Available online at www.sciencedirect.com
ScienceDirect Journal of Electrocardiology 48 (2015) 141 – 144 www.jecgonline.com
Vectorcardiographic predictors of ventricular arrhythmia inducibility in patients with tetralogy of Fallot Daniel Cortez, MD, a, b,⁎ Emily Ruckdeschel, MD, a, b Anthony C. McCanta, MD, a, b Kathryn Collins, MD, a, b William Sauer, MD, b Joseph Kay, MD, a, b Duy Nguyen, MD b a
Children’s Hospital of Colorado, Aurora, USA b University of Colorado, Aurora, USA
Abstract
Introduction: Vectorcardiography (VCG) may have predictive value in Tetralogy of Fallot (TOF) patients undergoing ventricular arrhythmia inducibility (VAI) electrophysiology studies (EPs). Materials and methods: Blinded, retrospective analyses of 37 adult TOF patients undergoing EPs prior to pulmonary valve replacements were performed (21 female, median age 37 years). VAI was evaluated from EPs and resting 12-lead electrocardiograms, respectively using QRS and heart rate adjusted Q-T intervals, spatial QRS-T angles (peaks), T-wave and QRS-wave (QRSwave vc) component vector root mean squares. Differences were assessed (Student t-tests, Mann Whitney U-tests, Analysis of Variance). Relative risks were calculated. Results: 16 patients had VAI (6 monomorphic, 10 polymorphic). Only the QRSwave vc showed significant differences between those with and without VAI, 10.5 ± 2.4 dmV vs. 13.9 ± 4.5 dmV, respectively (p = 0.002), area under the ROC curve of 0.78 and relative risk of 2.52. Conclusion: VCG evidence of depolarization differences was significant between TOF patients with and without inducible VA. © 2015 Elsevier Inc. All rights reserved.
Keywords:
Vectorcardiography; Tetralogy of Fallot; Ventricular tachycardia
Introduction
Materials and methods
Tetralogy of Fallot (TOF) patients have significant arrhythmia burden post-operatively, reported to be as high as 43.3% [1]. Programmed ventricular stimulation in TOF patients has been shown to have diagnostic and prognostic value in risk stratisfying TOF patients [2]. Vectorcardiographic (VCG) principles provide additional clinical information to the 12-lead electrocardiogram (ECG) and have provided further diagnostic [3,4] and prognostic [5–9] uses of the ECG in the traditional 12lead set-up. We hypothesize that some of these parameters and their vector components may have predictive value in Tetralogy of Fallot (TOF) patients undergoing electrophysiology studies (EPs) for ventricular arrhythmia inducibility (VAI). Secondary aims include evaluation of the utility of the QRS wave vector component (QRSwave vc) versus QRS duration in predicting gadolinium enhancement versus large right ventricular (RV) volume in this TOF cohort.
A blinded retrospective analysis of 37 adult TOF patients undergoing EP studies prior to pulmonary valve replacements (PVR) was performed (21 female patients, median age 37 years). VA inducibility and vectorcardiography were evaluated from electrophysiology studies and resting 12-lead electrocardiograms, respectively using right ventricular (RV) inducibility studies as described by Khairy et al. [2]. Specifically, measurements of Q-T interval adjusted for heart rate (QTc), QRS duration (QRSd), spatial peaks QRS-T angles (SPQRS-T angle), principal T wave and principal QRS-wave component vectors (Twave vc and QRSwave vc) (root mean square of the T-wave and QRS-wave vector components, respectively) were used to compare those with inducible VA versus those without inducible VA. QRSwave vc, Twave vc and SPQRS-T angles were calculated by the visual estimation method (utilizing the regression-related analysis of Kors et al.) as described by our group [10]. EVGs were taken on the same day prior to the EPS. Fig. 1 demonstrates the vectorcardiographic components of a patient with and a patient without VA inducibility while Fig. 2 gives an example of how to calculate
⁎ Corresponding author at: 13123 East 16th Avenue, Box 100 Aurora, CO 80045. E-mail address: [email protected] http://dx.doi.org/10.1016/j.jelectrocard.2014.11.009 0022-0736/© 2015 Elsevier Inc. All rights reserved.
