Liliane Wecke

Vectorcardiographic QRS area as a novel predictor of response to cardiac resynchronization therapy

BACKGROUND QRS duration and left bundle branch block (LBBB) morphology are used to select patients for cardiac resynchronization therapy (CRT). We investigated whether the area of the QRS complex (QRSAREA) on the 3-dimensional vectorcardiogram (VCG) can improve patient selection. METHODS VCG (Frank orthogonal lead system) was recorded prior to CRT device implantation in 81 consecutive patients. VCG parameters, including QRSAREA, were assessed, and compared to QRS duration and morphology. Three LBBB definitions were used, differing in requirement of mid-QRS notching. Responders to CRT (CRT-R) were defined as patients with ≥15% reduction in left ventricular end systolic volume after 6months of CRT. RESULTS Fifty-seven patients (70%) were CRT-R. QRSAREA was larger in CRT-R than in CRT non-responders (140±42 vs 100±40 μVs, p<0.001) and predicted CRT response better than QRS duration (AUC 0.78 vs 0.62, p=0.030). With a 98μVs cutoff value, QRSAREA identified CRT-R with an odds ratio (OR) of 10.2 and a 95% confidence interval (CI) of 3.4 to 31.1. This OR was higher than that for QRS duration >156ms (OR=2.5; 95% CI 0.9 to 6.6), conventional LBBB classification (OR=5.5; 95% CI 0.9 to 32.4) or LBBB classification according to American guidelines (OR=4.5; 95% CI 1.6 to 12.6) or Strauss (OR=10.0; 95% CI 3.2 to 31.1). CONCLUSION QRSAREA is an objective electrophysiological predictor of CRT response that performs at least as good as the most refined definition of LBBB. CONDENSED ABSTRACT In 81 candidates for cardiac resynchronization therapy (CRT) we measured the area of the QRS complex (QRSAREA) using 3-dimensional vectorcardiography. QRSAREA was larger in echocardiographic responders than in non-responders and predicted CRT response better than QRS duration and than simple LBBB criteria. QRSAREA is a promising electrophysiological predictor of CRT response.

The value of the 12-lead ECG for evaluation and optimization of cardiac resynchronization therapy in daily clinical practice

Based on existing literature and some new data we propose a simple three-step strategy using the standard 12-lead ECG for patient selection and optimal delivery of cardiac resynchronization therapy (CRT). (1) Complete LBBB with regard to the indication for CRT can probably best be identified by a QRS duration of ≥ 130 ms for women and ≥ 120 ms for men with the presence of mid-QRS notch-/slurring in ≥ 2 contiguous leads of V1, V2, V5, V6, I and aVL. (2) Left ventricular (LV) free wall pacing should result in a positive QRS complex in lead V1, with estimation of the exact LV lead position in the circumferential and apico-basal direction using lead aVF and the precordial leads, respectively. Wide and fractionated LV-paced QRS complexes may indicate pacing in scar tissue. (3) Atrioventricular and interventricular stimulation intervals may be optimized by adjusting them until precordial leads show fusion patterns between left and right ventricular activation wavefronts in the QRS complex.

Repolarization changes in patients with heart failure receiving cardiac resynchronization therapy—signs of cardiac memory

BACKGROUND AND PURPOSE Cardiac memory is known as T-wave inversions and other repolarization changes after a period of altered ventricular activation, previously mainly studied in structurally normal hearts. We investigated repolarization changes in failing hearts undergoing cardiac resynchronization therapy (CRT). METHODS Electrocardiogram and vectorcardiogram were recorded before and 1 day and 2 weeks after initiation of CRT in 23 patients with heart failure and left bundle-branch block. RESULTS After 1 day of CRT, the T vector during intrinsic conduction (left bundle-branch block) had rotated toward the direction of the paced QRS vector; T-vector size had increased with further increase after 2 weeks (T-vector amplitude, 889 ± 277 vs 651 ± 225 μV; T area, 169 ± 70 vs 102 ± 39 μVs; P < .01) accompanied by prolonged repolarization (T peak-to-end, 174 ± 34 vs 127 ± 16; QT interval corrected for heart rate, 541 ± 59 vs 493 ± 33 milliseconds; P < .01). CONCLUSIONS Repolarization changes are present in patients with heart failure, although less pronounced compared with after right ventricular pacing in structurally normal hearts.

