Leftward QRS Axis Research Articles

Abstract 12254: The QRS Frontal Plane Axis Changes During Left Bundle Branch Block After Transcatheter Aortic Valve Replacement

Background: Left bundle branch block (LBBB) is common after transcatheter aortic valve replacement (TAVR) and associated with either a left or normal frontal QRS axis. Research Questions: To assess the QRS frontal plane axis shift changes during LBBB after TAVR and determine if the risk of procedure-related high degree atrioventricular block (AVB) is affected by these QRS axis shift changes. Methods: In a retrospective single-center study of 720 consecutive patients who underwent TAVR, 141 (19.6%) with normal baseline QRS duration developed a new LBBB after TAVR and constituted the study group. Most patients (59.6%) were females, and the mean age of the cohort was 81.2±6 years. About two-thirds of the patients were implanted with a self-expandable valve. The length of hospital stay was 6.6±4.4 days. Results: This study show 3 main findings: 1) As compared with the baseline QRS axis before TAVR, the occurrence of LBBB after TAVR was associated with a leftward QRS axis shift (by 40+28.3°) in 73% of the study patients and a rightward (by 18.6+19.4°) or no change in QRS axis in 25.6% and 1.4% of the study patients, respectively. These results were not affected by the type and size of prosthetic valve used. 2) Although the proportion of patients having a left QRS axis (<-30°) markedly increased after TAVR in the study group (from 14.9% to 38.3%) and in the group displaying a leftward QRS axis shift (from 5.8% to 45.6%), converse results were observed in the group displaying a rightward QRS axis shift (decrease from 38.9% to 16.7%). 3) The group of patients exhibiting a rightward or no QRS axis shift tended to show a greater incidence of high degree AVB than the group of patients exhibiting a leftward QRS axis shift (18.4% vs. 6.8%, P=0.056). Conclusion: Although post TAVR-LBBB was associated with a leftward QRS axis shift in most patients (73%), a non-negligible proportion of patients (27%) exhibited a rightward or no QRS axis shift. The latter group tended to have a higher risk of developing high degree AVB.

The QRS frontal plane axis changes during left bundle branch block after transcatheter aortic valve replacement.

Left bundle branch block (LBBB) is common after transcatheter aortic valve replacement (TAVR) and associated with a left or normal QRS axis. We aim to assess the QRS frontal plane axis shift changes during LBBB after TAVR and determine if the risk of procedure-related high degree atrioventricular block (AVB) is affected by QRS axis shift changes. In a retrospective single-center study of 720 consecutive patients who underwent TAVR, 141 (19.6%) with normal baseline QRS duration developed a new LBBB after TAVR and constituted the study group. Most patients (59.6%) were females and the mean age of the cohort was 81.2±6 years. As compared with the baseline QRS axis before TAVR, the occurrence of LBBB was associated with a leftward QRS axis shift (by 40±28.3°) in 73% of the study patients and a rightward (by 18.6±19.4°) or no change in QRS axis in 25.6% and 1.4% of the study patients, respectively. A left QRS axis (-30°) was observed in 14.9% and 38.3% of the study patients before and after TAVR, respectively. The group of patients exhibiting a rightward or no QRS axis shift had a greater incidence of high degree AVB than the group of patients exhibiting a leftward QRS axis shift (18.4%vs. 6.8%, p=.056). Although post TAVR-LBBB is associated with a leftward QRS axis shift in most patients, a non-negligible proportion of patients (27%) exhibited a rightward or no QRS axis shift. The latter group tend to have a higher risk of developing high degree AVB.

