Difference In QRS Duration Research Articles

Left ventricular hypertrophy

Left ventricular hypertrophy

What Resulted in the Increase of Primary Prevention by Cardiac Resynchronization Therapy with Defibrillation (CRT-D) in Japan?

MADIT-CRT trial and REVERSE trial recommended the implantation of CRT-D in patients with a relatively early phase of heart failure (HF) and electrocardiac disturbance (ED). The primary prevention by CRT-D has already increased for recent days in Japan. However, it is little known what caused an increase of implantation of CRT-D. Methods: We investigated 3267 patients (66±11 years old) with newly implanted CRT-D in data-base of JCDTR. The clinical characteristics were compared between primary and secondary prevention. Further, we investigated the transition of percentage of primary prevention, LVEF, QRS duration and NYHA functional class at the implantation for the latest 5 years. Results: Subjects were divided into two group, primary (n=2073; 63%) and secondary prevention (n=1194; 37%). The clinical characteristics of primary prevention were relatively elder, lower LVEF, higher NYHA functional class and higher degree of LV dyssynchrony. However, there was no significant difference in QRS duration. The percentage of primary prevention of CRT-D has significantly increased from 50% to 69%. But, the percentages of NYHA I/II, LVEF>35% and QRS duration <130 msec did not significantly change for 5 years in the primary prevention group. Conclusion: Though the primary prevention of CRT-D has increased for 5 years, this did not result from the increase of patients with a relatively early phase of HF and ED.

Prevalence and Pathophysiologic Attributes of Ventricular Dyssynchrony in Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy

This study sought to investigate the prevalence and mechanisms underlying right ventricular (RV) dyssynchrony in arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) using tissue Doppler echocardiography (TDE). An ARVD/C is characterized by fibrofatty replacement of RV myocardium and RV dilation. These pathologic changes may result in electromechanical dyssynchrony. Echocardiography, both conventional and TDE, was performed in 52 ARVD/C patients fulfilling Task Force criteria and 25 control subjects. The RV end-diastolic and -systolic areas, right ventricular fractional area change (RVFAC), and left ventricular (LV) volumes and function were assessed. Mechanical synchrony was assessed by measuring differences in time-to-peak systolic velocity (T(SV)) between the RV free wall, ventricular septum, and LV lateral wall. An RV dyssynchrony was defined as the difference in T(SV) between the RV free wall and the ventricular septum, >2 SD above the mean value for control subjects. The mean difference in RV T(SV) was higher in ARVD/C compared with control subjects (55 +/- 34 ms vs. 26 +/- 15 ms, p < 0.001). Significant RV dyssynchrony was not noted in any of the control subjects. Based on a cutoff value of 56 ms, significant RV dyssynchrony was present in 26 ARVD/C patients (50%). Patients with RV dyssynchrony had a larger RV end-diastolic area (22 +/- 5 cm(2) vs. 19 +/- 4 cm(2), p = 0.02), and lower RVFAC (29 +/- 8% vs. 34 +/- 8%, p = 0.03) compared with ARVD/C patients without RV dyssynchrony. No differences in QRS duration, LV volumes, or function were present between the 2 groups. An RV dyssynchrony may occur in up to 50% of ARVD/C patients, and is associated with RV remodeling. This finding may have therapeutic and prognostic implications in ARVD/C.

QRS Duration, an Indirect Reflection of Ventricular Synergy, Is Not Altered in Decompensated Heart Failure

QRS duration is frequently used to identify left ventricular dyssynchrony and is a primary qualification for cardiac resynchronization therapy. While QRS duration can be wider with higher heart rates due to aberrant conduction, there is little information on fluctuations of QRS duration due to decompensated heart failure, which is relevant with regard to optimal timing to assess patients for cardiac resynchronization therapy (CRT). Therefore, we sought to identify and characterize fluctuations of QRS duration during inhospital treatment for acute decompensated heart failure (ADHF).We analyzed the medical records of all patients admitted to our cardiology service for ADHF. Demographic and clinical data were obtained including analysis of initial and discharge electrocardiogram for QRS duration and determination of left ventricular systolic function. Data were obtained on 107 patients. There was no significant difference in QRS duration from admission to discharge during which patients' clinical status improved from ADHF to the compensated state. Subgroup analysis also did not reveal significant differences in QRS duration in this patient population.QRS duration did not change significantly in these patients during acute heart failure exacerbation or its resolution.

