PMC5420054_01
Twelve-lead ECGs. A: Sinus rhythm. B: Ventricular tachycardia. Inferior axis and left bundle branch block type morphology are observed.
gr1.jpg
PMC5420054_01_gr1.jpg
f0005
ECG during sinus rhythm showed no remarkable abnormalities (Figure 1A). ECG recorded during VT showed inferior axis and left bundle branch block type morphology, which suggested an RVOT origin (Figure 1B).
Fluoroscopic images of ablation sites and right coronary artery and intracardiac electrograms during ventricular tachycardia (VT). A: Placement of catheters during ablation at the posterior aspect of right ventricular outflow tract (RVOT). B: Placement of catheters during ablation at the right coronary cusp (RCC). Note the proximity of the RCC ablation site to the RVOT ablation site shown in panel A. C: Right coronary angiography before ablation at the RCC. The white star indicates the RCC ablation site from panel B, which was located anteriorly to the right coronary artery in right anterior oblique (RAO) view. D: Same images as panel C but with the ostium (white arrows) and the ostial portion (white lines) of the right coronary artery marked. Note that the ostium was located much higher than the distal tip of the ablation catheter (ABL) and the ostial portion ran inferiorly. E: Intracardiac electrogram recorded at the RVOT ablation site during VT. Local ventricular activation recorded at the distal (d) bipolar (Bi) electrode of the ABL showed an upright initial R wave preceding the onset of the QRS complex by 30 ms. Simultaneous recording of the unipolar (Uni) electrode of the ablation catheter displayed a QS pattern. F: Intracardiac electrogram recorded at the RCC ablation site during VT. Local ventricular activation showed not an initial positive but an early activation preceding the onset of the QRS complex by 27 ms (arrow) in the distal bipolar recording and exhibited a QS pattern in unipolar recording. See text for further discussion. EPI = epicardial mapping catheter inserted via subxiphoid puncture (catheter placed only for mapping, and catheter location not related with any endocardial ablation sites); HBE = His-bundle catheter; LAO = left anterior oblique; p = proximal; RVA = right ventricular apex catheter.
gr2.jpg
PMC5420054_01_gr2.jpg
f0010
RF energy was delivered repeatedly at the posterior RVOT (Figure 2A), where the earliest ventricular activation of bipolar electrogram preceding the onset of QRS by 30 ms and a QS pattern of unipolar electrogram were recorded during VT (Figure 2E). Subsequently, the RCC was mapped after identification of the right coronary artery (RCA) ostium and confirmation of the absence of organic stenosis by coronary angiography (CAG; Figure 2C). Although an initial positive and upright electrogram was not observed in the bipolar recording made at the RCC, an early activation and a QS pattern were recorded in the bipolar and unipolar recordings, respectively, during VT (Figure 2F). Figure 2C shows the relative positions of the RCC ablation site (white stars) and the RCA. In addition, the RCA ostium (Figure 2D, white arrows) was seen to be much higher than the ablation catheter tip. Based on these considerations, a decision was made to attempt ablation at this site (Figure 2B). During the second RF application at the site (Figures 2B and 2F), VT was terminated transiently but recurred after RF energy was turned off.
Right coronary artery stenosis. A: Twelve-lead ECGs just before (left) and after (right,asterisks) ST elevation in the inferior leads. B: Right coronary angiography (left anterior oblique view) showing acute stenosis just after ST-segment elevation was first observed (top) and after balloon angioplasty (bottom).White arrows indicate stenotic lesion. C: Intravascular ultrasound showing stenosis after repeated nitroglycerin injection (top) and after balloon angioplasty (bottom).White arrow indicates eccentric intimal thickening that successfully resolved after angioplasty. Neither coronary artery dissection nor thrombus was observed. See text for further discussion.
gr3.jpg
PMC5420054_01_gr3.jpg
f0015
ECG showed ST-segment elevation in the inferior leads (Figure 3A). Urgent CAG revealed acute severe stenosis at the ostial RCA, which was not resolved by repeated intracoronary nitroglycerin injection (Figure 3B, top). Intravascular ultrasound examination showed eccentric intimal thickening (Figure 3C, top, white arrow), which resolved after angioplasty (Figure 3C, bottom). Stenting was deferred at that time because subsequent percutaneous balloon angioplasty successfully improved the severity of stenosis (Figure 3B, bottom).