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At least 109 records · Page 6Linked to original sources

PubMed2000

Validation of cardiologists' decisions to initiate reperfusion therapy for acute myocardial infarction with electrocardiograms viewed on liquid crystal displays of cellular telephones.

BACKGROUND: The transmission of 12-lead electrocardiograms from remote locations to hand-held computers of cardiologists is now possible with the development of wireless technology and computer software. This investigation determined whether the cardiologist's decisions regarding reperfusion therapy for patients with symptoms suggestive of an acute myocardial infarction are the same when given electrocardiograms displayed on a cellular telephone as on a standard paper recording. METHODS: Cardiologists were given 20 electrocardiograms of patients with acute chest pain suggestive of acute myocardial infarction to test the diagnostic reliability of the Nokia 9000i cellular telephone liquid crystal display (LCD) screen. The cardiologists made their decision to initiate or not initiate reperfusion therapy for the patients after viewing their electrocardiograms displayed on both 5-mm and 1-mm formatted grids and twice on traditional printout electrocardiograms. The control level of intraobserver agreement between the responses from the 2 sets of paper display electrocardiograms was compared with the experimental level of intraobserver agreement between the 1-mm LCD electrocardiograms and both sets of paper display electrocardiograms to determine whether the viewing medium affected the cardiologist's decisions. The 1-mm and 5-mm LCD screen electrocardiograms were compared to determine if the grid size affected the cardiologist's decisions. RESULTS: Ninety-three percent of the 2 sets of paper-guided decisions were in agreement. When comparing the 1-mm LCD-guided decisions with both sets of paper-guided decisions, 94% and 89% of the decisions, respectively, were in agreement. The differences between the control and experimental degrees of intraobserver agreement of 1% and 4% were not statistically significant (P1 =.81, P2 =.29). Ninety-one percent of the 1-mm LCD-guided decisions were in agreement with the 5-mm LCD-guided decisions. CONCLUSIONS: Cardiologists' decisions did not vary significantly when viewing either traditional paper electrocardiograms or LCD screen electrocardiograms. Even though there was not a significant difference in the cardiologists' decisions when they viewed electrocardiograms displayed on both the 1-mm and 5-mm grid, it is recommended that the 1-mm grid be used for clinical implementation of the LCD screen.

Computer Terminals↗

PubMed1996

[Usefulness of the newly developed transtelephonic electrocardiogram and computer-supported response system].

The "Cardiophone System" is a system designed to expand the relationship between patients and medical services using a transtelephonic electrocardiogram and computer-assisted answering system. The transtelephonic electrocardiogram, or so-called "Cardiophone", developed by Nihon Kohden, Inc., allows the patients to carry a "Cardiophone" to record electrocardiograms during paroxysmal occurrences of palpitation, chest pain, and other symptoms. The Cardiophone may function as a terminal of the host computer at the hospital, which stores the electrocardiogram and print it as soon as the computer receives the electrocardiogram over the phone. Cardiologists can examine the electrocardiogram immediately after it is printed. Cardiologists and operators are on duty 24 hours a day. Judgments based on the electrocardiogram are made by the cardiologist on duty, and stored in the computer by the operator. The patients may listen to the judgment over the phone within 30 min of sending the electrocardiogram. In the case of potentially lethal findings on the electrocardiogram, the cardiologist on duty calls the patient directly to give a medical advice. We studied 184 outpatients who were enrolled in the Cardiophone System of our hospital. The average number of transtelephonic electrocardiograms was 10 per day. Abnormal electrocardiographic changes were observed in 42 patients, and the diagnoses were as follows: paroxysmal supraventricular tachycardia in 18 patients, paroxysmal atrial fibrillation in 17, ventricular tachycardia in 3, and angina in 7. Among seven patients in whom ST changes were documented by Cardiophone, six were diagnosed as variant angina. In several patients with diagnoses already made by Holter monitoring, the Cardiophone was used to monitor the drug effects and the correlations between symptoms and arrhythmic events. We conclude that the Cardiophone System is useful for diagnosing the causes of paroxysmal cardiac symptoms in some patients and for improving home medical services.

Adolescent↗

PubMed1985

The yield of the routine admission electrocardiogram. A study in a general medical service.

