QRS Amplitude Research Articles

Triple-site pacing in patients with biventricular device-incidence of the phenomenon and cardiac resynchronization benefit.

In patients with biventricular pacing (BIV), triple-site pacing (TSP), i.e. standard biventricular cathodal pacing of the right and the left ventricle plus additional anodal capture of the right ventricle, is sometimes present. To evaluate the incidence of TSP phenomenon, to examine TSP-related QRS changes, and to assess the effect of TSP on intraventricular resynchronization by means of tissue Doppler imaging (TDI). 23 patients with a first generation biventricular device (Medtronic 8040) and 16 patients with a new generation device (Medtronic 8042) were evaluated to look for the presence of TSP. TSP was found in 6 patients (26%) with the Medtronic 8040 (group I) and in 13 patients (81%) with the Medtronic 8042 device (group II). QRS duration decreased by 10 to 20 ms and QRS amplitude of leads I and aVL increased in almost all patients in group I during TSP modality. In group II, QRS morphology, duration and amplitude did not change as obviously. TDI analysis of the left ventricular (LV) basal segments showed significant shortening of the systole, together with a corresponding prolongation of the diastole, at the inferior wall of the LV, during TSP compared to standard BIV in all patients ( p < 0.01). Other LV segments did not show any change. Qualitative TDI electro-mechanical activation pattern of all LV segments improved in 22%, while it remained unchanged in 72%. TSP phenomenon can be identified in approximately a quarter of patients with the first-generation biventricular devices on the basis of the QRS morphology changes. In the second-generation biventricular pacemakers it can be demonstrated in the vast majority of patients. TSP may increase the effectiveness of cardiac resynchronization therapy by counteracting the regional activation delay located at the inferior wall of the LV.

The Initial Stage of Left Ventricular Hypertrophy in Spontaneously Hypertensive Rats is Manifested by a Decrease in the QRS Amplitude/Left Ventricular Mass Ratio

In this study we tested the hypothesis of the relative voltage deficit, i.e. the discrepancy between increased left ventricular mass (LVM) and QRS amplitudes, in an experimental model of spontaneously hypertensive rats (SHR) during the period of a moderate increase in blood pressure. To address this issue we recorded orthogonal electrocardiograms of male SHR at the age of 12 and 20 weeks. During this period the systolic blood pressure (sBP) increased from 165 ± 3 mmHg to 195 ± 1 mmHg (p < 0.001). Age and sex matched WKY rats were used as control groups. The sBP values in WKY normotensive control groups were within normal limits (122 ± 8 mmHg and 130 ± 4mmHg, respectively). The maximum QRS spatial vector magnitude (QRSmax) was calculated from X, Y, Z amplitudes of the orthogonal electrocardiograms. The animals were sacrificed and the left ventricular mass was weight. The specific potential of myocardium (SP) was calculated as a ratio of QRSmax to LVM. The LVM in SHR (0.86 ± 0.05 g and 1.05 ± 0.07 g, respectively) was significantly higher as compared to WKY (0.65 ± 0.07 g and 0.70 ± 0.02 g), and the increase of LVM closely correlated with the sBP increase. On the other hand, QRSmax in SHR did not follow either the increase of sBP, or LVM. The QRSmax values in SHR did not differ from those of WKY at the age of 12 weeks (0.59 ± 0.14 mV compared to 0.46 ± 0.05 mV), and they were even lower in SHR at the age of 20 weeks (0.74 ± 0.08 mV compared to 0.44 ± 0.05 mV, p < 0.001). The values of SP, quantifying the relative voltage deficit, were significantly lower in SHR as compared to the WKY control. The values decreased significantly in SHR with increasing age, sBP and LVM, i.e., with the progression of hypertrophic remodeling of the left ventricle. The results of this study support the hypothesis of the relative voltage deficit in LVH. These results are consistent with the finding of a high number of false negative ECG results in clinical ECG diagnostics of LVH, and could contribute to an understanding of the diagnostic importance of the false negative ECG results, their re‐evaluation and utilization for clinical diagnosis and prognosis.

Comparative dipolar electrocardiotopographic study of ventricular activation in Macaca mulatta monkeys and man.

