Intermediate stenosis

Coronary slow flow by intermediate stenosis with negative remodeling

Case: 60’s, male.

Course: Previously the patient received BMS (3.0-18mm) implantation at LAD#7 for ST elevation MI (2 years ago), and one year later TLR was performed by drug coating balloon (3.0-15mm) for ISR lesion. This time follow up CAG was performed.

ECG showed mild ST-T abnormalities in V5-6, and exercise SPECT showed no obvious finding of stress induced ischemia (figure 1).

Echocardiography didn’t show a wall motion abnormality. CAG revealed no significant in-stent restenosis. However, 90% stenosis was detected distal to the stent, and coronary flow in LAD was extremely sluggish (figure 2, 3).

We measured FFR in LAD because non-invasive stress test didn’t show a reversible ischemic change. FFR was 0.78 and focal step up was detected at the stenosis site (figure 4).

IVUS demonstrated negative remodeling at the stenosis site, and amount of plaque was small (figure 5).

Minimal lumen area was 2.4mm². The lesion was not dilated by intracoronary injection of ISDN and Nicorandil, therefore, an involvement of coronary spasm was denied. We decided to perform PCI based on the finding of coronary slow flow and FFR result.

We dilated the lesion step by step from low pressure by POBA(2.5/15mm) to avoid perforation. And then, DCB(2.5/20mm) dilation was followed. During balloon dilatation, we observed coronary wedge pressure (figure 6).

Coronary wedge pressure was 9mmHg (Pw/Pa 0.11; within normal range), therefore an involvement of disturbance of micro-vascular circulation (i.e. distal embolization) was denied. After POBA, coronary flow was improved and FFR was increased to 0.87 (figure 7). 

Possible cause of coronary slow flow were;

1) severe stenosis,

2) distal embolization,

3) microvascular dysfunction (including microvascular spasm).

About this case, the participation of severe stenosis and distal embolization were denied, and then microvascular dysfunction was thought as a cause. And the dysfunction was reversible, which indicated the possibility of microvascular spasm.

As for the future, a measurement of microvascular resistance will be desirable for the elucidation of pathology of this kind of patient.