Routine 12-lead Electrocardiogram Research Articles

Standardizing electrocardiographic leads: introduction to a symposium

Since Einthoven introduced the string galvanometer in 1902, electrocardiography has evolved as one of the most widely used tests in the practice of medicine. The routine 12-lead electrocardiogram (ECG), comprising limb leads, augmented frontal plane leads, and precordial leads, has been standardized for half a century. Routine electrocardiography is a fundamental tool for establishing cardiac rhythm and for the diagnosis of acute and chronic diseases of the heart. Comparison of serial ECGs is important in clinical decision making, and this requires technical consistency to minimize nonbiologic variability. Important elements of technical consistency include choice of leads and accuracy of electrode placement. To identify Q waves of prior myocardial infarction and to quantify QRS amplitudes to diagnose ventricular hypertrophy, proper lead placement of the standard electrodes can be extremely important. Electrode placement can have a profound effect on the quantitative variability of serial ECG findings. For example, to evaluate changing ST-segment deviation in patients with acute coronary syndromes, consistent electrode placement is essential. For most rhythm diagnoses, precise lead placement is less critical, but electrode placement is important when QRS morphology is used to determine whether a wide QRS complex tachycardia is ventricular tachycardia or supraventricular tachycardia with aberrancy or bundle branch block. Before the modern era of acute coronary care and hospital-based monitoring and telemetry, nearly all ECGs recorded in the course of practice used a standard 12-lead electrode array that evolved by empirical consensus in the 1930s and 1940s. Early exercise tests conducted with the master 2-step protocol used supine limb lead tracings recorded before and after effort, but exceptions began to occur in the last third of the 20th century when bipolar torso electrodes were introduced to allow activity-compatible

Pseudo Pacemaker Stimuli

Current electrocardiographic technology is limited in its ability to detect pacemaker stimuli secondary to the use of 150 Hz low-pass bandwidth filters designed to block high-frequency interference. Software solutions to improve the sensitivity of pacemaker stimulus detection are associated with imperfect specificity. The following case reports include three patients who do not have a pacing device, but were identified by a computer-based preliminary interpretation of a routine 12-lead surface electrocardiogram (ECG) as having a paced rhythm.

Trigeminy transformed into allorhythmic triplets

The patient was a 79-year-old woman with chronic coronary artery disease who was seen in the cardiology clinic for increasing angina pectoris. She was asymptomatic at the time. Her routine 12-lead electrocardiogram is shown in Fig 1. The first impression of the electrocardiogram is that there is an overall tachycardia, approximately 108 beats/min. Regular sinus P waves can be mapped throughout, at the rate of 79 beats/min to 82 beats/min, but every third sinus cycle sandwiches an additional beat, producing an allorhythmic triplet. Allorhythmia is a regularly recurring irregularity, named and defined by Sommerbrodt in 1877. 1 This patient’s allorhythmia consists of triplets separated by 2 normal sinus cycles. The extra beat, flanked by sinus beats in each triplet, is only minimally different from its neighbors: They all have the same basic left bundle branch block morphology. The difference may be because of the variation in the intraventricular conduction imposed by different cycle lengths; even the flanking sinus beats are not exactly identical. The complex in the middle, however, may also be different because of its junctional origin, what Schamroth called nonphasic aberrant ventricular conduction. 2 Although the phasic variety involves long– short cycle sequences, this allorhythmia is predicated on the different wave-front when spreading from a junctional focus. It can be seen in both junctional escape and premature beats as a slight but constant variation of the basic supraventricular morphology.

Prevalence of the Brugada-Type ECG Recorded From Higher Intercostal Spaces in Healthy Korean Males

Electrocardiograms (ECGs) recorded from the higher intercostal spaces (ICSs) are reported to be helpful for the diagnosis of Brugada syndrome (BS). However, the prevalence of Brugada-type ECG changes recorded from the higher ICSs is unknown in the healthy Korean population. A total of 225 healthy Korean male subjects with a mean age of 44+/-13 (20-69) years with no syncope or family history of sudden death were enrolled in the present study. ECGs were taken from 4th, 3rd, and 2nd ICSs and examined for Brugada-type ECG changes. There were none on the routine 12-lead ECGs, but 3 (1.3%) of the 225 subjects had a Brugada-type ECG recorded from the higher ICSs and 1 of them had a Brugada-type ECG recorded at both the 2nd and 3rd ICSs. The prevalence of the Brugada-type ECG was 1.3% at the 3rd ICS, 0.4% at the 2nd ICS. All were type 2. Some healthy Korean males with normal routine ECGs show Brugada-type 2 changes on ECGs recorded from higher ICSs.

