Discriminating between right coronary artery and circumflex artery occlusion by using a noninvasive 18-lead electrocardiogram

BACKGROUND

Differentiating occlusion of the circumflex branch of the left coronary artery (also called the circumflex artery) from occlusion of the right coronary artery is often difficult because either may be associated with a pattern of acute inferior myocardial infarction on the electrocardiogram.

OBJECTIVES

To determine if an inexpensive 18-lead electrocardiogram can provide useful information in differentiating sites of coronary occlusion.

METHODS

Continuous 18-lead electrocardiograms, including standard 12-lead, right ventricular, and posterior leads, were recorded in 38 and 50 subjects undergoing percutaneous coronary interventions in the right coronary artery and the circumflex artery, respectively.

RESULTS

ST-segment elevation in the posterior leads was twice as frequent during occlusion of the circumflex artery as during right coronary occlusion (P < .001). ST-segment elevation in the right ventricular leads and inferior leads occurred more often during occlusion of the right coronary artery than during occlusion of the circumflex artery. ST-segment depression in lead aVL is highly suggestive of right coronary occlusion, whereas ST-segment elevation in posterior leads without depression of the ST segment in lead aVL is highly sensitive and specific for occlusion of the circumflex artery.

CONCLUSIONS

ST-segment changes in the 18-lead electrocardiogram can be used to differentiate between occlusions of the circumflex artery and occlusions of the right coronary artery. Knowing which vessel is occluded before percutaneous coronary intervention can help in planning the procedure and recognizing when patients are at high risk for disturbances in conduction at the atrioventricular node.

The Self-Care Self-Efficacy Enhancement Program for Chinese Nursing Home Elders

The purpose of this article is to introduce a theory-based intervention program, the Self-Care Self-Efficacy Enhancement Program (SCSEEP), which was derived from Bandura's Social Cognitive Theory (SCT). The SCSEEP, based on the concept of "perceived self-efficacy" within the SCT, was designed to improve self-care ability in Chinese nursing home elders. The theory-based SCSEEP was tested during a pilot study involving 42 elders from 2 nursing homes in Taiwan. Following the study, basic activities of daily living performance improved significantly in treatment group residents. Many Chinese elders are placed in nursing homes in the United States; thus, the SCSEEP may also be used as a theory-based caring model to improve self-care performance in Chinese Americans.

Discriminating Between Right Coronary Artery and Circumflex Artery Occlusion by Using a Noninvasive 18-Lead Electrocardiogram

• Background Differentiating occlusion of the circumflex branch of the left coronary artery (also called the circumflex artery) from occlusion of the right coronary artery is often difficult because either may be associated with a pattern of acute inferior myocardial infarction on the electrocardiogram.

• Objectives To determine if an inexpensive 18-lead electrocardiogram can provide useful information in differentiating sites of coronary occlusion.

• Methods Continuous 18-lead electrocardiograms, including standard 12-lead, right ventricular, and posterior leads, were recorded in 38 and 50 subjects undergoing percutaneous coronary interventions in the right coronary artery and the circumflex artery, respectively.

• ResultsST-segment elevation in the posterior leads was twice as frequent during occlusion of the circumflex artery as during right coronary occlusion (P &lt; .001). ST-segment elevation in the right ventricular leads and inferior leads occurred more often during occlusion of the right coronary artery than during occlusion of the circumflex artery. ST-segment depression in lead aVL is highly suggestive of right coronary occlusion, whereas ST-segment elevation in posterior leads without depression of the ST segment in lead aVL is highly sensitive and specific for occlusion of the circumflex artery.

• Conclusions ST-segment changes in the 18-lead electrocardiogram can be used to differentiate between occlusions of the circumflex artery and occlusions of the right coronary artery. Knowing which vessel is occluded before percutaneous coronary intervention can help in planning the procedure and recognizing when patients are at high risk for disturbances in conduction at the atrioventricular node.