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Fig. 1. Example of parameters used in TOF patients with and without ventricular inducibility.
the QRSwave vc. Student t, Mann–Whitney U and Fisher exact tests were used as appropriate in comparing those with and those without ventricular inducibility and when comparing MRI findings to inducibility. Analysis of Variance was also used to assess differences between those with and without sustained inducible VA and between the three groups, respectively (non-inducible versus monomorphic versus polymorphic VA patients). An area under the receiver operating characteristic (ROC) curve and relative risk (RR) were calculated for inducible VA.
Results Of the 37 patients analyzed, 16 had inducible VA (N 5 beat ventricular tachycardia) with 6 having monomorphic VA and 10 having polymorphic VA. 21 patients were not inducible. Only the QRSwave vc showed significant
differences between those with and those without VA inducibility, 10.5 ± 2.4 dmV vs. 13.9 ± 4.5 mV respectively (p = 0.002). Table 1 depicts all other parameters tested with associated p-values. The principle QRSwave vc had sensitivity and specificity of 100% and 62% respectively with an area under the ROC curve of 0.78 and relative risk (RR) of 2.52 (95% CI 1.48 to 4.29) at a cut-off based on the best value derived from the area under the ROC curve (13.2 mV) as noted in Table 2. No other parameters showed significant differences between those inducible and those not inducible. No clarification was needed. No inter-group variability existed between those with inducible monomorphic VT, as compared to those with inducible polymorphous VT. Patient history of ventricular tachycardia via Holter monitor or emergency room documentation was also compared utilizing the same parameters (although only 3 patients had history of documented sustained VT). Only the QRS wave vc showed significant differences (p-value = 0.050) with an AUROC of
Fig. 2. Example calculation of QRS wave vector component (QRS wave vc).
D. Cortez et al. / Journal of Electrocardiology 48 (2015) 141–144 Table 1 Parameters used for prediction of pre-operative ventricular arrhythmia inducibility (VAI). QTc (ms)
QRSd (ms)
SPQRS-T angle (°)
QRSwave Twave vc (dmV) vc (dmV)
VAI 479.7 ± 38.4 153.2 ± 30.7 98.6 ± 39.4 10.5 ± 2.4 4.4 ± 1.7 (n = 16) No VAI 489.6 ± 38.5 166.5 ± 33.4 97.7 ± 47.5 13.9 ± 4.5 5.2 ± 2.2 (n = 21) p-value 0.624 0.322 0.891 0.002 0.336
0.75 (95% CI 0.60 to 0.90) and sensitivity, specificity and RR of 1.00, 0.67 and 2.59 (95% CI 1.48 to 4.71). When assessed for gadolinium enhancement the QRSd was the only parameter that showed statistical significance between those with versus those without enhancement at 166.9 ± 30.0 ms and 142.0 ± 5.7 ms (p 0.03), respectively as noted in Table 3. The QRSd was also the only parameter that seemed to predict those with right ventricular volumes N 180 ml by MRI with values of 140.7 ± 4.6 ms and 168.1 ± 31.1 ms, respectively for those without versus those with RV volume N 180 ml (Table 4). No significant differences existed however regarding the ability of the increased RV volume versus gadolinium enhancement to predict inducibility. An attempt at separating the patients based on hemodynamic properties yielded no significant differences between those with atrial septal defects (ASDs) versus those with repaired atrial level shunts, and between those with or without ASDs and right ventricular end diastolic pressures (RVEDP) N 10 mmHg and those with RVEDP b 10 mmHg (Table 5). No significant differences existed between those TOF patients with right ventricular systolic pressures (RVsp) greater than one half of the left ventricular systolic pressures (LVsp) versus those with less than half systemic RVsp. Discussion These findings show that the root mean square of the depolarization vector components is more predictive of inducibility than any other parameter tested in our cohort. It also shows that the same holds true and with very similar AUROC and RR as the inducibility results. Surprisingly the QRSd and QTc were not predictive of inducible arrhythmogenicity as suggested by studies including a recent literature review by Bassareo and Mercuro [11]. This study also suggests Table 2 QRS wave vector component (QRSwave vc) sensitivity, specificity values, area under the receiver operating characteristic curve (area under ROC curve) and relative risk with 95% confidence intervals (95% CI) for prediction of ventricular inducibility at cutoff of 13.2 dmV and history of ventricular arrhythmias at a cutoff of 11.2 dmV for the QRS wave vector component.