Pulmonary Hypertension Affects Left Ventricular Basal Twist: A Novel Use for Speckle‐Tracking Imaging

Chronic pulmonary hypertension (PH) results in right ventricular (RV) mechanical dyssynchrony. However, its effects on left ventricular (LV) mechanics have not been examined. Since speckle-tracking echocardiography (STE) is a novel approach to quantify LV dyssynchrony; we decided to use STE to assess the effect of PH on LV mechanics. Our echocardiography database was queried for patients with PH who had undergone STE analysis and compared to similarly collected data from a group of healthy volunteers. Group I (15 patients, age of 53 +/- 17 years, pulmonary artery pressure of 62 +/- 20 mmHg, eccentricity index of 0.78 +/- 0.06, and LV ejection fraction of 64 +/- 11%) and Group II (8 healthy volunteers, age 41 +/- 9 years, pulmonary artery pressure 14.6 +/- 4.2 mmHg, eccentricity index of 1.02 +/- 0.05, and LV ejection fraction of 66 +/- 6 mmHg). There was no difference in QRS duration between the two groups. Although PH significantly altered basal LV twist (Group I: M =-5.76 degrees versus Group II: M =-1.82 degrees , P < 0.05), it had no effect on LV apical twist (5.29 degrees versus 4.50 degrees ; P = NS, respectively). More notably, significant LV radial basal LV dyssynchrony, measured as the time to peak LV basal twist, was seen as a result of PH. STE identifies the presence of LV dyssynchrony in PH despite normal LV ejection fraction and no difference in QRS duration. Additional studies are now required to further characterize these results and determine their prognostic significance.

Abstract 636: Conduction Delay in Right Ventricle as a Marker for Identifying High-Risk Patients in Brugada Syndrome

BACKGROUND In Brugada syndrome (BS), abnormal conduction delay in right ventricle has been reported. However, the meaning of the conduction delay for risk stratification in BS is still unclear. OBJECTIVES To evaluate the significance of conduction delay in patients with BS as a marker for risk stratification. METHODS Twenty-four patients with BS in whom pilsicainide challenge test was performed (documented VF: N = 7, syncope: N = 7, and asymptomatic: N = 10) were paced from right ventricular apex (RVA), using a basic cycle length of 500ms (8 beats) and a single extrastimulus. A 2.5-French 16-electrode catheter was positioned into the coronary sinus and the great cardiac vein to record intracardiac electrograms on the epicardial sites in right ventricular outflow tract area (RVOT) and lateral left ventricle (l-LV). We measured the conduction time from the stimulus artifact at RVA to the epicardial ventricular electrogram at RVOT or l-LV. The conduction delay between RVA and RVOT (CD-RV) or between RVA and l-LV (CD-LV) was defined as the time interval between the ventricular response at RVOT (RV-V1V2) or at l-LV (LV-V1V2) and the stimulus coupling interval (S1S2) at RVA, respectively (CD-RV; RV-V1V2 minus S1S2, and CD-LV; LV-V1V2 minus S1S2). We also measured 12-lead ECG parameters at baseline and after pilsicainide challenge test, and evaluated the differences of the ECG parameters before and after pilsicainide challenge test. RESULTS Max CD-RV was significantly larger than max CD-LV in all patients (28±9 vs 19±7 ms, p&lt;0.05). Max CD-RV in patients with documented VF was significantly larger than that in patients without (35±10 vs 25±7 ms, p&lt;0.05). However, there was no significant difference in max CD-RV and CD-LV between patients with induced VF and those without (30±9 and 20±5 vs 26±7 and 21±7 ms, p=NS). There was significant positive correlation between max CD-RV and the differences in QRS duration in leads V1, V2, and V6 after pilsicainide administration (r = 0.51, 0.53, and 0.48, respectively, p&lt;0.05). CONCLUSIONS The conduction delay in right ventricle (RV) was a useful marker for identifying high-risk patients in BS. The conduction delay at RV may be related to depolarization abnormality due to sodium channel dysfunction in BS.