The lipoprotein lipase gene in combined hyperlipidemia: evidence of a protective allele depletion

Background

Lipoprotein Lipase (LPL), a key enzyme in lipid metabolism, catalyzes the hydrolysis of triglycerides (TG) from TG-rich lipoproteins, and serves a bridging function that enhances the cellular uptake of lipoproteins. Abnormalities in LPL function are associated with pathophysiological conditions, including familial combined hyperlipidemia (FCH). Whereas two LPL susceptibility alleles were found to co-segregate in a few FCH kindred, a role for common, protective alleles remains unexplored. The LPL Ser447Stop (S447X) allele is associated with anti-atherogenic lipid profiles and a modest reduction in risk for coronary disease. We hypothesize that significant depletion of the 447X allele exists in combined hyperlipidemia cases versus controls. A case-control design was employed. The polymorphism was assessed by restriction assay in 212 cases and 161 controls. Genotypic, allelic, and phenotypic associations were examined.

Results

We found evidence of significant allelic (447X_control: 0.130 vs. 447X_case: 0.031, χ² = 29.085; 1df; p < 0.001) and genotypic association (SS: 0.745 vs. 0.939, and SX+XX: 0.255 vs. 0.061) in controls and cases, respectively (χ² = 26.09; 1df; p < 0.001). In cases, depletion of the 447X allele is associated with a significant elevation in very-low-density lipoprotein cholesterol (VLDL-C, p = 0.045). Consonant with previous studies of this polymorphism, regression models predict that carriers of the 447X allele displayed significantly lower TG, low-density lipoprotein cholesterol (LDL-C) and TG/high-density lipoprotein cholesterol (HDL-C) ratio.

Conclusion

These findings suggest a role for the S447X polymorphism in combined hyperlipidemia and demonstrate the importance of evaluating both susceptibility and protective genetic risk factors.

A quantitative evaluation of ST-segment changes on the 18-lead electrocardiogram during acute coronary occlusions

This study determined quantitative ST segment changes on the 18-lead electrocardiogram (ECG) during occlusions in each of the coronary arteries.

METHODS

Continuous 18-lead ECGs, including standard 12 leads, posterior (V7-9), and right ventricular (RV) leads (V3-5R) were recorded for 155 subjects undergoing percutaneous coronary occlusions, the maximum intervention.

RESULTS

During 58 left anterior descending (LAD) coronary occlusions, the maximum ST elevation and depression were in V3 (4.2 mm) and III (-0.9 mm), respectively. During 44 right coronary artery (RCA) occlusions, the maximum ST elevation and depression were in III (2.2 mm) and aVL (-1.4 mm), respectively. During 53 left circumflex (LCX) occlusions, the maximum ST elevation and depression were in V7 (0.8 mm) and V2 (-1.6 mm), respectively.

CONCLUSIONS

ST elevation often occurred in the anteroapical (V1-V6), lateral (I, aVL), and RV lead V(3R) during LAD occlusions; in the inferior, RV, and posterior leads during RCA occlusions; and in the posterior, inferior, and apical leads (V5-V6) during LCX occlusions.

BRCA1 genetic mutation and its link to ovarian cancer: implications for advanced practice nurses

PURPOSE

The purpose of this paper is to review (a) the linkage between the BRCA1 gene and ovarian cancer and (b) BRCA1 testing and its related issues. This review is aimed for nurse practitioners (NPs), who may be in positions to identify those at risk for BRCA1-associated ovarian cancer and to assist patients with related issues.

DATA SOURCES

Data sources include reviews and original research from scholarly journals and Internet sites.

CONCLUSIONS

Ovarian cancer is a deadly disease. Identification of those at risk because of BRCA1 mutation is possible through genetic testing. Testing for BRCA1 gene mutations has many implications whether results are positive or negative. Those with positive results will be faced with decisions regarding the best management strategies. Negative results do not completely eliminate ovarian cancer risk. Current management options for carriers of the BRCA1 mutation include taking no action, increasing surveillance for ovarian cancer, and chemoprevention with oral contraceptives or prophylactic oophorectomy for those who have completed childbearing. It is essential that NPs have knowledge underlying the issues and concerns of patients and their families at risk for BRCA1-associated ovarian cancer.

IMPLICATIONS FOR PRACTICE

NPs are in a unique position to help identify BRCA1 mutation carriers and to assist them and their families with the complex issues involving genetic testing and management options. Understanding these issues will allow NPs to give appropriate care that may include making appropriate referrals to certified genetic counselors and having balanced discussions on treatment options. Such measurements may improve early diagnosis of ovarian cancer and increase survival from this disease.

