Opportunistic screening for cardiovascular problems in rural and remote health settings. Herbert Jelinek, Paul Warner, Stephen King and Bev De Jong.  Journal of Cardiovascular Nursing 21.3 (May-June 2006): p217(6). 

Background: Cardiovascular disease is the leading cause of death in Australia and the United States. It is not known if routine electrocardiogram (ECG) assessment at the community level could identify a significant proportion of people with clinically relevant ECG anomalies who could benefit from intervention. Purpose: This study aimed to elucidate the use of 3-lead ECG assessment by community nurses in rural and remote health settings. We report the findings obtained from 20-minute, lead II ECG recordings of 71 people who participated in a diabetes screening study. Results: Seven participants reported cardiac anomalies before screening. One or more ECG abnormalities were found in 45 participants. Of these, nine people who were otherwise asymptomatic showed abnormal ECG characteristics that warranted further investigation. Conclusion: Although further research is needed, incorporating routine 3-lead ECG testing in rural and remote communities may improve general health in the community by providing early recognition of cardiac anomalies in otherwise asymptomatic individuals who may be amenable to treatment. This study has implications for community nurses on two levels: opportunistic screening, monitoring and evaluation.

KEY WORDS: 3-lead ECG, community nursing, dysrhythmia, screening

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Cardiovascular disease (CVD) is the leading cause of death in Australia) It is estimated that by the year 2020, 40% of deaths worldwide will he caused by CVD. (2) A significant proportion of CVD is asymptomatic. (3) The underlying pathology varies among individuals but includes coronary artery disease, long QT syndrome, cardiomyopathies, premature atrial or ventricular contractions (PAC or PVC), atrial or ventricular tachycardias, and bradycardias. (4) The burden of chronic disease on individuals and healthcare professionals is considerable and supports an alternative model of healthcare incorporating early assessment and intervention. In Australia and worldwide, healthcare delivery is changing from hospital- to community-based programs because of increases in costs, an aging population, and increased numbers of people living with chronic disease. (5) Including an electrocardiogram (ECG) assessment as part of a routine community visit has the potential to improve early identification and treatment of CVD.

The ECG is an important adjunct to risk stratification and decision for further assessment because a large proportion of individuals with chronic CVD are asymptomatic. In individuals with acute chest pain, the ECG aids the clinical decision process of whether to refer to a hospital or not. However, opportunistic screening of asymptomatic individuals is not recommended by most government agencies. For example, the US Preventative Services task Force found insufficient evidence to recommend for or against routine screening with ECG. (6-8) Reasons include low sensitivity and high costs associated with 12-lead ECGs and the technical expertise required. (9) Routine 10-second 12-lead ECG tends to miss anomalies such as transient changes, including ST-segment elevation, PVCs, and atrial fibrillation. However, using a 3-lead configuration and recording for a longer period would identify most of the transient rhythms. This approach, coupled with the ease of application of limb leads, makes a targeted community screening with a 3-lead ECG assessment attractive.

In community healthcare, prior research has shown a clear benefit in recording baseline ECGs before cardiac symptoms appear. (10) Greater access and targeted assessment followed by on-the-spot healthcare also reduce healthcare costs and the disparity in healthcare between rural and urban communities. (11)

Practical and Evidence-Based Decisions on Method for ECG Recording

The relative value of any screening test depends on its cost, the prevalence of abnormalities identified, the relationship of abnormalities to morbidity and mortality, and the possibility of reducing or avoiding future morbidity or mortality. (12) Decisions on which ECG method (3-lead or 12-lead) is most practical are based on context. Community health service nurses are often equipped with a defibrillator that has a 3-lead ECG recording option to assess conduction and rhythm disturbances. (13) Emergency services also assess a 3-lead recording followed by a 12-lead assessment if necessary.

