Case Report:
A 71-year-old woman presented with decompensated biventricular heart
failure in 2015, thought to be due to acute myocarditis. The CT chest
revealed a partial anomalous right upper pulmonary venous drainage,
right hypoplastic lung and cardiac dextroposition, findings consistent
with Scimitar syndrome. Her ECG revealed LBBB with a QRS duration of
196ms (Figure 1A). She was referred to our institution due to persistent
NYHA III-IV symptoms with a severely reduced LV ejection fraction (LVEF)
of 25%. Her vasoactive medical therapy was limited by hypotension.
Cardiac resynchronization therapy (CRT) was indicated.
In planning for this complex procedure, cardiac CT angiogram and
pulmonary venogram revealed right lung hypoplasia and mediastinal shift
to the right thoracic cavity leading to dextroposition of the heart
chambers. Her left ventricle was severely dilated. The right upper
pulmonary vein drained into the inferior vena cava (Figure 1C). The
coronary sinus had a high superior take-off but did not demonstrate a
left sided superior vena cava. Her previous right heart catheterisation
revealed moderately elevated pulmonary artery pressures but only minor
left to right shunting with a Qp:Qs of 1.24. The peak systolic and mean
pulmonary artery (PA) pressures were 62mmHg and 32mmHg, respectively.
The cardiac CT scan was used to register with the CARTOSEG™ modality of
the CARTO (CARTO® 3 Version 6) three-dimensional electroanatomical
mapping system. The ventricular septum was found to be rotated
anti-clockwise by 60 o due to dextroposition.
Fluoroscopic view of RAO 20-30o helped us in orienting
the interventricular septum perpendicularly (Figure 2A).
The patient was electively intubated. Using
NAVISTAR® DS Bi-Directional Catheter (4mm 7French
Curve D-F) and CARTO 3D Mapping system TM (Version 6),
images were created, aligned, and verified with the cardiac CT
geometries on the CARTOSEG™. Important landmarks like the right atrial
appendage, tricuspid annulus, the ostium of the coronary sinus and the
His-bundle were tagged (Figure 2B). All the obtained geometries were
integrated onto the fluoroscopic screen using the CARTOUNIVU™ modality
(Figure 3A-D). A quadripolar catheter was placed in the RV for back-up
pacing.
Left-sided delto-pectoral pocket was created. Three separate
venography-guided extra-thoracic axillary venous accesses were secured.
The axillary vein was then cannulated and a Medtronic® 62cm 6935M high
voltage lead advanced to the RV apical septum. CARTOUNIVU™ was used to
advance the RV lead to the desired location of the lower septum and the
position was confirmed in the RAO 30o and
antero-posterior (AP) views (Figure 3A). The cannulation of the coronary
sinus (CS) was then attempted. The ostium of the CS was angulated at
90o from usual anatomy, with a sharp superior and
anterior tortuosity before reaching the body of the CS (Figure 2B).
Neither the standard nor Amplatz curve Attain Command™ and the
90o and 135o Attain Select II™
catheters were successful in cannulating the CS. However, we were
successful in advancing a steerable decapolar diagnostic
electrophysiology catheter into the CS on which the long sheath was
telescoped. We identified 3 tributaries targeted for lead advancement.
Unfortunately, all the tributaries had angulation and tortuous take-off
precluding successful advancement of any hardware. After multiple
attempts with various tools, LV lead placement was abandoned, and
His-bundle pacing was attempted.
Placement of the His-bundle lead was guided by the tagged His-bundle
anatomy, which was integrated onto the fluoroscopic screen with the
CARTOUNIV™. Fluoroscopic angles of RAO 30o and AP were
helpful in guiding the Medtronic® C315 catheter to the perceived
His-bundle location (Figure 2C). Mapping using the Medtronic® 69cm 3830
pacing lead recorded His-bundle potential at the targeted region (Figure
2D). Passive pacing at the distal His region resulted in a threshold of
5V at 1ms with correction of LBBB (Figure 2E). This resulted in
non-selective capture of the His-bundle with complete correction of the
LBBB. The threshold for LBBB correction was 1.5V at 1ms and the capture
threshold was 0.75V at 0.4ms. Finally, the atrial lead was then placed
at the right atrial appendage guided again by CARTOUNIVU™. A Medtronic®
Amplia MRI Quad CRT-D device was secured in the pre-formed left pectoral
pocket. The fluoroscopic time was 117 minutes, and procedural time was
350 minutes. The His-CRT was programmed with a LV-RV delay of -80ms and
a programmed output of 3.5V at 1.0ms for the His bundle lead. The device
mode was set to DDDR 60bpm. The following changes in the 12-lead ECG
parameters suggested successful correction of the LBBB by capturing the
His-bundle: 1. Narrowing of QRS of 54ms (from 196ms to 142ms); 2. Change
in mean QRS axis (from +16o to
+42o), and; 3. Decrease in LV activation time
(measured in V5 from 90ms to 60ms) (Figure 1B).
The patient returned 6 months post His-CRT-D implantation for review.
The lead parameters were satisfactory. She was 99.7% paced. The LBBB
correction threshold of the His lead was 2.00V at 1ms. The patient had
an improvement in her functional status from NYHA Class III-IV to Class
II, associated with a 36% relative increase in LVEF (from 25% to
34%).