Newly mapped gene for thoracic aortic aneurysm and dissection

Thoracic aortic aneurysm and dissection (TAAD) is associated with high mortality and medical expense. These poor outcomes are preventable by surgical repair; however, identifying at-risk individuals is difficult. Researchers are actively surveying the human genome (the repository of human genes) to characterize the genetic determinants of TAAD by identifying chromosomal regions likely to harbor such predisposing genes. In previous studies, investigators identified genetic markers shared by a subset of families who were ascertained to have the disease, which clustered into 2 chromosomal regions: 5q13-q15 (TAAD1) and 11q23.2-q24 (familial aortic aneurysm [FAA1]). In a subsequent study, a third chromosomal region at 3p24-25 (TAAD2) was found to contribute to TAAD in a 4-generation, 52-member family that displayed little evidence of sharing either the TAAD1 or FAA1 regions. Although additional regions of the genome may contribute to TAAD, investigators are focusing their efforts on identifying the actual genes and the specific mutations that participate in the disease process. The goal of these endeavors is to develop screening tests to identify individuals at risk for familial TAAD. This genetic discovery has significant clinical implications because high-risk individuals and families can be closely monitored and can benefit from preventative surgical repairs.

Corneal Endothelial Cell Count in Keratoconus Patients After Contact Lens Wear

PURPOSE

The influence of contact lenses on healthy corneal endothelium has been well documented, but little is known about the effect of contact lens wear on the corneal endothelial cells of patients with keratoconus. This cross-sectional comparative study was conducted to determine quantitative characteristics of corneal endothelial cells of 100 patients with keratoconus with or without contact lenses.

METHODS

A Humphrey Atlas corneal topographer was used to map the keratoconic cornea. The corneal apex of the cone was located by using the axial topography map. The Konan SP-9000 Noncon Robo Pachy specular microscope and the Konan SP-400 specular microscopes were used to photograph the endothelium at the apex of the cone, and the average endothelial cell count was obtained. Patients were categorized into four groups based on the types of contact lenses worn: no contact lenses, SofLens 66 toric contact lenses, SoftPerm contact lenses, and FluoroPerm 30 aspheric rigid gas-permeable (RGP) contact lenses. Analysis of variance was used to determine differences in endothelial cell counts among groups.

RESULTS

After controlling for age and severity of keratoconus, patients who wore SoftPerm contact lenses had 18% lower endothelial cell counts (2,157 +/- 442) than did patients without contact lenses (2,538 +/- 398). These patients also had 15% lower endothelial cell counts than did patients who wore soft toric disposable contact lenses (2,483 +/- 292). There was a 7% lower endothelial cell count in the group wearing aspheric RGP contact lenses than in the group that did not wear contact lenses, and a 5% lower endothelial cell count in the group wearing aspheric RGP contact lenses than in the group that wore soft toric contact lenses, but these differences were not statistically significant.

CONCLUSIONS

Patients with keratoconus who wear SoftPerm contact lenses have a significantly lower endothelial cell count than those patients with keratoconus who do not wear lenses, or who wear soft toric disposable contact lenses or RGP contact lenses.

Gender and Ethnic Differences in a Case-Control Study of Dyslipidemia: Using the Apolipoprotein A-V Gene as an Exemplar in Cardiovascular Genetics