Electrocardiographic correlates of ventricular activation sequence were studied in 22 Macaca mulatta monkeys, aged 1-18 years, and 145 human subjects, aged 11-72 years, using the corrected orthogonal lead system of McFee-Parungao and the dipolar electrocardiotopographic (DECARTO) data presentation, where the time series of instantaneous spatial vectors are converted into time series of areas of activation on a spherical image surface enveloping the heart. Macaques had shorter ventricular activation time (61+/-11 vs. 97+/-11 ms) that could not be explained exclusively by their higher heart rate. Their DECARTO image of the resultant activation front occurred 10 ms after QRS onset (septal activation) identically with humans, but it attained a more anteriorly oriented maximum earlier than in humans (20 vs. 40 ms). The time course of the extent of the resultant activation front in old macaques (15-18 years) resembled to that observed in humans. On the average, female macaques had smaller DECARTO images of activation fronts throughout the QRS complex than males. This finding is in agreement with the known smaller QRS amplitudes in women than in men.

Assessment of ventricular repolarization alterations in subjects with early repolarization

Background: Although the electrocardiographic (ECG) features of early repolarization (ER) have been studied extensively, no systematic quantification of ventricular repolarization in subjects with ER has been conducted so far. Methods: The objective of the present study was to evaluate ECG and spatial vectorcardiographic (VCG) descriptors of ventricular repolarization in ER subjects and to associate them with the respective indices of ventricular depolarization. A digital 12-lead surface ECG was obtained from 108 young, healthy men with ER and 108 age-matched healthy controls. The maximum Q-onset–T-end interval (QT maximum), the maximum Q-onset–T-peak interval (QTp maximum), the respective QT dispersion values (QT maximum–QT minimum), the rate-corrected QTC maximum and QTpC maximum, the QRS duration, and the VCG markers spatial T amplitude, spatial QRS amplitude and spatial QRS– T angle, were evaluated in ER subjects and controls. Results: QT maximum ( P=0.05) and QTp maximum ( P=0.003) were higher in ER subjects than in controls, while QTC maximum ( P<0.0001) and QTpC maximum ( P=0.002) were lower in ER subjects than in controls. The QRS duration ( P=0.013), as well as the spatial T amplitude, the spatial QRS amplitude, and the spatial QRS– T angle were higher in ER subjects than in controls ( P<0.0001). The spatial T amplitude was not associated with the indices of ventricular depolarization neither in ER subjects, nor in controls. Conclusions: Ventricular repolarization, as well as depolarization, is altered in young, healthy males with ER compared to age-matched healthy controls. Ventricular depolarization and repolarization indices in ER subjects are not associated to each other.

A33-6 Which lead polarity provides optimal paced and sensed QRS amplitudes in dual chamber stored electrograms?

A33-6 Which lead polarity provides optimal paced and sensed QRS amplitudes in dual chamber stored electrograms?

A33-6 Which lead polarity provides optimal paced and sensed QRS amplitudes in dual chamber stored electrograms?

A33-6 Which lead polarity provides optimal paced and sensed QRS amplitudes in dual chamber stored electrograms?

Analysis of electrocardiograms for subcutaneous monitors

We are developing a subcutaneous cardiac arrest monitor and alarm with electrodes that have spacing of a few centimeters. We hypothesize that closely spaced bipolar electrodes that provide QRS amplitudes of a millivolt or more in sinus rhythm (SR) will not provide similar amplitudes during ventricular tachyarrhythmia (VT/VF), and that an orthogonal set of electrode pairs in diagonal is necessary to produce signals of sufficient amplitude in order to distinguish these rhythms. Methods: Forty patients were studied during ICD implantation in the clinical electrophysiology laboratory. A square array of 9 electrodes with 4- to 10-cm spacing between adjacent electrodes was placed on the patient’s anterior chest over the left heart. The center electrode in the left most column is located in the 5th intercostal space at the left sternal border. Eight-channel recordings were made in SR and during induced VT/VF from the 8 peripheral electrodes referenced to the central member of the array. From these recordings all 20 bipolar ECGs of adjacent (including diagonally adjacent) electrodes were constructed algebraically. QRS peak-peak amplitudes in SR and VT/VF were measured in each bipolar lead and in the spatial vector formed by summing the squares of each adjacent and orthogonal pair of these leads. Results: Electrode pairs that yielded optimal ECG amplitudes in SR were not always the pairs that yielded optimal amplitudes in VT/VF. But in every patient two orthogonal pairs could be found whose QRS vector amplitude is sufficient in both SR and VT/VF to separate the rhythms. Conclusions: A patient-defined set of bipolar electrode pairs is suitable for automatic separation of SR and VT/VF by rate in subcutaneous ambulatory monitoring.

