Coronary bifurcation stenosis – hemodynamically relevant?

Bunny Saberwal, MD; Sebastian Vandermolen, MD; Francesca Pugliese, MD, PhD, FHEA FESC FSCCT, Consultant / Reader Advanced Cardiovascular Imaging

William Harvey Research Institute Barts Heart Centre / Queen Mary University of London, London, UK

A 65-year-old female patient, suffering from atypical chest pain for the past year, came to the hospital for a check-up. Her medical history included hypercholesterolemia and borderline type 2 diabetes on dietary control. Coronary CT angiography (cCTA) was performed, followed by dynamic CT myocardial perfusion imaging (MPI) in rest and under stress using adenosine-mediated vasodilation.

Coronary CTA images showed a right coronary artery (RCA) dominant system, and a moderate stenosis in the proximal left anterior descending artery (LAD). A suspected significant stenosis involving mid LAD, distal LAD and the second diagonal branch (D2) at the bifurcation of the LAD/D2 (Medina classification 1,1,1) was visualized. No signs of stenosis were seen in the circumflex (Cx) and RCA. MPI did not show focal or territorial ischemia in the myocardium with a normal myocardial blood flow (MBF) of 127 mL/100mL/min in rest, and 248 mL/100mL/min under stress.

Subsequently, the patient underwent invasive coronary angiography (ICA), which confirmed the CT findings, and measured a normal LAD fractional flow reserve (FFR) of 0.85. No interventional therapy was performed.
An axial MIP image and a cinematic VRT image show a moderate stenosis in the proximal LAD and a significant stenosis at the LAD/D2 bifurcation.
Courtesy of William Harvey Research Institute Barts Heart Centre and Queen Mary University of London, London, UK

Fig. 1: An axial MIP image (Fig. 1a) and a cinematic VRT image (Fig. 1b) show a moderate stenosis in the proximal LAD (arrows) and a significant stenosis at the LAD/D2 bifurcation (dotted arrows). 

MBF images in both short and long axis reveal no evidence of myocardial perfusion defects in rest and under stress. The absolute global MBF value was measured 127 mL/100mL/min in rest, and 248 mL/100mL/min under stress.
Courtesy of William Harvey Research Institute Barts Heart Centre and Queen Mary University of London, London, UK

Fig. 2: MBF images in both short (Figs. 2a and 2c) and long (Figs. 2b and 2d) axis reveal no evidence of myocardial perfusion defects in rest (Figs. 2c and 2d) and under stress (Figs. 2a and 2b). The absolute global MBF value was measured 127 mL/100mL/min in rest, and 248 mL/100mL/min under stress.

Angiographic images confirm the moderate stenosis at proximal LAD, and significant stenosis at the LAD/D2 bifurcation.
Courtesy of William Harvey Research Institute Barts Heart Centre and Queen Mary University of London, London, UK

Fig. 3: Angiographic images confirm the moderate stenosis at proximal LAD (Fig. 3a, arrow), and significant stenosis at the LAD/D2 bifurcation (Fig. 3b, arrow).

Coronary bifurcation lesions account for up to 20% of all PCI, and the treatment with stenting remains challenging due to numerous possible techniques and high risk of complications.[1] In order to make an appropriate treatment decision, i.e. stenting or no stenting, it is important not only to acquire diagnostic information about a coronary bifurcation stenosis, but also to assess its hemodynamic relevance. This can be evaluated comprehensively and noninvasively with a single modality by combining coronary CTA with dynamic CT MPI. In this case, a coronary artery disease involving a coronary bifurcation is visualized. However, both MPI in rest and under stress show no focal or territorial perfusion defects. The global MBF value under stress is almost twice of the one in rest, which confirms expected increase in flow denoting flow reserve. This agrees with the measured FFR value of 0.85 in PCI. Therefore, no interventional therapy was performed to this patient. It is also noteworthy that a systolic ECG-triggered Sequential Shuttle mode is used with an absolute delay of 250 ms, which is insensitive to extra-systolic events and improves myocardial perfusion evaluation since the myocardium is thicker in systole. It also is very robust for high and varying heart rates – this patient’s heart rate varied from 63 to 120 bpm over both examinations. CARE Dose4D (Real time anatomic exposure control) and 70 kV are applied to minimize radiation exposure.

Scanner

Scan area

Heart

Heart

Scan mode

Prospective ECG triggered CTA

Dynamic perfusion (Rest/Stress)

Scan length

91 mm

105 mm

Scan direction

Cranio-caudal

Shuttle

Scan time

2.4 s

32 s

Tube voltage

70/70 kV

70/70 kV

Effective mAs

462 mAs

218 mAs

Dose modulation

CARE Dose4D

CARE Dose4D

CTDIvol

11.8 mGy

26.3/ 28.9 mGy

DLP

108.3 mGy cm

277.4/ 305.1 mGy cm

Rotation time

0.25 s

0.25 s

Slice collimation

152 x 0.6 mm

192 x 0.6 mm

Slice width

0.75 mm

3.0 mm

Reconstruction increment

0.5 mm

2.0 mm

Reconstruction kernel

Bv40 (ADMIRE 2)

Qr36

Heart rate

73 bpm

63–117 / 83–120 bpm

Contrast

300 mg/mL

300 mg/mL

Volume

60 mL

60 mL

Flow rate

7.5 mL/s

7.5 mL/s

Start delay

Test bolus using 15mL + 40mL saline

Test bolus using 15mL + 40mL saline