Sensitivity Specificity AUROC (95% CI) Relative Risk
Ventricular inducibility
Ventricular arrhythmias
1.00 0.62 0.78 (0.65 to 0.90) 2.52 (1.48 to 4.29)
1.00 0.67 0.75 (0.60 to 0.90) 2.59 (1.48 to 4.71)
143
Table 3 Gadolinium enhancement versus no enhancement for all tested parameters.
Inducible (%) QRSd (ms) QTc (ms) Spatial QRS-T °(deg) QRSwave vc (dmV) Twave vc (dmV)
+Gadolinium RV (N = 13)
No Gadolinium (N = 2)
p-value
6 (46.2) 166.9 ± 30.0 491.5 ± 32.6 101.3 ± 39.1 13.3 ± 5.1 5.7 ± 2.1
1 (50.0) 142.0 ± 5.7 485.0 ± 17.0 123.6 ± 41.7 10.1 ± 5.9 5.9 ± 0.0
0.92 0.025 0.704 0.584 0.573 0.733
that TOF patients with increased QRSd should undergo electrophysiology studies to assess arrhythmogenicity. And since this has already proven to be predictive of ventricular tachycardia risk [2], one might confer that our small study suggests that the QRSwave vc should be assessed before EP study is performed regardless of QRSd given the inducible average was far less than 180 ms as suggested to be predictive of arrhythmogenicity [11]. Furthermore, since increased ventricular stretch and mass to volume ratio may increase arrhythmogenicity as suggested by the above author as well as by Menon et al. [12] and Velente et al. [13], respectively, one could rationalize that with this increased stretch and RVH mass, there would also be differences in depolarization subcomponent vector orientation. This could cause an overall sum magnitude to be smaller than that with less right ventricular stretch as the increased components in the thickened walls could disperse the magnitude of the overall vector. This fits our cohort as they are all undergoing PVR and thus have RV pressure and volume overload. Also, the association between ventricular arrhythmia inducibility and the root mean square of the QRSwave has been demonstrated in the past by el-Sherif et al. [14] as well as others as part of a signal averaged ECG analysis, thus it is not surprising that derived QRSwave vc is also predictive. Furthermore this study shows that the risk of ventricular tachycardia inducibility is not just based on RV volume N 180 ms or on just scar formation as neither showed a significant relationship to inducibility. Furthermore our results give many patients with QRSd b 180 ms for those with RV volume N 180 ml. Interestingly, hemodynamic measurements of right ventricular systolic or diastolic pressure were not consistent with inducibility or history of actual arrhythmias, and our tested parameters did not show any significant relationship to these parameters either. Arrhythmia inducibility is more complex than any one aspect MRI or catheter-derived it seems. Table 4 MRI measured RV volume b180 ml versus RV volume N 180 ml for all tested parameters.
Inducible (%) QRSd (ms) QTc (ms) Spatial QRS-T °(deg) QRSwave vc (dmV) Twave vc (dmV)
RV volume b 180 ml (N = 3)
RV volume N 180 ml (N = 14)
p-value
2 (66.7) 140.7 ± 4.6 496.7 ± 23.5 117.4 ± 31.4 9.4 ± 4.3 4.9 ± 1.7
5 (35.7) 168.1 ± 31.1 491.9 ± 32.8 93.5 ± 42.4 14.1 ± 5.0 5.2 ± 2.2
0.321 0.007 0.781 0.330 0.186 0.808
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Table 5 Hemodynamic data, right ventricular end diastolic pressure ≥ 10 mmHg versus those with RVEDp b 10 mmHg.
Inducible (%) QRSd (ms) QTc (ms) Spatial QRS-T (°) QRSwave vc (dmV) Twave vc (dmV)
RVEDp N 10 mmHg (N = 10)
RVEDp=/b10 (N = 13)
p-value
3 (30.0) 173.0 ± 22.1 501.4 ± 38.4 91.8 ± 31.5 11.6 ± 3.6 4.7 ± 1.6
5 (35.7) 162.3 ± 28.1 485.6 ± 21.1 102.8 ± 44.4 14.3 ± 5.4 5.8 ± 1.9
1.000 0.319 0.263 0.496 0.162 0.408
Of course limitations of this study include mainly the small size of the study. Also, since this was a retrospective study and signal averaged ECGs were not assessed, we were unable to include those values in our risk stratification as have been suggested to be associated with arrhythmogenicity [11].
