While many hundreds of studies have been published utilising coronary artery optical coherence tomography (OCT), very few have focused on the application of OCT in daily clinical practice. The following case studies are intended to help guide physicians on specific clinical situations in which OCT can help optimise physician treatment strategies.
The cardiac cath lab at Mount Sinai Hospital, New York, New York, is a leader in sharing best practices for improving outcomes in complex coronary cases. Mount Sinai has established guidelines to help drive best practices among interventional cardiologists and fellows in the cath lab. OCT has been adopted as an optimal intravascular imaging modality for specific clinical situations in percutaneous coronary intervention (PCI).
The following cases are illustrative, real-life examples of when and how to best implement OCT in the cath lab. These cases highlight the strengths and pitfalls of OCT use in daily clinical practice. While all cases presented were imaged at the Mount Sinai Hospital Catheterization Laboratory, minor changes have been made to clinical details for educational purposes. Images have not been enhanced or manipulated in any way.
Optical Coherence Tomography Imaging Protocol
The St. Jude Medical OCT system and the Dragonfly™ intravascular imaging catheter are used to perform OCT intravascular imaging after intracoronary injection of 200 μg of nitroglycerin through conventional 6 F guiding catheters. A 0.014 in guidewire is positioned distal to the region of interest; the guidewire is then back-loaded through the blue tip and out of the exit port on the Dragonfly catheter.
The Dragonfly catheter is advanced until the proximal radiopaque marker is distal to the target lesion. A test injection of 1–2 cc of 100 % contrast is used to ensure guide catheter positioning.
Once the pullback is enabled on the system, the coronary blood flow is replaced by continuous flushing of 100 % contrast media using a power injector or manual injection. The system labelling suggests power injector settings of 14 cc of total volume at 4 cc/sec rate at 350 psi and 0 rise. We recommend these settings for the left anterior descending (LAD) and left circumflex (LCX) arteries, and 12 cc of total volume at 4 cc/sec rate at 350 psi and 0 rise for the right coronary artery (RCA). We find these settings to provide consistent, high-quality images. Measurements are performed using the system after proper calibration settings of the Z-offset.
Scenario I – In-stent Restenosis
In-stent restenosis (ISR) is a major clinical problem faced in the cath lab. OCT has the capacity to differentiate ISR from other pathologies and can easily distinguish stent struts. OCT may also provide information about the pathology of the restenotic process by identifying features such as calcification or lipid content, which suggests neoatherosclerosis within the stent. In the following two cases, we highlight how the use of OCT can help to guide clinical decision-making when dealing with ISR.
History: Hypertension, hyperlipidaemia and previous smoking.
- Previous PCI to mid-LAD in 2009 and in 2010 at an outside hospital. The details of these previous PCIs were unknown and it was unclear how many stents had previously been placed.
- The patient presented to Mount Sinai with Canadian Cardiovascular Society (CCS) Class III angina. Exercise myocardial perfusion imaging revealed a small reversible apical perfusion defect.
- Cardiac catheterisation suggested a stenosis in the mid-LAD region (see Figure 1A).
- As seen in Figure 1B, OCT of the stenotic LAD lesion identified two stent layers; both layers appeared to be well-apposed.
- Based on these OCT findings of well-apposed, double-layered stents, clinical decision-making was simplified, with reasonable options including percutaneous transluminal coronary angioplasty (PTCA), bypass surgery or PTCA with potential brachytherapy.
- Following patient consultation with a cardiothoracic surgeon and interventional cardiologist, a cutting balloon PTCA was performed at 10 atmospheres followed by brachytherapy.
Notably, the high resolution of OCT was able to easily define the two layers of stent and prevented us from placing a third layer of stent in this patient.