The resynchronization therapy in narrow QRS study (RethinQ study): Methods and protocol design

Numerous trials have demonstrated the effectiveness of cardiac resynchronization therapy (CRT) as an adjunct to medical therapy for the relief of heart failure (HF) symptoms in patients with a wide QRS duration (QRSd). Current guidelines recommend CRT in patients with an EF <35%, medically refractory NYHA Class III-IV HF and QRSd >or=120 ms. Previous studies have demonstrated QRSd as a marker of electrical dyssynchrony fails to predict response to CRT. In addition, studies have demonstrated significant differences in QRSd post CRT between responders and non-responders. Moreover, smaller non-controlled studies demonstrated that HF patients with a narrow QRSd may benefit from CRT. A growing body of evidence suggests that echocardiographic criteria may be a better method to evaluate mechanical dyssynchrony (MD) which may predict those that will benefit from CRT, particularly those with a narrow QRSd. The Resynchronization Therapy In Narrow QRS (RethinQ) study will evaluate mechanical dyssynchrony using echocardiography (both M mode and TDI) as an eligibility requirement for CRT. The RethinQ study is a prospective, multi-center, randomized, double blind controlled clinical study. The objective of the RethinQ study is to evaluate the effectiveness of CRT in patients with approved ICD indication, advanced HF (NYHA Classification III), narrow QRSd (<130 ms) and evidence of MD measured by echocardiography. We hypothesize that patients with narrow QRS <130 ms, advanced HF, and MD as measured by echocardiography will benefit from CRT.

Analysis of fetal cardiac conduction times in twin pregnancy using magnetocardiography

Abstract. Aim of this work was to compare fetal cardiac time intervals (CTI) in twin and singleton pregnancies taking gestational age into account. Eighteen fetal magnetocardiograms were obtained in 14 twin fetuses (28th–38th week of gestation). In the signal averaged fetal PQRST courses, the following CTI were determined: P wave, PR interval, PQ interval and QRS complex. The CTI of 228 magnetocardiograms from 47 singleton fetuses served as controls. The CTI of both groups were compared using a regression model including gestational age and singleton/twin status. Atrioventricular conduction and ventricular depolarization times could be determined reliably. Regression analysis showed that P, PQ and PR duration were significantly shorter in the twin fetuses than in the control group (3.7 ms, p = 0.020; 6.5 ms, p = 0.050; 10.2 ms, p = 0.004; respectively). No difference in QRS duration was found. Values for birth weight, length and head circumference were significantly lower in the twin fetuses. The results show that, in twin pregnancy, reduced fetal size and weight may be reflected in shorter CTI, in particular those associated with atrioventricular conduction. The values obtained here are however not as low as those in previously published values found in growth retarded fetuses.

Acute biventricular pacing after cardiac surgery has no influence on regional and global left ventricular systolic function