Association of Age, Sex, Body Size and Ethnicity with Electrocardiographic Values in Community-based Older Asian Adults

Existing electrocardiographic (ECG) reference values were derived in middle-aged Caucasian adults. We aimed to assess the association of age, sex, body size and ethnicity on ECG parameters in a multi-ethnic Asian population. Resting 12-lead ECG and anthropometric measurements were performed in a community-based cohort of 3777 older Asians (age 64.7±9.1 years, 1467 men, 88.8% Chinese, 7.7% Malay, 3.5% Indian, body mass index [BMI] 24.0±3.9kg/m(2)). Men had longer PR interval, wider QRS, shorter QTc interval and taller SV3. In both sexes, older age was associated with longer PR interval, wider QRS, larger R aVL and more leftward QRS axis, while higher BMI was associated with longer PR interval, wider QRS, larger RaVL and more negative QRS axis. There were significant inter-ethnic differences in QRS duration among men, as well as in PR and QTc intervals among women (all adjusted p<0.05). Findings were similar in a healthy subset of 1158 adults (age 61.2±9.1 years, 365 men) without cardiovascular risk factors. These first community-based ECG data in multi-ethnic older Asians highlight the independent effects of age, sex, body size and ethnicity on ECG parameters.

Notched QRS for the assessment of myocardial fibrosis in hypertrophic cardiomyopathy.

Patients with hypertrophic cardiomyopathy (HCM) sometimes develop myocardial fibrosis in association with adverse cardiovascular events. Electrocardiography (ECG) could provide helpful information on myocardial fibrosis in HCM, as in coronary artery disease. A total of 60 patients with HCM without bundle branch block underwent cardiac magnetic resonance imaging (CMR). The extent or location of late gadolinium enhancement (LGE) was examined in relation to 12-lead ECG. A notch on QRS was defined as at least 2 consecutive spikes in the same polarity with a reversal of direction ≥90° and the initial negative deflection ≥0.05 mV. LGE was associated with notched QRS, leftward QRS axis, and prolonged QRS duration, but not with any other findings such as abnormal Q waves, R-wave amplitude, or ST-T changes. Notched QRS was most useful in determining the presence or absence of myocardial fibrosis, with a sensitivity of 70% and a specificity of 81% using a cut-off of the number of leads with notched QRS ≥2. The number of notched QRS leads was positively correlated with LGE volume (P<0.01) and the lead distribution of notched QRS was informative about the location of LGE. A notch on QRS was useful in estimating myocardial fibrosis as assessed on CMR LGE in HCM patients without bundle branch block.

Quantitative electrocardiographic measures and long-term mortality in exercise test patients with clinically normal resting electrocardiograms

Currently, the only function of the resting electrocardiogram (ECG) in patients referred for exercise testing is to determine whether imaging is mandated. It is unknown if subtle ECG findings in those patients with clinically normal resting ECGs have prognostic significance. We performed a single-center cohort study of 18,964 patients without known cardiovascular disease who had a clinically normal resting ECG and who underwent treadmill exercise testing for evaluation of suspected coronary artery disease. Eleven quantitative ECG measures relating to heart rate, conduction, left ventricular mass, or repolarization were collected digitally. The primary outcome was all-cause mortality. The prognostic importance of a composite ECG score was assessed by measuring its impact on the c-index (analogous to area under receiver operating characteristic curve) and by measures of reclassification. During a median follow-up of 10.7 years, 1,585 patients died. The 4 most predictive digital ECG variables were higher ventricular rate, more leftward QRS axis, more downward ST-segment deviation, and longer QT interval. The ECG score was independently associated with mortality (75th vs 25th percentile hazard ratio 1.36, 95% confidence interval 1.25-1.49, P < .0001). The ECG score had modest impact on discrimination (change in c-index 0.04) and reclassification of risk (3.0% decrease of relative integrated discrimination improvement, P < .001). Subtle ECG findings relating to heart rate, conduction, left ventricular mass, or repolarization in patients with clinically normal ECGs referred for exercise testing may provide modest additional prognostic information over and above clinical and exercise measures.

Left bundle-branch block with right axis deviation—a unique aberrancy during supraventricular tachycardia

A tachycardia with left bundle-branch block morphology and right axis deviation points to the diagnosis of ventricular tachycardia. Conversely, any supraventricular tachycardia with left bundle-branch block is typically associated with a normal or leftward QRS axis. We present the case of a 34-year-old man showing atrioventricular nodal reentrant tachycardia with left bundle-branch block/right axis deviation as an exception to this rule.