Pneumothorax during laparoscopy.

Pneumothorax is a known complication of laparoscopy, with most pneumothoraces diagnosed postoperatively with conventional chest x-ray. Electrocardiogram (ECG) conduction changes are associated with pneumothorax. In a sheep model, ECG changes were evaluated as a potential indicator of intraoperative pneumothorax. Additionally, resolution rates of helium (He) and carbon dioxide (CO2) pneumothorax were also evaluated in this model. Under general anesthesia, 10 sheep had known volumes (20-100 cc) of either He or CO2 introduced into the left hemithorax. A 12-lead ECG recorded changes associated with the induced pneumothorax. After changes in the ECG plateaued, the gas volume in the hemithorax was increased to 2 L and the resultant pneumothorax was followed for a 2-h period using fluoroscopy to determine resolution rates for the different gas pneumothoraces. Gas volumes were aspirated after 2 h and ECGs were again recorded. Pneumothorax volumes as low as 20 cc produced consistent ECG changes. The amplitude of the precordial QRS complex was seen to diminish, and this lowering of the QRS amplitude continued as pneumothorax volume increased up to 100 cc. The ECG returned to prepneumothorax patterns with aspiration of the left chest. For different gas pneumothoraces, CO(2) pneumothorax showed almost complete resolution in the 2-h period, whereas He pneumothorax was unchanged. Precordial ECG changes appear to be a very sensitive indicator of pneumothorax, with very small pneumothorax (<100 cc) consistently being detected by reduction of the QRS complex amplitude. Intraoperative use of precordial ECG leads could result in rapid identification of pneumothorax during laparoscopic surgery. Carbon dioxide pneumothorax shows near 100% resolution in a 2-h period. This supports recommendations of expectant management in asymptomatic patients with CO(2) pneumothorax. However, He pneumothorax does not resolve spontaneously quickly and may require aspiration even in asymptomatic patients.

Telemetrically monitored arrhythmogenic effects of doxorubicin in a dog model of heart failure

A model of chronic heart failure has been induced in dogs by repeated intracoronary infusion of doxorubicin, which is an antineoplastic medication that has dose-limiting cardiotoxic side effects. Although many of the dogs receiving doxorubicin develop typical signs of dilated cardiomypathy over 4–6 weeks, some of them suddenly die before completing the four weekly infusions of the drug. The present study was undertaken to determine whether such sudden death may be caused by the development of fatal arrhythmias during doxorubicin treatment. This was assessed by telemetrically monitoring the EKG of seven dogs, which received intracoronary infusion of 1 mg/kg doxorubicin given in four divided weekly doses. The recordings were obtained for 8–10 h on alternate days up to 4 weeks. Echo-cardiographic recordings were obtained once a week. The acute effects with each infusion of doxorubicin included a significant increase in heart rate, and no significant change in QRS complex. The cumulative prolonged effects of doxorubicin included slight reduction in QRS amplitude and duration, and marked arrhythmic changes. Four out of seven dogs showed a spectrum of arrhythmic events such as single or groups of premature ventricular complexes (PVCs), bigeminy, ventricular tachycardia (VTAC), ventricular fibrillations (VFIB), and asystole. All dogs did not show each of the events listed above and the same dog did not show all the events all the time. One of these four dogs developed VFIB for 25 min and then asystole leading to sudden death. These studies conclusively showed that fatal arrhythmias develop in some of the dogs receiving doxorubicin treatment accounting for the sporadic incidence of sudden death. Prophylactic treatment with antiarrhythmic agents may prevent such adverse events.

Electrocardiographic Changes during Hemodiafiltration with Different Potassium Removal Rates

Background/Aims: Sudden K removal is thought to be implicated in ECG alterations observed during hemodialysis (HD). The effects of the K removal rate on ECG-derived parameters have been investigated. Methods: Two different hemodiafiltration (HDF) schedules were used for 10 HD patients: the dialysate K concentration was kept constant in HDF_st, while in HDF_K it was decreased during the session in order to maintain a uniform plasma-dialysate K gradient. A 12-lead Holter monitor was used to acquire the ECG in the course of the treatments. Classical ECG parameters and overall indices for quantifying ventricular repolarization abnormalities were evaluated. Results: Several ECG parameters were affected by both HD therapies (ST depression, QRS amplitude and QT dispersion), but only indices of the homogeneity of repolarization (PCA-T, E1-T) were significantly affected by the K removal rate. Conclusion: The present study confirms the large impact of HD therapy on ECG. The analysis of the spatial T wave complexity points out the intrinsic arrhythmogenic implications of the K removal rate.