Common, complex genetic disorders such as coronary heart disease (CHD) frequently show large population differences, contributing to health disparities. It is also well known that CHD risk factor profiles and the frequency of coronary events differ by gender. Study of premature CHD has revealed that apolipoproteins are important discriminating factors for distinguishing individuals with CHD. Recent findings indicated that apolipoprotein A-V (APOA-V) gene promoter polymorphisms are an important determinant of plasma triglycerides (TG) and lipoprotein cholesterol, and a risk factor for CHD. Variations in APOA-V may have varying impacts in different ethnic groups. The purpose of this interdisciplinary genetic research project was to determine (1) the association of the APOA-V polymorphisms with lipoprotein profiles, and (2) the gender and ethnic differences in the T-1131C promoter polymorphism of the APOA-V gene in individuals with dyslipidemia versus controls. Results indicate that the minor -1131C allele (CC homozygotes + CT heterozygotes) was associated with elevated plasma TG (p= 0.007), very low density lipoprotein (VLDL)–TG (p= 0.019), LDL-TG (p= 0.004), high-density-lipoprotein (HDL)-TG (p< 0.001), and VLDL-cholesterol (p= 0.008). We found a striking elevation in the frequency of the minor C allele in Asians (p< 0.001) compared to Europeans. We also found a significant difference in genotype frequency between men and women in Asians (p= 0.031) and Europeans (p< 0.01). Remarkably, Asian women with the C allele have a 36% increase in TG compared to Asian women homozygous for the T allele. In summary, we found significant ethnic-specific and gender-based differences in the frequency of the minor allele of the -1131 APOA-V gene promoter polymorphism. Identification of genetic variations among ethnic groups and between genders may have significant potential for a better understanding of the development of cardiovascular disease.

Genetic advances in coronary artery disease

Traditionally, many health care providers consider clinical genetics to be a field that only applies to specialists who provide services to individuals with rare single-gene or chromosomal disorders. But this concept is changing rapidly. In the year 2000, nine of the ten leading causes of mortality, including heart disease, have identified genetic components. As patient advocates and health care providers, nurses have a responsibility to become familiar with genetic advances and translate this knowledge into improved individualized care for patients.

Computer-assisted continuous ST-segment analysis for clinical research: methodological issues

Continuous ST-segment monitoring has been used to detect acute myocardial ischemia, determine the success of the reperfusion therapy, and predict outcomes in both research and a variety of clinical settings. However, analyzing the abundant electrocardiography (ECG) data recorded using continuous multilead ST-segment monitoring techniques is time consuming and requires expertise. Experienced data interpreters in dedicated ECG core laboratories handle many continuous ECG data records from large clinical trials. Little information on measurement issues for computer-assisted ST-segment analysis is available for individual investigators. Unsupervised or inexperienced computer analysis of ST-segment deviations can, under certain circumstances, yield invalid or unreliable summary indices. The goal of this article is to discuss basic ST-segment measurement principles in evaluating acute myocardial ischemia and methodological issues surrounding the use of computer-assisted ST-segment analysis for continuous ECG data. Variables affecting ST-segment measurements will be examined. Sources and examples of variability for these potential errors will be identified.

Thoracic location of the lead with maximal ST-segment deviation during posterior and right ventricular ischemia: comparison of 18-lead ECG with 192 estimated body surface leads

By using our database of continuous 18-lead electrocardiographic (ECG) recordings (standard + V3-5R + V7-9) during coronary angioplasty, we selected 68 patients with left circumflex balloon occlusions (posterior ischemia model) or proximal right coronary artery balloon occlusions (right ventricular IRV] ischemia model). ST-segment amplitudes (J + 60 ms) at preangioplasty baseline were subtracted from maximal ST amplitudes during balloon inflation to create a positive or negative change score (deltaST) for each of the 18 leads. DeltaST elevation was used to describe a change in the ST level in the positive direction from baseline, whether or not actual ST elevation from the isoelectric line was present. DeltaST depression was used to describe a change in the ST level in the negative direction from baseline, whether or not actual ST depression from the isoelectric line was present. ST amplitudes from 8 of the 12 standard leads were then used to estimate ST amplitudes at 192 body surface sites spanning the entire anterior and posterior thorax using the transformation technique of Lux. Thoracic distributions of the DeltaST values were displayed on a torso figure, including locations of the 18 lead locations and points of maximal ST elevation and depression. The 192 estimated body surface unipolar leads were compared with 18-lead ECGs (bipolar and unipolar). During 53 left circumflex occlusions, the maximal deltaST elevation was always located in the 18-lead ECG, with the most frequent locations at leads III, II (41%), V7-8 (34%), and V5-6 (25%). The maximal deltaST depression was located outside the 18-lead ECG (89%), with the most frequent locations above standard lead V2 (67%) and V3 (14%). During 16 proximal right coronary artery occlusions, the maximal deltaST elevation was always located in the 18-lead ECG, with the most frequent locations at leads III (81%) and V2-3R (13%). The maximal deltaST depression was located outside the 18-lead ECG (93%), with the most frequent locations above standard lead V2 (50%), V3 (14%), and V4 (14%). We conclude that maximal deltaST elevation is always located in the 18-lead ECG and maximal deltaST depression is frequently located outside of 18-lead ECG during left circumflex and proximal right coronary artery occlusions. Future studies are required to determine the bipolar leads for the 192 estimated body surface potential mapping leads.