Clinical Significance of Obstruction of the First Major Septal Branch

To the Editor: The first major septal branch of the left anterior descending coronary artery seems to be closely related to disorder of the conduction system. Blood supply to the anterosuperior fascicle of the left bundle branch originates exclusively from the septal branches.1 During myocardial ischemic attack due to stenosis of the proximal left anterior descending coronary artery, from the ostium of the left coronary artery to just before the first major septal branch, left-axis deviation often appears.2 3 4 Very recently, we reported5 that transient leftward QRS-axis shift during treadmill exercise testing or PTCA was a highly specific marker of proximal left anterior descending coronary artery disease. However, no one has confirmed that …

Accuracy of Exercise-Induced Left Axis QRS Deviation as a Specific Marker of Left Anterior Descending Coronary Artery Disease

In this prospective study, we examined the diagnostic accuracy of exercise-induced left QRS axis deviation as a marker of LAD coronary artery stenosis. The mean frontal QRS axis of 66 consecutive patients with chest pain and exercise-induced ST segment depression referred for diagnostic coronary angiography was analyzed and related to the angiographic findings. An exercise-induced leftward QRS axis deviation was found in 9/40 patients with and 0/26 patients without obstructive (≥70%) LAD disease (sensitivity 23%, specificity 100%, p = 0.025). In 7 of the 9 patients with left axis deviation, the lesion was proximal to and in 2 in the region of the first septal perforator. Inclusion of patients with 0° exercise-induced QRS axis deviation provided a more sensitive but less specific marker of LAD disease [sensitivity 53% (21/40), specificity 81% (21/26), p = 0.015]. The findings were similar in patients with single and with multivessel coronary artery disease. Grouping all patients in the present prospective and two previous retrospective studies (n = 165), the sensitivity was 29% and specificity 100% (p < 0.0001). Exercise-induced left QRS axis deviation was a highly specific marker of LAD coronary artery stenosis.

Transient Leftward QRS Axis Shift During Treadmill Exercise Testing or Percutaneous Transluminal Coronary Angioplasty Is a Highly Specific Marker of Proximal Left Anterior Descending Coronary Artery Disease

The efficacy of transient QRS axis shift to the left as a predictor of proximal left anterior descending coronary artery (LAD) disease was assessed. By using receiver operating characteristic curve analysis, we indicated that the difference in modal QRS axis between before and after exercise was useful in detecting proximal LAD disease.

Electrocardiogram and vectorcardiogram in ventricular inversion (corrected transposition)

The vectorcardiographic (VCG) and electrocardiographic (ECG) features in nine cases of ventricular inversion with two functioning ventricles (congenital corrected transposition of the great arteries) and associated cardiac malformations were correlated related with their hemodynamic states. All three cases with low venous ventricular pressure showed a similar VCG pattern with a posterior and completely counter-clockwise horizontal QRS loop. The ECG showed a leftward QRS axis, QS complexes in V 1, and RS complexes in V 6. These findings are normal for ventricular inversion without major associated defects. Three patients with isolated pressure or volume overload of the venous ventricle showed large leftward and posterior initial QRS forces, followed by a predominantly clockwise and rightward horizontal QRS loop. The ECG showed right axis deviation, qR complexes in V 1, and rS complexes in V 6. These findings are considered to represent venous ventricular hypertrophy. Three patients with hemodynamic situations which would be expected to result in biventricular overload demonstrated varying degrees of anterior displacement of the horizontal QRS loop, two with counter-clockwise inscription and one predominantly clockwise. The initial QRS forces, although leftward and superior as in the other groups, were anterior in each case. The ECG demonstrated normal or rightward QRS axis, no precordial q waves, and large biphasic RS complexes in the midprecordial leads. These findings are considered to represent biventricular hypertrophy. One patient had serial tracings which revealed progressive ECG-VCG changes due to increasing venous ventricular hypertension secondary to increasing pulmonic stenosis. These findings indicate that the ECG-VCG accurately reflect the anatomy and hemodynamics in ventricular inversion.