To evaluate the usefulness of the admission electrocardiogram, we prospectively studied 1410 patients admitted to a general medical service. The patients' history and physical examination were analyzed, and then the electrocardiogram was evaluated to determine whether it added new information. Fifty-two admission electrocardiograms added unique information; 31 established a new diagnosis, 28 of which changed management. Twenty-one electrocardiograms suggested a new diagnosis, 13 of which proved correct. Only age and a clinically evident cardiac abnormality predicted the yield of the admission electrocardiogram. Among patients with cardiac abnormalities, electrocardiogram yield was 8.5% in those 45 years or older and 2.5% in those younger. Among patients without cardiac abnormality, electrocardiogram yield was 1.0% overall and its cost-effectiveness was $24 000 per year of life saved. An admission electrocardiogram infrequently added new information to the clinical evaluation, but was useful when it did. Admission electrocardiograms are as cost-effective as many accepted medical practices.

Adult↗

PubMed2005

Competency in electrocardiogram interpretation among internal medicine and emergency medicine residents.

PURPOSE: Accurate interpretation of the electrocardiogram is critical, yet there are no evidence-based guidelines for assessing competency. Our study evaluated the ability of internal medicine residents and emergency medicine residents to interpret a variety of electrocardiograms. METHODS: The 120 participants included 87 internal medicine residents and 33 emergency medicine residents at two hospitals. Participants reported their sex, training level, adequacy of training, career interest in cardiology, and estimated electrocardiogram proficiency. They then took a test containing 12 electrocardiograms and recorded their diagnosis and certainty. Two cardiologists independently established the correct diagnoses. Two blinded, independent graders scored each electrocardiogram (0 = incorrect, 1 = partially correct, 2 = correct). RESULTS: The median proficiency was 6 out of 10, total electrocardiogram score was 15 of 24, and certainty was 33 of 48. There was no significant difference in overall competency between emergency medicine and internal medicine residents (14.0 vs 15.0, P = 0.239). Internal medicine residents interested in a cardiology career scored higher than those not interested in a cardiology career (17.3 vs. 14.1, P = 0.003). When analyzing the most critical diagnoses, we found that the mean score for ventricular tachycardia was 1.6 of 2.0, for myocardial infarction was 1.3 of 2.0, and for complete heart block was 0.8 of 2.0. Over half of the participants felt their electrocardiogram training was inadequate. CONCLUSION: Despite improvement in interpretation with clinical experience, overall performance was low. Research is needed to find optimal methods to improve electrocardiogram competency.

Career Choice↗

PubMed2006

The prevalence and prognosis of a Brugada-type electrocardiogram in a population of middle-aged Japanese-American men with follow-up of three decades.

BACKGROUND: The Brugada syndrome is an inherited arrhythmogenic and nonstructural heart disease associated with an increased risk of sudden cardiac death from ventricular fibrillation. There are conflicting data about its prevalence and prognosis. Particularly, population-based studies are lacking in the United States and other countries. METHODS: A total of 8006 Japanese-American men aged 45 to 68 years participated in the initial examination of the Honolulu Heart Program during the period of 1965 through 1968. After excluding prevalent cases with coronary heart disease, 864 electrocardiograms coded as right bundle branch block were reviewed using the specified criteria for Brugada-type electrocardiogram. Baseline characteristics and the prognosis of Brugada-type electrocardiogram were compared with 5983 control subjects who had electrocardiograms coded as normal at the initial examination. RESULTS: There were 12 typical cases and 11 atypical cases of Brugada-type electrocardiogram at the initial examination (prevalence, 0.15% and 0.14%, respectively). Analysis of baseline characteristics revealed no difference between control cases and either typical or atypical Brugada-type electrocardiogram cases except significantly lower body mass index in subjects with Brugada-type electrocardiogram. During the 30-year follow-up period, none of the subjects died suddenly within 24 hours after the onset of symptoms. Survival analysis revealed no significant difference between case and control groups. CONCLUSIONS: Brugada-type electrocardiograms among middle-aged or elderly Japanese-American men are uncommon and are not associated with increased risk of either sudden death or total mortality.

Arrhythmias, Cardiac↗

PubMed2002

Electrocardiogram in Pneumocystis carinii pneumonia: can it be used as a prognostic variable?

