Features of an exceptionally narrow QRS data set

Background

Little attention has been directed to the characteristics of electrocardiograms (ECGs) with brief QRS durations (BD).

Methods

From a database of 859?977 computer-analyzed (Marquette 12SL, GE Healthcare, Milwaukee, WI, USA) ECGs of 216?148 patients, 1805 patients (data set of BD: 19?718 ECGs; age, >18 years, unpaced), had, in at least one ECG, a QRS duration of less than 62 milliseconds, a prevalence of 0.8%.

Results

The QRS duration ranged from 46 to 188 milliseconds; values fluctuated between excessive brevity and the traditionally normal (80-95 milliseconds), with many values in the 60's. The average age at first acquisition was 56 years (range, 18-96 years); 1371 were female (76%) and 433 were males (24%); and 416 were white (23%), 1243 African American (69%), 109 other (6%). The summed 12-lead QRS amplitude (ΣQRS) ranged from 2800 to 32?929 μV (mean ± SD, 11?154 ± 4101), and heart rate ranged from 40 to 269 (98 ± 26). There was a statistically positive relationship between QRS duration (in the range 52-105 milliseconds) and ΣQRS (P < 0001): for each 1000 μV increment, duration increased by 0.7 milliseconds (95% confidence interval [CI], 0.66-0.73 milliseconds). Conversely, for each 5-millisecond increment in duration, ΣQRS increased by 475 μV (95% CI, 450-498 μV). There was an inverse relationship between QRS duration and heart rate (P < .0001): for every 10 beat rate increase, the duration dropped by 1.14 milliseconds (95% CI, 1.09-1.19 milliseconds). An additional data set of normal QRS durations ND consisted of 2902 subjects, none of whose 40?327 ECGs showed a QRS duration less than 62 milliseconds; 2.8% of ND ECGs had durations in the 62-69 millisecond range, 26% in BD. Sinus tachycardia was 43% in BD and 24% in ND. The average age of ND was 58 years (range, 18-100 years); 44% were male and 56% female; and 39% were white and 57% were African American. A positive relationship between duration and amplitude was found among ND subjects as well: for each 1000 point increase in ΣQRS, duration increased by 0.45 milliseconds (P < .0001; 95% CI, 0.42-0.47 milliseconds). The duration amplitude relationship did not hold for durations greater than 105 milliseconds in either data set.

Conclusion

Over the full extended span of QRS durations (46-106 milliseconds), the value of the latter is directly related to the total summed amplitude of the 12-lead QRS. An inverse relationship is demonstrable with heart rate.     

Diagnostic accuracy of a new detection algorithm for atrial fibrillation in cardiac telemonitoring with portable electrocardiogram devices

Background

Telemedical approaches targeting cardiac outpatients try to include electrocardiogram (ECG) analysis. Increasing numbers of monitored patients require automated preanalysis of the ECG to prioritize the evaluation for the clinical professional to enable an efficient intervention.

Methods

ECGs were recorded from 60 patients, both with a standard 12-lead ECG and with a new handheld ECG device having dry electrodes for direct skin contact. Recordings of the handheld device were automatically analyzed by a new algorithm. The 12-lead recordings were evaluated by a blinded cardiologist and then compared to the automated analysis of the handheld ECG. Sensitivity and specificity of the algorithm for the detection of atrial fibrillation (AF) were calculated.

Results

A total of 60 ECG strips having 122 ± 36 beats were registered. One hundred percent of the ECG strips were sufficient for automated heart rate count; 96.6%, for automated AF analysis; and 80%, for PQ, QRS, and QTc time measurements. AF detection had a sensitivity of 92.9% and a specificity of 90.9%. There was no difference in heart rate count between automated and manual analysis (median, 71 vs 70 beats per minute; P = .51). Automated measurements of a summary complex showed no difference for PQ time (165 vs 161 milliseconds, P = .50) but overestimated QRS (119 vs 90 milliseconds, P = .001) and QTc (489 vs 417 milliseconds, P < .001) times as compared to the 12-lead recordings analyzed manually.

Conclusion

The new algorithm is suitable for automated preanalysis of the ECG data with regard to AF. It could be used for rapid selection of ECGs with relevant rhythm abnormalities from a large pool. Electrocardiographic data remain to be evaluated by health care professionals for exact diagnosis.     

An early phase of slow myocardial activation may be necessary in order to benefit from cardiac resynchronization therapy

Background

Not all patients with a QRS duration longer than 140 milliseconds respond to cardiac resynchronization therapy (CRT). The same QRS duration may correspond to different spatiotemporal patterns of myocardial activation that influence response to CRT.