New electrocardiographic criteria for posterior wall acute myocardial ischemia validated by a percutaneous transluminal coronary angioplasty model of acute myocardial infarction

The standard 12-lead electrocardiogram (ECG) fails to detect ST-segment elevation in patients with posterior wall acute myocardial ischemia. However, additional posterior leads V(7-9) provide limited additional diagnostic information to the standard 12-lead ECG when an ischemic criterion of 1-mm ST elevation is used. No study is available to delineate the ischemic criteria in the posterior electrocardiographic leads. Continuous 15-lead ECGs (standard 12 lead + V(7-9)) were recorded in 53 subjects undergoing elective left circumflex coronary angioplasty (posterior ischemia model). ST amplitudes (J + 60 ms) at preangioplasty baseline were subtracted from maximal ST amplitudes during balloon occlusion to create a positive or negative change score (DeltaST) for each of the 15 leads. During 53 left circumflex occlusions, 26 subjects (49%) had DeltaST elevation of > or = 1 mm and 24 subjects (45%) had DeltaST elevation ranging from 0.5 to 0.95 mm in > or = 1 posterior leads. Five subjects (9%) had DeltaST elevation of > or = 1 mm in the posterior leads without DeltaST elevation anywhere in any of the 12 leads. The sensitivity in detecting myocardial ischemia using 15-lead ECGs (58%) was not statistically different from the standard 12-lead ECG (49%) (p = 0.06). Adjusting the ischemic criterion from 1 to 0.5 mm in V(7-9) significantly improved the sensitivity from 49% in the 12-lead ECG to 94% in the 15-lead ECG (p = 0.000). In addition, 12 subjects (23%) had posterior ST-segment elevation without anterior ST-segment depression. Thus, posterior leads V(7-9) contribute significant additional diagnostic information above and beyond the standard 12-lead ECG only when a new ischemic criterion of 0.5 mm instead of 1 mm ST elevation is applied to the posterior leads.

Comparison of 18-lead ECG and selected body surface potential mapping leads in determining maximally deviated ST lead and efficacy in detecting acute myocardial ischemia during coronary occlusion

Kornreich identified 6 body surface potential mapping (BSPM) leads outside the standard 12-lead electrocardiographic (ECG) sites for optimal recognition of ST segment elevation (+) and depression (-) during acute ischemia in anterior, inferior, and posterior myocardial zones (A+, A-, I+, I-, P+, P-). No comparison has been made between the 6 selected BSPM leads and 18-lead ECG (12 + V3-5R + V7-9) in detecting acute myocardial ischemia during coronary occlusion. Continuous 18-lead ECG and 6 selected BSPM leads were recorded in 68 patients (77 vessels) undergoing coronary angioplasty during balloon occlusion. Ischemia was defined as ST segment deviation (deltaST) > or = 100 microV > or = 1 lead from the preinflation baseline. The 18-lead ECG was a more frequent source of the maximal deltaST lead during left anterior descending artery, right coronary artery, and left circumflex artery occlusion (71 [92%]) than the 6 selected BSPM leads (5 [7%]). The 18-lead ECG was more efficacious than the 6 selected BSPM leads for detecting acute myocardial ischemia in the group as whole. The 18-lead ECG was also more efficacious for detecting right ventricular ischemia associated with proximal right coronary artery occlusion and for detecting ST segment elevation during left circumflex artery occlusion. Our findings indicate that the 18-lead ECG is the most frequent source of maximally deviated lead and is more efficacious in detecting myocardial ischemia during balloon occlusion than the 6 selected BSPM leads. The 6 selected BSPM leads do not add information above and beyond the 12- or 18-lead ECG, and thus cannot be recommended as optimal sites for continuous ST segment monitoring of patients with acute coronary syndromes.