Conclusions In this retrospective analysis of TOF patients undergoing EP studies, VCG evidence of depolarization differences was present between those TOF patients with and without inducible VA in the pre- and post-operative medicine, while the QRS duration as well as all other parameters tested did not. This suggests that VCG, especially the QRSwave vc, may have a role in risk stratification for arrhythmias in TOF patients but not necessarily in RV volume or in scar formation. Larger, prospective studies are needed to validate this method. Acknowledgements No acknowledgements other than the authors cited above. There are no financial disclosures or conflicts of interest. References [1] Khairy P, Aboulhosn J, Gurvitz M, et al. Arrhythmia burden in adults with surgically repaired tetralogy of Fallot. Circulation 2010;122:868–75.
[2] Khairy P, Landzberg M, Gatzoulis M, et al. Value of programmed ventricular stimulation after tetralogy of Fallot repair. Circulation 2004;109:1994–2000. [3] Triola B, Olson MB, Reis SE, et al. Electrocardiographic predictors of cardiovascular outcome in women: the National Heart, Lung, and Blood Institute-sponsored Women's Ischemia Syndrome Evaluation (WISE) study. J Am Coll Cardiol 2005;46:51–6. [4] Voulgari C, Tentolouris N, Moyssakis I, et al. Spatial QRS-T angle: association with diabetes and left ventricular performance. Eur J Clin Investig 2006;36:608–13. [5] Borleffs CJ, Scherptong RW, Man SC, et al. Predicting ventricular arrhythmias in patients with ischemic heart disease: clinical application of the ECG-derived QRS-T angle. Circ Arrhythm Electrophysiol 2009;2:548–54. [6] de Torbal A, Kors JA, van Herpen G, et al. The electrical T-axis and the spatial QRS-T angle are independent predictors of long-term mortality in patients admitted with acute ischemic chest pain. Cardiology 2004;101:199–207. [7] Kardys I, Kors JA, van der Meer IM, Hofman A, van der Kuip DA, Witteman JC. Spatial QRS-T angle predicts cardiac death in a general population. Eur Heart J 2003;24:1357–64. [8] Rautaharju PM, Ge S, Nelson JC, et al. Comparison of mortality risk for electrocardiographic abnormalities in men and women with and without coronary heart disease (from the Cardiovascular Health Study). Am J Cardiol 2006;97:309–15. [9] Yamazaki T, Froelicher VF, Myers J, Chun S, Wang P. Spatial QRS-T angle predicts cardiac death in a clinical population. Heart Rhythm 2005;2:73–8. [10] Cortez D, Sharma N, Devers C, Devers E, Schlegel TT. Visual transform applications for estimating the spatial QRS-T angle from the conventional 12-lead ECG: Kors is still most frank. J Electrocardiol 2014;47:12–9. [11] Bassareo PP, Mercuro G. QRS complex enlargement as a predictor of ventricular arrhythmia in tetralogy of Fallot: a comprehensive literature review and historical review. Int Sch Res Not Cardiol 2013;2013:1–8 [7825 08]. [12] Menon SC, Kaza AK, Puchalski MD. Effect of ventricular size and function on exercise performance and the electrocardiogram in repaired tetralogy of Fallot with pure pulmonary regurgitation. Ann Pediatr Cardiol 2012;5:151–5. [13] Velente AM, Gauvreau K, Assenza GE, et al. Contemporary predictors of death and sustained ventricular tachycardia in patients with repaired tetralogy of Fallot enrolled in the INDICATOR cohort. Heart 2014;100:247–53. [14] el-Sherif N, Turitto G, Fontaine JM. Risk stratification of patients with complex arrhythmias. Value of ambulatory electrocardiographic recording, programmed electrical stimulation and the signal-averaged electrocardiogram. Am J Cardiol 1978;42:602–12.