Apart from contextual decisions on which ECG recording method is more appropriate, the sensitivity and specificity of ECG recording as a diagnostic tool have to be considered, as well as the recording protocol. Regardless of whether a 3-, 5-, or 12-lead ECG is used, sensitivity and specificity are largely dependent on incidence of disease in a population. Therefore, screening or assessing individuals with prior CVD or in high-risk groups will have better outcomes. (14) The ECG assessment is used by numerous healthcare practitioners, including community health nurses, and has shown a very high degree of sensitivity and specificity when combined with signs and symptoms. (15) A recent comparative study of 12- and 3-lead (III, [V.sub.2], [V.sub.5]) ECG in patients presenting to an emergency department with unstable angina reported ST episodes in 77% versus 62% of patients, respectively (P < .05). The difference suggests that a large proportion of patients with CVD can be identified using 3-lead ECGs. (16) Regular 5- to 20-minute recordings are more likely to pick up anomalies compared with 10-second recordings. The frequency at which individuals are screened correlates with the likelihood of detecting life-threatening ECG anomalies. (17) In a study comparing 12-lead to 3-lead ECG-based referrals, a similar number of people required further testing irrespective of ECG configuration. (17)

Community health access provides an opportunity for regular assessment of patients by community nurses. A 3-lead recording of 5 minutes or more can be administered during a home-care visit to high-risk clients with or without diagnosed CVD.

Potential Use of Single-Lead ECG Assessment by Community Nurses

Heart failure, commonly associated with dysrhythmias, is the most common diagnostic group in Australia. (18) Syncope, either associated with or independent of long QT, and atrial fibrillations are two additional cardiovascular pathologies that have a high prevalence and lend themselves to ECG identification. (4,19,20) Nurses play an important role in the identification of CVD and the reduction of the risk of sudden cardiac death, which includes regular ECG assessment. (21)

The ECG can provide information on the orientation of the heart in the chest, conduction disturbances, electrical effects of medications and electrolytes, the mass of the cardiac muscle, and the presence of ischemic change. Standard limb leads, available in 3-lead ECG configuration, provide information on the lateral (lead I) and inferior (lead II and III) surface of the heart. Using the limb leads, one can also determine the augmented leads that provide information on the lateral (aVL) and inferior (aVF) surfaces of the heart. For a recording where the heart has a normal electrical axis, lead II is a good choice because it displays a waveform that is predominantly upright and has the greatest amplitude and, therefore, the best signal-to-noise ratio. QRS complexes and P and T waves are easily identified, as weLl as PR, QRS, and QT intervals and ST segment evaluation. (22)

Lead II has good sensitivity and specificity for dysrhythmias. Lead II can also reveal ST-segment changes that indicate asymptomatic transient ischemia and ischemia associated with angina. If ischemia is suspected, a 12-lead recording can increase sensitivity, and the client can be referred to a physician for further assessment. Lead II ECG traces can identify extreme electrolyte imbalances involving potassium, calcium, and magnesium. These abnormalities are indicated by signs such as tented T waves, PVCs, prominent U waves, shortened or prolonged QT interval, prolonged PR intervals, and widened QRS intervals. (23)

Much of the literature deals with ECG assessment in coronary care units. We were interested whether standard lead II recording could identify asymptomatic individuals with CVD who would otherwise not be recognized. Our specific aim was to determine the efficacy of ECG assessment using 3-lead ECG recordings as an adjunct to community healthcare in two rural Australian towns. The study focused on the presence or absence of abnormal ECG findings as seen in 3-lead rhythm traces and their clinical significance.

Methods

Seventy-one people from rural Australia participated in our study between 2002 and 2003. Individuals responded to a newspaper and television segment advertising the study. The criteria for inclusion in the study were aged 45 years or older and no known history of diabetes. No other exclusion or inclusion criteria were set to obtain a good cross-section of the community. For each individual, a medical history was taken and a 3-lead ECG recorded for 20 minutes. Characteristics of the group are shown in Table 1. Our study had ethics approval, and all individuals consented to have their ECG recorded and a medical history taken.

Electrocardiogram traces were recorded by a trained research assistant using a Macintosh iBook linked to a Maclab recording system and visualized with Chart 5 (ADInstruments). All recordings were assessed by a cardiac nurse specialist and verified by a staff cardiologist.