Normal limits of the electrocardiogram in Chinese subjects

Background: Accurate normal limits of the electrocardiogram (ECG) are the basis on which diagnostic criteria are developed. The ECG, however, is subject to age- and sex-variations and may also be racially determined. Studies into normal ECG limits for the Chinese, comprising one fifth of the world population, are few and have their limitations. We have undertaken to establish normal limits of the ECG from a large sample of healthy Chinese subjects. Methods: Standard simultaneous 12-lead ECGs from 5360 apparently healthy Chinese subjects (3614 men and 1746 women, ages ranging from 18 to 84 years) were collected with a modern digital recorder and processed with a well-validated ECG computer program. The medians, lower limits (2nd percentile) and upper limits (98th percentile) of various ECG measurements were calculated and age and sex differences examined. Results: Significant age trends were present in, for example, P-wave duration, QTc interval, and frontal QRS axis, with concomitant changes of R amplitudes in the extremity leads. Sex differences existed for heart rate, interval durations, the Sokolow and Cornell indices, and QRS and ST-T amplitudes in different leads. Notably, left-precordial R-wave amplitudes in women increased with age; the Sokolow index showed a clearer age trend for men than for women, the reverse being true for the Cornell index. Some of these findings are at odds with established diagnostic ECG criteria. Conclusions: Normal ECG limits of Chinese subjects show marked age and sex differences. This merits the definition and use of age- and sex-specific ECG criteria for a Chinese population.

Late potential analysis: is a mathematically-derived X,Y,Z lead system comparable to a true orthogonal X,Y,Z lead system?

Analysis of ventricular late potentials (LP) with signal-averaged ECG (SAECG) using three bipolar, orthogonal X,Y, Z leads is a validated method of risk-stratification in patients prone to ventricular tachycardia. The aim of this study was to validate a ECG system, which allows LP analysis using X,Y, Z leads mathematically derived from the standard 12-lead ECG. In 36 patients (age 56 +/- 12 years, coronary artery disease 71%, LVEF 46 +/- 14%) with known or suspected ventricular tachyarrhythmia, two consecutive SAECGs were recorded, one with mathematically derived and another one with true X,Y, Z leads. Time domain measurements with these different lead systems were compared using linear regression analysis and "Bland-Altman" plots. Correlation was good (r = 0.92) for the filtered QRS complex duration, but poor for the terminal QRS amplitude (RMS) and duration (LAS) criteria (r = 0.66 and 0.61, respectively; P < 0.0001). Defining LPS as present if at least two of the three time domain criteria were abnormal, the result matched in 28 (78%), but differed in 8 (22%) patients. SAECG using X,Y, Z leads mathematically derived from the standard 12-lead ECG compared to true bipolar X,Y, Z leads show a close correlation in filtered QRS duration, but can differ considerably in the other time domain measurements, resulting in different interpretation of LP analysis in 22%. Therefore, SAECG registration should currently be performed with true X,Y, Z leads, until the accuracy of other approaches is validated.

Effects of season and temperature acclimation on electrocardiogram and heart rate of toads

Electrocardiogram (ECG) was recorded from unrestrained toads of two species, one resistant ( Bufo viridis) and the other sensitive ( B. regularis) to low temperatures. Although the temperature-sensitive species could not survive at temperatures below 7–8 °C, heart rate is linearly and similarly related to ambient temperature in the two species. In B. viridis, the cold resistant species, heart rate in winter was 25% lower than in summer, and the dependency of heart rate on temperature was reduced by 50% in toads acclimated to 10 °C in winter. It was not possible to disclose any effect of acclimation on heart rate in summer, due to the large variation in the recorded values. The QRS amplitude in the ECG was considerably reduced at low temperature only in B. viridis. It is concluded that differences in cardiac activity cannot account for the distinct difference in thermal relations of the two species, and that it should reside at other regulatory levels.