OBJECTIVE: Many prognostic variables have been studied in patients with Pneumocystis carinii pneumonia and acquired immunodeficiency syndrome (AIDS). The role of the electrocardiogram in this setting has not been previously evaluated. We analyzed the admission electrocardiogram in patients with Pneumocystis carinii pneumonia and AIDS in an attempt to identify electrocardiogram findings that could be associated with adverse clinical outcomes and worse prognostic variables. DESIGN: A retrospective medical chart review. SETTING: All confirmed cases of Pneumocystis carinii pneumonia in patients positive for human immunodeficiency virus admitted to Albert Einstein Medical Center from 1994 to 2000. METHODS: Patients were assigned increasing severity ranks based on the findings on the admission electrocardiogram (normal sinus rhythm, sinus tachycardia, and right ventricular strain pattern). Data were extracted regarding study outcomes (admission to intensive care unit, mechanical ventilation, and hospital mortality) and prognostic variables. MAIN RESULTS: Of the 40 study patients, 14 (35%) had normal sinus rhythm, 15 (37.5%) had sinus tachycardia, and 11 (27.5%) presented with signs of right ventricular strain. The number of admissions to the intensive care unit, use of mechanical ventilation, and hospital mortality rate all increased with the severity of the electrocardiogram findings (p < or =.03). The serum lactate dehydrogenase concentrations and the alveolar-arterial oxygen gradient both increased with the severity of the electrocardiogram findings (p < or =.02). CONCLUSION: Electrocardiogram findings of sinus tachycardia and right heart strain are common in Pneumocystis carinii pneumonia. These findings are associated with adverse clinical outcomes as well as worsening of prognostic variables. The electrocardiogram may be useful in predicting outcome in patients with Pneumocystis carinii pneumonia.

Adult↗

PubMed1988

Time course of ventricular arrhythmias and the signal averaged electrocardiogram in the post-infarction period: a prospective study of correlation.

The incidence and time course of complex ventricular arrhythmias and of the abnormal signal averaged electrocardiogram were studied prospectively in 90 patients in the first two months after acute myocardial infarction. Serial recordings of both 24 hour ambulatory and signal averaged electrocardiograms were obtained 0-5 days (phase 1), 6-30 days (phase 2), and 31-60 days (phase 3) after infarction. A total of 264 ambulatory electrocardiograms and 264 signal averaged electrocardiograms were available for analysis. Complex ventricular arrhythmias were seen in 31%, 17%, and 38% of patients during phases 1, 2, and 3 respectively, and abnormal signal averaged electrocardiogram in 13%, 24%, and 16%. The incidence of complex ventricular arrhythmias was not significantly different in patients with or without an abnormal signal averaged electrocardiogram in the entire study period nor in any of the three phases after infarction. During phase 2 when abnormal signal averaged electrocardiograms were most common complex ventricular arrhythmias were least common. This lack of correlation suggests that the abnormal signal averaged electrocardiogram and complex ventricular arrhythmias after infarction have different electrophysiological bases.

Adult↗

PubMed1995

Familial sudden death syndrome with an abnormal signal-averaged electrocardiogram as a potential marker.

Most familial sudden cardiac death syndromes are associated with structural heart disease or 12-lead electrocardiographic abnormalities. Additionally, the utility of signal-averaged electrocardiograms in patients with familial sudden death syndromes has not been examined. We studied a kindred with sudden death to determine whether they could be classified into any of the previously described syndromes and whether an abnormal signal-averaged electrocardiogram is a marker for this trait. Surviving family members had normal 12-lead electrocardiograms and echocardiograms. Two of the patients who died from ventricular arrhythmias had normal hearts on autopsy. Two surviving family members had a clinical history of arrhythmic events; both had abnormal signal-averaged electrocardiograms and inducible ventricular arrhythmias during electrophysiologic studies. The other family members had normal signal-averaged electrocardiograms. This familial sudden death syndrome appears to be unique because the patients have anatomically normal hearts and normal 12-lead electrocardiograms. An abnormal signal-averaged electrocardiogram may be a marker for the sudden death trait.

Adult↗

PubMed1995

The initial electrocardiogram pattern is a strong predictor of outcome in acute myocardial infarction.