Narrow capture beat

The patient was a 70-year-old man admitted with an ischemic left foot and a thrombosed popliteal aneurysm. He had a history of successful coronary artery bypass grafts and abdominal aortic aneurysm repair. No symptoms apart from the leg pain were present on admission. His routine 12-lead electrocardiogram (ECG) is shown in Fig 1.

The effect of beta adrenergic stimulation on QT and QTc interval in syncope children with or without coexisting ventricular arrhythmias.

We investigated the effect of beta-adrenergic stimulation on the heart rate and QT interval in syncope children with or without coexisting ventricular arrhythmias (VA). Of the 24 children who presented with syncope or presyncope and showed negative tilt test, 13 were classified into a group with VA and the remaining 11 without VA. The provocative test was performed in bolus infusion and continuous infusion. RR, QT, and QTc intervals on routine 12-lead surface electrocardiogram were obtained during each stage of isoproterenol infusion. In all cases, malignant ventricular arrhythmia and syncope were not induced by isoproterenol provocative test. RR and QT intervals were shortened and QTc intervals were prolonged as the isoproterenol dose was increased in both groups and methods. The QTc interval reached its peak level after the bolus injection of 1.0 microgram and during the continuous infusion of 0.03 microgram/kg/min. The two groups showed no significant difference in the QTc interval change according to the infusion methods. This study indicates that changes in the heart rate and QT interval by beta-adrenergic stimulation were not different according to the coexisting ventricular arrhythmias in syncope children with negative head-up tilt test.

Angioplasty decreases prolonged QT dispersion in patients with angina pectoris but not in patients with prior myocardial infarction.

Prolonged QT dispersion (QTd) is shortened by successful percutaneous transluminal coronary angioplasty (PTCA) in patients with ischemic heart disease. Particularly, QTd plays an important role in the prognostication in patients with prior myocardial infarction (MI). However, whether the effect of PTCA on QTd differs in patients with and without prior MI is not clear, and this study sought to clarify this question. In 41 consecutive patients with ischemic heart disease, we measured QTd from a routine 12-lead electrocardiogram taken at 72 h before and after successful PTCA. Patients were divided into two groups based on the presence or absence of prior MI: Group 1 consisted of 24 patients with angina (61 +/- 11 years old) without prior MI and Group 2 was comprised of 17 patients (69 +/- 10 years old) with prior MI. QTd was calculated as the difference between the maximum and minimum QT and QT corrected for heart rate (QTc), using Bazett's formula for calculating QTcd. All measurements were obtained manually and blindly. In Group 1, 15 of 24 patients (63%) demonstrated multivessel disease and 16 of 24 (67%) patients had high QTd > 60 ms. Percutaneous transluminal coronary angioplasty decreased QTd and QTcd in Group 1 (QTd, from 83 +/- 35 to 57 +/- 19 ms, p < 0.05 ; QTcd, from 89 +/- 37 to 63 +/- 33 ms, p < 0.05), whereas no changes were observed in Group 2 (QTd, from 73 +/- 25 to 69 +/- 22 ms, NS; QTcd, from 80 +/- 30 to 79 +/- 28 ms, NS). QTd is more sensitive to decrease by successful PTCA in patients with angina than in patients with prior MI. The effect of successful PTCA on inhomogeneity of ventricular repolarization reflected by QTd in patients with prior MI is different from that in patients without prior MI.

Effect of ambulance 12-lead ECG recording on times to hospital reperfusion in acute myocardial infarction.