Accuracy of the EASI 12-lead electrocardiogram compared to the standard 12-lead electrocardiogram for diagnosing multiple cardiac abnormalities

This study was performed to compare a derived 12-lead electrocardiogram (ECG) using a simple 5-electrode lead configuration (EASI 12-lead) with the standard ECG for multiple cardiac diagnoses. Accurate diagnosis of arrhythmias and ischemia often require analysis of multiple (ideally, 12) ECG leads; however, continuous 12-lead monitoring is impractical in hospital settings. EASI and standard ECGs were compared in 540 patients, 426 of whom also had continuous 12-lead ST segment monitoring with both lead methods. Independent standards relative to a correct diagnosis were used whenever possible, for example, echocardiographic data for chamber enlargement-hypertrophy, and troponin levels for acute infarction. Percent agreement between the 2 methods were: cardiac rhythm, 100%; chamber enlargement-hypertrophy, 84%-99%; right and left bundle branch block, 95% and 97%, respectively; left anterior and posterior fascicular block, 97% and 99%, respectively; prior anterior and inferior infarction, 95% and 92%, respectively. There was very little variation between the 2 lead methods in cardiac interval measurements; however, there was more variation in P, QRS, and T-wave axes. Of the 426 patients with ST monitoring, 138 patients had a total of 238 ST events (26, acute infarction; 62, angioplasty-induced ischemia; 150, spontaneous transient ischemia). There was 100% agreement between the 2 methods for acute infarction, 95% agreement for angioplasty-induced ischemia, and 89% agreement for transient ischemia. EASI and standard 12-lead ECGs are comparable for multiple cardiac diagnoses; however, serial ECG changes (eg, T-wave changes) should be assessed using one consistent 12-lead method.

Frequency of ischemia during intracoronary ultrasound in women with and without coronary artery disease

Myocardial ischemia is common during ICUS imaging in women with and without CAD. Although no long-term adverse effects occurred in our small sample, a larger sample of women is required to confirm our observations and to determine the precise mechanisms of ischemia. Such studies may determine whether the smaller diameter of coronary vessels in women makes the women more vulnerable than men to the occurrence of chest pain and ischemia during ICUS. Although ICUS is valuable in guiding coronary interventions, disposable catheters are costly. Studies are required to assess the cost-benefit ratio of incorporating ICUS with coronary interventional procedures. Until more is known, we recommend that nurses educate patients about ICUS, monitor them closely for ischemia and arrhythmias during the procedure, and consider obtaining 12-lead ECGs when patients undergo and ICUS procedure.

Frequency of ischemia during intracoronary ultrasound in women with and without coronary artery disease

Myocardial ischemia is common during ICUS imaging in women with and without CAD. Although no long-term adverse effects occurred in our small sample, a larger sample of women is required to confirm our observations and to determine the precise mechanisms of ischemia. Such studies may determine whether the smaller diameter of coronary vessels in women makes the women more vulnerable than men to the occurrence of chest pain and ischemia during ICUS. Although ICUS is valuable in guiding coronary interventions, disposable catheters are costly. Studies are required to assess the cost-benefit ratio of incorporating ICUS with coronary interventional procedures. Until more is known, we recommend that nurses educate patients about ICUS, monitor them closely for ischemia and arrhythmias during the procedure, and consider obtaining 12-lead ECGs when patients undergo and ICUS procedure.

Frequency of silent myocardial ischemia with 12-lead ST segment monitoring in the coronary care unit: are there sex-related differences?

BACKGROUND

Ischemia that occurs in the coronary care unit (CCU), whether symptomatic or silent, is associated with significant in-hospital and out-of-hospital complications. Studies have reported that more than 90% of ischemic episodes are silent in patients with unstable angina who are treated in the CCU with maximal medical therapy. Prior reports indicate that women complained more frequently of chest pain than men did.

PURPOSE

The aim of this study was to compare the frequency of silent myocardial ischemia in men versus women with use of continuous 12-lead ST segment monitoring in the CCU. A secondary goal was to determine whether silent ischemia was associated with less ST segment deviation as compared with symptomatic ischemia.