We analyzed the significance of the initial electrocardiogram on the clinical outcome of 205 consecutive patients with a first myocardial infarction. Three different patterns of the electrocardiogram were defined: (A) Tall symmetric T waves in the involved leads; (B) ST segment elevation > 0.1 mV in two or more adjacent leads; and (C) ST segment elevation together with distortion of the terminal portion of the QRS complex in two or more adjacent leads. Twelve patients were considered to have an initial 'A' electrocardiogram, 151 an initial 'B' electrocardiogram, and 42 an initial 'C' electrocardiogram. Four factors were significantly related to mortality: age, ST, Killip class and electrocardiographic pattern. The mortality rate was 0% in group A, 7.9% in group B, and 26.2% in group C (P = 0.0019). Patients with type C electrocardiograms had a significantly worse Killip classification and a significantly higher sum of ST segment elevation. Among patients with inferior infarction, the mortality rate was 1.4% in type B vs. 24.1% in type C (P = 0.0005). Among patients with anterior infarction, the mortality rate was 13% in type B vs. 30.8% in type C (P = 0.089). We conclude that the pattern of the initial electrocardiogram is a strong predictor of outcome in acute myocardial infarction, especially if it is inferior.

Adult↗

PubMedDate not supplied

The electrocardiogram in acute pulmonary embolism.

Electrocardiograms of 90 patients with arteriographically documented acute submassive or massive pulmonary embolism and no associated cardiac or pulmonary disease were studied. Patients were derived from the Urokinase-Pulmonary Embolism Trial National Cooperative Study. In massive embolism, the electrocardiogram was normal in 6 per cent (3 of 50) of patients. With submassive embolism, 23 per cent of patients (9 of 40) had a normal electrocardiogram. Since one or more of the traditional manifestations of acute cor pulmonale (S1Q3T3, right bundle branch block, P pulmonale, or right axis deviation) occurred in only 26 per cent of patients, one could not rely exclusively upon these electrocardiographic abnormalities for the diagnosis of pulmonary embolism. The most common electrocardiographic abnormalities were nonspecific T wave changes which occurred in 42 per cent of patients and nonspecific abnormalities (elevation or depression) of the RST segment which occurred in 41 per cent of patients. Left axis deviation occurring in 7 per cent of the patients was as frequent as right axis deviation. Low voltage QRS complexes, previously undescribed in pulmonary embolism, occurred in 6 per cent of patients. None of the patients had atrial flutter or atrial fibrillation, which appears to occur more typically in patients with pulmonary embolism who have preexistent cardiac disease. All of the varieties of electrocardiographic abnormalities disappeared in some of the patients by 2 wk. Inversion of the T wave was the most persistent abnormality. Larger defects on the lung scan or pulmonary arteriogram occurred in patients with various abnormalities on the electrocardiogram than in patients with normal electrocardiograms. The pulmonary arterial mean pressure and/or right ventricular end-diastolic pressure was significantly higher in patients with several varieties of abnormal electrocardiograms, although the partial pressure of oxygen in arterial blood, in general, did not differ from that in patients with normal electrocardiograms. These hemodynamic correlations, made for the first time in patients, suggest that acute ventricular dilatation, possibly in combination with hypoxemia, is a causative factor of the electrocardiographic changes in acute massive or submassive pulmonary embolism.

Acute Disease↗

PubMed1997

Should general practitioners use the electrocardiogram to select patients with suspected heart failure for echocardiography?

Patient referrals from general practice for suspected heart failure are increasing the demand for echocardiograms, many of which are normal. We investigated whether general practitioners could be more selective by referring only patients with abnormal electrocardiograms for echocardiography. The electrocardiograms of 200 patients attending a heart failure clinic were analysed by a consultant cardiologist and two general practitioners. All three assessors examined the electrocardiograms independently and unaware of the echocardiography results. The correlation between abnormal electrocardiograms and left ventricular systolic dysfunction on echocardiography was assessed, together with the concordance between the assessors in their electrocardiogram interpretations. One hundred and sixty-five patients had echocardiographic evidence of left ventricular systolic dysfunction. When interpreted by a cardiologist, the electrocardiogram had a sensitivity of 89.1% and a specificity of 45.7% in predicting left ventricular systolic dysfunction. The general practitioners' results were comparable to the cardiologist's. We estimate that using the electrocardiogram to select patients could reduce the number of open access echocardiograms performed for suspected heart failure by up to 43% but would miss 10% of those with significant left ventricular systolic dysfunction. We therefore do not recommend selecting patients for open access echocardiography on the basis of electrocardiographic abnormalities.