Significance of shortening of the mean QRS duration of the standard electrocardiogram in patients developing peripheral edema

An electrocardiographic syndrome was reported recently linking a gradual decrease in the QRS potentials of the standard electrocardiogram (ECG) with a parallel development of peripheral edema in patients with a critical illness of varying etiology. 1 In that study, a decrease in the sums of QRS amplitude of 12-lead ECGs (QRS) correlated well with weight gain (r 0.61, p 0.0005). Perusal of the daily ECGs from that study revealed gradual shortening of the mean QRS duration. To investigate this matter further, a documentation of the decrease in the mean QRS duration and an analysis of its relation with weight and QRS was carried out. The objectives of this study were: (1) to define whether mean QRS duration correlates with weight gain; (2) to determine whether it has any advantages when compared with QRS in predicting weight gain; and (3) to determine whether it provides a better indicator of weight gain when combined with QRS in a form of a product. Speculation as to the mechanism of decrease in the mean QRS duration consequent to weight gain is also included in this study. ••• The study population and the methods employed have been previously described. 1 For the purposes of this study, data from the consecutive series of 28 patients with peripheral edema admitted to our Coronary Care Unit in 1999 with a critical illness were reevaluated. The patients had daily weights and electrocardiographic tracings recorded. Information on percent change of weight from admission to the point of peak weight value, and half-weight gain were used as study parameters. The QRS and mean QRS duration and the percent change of QRS and mean QRS duration from admission to the peak weight and half-weight points were also considered. In addition, a composite variable consisting of the product of QRS and mean QRS duration of the corresponding ECG was included. QRS was calculated as the sum of the QRS complex amplitudes (highest positive lowest negative deflection) of all electrocardiographic leads, measured to the nearest 0.5 mm, using a magnifying glass and calipers (Figure 1). The average of measurements of 3 consecutive beats was used for ECGs of patients with atrial fibrillation. The Hewlett-Packard (now acquired by Royal

Effect of changes in body weight and serum albumin levels on electrocardiographic QRS amplitudes

An association of gradual weight gain in patients with generalized extensive edema (anasarca) and parallel amplitude attenuation of surface electrocardiographic (ECG) potentials was recently reported. 1 Madias J.E. Bazaz R. Agarwal H. Win M. Medepalli L. Anasarca-mediated attenuation of the amplitude of ECG complexes a description of a heretofore unrecognized phenomenon. J Am Coll Cardiol. 2001; 38: 756-764 Abstract Full Text Full Text PDF PubMed Scopus (116) Google Scholar Heaf 2 Heaf J.G. Albumin-induced changes in the electrocardiographic QRS complex. Am J Cardiol. 1985; 55: 1530-1533 Abstract Full Text PDF PubMed Scopus (10) Google Scholar had reported an effect of serum albumin levels on QRS amplitudes. To explore the issue of albumin levels as a confounding factor in the interaction of weight and amplitude of electrocardiographic complexes, an investigation was performed using the data basis of our previous study. 1 Madias J.E. Bazaz R. Agarwal H. Win M. Medepalli L. Anasarca-mediated attenuation of the amplitude of ECG complexes a description of a heretofore unrecognized phenomenon. J Am Coll Cardiol. 2001; 38: 756-764 Abstract Full Text Full Text PDF PubMed Scopus (116) Google Scholar

Alternans in QRS amplitude during ventricular tachycardia.

Although the value of T wave alternans as an index of electrical instability has been extensively investigated, little is known about QRS alternans during VT. Intracardiac electrograms of 111 episodes of spontaneous monomorphic regular VT retrieved from implantable defibrillators in 25 patients were retrospectively selected. Three beat series, representing the total amplitudes and amplitudes from baseline to summit and from baseline to lower point of 16 or 32 successive QRS complexes before deliverance of electrical therapy were generated for each episode. Spectral analysis was then performed using the fast Fourier transform. VT was considered as alternans if the magnitude of the spectral power at the 0.5-cycle/beat frequency was greater than the mean +/- 3 SD of the noise in at least one of the three spectral curves. QRS alternans was present in 23 (20%) of 111 episodes and in 9 (36%) of 25 patients. Alternans was not related to the VT cycle length, QRS duration, QRS amplitude, signal amplification, nor to clinical variables. Alternans was more frequently detected in unipolar configuration and when a higher number of complexes was included in analysis. Failure of antitachycardia pacing was more frequent in case of alternans VT (50% vs 75% success in nonalternans VT, P = 0.05). Spontaneous termination before deliverance of therapy occurred in 16 non-alternans VT but never in alternans episodes (P = 0.02). Alternans in QRS amplitude is a relatively common finding during VT and could be associated with failure of antitachycardia pacing and lack of spontaneous termination. Lower efficacy of electrical therapies in case of QRS alternans must be confirmed in a way to improve the effectiveness of antitachycardia pacing.

