods. The mean ambulatory BP load was greater in the patients with than without ST-segment depression for both systolic and diastolic BP (135 +/- 14 vs 129 +/- 15 and 84 +/- 8 vs 79 +/- 10 mm Hg, respectively; p < 0.01). Plasma glucose (5.83 +/- 0.70 vs 5.46 +/- 0.71 mmol/L; p = 0.04) and self-related work-related stress levels (22% vs 13%; p = 0.03) were also higher in patients with ST-segment depression. There were no significant differences between groups for clinical parameters, left ventricular mass index, and other cardiovascular risk factors. During ST depression episodes, systolic BP increased by 9 +/- 15 mm Hg, diastolic BP by 7 +/- 11 mm Hg, and heart rate by 5 +/- 17 beats/min. Thus, 24-hour Holter electrocardiographic monitoring showed ST depression episodes in 23 of 100 hypertensive patients (23%); ambulatory BP load was greater in these patients. BP variations, and mainly its elevation, may trigger such episodes of ST-segment depression.

Myocardial ischemia after cardiopulmonary bypass

Intraoperatively, myocardial ischemia is more common after cardiopulmonary bypass (CPB) than before CPB. Ischemia associated with coronary vasospasm and thrombosis may be much more common toward the end of surgery and early in the postoperative period than previously appreciated. This may be because the coagulation system is altered during CPB, and the coronary endothelium is damaged significantly as a result of cardioplegic arrest followed by reperfusion. In this milieu, vasospasm and thrombosis may be caused by the administration of protamine. Some of the ischemia observed in this period actually is not reversible and is associated with myocardial injury and infarction. It may be ameliorated by the administration of calcium channel blockers, aspirin, and anticoagulants. Electrocardiography may be the most suitable modality for the detection of ischemia after CPB and postoperatively. During this period, many episodes of ST deviation are of a nonischemic etiology, and the ECG needs careful interpretation. Transesophageal echocardiography is suitable for use intraoperatively and early on in the intensive care unit.

Effect of precordial electrocardiographic electrode placement on ST-segment measurement during exercise

Research protocols often utilize serial exercise testing to examine the efficacy of anti-ischemic therapies. These tests, however, are prone to multiple sources of bias. This investigation sought to determine the influence of varying precordial electrocardiographic (ECG) electrode placement on the detection of exercise-induced ST-segment shifts. Fifteen coronary artery disease patients with abnormal exercise tests were studied. Based on the previous exercise test, the precordial electrode position exhibiting the greatest ST-segment shift was selected as the reference electrode. Four additional electrodes were placed around this reference electrode and exercise testing was performed. ECG strips were recorded every minute. The time-to-onset and -offset of ischemic-type ST-segment depression was recorded. ST-segment depression was recorded during exercise from the reference electrode in 12 of 15 patients. Ischemic-type ST-depression was also recorded in each of these 12 patients with the surrounding electrodes; however, the time-to-onset detected by all four surrounding electrodes concurred in only 5 of 12 (42%) patients. The time-to-offset of the ST-segment depression concurred in 9 of 12 (75%) patients. Serial ECGs recorded from similar but not exactly the same precordial ECG electrode position should yield similar results for the detection of ischemia, but time-to-onset or -offset of ischemia may differ by 60 s or more. Small changes in the time-to-onset and -offset of ischemia should not be considered reliable indicators of anti-ischemia efficacy.

Daily life cardiac ischaemia. Should it be treated?

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