Methods

Electrocardiographic ima'ging based on 80 chest wall electrodes was used to construct the spatiotemporal myocardial activation map in 46 consecutive patients before CRT. The cumulative percentage of myocardium activated was plotted against time expressed in terms of quintiles of the overall QRS duration. Changes in the left ventricular ejection fraction and end-diastolic diameter, maximum oxygen consumption per minute, brain natriuretic peptide level, and 6-minute walk distance after 6 months of CRT were compared across different patterns with 1-way analysis of variance.

Results

Data from 34 patients were available for analysis. Four spatiotemporal patterns of myocardial activation could be identified: triphasic (fast-slow-fast) (13), uniform (8), fast-slow (7), and slow-fast (6). The overall QRS duration was similar in the 4 groups (166 ± 19 vs 138 ± 21 vs 157 ± 26 vs 152 ± 37 milliseconds, P = not significant [NS]). The ejection fraction showed a trend of greater increases for the triphasic (6.5% ± 7.0%) and slow-fast (15.5% ± 6.4%) patterns than for the uniform (4.0% ± 13.3%) and fast-slow (8.0% ± 6.1%) patterns (P = NS). The end-diastolic diameter showed a trend of greater decreases for the triphasic (−3.7% ± 5.3%) and slow-fast (−7.0% ± 6.7%) patterns than for the uniform (0.8% ± 6.7%) and fast-slow (0.0% ± 4.6%) patterns (P = NS). The maximum oxygen consumption per minute showed a trend of greater increases for the triphasic (1.2 ± 4.2 mL/kg/min) and slow-fast (4.1 ± 2.7 mL/kg/min) patterns than for the uniform (0.1 ± 4.1 mL/kg/min) and fast-slow (1.0 ± 2.1 mL/kg/min) patterns (P = NS). The brain natriuretic peptide level decreased significantly more for the triphasic (−450 ± 1269) and slow-fast (−3121 ± 1512) patterns than for the uniform (762 ± 1036) and fast-slow (718 ± 2530) patterns (P = .0003). The 6-minute walk distance increased significantly more for the triphasic (29 ± 89) and slow-fast (40 ± 23) patterns than for the uniform (6 ± 87) and fast-slow (37 ± 45) patterns (P = .0003).

Conclusions

Different spatiotemporal patterns of myocardial activation exist among patients with broad QRS complex and may affect response to CRT. An early phase of slow myocardial activation (the triphasic fast-slow-fast and the slow-fast patterns) may be necessary for a patient to benefit from CRT.     

Discrepancy between increased left ventricular mass and "normal" QRS voltage is associated with decreased connexin 43 expression in early stage of left ventricular hypertrophy in spontaneously hypertensive rats

Background and Purpose

On the basis of our previous results of animal and human studies, we assume that the discrepancies between increased left ventricular mass (LVM) and electrocardiographic (ECG) findings not exceeding the upper normal limits in left ventricular hypertrophy (LVH) are conditioned by the electrical remodeling of hypertrophied myocardium. We assumed that these discrepancies observed in the early stage of LVH in spontaneously hypertensive rats (SHR) are associated with a decreased expression of connexin 43.

Methods

Standard 12-lead ECG was recorded in 20-week-old male SHR and age-matched and sex-matched normotensive Wistar rats (Institute of Experimental Pharmacology SAV, Dobra Voda, Slovakia). The approximated maximum QRS spatial vector magnitude (QRSmax) was calculated from leads V₂, aVF, and V₅. Left ventricular mass was weighed, and the specific potential (SP) of myocardium was calculated as the QRSmax-to-LVM ratio. Left ventricular protein levels of connexin 43 were analyzed with sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting.

Results

The LVM values were significantly higher in SHR than in normotensive controls (0.96 ± 0.03 g and 0.680 ± 0.07 g, respectively; P < .001). The QRSmax values in SHR did not follow the increase either in systolic blood pressure or in LVM. The SP values in SHR were significantly lower than those in control rats (0.92 ± 0.11 mV/g and 1.358 ± 0.06 mV/g, respectively; P < .01). A 37% decrease in connexin 43 level was observed in SHR.

Conclusions

The QRS voltage did not follow the increase in the LVM in 20-week-old SHR, and the values of connexin 43 were lower in SHR than in normotensive controls. We believe that the discrepant findings between ECG voltage and LVM can be caused by the electrical remodeling in the early stages of LVH.     

The prognostic value of the Tpeak-Tend interval in patients undergoing primary percutaneous coronary intervention for ST-segment elevation myocardial infarction

Introduction

The Tpeak-Tend interval (TpTe) has been linked to increased arrhythmic risk. TpTe was investigated before and after primary percutaneous coronary intervention (pPCI) in patients with ST-segment elevation myocardial infarction (STEMI).