Cardiac resynchronization therapy has been shown to improve systolic function in patients with advanced chronic heart failure and electromechanical delay (QRS width > 120 ms). However, the effect of acute biventricular (BiV) pacing on perioperative haemodynamic changes is not well defined. In the present study, acute changes in regional left ventricular (LV) systolic function determined by tissue Doppler imaging (TDI) and global LV systolic function determined by the continuous cardiac output method were measured during various pacing configurations in patients with depressed LV systolic function undergoing heart surgery. Twenty-six patients (age 68 +/- 8 years, 15 males) with depressed systolic LV function (LV ejection fraction <or=35%), symptomatic heart failure, and a QRS duration of > 120 ms undergoing temporary epicardial BiV pacing after aortocoronary bypass and valve surgery were included. QRS duration on surface electrocardiogram (ECG), TDI (systolic velocities of septal and lateral mitral annulus), cardiac index (CI), right atrial pressure, pulmonary artery pressure (PAP), and pulmonary capillary wedge pressure (PCW) were measured during various pacing configurations [no pacing (intrinsic rhythm), right atrial-biventricular (RA-BiV pacing), right atrial-left ventricular (RA-LV), right atrial-right ventricular (RA-RV), and AAI pacing]. There were no differences in QRS duration during intrinsic rhythm, RA-BiV pacing, and AAI pacing. However, RA-LV and RA-RV stimulations showed a longer QRS duration (P < 0.01 vs. intrinsic rhythm, RA-BiV pacing, and AAI, respectively). Tissue Doppler velocities of the septal and lateral mitral annulus were comparable in all pacing modes. Neither CI nor PAP or PCW showed significant differences during the various pacing configurations. There was a positive correlation between regional (TDI) and global (CI) parameters of LV systolic function. Conclusions Biventricular pacing after heart surgery does not improve parameters of regional and global LV systolic function acutely in patients with heart failure and intraventricular conduction delay and, thus, may not reflect changes observed with chronic BiV pacing.

Exercise Electrocardiogram Testing

Exercise testing remains the most widely accessible and relatively inexpensive method for initial evaluation of suspected coronary disease and for evaluation of its severity.1–3 Clinical usefulness has been limited, however, by poor sensitivity of standard ST-segment depression criteria for assessment of anatomic and functional coronary disease severity and for prediction of risk.1,2,4–6 Recent data make it clear that symptomatic obstructive plaques that typically result in exercise-mediated ischemia may be less relevant to infarction and sudden death than less obstructive unstable plaques.7 These limitations mandate a rethinking of the exercise ECG along 2 distinct lines: First, is it possible to improve the diagnostic value of the exercise ECG? Second, separate from its ability to diagnose obstructive coronary artery lesions, can the exercise test be used as a prognostic tool that can encourage effective prevention of premature deaths or coronary events? Both goals take us beyond the ST segment. Reversible ST-segment depression is the characteristic finding associated with exercise-induced, demand-driven ischemia in patients with significant coronary obstruction but no flow limitation at rest. This process differs from the flow-limited acute coronary syndromes because exercise-related ischemia is generally limited to the subendocardium and is proportional to increases in myocardial oxygen demand. Ventricular waveforms of the ECG can be related to the net uncanceled transmural gradients between endocardial and epicardial myocardium, as extrapolated from the work of Holland and Brooks, among others.8–10 Accordingly, isoelectric TQ and ST segments in normal and in nonischemic patients can be related to comparable resting membrane and action potential plateau voltages in endocardial and epicardial action potentials. During exercise, progressive ischemia results in changing endocardial action potentials during both diastole and systole. Less negative endocardial cell resting membrane potential leads to current flow across the ischemic boundary during diastole, leading to elevation of the TQ …

Uncertainty principle of signal-averaged electrocardiography.

Signal-averaged ECG (SAECG) reproducibility is reported to have a component that is independent of residual noise. Methods and Results-In group 1, multiple paired SAECGs were obtained to noise levels of 0.3+/-0.1 and 0.5+/-0.2 microV. For the 0.5- and 0. 3-microV noise recordings, QRS duration (QRSd) was 101.2+/-11.3 and 104.6+/-9.6 ms, respectively (P<0.0001), and the differences in paired QRSd (DeltaQRSd) were normally distributed, with variances of 11.4 and 26.2 ms(2) (P<0.0001). Paired SAECGs were obtained in group 2 patients without and with late potentials; DeltaQRSd variance was 3.3 and 217.9 ms(2) (P<0.0001). In group 3, >/=10 SAECGs were acquired at noise levels of 0.2 to 0.8 microV, in 0.1-microV increments. QRSd increased as noise level decreased. The variance was greater in low-noise (0.2 to 0.4 microV) versus higher-noise (0. 5 to 0.8 microV) recordings. In group 4, SAECGs were analyzed with bidirectional and Bispec filters, with no difference in QRSd between the 2 filters and a normally distributed DeltaQRSd. A computer simulation demonstrated that alterations in the phase relationship of noise to signal results in a normal distribution of signal end points. Within the acceptable noise range for SAECG, lower noise results in longer QRSd and larger variance, suggesting that more accurate recordings may have less reproducibility. The random timing of noise relative to signal results in the distribution/variance of repeated measurements. Statistical strategies may be used to reduce some of this variance and may enhance the diagnostic utility of SAECG.