Clinical Competence↗

PubMed2002

Longitudinal estimation of signal-averaged electrocardiograms in patients with Kawasaki disease.

BACKGROUND: Myocarditis associated with Kawasaki (KD) disease is prominent, but rarely detected by conventional methods. The hypothesis of this study is to see if signal-averaged electrocardiogram can detect myocarditis with KD. METHODS: We obtained signal-averaged electrocardiograms from 71 patients with KD (mean age 2.8 +/- 2.9 years) in the acute (1st-4th week), subacute (5-7th week), and chronic (8th week or later) phases (mean study period 3.5 +/- 1.7 years). Sixteen patients who had pericardial effusion, bundle branch block or myocardial ischemia were excluded from this study. The results were compared with those of Holter and 12-lead electrocardiograms, echocardiography and serum myocardial enzymes. They were also contrasted with the course of each patient. RESULTS: The incidence of abnormal findings on signal-averaged electrocardiogram was 18.2% in the acute phase versus 10.9% in the subacute and chronic phases. It differed significantly higher than the other conventional tests (P < 0.05). Four patients had abnormalities of signal-averaged electrocardiograms through all three phases. Among these four, two had reduced left ventricular contractility. However, these changes were transient and resolved in the subacute phase. All patients had good courses and no residue. CONCLUSION: This study shows the possibility that signal-averaged electrocardiogram is more useful to detect myocarditis associated with KD than the other conventional tests. However, we could not define the prognostic value of abnormal signal-averaged electrocardiograms during this study period.

Adolescent↗

PubMed2001

The cumulative effects of historical and physical examination findings on the prognostic value of the electrocardiogram.

The electrocardiogram has been shown in epidemiologic studies to be an independent predictor of survival. These studies have adjusted for selected covariates simultaneously. This article assesses the value of the electrocardiogram as a predictor of survival when introduced at progressive stages of the common clinical encounter. Data collected from 4,518 patients ages of 60 to 96 years with isolated systolic hypertension who were followed-up for up to 6 years as part of the Systolic Hypertension in the Elderly Project were analyzed. Survival curves and 3- and 5-year survival rates (Cox regression methods) of groups with normal and abnormal resting electrocardiograms were compared. Blocks of covariates representing demographic information, risk factors for cardiovascular disease, clinical history, and physical examination findings were added to the survival models sequentially to mimic the sequence of the common clinical encounter, and the independent significance of the electrocardiogram as a predictor of survival was assessed at each step. An abnormal electrocardiogram was associated with reduced survival when no adjustment for covariates is made. Survival was also significantly (P <.05) different for groups with normal and abnormal electrocardiograms when demographic and risk factor variables were included in the statistical models, but not after findings from the clinical history and physical examination were added. The prognostic value of the electrocardiogram varies with the stage in the clinical encounter in which it is introduced.

Aged↗

PubMed1985

Use of the initial electrocardiogram to predict in-hospital complications of acute myocardial infarction.

We evaluated the initial electrocardiogram as a predictor of complications in 469 patients with suspected acute myocardial infarction. An electrocardiogram was classified as positive if it showed one or more of the following: evidence of infarction, ischemia, or strain; left ventricular hypertrophy; left bundle-branch block; or paced rhythm. Forty-two (14 per cent) of 302 patients with positive electrocardiograms had at least one life-threatening complication (ventricular fibrillation, sustained ventricular tachycardia, or heart block), as compared with 1 (0.6 per cent) of 167 patients with a negative electrocardiogram. Life-threatening complications were therefore 23 times more likely if the initial electrocardiogram was positive (P less than 0.001). Other complications were 3 to 10 times more likely (P less than 0.01), interventions were 4 to 10 times more likely (P less than 0.05), and death was 17 times more likely (P less than 0.001) in patients with a positive electrocardiogram. We conclude that patients with a negative initial electrocardiogram have a low likelihood of complications and could be admitted to an intermediate care unit instead of a coronary care unit. This would reduce admissions to the coronary care unit by 36 per cent and thereby save considerable hospital costs without compromising patient care.