Method

Patients with first-time STEMI treated with pPCI were included (n = 101; mean age 62 years; range 39-89 years; 74% men). Digital electrocardiograms were taken pre- and post-PCI, respectively. Tpeak-Tend interval was measured in leads with limited ST-segment deviation. The primary end point was all-cause mortality during 22 ± 7 months (mean ± SD) of follow-up.

Results

Pre- and post-PCI TpTe were 104 milliseconds [98-109 milliseconds] and 106 milliseconds [99-112 milliseconds], respectively (mean [95% confidence interval], P = .59). A prolonged pre-PCI TpTe was associated with increased mortality (hazard ratio, 10.5 [1.7-20.4] for a cutoff value of 100 milliseconds). Uncorrected QT and heart rate-corrected QT intervals (Fridericia-corrected QT) were prolonged after PCI (QT: 401 vs 410 milliseconds, P = .022, and Fridericia-corrected QT: 430 vs 448 milliseconds, P < .0001).

Conclusion

In patients with STEMI undergoing pPCI, pre-PCI TpTe predicted subsequent all-cause mortality, and the QT interval was increased after the procedure.     

Ventricular arrhythmia is predicted by sum absolute QRST integralbut not by QRS width

Background

There is a controversy regarding the association between QRS width and ventricular arrhythmias (VAs). We hypothesized that predictive value of the QRS width could be improved if QRS width were considered in the context of the sum magnitude of the absolute QRST integral in 3 orthogonal leads sum absolute QRST integral (SAI QRST). We explored correlations between QRS width, SAI QRST, and VA in primary prevention implantable cardioverter-defibrillator (ICD) patients with structural heart disease.

Methods

Baseline orthogonal electrocardiograms were recorded at rest in 355 patients with implanted primary prevention ICDs (mean age, 59.5 ± 12.4 years; 279 male [79%]). Patients were observed prospectively at least 6 months; appropriate ICD therapies because of sustained VA served as end points. The sum magnitude of the absolute QRST integral in 3 orthogonal leads (SAI QRST) was calculated.

Results

During a mean follow-up of 18 months, 48 patients had sustained VA and received appropriate ICD therapies. There was no difference in baseline QRS width between patients with and those without arrhythmia (114.9 ± 32.8 vs 108.9 ± 24.7 milliseconds; P = .230). SAI QRST was significantly lower in patients with VA at follow-up than in patients without VA (102.6 ± 27.6 vs 112.0 ± 31.9 mV·ms; P = 0.034). Patients with SAI QRST (≤145 mV·ms) had a 3-fold higher risk of ventricular tachycardia (VT)/ventricular fibrillation (VF) (hazard ratio [HR], 3.25; 95% confidence interval [CI], 1.59-6.75; P = .001). In the univariate analysis, QRS width did not predict VT/VF. In the bivariate Cox regression model, every 1 millisecond of incremental QRS widening with a simultaneous 1 mV·ms SAI QRST decrease raised the risk of VT/VF by 2% (HR, 1.02; 95% CI, 1.01-1.03; P = .005).

Conclusion

QRS widening is associated with ventricular tachyarrhythmia only if accompanied by low SAI QRST.     

The relationship between mitral papillary muscles positions and characteristics of the QRS complex

Background

QRS complex characteristics are considered to be one of the most significant diagnostic and prognostic determinants for assessment of several cardiac conditions. However, there is a large variability of the QRS complex even among “normal” individuals.This study was based on 2 assumptions: (1) that the portion of the left ventricular endocardium activated earliest is directly supplied by the “fanlike” distribution of the anterior, middle, and posterior fascicles of the left bundle branch, and (2) that the anterior and posterior fascicles course toward their respective mitral papillary muscles. These structures could therefore serve as anatomical landmarks to indicate the borders of this fanlike distribution of primary “start points” of left ventricular activation.

Aims

The primary aim of this study is to test the hypothesis that location of both papillary muscles closer to the septum correlates with longer QRS duration. The secondary aim of the study is to test the hypothesis that the balance of the distances of the anterior and posterior papillary muscles from the septum is related to the direction of the frontal plane QRS axis.

Methods

The study population consisted of 16 healthy adult volunteers with a mean age of 26 ± 9 years, mean height of 170 ± 12 cm, and mean weight of 68 ± 10 kg. Measurements were done on the magnetic resonance images from all study subjects. Positions of papillary muscles were assessed as a predictive variable of QRS duration.

Results

A significant correlation was found between the closer position of both papillary muscles to the septum and longer QRS duration (R = 0.7, P = .02). Subjects with higher ratio of anterior papillary muscle vs posterior papillary muscle free wall angle correlates with inferior rotation of the average axis of QRS complex in the frontal plane (R = 0.5, P = .04).