ScienceDirect Journal of Electrocardiology 48 (2015) 141 – 144 www.jecgonline.com
Vectorcardiographic predictors of ventricular arrhythmia inducibility in patients with tetralogy of Fallot Daniel Cortez, MD, a, b,⁎ Emily Ruckdeschel, MD, a, b Anthony C. McCanta, MD, a, b Kathryn Collins, MD, a, b William Sauer, MD, b Joseph Kay, MD, a, b Duy Nguyen, MD b a
Children’s Hospital of Colorado, Aurora, USA b University of Colorado, Aurora, USA
Abstract
Introduction: Vectorcardiography (VCG) may have predictive value in Tetralogy of Fallot (TOF) patients undergoing ventricular arrhythmia inducibility (VAI) electrophysiology studies (EPs). Materials and methods: Blinded, retrospective analyses of 37 adult TOF patients undergoing EPs prior to pulmonary valve replacements were performed (21 female, median age 37 years). VAI was evaluated from EPs and resting 12-lead electrocardiograms, respectively using QRS and heart rate adjusted Q-T intervals, spatial QRS-T angles (peaks), T-wave and QRS-wave (QRSwave vc) component vector root mean squares. Differences were assessed (Student t-tests, Mann Whitney U-tests, Analysis of Variance). Relative risks were calculated. Results: 16 patients had VAI (6 monomorphic, 10 polymorphic). Only the QRSwave vc showed significant differences between those with and without VAI, 10.5 ± 2.4 dmV vs. 13.9 ± 4.5 dmV, respectively (p = 0.002), area under the ROC curve of 0.78 and relative risk of 2.52. Conclusion: VCG evidence of depolarization differences was significant between TOF patients with and without inducible VA. © 2015 Elsevier Inc. All rights reserved.
Keywords:
Vectorcardiography; Tetralogy of Fallot; Ventricular tachycardia
Introduction
Materials and methods
Tetralogy of Fallot (TOF) patients have significant arrhythmia burden post-operatively, reported to be as high as 43.3% [1]. Programmed ventricular stimulation in TOF patients has been shown to have diagnostic and prognostic value in risk stratisfying TOF patients [2]. Vectorcardiographic (VCG) principles provide additional clinical information to the 12-lead electrocardiogram (ECG) and have provided further diagnostic [3,4] and prognostic [5–9] uses of the ECG in the traditional 12lead set-up. We hypothesize that some of these parameters and their vector components may have predictive value in Tetralogy of Fallot (TOF) patients undergoing electrophysiology studies (EPs) for ventricular arrhythmia inducibility (VAI). Secondary aims include evaluation of the utility of the QRS wave vector component (QRSwave vc) versus QRS duration in predicting gadolinium enhancement versus large right ventricular (RV) volume in this TOF cohort.
A blinded retrospective analysis of 37 adult TOF patients undergoing EP studies prior to pulmonary valve replacements (PVR) was performed (21 female patients, median age 37 years). VA inducibility and vectorcardiography were evaluated from electrophysiology studies and resting 12-lead electrocardiograms, respectively using right ventricular (RV) inducibility studies as described by Khairy et al. [2]. Specifically, measurements of Q-T interval adjusted for heart rate (QTc), QRS duration (QRSd), spatial peaks QRS-T angles (SPQRS-T angle), principal T wave and principal QRS-wave component vectors (Twave vc and QRSwave vc) (root mean square of the T-wave and QRS-wave vector components, respectively) were used to compare those with inducible VA versus those without inducible VA. QRSwave vc, Twave vc and SPQRS-T angles were calculated by the visual estimation method (utilizing the regression-related analysis of Kors et al.) as described by our group [10]. EVGs were taken on the same day prior to the EPS. Fig. 1 demonstrates the vectorcardiographic components of a patient with and a patient without VA inducibility while Fig. 2 gives an example of how to calculate
⁎ Corresponding author at: 13123 East 16th Avenue, Box 100 Aurora, CO 80045. E-mail address: [email protected] http://dx.doi.org/10.1016/j.jelectrocard.2014.11.009 0022-0736/© 2015 Elsevier Inc. All rights reserved.
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Fig. 1. Example of parameters used in TOF patients with and without ventricular inducibility.
the QRSwave vc. Student t, Mann–Whitney U and Fisher exact tests were used as appropriate in comparing those with and those without ventricular inducibility and when comparing MRI findings to inducibility. Analysis of Variance was also used to assess differences between those with and without sustained inducible VA and between the three groups, respectively (non-inducible versus monomorphic versus polymorphic VA patients). An area under the receiver operating characteristic (ROC) curve and relative risk (RR) were calculated for inducible VA.