To review the evidence that recording a prehospital 12-lead electrocardiogram (ECG) reduces time from hospital arrival to initiation of reperfusion therapy for acute myocardial infarction (AMI). Medline search from 1966 to the present (articles in all languages) and examination of bibliographies. Published studies of prehospital 12-lead ECG recording that included control groups and reported time intervals from hospital arrival to start of reperfusion therapy. Eight articles satisfied selection criteria (two randomised controlled trials, four non-randomised interventional studies and two prospective observational studies). Widely varying study methodologies precluded meta-analysis. All studies had methodological problems, but hospital delays were consistently reduced. Such improvements appear to be small in hospitals where delays are already minimal. Little evidence is available to support routine prehospital 12-lead ECG recording if the median hospital time to reperfusion is already less than 30 minutes. Improvement of in-hospital treatment times may be a better initial strategy than prehospital 12-lead ECG recording, as this will benefit more patients and allow ambulance services to better allocate their available resources.

Improved detection of posterior myocardial wall ischemia with the 15-lead electrocardiogram

Background: A routine 12-lead electrocardiogram is commonly obtained to evaluate for possible acute myocardial infarction during the initial screening of patients with chest discomfort. Posterior myocardial infarction is commonly missed because it is not usually visible in the standard leads. In this study, we compared the sensitivity and specificity of posterior chest leads (V7, V8, and V9) and 12-lead electrocardiography in detecting posterior injury pattern during single-vessel percutaneous transluminal coronary angioplasty. Methods and Results: Three posterior chest leads in addition to the routine 12-lead electrocardiogram were monitored simultaneously during single-vessel percutaneous transluminal coronary angioplasty of the right, circumflex, and left anterior descending coronary arteries in a total of 223 patients. Posterior injury patterns (95%) were detected mostly during circumflex coronary occlusion. Posterior leads were able to detect injury pattern in 49% (36 of 74) of patients, whereas the 12-lead electrocardiogram was able to detect only 32% (P < .04). When all 15 leads were used to detect all ST elevations, sensitivity increased to 57%, with a specificity of 98% for the circumflex coronary artery. If maximal ST depressions in leads V2 to V3 are considered to be from posterior myocardial injury, then the overall sensitivity is increased to 69%. Conclusions: Posterior leads significantly increased the detection of posterior injury pattern compared with the standard 12-lead electrocardiogram. Using all 15 leads significantly further improved the detection of circumflex coronary–related injury pattern over the standard 12-lead electrocardiogram. (Am Heart J 1999;138:934-40.)

Importance of Posterior Chest Leads in Patients with Suspected Myocardial Infarction But Nondiagnostic, Routine 12-Lead Electrocardiogram

Importance of Posterior Chest Leads in Patients with Suspected Myocardial Infarction But Nondiagnostic, Routine 12-Lead Electrocardiogram

Importance of posterior chest leads in patients with suspected myocardial infarction, but nondiagnostic, routine 12-lead electrocardiogram

Criteria for reperfusion therapy in acute myocardial infarction require the presence of ST elevation in 2 contiguous leads. However, many patients with myocardial infarction do not show these changes on a routine 12-lead electrocardiogram and hence are denied reperfusion therapy. Posterior chest leads (V 7 to V 9) were recorded in 58 patients with clinically suspected myocardial infarction, but nondiagnostic routine electrocardiogram. ST elevation >0.1 mV or Q waves in ≥2 posterior chest leads were considered to be diagnostic of posterior myocardial infarction. Eighteen patients had these changes of posterior myocardial infarction. All 18 patients were confirmed to have myocardial infarction by creatine phosphokinase criteria or cardiac catheterization. Of the 17 patients who had cardiac catheterization, 16 had left circumflex as the culprit vessel. We conclude that posterior chest leads should be routinely recorded in patients with suspected myocardial infarction and nondiagnostic, routine electrocardiogram. This simple bedside technique may help proper treatment of some of these patients now classified as having unstable angina or non–Q-wave myocardial infarction.