Conclusions

The positions of the papillary muscles in relation to the free wall and septum wall can be predictive of both QRS duration and the direction of the QRS complex of the heart. These results might provide a new basis for prediction of QRS complex characteristics of an individual and, thus, differentiate between real QRS complex abnormalities and variants of normal.     

The decrease in QRS amplitude after aortic valve replacement in patients with aortic valve stenosis

Purpose

The purpose of this study was to evaluate the effect of aortic valve replacement on electrocardiogram (ECG) in patients with aortic valve stenosis.

Methods

Serial 12-lead ECGs were obtained in 15 patients with aortic valve stenosis who underwent aortic valve replacement. Three ECG indexes for left ventricular hypertrophy were manually measured in each ECG: Sokolow-Lyon index (sum of S wave in V₁ and R wave in V₅), Cornell voltage index (sum of R wave in aVL and S wave in V₃), and Gubner index (sum of R wave in I and S wave in III).

Results

After aortic valve replacement, Sokolow-Lyon index gradually decreased during 2 years (51.1 ± 17.9 to 34.8 ± 12.5 mm, P < .01). Cornell voltage index (25.6 ± 7.0 to 15.0 ± 4.8 mm, P < .01) and Gubner index (15.8 ± 7.6 to 10.3 ± 5.5 mm, P < .01) also gradually decreased during 2 years. ST depression in V₆ was found in 14 patients (93%) before aortic valve replacement. It resolved in 9 of 14 patients during 2 years.

Conclusions

Electrocardiographic evidence of left ventricular hypertrophy gradually resolved after aortic valve replacement in patients with aortic valve stenosis.     

Relation of admission QRS duration with development of angiographic no-reflow in patients with acute ST-segment elevation myocardial infarction treated with primary percutaneous interventions

Background

Although QRS-complex changes during ischemia have been described previously, their relation with no-reflow is not clear.

Purpose

To evaluate relation of admission QRS duration with angiographic no-reflow, we studied 162 patients who underwent primary angioplasty.

Methods

Twelve-lead electrocardiogram with a paper speed of 50 mm/s was recorded on admission and repeated after angioplasty. Patients were divided into reflow and no-reflow groups based on postangioplasty coronary thrombolysis in myocardial infarction flow grade.

Results

Patients in the no-reflow group (26 patients) were older (P = .001) and had significantly longer pain-to-balloon interval (P = .007). The patients in the no-reflow group had significantly longer QRS duration on admission electrocardiogram compared with patients in the reflow group (interquartile range, 80-93 [median, 84] milliseconds vs 60-80 [median, 76] milliseconds, respectively; P < .001). After adjusting all variables, QRS duration on admission was found to be independently related to angiographic no-reflow (odds ratio, 1.07; 95% confidence interval, 1.02-1.12; P = .003).

Conclusion

QRS duration on admission may be valuable in predicting no-reflow.     

Grade 3 ischemia on the admission electrocardiogram is associated with severe microvascular injury on cardiac magnetic resonance imaging after ST elevation myocardial infarction

Background

Grade 3 ischemia during ST elevation myocardial infarction (STEMI) is defined as ST elevation with distortion of the terminal portion of the QRS on electrocardiogram (ECG). The aim of this study was to evaluate the effect of ischemic grade on cardiac magnetic resonance (CMR) imaging infarct characteristics such as infarct size, microvascular obstruction (MVO), intramyocardial hemorrhage (IMH), and myocardial salvage.

Methods

Patients with STEMI treated with primary percutaneous coronary intervention had a 12-lead ECG on presentation for analysis of ischemic grade. Gadolinium-enhanced CMR imaging was performed within 7 days to assess infarct size, MVO, IMH, and myocardial salvage.

Results

Of the 37 patients enrolled in the study, grade 3 ischemia was present in 32%. Those with grade 3 ischemia had higher peak troponin I levels (P = .013), more MVO (P < .001), more IMH (P < .001), larger infarct size (P = .025), and less myocardial salvage (P = .012). Regression analysis found that grade 3 ischemia, infarct size, and peak troponin I level were significantly associated with MVO and IMH.

Conclusion

Grade 3 ischemia on the admission ECG during STEMI is closely associated with the development of severe microvascular damage on CMR imaging.     

Comparison of serial measurements of infarct size and left ventricular ejection fraction by contrast-enhanced cardiac magnetic resonance imaging and electrocardiographic QRS scoring in reperfused anterior ST-elevation myocardial infarction

Background

Left ventricular ejection fraction (LVEF) is a powerful prognostic marker after acute myocardial infarction and is dependent on infarct magnitude. Contrast-enhanced cardiac magnetic resonance (ceCMR) represents the current criterion standard means of LVEF and infarct size measurement. Infarct size and LVEF can be estimated from the 12-lead electrocardiogram (ECG) using the Selvester QRS score. We examined for the first time the relationship between serial measures of LVEF and infarct size by ceCMR and ECG in patients with reperfused anterior ST-elevation myocardial infarction (STEMI) and depressed LVEF.