METHOD

Patients admitted for treatment of acute coronary syndrome in the CCU and who subsequently had 1 or more ischemic events during their monitoring period were selected for this analysis. All patients were continuously monitored (42.5 hours +/- 37.6) in the CCU with the EASI (Zymed Medical Instruments, Camarillo, Calif) 12-lead electrocardiogram (ECG) system that derives 12 leads with use of 3 information channels and 5 electrodes.

RESULTS

Of 491 patients, 128 (91 men and 37 women) had at least 1 episode of transient myocardial ischemia. Men and women did not differ in their proportion of chest pain during ischemia (men 27% and women 21%, NS). For both men and women, ST segment deviation was significantly greater during symptomatic ischemia compared with silent ischemia.

CONCLUSION

There are no sex-related differences in ischemic events in the CCU in regards to the variables of chest pain and ST magnitude. Therefore, because chest pain is not a reliable indicator of myocardial ischemia in the CCU, regardless of sex, patients should be adequately monitored for ischemic events.

Peak time of occurrence of myocardial ischemia in the coronary care unit

BACKGROUND: The onset of acute myocardial infarction and sudden cardiac death has a circadian variation, with the peak occurrence between 6 AM and 12 noon. OBJECTIVES: To determine if a circadian variation exists for transient myocardial ischemia in patients admitted to the coronary care unit with unstable coronary syndromes. METHODS: The sample was selected from patients enrolled in a prospective clinical trial who had had ST-segment monitoring for at least 24 hours and had had at least one episode of transient ischemia. The 24-hour day was divided into 6-hour periods, and comparisons were made between the 4 periods. RESULTS: In 99 patients, 61 with acute myocardial infarction and 38 with unstable angina, a total of 264 (mean +/- SD, 3 +/- 2) ischemic events occurred. Patients were more likely to have ischemic events between 6 AM and noon than at other times. A greater proportion of patients complained of chest pain between 6 AM and noon than during the other 3 periods. However, more than half the patients never complained of chest pain during ischemia between 6 AM and noon. CONCLUSION: Transient ischemia occurs throughout the 24-hour day; however, ischemia occurs more often between 6 AM and noon. An important nursing intervention for detecting ischemia is continuous electrocardiographic monitoring of the ST segment, even during routine nursing care activities, which are often at a peak during the vulnerable morning hours.

Peak time of occurrence of myocardial ischemia in the coronary care unit

BACKGROUND

The onset of acute myocardial infarction and sudden cardiac death has a circadian variation, with the peak occurrence between 6 AM and 12 noon.

OBJECTIVES

To determine if a circadian variation exists for transient myocardial ischemia in patients admitted to the coronary care unit with unstable coronary syndromes.

METHODS

The sample was selected from patients enrolled in a prospective clinical trial who had had ST-segment monitoring for at least 24 hours and had had at least one episode of transient ischemia. The 24-hour day was divided into 6-hour periods, and comparisons were made between the 4 periods.

RESULTS

In 99 patients, 61 with acute myocardial infarction and 38 with unstable angina, a total of 264 (mean +/- SD, 3 +/- 2) ischemic events occurred. Patients were more likely to have ischemic events between 6 AM and noon than at other times. A greater proportion of patients complained of chest pain between 6 AM and noon than during the other 3 periods. However, more than half the patients never complained of chest pain during ischemia between 6 AM and noon.

CONCLUSION

Transient ischemia occurs throughout the 24-hour day; however, ischemia occurs more often between 6 AM and noon. An important nursing intervention for detecting ischemia is continuous electrocardiographic monitoring of the ST segment, even during routine nursing care activities, which are often at a peak during the vulnerable morning hours.