Clinical and echocardiographic findings in patients with suspected acute aortic dissection

Objectives The objective of this study was to define the range of clinical presentations, echocardiographic findings, and underlying final diagnoses in patients with clinically suspected acute aortic dissection. Methods and Results This study was designed as a retrospective review of clinical and echocardiographic data in consecutive patients evaluated for clinically suspected acute aortic dissection. The study population consisted of 75 studies in 74 consecutive patients referred for urgent or emergency evaluation because of signs and symptoms suggesting acute aortic dissection. A history and physical examination designed to elicit the cause of chest pain, evidence of congestive heart failure, and other cardiovascular abnormalities was performed in each patient. All patients underwent transesophageal echocardiography by experienced operators. Routine 12-lead electrocardiograms and chest radiographs were available for review in the majority of patients. Magnetic resonance imaging or computed tomography was performed in only 5 (6%) and 34 (44%) patients, respectively. Contrast aortography was performed in 21 (27%) patients. For the entire patient cohort, the most prevalent symptom was chest pain alone ( n = 31; 41%) or chest pain in conjunction with back pain ( n = 23; 31%). Classic “tearing” pain was an infrequent symptom. Syncope or other neurologic findings were present in 15 (20%) patients. Acute aortic dissection was responsible for 34 (45%) of the 75 presentations, with 31 (41% of total evaluations, 92% of dissections) involving the ascending aorta (Stanford type A, DeBakey type 1 or 2). Alternate major cardiovascular diagnoses, including acute myocardial infarction, primary valvular disease, or pericardial disease, were established in 12 (16%) cases. Aortic pathology, other than dissection, was found in 15 (20%) cases. Transesophageal echocardiography established the diagnosis responsible for the symptoms in 61 (81%) cases. Conclusions Symptoms in patients with acute aortic dissection are more variable than commonly recognized. Transesophageal echocardiography is an accurate primary diagnostic tool in patients with clinically suspected acute aortic dissection. It allows rapid diagnosis of dissection and can identify alternate cardiovascular pathology responsible for the symptoms in a significant number of patients without acute dissection. (Am Heart J 1998;136:1051-60.)

Usefulness of Echocardiography in Detecting Left Ventricular Dysfunction in Population-Based Studies (The Rotterdam Study)

In a population-based study, the routine 12-lead electrocardiogram was found to have a high negative predictive value for detecting left ventricular (LV) systolic dysfunction. Withholding echocardiography in persons without major electrocardiographic abnormalities, however, would result in a considerable underestimation of LV systolic dysfunction (sensitivity only 54%); thus, echocardiography remains an essential tool for detecting LV systolic dysfunction in population-based studies.

Late sudden cardiac death in the follow-up of patients having a heart valve prosthesis

Eight hundred thirty-one patients with Björk-Shiley prostheses (341 aortic, 345 mitral, and 145 double) had a mean follow-up time of 68.2 months per patient. Of these, 24 (16% of all deaths) died suddenly: six of 42 with aortic valve replacement (14.3%), 12 of 56 with mitral valve replacement (21.4%), and six of 36 with double valve replacement (16.6%). This correlated with evidence of premature ventricular complexes detected in multiple routine 12-lead follow-up electrocardiograms (p less than 0.001 for simple aortic or mitral valve replacements and p less than 0.01 for combined aortic and mitral valve replacements). Premature ventricular complexes were significantly more frequent among those who died suddenly than among survivors and those who died of other causes (p less than 0.001 in both cases); there were no significant differences between the latter two groups. The actuarial risk of sudden death was significantly greater among those patients who had premature ventricular complexes than among those who did not have this disorder (p = 0.0002). We conclude that the presence of premature ventricular complexes, as an independent variable, was correlated with the risk of sudden death.