Methods

Thirty-four patients (mean ± SD age, 59 ± 11.8 years; 70.6% male) underwent ceCMR and simultaneous ECG at mean 93 hours after admission and at 12 and 24 weeks. The QRS score was calculated on each ECG, from which infarct size and LVEF were estimated and compared with the equivalent ceCMR measurements.

Results

Infarct size on ceCMR was higher than that by QRS score at each time-point (P < .001) with modest correlation (r = 0.56-0.78, P < .001). Left ventricular ejection fraction was consistently significantly higher on CMR than on ECG, with weak correlation (r = 0.37-0.51, P < .05). We derived a novel equation relating QRS score to CMR-measured LVEF in the subacute phase of infarction: LVEF = 61 − (1.7 × QRS score) (%).

Conclusions

In patients with reperfused anterior ST-elevation myocardial infarction and depressed LVEF, ceCMR is moderately correlated with the QRS in the serial measurement of infarct size and LVEF. Infarct size (measured by ceCMR) and LVEF are consistently higher than those calculated on the QRS score in the acute and subacute phases of infarction.     

Prognostic value of predischarge electrocardiographic measurement of infarct size after thrombolysis: insights from GUSTO I Economics and Quality of Life substudy

Background

Current methods for risk stratification after acute myocardial infarction (MI) include several noninvasive studies. In this cost-containment era, the development of low-cost means should be encouraged. We assessed the ability of an electrocardiogram (ECG) MI-sizing score to predict outcomes in patients enrolled in the Economics and Quality of Life (EQOL) sub study of the Global Utilization of Streptokinase and Tissue plasminogen activator for Occluded coronary arteries -I (GUSTO-I) trial.

Methods

We classified patients by electrocardiographic Selvester QRS score at hospital discharge: those with a score 0-9 versus ≥10. Endpoints were 30-day and 1-year mortality, resource use, and quality-of-life measures.

Results

Patients with a QRS score <10 were well-matched with those with QRS score ≥10 with the exception of a trend to more anterior MI in the higher scored group. Patients with QRS score ≥10 had increased risk of death at 30-days (8.9% vs. 2.9% P < .001), and this difference persisted at 1 year (12.6% vs. 5.4%, P = .001). Recurrent chest pain, use of angiography, and angioplasty were similar during follow-up. However, there was a trend toward less coronary bypass surgery in patients with a QRS score ≥10. Readmission rates were higher at 30 days but similar at 1 year.

Conclusions

Stratification of patients after acute MI by a simple measure of MI size identifies populations with different long-term prognoses; patients with a QRS score ≥10 (approximately 30% of the left ventricle infarcted) at discharge have poorer outcomes in both the short- and long-term. The standard 12-lead ECG provides a simple, economical means of risk stratification at discharge.     

Consideration of QRS complex in addition to ST-segment abnormalities in the estimated "risk region" during acute anterior myocardial infarction

Background

The myocardial area at risk (MaR) has been estimated in patients with acute myocardial infarction (AMI) by using ST segment-based electrocardiographic (ECG) methods. As the process from ischemia to infarction progresses, the ST-segment deviation is typically replaced by QRS abnormalities causing a falsely low estimated total MaR if determined by using ST segment-based methods. The purpose of this study was to investigate if consideration of the abnormalities in the QRS complex, in addition to those in the ST segment, provides a more accurate estimated total MaR during anterior AMI than by considering the ST segment alone.

Methods

Twenty-five patients with acute anterior ST elevation myocardial infarction (STEMI) received technetium Tc 99m-sestamibi before percutaneous coronary intervention. Single photon emission computed tomography (SPECT) was performed within 2 hours after treatment and was used as a criterion standard for the estimated total MaR. The ECG recorded at admission in the hospital was used for the ECG estimated total MaR. This included an ST-segment estimated ischemic component of the total MaR (Aldrich score) and an estimated infarcted component of the total MaR in the acute phase of AMI by QRS abnormalities (Selvester score). These scores were added for the combined ECG score.

Results

The ischemic component of the total MaR estimated by the Aldrich score alone had no statistically significant correlation with SPECT (r = 0.21, P = .32). The infarcted component of the total MaR estimated by the Selvester score showed a significant correlation with SPECT (r = 0.49, P = .01). Each score gave a significant underestimated total MaR measured by SPECT (P < .01). When the Aldrich and Selvester scores were combined, the correlation with SPECT was r = 0.47, P = .02. The combined score still underestimated the total MaR by SPECT (P < .01), though the difference was smaller in comparison to either method alone (P < .01).