12-lead ST-segment monitoring vs single-lead maximum ST-segment monitoring for detecting ongoing ischemia in patients with unstable coronary syndromes

BACKGROUND: 12-lead ECG monitoring of the ST segment is more sensitive than patients' symptoms for detecting ischemia after thrombolytic therapy or catheter-based interventions, but it is unclear whether monitoring of the single lead showing maximum ST deviation would be as efficacious. OBJECTIVE: To determine whether monitoring all 12 ECG leads for changes in the ST segment is necessary to detect ongoing ischemia in patients with unstable coronary syndromes. METHODS: Continuous 12-lead ST segment monitoring was performed in 422 patients from the onset of myocardial infarction or during balloon inflation in catheter-based interventions until the patient's discharge from the cardiac care unit. Computer-assisted techniques were used to determine (1) which lead showed the maximum ST deviation at the onset of myocardial infarction or during balloon inflation and (2) what proportion of later ischemic events were associated with ST deviation in this lead. RESULTS: The lead with the maximum ST deviation could be determined in 312 patients (74%). The remaining 110 (26%) had non-Q wave infarction without ST deviation or no ST changes during balloon inflation. During 18,394 hours of 12-lead ST monitoring, 118 (28%) of the 312 patients had a total of 463 ischemic events, 80% of which were silent. Of 377 ischemic events in which a maximum ST lead was detected, 159 (42%) did not show ST deviation in this lead (sensitivity, 58%; 95% CI, 53%-63%). Routine monitoring of leads V1 and II showed ST deviation in only 152 of the 463 events (sensitivity, 33%; 95% CI, 29%-37%). CONCLUSIONS: Monitoring of all 12 ECG leads for changes in the ST segment is necessary to detect ongoing ischemia in patients with unstable coronary syndromes.

12-lead ST-segment monitoring vs single-lead maximum ST-segment monitoring for detecting ongoing ischemia in patients with unstable coronary syndromes

BACKGROUND

12-lead ECG monitoring of the ST segment is more sensitive than patients' symptoms for detecting ischemia after thrombolytic therapy or catheter-based interventions, but it is unclear whether monitoring of the single lead showing maximum ST deviation would be as efficacious.

OBJECTIVE

To determine whether monitoring all 12 ECG leads for changes in the ST segment is necessary to detect ongoing ischemia in patients with unstable coronary syndromes.

METHODS

Continuous 12-lead ST segment monitoring was performed in 422 patients from the onset of myocardial infarction or during balloon inflation in catheter-based interventions until the patient's discharge from the cardiac care unit. Computer-assisted techniques were used to determine (1) which lead showed the maximum ST deviation at the onset of myocardial infarction or during balloon inflation and (2) what proportion of later ischemic events were associated with ST deviation in this lead.

RESULTS

The lead with the maximum ST deviation could be determined in 312 patients (74%). The remaining 110 (26%) had non-Q wave infarction without ST deviation or no ST changes during balloon inflation. During 18,394 hours of 12-lead ST monitoring, 118 (28%) of the 312 patients had a total of 463 ischemic events, 80% of which were silent. Of 377 ischemic events in which a maximum ST lead was detected, 159 (42%) did not show ST deviation in this lead (sensitivity, 58%; 95% CI, 53%-63%). Routine monitoring of leads V1 and II showed ST deviation in only 152 of the 463 events (sensitivity, 33%; 95% CI, 29%-37%).

CONCLUSIONS

Monitoring of all 12 ECG leads for changes in the ST segment is necessary to detect ongoing ischemia in patients with unstable coronary syndromes.

Bedside diagnosis of myocardial ischemia with ST-segment monitoring technology: measurement issues for real-time clinical decision making and trial designs

Monitoring of the ST segment is a valuable tool for guiding clinical decision making and evaluating anti-ischemia interventions in clinical trials; however, measurement issues hamper its diagnostic accuracy. This study reports the frequency and type of false positives and other measurement issues we have encountered during 12-lead ST-segment monitoring of patients in a cardiac care unit. Of 292 patients, 117 (40%) had one or more false positive events during an average of 41 hours of ST-segment monitoring, for a total of 506 false positive events. The 506 false positive events included 167 (36%) due to body positional change; 132 (26%) due to sudden increase in QRS complex/ST-segment voltage; 96 (19%) due to transient arrhythmia or pacing; 80 (16%) due to heart rate change in steeply sloped ST-segment contours; 26 (5%) due to a noisy signal; and 5 (1%) due to lead misplacement. It is concluded that many conditions in addition to myocardial ischemia can cause transient ST-segment deviation in patients with unstable coronary syndromes. Accurate ST-segment monitoring requires expertise in electrocardiogram interpretation, an understanding of the patient's clinical situation, and knowledge of the functions and limitations of the ST-segment monitoring system.