Results

The cardiac anomalies were divided into benign and serious (clinically significant), with people falling into the serious category referred for further investigation (Table 2). Seven people reported a known ECG anomaly during the initial interview, and these reports were subsequently confirmed using the 3-lead ECG. Of these, three had coronary artery disease, two reported a prior myocardial infarct, one had atrial fibrillation that was treated pharmacologically and displayed as atrial flutter, and one had unspecified cardiac pathology. Overall, 45 (64%) participants had one or more ECG anomaly.

Thirteen had serious ECG findings, including 9 with no previous record of cardiac dysrhythmias or pathology. Thus, 12% of ECG abnormalities represented new cases that required further investigation. Anomalies identified in this study included atrial flutter, ST changes, peaked T waves, notched P and QRS waves, and unifocal and multifocal PVCs and PACs.

All serious ECG findings were referred for follow-up. One person with ST elevation referred to the general practitioner died and was lost to follow-up. Another participant reported intermittent chest pain and is under the management of the general practitioner. Three patients with ST depression, including one patient also presenting with multifocal PVCs, were referred to their physician and were started on cardiac medication. Two participants had notched P waves suggesting mitral valve disease, but one was subsequently deemed clinically unremarkable. Another with irregular heart rate, PAC, and borderline long QT continues to be monitored. One participant with PVC couplet and slurred S and peaked T waves was found to have an incompetent valve. This person was advised by his general practitioner to reduce his daily exercising, and the subsequent ECG showed no clinically significant anomalies. Thus, of the 13 participants requiring follow-up based solely on the 3-lead ECG, 4 had previous CVD and were undergoing treatment. Of the remaining nine, two were cleared by their general practitioner after a 12-lead ECG and clinical examination. In seven patients, new treatment was initiated. This represents a 77% accuracy in detecting asymptomatic CVD.

Discussion

Community screening as proposed here aims at increasing the number of people identified with serious ECG abnormalities that may otherwise not be identified. The intention is not to replace the cardiologist or the general practitioner, but to triage people to care before an event. In our study, nine people were identified with serious ECG anomalies, and seven of these required follow-up by the general practitioner. The percentage of significant CVD detected was large, but we expect the percentage to be even larger in groups with known CVD or diabetes. (17)

It is estimated that by 2010, there will be at least 25 patients with heart failure per each general practitioner in Australia, with the ratio being greater in rural and remote regions. Effective, collaborative multidisciplinary teams that include nurse practitioners, community nurses, and pharmacists can reduce the burden on physicians. (24) UK and US data show that implementing community-based healthcare produces high patient satisfaction. Our study illustrates the efficacy of 3-lead ECG recording as an adjunct to a primary or secondary community health service that may lead to optimizing prevention or decreasing morbidity from CVD. Routine ECG recording in outpatient community health provides baseline data and regular assessment of cardiac function.

We identified clinically significant 3-lead ECG recordings in people with known CVD and in asymptomatic individuals. This result confirms recent research that has shown benefit when recording baseline ECGs before cardiac symptoms appear. (10) Combining the patient's history and current pulse characteristics with the data from a 3-lead tracing provides enough information for the community nurse to make a decision whether to refer to a general practitioner for further assessment.

In this study, the percentage (12%) of asymptomatic individuals identified with potentially serious CVD is consistent with the rate noted in past studies with 12-lead ECGs and/or Holter monitoring. An 8-year trial of Q-wave myocardial infarction reported a rate of 10.59/o. (19) Another study reports an 11% positive identification of people with syncope and 8% of participants in a heart study associated with atrial fibrillation, all first identified by ECG screening. (20)

Cardiac problems, especially rhythm disturbances associated with coronary artery disease and other anomalies that increase mortality, even when asymptomatic, can often be detected using resting 3-lead ECG. A Netherlands study of dysrhythmia detection in general practice reported finding a clinically relevant ECG in 36% of patients with symptoms and in 19% of asymptomatic patients. (25) In a similar UK study, 12% of patients with atrial fibrillation were identified by ECG screening. (20) Although up to 3% of ECGs are misinterpreted, this is far less than the approximately 30% of people with asymptomatic disease that are not screened at all, of whom 15% to 50% die of sudden cardiac death. (3)