Effect of weight loss in congestive heart failure from idiopathic dilated cardiomyopathy on electrocardiographic QRS voltage

It was appreciated in the 1950s and 1960s that patients with congestive heart failure (CHF) had lower QRS voltages on their electrocardiograms than they had when compensated.1–4 Also, 30 years ago Ishikawa et al5 documented an increase in ECG voltages in 12 patients after treatment of CHF, whereas a decrease in the QRS amplitudes occurred in 3 patients with poor response to therapy.5 Recently, a phenomenon consisting of a reduction in ECG amplitude commensurate with weight gain in patients with anasarca was reported6; the involved patients had a variety of critical illnesses, mainly sepsis, and required administration of large volumes of intravenous fluids. During the last month of implementation of this study,6 we encountered in the coronary care unit 3 patients with CHF who had the reverse phenomenon, i.e., an increase in the amplitude of electrocardiograms in response to treatment of CHF, and a resultant loss of weight. These were the only patients admitted in the course of 1 month, with CHF and visible “pitting” peripheral edema in the pretibial aspect of their legs and the dorsum of their feet. Daily weights and standard electrocardiograms were obtained. Measurements to the nearest 0.5 mm of the amplitude (highest positive + lowest negative deflections) of the QRS complex of all 12 leads were obtained by 1 of the investigators (JEM) using a magnifying glass and calipers. Calibration was 1 mV = 10 mm. Sums of the QRS amplitudes of all leads (ΣQRS) were calculated for electrocardiograms of each patient from the days corresponding to the initial (peak) and the lowest weights attained in response to therapy for CHF. Both the change in weights and ΣQRS, and the adjusted values to the commencement of therapy as a percent change were used as variables. The intraobserver variability of ΣQRS in 10 random electrocardiograms from a previous study was found to be 0.41 ± 3.34% (mean ± SD).6 Because hematocrit change may affect blood conductivity,7,8 and thus the amplitude of ECG potentials, this parameter was followed closely. Electrolytes were monitored, and supplemental potassium was administered. Frequent portable chest radiographs were obtained in the study patients to evaluate heart size and status of pulmonary congestion, and its change. Echocardiograms were obtained to assess cardiac structure and function. Management of CHF was done routinely.

A critique of the new ST-segment criteria for the diagnosis of acute myocardial infarction in patients with left bundle-branch block.

Recently, electrocardiogram (ECG) criteria have been proposed for the diagnosis of acute myocardial infarction (AMI) in the presence of left bundle-branch block (LBBB). However, clinical experience indicates that such ECG changes indicative of AMI are occasionally noted in clinically stable patients with LBBB, raising concerns about the specificity of the proposed criteria. The aim of this study was to evaluate the frequency of ST-segment abnormalities suggestive of AMI in ambulatory patients with cardiovascular disease and chronic LBBB, who did not have an AMI. In addition, the ECG determinants of such ST-segment abnormalities were sought. The files of all (4,193) patients followed in the outpatient cardiology clinic were reviewed to identify patients with LBBB. Electrocardiograms of these patients were evaluated as to the duration of the QRS complex, frontal QRS axis, amplitude of QRS in leads V1-V3, and the presence and magnitude of ST-segment depression (-ST) in leads V1-V3, and ST-segment elevation (+ST) in leads with predominantly positive or negative QRS complexes. Correlations of these ECG variables were carried out. In 124 patients with LBBB only 1 patient with -ST of 1 mm in leads V1-V3, and 1 patient with +ST of 1 mm in a predominantly positive ECG lead were found; the latter patient also had +ST of 6 mm in V3. Nine patients were detected with > or = 5 mm +ST in at least one ECG lead with predominantly negative QRS complex. Regression analysis of amplitude of +STs on corresponding QRS amplitudes in leads V1-V3 yielded Rs of 0.69, 0.68, and 0.69, all with a p value of 0.00005. A similar analysis of the amplitudes of +STs > or = 5 mm with the corresponding QRSs yielded an R = 0.76 and a p value of 0.0018. Thus, recently proposed ST-segment criteria for the diagnosis of AMI in patients with LBBB are appropriate. However, stable > or = 5 mm +STs are occasionally found in leads with predominantly negative QRS complexes, particularly of large amplitude (mean value 46.0, range [28.0-71.0] mm) in the absence of AMI. In such patients presenting with symptoms suggestive of AMI, further non-ECG confirmation of probable underlying AMI should be sought.