Conclusion

The ECG estimated total MaR was more accurate by taking both ST deviation and QRS abnormalities into account than by using either method alone. A new ECG method to determine the total MaR during acute coronary occlusion should consider both its ischemic and infarcted components.     

Electrocardiographic reference ranges derived from 79,743 ambulatory subjects

Background

Reference ranges for electrocardiogram (ECG) intervals, heart rate, and QRS axis in general use by medical personnel and ECG readers are unrepresentative of true age- and sex-related values in large populations and are not based on modern electrocardiographic and ECG reading technology.

Methods and Results

The results of ECG interpretation by cardiologists using digital technology for viewing and interpreting ECGs were compiled from single, baseline ECGs of 79,743 individuals included in pharmaceutical company-sponsored clinical trials. Women comprised 48% of the total population. Ages ranged from 3 months to 99 years, and the bulk of the population (56%) was aged 40 to 70 years. Striking differences in numerical ECG values based on age and sex were observed. A subgroup of 46,129 individuals with a very low probability of cardiovascular disease was identified. The following were the reference ranges for this subgroup, determined using the 2nd and 98th percentiles: heart rate, 48 to 98 beats/min; PR interval, 113 to 212 milliseconds; QRS interval, 69 to 109 milliseconds; frontal plane QRS axis, −40° to 91°; QT interval, 325 to 452 milliseconds; QTc-Bazett, 361 to 457 milliseconds; and QTc-Fridericia, 359 to 445 milliseconds. There were marked age- and sex-related variations in the reference ranges of this subgroup, and they differ substantially from previously reported norms. Small differences were observed in ECG values obtained using our digital methods as compared with readings done using paper tracings and values computed by 2 commercial computer algorithms.

Conclusions

We observed large differences in electrocardiographic heart rate, interval, and axis reference ranges in this study compared with those reported previously and with reference ranges in general use. We also observed a large influence of age and sex upon normal values. Very large cohorts are required to fully assess age- and sex-related variation of reference ranges. Electrocardiographic reference ranges should be modernized.     

Does modifying electrode placement of the 12 lead ECG matter in healthy subjects?

Background

Limb electrodes for the 12 lead ECG are routinely placed on the torso during exercise stress testing or when limbs are clinically inaccessible. It is unclear whether such electrode modification produces ECG changes in healthy male or female subjects that are clinically important according to the 2009 AHA, ACCF, HRS guidelines. We therefore measured whether ECG modification produced clinically important or false positive ECG changes e.g., appearance of Q waves in leads V_1-3, ST changes greater than 0.1 mV, T wave changes greater than 0.5 mV (frontal plane) or 1 mV (transverse plane), QRS axis shifts or alterations to QTc/P-R/QRS intervals.

Methods

The 12 lead ECG was measured in 18 healthy and semi-recumbent subjects using the standard and Takuma modified limb placements.

Results

In the frontal plane we demonstrate that the modification of limb electrode placement produces small Q, R and T wave amplitude and QRS axis changes that are statistically but not clinically significant. In the transverse plane it produces no statistically or clinically significant changes in the ECG or in ST segment morphology, P-R, QRS or QTc intervals.

Conclusions

We provide better and more robust evidence that routine modification of limb electrode placement produces only minor changes to the ECG waveform in healthy subjects. These are not clinically significant according to the 2009 guidelines and thus have no effect on the clinical specificity of the 12 lead ECG.     

Comparison of the correlation of the Selvester QRS scoring system with cardiac contrast-enhanced magnetic resonance imaging-measured acute myocardial infarct size in patients with and without thrombolytic therapy

Background

After an acute myocardial infarction (MI), it is important to define the infarct size because it is related to mortality and morbidity. The Selvester QRS Score is an electrocardiographic (ECG) method that has been developed for estimating MI size. It has been shown to correlate well with postmortem anatomically measured sizes of single MI in patients who did not receive thrombolytic therapy. The aim of this study was to test the hypothesis that correlation between Selvester QRS Score-estimated MI size and contrast-enhanced magnetic resonance imaging (ceMRI)-measured MI size is equivalent in patients who did vs those who did not receive thrombolytic therapy.

Methods

Thirty-six patients with MI (24 with thrombolytic therapy and 12 without) received ceMRI and ECG at admission and at 1 or 6 months after admission. Indeed, in 23 of the patients, the therapy was intravenous only. The Selvester QRS Score was calculated using the 1-month ECG or, if not available, the 6-month ECG. The correlation between the 2 measures of MI size was determined for all patients and for the 2 groups separately.