Vectorcardiography as a Tool for Easy Optimization of Cardiac Resynchronization Therapy in Canine LBBB Hearts

Background—In cardiac resynchronization therapy (CRT), optimization of left ventricular (LV) stimulation timing is often time consuming. We hypothesized that the QRS vector in the vectorcardiogram (VCG) reflects electric interventricular dyssynchrony, and that the QRS vector amplitude (VAQRS), halfway between that during left bundle branch block (LBBB) and LV pacing, reflects optimal resynchronization, and can be used for easy optimization of CRT. Methods and Results—In 24 canine hearts with LBBB (12 acute, 6 with heart failure, and 6 with myocardial infarction), the LV was paced over a wide range of atrioventricular (AV) delays. Surface ECGs were recorded from the limb leads, and VAQRS was calculated in the frontal plane. Mechanical interventricular dyssynchrony (MIVD) was determined as the time delay between upslopes of LV and right ventricular pressure curves, and systolic function was assessed as LV dP/dtmax. VAQRS and MIVD were highly correlated (r=0.94). The VAQRS halfway between that during LV pacing with short AV delay and intrinsic LBBB activation accurately predicted the optimal AV delay for LV pacing (1 ms; 95% CI, –5 to 8ms). Increase in LV dP/dtmax at the VCG predicted AV delay was only slightly lower than the highest observed [INCREMENT]LV dP/dtmax (–2.7%; 95% CI, –3.6 to –1.8%). Inability to reach the halfway value of VAQRS during simultaneous biventricular pacing (53% of cases) was associated with suboptimal hemodynamic response, which could be corrected by sequential pacing. Conclusions—The VAQRS reflects electric interventricular dyssynchrony and accurately predicts optimal timing of LV stimulation in canine LBBB hearts. Therefore, VCG may be useful as a reliable and easy tool for individual optimization of CRT.

Vectorcardiography shows cardiac memory and repolarization heterogeneity after ablation of accessory pathways not apparent on ECG

BACKGROUND Pacing induced cardiac memory is an established phenomenon, but following successful WPW ablation, cardiac memory was present on ECG in variable proportions of patients depending on accessory pathway (AP) location. We hypothesized that vectorcardiography (VCG), which is more sensitive than ECG, would show cardiac memory after WPW ablation independent of AP location. METHODS Thirty-six patients were followed after successful AP ablation, 11 with overt posteroseptal (PS), 13 with overt left-sided (LS) and 12 with concealed APs (controls). VCGs were recorded the day before and after the procedure, ≥ once/week for 6-8 weeks and after ≥ 3 months. T vector and T-vector loop parameters were analyzed and compared. RESULTS After ablation of overt APs, there was a correlation between the directions of the preexcited maximum QRS-vector and the post-ablation maximum T-vector, confirming the presence of cardiac memory. Ablation of overt APs was followed by cardiac memory apparent in different directions. Thus, ablation of PS APs was followed by most pronounced changes in T-vector elevation and LS APs with significant changes only in T-vector azimuth. Cardiac memory disappeared within a month in > 80% of cases. Furthermore, T-vector loop morphology changes suggested a period of repolarization heterogeneity immediately after ablation of overt APs. CONCLUSIONS According to VCG analysis cardiac memory was present after ablation of overt APs independent of location as consistently as after ventricular pacing, and disappeared within a similar time frame during normal ventricular activation. In addition, signs of transient repolarization heterogeneity were observed after ablation of overt APs.

The synthesized vectorcardiogram resembles the measured vectorcardiogram in patients with dyssynchronous heart failure

BACKGROUND The use of vectorcardiography (VCG) has regained interest, however, original Frank-VCG equipment is rare. This study compares the measured VCGs with those synthesized from the 12-lead electrocardiogram (ECG) in patients with heart failure and conduction abnormalities, who are candidate for cardiac resynchronization therapy (CRT). METHODS In 92 CRT candidates, Frank-VCG and 12-lead ECG were recorded before CRT implantation. The ECG was converted to a VCG using the Kors method (Kors-VCG) and the two methods were compared using correlation and Bland-Altman analyses. RESULTS Variables calculated from the Frank- and Kors-VCG showed correlation coefficients between 0.77 and 0.90. There was a significant but small underestimation by the Kors-VCG method, relative bias ranging from -1.9% ± 4.6% (QRS-T angle) to -9.4% ± 20.8% (T area). CONCLUSION The present study shows that it is justified to use Kors-VCG calculations for VCG analysis, which enables retrospective VCG analysis of previously recorded ECGs in studies related to CRT.

Pacing-induced electrophysiological remodeling in hypertrophic obstructive cardiomyopathy--observations on cardiac memory.

Background: Hypertrophic cardiomyopathy carries an increased risk for sudden cardiac death. While pacing therapy reduces the left ventricular outflow tract gradient and improves symptoms in a subgroup of hypertrophic obstructive cardiomyopathy (HOCM) patients, its electrophysiological consequences are unknown and were therefore assessed in this prospective study.