Results Of the 37 patients analyzed, 16 had inducible VA (N 5 beat ventricular tachycardia) with 6 having monomorphic VA and 10 having polymorphic VA. 21 patients were not inducible. Only the QRSwave vc showed significant
differences between those with and those without VA inducibility, 10.5 ± 2.4 dmV vs. 13.9 ± 4.5 mV respectively (p = 0.002). Table 1 depicts all other parameters tested with associated p-values. The principle QRSwave vc had sensitivity and specificity of 100% and 62% respectively with an area under the ROC curve of 0.78 and relative risk (RR) of 2.52 (95% CI 1.48 to 4.29) at a cut-off based on the best value derived from the area under the ROC curve (13.2 mV) as noted in Table 2. No other parameters showed significant differences between those inducible and those not inducible. No clarification was needed. No inter-group variability existed between those with inducible monomorphic VT, as compared to those with inducible polymorphous VT. Patient history of ventricular tachycardia via Holter monitor or emergency room documentation was also compared utilizing the same parameters (although only 3 patients had history of documented sustained VT). Only the QRS wave vc showed significant differences (p-value = 0.050) with an AUROC of
Fig. 2. Example calculation of QRS wave vector component (QRS wave vc).
D. Cortez et al. / Journal of Electrocardiology 48 (2015) 141–144 Table 1 Parameters used for prediction of pre-operative ventricular arrhythmia inducibility (VAI). QTc (ms)
QRSd (ms)
SPQRS-T angle (°)
QRSwave Twave vc (dmV) vc (dmV)
VAI 479.7 ± 38.4 153.2 ± 30.7 98.6 ± 39.4 10.5 ± 2.4 4.4 ± 1.7 (n = 16) No VAI 489.6 ± 38.5 166.5 ± 33.4 97.7 ± 47.5 13.9 ± 4.5 5.2 ± 2.2 (n = 21) p-value 0.624 0.322 0.891 0.002 0.336
0.75 (95% CI 0.60 to 0.90) and sensitivity, specificity and RR of 1.00, 0.67 and 2.59 (95% CI 1.48 to 4.71). When assessed for gadolinium enhancement the QRSd was the only parameter that showed statistical significance between those with versus those without enhancement at 166.9 ± 30.0 ms and 142.0 ± 5.7 ms (p 0.03), respectively as noted in Table 3. The QRSd was also the only parameter that seemed to predict those with right ventricular volumes N 180 ml by MRI with values of 140.7 ± 4.6 ms and 168.1 ± 31.1 ms, respectively for those without versus those with RV volume N 180 ml (Table 4). No significant differences existed however regarding the ability of the increased RV volume versus gadolinium enhancement to predict inducibility. An attempt at separating the patients based on hemodynamic properties yielded no significant differences between those with atrial septal defects (ASDs) versus those with repaired atrial level shunts, and between those with or without ASDs and right ventricular end diastolic pressures (RVEDP) N 10 mmHg and those with RVEDP b 10 mmHg (Table 5). No significant differences existed between those TOF patients with right ventricular systolic pressures (RVsp) greater than one half of the left ventricular systolic pressures (LVsp) versus those with less than half systemic RVsp. Discussion These findings show that the root mean square of the depolarization vector components is more predictive of inducibility than any other parameter tested in our cohort. It also shows that the same holds true and with very similar AUROC and RR as the inducibility results. Surprisingly the QRSd and QTc were not predictive of inducible arrhythmogenicity as suggested by studies including a recent literature review by Bassareo and Mercuro [11]. This study also suggests Table 2 QRS wave vector component (QRSwave vc) sensitivity, specificity values, area under the receiver operating characteristic curve (area under ROC curve) and relative risk with 95% confidence intervals (95% CI) for prediction of ventricular inducibility at cutoff of 13.2 dmV and history of ventricular arrhythmias at a cutoff of 11.2 dmV for the QRS wave vector component.
Sensitivity Specificity AUROC (95% CI) Relative Risk
Ventricular inducibility
Ventricular arrhythmias
1.00 0.62 0.78 (0.65 to 0.90) 2.52 (1.48 to 4.29)
1.00 0.67 0.75 (0.60 to 0.90) 2.59 (1.48 to 4.71)
143
Table 3 Gadolinium enhancement versus no enhancement for all tested parameters.