Results

The mean MI size in the group that did not receive thrombolytic therapy was 8.5% ± 6.4% estimated by the Selvester QRS Score and 11.7% ± 10.2% measured by ceMRI. For the group that received thrombolytic therapy, Selvester QRS Score was 13.9% ± 11.1% and ceMRI was 20.2% ± 11.3%. The mean MI size in both groups combined was 12.1% ± 10.0% estimated by the Selvester QRS Score and 17.3% ± 11.5% measured by ceMRI. The Spearman rank correlation coefficient between Selvester QRS Score and ceMRI was 0.74 (P < .0001) for all patients, 0.74 (P < .0001) for the group that received thrombolytic therapy, and 0.64 (P = .024) for the group that did not receive thrombolytic therapy.

Conclusions

The associations between Selvester QRS Score and ceMRI-based MI were statistically significant and similar in both groups.     

Comparison of infarct size changes with delayed contrast-enhanced magnetic resonance imaging and electrocardiogram QRS scoring during the 6 months after acutely reperfused myocardial infarction

Introduction

Magnetic resonance imaging using the delayed contrast-enhanced (DE-MRI) method can be used for characterizing and quantifying myocardial infarction (MI). Electrocardiogram (ECG) score after the acute phase of MI can be used to estimate the portion of left ventricular myocardium that has infracted. There are no comparison of serial changes on ECG and DE-MRI measuring infarct size.

Aim

The general aim of this study was to describe the acute, healing, and chronic phases of the changes in infarct size estimated by the ECG and DE-MRI. The specific aim was to compare estimates of the Selvester QRS scoring system and DE-MRI to identify the difference between the extent of left ventricle occupied by infarction in the acute and chronic phases.

Methods

In 31 patients (26 men, age 56 ± 9) with reperfused ST-elevation MI (11 anterior, 20 inferior), standard 12-lead ECG and DE-MRI were taken from 1 to 2 days (acute), 1 month (healing), and 6 months (chronic) after the MI. Selvester QRS scoring was used to estimate the infarct size from the ECG.

Results

The correlation values between infarct size measured by DE-MRI and QRS scoring range from 0.33 to 0.43 higher for anterior than inferior infarcts. The infarct size estimated by QRS scoring was larger (about 5% of the left ventricle) than infarct size by DE-MRI acute and 1 month, but at 6 months, there was no difference. In about half of the patients, the QRS score agreed with DE-MRI in change of infarct size from acute to 6 months.

Conclusion

In conclusion, the Selvester QRS scoring system is in half of the patients with reperfused first time MI in good accordance with DE-MRI in identifying a decrease or no change in the extent of left ventricle occupied by infarction in the acute and chronic phases.     

Simulation of the QRS complex using papillary muscle positions as the site of early activation in human subjects

Background

Simulation of the electrical activation of the heart and its comparison with real in vivo activation is a promising method in testing potential determinants of excitation. Simulation of the electrical activity of the human heart is now emerging as a step forward for understanding and predicting electrophysiologic patterns in humans. Initial points of excitation and the manner in which the activation spreads from these points are important variables determining QRS complex characteristics. It has been suggested that in humans, the initial excitation of the left ventricle is a primary determinant of QRS complex characteristics, and that excitation begins at the papillary muscles and septum, where the fascicles of the left bundle branch insert. The aim of this study is to test the hypothesis that QRS duration and direction of QRS axis in the frontal plane have excellent agreement between real QRS and simulated QRS using papillary muscle position to indicate the border of the origin of early ventricular activation.

Methods

Fourteen healthy adult volunteers were included in the study. Magnetic resonance imaging data were obtained to assess the papillary muscle positions. Twelve-lead electrocardiographic (ECG) recordings were used to obtain real ECG data for assessment of QRS duration and QRS axis in each subject. Simulation software developed by ECG-TECH Corp (Huntington, NY) was used to simulate the ECG of each subject to determine simulated QRS duration and QRS frontal plane axis. QRS duration and QRS axis data were compared between simulated and real ECG and agreement between these variables was calculated.

Results

Seventy-nine percent of subjects had a difference of the QRS duration between real and simulated ECG of less than 10 milliseconds. The calculated strength of agreement between simulated and real QRS duration was 71% and considered as “good” (κ statistics). In 70% of subjects, the difference in the QRS axis was less than 10°. The calculated strength of agreement between simulated and real QRS axis was 80% and considered as “excellent” (κ statistics).

Conclusions

The results of this study suggest that the sites of the initiation of electrical activity in the left ventricle, as assessed by the positions of papillary muscles, may be considered as primary determinants of the QRS duration and QRS axis in humans. This knowledge may help in predicting normal QRS characteristic on a patient-specific basis. In this study, simulation of the QRS complex was based on papillary muscles from human hearts.     