Anasarca-mediated attenuation of the amplitude of electrocardiogram complexes: a description of a heretofore unrecognized phenomenon

OBJECTIVESThe relationship between the changes of weight (WT) and electrocardiogram (ECG) QRS amplitude in patients with anasarca (AN) was evaluated.BACKGROUNDAttenuation of the ECG voltage occurs as the electrical current spreads from the epicardium to the body surface. The voltage registered is a function of the cardiac potentials, the electrical resistivities of the intervening tissues and the orientation of the ECG leads with respect to the direction of propagation of excitation. Lung congestion and pericardial and pleural effusions can cause attenuation in the ECG potentials; additionally, a similar change was recently observed in patients with AN.METHODSA prospective study of this phenomenon in 28 patients with a critical illness was carried out. Electrocardiograms and patients’ WTs were recorded daily. Pericardial effusions were excluded by serial echocardiograms. The sums of the amplitude of QRS complexes from the 12 ECG leads (ΣQRS) were correlated with the corresponding WTs. Intracardiac ECGs, done in three patients, were correlated with surface ECGs.RESULTSAdmission WT was 148.9 ± 37.8 lbs, and it peaked to 197.8 ± 52.3 lbs (p = 0.0005). Admission ΣQRS was 120.2 ± 41.6 mm and dropped to 54.8 ± 26.9 mm at time of peak WT (p = 0.0005). Regression of ΣQRS on WT revealed an r = 0.61 and a p = 0.0005. Subsequent WT loss in 13 patients (from 219.0 ± 40.7 lbs to 179.5 ± 41.7 lbs, p = 0.001) led to an increase of ΣQRS from 53.5 ± 24.5 mm to 86.8 ± 38.2 mm (p = 0.001). Intracardiac ECGs remained stable, while surface ECGs changed with perturbations of WT.CONCLUSIONSAttenuation of ECG voltage in patients with AN correlates with WT gain, and it can be attributed to a shunting of the cardiac potentials due to the low resistance of the AN fluid.

Changes in QRS voltage in cardiac tamponade and pericardial effusion: reversibility after pericardiocentesis and after anti-inflammatory drug treatment

OBJECTIVESThe goal of this study was to define the association between low QRS voltage and cardiac tamponade or pericardial effusion and to assess the reversibility of low QRS voltage after therapeutic procedures.BACKGROUNDIt is unclear whether low QRS voltage is a sign of cardiac tamponade or whether it is a sign of pericardial effusion per se.METHODSIn a prospective study design, we recorded consecutive 12-lead electrocardiograms and echocardiograms in 43 patients who were referred to our institution for evaluation and therapy of a significant pericardial effusion. Cardiac tamponade was present in 23 patients (53%). Low QRS voltage (defined as maximum QRS amplitude <0.5 mV in the limb leads) was found in 14 of these 23 subjects (61%). Nine of these 14 patients were treated by pericardiocentesis (group A). Five patients received anti-inflammatory medication (group B). Group C consisted of nine patients with pericarditis and significant pericardial effusion who had no clinical evidence of tamponade.RESULTSIn group A, low QRS voltage remained largely unchanged immediately after successful pericardiocentesis (0.36 ± 0.17 mV before vs. 0.42 ± 0.21 mV after, p = NS), but QRS amplitude recovered within a week (0.78 ± 0.33 mV, p < 0.001). In group B, the maximum QRS amplitude increased from 0.40 ± 0.20 mV to 0.80 ± 0.36 mV (p < 0.001) within six days. In group C, all patients had a normal QRS amplitude initially (1.09 ± 0.55 mV) and during a seven-day follow-up (1.10 ± 0.56 mV, p = NS).CONCLUSIONSLow QRS voltage is a feature of cardiac tamponade but not of pericardial effusion per se. Our findings indicate that the presence and severity of cardiac tamponade, in addition to inflammatory mechanisms, may contribute to the development of low QRS voltage in patients with large pericardial effusions.