Maximal Aerobic Power versus Performance in Two Aerobic Endurance Tests among Young and Old Adults

Background: Aerobic fitness is of great value for reducing risk of mortality and cardiovascular diseases. Objective: This study evaluated the performance in and correlations between a new test (five-minute pyramid test, 5MPT), the six-minute walk-test (6MWT) and maximal oxygen uptake (VO2max) among old and young adults. Methods: Forty-four habitually active adults (females and males), 23 old (64–79 years) and 21 young (20–32 years) participated. In the 5MPT, the participants moved back and forth along a short walkway (5.5 m) over boxes (height: ‘old people’ 0.42 m, ‘young people’ 0.62 m) arranged like an elongated step pyramid for 5 min. Power in the pyramid test (5MPTpower) was calculated as the product of numbers of laps, body weight, gravity and highest box level divided by time. A 6MWT and a maximal cycle ergometer test for direct measurements of VO2max were also performed. In all tests heart rate, with on-line electrocardiography, and perceived exertion were recorded. Results: There was a strong correlation between the 5MPTpower and VO2max for the entire group studied (r = 0.98), and each of the four subgroups old and young females and males separately (r = 0.78–0.98). Contrary to several earlier studies, especially involving people with various diseases, the present data showed that 6MWT cannot be used to predict VO2max among old females and young adults. The correlation with VO2max was weaker for the 6MWT than for the 5MPTpower. The relative performance values for the old compared to the young (ratio old/young × 100) were considerably lower in 5MPTpower and VO2max (47–55%) than in distance and ‘work’ in the 6MWT (82–86%). Conclusions: The results, with age and gender variations, can be valuable information in health-fitness contexts, since measuring physical aerobic capacity is very significant in connection with risk evaluations of mortality and various diseases. The 5MPT is a rapid, functional, easy and inexpensive tool for predicting assessed maximal aerobic power.

Early Repolarization in Middle-Age Runners: Cardiovascular Characteristics.

PURPOSE This study aimed to assess the prevalence and patterns of early repolarization (ER) in middle-age long-distance runners, its relation to cardiac structure and function, and its response to strenuous physical activity. METHODS Male first-time cross-country race participants >45 yr were assessed pre- and postrace by medical history and physical examination, 12-lead ECG, vectorcardiography, blood tests, and echocardiography. ER was defined either as ST elevation or J wave and categorized according to localization and morphology. RESULTS One hundred and fifty-one subjects (50 ± 5 yr) were evaluated before the race, and 47 subjects were evaluated after the race. Altogether, 67 subjects (44%) had ER. Subjects with versus without ER had a lower resting HR (56 ± 8 vs 69 ± 9 bpm, P = 0.02), lower body mass index (24 ± 2 vs 25 ± 3 kg·m(-2), P < 0.001), higher training volume (3.0 ± 2.6 vs 2.1 ± 2.7 h·wk(-1), P = 0.03), and faster 30-km running times (194 ± 28 vs 208 ± 31 min, P = 0.01). Vectorcardiography parameters in subjects with ER showed more repolarization heterogeneity: vector gradient (QRS-T(area)) (120 ± 25 vs 92 ± 29 μVs, P < 0.001), T(area) (105 ± 18 vs 73 ± 23 μVs, P < 0.001), and T(amplitude) (0.63 ± 0.13 vs 0.53 ± 0.16 mm, P < 0.001); these parameters were inversely related to HR (r = -0.37 to -0.48, P < 0.001). ER disappeared in 15 (75%) of 20 subjects after the race. CONCLUSIONS ER is a common finding in middle-age male runners. This ECG pattern, regardless of morphology and localization, is associated with normal cardiac examinations including noninvasive electrophysiology, features of better physical conditioning, and disappears after strenuous exercise in most cases. These findings support that ER should be regarded as a common and training-related finding also in middle-age physically active men.

Contents Vol. 57, 2011

Behavioural Science Section K.J. Anstey, Canberra L. Clare, Bangor D. Gerstorf, Berlin J.D. Henry, Sydney T. Hess, Raleigh, N.C. S.M. Hofer, Victoria I. Kryspin Exner, Wien D.C. Park, Dallas, Tex. K. Ritchie, Montpellier J. Smith, Ann Arbor, Mich. Experimental Section C. Bertoni-Freddari, Ancona R. Faragher, Brighton C. Franceschi, Bologna T. Fülöp, Sherbrooke L. Gavrilov, Chicago, Ill. L. Haynes, Saranac Lake, N.Y. K. Hirokawa, Tokyo G.J. Lithgow, Novato, Calif. M. Rose, Irvine, Calif. A. Viidik, Wien J. Vijg, Bronx, N.Y.