Inducible (%) QRSd (ms) QTc (ms) Spatial QRS-T °(deg) QRSwave vc (dmV) Twave vc (dmV)
+Gadolinium RV (N = 13)
No Gadolinium (N = 2)
p-value
6 (46.2) 166.9 ± 30.0 491.5 ± 32.6 101.3 ± 39.1 13.3 ± 5.1 5.7 ± 2.1
1 (50.0) 142.0 ± 5.7 485.0 ± 17.0 123.6 ± 41.7 10.1 ± 5.9 5.9 ± 0.0
0.92 0.025 0.704 0.584 0.573 0.733
that TOF patients with increased QRSd should undergo electrophysiology studies to assess arrhythmogenicity. And since this has already proven to be predictive of ventricular tachycardia risk [2], one might confer that our small study suggests that the QRSwave vc should be assessed before EP study is performed regardless of QRSd given the inducible average was far less than 180 ms as suggested to be predictive of arrhythmogenicity [11]. Furthermore, since increased ventricular stretch and mass to volume ratio may increase arrhythmogenicity as suggested by the above author as well as by Menon et al. [12] and Velente et al. [13], respectively, one could rationalize that with this increased stretch and RVH mass, there would also be differences in depolarization subcomponent vector orientation. This could cause an overall sum magnitude to be smaller than that with less right ventricular stretch as the increased components in the thickened walls could disperse the magnitude of the overall vector. This fits our cohort as they are all undergoing PVR and thus have RV pressure and volume overload. Also, the association between ventricular arrhythmia inducibility and the root mean square of the QRSwave has been demonstrated in the past by el-Sherif et al. [14] as well as others as part of a signal averaged ECG analysis, thus it is not surprising that derived QRSwave vc is also predictive. Furthermore this study shows that the risk of ventricular tachycardia inducibility is not just based on RV volume N 180 ms or on just scar formation as neither showed a significant relationship to inducibility. Furthermore our results give many patients with QRSd b 180 ms for those with RV volume N 180 ml. Interestingly, hemodynamic measurements of right ventricular systolic or diastolic pressure were not consistent with inducibility or history of actual arrhythmias, and our tested parameters did not show any significant relationship to these parameters either. Arrhythmia inducibility is more complex than any one aspect MRI or catheter-derived it seems. Table 4 MRI measured RV volume b180 ml versus RV volume N 180 ml for all tested parameters.
Inducible (%) QRSd (ms) QTc (ms) Spatial QRS-T °(deg) QRSwave vc (dmV) Twave vc (dmV)
RV volume b 180 ml (N = 3)
RV volume N 180 ml (N = 14)
p-value
2 (66.7) 140.7 ± 4.6 496.7 ± 23.5 117.4 ± 31.4 9.4 ± 4.3 4.9 ± 1.7
5 (35.7) 168.1 ± 31.1 491.9 ± 32.8 93.5 ± 42.4 14.1 ± 5.0 5.2 ± 2.2
0.321 0.007 0.781 0.330 0.186 0.808
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Table 5 Hemodynamic data, right ventricular end diastolic pressure ≥ 10 mmHg versus those with RVEDp b 10 mmHg.
Inducible (%) QRSd (ms) QTc (ms) Spatial QRS-T (°) QRSwave vc (dmV) Twave vc (dmV)
RVEDp N 10 mmHg (N = 10)
RVEDp=/b10 (N = 13)
p-value
3 (30.0) 173.0 ± 22.1 501.4 ± 38.4 91.8 ± 31.5 11.6 ± 3.6 4.7 ± 1.6
5 (35.7) 162.3 ± 28.1 485.6 ± 21.1 102.8 ± 44.4 14.3 ± 5.4 5.8 ± 1.9
1.000 0.319 0.263 0.496 0.162 0.408
Of course limitations of this study include mainly the small size of the study. Also, since this was a retrospective study and signal averaged ECGs were not assessed, we were unable to include those values in our risk stratification as have been suggested to be associated with arrhythmogenicity [11].
Conclusions In this retrospective analysis of TOF patients undergoing EP studies, VCG evidence of depolarization differences was present between those TOF patients with and without inducible VA in the pre- and post-operative medicine, while the QRS duration as well as all other parameters tested did not. This suggests that VCG, especially the QRSwave vc, may have a role in risk stratification for arrhythmias in TOF patients but not necessarily in RV volume or in scar formation. Larger, prospective studies are needed to validate this method. Acknowledgements No acknowledgements other than the authors cited above. There are no financial disclosures or conflicts of interest. References [1] Khairy P, Aboulhosn J, Gurvitz M, et al. Arrhythmia burden in adults with surgically repaired tetralogy of Fallot. Circulation 2010;122:868–75.
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