- Procedural step:
To determine the severity of dynamic obstruction of RCA, we carried out
the coronary pressure wire study (Figure
5). Aortic pressure was obtained by using a 6-F guiding catheter without
side holes, connected to a pressure transducer (Becton, Dickinson, Singapore)
and Horizon computerized polygraph (GE, USA). After calibration, a 0.014-inch
micro-manometer tipped guide wire (PressureWire, Radi-Medical Systems,
Uppsala, Sweden) was connected to its interface and advanced under fluoroscopy,
distal to the RCA ostial lesion. Selected pressure tracings and angiographic
runs were recorded during this procedure. Diastole was identified as the
interval between the dichrotic notch in the aortic pressure tracing and
the following R-wave peak in the ECG. Mean and diastolic components of
aortic pressure (Pa), distal intracoronary pressure (Pd), and pressure
gradient (P)
were calculated. To obtain baseline pressure parameters, intracoronary
administration of 200 µg of nitroglycerin was given for 5 minutes
and an intracoronary adenosine bolus (40 µg) was given to induce
hyperemia. To obtain dynamic pressure measurements, dobutamine was administered
through an intravenous infusion starting at 5 µg/kg per minute;
it was increased by 5 µg/kg per minute to a maximum of 30 µg/kg
per minute. After dobutamine challenge, the RAP stress test was done to
reach the target heart rate (as target heart rate in treadmill test).
Pacing rate started at 90 bpm and increased by 20 bpm every three minutes
until a final pacing rate of 140 bpm was reached. Pressure parameters
were measured continuously until the patient developed symptoms. Maximal
diastolic P
increased from 6 mmHg at baseline to 13 mmHg, and when the pressure gradient
reached to 13 mmHg, T wave inversion was observed, the chest pain was
developed. (Figure
6, Figure
7) This result showed that dobutamine challenge with rapid arterial
pacing may result in the dynamic obstruction in anomalous RCA, which may
cause ischemia. As this result, to relieve the dynamic compression of
RCA, we carried out intracoroanary stenting (Taxus 4 x16mm) of RCA ostium
(Figure
8). After stenting, lesion lumen area increased from 6.0 mm2 to 12.7
mm2, and despite continuing the dobutamine challenge with rapid atrial
pacing, diastolic P
decreased to 2 mmHg, chest pain was relieved, and T wave inversion was
disappeared. (Figure
9) He was asymptomatic at 2 months' follow-up.
|
Leave a comment