Connecticut↗

PubMed1987

Value of the resting 12 lead electrocardiogram and vectorcardiogram for locating the accessory pathway in patients with the Wolff-Parkinson-White syndrome.

The resting 12 lead electrocardiogram and vectocardiogram were reviewed in 47 patients with the Wolff-Parkinson-White syndrome (a) who had pre-excitation on the resting 12 lead electrocardiogram, (b) who had a single anterograde conducting accessory pathway assessed and located during preoperative electrophysiological study and during epicardial mapping at operation, and (c) in whom surgical division of the accessory pathway resulted in loss of pre-excitation. The site of the accessory pathway established during operation was compared with that established by evaluating the polarity of the delta wave and QRS complex on the resting 12 lead electrocardiogram. The electrocardiogram was assessed by the Rosenbaum criteria (Wolff-Parkinson-White type A, left-sided pathway; or type B, right-sided pathway), the Gallagher criteria (atrial pacing resulting in maximal pre-excitation), and the World Health Organisation criteria (a composite of previous studies). The Gallagher and World Health Organisation criteria were derived from patients demonstrating maximal pre-excitation that often required atrial pacing. The present study was designed to determine whether these criteria could be accurately applied to the resting 12 lead electrocardiogram on which the degree of pre-excitation was variable. The Rosenbaum criteria correctly identified a left sided accessory pathway in 26 of 34 patients and a right-sided accessory pathway in nine of 13 patients. The Gallagher and World Health Organisation criteria correctly identified the location in only 15 (32%) of the 47 patients. The resting vectorcardiogram was inaccurate for locating the accessory pathway. Although published criteria are useful for identifying the site of the accessory pathway from an electrocardiogram obtained when rapid atrial pacing is being used to achieve maximal pre-excitation, they are not suitable for identifying the exact site of an accessory pathway from the resting 12 lead electrocardiogram.

Adolescent↗

PubMed1994

Comparison of the value of novel rapid measurement of myoglobin, creatine kinase, and creatine kinase-MB with the electrocardiogram for the diagnosis of acute myocardial infarction.

OBJECTIVE: To determine whether serum myoglobin, creatine kinase, and creatine kinase-MB measured at admission by rapid, compact, and easy to use automated quantitative analysers (results within 10 min) helped the early identification of acute myocardial infarction. The results were compared with the data obtained from the electrocardiograms recorded at admission. DESIGN: A prospective study. SETTING: Coronary care unit. PATIENTS: 94 consecutive patients with suspected myocardial infarction. Myocardial infarction was subsequently confirmed in 44 patients and excluded in 50. METHODS: All admission serum myoglobin, creatine kinase, and creatine kinase-MB were measured by clinical staff using analysers in the coronary care unit. An admission electrocardiogram was obtained from all patients. RESULTS: The sensitivity, specificity, and predictive accuracy for diagnosing myocardial infarction were: electrocardiogram 68%, 100%, and 85%; myoglobin 57%, 100%, and 80%; creatine kinase (threshold of 190 U/l) 34%, 98%, and 68%; creatine kinase-MB (threshold of 25 U/l) 43%, 100%, and 73%. When the electrocardiographic and myoglobin data were combined the sensitivity improved to 91%, diagnostic accuracy to 96%, with specificity of 100%. The results for the electrocardiogram and creatine kinase-MB were 80%, 90%, 100% respectively and those for the electrocardiogram with creatine kinase were 80%, 89%, 98% respectively. CONCLUSIONS: Admission myoglobin, creatine kinase, and creatine kinase-MB measurements were not as useful as the electrocardiogram for the diagnosis of acute myocardial infarction. Combining the electrocardiogram and myoglobin data substantially improved the sensitivity and predictive accuracy for the diagnosis of acute myocardial infarction.

Blood Chemical Analysis↗

PubMed1994

Adjustment of QT dispersion assessed from 12 lead electrocardiograms for different numbers of analysed electrocardiographic leads: comparison of stability of different methods.

