ECG and Anatomical Features in Patients of Left Coronary Cusp Ventricular Arrhythmias With R Wave in Lead I

Figures

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  FIGURE 1. CT assessment of the anatomical axis. The anatomical axis was defined as the angle between the horizontal line (white line) and the line connecting the inferior margin of the right coronary cusp and left ventricular apex (yellow line) in the frontal plane.

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  FIGURE 2. Samples of 12 lead QRS morphology of ventricular arrhythmias from patients with arrhythmias originating in the coronary cusps. Single QRS waves from 12 lead ECG from nine patients with left coronary cusp origin ventricular arrhythmias belonging to the R(I)‐wave group, one patient from the non‐R(I)‐wave group, and one patient from a right coronary cusp arrhythmia are displayed. The red box draws attention to QRS morphology in lead I.

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  FIGURE 3. Samples of 12‐lead ECG showing sinus beat—ventricular arrhythmia beat pairs. Paired sinus and arrhythmia beats are shown from three patients belonging to the left coronary cusp R(I)‐wave group and three patients belonging to the right coronary cusp arrhythmia group. The R(I)‐waves of both sinus and arrhythmia beats are positive in lead I for all six patients.

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  FIGURE 4. Details from a representative case from the R(I)‐wave group catheter ablation was performed for an 78‐year male (Case 1) with ventricular ectopy burden of 10%. (A) 12‐Lead ECG shows positive R wave in Lead I for both sinus and arrhythmia beat pair. (B) Intracardiac electrogram. At the successful ablation site, the ablation catheter recorded a potential (red arrow) that preceded the surface QRS complex by 30 ms, and a QS pattern was observed on the unipolar electrogram. (C) During pace mapping at the left coronary cusp (LCC), the QRS morphology matched that of the clinical ventricular premature complex. (D) Aortogram and the location of the left coronary artery (LCA). (E) Successful ablation site in right anterior oblique view. The blue dotted lines indicate the location of the LCC seen in the aortogram and demonstrate arrhythmia origin as the LCC.

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  FIGURE 5. Evaluation of the ECG axis in the LCC group. (A) Boxplots of QRS axis during sinus rhythm. The R(I)‐wave group demonstrated a more leftward QRS axis than the non‐R(I)‐wave group (p = 0.001). (B) ROC curve analysis showed a QRS axis < 26° during sinus rhythm, as discriminating R wave from non‐R(I)‐wave group best with area 0.849 (95% CI 0.725–0.973, sensitivity 81.2%, specificity 88.9%).

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  FIGURE 6. Analysis of anatomical axis measured by CT. (A) Anatomical axis obtained by CT correlated positively with sinus beat QRS electrical axis (r = 0.637, 95% CI 0.29–0.83, p = 0.0014). (B) Boxplots of anatomical axis. The R(I)‐wave group displayed a more horizontal cardiac axis on CT than the non‐R(I)‐wave group (14.4° ± 16.46° vs. 35.8° ± 11.71°, p = 0.004).

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  FIGURE 7. Putative mechanism of R wave presence in LCC ventricular arrhythmias. (A) Einthoven's triangle. (B and C) Frontal plane CT image of the heart of a patient from the non‐R(I)‐wave group (QRS axis of 65°). Anatomical axis was 37°. Electrical excitation originating in the LCC during VA tends to propagate more vertically (the green arrow represents the presumed excitation vector extending from the LCC to the left ventricular apex). (D–F) Frontal plane CT images of the heart of Case 1, a patient from the R(I)‐wave group (QRS axis of −51°). (D) Anatomical axis was 6°. Compared to the non‐R(I)‐wave group patient, the ventricles lay more horizontally, and (F) the electrical excitation of VA originating near the LCC propagated in a more horizontal direction (the orange arrow represents the presumed excitation vector extending from the LCC to the left ventricular apex). The horizontal component of ventricular activation is larger in the R(I)‐wave group than for non‐R(I)‐wave group patients, and makes emergence of an R wave in lead I more likely.