Despite a surprisingly high number of cardiac anomalies identified in this study and in past research, opportunistic screening for undiagnosed cardiac complications is not advocated by the National Health and Medical Research Council, the US Preventive Services Task Force, and Guidelines of the American College of Cardiology. (26,27) Importantly, however, the recommendations of these groups address screening of the general population. As a general screening tool, ECG has low sensitivity and specificity. However, in a population with high risk for CVD, the predictive value of the ECG increases significantly. (10) Further evidence on screening is needed, though, because ECG abnormalities found on a 2-minute rhythm strip were shown to be an independent predictor of morbidity and mortality in people without definitive heart disease in the Framingham study. (28,29)

Implications for Nursing Care in Rural Communities

In Australia, asymptomatic heart failure was reported to be 140,000 (26%) in rural and remote communities. (30) Each year, in the Unites States, 400,000 to 460,000 persons die of unexpected sudden cardiac death in an emergency department or before reaching a hospital. (31) Geographical isolation and lack of specialists, as weLl as spiralling institutional costs, an aging population, and increased numbers of people living with chronic illness, identify a need for a community- or home-based approach for effective cardiovascular healthcare. (5) In these groups and in others in high-risk categories, frequent and costly rehospitalizations and a high incidence of mortality could be addressed by home-based intervention. (32)

Home-based intervention by community nurses addresses patients' interest in their health and their desire to be informed with respect to their illness. Chronic problems require continuous monitoring, a need that is not met with traditional consultation processes but is feasible in a multidisciplinary healthcare model. In a study of a nurse-led falls-prevention program that included ECG assessment, 50% of the people assessed were asymptomatic for cardiac pathology but were identified as having abnormal ECG traces. (33)

A 3-lead recording is easy to implement, with electrode placement less critical and the interpretation less demanding than the 12-lead ECG. Telemedicine can be used if additional confirmation of the ECG interpretation is required. A 12-lead ECG can be mathematically described from an orthogonal 3-lead placement that includes leads I, aVF, and [V.sub.2]. Current computer technology performs this calculation instantaneously in real time. A pilot study showed 100% accuracy in differentiating normal from infarction ECGs based on traditional 12-lead evaluation as the gold standard. (34) Cost-effective training options are also available.

Successful integration of ECG assessment in community healthcare is a step toward integrating specialist services with community and primary care practitioners. The shift toward community-based care, particularly in chronic conditions, underscores the importance of empowering community-based clinicians to undertake duties traditionaily in the domain of critical care. Holistic healthcare as part of a community health service is practical and efficient healthcare. Adding 3-lead ECG recordings may improve outcomes for the communities we serve. (5)

Our ECG assessment model is consistent with the current European guidelines on CVD prevention, which seek to achieve a reduction in the incidence of first and recurrent clinical events due to heart disease. (35) As such, we propose that an initial assessment of all patients should include a 3-lead ECG, which is repeated every 2 years. When consultations are provided to patients at increased risk of CVD, ECG assessment can be done more often. This model is an extension of the recommendation by the Australian National Health and Medical Research Council on prevention and detection of macrovascular disease for management of type 2 diabetes mellitus. (36)

Medical expenses and lost productivity from CVD cost an estimated US$138 billion. (37) The cost of ECG recordings and interpretation associated with general practice is an estimated US$250 million annually. (26) Further research is needed to evaluate the cost effectiveness of community nurses using the 3-lead ECG for screening. However, nurse-led primary care initiatives and secondary prevention initiatives have been shown to be cost effective. (38) Coronary artery disease screening in asymptomatic patients has also been shown to be cost effective in people with diabetes with additional atherogenic risk factors. (39) Using nurses with suitable expertise is especially important in isolated practice areas. In summary, based on the data from this study, we have argued that an in-depth assessment of cardiovascular risk factors combined with a 3-lead ECG tracing provides the basis for a more informed patient assessment.

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