Validation testing of the SpaceLabs PC2 ST-segment analyzer

Recent studies have demonstrated that perioperative myocardial ischemia, detected by electrocardiography, is a risk factor for myocardial infarction. ST-segment analyzers and hemodynamic monitors may be useful for on-line detection in perioperative and critical care environments. However, independent performance and accuracy standards for these devices have not been established. Therefore, a testing protocol was developed using an electrocardiogram (ECG) simulator that allowed selectively altered ST-segment displacement, in a calibrated fashion over a wide range. Laboratory bench study. Not applicable. Not applicable. Not applicable. Custom digital ECG waveform templates were programmed for use with a commercially available ECG simulator (M311 ECG simulator; Fogg Systems, Inc., Aurora, CO). For each template, ST-segment morphology (horizontal elevation or depression, downsloping depression), QRS duration, and the presence or absence of a P wave were manipulated, resulting in seven different QRS shapes. Within each shape, the degree of ST-segment deviation was altered over a wide range. A PC2 Bedside Monitor (SpaceLabs Inc., Redmond, WA) was tested. One hundred forty-eight measurements of ST-segment deviation input from the simulator were made at each of two testing sessions. The first ST-segment value displayed by the analyzer was recorded, and the two measurements averaged for comparison. Placement of the J-point, J + 60 msec, and isoelectric reference points by the analyzer were evaluated. Simulator output was validated for accuracy and stability. Subtle errors in placement of the J-point marker were observed in all seven QRS shapes. These errors usually did not alter placement of the isoelectric marker before, but not exactly at the beginning of, the R-wave upstroke. Thus, ST-segment values returned by the monitor (J + 60 msec - isoelectric reference value) were unaffected. However, in two QRS shapes, the isoelectric point was displaced onto the upstroke of the R wave, resulting in erroneous ST-segment values. In one, the error may have been caused by the difference in QRS duration of that template (120 msec) relative to the fixed 115-msec interval from the J point used by the analyzer and was present in all points tested. In the second (normal QRS duration), the error was present in some, but not all points tested (4/21, 24%). All QRS shapes with proper placement of the isoelectric point returned ST-segment values within +/- 0.5 mm of expected, and 98% were within +/- 0.25 mm of expected. The mean difference between observed and expected ST-segment values for 100 measurements with normal QRS duration and proper isoelectric point placement was 0.08 mm +/- 0.07 mm (SD). The bench results suggest that visual confirmation of ST-segment analyzer values may be advisable in the clinical setting. Although most complexes with normal conduction and a P wave are likely to be accurately analyzed, those with prolonged QRS duration were problematic. The simulator protocol may be helpful in ensuring accuracy of ST-segment analyzers, especially in their early development stages.

Gender Differences and the Electrocardiogram in Left Ventricular Hypertrophy

We examined the relations of gender differences in electrocardiographic (ECG) voltages and QRS duration to differences in cardiac dimensions and body size between men and women and gender differences in test performance of ECG criteria for the detection of echocardiographic left ventricular hypertrophy in 389 subjects (112 women and 277 men). ECG voltage-duration products were calculated as the product of QRS duration and voltages. Among subjects with normal left ventricular mass and also among subjects with left ventricular hypertrophy, men had longer QRS duration, higher Cornell voltage, higher 12-lead sum of QRS voltage, and higher Cornell and 12-lead voltage-duration products than did women. Significant gender differences in QRS duration, Cornell voltage, the 12-lead sum of voltage and their voltage-duration products remained after adjusting for the greater left ventricular mass, height, and weight in men than women. Comparison of areas under receiver operating characteristic curves using gender-specific criteria demonstrated higher performance of QRS duration, Cornell voltage, the 12-lead sum of QRS voltage, and the respective voltage-duration products for the identification of left ventricular hypertrophy in men than women. Thus, gender differences in body size and left ventricular mass do not completely account for gender differences in QRS duration and voltage measurements, and ECG criteria for left ventricular hypertrophy have lower accuracy in women even when gender differences in partition value selection are taken into account.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental right ventriculotomy: effects on local propagation at a small size scale.