OBJECTIVE: Normal electrocardiographic recordings were analysed to establish the influence of measurement of different numbers of electrocardiographic leads on the results of different formulas expressing QT dispersion and the effects of adjustment of QT dispersion obtained from a subset of an electrocardiogram to approximate to the true QT dispersion obtained from a complete electrocardiogram. SUBJECTS AND METHODS: Resting 12 lead electrocardiograms of 27 healthy people were investigated. In each lead, the QT interval was measured with a digitising board and QT dispersion was evaluated by three formulas: (A) the difference between the longest and the shortest QT interval among all leads; (B) the difference between the second longest and the second shortest QT interval; (C) SD of QT intervals in different leads. For each formula, the "true" dispersion was assessed from all measurable leads and then different combinations of leads were omitted. The mean relative differences between the QT dispersion with a given number of omitted leads and the "true" QT dispersion (mean relative errors) and the coefficients of variance of the results of QT dispersion obtained when omitting combinations of leads were compared for the different formulas. The procedure was repeated with an adjustment of each formula dividing its results by the square root of the number of measured leads. The same approach was used for the measurement of QT dispersion from the chest leads including a fourth formula (D) the SD of interlead differences weighted according to the distances between leads. For different formulas, the mean relative errors caused by omitting individual electrocardiographic leads were also assessed and the importance of individual leads for correct measurement of QT dispersion was investigated. RESULTS: The study found important differences between different formulas for assessment of QT dispersion with respect to compensation for missing measurements of QT interval. The standard max-min formula (A) performed poorly (mean relative errors of 6.1% to 18.5% for missing one to four leads) but was appropriately adjusted with the factor of 1/square root of n (n = number of measured leads). In a population of healthy people such an adjustment removed the systematic bias introduced by missing leads of the 12 lead electrocardiogram and significantly reduced the mean relative errors caused by the omission of several leads. The unadjusted SD was the optimum formula (C) for the analysis of 12 lead electrocardiograms, and the weighted standard deviation (D) was the optimum for the analysis of six lead chest electrocardiograms. The coefficients of variance of measurements of QT dispersion with different missing leads were very large (about 3 to 7 for one to four missing leads). Independently of the formula for measurement of QT dispersion, omission of different leads produced substantially different relative errors. In 12 lead electrocardiograms the largest relative errors (> 10%) were caused by omitting lead aVL or lead V1. CONCLUSIONS: Because of the large coefficients of variance, the concept of adjusting the QT dispersion for different numbers of electrocardiographic leads used in its assessment is difficult if not impossible to fulfil. Thus it is likely to be more appropriate to assess QT dispersion from standardised constant sets of electrocardiographic leads.

Adult↗

PubMed2003

The interpretation of the electrocardiogram in patients with pulmonary hypertension: the need for clinical correlation.

BACKGROUND: The detection and treatment of pulmonary hypertension have become increasingly important for the clinician. While the electrocardiogram is often used as a screening tool in patients suspected of having pulmonary hypertension, the sensitivity for detecting right ventricular hypertrophy in the era of computerized electrocardiogram analysis is highly suspect. The aim of the study was to determine the importance of clinical information in providing an accurately edited electrocardiographic system. METHODS: The interpretation of the electrocardiograms of 64 consecutive symptomatic patients (12 males, 52 females, mean age 43 +/- 13 years) with isolated pulmonary hypertension provided by the computer program and the cardiologist following editing during routine daily reading sessions were reviewed. The reader (blinded cardiologist) was unaware of the clinical diagnosis. Subsequently, a cardiologist given clinical information regarding age and symptoms, edited the computer interpretation. RESULTS: The unblinded cardiologist diagnosed right axis deviation > 90 degrees, right ventricular hypertrophy, right ventricular strain, and right atrial enlargement in 76.6, 78.1, 71.9 and 20.3% of patients, respectively. In 6 (9.4%) patients, the electrocardiogram was normal. The blinded cardiologist and computer program diagnosed right ventricular hypertrophy in 43.8 and 39.1% respectively and most often characterized right ventricular strain as non-specific or inferior or as antero-lateral ischemia. CONCLUSIONS: The electrocardiogram has a high degree of sensitivity for the detection of abnormalities in symptomatic patients with isolated pulmonary hypertension. Correlation with the clinical parameters is essential to optimize the usefulness of the electrocardiogram. Consideration should be given to tailoring computerized electrocardiogram interpretative software to clinical information.

Adolescent↗