Perioperative myocardial ischaemia and infarction in non-cardiac surgical patients

Summary Cardiovascular morbidity and mortality associated with non-cardiac surgery increase with the probability and severity of coronary artery disease in the surgical population. In the absence of coronary artery disease, the risk of a perioperative cardiac event is negligible. Preoperative evaluation of patients should always include a thorough history and clinical examination but specific investigations should be individualized as false-positive results are common when the incidence of coronary artery disease is low. Recent myocardial infarction, symptoms suggestive of unstable angina and the presence of heart failure are powerful predictors of perioperative cardiovascular morbidity. A routine 12-lead electrocardiogram should be obtained for all men over 40 years and for all women over 55 years as well as for all patients with a history suggestive of heart disease. Stress testing, with or without thallium, is useful for patients with peripheral vascular disease, and dipyridamole-thallium imaging may be of value in risk stratification for those patients in whom adequate exercise levels cannot be achieved. The risk of a cardiovascular event during surgery can be stratified using a ‘risk index’. Coronary angiography allows precise definition of the coronary anatomy and accurate assessment of left ventricular function but this is usually reserved for patients with severe symptoms or for those found to be at high risk as a result of provocative testing, where it is felt that revascularization of the myocardium may be indicated before the proposed surgery. Every effort should be made to treat any reversible risk factors that arepresent (unstable angina, heart failure, etc.) before surgery, with the aim of decreasing perioperative morbidity and mortality. In general, all cardiac medications should be continued throughout the perioperative period unless specific complications occur necessitating their withdrawal. Throughout the stress of the perioperative period myocardial oxygen delivery must be maintained while myocardial oxygen consumption should be kept at a low level. Myocardial ischaemia is common in patients with coronary artery disease during anaesthetic inducation and perioperative infarction occurs largely in those patients who develop significant tachycardia, hypotension or hypertension during surgery, the risk of infarction being increased three-fold when perioperative ischaemia occurs. Monitoring of the cardiac rhythm, arterial pressure, ST segment changes and, in high-risk patients, more sophisticated parameters of cardiac function, will allow for the early diagnosis of myocardial ischaemia and allow therapy to be monitored. Anaesthetic risk cannot be eliminated but can be minimized. The anaestheticagents and technique can be tailored to a patient's cardiovascular status but much will also depend on the anaesthetist's experience and expertise. Even with the best management there will be circumstances when myocardial ischaemia and infarction will occur and successful management will depend upon recognition and treatment. Careful monitoring can help diagnose myocardial ischaemia but infarction may be difficult to diagnose unless there is a high index of suspicion. It is often not possible to obtain a history and the standard investigations such as the 12-lead electrocardiogram and cardiac enzymes can be difficult to interpret. Radionuclide techniques and echocardiography can be helpful. The initial treatment of myocardial ischaemia and infarction in the perioperative period is identical, with nitrates, β-blocking drugs, aspirin and calcium antagonists being used. Thrombolytic therapy is contraindicated during and immediately after surgery. A combination of improved anaesthetic agents and techniques, togetherwith advances in the treatment of coronary artery disease, appear to be making surgery safer for patients with heart disease.

Usefulness of noninvasive doppler measurement of ascending aortic blood velocity and acceleration in detecting impairment of the left ventricular functional response to exercise three weeks after acute myocardial infarction

Left ventricular (LV) function was assessed by Doppler ultrasound measurement of ascending aortic blood velocity and maximal acceleration in 165 patients 3 to 4 weeks after acute myocardial infarction (AMI); all were undergoing routine 12-lead electrocardiogram exercise stress testing. Patients were grouped according to electrocardiographic stress test response; a positive response was defined as at least 1 mm of ST-segment depression in any lead. The Doppler velocity signal yielded 3 variables of interest: peak velocity, maximal acceleration (an index of inotropic state) and the systolic velocity integral (an index of stroke volume). All 3 Doppler ejection variables were significantly lower at peak exercise in patients with a positive electrocardiographic stress test response than in those with negative response, with maximal acceleration showing the most significance (p less than or equal to 0.001). Coronary angiography was performed in 63 of the 67 patients with positive responses, and patients were separated into 2 groups according to extent of coronary artery disease (CAD): 1- and 2-vessel or 3-vessel CAD. Peak velocity and maximal acceleration were significantly lower in patients with 3-vessel CAD than in those with 1- and 2-vessel CAD (p less than or equal to 0.01 and p less than or equal to 0.01). Discriminant analysis showed maximal acceleration and peak velocity values at peak exercise to be 65% predictive of 3-vessel CAD, onset time to ST-segment depression was 74% predictive and the combination of Doppler and electrocardiographic variables increased 3-vessel CAD predictive value to 80%.(ABSTRACT TRUNCATED AT 250 WORDS)

Utility of the routine electrocardiogram before surgery and on general hospital admission. Critical review and new guidelines.