Repair of tetralogy of Fallot and ventricular septal defect frequently requires righ ventriculotomy. Although the mechanisms for right bundle branch block (RBBB) have been frequently discussed, the pathogenesis of this electrocardiographic abnormality is still unknown. To determine if disruption of the distal subendocardial Purkinje fiber network in the right ventricular free wall produced RBBB and if cellular electrophysiologic abnormalities in or near the ventriculotomy scar could provide a substrate for conductance disturbances, we investigated the electrocardiographic and electrophysiologic effects of experimental right ventriculotomy in 12 beagles. On the surface electrocardiogram no significant differences in QRS duration (lead II) or morphology were apparent between the control group (n = 6) and the postventriculotomy animals (n = 6) (QRS duration = 34 +/- 4 versus 34 +/- 7 ms, respectively). Using microelectrode techniques, the right ventricular endocardial surface was carefully mapped. To facilitate analysis, data were grouped into five regions: outflow septum, outflow free wall, inflow free wall, and ventriculotomy region. No significant delays of regional activation were noted in the postventriculotomy group compared to the control group: outflow septum--30 +/- 16 versus 36 +/- 16 ms; outflow free wall--33 +/- 10 versus 38 +/- 19 ms, inflow septum--32 +/- 7 versus 33 +/- 13 ms, inflow free wall--35 +/- 11 versus 35 +/- 22 ms, and ventriculotomy region--32 +/- 10 versus 31 +/- 16 ms, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

QRS duration measurement using high-frequency electrocardiography: Applications and limitations of a new technique

Accurate, objective measurement of QRS duration is of central importance in clinical electrocardiography. The applicability of a new computer technique based on the observation that the QRS, unlike other ECG waveforms, contains significant frequencies >50 Hz was studied. Accordingly, a microprocessor-based ECG system was adapted with a signalaveraging program to reduce noise and a 50- to 300-Hz phaseless digital filter which permitted direct “extraction” of the QRS complex from surrounding low-frequency PR and ST segments. The hypothesis first tested was that, owing to greater cardiac mass, QRS duration in men should be slightly greater than in women. High-frequency QRS duration measurements were performed in 30 healthy adult men and 28 healthy adult women from simultaneously acquired orthogonal leads I and a VF. QRS duration in men (85.5 ± 12.3 msec, X ± SD ) was significantly ( p < 0.05) greater than in women (78.7 ± 11.0 msec). Furthermore, after pooling these two groups of healthy subjects ( n = 58), modest but significant ( p < 0.001) correlations were noted between QRS duration and height ( r = 0.51), weight ( r = 0.46), and body surface area ( r = 0.48). The question then addressed was whether QRS duration in patients with myocardial infarction (after excluding those with apparent conduction delays, hypertension, or axis deviation) is greater than normal due to myocardial scarring or conduction system involvement. QRS duration in 25 men with prior transmural infarction (90.6 ± 14.2 msec) was slightly greater than normal; however, this difference was not statistically significant. Furthermore, in 7 of the 25 cases (28%) QRS duration was <86 msec, the mean for normal men. These results indicate that (1) high-frequency electrocardiography provides a useful new technique capable of detecting subtle (<10 msec) differences in QRS duration between men and women; (2) body size and therefore cardiac mass is one determinant of QRS duration; and (3) QRS duration in patients with infarction overlaps with normals. Therefore, QRS duration criteria cannot be used to exclude previous infarction.