Electrocardiographic findings in cardiogenic shock, risk prediction, and the effects of emergency revascularization: results from the SHOCK trial

Objectives

To evaluate electrocardiographic (ECG) parameters as predictors of 1-year mortality in patients developing cardiogenic shock after acute myocardial infarction (AMI), and to document associations between these ECG parameters and the survival benefit of emergency revascularization versus initial medical stabilization.

Background

Emergency revascularization reduces the risk of mortality in patients developing cardiogenic shock after AMI. The prognostic value of ECG parameters in such patients is unclear, and it is uncertain whether emergency revascularization reduces the mortality risk denoted by ECG parameters.

Methods

In a prospective substudy of 198 SHOCK (SHould we emergently revascularize Occluded Coronaries for cardiogenic shocK) trial patients, ECGs recorded within 12 hours of shock were interpreted by personnel blinded to the patients' treatment assignment and outcome.

Results

The baseline heart rate was higher in non-survivors than in survivors (106 ± 20 versus 95 ± 24 beats/minute, P = .001). There was a significant association between the QRS duration and 1-year mortality in medically stabilized patients (115 ± 28 ms in non-survivors versus 99 ± 23 ms in survivors, P = .012), but not in emergently revascularized patients (110 ± 31 versus 116 ± 27 ms respectively, P = .343). The interaction between the QRS duration, mortality and treatment assignment was significant (P = .009). Among patients with inferior AMI, a greater sum of ST depression was associated with higher 1-year mortality in medically stabilized patients (P = .029), but not in emergently revascularized patients (P = .613, treatment interaction P = .025). On multivariate analysis, the independent mortality predictors were increasing age, elevated pulmonary capillary wedge pressure, heart rate, sum of ST depression in medically stabilized patients, and interaction (P = .016) between a prolonged QRS duration and treatment assignment. The adjusted hazard ratio for 1-year mortality per 20 ms increase in the QRS duration was 1.19 (95% CI 0.98-1.46) in medically stabilized patients and 0.81 (95% CI 0.63-1.03) in emergently revascularized patients.

Conclusion

ECG parameters identified patients with cardiogenic shock who were at high risk. Emergency revascularization eliminated the incremental mortality risk associated with cardiogenic shock in patients with a prolonged QRS duration, or inferior AMI accompanied by precordial ST depression. Prospective assessments of the magnitude of the treatment effect based on ECG parameters are required.     

Determinants of the total cosine of the spatial angle between the QRS complex and the T wave (TCRT): implications for distinguishing primary from secondary T-wave abnormalities

Background

Contrary to intuitive expectations and dissimilar from that which occurs in the atria, left ventricular (LV) depolarization and repolarization proceed in opposite directions, creating a concordance of the spatial QRS complex and T-wave angles (QRS-T). By defining the determinants of QRS-T, it might be possible to distinguish a primary (caused by an abnormality of repolarization) from a secondary (caused by a delay in ventricular depolarization) T-wave abnormality.

Methods and Results

From a near-consecutive series of 154 patients (age, 60 ± 16 years; 81 females) in sinus rhythm, Doppler echocardiographic and 12-lead electrocardiogram (ECG) findings were related to the total cosine of the angle subtended by the spatial QRS complex and T wave (TCRT). Using the QRS complex and T-wave angles in the frontal and horizontal planes, TCRT was obtained from the table cited in the article of Helm and Fowler (Am Heart J 1953;45:835). TCRT correlated negatively with age, QRS duration (QRS), interventricular septal thickness (IVS) and posterior wall thickness, LV mass, LV cross-sectional area (CSA), LV relative wall thickness (RWT), left atrial dimension, and atrial velocity time integral (all, P < .001), but it was not related to LV diastolic dimension or systolic function. In multivariate analyses of the entire cohort or of patients without a left bundle branch block, QRS, CSA, RWT, and atrial velocity time integral emerged as independent variables (all, P < .001). When patients with right bundle branch block were also excluded, IVS, instead of CSA and RWT, was significant (P < .001). Overall, TCRT distinguished normal patients from those with heart disease, and patients with diabetes mellitus and hypertension from those not having these conditions. However, residuals of regression, TCRT = (−1.6IVS [cm]) + (−0.01QRS [milliseconds]) + 3, distinguished patients with coronary disease, but not other disorders, from normals, and diabetics, but not patients with hypertension or hyperlipidemia, from those not having these conditions (the regression having adjusted for secondary QRS-T discordance).

Conclusions

The determinants of TCRT can be quantified and expressed as a regression that may be used to distinguish primary from secondary T-wave abnormalities.