No consensus has been reached regarding the need for a routine 12-lead electrocardiogram (ECG) preoperatively or on general admission in adult patients. Critical review of relevant studies reveals important weaknesses and gaps in the data needed to formulate definitive recommendations. Available data, however, do not support the necessity for obtaining a baseline or screening ECG in all adult patients before surgery involving general or regional anesthesia or on hospital admission for other indications. To reduce costs related to unnecessary tests and false-positive results, routine use of the ECG is warranted only in selected subsets of hospitalized patients, including those with cardiac signs or symptoms and those at risk for occult heart disease, particularly older patients.

THE CLINICAL VALUE OF VECTORCARDIOGRAPHY IN OLD MYOCARDIAL INFARCTION WITH PARTICULAR EMPHASIS ON ITS USEFULNESS IN CASES WITHOUT SIGNIFICANT Q WAVES

Serial observations on the electrocardiograms in 278 cases of definite acute myocardial infarction revealed the disappearance of diagnostic Q waves in 34 (12.2%) of them during a mean follow-up of 12.1 months. A vectorcardiographic diagnosis of old myocardial infarction was possible in 14 of these 34 cases without Q waves on the basis of abnormal distortion and/or indentation of the QRS loop. The cases with old myocardial infarction were divided into three groups, namely those without abnormal Q waves and without any obvious evidence of myocardial infarction in vectorcardiography (group I), those without abnormal Q waves but with diagnostic vectorcardiographic abnormalities (group II) and those with persistent abnormal Q waves (group III). The severity of coronary atherosclerosis did not differ among the three groups. On the other hand, the involvement of myocardial contraction was the least extensive in group I, more extensive in group II and the most extensive in group III. Thus, vectorcardiography was more sensitive in the diagnosis of old myocardial infarction than routine 12-lead electrocardiogram. The present results also indicate that serial observations on electrocardiograms are of considerable value in myocardial infarction for assessment of the extent of myocardial lesions.

Absence of respiratory sinus arrhythmia: a manifestation of the sick sinus syndrome.

The failure of changes in autonomic drive to affect heart rate is a common finding in patients with the sick sinus syndrome (SSS). The normal respiratory sinus arrhythmia is vagally mediated and should therefore be attenuated in SSS. This hypothesis was tested in a series of 32 symptomatic patients with SSS, mean age 68 years, and an age-matched control group of 75 normal subjects. The degree of sinus arrhythmia present in routine 12-lead electrocardiograms was quantitated as (1) the coefficient of variation (CV) of the R-R interval, and (2) the maximal R-R interval difference (delta R-Rmax). Mean CV was 2.7% in SSS compared to 3.8% in the control group (p less than 0.01). Mean delta R-Rmax was 72 ms in SSS and 140 ms in controls (p less than 0.01). Sixteen of 32 patients (50%) compared to only 4/75 (5%) control subjects had delta R-Rmax of less than 80 ms (p less than 0.01). Thus, SSS is frequently associated with a significant attenuation of sinus arrhythmia and the simple measurement of delta R-Rmax in standard ECG recordings provides useful diagnostic information.

Flutter and fibrillation-like phenomenon of his bundle observed in a patient with persistent atrial standstill

A diagnosis of persistent atrial standstill was made in a patient with syncopal attacks, based on: (1) the lack of P waves both in the routine 12-lead electrocardiogram (ECG) and in the right atrial cavity lead; (2) the absence of "a waves in the right atrial pressure curve; and (3) the failure of the atria to respond to electrical stimulation. Compared with previously reported cases of persistent atrial standstill with a slow, regular escape rhythm of supraventricular origin, the present case was characterized by alternate periods of bradycardia and tachycardia, the latter being suggested as AV junctional tachycardia with exit block. Furthermore, the His bundle electrogram (HBE) showed either regular, high frequency deflictions or irregular, deformed potentials, suggesting flutter and fibrillation-like phenomena in the His bundle.